Journal of Geotechnical and Geoenvironmental Engineering

The authors, to their knowledge for the first time, produced two complete principal soil water retention curves (SWRCs) under both positive and negative matric suction regimes. An innovative testing technique combining the transient water release and imbibition method (TRIM) and constant flow method (CFM) was used to identify the principal paths of SWRC in the positive pore-water pressure regime under unsaturated conditions. A negative matric suction of 9.8 kPa is needed to reach full saturation or close the loop of the SWRC for a silty soil. This work pushes the understanding of the interaction of soil and water into new territory by quantifying the boundaries of the SWRC over the entire suction domain, including both wetting and drying conditions that are relevant to field conditions such as slope wetting under heavy rainfall or rapid groundwater table rise in earthen dams or levees.

Finite-element analyses are performed of centrifuge tests consisting of untreated and drain-treated lateral spread sites, with the goal of evaluating the ability of numerical simulations to predict the response of sites improved with prefabricated vertical drains. Finite-element models of varying complexity are analyzed: a two-dimensional model of the full centrifuge test, a three-dimensional unit cell model around a single drain, and a two-dimensional unit cell model. All the finite-element models predict pore pressures consistent with the centrifuge tests. The deformation responses of the finite-element models show that unit cell analyses produce significantly larger deformations than those observed in the centrifuge. This result is caused by the fact that the centrifuge test geometry is not well represented by the infinite slope condition assumed in a unit cell. The full two-dimensional model predicts deformations that are more consistent with those of the centrifuge because it can capture the rotational mode of deformation experienced in the centrifuge. These results indicate that the expected mode of deformation should be considered when selecting the appropriate finite-element model to analyze a site. The simulations also show that constitutive models for liquefiable soils significantly overestimate the volumetric stiffness, which leads to inaccurate modeling of the diffusion process unless the model is appropriately modified. This issue is critical when simulating the performance of drain-treated sites.

The presence of nano-sized particles on the surface of sand grains can significantly influence the mechanical, physical, and chemical behavior of the sand because of the effects of contacts between particles. This study quantified the change in small strain stiffness caused by the presence of iron oxide particles (hematite and goethite) that were chemically sorbed onto uncemented silica sand. Particularly, the change in contact mode between sand particles, caused by the presence of the nanoparticles, was studied. The iron oxide coating density of coated sands was controlled by changing the substrate sand particle size, ranging from 0.11 to 0.72 mm in diameter, with corresponding iron contents ranging from $0.13\hspace{0.17em}\text{mg iron oxide}/\text{g sand}\hspace{0.17em}\left(\text{goethite}\right)$ to $6.4\hspace{0.17em}\text{mg iron oxide}/\text{g sand}\hspace{0.17em}\left(\text{hematite}\right)$. The presence of the iron oxide nanoparticles altered the contact mode between particles and, correspondingly, the small strain stiffness as a function of the initial relative density, applied stress, iron content, and substrate particle size. The macroscale experimental results were analyzed via contact mechanics (i.e., Hertz and Mindlin contacts) to gain a more fundamental understanding of changes that iron oxide coatings make on the behavior of sand.

Ground movements observed during foundation installation and basement construction of a residential 53-story RC tower are presented. The One Museum Park West building is located in Chicago, Illinois, and was developed using a combination of bottom-up methods, used for the construction of a central concrete core of the building, and top-down methods to build five levels of basements. The excavation extended 13–15 m below grade and was made through soft to medium-stiff clays. The building was supported by drilled shafts and a perimeter wall formed by secant piles that transitioned to tangent piles below the bottom of the cut. The system was laterally braced with RC floor slabs structurally connected to the secant pile walls and the RC core. Field performance data were collected by means of settlement points and inclinometers located close to the walls on two sides of the excavation. The construction sequence and attendant ground movements during each main activity are summarized. As much as 160 mm of settlement was recorded in the adjacent streets throughout construction. Wall and foundation installation accounted for approximately 35% of the total settlements during construction, whereas top-down construction of the basement resulted in approximately 40% of the total settlements. These data emphasize the importance of considering all construction activities when making predictions of ground movements adjacent to deep supported excavations.

The potential for downslope bentonite erosion from a geosynthetic clay liner (GCL) subjected to an imposed daily surface flow of deionized water is examined for 10 GCLs with different carrier and cover geotextiles, bentonite (powdered and fine and coarse grained and some with a polymer-enhancement additive), and a polypropylene coating on the carrier geotextile. The erosion was similar but more visible in products with a white geotextile than in those with a black geotextile. Also, the erosion features were similar but more visible with nonwoven geotextiles than with woven geotextiles. Polymer-enhanced sodium bentonite substantially slowed the formation of erosion features. A polypropylene coating over the upper geotextile prevented erosion features from developing by keeping water from penetrating into the bentonite layer when subjected to 60 daily imposed-flow/air-drying cycles.

The suction embedded plate anchor (SEPLA) is a promising deepwater anchoring solution that uses a suction caisson to install a plate anchor vertically to a precise depth within the seabed. The plate anchor is then rotated from its vertical position toward an inclination approximately normal to the load applied by the mooring line in a process known as keying. This configuration reduces the embedment depth and, in typically increasing strength with depth soils, diminishes the installed capacity of the anchor. Therefore, an accurate prediction of the keying behavior of SEPLAs is crucial for offshore operations. Recently, plasticity approaches that combine a yield surface written directly in terms of the applied loads on the anchor with an associated flow rule have been suggested. However, the combined loading yield surface has been defined only for a flat square or rectangular plate. None of these approaches directly account for the resistance of the relatively large anchor shank used to attach the mooring line. The results described in this paper show (1) the impact of the joint plate and shank on the size and shape of the combined loading yield surface and (2) the subsequent impact on predicting the keying behavior of SEPLAs using the plasticity approach. The influence of anchor thickness and shank height on the capacity of an idealized plane-strain anchor is first defined through two-dimensional finite-element (FE) studies. Then, the yield surface parameters for a typical plate and anchor size are provided from three-dimensional FE analysis. The keying behavior of this anchor when subjected to pullout loading from an anchor chain is simulated using the plasticity approach and the results are compared with keying paths for a simple plate anchor without a shank. The predictions using parameters derived from a plate anchor with a shank significantly outperform those using parameters derived from a plate anchor without a shank.

Large-scale cubical triaxial tests were conducted to investigate the behavior of reinforced and unreinforced subballast under cyclic load. Granular material with an average particle size ($D_{50}$) of 3.3 mm and geocell with a depth of 150 mm and nominal area of $46\times {10}^3\hspace{0.17em}{\text{mm}}^2$ were used in this study. The laboratory results proved that subballast stabilization was influenced by the number of cycles ($N$), the confining pressure (${\sigma }_3^{\prime }$), and the frequency of train-caused vibration ($f$). The experimental results also confirmed that the geocells influenced the subballast behavior under cyclic loading, particularly at low confining pressure and high frequency. The additional confining pressure induced by the geocell reduced its vertical and volumetric strains. The optimum confining pressure required to reduce excessive volumetric dilation also was identified in this study. An empirical model using a mechanistic approach is proposed to determine the additional confinement induced by the geocells, as well as the practical implications of the experimental outcomes.

In the current study, the load responses and interaction effects of piled rafts embedded in sands were investigated. A series of centrifuge load tests were conducted using different types of model foundations. Single piles, group piles, piled rafts, and unpiled rafts were adopted in the tests to analyze various interaction effects of piled rafts. The load-settlement curves of piled rafts were similar to those of group piles for the initial settlement range and became similar to those of rafts as settlement increased. The pile-group, pile-to-raft, and raft-to-pile interaction factors showed state-dependent and nonlinear variations with settlement. Both pile-to-raft and raft-to-pile interaction factors decreased within the initial settlement range and increased with increasing settlement. The range of pile-to-raft interaction factor values was much larger than the range of values for the raft-to-pile interaction factor. The load response and load transfer relationship of piles for piled rafts were different from those of single piles, showing that the effect of raft-to-pile interaction was more dominant within the upper soil zone. The mobilized factor of safety for rafts was always higher than the safety factor of piles and piled rafts because of the lower mobilized load-carrying capacity of rafts.

Many compacted embankments are composed of expansive soils. Water from landscape irrigation, precipitation, and subsurface seepage can gradually infiltrate throughout the fill and cause both vertical movement and lateral expansion of the fill-slope zone. Lateral stretching from expansion can cause distress to surface improvements and structures built near the crest of the slope. Slope inclinometers installed within the slope near the crest would register lateral movement that is the result of the fill’s lateral expansion. This paper describes the mechanism of lateral extension of expansive fill embankments and presents examples of resulting distress features. A test procedure is described for measuring wetting-induced vertical and lateral strains on compacted specimens using triaxial equipment. The paper also recommends a procedure, the lateral fill extension (LFE) method, for calculating the amounts of heave or settlement and lateral movement as a function of the slope’s geometry, the soil’s vertical and lateral swell-collapse characteristics, the fill’s oversize fraction, and the degree of wetting. Limitations of the method and mitigation of the effects of LFE are briefly discussed.

This paper presents a fuzzy set–based robust geotechnical design (RGD) approach for the design of earth slopes in which uncertain soil parameters are represented as fuzzy sets. For a slope with fuzzy sets as inputs, the stability (factor of safety) of the slope is also a fuzzy set. The failure probability of the slope can readily be determined based on the obtained fuzzy factor of safety; further, the design robustness in terms of the signal-to-noise ratio (SNR) can also be evaluated. The purpose of the RGD is to derive a design that is robust against the uncertainty in the input parameters, with an explicit consideration on safety and cost. Therefore, a multiobjective optimization is performed and a three-dimensional or two-dimensional Pareto front showing a trade-off between objectives can be obtained, which allows for an informed design decision. The effectiveness of the proposed fuzzy set–based RGD approach is demonstrated through an illustrative example.

To evaluate the effect of soil-foundation interaction on the earthquake response of structures, centrifuge tests were performed using an in-flight earthquake simulator. The test specimen was composed of a single-degree-of-freedom structure model, a shallow foundation, and subsoil deposits in a centrifuge container. The test parameters were the dynamic period of the structure model, the centrifugal acceleration level, and the type and level of input earthquake accelerations. The test results showed that the lateral forces of the structures were limited by the soil-bearing strength (i.e., ultimate moment capacity of the foundation) and the damping effect owing to the rocking motion of the foundation. Thus, even when the periods of the structures were close to the site periods, the lateral forces did not significantly increase. However, it should be noted that, because of the damping effect of the foundation, the maximum seismic lateral load of the structures exceeded the load statically determined by the soil-bearing strength. This issue should be addressed for the safe design of structures and members. In this test, the maximum damping ratio for rocking due to the rocking motion was estimated to be 0.31.

Landslides and slope failures in natural clay-rich materials are frequently observed in coastal areas and other areas where these materials were deposited in a saline water environment. High sodium chloride (NaCl) concentration in the pore fluid results from deposition in this environment. As shown by the results of this study, subsequent reduction in the NaCl concentration results in reduction in fully softened shear strength, with potentially significant reduction in slope stability. Fourteen sample materials were collected from seven different landslide areas in Niigata Prefecture, Japan, to evaluate the effect of saline water on fully softened shear strength (FSSS). The sample materials were collected from the intact mudstones and the sliding surface materials. Pore waters from the powdered sliding surface materials exhibited low concentrations of NaCl; however, the pore waters in the powdered intact rock samples exhibited a high concentration of NaCl. Washing of NaCl from the powdered intact rock samples caused a significant drop in FSSS, whereas mixing the sliding surface materials with NaCl at 0.5-M concentration increased the FSSS of the samples significantly. To evaluate the effect of saline water on various types of clay minerals, 12 samples—nine with montmorillonite as the clay mineral and three with kaolinite as the clay mineral—were prepared in the laboratory, and Atterberg limits and FSSS of these mineral mixtures were measured. There was a significant increase in the FSSS when the mineral mixtures with more than 9.5% montmorillonite were tested with saline water. The effect was negligible or negative for mineral mixtures having 9.5% or less montmorillonite content and any amount of kaolinite. An excellent correlation was observed between the liquid limits, plasticity indexes, and corresponding fully softened friction angles irrespective of the type of pore water. Likewise, there was a good correlation between the ratios of the liquid limits and plasticity indexes measured with different pore waters and the corresponding ratios of the fully softened shear strengths. It was observed that the reduction in FSSS of powdered intact rock with NaCl leaching could reduce the calculated factor of safety of the landslides by more than 0.3, demonstrating the negative effect of NaCl leaching from the slope materials on the stability of slopes.

By using the state-dependent strength criterion and dilatancy function, a state-dependent nonassociated elastoplasticity hardening model was proposed to unify modeling the constitutive relationships of sands with different initial void ratios. According to the second-order work theory, the criteria for predicting the potential instability and static liquefaction of sands were obtained. The proposed model and criteria were used to predict a series of isotropically consolidated and $K_0$-consolidated undrained triaxial tests. The results showed that the potentially unstable point and the onset of static liquefaction under undrained conditions coincided with the attainment of a deviatoric stress peak in very loose sand, whereas, with the decrease of the initial void ratio, the onset of static liquefaction fell behind the potential instability. When the sand specimen was dense enough, static liquefaction did not occur, although the stress state was located inside of the potentially unstable region. The potential instability and static liquefaction occurred before the effective stress reached the failure surface, and they were the precursors though not the results of the sand failures.

This work presents a critical evaluation of the model factor for the mobilized strength design (MSD) method for cantilever deflection in undrained soft to medium-stiff clay. The model factor is characterized in two parts. A correction factor $\eta$ is first defined as the ratio between the wall-top deflection computed from the FEM and its corresponding value computed from the MSD. The hardening soil with a small-strain model is used in FEM. The statistics of $\eta$ are evaluated using 82 numerical simulations. Because $\eta$ is not random, and therefore cannot be modeled directly as a random variable, it is decomposed as a product of a systematic part ($f$) and a random part (${\eta }^{\ast }$). The random part is modeled as a lognormal random variable with a mean of 1.01 and a coefficient of variation (COV) of 0.18. The model factor for FEM (${\epsilon }_{\mathrm{FEM}}$) is next defined as the ratio between the measured wall-top deflection and the corresponding FEM result. The statistics of ${\epsilon }_{\mathrm{FEM}}$ are evaluated using 45 field cases. The ratio ${\epsilon }_{\mathrm{FEM}}$ is random and can be modeled directly as a lognormal random variable with a mean of 1.01 and a COV of 0.21. The model factor for MSD (${\epsilon }_{\mathrm{MSD}}$) is finally derived from the product of $\eta$ and ${\epsilon }_{\mathrm{FEM}}$. This proposed approach is validated by 14 centrifuge tests. The importance of including the proposed model factor ${\epsilon }_{\mathrm{MSD}}$ in reliability analysis is illustrated using a field example.

The tailings beach slope is a fundamental parameter for the design and operation of tailings storage facilities because it affects the tailings storage capacity, pond levels, and phreatic surfaces within the containment structures. Understanding tailings beach development is particularly important for thickened and paste tailings facilities, where the tailings can form a self-stacking structure. This paper presents a theoretical tailings deposition model that can describe the formation of tailings beach slopes in both subaerial and subaqueous deposition environments. The depositional behavior and deposition mechanisms are investigated from both geotechnical and hydraulic engineering perspectives. The model is developed to capture deposition mechanisms based on the principles of soil mechanics and fluid mechanics. The governing differential equations can be solved using a numerical technique, and the solution scheme can readily be implemented in computer languages. Case studies for subaerial deposition demonstrate that the modeling results are in agreement with laboratory flume testing and field measurements. The proposed model considers geotechnical and rheological properties of tailings, water pressures, operation parameters, and site topographic conditions. A sensitivity study was carried out to provide insight into the effects of influencing factors on the beach slope.

The buckling response of straight and initially bent, i.e., geometrically imperfect, end-bearing piles in soil subjected to axial load has been examined in the current study through FEM, considering geometric and material nonlinearities exclusively. Nonlinear buckling analysis is performed herein using the Static/Riks method. Material nonlinearity has been considered by assuming elastic-plastic stress-strain response of the steel pile and the surrounding soil. Parametric sensitivity studies have been performed by changing the slenderness ratios and the initial curvature of the piles. The analyses results show that the load-carrying capacity of the piles decreases with increasing pile curvature and increasing slenderness ratio of the initially bent piles. It was also found that the piles with a half-sine bent carry smaller loads than the piles with a quarter-sine bent.

Although many traditional soil stabilizers (e.g., lime, cement, gypsum, and fly ash) have been widely and effectively used for ground improvement, they often adversely affect the surrounding soil and groundwater environment. Moreover, traditionally treated soils have shown excessive brittle behavior, especially under cyclic loads, which is often undesirable for structures such as rail embankments and airport runways. To establish an alternative stabilizer that could overcome these problems, this paper presents the results of a series of cyclic triaxial tests on the use of lignosulfonate (a by-product of the timber industry), an environmentally friendly soil stabilizer effective for treating fine sandy silt that formed the bulk of the embankment fill at Penrith, Australia. The influence of lignosulfonate on the stress-strain behavior, resilient modulus, and excess pore pressure development of the treated soil is discussed.