IFCEE 2024: Earth Retaining Systems, Ground Improvement, and Seepage Control

This research study involves two numerical models representing the realistic field conditions of GRS bridge abutments to investigate the static and dynamic response of these structures. The accuracy of the simulation was assessed first against the results of instrumented and monitored GRS systems in static condition and then was evaluated in dynamic analysis under harmonic base acceleration up to 0.4 g. To capture the wall behavior accurately during construction, the numerical simulation was developed within several steps, including placement of the facing blocks following by the backfill soil layer-by-layer, representing the bottom-up construction stages. The numerical analysis was found to give reasonably accurate prediction of the experimental results at both the end of construction and after the dynamic load was applied.

Damage caused by earthquakes to earth retaining structures can result in a high number of casualties. One way to improve the seismic response of these structures is to use lightweight backfill materials such as tire derived aggregates (TDA) as separate layers or mixtures with sand. The present research studies the static and dynamic response of cantilever retaining walls with inclined backfill filled with soil-rubber mixtures (SRM). The finite element software GeoStudio QUAKE/W in conjunction with SLOPE/W is used. A comparison with a similar retaining structure with conventional backfill shows that the displacements of the wall with SRM backfill increased, but less shear forces were developed behind the wall, and higher factors of safety against slope stability were obtained. The Newmark method is also used to determine the permanent deformations that may occur as a result of the inertial forces associated with the seismic loading.

This paper describes a field-testing program consisting of 14 lightweight deflectometer (LWD) tests performed on compacted foamed glass aggregate (FGA) fill. The details of the LWD testing procedures and data interpretation are provided. A portion of the tests included either a 1.9 kPa (40 psf) or 7.2 kPa (150 psf) surface pressure to simulate the confinement provided by soil or crushed stone typically placed between the FGA and the pavement or floor slab. The results of the LWD tests are compared to static plate load (SPL) tests performed at the same locations under the same conditions. The dynamic modulus values, E_dyn, interpreted from the LWD tests are compared to the second loading strain modulus values, E₂, and second loading modulus of subgrade reaction, k_u2, interpreted from the SPL tests. The results from this study show that E_dyn generally increases with the magnitude of surface pressure. The results also show weak correlation between E_dyn and E₂ and some positive correlation between E_dyn and k_u2.

In engineering construction projects, foundation systems often require resistance to vertical uplift and horizontal pullout loads, with tension members like percussion-driven earth anchors (PDEAs) being a preferred choice. This study focuses on a laboratory pullout experiment involving a PDEA (Duckbill model 88 with a 7.9 mm wired tendon cable) in poorly graded sand (SP). The soil box dimensions are 1,000 (L) × 900 (H) × 300 (W) mm, and the anchor was pushed to a depth of 750 mm using a hydraulic jack. The pullout force and anchor displacement were measured using a linear variable differential transformer (LVDT) and a load cell. A numerical model in ABAQUS, employing the combined Eulerian-Lagrangian (CEL) approach, was used and validated against the experimental test. The numerical analysis showed that increasing anchor embedment depth by 13% led to a 78% higher pullout load in the numerical analysis.

In the late 1970s, Steve Webster at the US Army Corps of Engineers Waterways Experiment Station (WES) started experimenting with a three-dimensional cellular system to confine aggregate and soil to assist heavy military vehicles in traversing over soft soils. Soon after, commercial geocells were created for the purpose of load support and erosion control on slopes. The basic design of geocells is texturized strips of polyethylene (PE), which are ultrasonically welded together, and usually perforated to allow water to flow through the PE strips, reducing hydrostatic pressure. Over the past approximately 40 years, this design and manufacturing process has not changed. There are several major challenges associated with using traditional geocells for protecting slopes from erosion: spillage of aggregate from the cells when used on slopes with an angle greater than 35°, and washout of the aggregate from the cells under the influence of heavy precipitation and flowing water. This paper provides an overview of the technology of using weld-free geocells (WFG) for slope reinforcement to deal with these potential problems.

Freeze-thaw cycles are closely related to the slope instability in the seasonally frozen areas. During winter, soil moisture content decreases forming ice segregates, which increase the stability of the slope. The slopes are the strongest in the winter when ice forms. However, when the ice melting starts in the spring season, formation of stagnant water lubrication between the melting soil and freezing soil interface constitutes the weak interface of landslide hazard. As temperature starts increasing, the ice melts and the soil moisture content increases dramatically. The excessive moisture content generates porewater pressure and reduces soil strength, which contributes to slope failure. In this study, a numerical model using GeoStudio has been developed to simulate freeze and thaw condition in a shallow slope. TEMP/W and SEEP/W modules are used to perform coupled conductive thermal analysis, which generates both heat and water mass transfer inside a slope. Later using the generated pore water condition, slope stability analysis is conducted using SLOPE/W. After that, a transient seepage model was developed incorporating rainfall intrusion in the slope with the thawing process for the same duration. The model showed that slope stability increases with the decreasing pore water pressure during cold weather. The slope stability decreases from 1.7 to 1.2 during the thawing. This phenomenon is due to the absorption of heat followed by rapid rising in soil temperature. This research will be helpful for the decision makers as a guide for highway slope construction and act as an early warning tool in the snow melting period.

The earthen embankment is extensively employed in transportation networks and flood defenses. The collapse of embankments might cause social and economic disruptions. Expansive soils are a prevalent problem that affects many locations in the United States’ southern, western, southwestern, and north-central states. Sulfate-rich expansive soils form ettringite by the reaction of soluble sulfate and free alumina with calcium-based stabilizers. Expansive clayey soil frequently exhibits shrinkage-swelling behavior as a result of variations in moisture regimes with wetting-drying cycles. The structural integrity of slopes is seriously threatened by desiccation cracking in expanding clays during seasonal fluctuations. In the past, soil treatment with a biopolymer additive has been effective in lowering soil cracking brought on by desiccation. This study presents a probabilistic framework to assess the stability of expansive soil slopes considering the impact of flood levels and drought conditions on the earthen embankments. The procedure for the development of the fragility curve is discussed in the study. The impact of biopolymer treatment on slope stability is investigated with a combined framework of slope stability analysis using a coupled finite element (FE) and limit equilibrium (LE) based software and risk-based analysis using fragility function.

Ground anchors are commonly used in construction to ensure safe support of various structures. Load distributive compression anchors (LDCAs) have recently been introduced as an improvement over conventional ground anchors and have been extensively used in the field. Understanding the load transfer mechanism of LDCA accurately is crucial to ensure structural stability. In this study, scaled-down model experiments with multiple anchor bodies were performed to analyze the load transfer mechanism of LDCAs. Experimental results showed that the bearing capacity of LDCAs decreases due to the interference effect between the anchor bodies. To investigate the interference effect, the load–displacement relationship of the anchor body and grout–soil shear stress distribution was evaluated.

Photogrammetry for measuring soil surface movement has gained popularity in recent years. This technique involves placing coded targets and ground points on the soil surface and capturing images before and after the movement, enabling precise measurements. This study explores the effectiveness of using a consumer-grade camera for geotechnical soil surface heave measurement compared to conventional methods, such as dial gauges, during laboratory pullout tests. The laboratory pullout tests were conducted by pulling out an anchor driven into a soil box consisting of sandy lean clay. The dimensions of the soil are 1 m × 1 m × 1 m (3.28 ft × 3.28 ft × 3.28 ft). Digital dial gauges were positioned on the soil surface to measure surface heave during pullout tests. The consumer-grade camera was used to capture soil surface images before and after each pullout test. The captured images were then processed using the photogrammetric software Agisoft Metashape Professional to obtain soil surface displacement due to the anchor pullout. The acquired displacement of the soil surface from photogrammetry was compared with readings obtained from dial gauges. Results demonstrate the successful application of photogrammetry in obtaining accurate measurements of heave. In addition, heave patterns related to different anchor embedments were analyzed based on photogrammetric images. This study aids in predicting potential soil heave occurrences, expanding the potential applications of photogrammetry in geotechnical engineering.

Embedded foundation elements such as diaphragm walls, drilled shaft walls, and heavy gauge sheet pile walls are often used to stabilize soil slopes and to create retaining walls for grade separation. These walls are typically analyzed for global stability using limit equilibrium analysis methods where the slip surfaces pass through the wall below grade. This type of analysis assumes that the slip surface is continuous and shears through the wall. However, the failure mode for these heavy foundation elements is not shearing through the wall but instead is a deformation failure as the foundation elements are pushed into the soil mass downslope in a passive failure mode. The author presents a modified limit equilibrium analysis approach where the slip surface is uncoupled at the wall instead of being modeled as a continuous slip surface through the wall. This method includes a search for the critical slip surface beginning upslope and terminating along the vertical wall below grade. The slip surface downslope of the wall is replaced with a line load acting upslope. The line load represents the resultant of an allowable passive pressure, less than the full passive pressure to limit deformation to an acceptable magnitude. A comparative example of an embedded wall for grade separation is presented. The uncoupled analysis is more realistic and often results in a lower calculated global factor of safety than a limit equilibrium analysis assuming a continuous slip surface through the wall.

This study details the finite element modelling of two double-barrel, low-profile arch corrugated metal culverts with shallow cover. Instrumentation and load-testing was conducted in a previous study to measure the responses in terms of vertical deflection and inner fiber strain using a 381.3-kN (85.7-kips) load truck configured to the ALDOT LC-5 load specification, and the measured responses were used to validate the results of the numerical models in this study. The structural support from shallow buried culverts comes not only from the culvert itself but from the backfill soil as well, which makes it difficult to simply calculate the loads transferred and the response of the culvert structures. The objective of this study was to use numerical models to predict the structural behavior of the culverts due to external loading. 3D finite element models were created in Plaxis-3D and Abaqus, while 2D plane strain analysis was conducted in CANDE to simulate the load tests. Comparison of the field measured values to the numerical simulation results for the same load and measurement positions showed reasonable agreement in terms of trending and magnitude; however, the deflections predicted by the numerical analyses have been consistently higher than the measured values. The stresses estimated from the measured strain based on plane stress conditions also showed reasonable agreement with the calculated stresses from the FE analyses. Additionally, the validated modelling approach was then used to analyze a pipe culvert that could not be tested during the field-testing program, and the results were compared to those of the low-profile arch. The trends in the responses were similar; however, the vertical displacement from the pipe was relatively higher than that of the low-profile arch.

This study aims to investigate the effect of various types of biopolymers, including xanthan gum (XG), guar gum (GG), and agar gum (AG), on the shear strength of granular media. The environmental impacts of using traditional materials, such as cement and lime, for soil improvement have led geotechnical engineers to consider using eco-friendly alternatives. Biopolymers, due to their low cost and abundance, have become an attractive alternative for soil improvement. In this study, biopolymers were introduced at a dry mass ratio of 1%. Consolidated undrained (ICU) triaxial tests were performed to examine the soil shear strength, while an Anton Paar MCR 302e rheometer was used to evaluate the rheological properties of the biopolymer gels. The results showed that increasing biopolymer yield stress resulted in an increase in the effective cohesion (c′) of the treated material, while soils treated with all biopolymers resulted in a decrease in the soil’s effective friction angle (ϕ′). Furthermore, the study established a correlation between the yield stress, viscosity at a strain of 1 s⁻¹ of the biopolymer, and the enhanced soil shear strength for different biopolymer types.

This paper reviews the latest techniques applied to the jet grouting practice in order to define the correct 3D position of the column and its diameter at the project depth. These aims have been already pursued by several companies in different ways. However, the increasing depth of application keeps on moving the goalposts. When contractors ask specialized companies for an effective jet grouting grid, it is imperative to know the position of the hole within the tolerance required to obtain the design columns’ overlapping. To do that, new tools have been improved with higher accuracy and real time data delivery. Wired drilling rods and mag./incl. tools allow the driller to receive a continuous flow of data to the surface, thus avoiding loss of time and long stops at the bottom of the hole where risk of getting stuck is high. They further eliminate opening the drill string, which may allow ingress of particles into the air line. In a different way, the slim gyro tools may be inserted through the swivel (again, without opening the string) and quickly lowered into the grout line until reaching the bottom of the string. In both cases, data is transmitted in real time making possible trajectory corrections or making quick decisions in case of excessive deviation. In addition, for the formation required to be treated, it is not always possible to carry on a shallow trial test field (where the columns may be excavated and directly observed), where the nature of such deep formations differs from the formations located at a shallower depth. The existing methods to detect the column diameter at the project depth are often very expensive, not real time, and they also lose accuracy with depth. For such a reason, a mechanical system has been coupled with advanced electronics to reach the border of the column while simultaneously surveying the path of the pipe used to “travel” inside the grouted soil.

Instrumentation efforts aimed at monitoring the stiffness and displacement characteristics of inclusions under surcharge load involve measurements of settlement and load to understand both the movement response and the portion of the surcharge load that is held by the inclusions. This paper compares two projects, one with stone columns and stiff surface soils (N > 15) to a 20-ft depth, and the other with 4.5-in. diameter helical piles and soft surface soils (N < 4). In both projects, the same types of vibrating wire (VW) earth pressure cells and VW settlement systems were used in similar arrangements, each installed in pairs with one on top of and one in between the inclusions. Both projects also had approximately the same level of loading (12 and 15 ft of fill at Site 1 and Site 2, respectively). The earth pressure cells on top of the helical piles showed they held nearly all of the surcharge loads at top of the stone column. Conversely, for the project with stiff clay surface soils and stone columns, most of the surcharge load was held by the clay at the ground surface. There was almost zero relative settlement between the stone columns and the stiff clay surfaces, and the clay held the full surcharge load (1,300 psf) without deflecting much at all, while the stone columns mobilized only 800 psf of vertical earth pressure at the top of the stone column. On the other hand, for the helical pile project with soft surface soils, the helical piles experienced less settlement (0.75 in.) compared to the adjoining soft soils (2.5 in.), indicating a stiffer load bearing response of the helical piles near the ground surface. Significant load concentration (approximately 11,000 psf) was measured by the earth pressure cells on top of the helical piles along with a commensurate amount of load relief on the surrounding soft soil (approximately 150 psf). In consideration of the above, it is the author’s opinion that the planning of instrumentation programs using earth pressure cells to verify inclusion performance needs to consider the relative stiffness between the surface soils and the top of the inclusion elements before deploying earth pressure cells. With stiff surface soils and stone columns, it is unlikely to measure load concentration at the surface, whereas with helical piles and soft surface soils it is highly likely. In scenarios with stiff surface soils and stone columns, it may be practical to limit instrumentation efforts to measurements of settlement.

The compressibility characteristics of soils are of great importance in geotechnical engineering, as they play a vital role in determining the magnitude of deformation that the soil will impose on superstructures. This matter becomes more important in expansive soils due to their unusual volume-change behavior. Many studies have explored the role of different stabilizers on the compressibility of expansive soils in addition to their swelling potential. However, the effect of loading history of the soil has been neglected in their measurements. This study assessed the role of loading history on compressibility characteristics of lime-stabilized expansive soils. A series of one-dimensional swelling-consolidation tests were conducted on samples containing different lime percentages (3%, 6%, and 12% of dry soil weight). In order to observe the effect of loading history, different overconsolidation ratios (OCR) were induced in the stabilized specimens. The rebound and compression indices of samples with different OCRs and lime contents were measured and compared to each other. Results of this study show that increasing the OCR value lowers the effectiveness of lime in reducing the rebound index, while it improves the reduction of the compression index.

The wet method of deep mixing involves mixing a binder-water slurry with soft in situ soil to increase the strength of the soil. Curing temperature is one of the most important factors that affect the strength of cement-treated soil. However, the ground temperature is not always consistent; it depends on the weather, season, region, and other environmental conditions. Additionally, the temperatures of cement-treated soil columns and adjacent in situ soil increase due to the heat generated from the cement hydration reaction in the elements and then decrease as the heat dissipates. This paper presents unconfined compressive strength (UCS) test results of cement-treated soil samples that the curing temperature was increased or decreased during the curing process. A fabricated lean clay (CL) was blended with a cement-water slurry. The prepared samples were cured in temperature-controlled water baths at 25°C and 45°C for up to 28 days. The portions of time at 25°C and 45°C and the order of curing at 25°C and 45°C varied. After the curing, UCS tests were performed to measure the strength of the samples. The test results show that a sample cured for a longer time at a higher temperature has a high UCS regardless of the order of curing temperatures. However, the effect of high curing temperature on the strength is more significant at a later curing time. In other words, with the same portions of curing time at 25°C and 45°C for two samples, a sample initially cured at the low temperature and then cured at the high temperature is stronger than the sample cured at the high temperature first. A strength development plot in the relationship between curing time and UCS has two logarithmic curves before and after the temperature change with different shapes.

The use of biopolymers has received research attention for the stabilization and erosion control of course-grained soils. However, there are questions remaining on the long-term stability of biopolymer-treated soils under drying and wetting cycles. This work focuses on the performance of xanthan gum (XG) for improving mechanical properties of sands. Biopolymer-treated samples were subjected to cyclic drying/wetting according to the ASTM D559/D559M-15 code designed for soil-cement mixtures. The samples were dissected after each cycle to study the mechanism and progression of the failure. The biopolymer was extracted and studied using rheological and infrared spectroscopy (FTIR). The outer crust of the specimen seems to prevent intrusion of water inside the sample due to its low hydraulic conductivity. Rheological investigations indicate a reduction in the yield stress of the biopolymer gel in this crust compared to the rest of the specimen. FTIR showed the appearance of adsorbed CO₂, which could indicate biological degradation.

Cement grouts are used for installing pipes and wells, repairing infrastructure, treating and stabilizing soils and rocks, and also treating contaminated soils. Drilling muds are used in installing various deep foundations, pipes, tunnels, drilling boreholes, and in horizontal direction drillings even along the coastal regions. In this study, cement grouts with water-to-cement ratios of 1.0 and 1.5 were tested with and without 3.5% salt water. Also, drilling muds with bentonite clay content of 4% and 6% were tested. Also, the tests were performed at 25°C and 75°C. Based on the electrical impedance-frequency response, electrical resistivity was identified as the critical material property to monitor using the Vipulanandan impedance model for the cement grouts and the bentonite clay drilling muds. Immediately after mixing the resistivity of cement grouts with water-to-cement ratio of 1.0 and 1.5 were 1.42 and 1.60 Ωm, respectively, and the salt water and temperature reduced the initial resistivity. The initial resistivity of the drilling muds with 4% and 6% bentonite were 5.5 and 4.5 Ωm, respectively. Rheological tests showed that both fluids were non-Newtonian fluids and were shear thinning. The cement grouts’ yield stresses were higher than the yield stresses of the drilling muds. Salt water and higher temperature modified the rheological properties of the cement grouts and drilling muds. Vipulanandan rheological model was used to model the behaviors, and the maximum shear stress tolerance (new parameter) for the cement grouts were higher than the drilling muds. Also, the maximum shear stress tolerance of the drilling mud is an indicator of borehole cleaning (removing mud filtercakes) and also the potential for formation erosion. Vipulanandan rheological model predicted the cement grouts and drilling muds rheological behaviors very well based on the root mean square error (RMSE) and coefficient of variation statistical parameters.

Construction of roadway embankment with gypseous soil exhibits hazard for the long-term performance. The gypseous soil is known to exhibit suitable strength after compaction; however, it loses the strength when subjected to environmental issues such as rain and the variation in the water table level. In the present investigation, an attempt has been made to implement gypseous soil with 84.2% of gypsum content, which was obtained from Tikret region (180 km north of Baghdad), in the preparation of an embankment model in the laboratory. The gypseous soil was compacted to 95% of its maximum pre-determined dry unit weight of (16.4 kN/m³) in six layers in a metal box with the dimensions of (50 × 50 × 30) cm, and each layer is of 5 cm thickness to form a control embankment model, and subjected to vertical stress. Test was carried out using proving ring of 5 kN capacity. The vertical and lateral deformations of the embankment model were monitored until failure. The second embankment model was constructed using an aluminum reinforcing strips spread at five layers of the embankment height. The aluminum reinforcing strips were laid at equal spaces between each of them, which means that each layer was reinforced with four strips at a spacing of 10 cm center to center. The vertical and lateral deformations were also monitored until failure. In the third embankment model, the gypseous soil was stabilized with M-30 cutback asphalt, and then the embankment model was constructed using an aluminum reinforcing strips as in the second model. The fourth embankment model was constructed using the aluminum strips and a stabilized gypseous soil with cationic emulsion. It was observed that the reinforced and the emulsion stabilized embankment models exhibits lower vertical deformation of 40% and 30% as compared with the control embankment. On the other hand, the lateral deformation at the third embankment layer declines by 50%, 39.2%, and 35.7% when the emulsion, cutback, and earth reinforcements were implemented, respectively, as compared with the control model. However, the lateral deformation at the fifth layer declines by 68.4%, 55.5%, and 68.4% when the emulsion, cutback, and earth reinforcements were implemented, respectively, as compared with the control model. It was concluded that implementation of cutback and emulsion stabilization in addition to the earth reinforcement can better sustain vertical stresses applied on the embankment surface and present a sustainable solution for the roadway infrastructure.

In this study, highly sensing smart cement grouts with and without sodium silicate additive were developed and tested, and also the curing and piezoresistive behavior were modeled. Sensing cement grout was prepared using water-to-cement ratio of 0.8. Commercially available table top mixer was used at a speed of 1,000 rpm for 5 min and 0.075% carbon fibers (based on the cement weight) were added during the mixing process. Curing process of the cementitious materials was monitored with changes in electrical properties, which can also be easily monitored in the field. Electrical resistivity (sensing property) of the grouts was measured using a digital resistivity meter. Also, the electrical resistance changes with the curing time were measured using the LCR [inductance (L), capacitance (C), resistance (R)] meter with the two-probe method. The test specimens were capped and then tested at a controlled displacement rate to fail the specimen in about 30 min. Tests were performed up to 28 days of curing. The one day compressive strength of the smart cement grout was 3 MPa, and it increased to over 16 MPa after 28 days of curing. Addition of up to 3% sodium silicate reduced the compressive strength of the grout. Change in sensing parameter, the resistivity of the smart cement grout material under stress was investigated. During the compression test, electrical resistance was measured along the stress axis. Also, the change in sensing property was related to the applied stress to develop the piezoresistive relationship. The piezoresistive strain after one day curing was 155%, and it increased to 179% after 28 days of curing. The failure strain of cement grout is about 0.2%, so the smart cement grout was over 775 times (77,500%) more sensitive than the regular grout. Vipulanandan curing model, correlation model, and piezoresistive p-q model were used to characterize the smart grout behaviors.

The objective of this paper is to examine the relationship between biopolymer concentration and the erodibility of coarse-grained soil. The erosion of soil by water (referred to as scour) is an important issue that affects many engineering structures such as earthen dams, levees, bridges, and embankments. Scour is one of leading causes of bridge failure; the cost of repairs due to scour has reported by the United States Department of Transportation to be very high. This gives rise to the need for an environmentally friendly solution to improving soil supporting these structures. Biopolymers, naturally occurring polymers that are found in living organisms, have been seen as a viable solution for ground improvement. Biopolymer treatment has been shown to enhance soil properties such as shear strength, compressive strength, and friction angle. Greater resistance to erosion is expected in samples treated with biopolymers. To confirm the erodibility of treated samples, this study will use the erosion function apparatus (EFA) to quantify the erosion rate of soil specimens with varying biopolymer concentrations. Xanthan gum was the biopolymer used to treat the soil specimens at 0.2%, and 0.4% concentration by weight of the soil. Well-graded Acco sand was used for this experiment. During the experiment, erosion rates were measured for each soil specimen in the EFA at the same velocity. Specimens were not allowed to cure for more than 1 h before testing and were prepared with the same water content and relative density. In this paper, comparisons are made between the tests performed in preliminary experiments in a different flume and those performed in the EFA.

This project aims to quantify how soil aggregate stability changes over time in biopolymer-amended, coarse-grained soil. Biopolymers, which are naturally occurring polymers that are found in living organisms, have been identified as possible materials to use for ground improvement. However, commonly used biopolymers such as xanthan gum and guar gum can be broken down and used by microorganisms in soil. Consequently, prior experiments have not explicitly considered how soil properties change due to biopolymer amendment degradation. To study biopolymer persistence in soil, unamended and biopolymer-amended (1.0% w/w xanthan gum and guar gum) coarse-grained soil samples were incubated in a greenhouse for 0, 5, 15, 30, 60, and 100 days. Following the greenhouse maturation time, soluble polysaccharide content and aggregate stability were measured for all soil samples. Soluble polysaccharide content decreased over time for both the guar gum and xanthan gum amended soils, indicating biopolymer degradation. However, after an initial decrease, aggregate stability increased rapidly for the biopolymer-amended soils, reaching 80%–90% by day 100. These results suggest that biopolymer effects on soil properties persist even as components of the biopolymer degrade within the soil.

This paper reviews fluid-particle interactions and implementation in coupled computational fluid dynamics (CFD) and discrete element modeling (DEM). Soil particles interact with water flow in various geotechnical engineering applications such as seepage and groundwater flow. Understanding these interactions is critical for the design of effective systems to mitigate potential instabilities and manage surface runoff. Coupled CFD and DEM simulations have been used widely to account for the presence of water in soils. In this study, we review the applications of coupled CFD-DEM in geotechnical engineering. Further, we present a coupled CFD-DEM numerical model, developed using both COMSOL Multiphysics and PFC3D. We first validated our model by comparing the model results to the physical tests on settling velocity of a gravel particle in media with different viscosity. Then, we highlighted some challenges and limitations in adopting coupled CFD-DEM in geotechnical research. The developed CFD-DEM model will be used in future studies to model both the surface and internal erosion of various construction soils.

This paper discusses the effect of spatial variability in strength properties of the cement-admixed soil slab on the basal heave stability for braced excavations. Deterministic and random finite element analyses are performed in Optum G2 software. In deterministic analysis, the effect of different strengths and thickness of slab on the basal heave stability are studied. For studying the effect of spatial variability in cement-admixed soil slab, the spatially correlated random fields of undrained shear strength (c_uj) are simulated for varying coefficient of variation (COV) and scale of fluctuation (SOF). Results show that the mean value of the FoS decreases with the increase in COV. The mean value of FoS also tends to decrease as the value of SOF increases from 0.5 to 1.0. Finally, equivalent design strengths are computed for the varying spatial parameters to take in account of the spatial variability in strength properties of the cement-admixed soil slab.

It is well acknowledged that one of the most crucial characteristics for preserving internal stability during and after the construction of mechanically stabilized earth (MSE) is pull-out resistance between geosynthetic reinforcing components and backfill soil. Typically, for the rigid reinforcing materials like steel rods and metallic sheets may have their pull-out resistance which can be directly estimated. Wherein for geosynthetic materials are considered to be flexible and hence, the pull-out resistance could not be measured directly. Using a coefficient of friction, such as tan (δ), where δ is the angle of internal friction, it is possible to compute and analyze the pull-out resistance. However, it has been proved complex to measure the friction coefficient, tan (δ), for geosynthetic reinforcing elements owing to their flexible nature. Numerous academic studies from all over the world have made many attempts to examine the precise behavior and interaction between reinforcing elements and backfill utilizing pull-out parameters in response to this challenge, and efforts are being made to suggest a practical solution. This study aims to investigate the sand-embedded pull-out resistance of various geosynthetic reinforcing materials. The experimentation was done using an in-house fabricated pull-out testing apparatus. Sand was employed in this investigation as a backfill. Additionally, the pull-out resistance in conjunction with a number of reinforcing elements placed in backfill (sand) was also assessed using a random distribution of steel fibers. In this investigation, model embankments were constructed and used to perform the field pull-out tests. The field test results were analyzed and compared to those produced by using conventional sand alone using the pull-out design factors viz., pull-out resistance factor (F*) and scale effect correction factor (α). With reference to the pull-out tests conducted on sand admixed with a random distribution of steel fibers, the F* and α values of geogrid is significantly greater than those of geotextiles due to the better confinement of sand particles within the grid structure. These higher values have been indicated that the sand has adequate resistance for pull-out.

Self-hardening slurries such as cement-bentonite and slag-cement-bentonite have been increasingly used in the installation of subsurface vertical barriers since the 1970s. In this paper, the authors build on previously reported lessons learned from the use of self-hardening slurries in vertical barriers to highlight recent developments and observations related to the applicability, specifications, installation, and testing of self-hardening slurry trenches. These lessons are based on direct observations from recent field applications. Lessons from this recent field experience offer new insight and reinforce existing knowledge. Topics addressed include the switch from type I/II Portland cement to type IL Portland cement, observations from field sampling and testing including coring and in situ permeability testing, comparison of strength and hydraulic conductivity results from mix design samples, wet-grab samples and core samples, discussion of changes in recent specifications, and updates on constructability considerations.

Soil mixing and soil-bentonite-cement slurry trenching methods produce a soil-cement product that can be classified as an intermediate geo-material (IGM). Field sampling and testing for quality control are critical in evaluating the engineering properties of these materials. An effective field sampling and testing program is one that provides an accurate representation of the resulting IGM. While there are several standards for field sampling and testing geo-structural materials, few were developed specifically for soil-cement mixtures created by soil mixing or slurry trenching methods. Available field sampling and testing methods and standards originally developed for other materials need to be carefully applied to soil mixing and slurry trenching projects to ensure that the results are both meaningful and representative of the tested materials. Specifications for soil mixing and slurry trenching projects sometimes contain field testing standards or sampling/testing requirements that are not well suited for the resulting geo-materials. This paper on field sampling and testing complements a previous paper the authors published in the 2023 DFI Sixth International Conference on Grouting & Deep Mixing proceedings, which focused on laboratory testing methods. The objective of this paper is to discuss field sampling and testing methods, such as coring, in situ permeability testing, test pits, sonic drilling, and thin-walled tube sampling, and the applicability of those methods for soil-cement mixtures created in the stated applications. The paper provides recommendations for modifications to testing methods, where appropriate, for use in soil mixing and slurry trenching applications.

This paper revisits the use of the load transfer (i.e., “t-z”) approach for modeling rigid inclusions (RI) and demonstrated through an analysis of a recently published load test case study on an RI-supported embankment in Connecticut. The load on the head of the rigid inclusion was estimated using a published “soil cone” model for the pullout capacity of shallow circular plates that accounts for the peak friction angle and dilation angle of the fill. A consolidation settlement analysis was performed to estimate the profile of ground settlement between RIs for input into a pile “t-z” analysis. The load distribution in the RIs was modeled and compared to the load distribution observed in the full-scale load tests. The modeled and observed results were in very good agreement further supporting the efficacy of the approach as a simple analysis tool.

In the framework of the Herbert Hoover Dike Rehabilitation project, BAUER Foundation Corp. has been tasked with the installation of 17.6 mi (28.3 km) of seepage cutoff wall distributed over three task orders. The cement deep soil mixing method of cutter soil mixing (CSM) is being used to install the wall. Challenging ground conditions such as organic soils and limestone and sandstone layers found in large portions of the project require a pretreatment of the foundation soils. This is performed via replacement borings applying cased Kelly drilling techniques or via pre-drilling using continuous flight augers (CFA). A special focus is put on tie-ins of new wall into existing cutoff wall segments and connections of new wall to existing structures via jet grouting.

The demand for the construction of geological disposal facilities has increased owing to the dearth of sustainable solutions for high-level nuclear waste management. Nuclear waste should be disposed of in deep underground spaces for long-term isolation to prevent radioactivity and overheating hazards. Several microcracks of various sizes exist in deep rock masses. These microcracks cause the inflow of groundwater and outflow of radionuclides, which can hinder the mechanical stability of the disposal facility. Therefore, cracks adjacent to storage spaces must be filled using grouting techniques. At the repository depth (500–1,000 m), the temperature exceeds 60°C owing to the thermal effect arising from radioactive waste and geothermal heat. The properties of cement grouts are affected by temperature and the water–cement ratio. In addition, the performance of cement grout is time dependent, and its viscosity varies with temperature. Considering grouting activities at high ground temperatures (e.g., 60°C), the mechanical and rheological properties (viscosity and yield strength) of grout in high-temperature environments should be investigated. In general, when grouting is performed at high temperatures, injectivity decreases owing to an increase in the viscosity and yield strength of the grouting material. In this study, laboratory experiments are conducted using micro-cement as the grout material to measure the viscosity and yield strength based on the temperature, mixing ratio, and injection time. Furthermore, artificial specimens with joint apertures of less than 1 mm are prepared for grout injection experiments. The injected distance based on different temperatures, mixing ratios, and injection times is analyzed. The injection performance of grout materials is evaluated under different temperatures (20°C–60°C). The injection characteristics are analyzed based on the relationship between the rheological properties and injectivity. Test results show that the viscosity and yield strength of the grout materials increase with temperature, thus resulting in a decrease in injectivity. The findings of this study can provide valuable input parameters for numerical simulations and basic data for in situ grouting operations at high temperatures.

Biopolymers are eco-friendly and sustainable replacements for conventional soil treatment materials like cement and lime. The objective of this paper is to assess the durability of sand treated with varying content of biopolymers, with and without stabilization using clay fillers. Previous studies have shown that treating sand with biopolymers leads to an increase in its strength. However, the strength and long-term durability of such bio-improved sand are affected by severe environmental conditions. In this study, xanthan gum and locust bean gum (separately as well as in proportion), with and without using clay fillers, were used to mix with sand at optimum moisture content. Proctor specimens were prepared and tested for wetting-drying cycles following ASTM D559 with modification. The weight loss of samples after each cycle of wetting-drying was reported. The durability of sand increased with increasing content of biopolymer and the use of a combination of two biopolymers, but durability did not improve with clay filler stabilization.

Rigid inclusions are a ground improvement technique consisting of introducing continuous, vertical elements to increase vertical stiffness and mitigate settlement of soils under load. In the United States, most rigid inclusion projects appear to involve drilled, grouted displacement elements using displacement augers. Displacement rigid inclusions significantly change the properties of the surrounding soil; they improve the strength and stiffness of granular soils due to densification and increasing lateral stresses, and cause displacement, shearing, and consolidation of saturated fine-grained soils. The beneficial effects of installation on the mechanical properties of soil are often ignored during design analyses, mostly due to the difficulty in evaluating post-installation soil properties and in assessing their effect on rigid inclusion performance in a reliable, repeatable way. Ignoring the improvement of mechanical properties of the soil due to installation can yield overly conservative designs. This paper presents a case history where significant densification of a liquefiable granular layer was accomplished through installation of rigid inclusions. The liquefaction potential of the site was assessed through numerous pre- and post-installation cone penetration test (CPT) probes. Comparison of the estimated pre- and post-installation values of factor of safety against liquefaction in the granular layer reveals increases in the factor of safety from an initial range of 0.75−1.0 to values greater than 1.3. Such level of improvement, which is consistent with findings from other authors, is a strong indicator that rigid inclusions are an effective measure to mitigate liquefaction and to upgrade seismic site classification of a site with a liquefiable soil profile. This paper discusses details of the project, site characterization, and liquefaction assessment. It also briefly discusses the mechanics of soil improvement around rigid inclusions, potential limitations and under-conservatism of current post-installation liquefaction assessment methods, and simple hand calculations methods to predict degree of soil densification.

Rigid inclusions (RIs) are no longer a new ground improvement technique. RIs, which are columns typically made of concrete or mortar, are used to reduce settlement and increase bearing capacity. They have been used by many geotechnical engineers, contractors, developers, and owners over the last 30 years. In this paper, we will show that, in fact, they have been used in many forms for centuries. This paper will highlight the wide variety of projects and soils that RIs can be applied to and the associated considerations. Current practice with RIs is in the realm of “ground improvement,” where many techniques are used to mitigate settlement and enhance bearing capacity. Projects that require settlement mitigation only tend to attract many techniques, and a technique is chosen based on its overall economic value (constructability, schedule, value, sustainability benefits, etc.). For projects where RIs are used to improve inadequate bearing capacity of the soils, the choices for foundation support become fewer (e.g., piles, drilled shafts, RIs, or soil mixing). The difference between providing settlement control versus increasing bearing capacity is stark, and between them lies a large range of conditions that requires careful consideration. RIs can be used on projects with a large spectrum of conditions, but often jurisdictions, specifications, and project requirements force the design, installation, and testing of the RIs as if they are piles. This significantly limits the amount of optimization and benefit that the RI solution can offer and discounts the advancements that RI technology offers to our industry. This paper will provide a description of the spectrum of conditions that RIs can be applied to and present the different challenges that apply based on those varying conditions. A hypothetical study will be presented that evaluates how RI behavior varies depending on the soil conditions and the primary purpose of the RI system (settlement mitigation or enhancing bearing capacity).

For a long time, grouting predominantly uses cementitious materials to fill voids and/or create bonding between soil particles, which in general have been performing well in highly permeable soil, such as sands and gravels. However, for soil with low permeability, for example, fine grain soil or coarse grain soil with high fine contents, cementitious materials typically are not applicable due to low flowability. Water-activated polymer (WAP) may be an excellent alternative to cementitious material to expand the groutable spectrum of soils. Among many types of WAPs, this study uses a polymer precursor that is liquid and has a viscosity as low as 25 centipoise, which means it is as flowable as low fat milk. In addition, WAP is made of macro-molecules, and the size of molecules is in the scale of nanometer, which makes them much smaller than cement particles. Therefore, using WAP to replace traditional cementitious materials as grouting materials has great potential to expand the application to fine-grain soils. This study focuses on studying the viscosity of WAP during its curing process as well as its penetration capacity for different pore sizes. The viscosity was measured by a viscometer under a controlled-temperature environment, while the penetration was measured by micro-filteration membrane with sub-micron pores. The results indicate that during the curing process, the viscosity experienced three phases of change: first increase and then decrease and finally increase again. As to penetration, the WAP can easily penetrate through micro-membranes with a pore size of 0.22 μm. Based on the test results, a preliminary estimation of the groutability was performed based on the existing pore size model. It showed that it can be used in many fine-grain soils, which are considered ungroutable for cementitious materials.

In general, soft soil deposits settle excessively. Many strategies have examined soil reinforcing for ground improvement. Stone column (granular pile) is often used to remediate weak soils. A detailed numerical study examined aspects affecting stone column design. The hardening soil and modified cam clay models replicate soils. Published numerical study validated the modelling. The effective characteristics evaluated are the ratio of stone column length to soft soil height L/H, D/L, distribution pattern, centroid spacing between stone columns, cushion soil thickness, and soft clay compression index. Published analytical analysis was compared to numerical data. The study suggests cost-effective stone column design criteria for the location.

The upkeep and rehabilitation of infrastructure damage related to the shrinking and swelling of expansive soils have cost the United States billions of dollars. Biochar, an innovative and eco-friendly additive proven to improve soil permeability, nutrient retention, and mechanical properties, is investigated as an additive to Mississippi chalk. The index properties of the chalk were determined and used to characterize its nature. The mechanical properties of the chalk amended with 6% and 12% biochar were evaluated via the Proctor compaction, compression, and direct shear tests, and the observed results were analyzed to make comparative remarks on how the behavior of the chalk evolved with biochar percentage. The chalk’s compactibility, compressibility, and shear strength increased as the biochar percentage increased. The cohesion coefficient decreased while the friction angle increased with an increased biochar percentage. The increased shear strength of biochar-amended soil is a promising observation of biochar’s potential as a construction material in geo-transportation projects.

One Chicago Square (OCS) is a billion-dollar private development encompassing an entire city block in the River North area of Chicago, Illinois. The project consisted of two high rise towers (55 and 65 stories), along with a four-story below grade parking structure directly adjacent to the existing Chicago Transportation Authority (CTA) Red Line tunnel and station. JDL and Power Construction, the owner/developer and general contractor, respectively, recognized the demands of the proposed excavation and the overall project schedule, which required completion within three years. Additionally, the historic Holy Name Cathedral, directly to the east of the project site, used the existing parking lot on the subject property. In accordance with certain requirements of the proposed development agreement, equivalent parking capacity had to be provided in the proposed below-grade garage within 24 months. These demands, along with cost efficiency, led the project team to choose a top-down construction method for the below-grade work. A design-build approach for the top-down method of the earth retention system and the partnership between the project stakeholders resulted in the overall accomplishment of the project goals. Measured deflections of the earth retention system around the site were controlled and agreed well with the underground construction team’s estimates (often less than our estimates), and instrumentation monitoring in the tunnel indicated negligible movements and no reported damage. The project was completed within the required schedule.

A new multi-story student housing structure required parking below existing grade. The general contractor requested temporary sheet piling for the majority of the project, with a small portion to be permanent sheet piling. Typical vibration restrictions are 1.0 in./s (25.4 mm/s); however, in the historic district the limits were reduced to 0.25 in./s (6.35 mm/s). During the installation of the sheet piling, vibrations were monitored and found to be 0.08 in./s (2.03 mm/s), well below the strict criteria. However, an existing historic brick-and-mortar structure built between 1873 and 1902 was located directly across the street, and there was noticeable impact to the mortar from the vibrations. The project was placed on hold, and a new solution was required to salvage the $90M development. Time was critical; the facility had to be completed before fall semester began. Spacing was critical; the temporary sheet piling was to be placed in the right-of-way with a cast in place wall poured in front. Many alternative solutions were considered, and we concluded a permanent secant wall constructed with drilled shafts and augercast piles was the best solution. The cast in place concrete building wall was eliminated and replaced with the secant wall. Larger diameter and deeper elements were constructed at each column location with smaller diameter secant piles in between. While the secant wall was considerably more expensive, vibrations were eliminated, spacing limitations were resolved, and the entire system was redesigned and constructed to meet the overall schedule.

Hurricane Ida was a Category 4 hurricane that hit the Atlantic coastal region in the fall of 2021. The subsequent rainfall created flooding conditions that inundated streams and rivers throughout the state of NJ. The hurricane also tested the capacity of embankments and retaining walls and their associated factor of safety against failure, throughout the state. Specifically, the flood event from the hurricane impacted a section of gravity block retaining wall about 100 ft along Vosseller Avenue in the township of Bridgewater, NJ. Vosseller Avenue, which sits atop this retaining wall, is a vital access corridor that was closed due to the failure of the retaining wall. The main cause of failure experienced at the retaining wall was due to the sudden rise in water level causing scouring and an overflow condition that undermined and washed out the material backfill behind the wall. This sudden reduction of factor of safety due to material washout caused a base sliding failure between the wall and the rock surface it sits on. American Pile and Foundation was contacted to investigate the field condition and provide an emergency design/repair of the damaged wall section. The solution provided was a permanent cantilever wall system socketed into rock using drilled soldier pile micropiles and permanent reinforced shotcrete facing. The geology encountered at the site location was very hard igneous rock intrusion of basalt and would prove difficult to drill. Site constraints also include an adjacent gravity sewer line underneath the road that could not be disturbed. American Pile was able to expedite the design of the permanent wall system and began construction within a week of notice. The construction process encountered some difficulties with the hard rock geology and difficult access. However, APF was able to adjust the drilling method to the difficult geology and employed the overburden system with a down the hole hammer with success. The micropile soldier piles were successfully installed and socketed into the bedrock. Temporary lagging was installed to allow backfill to be placed to the existing road grade and facilitate reinforcement and placement of the permanent wall shotcrete facing. Utilizing these techniques, the wall was finished in three weeks, and the road reopened just a month after the hurricane damage.

This paper presents a case study of building settlement resulting from an adjacent deep excavation (approximately 5 ft away and 40 ft deep). The settled structure was a multi-story brick building, which leased residential and commercial space. The excavation was supported by steel sheeting and three levels of internal steel bracing. Many aspects of the temporary excavation support system were prescribed in the specifications, including the size of the sheeting, embedment of the sheeting, number of bracing levels, elevation of bracing, and the magnitude and location of the adjacent structure loads. The building was monitored by survey points before, during, and after construction, and lateral movement of the sheeting was measured by inclinometers and survey points. During construction, the maximum lateral movement of the sheeting in front of the structure exceeded the limiting value set by project specification, and due to the proximity, the settlement of the adjacent structure was approximately equal to the lateral movement of the sheeting (causing architectural damage to the structure). This paper discusses the formation of expectations and communication of risk with project stakeholders and provides recommendations for future project planning.

The author performed a geotechnical engineering assessment of repeated failures of a 24-ft-tall cut earth slope along a main highway corridor. The slope was cut into high plasticity native clay soils during the original highway construction and located in the vicinity of stormwater drainage. The purpose of the assessment was to evaluate potential for additional slope failure, identify probable causes of failures, and provide engineering recommendations for stabilization of the slope. Findings of the assessment indicated that shallow groundwater was present in the slope, the native slope soils were significantly disturbed during construction of adjacent below-grade structures, and extension of the slope failure to the upper part of the slope was likely. The author recommended stabilizing the slope as soon as practical. However, while the decision on the stabilization was underway, a slope failure re-occurred approximately three months after the author’s assessment and substantially increased the scope of the stabilization. An emergency slope stabilization for the extended failure areas using soil nails and lateral drains to reinforce the slope and alleviate the shallow groundwater was completed.

The overarching upgrade project at a coal dumping facility in North Vancouver, BC, consisted of a new railcar dumper pit vault with an outfeed conveyor to increase coal handling capacity at the facility. The site is located 200 m (656 ft) from the Burrard Inlet with groundwater table close to grade and coarse sands and gravels, presenting high risk for both groundwater and soil ingress. An active rail yard immediately adjacent to the site was to remain operational throughout the project’s construction. Support of excavation for the multi-level coal dumper vault involved an internally braced three-cell cofferdam with pipe-pipe and pipe-sheet combi pile walls, connected to a four-cell trench that accommodated the dumper vault’s outfeed conveyor tunnel. The center cell of the main dumper pit vault was designed for a maximum excavation depth of 27 m (89 ft), hydrostatic pressures starting 3 m (10 ft) below grade, and surcharge pressures from six adjacent rail lines. Three levels of bracing were used with spans of up to 10.5 m (34 ft) to facilitate the buildout of the permanent structure without cold joints. An unreinforced tremie base plug with tie-down anchors created basal stability against hydraulic uplift. This paper will highlight the challenging design requirements and the detailed construction sequencing that was required for successful installation of the support of excavation system. In addition to complicated geotechnical conditions and constraints due to the geometry of the permanent structure, environmental and health and safety requirements were a driving factor of this project. Construction for the deep excavation was to occur in a live coal handling facility with confined spaces, several contractors, and sensitive waterways. The project was an exceptional example of innovative design and illustrates the potential of a job when coordination and collaboration between the construction team, design team, and owners is prioritized. Support of excavation for the railcar dumper pit vault and outfeed conveyor tunnel was accomplished with a design-build approach.

Emergency reconstruction of the lower retaining wall of a flood-damaged highway in a mountainous part of Japan was safely completed in one season with a pressed-in pipe pile wall and earth anchors. The access to the pile line was limited due to just one lane of the highway left undamaged with an unstable slope below it. The 1,300 mm diameter pipe piles were rotated, simultaneously pressed in, and socketed 1,300 mm into a black schist bedrock through colluvial sand, gravel, and boulder layers. The adoption of this construction method achieved much faster construction with much lower construction cost compared to other types considered.

A permanent, tied back soldier pile and lagging retaining wall has been constructed along the West Virginia Route 2 (WV2) roadway in Wellsburg, West Virginia, as part of the Wellsburg Bridge project. The new bridge allows for the crossing of the Ohio River to connect Wellsburg, West Virginia, to Brilliant, Ohio. An expansion of the original two-lane WV2 roadway was required to allow for inclusion of entry and exit lanes to the bridge. The portion of WV2 requiring expansion is located along a mountainside that has evidence of historical deep-seated slope failures. Limitations in the existing topography required the use of a fill wall to allow for additional width of WV2. However, due to the historical deep-seated instabilities at this location, the type of wall to meet project global stability is limited. A thin creep zone of low residual strength material, known as the Pittsburgh red beds, is located at the soil-rock interface. This problematic material was a key driver of the retaining wall design, requiring innovative methodologies to design the wall and careful considerations for construction to confirm design criteria was met. This paper will summarize the design considerations and challenges faced during construction of this 1,219 m (4,000 ft) long, 12.2 m (40 ft) high retaining wall. Advanced numerical analyses considering the complex subsurface stratigraphy and construction staging required for construction of the soldier pile systems provided an optimized design for the client. Challenges included those associated with an atypical bottom-up construction of a tieback wall that were solved by using low tieback lock-off loads to allow soldier pile movement as the backfill was placed. This resulted in the final position of the top of the soldier piles within project tolerance in most cases. Instrumentation was utilized along with Schnabel’s infrastructure monitoring service (IMS) to track the performance of the wall through construction and to compare measured movements to those predicted by analysis including numerical models of the staged construction.

Through a design-assist to design-build process, Nicholson Construction Company provided alternative permanent support of excavation solutions to Construction Manager LeChase Construction Company of Rochester, New York, for a new addition at Colgate University’s Olin Hall in Hamilton, New York. The alternative designs better met the project needs than the originally proposed permanent support of excavation solution, which limited usable space in the planned addition and included inherent risks from the construction methods of installation. The design and construction teams’ engagement led to a unique solution specifically tailored to the project needs and constraints.

This rehabilitation project aimed to safeguard human life while mitigating the intolerable risk of detrimental social, economic, and environmental impacts in the area. The cutoff wall, a critical feature in the dike rehabilitation, is designed to mitigate any existing internal erosion, also referred to as “piping” and to prevent any further damage to the internal structure of a dike. To eliminate the hydraulic piping that is occurring through and under the embankment of the Herbert Hoover Dike (HHD or Dike) surrounding Lake Okeechobee in South Florida, the United States Army Corps Engineers (USACE) designed to install a partial cutoff wall using in situ soil mixed with cementitious materials. The typical process for evaluating the integrity of the cutoff wall was to obtain core samples of the cutoff wall for visual inspection, perform unconfined compressive strength tests, and to conduct in situ permeability testing. Recent advancements in geophysical technology specialty imaging have led USACE to adopt optical televiewer (OPTV) and closed-circuit television (CCTV) technology for inspecting the boreholes as an integral part of the QA/QC process. During inspection, the OPTV camera survey produced a high resolution 360° continuous detailed and oriented image of the borehole side walls. The CCTV camera survey provided a continuous downhole and side-view recording of the conditions of the borehole side walls. In this case study, the overall benefits and lessons learned through the use of geophysical imaging technology will be discussed in detail.

In March 2019, floodwaters on the Missouri River reached within 12 in. (0.3 m) of the top of the levee and led to underseepage distress to the Lake Waconda Levee resulting in internal erosion of the foundation soils, as evidenced by sand boils and seepage areas at the landside levee toe. A 1,900-ft (579.5 m) riverside seepage barrier was designed and constructed using the one-pass trench mixing method to remediate underseepage distress where the thin clay blanket included clean and silty sand strata interbedded with the fine-grained material. The one-pass method has not been previously used on federal levees, so a robust quality control (QC) and quality assurance (QA) testing program was specified, including supplemental subsurface explorations along the alignment, a full-scale test section, laboratory testing, and confirmatory coring. The design and results of the wall construction are presented.

This paper presents two case studies from the IH-35E Phase 2 design-build project in north Texas, highlighting the successful utilization of geotextiles to overcome construction and design challenges. The first case study focuses on the reinforcement of steep side slopes, where the limited right of way made the construction of shallow slopes difficult and costly. Instead of using expensive retaining walls, a cost-effective reinforced soil slope (RSS) solution was implemented by embedding geogrid reinforcement in the slopes. The second case study addresses the construction of roadways over an existing lake, specifically the filling of a portion of the Sandy Lake Pond. Soft soils and limited construction time posed challenges for stabilization. Two options were considered, and geogrid reinforcement combined with crushed stone was implemented as a cost-effective and timely solution. These case studies demonstrate the benefits of geotextile reinforcement in geotechnical engineering projects. By using geogrids, the IH-35E Phase 2 project achieved cost savings, accelerated construction schedules, and ensured stability in challenging soil conditions. The successful implementation of geotextiles serves as a valuable reference for future infrastructure projects facing similar geotechnical challenges.

The planned bridge approach embankment located at the Hamner Avenue Bridge over the Santa Ana River in Norco, CA, is located in a high-risk seismic area. The embankment will be constructed on fill overlying young alluvial river deposits. Under the site design earthquake of magnitude 7.7 and peak ground surface acceleration of 0.57 g, the embankment site will be liquefied and potentially trigger lateral spreading. Treatment by Vibro Replacement Stone Columns was adopted to mitigate the site liquefaction and lateral spreading hazards below the planned embankment retaining wall footprint. To densify the liquefiable sands, the specialty geotechnical contractor performed liquefaction analysis and determined the stone column replacement ratio and treatment based on the soil fines content and pre-treatment CPT tip resistance. The contractor used a real time data acquisition system to monitor and record the stone column installation, including the vibrator penetration depth, electric current, and air pressure, which allowed the contractor and engineer to interpolate stone column diameter as a function of depth. This system provided a reliable field quality control record to the design engineer and the client. As part of the project QA/QC process, 20 post-treatments CPTs were performed and analyzed, which confirmed all the design densification criteria achieved. This paper discusses the project design, construction, and quality controls. The soil densification effectiveness was evaluated statistically by the comparison of the pre- and post-CPTs as a function the CPT Ic values.

A 241-acre site development was planned in an area known as Tremley Point in Linden, New Jersey. The plan was to build eight large warehouses and access roads to the site and within the site. Ground improvement was required due to the presence of variable and compressible soil. In addition to soil variability, the existing grading and past loading history of the site varied considerably. Surcharging, deep dynamic compaction, and rigid inclusions (RIs) were used to minimize long-term settlement to meet the project criteria of 2 in. Additionally, roadway embankments adjacent to a newly constructed bridge, which required up to 26 ft of fill to be placed on marshland, were also supported on rigid inclusions. This paper will provide an overview of the support provided, the variables controlling the designs, a summary of the load test data, and a discussion of how that data was used to optimize the RI design. Menard’s proprietary name for RIs is Controlled Modulus Column (CMC), which is how we will refer to the RIs throughout this paper.