Journal of Geotechnical and Geoenvironmental Engineering

Multiinterface direct shear tests have indicated that, under high normal stress conditions, a HDPE geomembrane can be damaged from interface shear against an overlying gravel drainage layer, with or without a protection nonwoven geotextile in between. A brief overview of the experimental results is presented and recommendations are provided for mitigation of such damage in field applications.

An experimental program was carried out to study the variation of shear strength of cross-anisotropic deposits of fine Nevada sand under three-dimensional (3D) conditions using a recently developed torsion shear apparatus. A total of 44 drained torsion shear tests were performed at a constant mean confining stress, ${\sigma }_m$, constant intermediate principal stress ratios, as indicated by $b=\left({\sigma }_2-{\sigma }_3\right)/\left({\sigma }_1-{\sigma }_3\right)$, and principal stress directions, $\alpha$. The experiments were performed on large hollow cylinder specimens deposited by dry pluviation and tested in an automated torsion shear apparatus. The specimens had a height of 40 cm, an average diameter of 20 cm, and a wall thickness of 2 cm. The 3D failure surface of fine Nevada sand is presented with discrete combinations of $\alpha$ and intermediate principal stress. The effects of these two variables on the shape of the failure surface are presented. The friction angles are highest for $\alpha =0°$ for all $b$-values and show a dip in strength with the lowest values near $\alpha =67.5°$, at which the major principal stress is inclined such that the potential shear band directions coincide with the bedding planes, which exhibit the lowest strengths. Overall, the friction angle varies from 57 to 32°, while the conventional friction angle from a triaxial compression test on a vertical specimen produced 41°, which is often employed in a given geotechnical engineering project.

Coal ashes discharged from coal-fired power plants have recently been gaining attention as a new form of geomaterials. They have been popularly used as ground materials for the improvement of unsuitable soil and for foam-mixed solidified soil. However, development of more applications is needed in light of the enormous amount of coal ash generated. The current study was performed to confirm the applicability of granulated coal ash (GCA) as reclamation material with adequate resistance against liquefaction during an earthquake. In this study, the liquefaction characteristics of GCA were investigated through cyclic triaxial tests and online pseudodynamic response tests, and the results were compared with those of natural sands to examine the cyclic shear properties of the material. The triaxial test results revealed that the slope of the cyclic shear strength curve of GCA was gentle under high confining pressure, but it was still higher than those of natural sands. It was observed that GCA underwent remarkable particle crushing, resulting in higher cumulative dissipated energy, and this accounted for the higher cyclic shear strength when compared with natural sand. Moreover, the online pseudodynamic response tests performed using a hollow torsional shear test apparatus showed that GCA exhibited slower excess pore water pressure buildup when compared with Toyoura sand for the same level of input motion. The presence of a GCA layer in a saturated sandy ground had beneficial effects on the earthquake response.

Centrifuge models of soft-clay deposits were shaken with suites of earthquake ground motions to study site response over a wide strain range. The models were constructed in an innovative hinged-plate container to effectively reproduce one-dimensional ground-response boundary conditions. Dense sensor arrays facilitate back-calculation of modulus-reduction and damping values that show modest misfits from empirical models. Low-amplitude base motions produced nearly elastic response in which ground motions were amplified through the soil column, and the fundamental site period was approximately 1.0 s. High-intensity base motions produced shear strains higher than 10%, mobilizing shear failure in clay at stresses larger than the undrained monotonic shear strength. The authors attribute these high mobilized stresses to rate effects, which should be considered in strength-parameter selection for nonlinear analysis. This nonlinear response deamplified short-period spectral accelerations and lengthened the site period to 3.0 s. The nonlinearity in spectral amplification is parameterized in a form used for site terms in ground-motion prediction equations to provide empirical constraint unavailable from ground-motion databases.

This research investigates the use of polymer-infused roots for soil-improvement applications. By infusing polymer through the easily accessible above-surface plant stems, polymer-infused roots can be created without subsurface excavations. Evaluation of this technique involves identifying the improvements from polymer-infused roots by measuring in situ shear strength of soil using a vane shear apparatus and by measuring the tensile strength using split-tension tests in the laboratory. Roots of Ruellia squarrosa and Artemisia annua plants were infused with a mixture of epoxy resin and polyoxyalkylamine blend hardener. Compared with noninfused roots, polymer-infused roots provided an additional 22 kPa (28%) of shear strength for elastic silt and an additional 13.1 kPa (25%) of shear strength for low-plasticity clay with a corresponding 13.6-kPa (55%) increase in tensile strength for the low-plasticity clay. Acid hydrolysis testing was performed to ascertain the potential durability of the polymer-infused roots. The 4% plant material mass loss measured for the infused samples was significantly less than the 18% plant material mass loss for the noninfused samples, demonstrating the protective effect of the polymer infusion process.

The classic experiment of a yielding trapdoor in (two-dimensional) plane strain beneath a granular mass is revisited, this time in the high-gravity environment of a geotechnical centrifuge. High-speed acquisition of load and displacement data makes it possible to examine the arching behavior of geomaterials. Results indicate the formation above the trapdoor of a physical arch, which evolves from an initially curved configuration to a triangular shape and ultimately to a prismatic sliding mass with vertical sides. Simple expressions for the reduced load caused by arching are proposed. Predictions using these expressions compare favorably with test measurements, paving the way for potential application to the design of underground structures.

Interpretation of experimental and field cone penetration test (CPT) data from across a broad range of stress conditions requires defining the dependence of the measurements on overburden stress and other influencing factors. This paper examines three possible methods for overburden normalization of CPT tip resistance in sand at the same state parameter or same relative state parameter. The three methods for determining state-based normalized tip resistance at a reference overburden stress of 101.3 kPa (1 atm) are evaluated against calibration chamber test data for four well-studied clean sands. The CPT data from the calibration chamber tests are corrected for chamber boundary effects using two different methods to illustrate the effect this step has on derived relationships. The CPT data are further normalized to a common lateral earth pressure coefficient to illustrate the effect of this step. The three methods for state-based overburden normalization were evaluated for bias and dispersion against the calibration chamber data, including their dependence on the applied chamber correction relationship. The dependence of state-based overburden normalized tip resistances on the crushing behavior of the clean sand was evaluated by examination of one-dimensional limiting compression curves for these four sands. Finally, correlations for estimating the state parameter or relative state parameter from the state-based overburden normalized tip resistance were developed and evaluated based on the examined data.

An experimental investigation was undertaken to compare the performance of a largely intact steel culvert with well-compacted backfill with a corroded culvert in loose backfill. The behavior of both structures is compared during backfilling and under imposed surface loads equivalent to the standard American and Canadian design trucks at two burial depths (0.6 and 0.9 m). During backfilling, the deteriorated culvert deflections were much larger than the intact culvert because of differences in both culvert and backfill stiffnesses. Under surface loading, the deteriorated culvert experienced higher deflections and bending moments, whereas the intact culvert experienced higher thrust forces. It was found that, under relatively shallow cover, the load from one wheel pad of the axle influenced the behavior of the culvert under the other wheel pad. The deteriorated culvert was then tested to failure with localized bending in the crown and buckling of the remaining steel in the corroded region serving as indicators of failure.

Hydraulic fracturing in clayey soils can be triggered by either tensile or shear failure. In this paper, the physical meanings of various equations to predict fracture initiation pressure proposed in the past are discussed using the cavity expansion theory. In particular, when fracturing pressure is plotted against initial confining pressure, published laboratory test results as well as analytical models show a linear relationship. When the slope is close to 2, fracture is initiated by tensile failure of the clay, whereas when the slope is close to 1, it is initiated by shear failure of the clay. In this study, the analytical models, validated only on laboratory test data to date, were applied to unique data from field grouting work in which extensive soil fracturing was carried out to improve the mechanical characteristics of the soft silty clay underlying a bell tower in Venice, Italy. By a careful assessment of initial confining pressure in the field, the variation in recorded injection pressures with confining pressure was examined. Results suggest that the fractures at this site were likely to be initiated by shear failure of the clay, and the values were similar to what was predicted by the model with the shear failure criterion.

Accurately predicting peak penetration resistance $q_{\text{peak}}$ during spudcan installation into sand overlying clay is crucial to an offshore mobile jack-up industry still suffering regular punch-through failures. This paper describes a series of spudcan penetration tests performed on medium-loose sand overlying clay and compares the response to existing centrifuge data from tests performed on dense sand overlying clay. Together these data demonstrate that punch-through is a potential problem for both dense and loose sand overlying clay soil stratigraphies. Using this experimental database, a failure-stress-dependent model has been modified to account for the embedment depth, and the depth of occurrence of $q_{\text{peak}}$ is shown to be a function of the sand thickness $H_s$. The model then was recalibrated, taking these findings into account, for a larger range of material properties and ratios of sand thickness to spudcan diameter ($H_s/D$). Finally, the performance of the modified and recalibrated model is verified by comparing its predictions with those calculated using current guidelines. The comparisons show that the modified model yields more accurate predictions of $q_{\text{peak}}$ over the range of $H_s/D$ ratios of practical interest, which when used in practice will potentially mitigate the risk of unexpected punch-through on sand overlying clay stratigraphies.

The design of a railway track substructure requires a realistic understanding of the resilient behavior of the underlying track foundation materials, namely, the subballast and subgrade layers. Currently, the best available method of characterizing the resilient behavior of track foundation materials is through the execution of cyclic triaxial tests, although these do not have the ability to impose principal stress rotation (PSR) on test specimens. A previous paper by the authors demonstrated that PSR increases the rate of permanent strain development. This paper reports on the effects of PSR on the resilient behavior of track foundation materials. Four different reconstituted soils selected to represent typical track foundation materials were subjected to undrained cyclic and torsional shear tests in a hollow-cylinder apparatus. It was established that PSR reduces the resilient modulus of the materials compared with cyclic loading without PSR. The effects of PSR as a function of clay content, overconsolidation ratio (OCR), and consolidation regime (isotropic or anisotropic) were also investigated.

Bridge scour is the loss of soil by erosion because of water flowing around bridge supports. Scour has been the number one cause of bridge failure in the United States with an average annual rate of 22 bridges collapsing or being closed owing to severe deformation. This paper addresses three topics related to bridge scour. First, a set of databases was used to quantify the statistical parameters associated with the scatter between the predicted and measured pier scour depth, as well as the probability that a deterministically predicted pier scour depth will be exceeded. These databases also were used to provide the bias factors in current predictions. Secondly, these statistical parameters were used to develop a reliability-based load and resistance factor design for shallow and deep foundations subjected to scour. The goal was to provide a design procedure where the reliability of the foundation is the same with or without scour. Reliability only addresses the probability of success and, therefore, of failure. Finally, the discussion was broadened by using the concept of risk defined as the probability of failure times the value of the consequences. In this third part, the risk associated with bridge scour was quantified and compared to risks associated with other engineering structures. Target values of acceptable risk were recommended as part of the conclusions.

An approach is presented for predicting saturated hydraulic conductivity ($k_{\text{sat}}$) and the unsaturated hydraulic conductivity function (HCF) of coarse-grained soils using pore-scale modeling of liquid configurations in idealized unit pores. Procedures are described for estimating $k_{\text{sat}}$ and the HCF from simple measurements of grain size distribution (GSD) obtained using mechanical sieve analysis. Measured GSD is converted into an equivalent population of spherical particles arranged to form subassemblies representing relatively loose and relatively dense particle configurations. Capillary theory and the geometry of unit pores formed within the particle subassemblies are used to quantify pore-scale liquid configurations as a function of matric suction. Corresponding hydraulic conductivity is calculated from pore-scale hydrodynamic considerations. Comparison between measured and predicted $k_{\text{sat}}$ for a suite of sand-sized soils demonstrates that the approach is an improvement over existing approaches, based solely on empirical correlation between hydraulic conductivity and GSD, porosity, or fractional grain size (e.g., $d_{10}$). The unsaturated HCF is effectively predicted to degrees of saturation as low as 20%. Assumptions and constraints in the framework restrict the applicability of the model to materials with a rigid matrix, with particles predominantly in the sand- to silt-sized range.

Nanoscale iron particles (NIPs) have recently been shown to be effective for dehalogenation of recalcitrant organic contaminants such as pentachlorophenol and dinitrotoluene in the environment. However, the effective transport of NIPs into the contaminated subsurface zosnes is crucial for the success of in situ remediation. Previous studies have shown that the transport of NIPs in soils is very limited and surface modification of NIPs is required to achieve adequate transport. This paper investigates the transport of lactate-modified NIPs (LMNIPs) through four different sand porous media. A series of laboratory column experiments was conducted to quantify the transport of bare NIPs and LMNIPs at two slurry concentrations, $1\hspace{0.17em}\text{and}\hspace{0.17em}4\hspace{0.17em}\text{g/L}$, under two flow velocities. The NIPs used in this study possessed magnetic properties; thus, a magnetic susceptibility sensor system was used to monitor the changes in magnetic susceptibility (MS) along the length of the column at different times during the experiments. At the end of testing, the distribution of total Fe in the sand column was measured. Results showed a linear correlation between the Fe concentration and MS, and that was used to assess the transport of NIPs and LMNIPs in the sand columns. Results showed that LMNIPs transported better than the bare NIPs, and a higher concentration of $4\hspace{0.17em}\text{g/L}$ LMNIPs exhibited uniform and greater transport compared with other test conditions. Transport of NIPs increased in the following order: $\text{coarse Ottawa sand}>\text{coarse field sand}>\text{medium field sand}>\text{fine Ottawa sand}$. Filtration theory and the advective-dispersion equation with reaction were applied and able to reasonably capture the transport behavior of NIPs and LMNIPs in the sand columns.

Proper design of joints in buried gravity flow pipelines should account for the demands generated in these elements when the system is subjected to surface loading. However, the behavior of joints under these loading conditions has received scant attention despite the fact that joint failure could cause the system to reach serviceability or strength limits because of leakage and soil erosion. The purpose of this study is to examine the response of band joints in corrugated steel pipes when subjected to surface vehicle loading and to examine the influence of burial quality, burial depth, and loading location on the joint response. To achieve this, large-scale laboratory testing of two 900-mm-diameter corrugated steel pipelines was performed, subjecting the specimens to the maximum service load (multiple configurations) and to the fully factored load (one configuration) while monitoring their response. The data obtained permit the key structural demands generated at the joint during surface loading to be identified and an observation of the failure mode. Recommendations are also made regarding the development of soil-pipe interaction analysis for use in structural design.

Soil reinforcement by vertical rigid piles is a suitable technique to solve soft-soil foundation problems. This technique consists of transferring the load of a pile-supported structure to a resistant, less compressible soil layer. The loads are transferred on pile heads by arching mechanisms in an earth-platform located between piles and structure. The role of the earth-platform is to distribute the loads among the piles and to minimize the fraction of the load applied on the soft compressible soil. Centrifuge tests are performed at $12\hspace{0.17em}\text{and}\hspace{0.17em}20\text{×}g$ levels of acceleration with a specific apparatus containing 63 rigid piles. The behavior of a granular earth-platform with rigid pile reinforcement is studied. The granular earth-platform is simulated with Hostun sand. The physical model is widely instrumented to compare the load-transfer efficiency and the surface settlements for several geometrical configurations. The influence of the height of the earth-platform and the spacing between the piles on load-transfer mechanisms are discussed as well as the effect of a cyclic loading. In this study, the low-height earth-platform is investigated to simulate extreme geometrical conditions. These low-height earth-platforms are suitable for low compressible soils, and in some cases a concrete slab is used above this platform.

A high-density polyethylene (HDPE) geogrid soil-reinforced dry-cast concrete block retaining wall 6.3-m high was designed using the $K$-stiffness method as part of a highway-widening project southeast of Seattle, Washington. The amount of reinforcement needed for the original wall design using the $K$-stiffness method was approximately 50% of that required using the AASHTO simplified method. This paper describes the construction, instrumentation program, and interpretation of the measurements. Geogrid strains were measured using strain gauges and extensometers attached to reinforcement layers. An extensive materials testing program was conducted to characterize the backfill soil properties and geogrid stiffness properties and to calibrate strain gauge readings. The reinforcement loads deduced from the measured strains are compared with Class A, B, and C1 predictions using the AASHTO simplified and $K$-stiffness methods. These comparisons demonstrate that the simplified method significantly overestimated reinforcement loads, whereas the $K$-stiffness method provided estimates that were consistent with the measured results. This paper describes lessons learned, the influence of construction activities on wall performance, and the limitations of both methods in estimating connections loads.

This study addresses the effects of anisotropic consolidation on sand behavior by comparing the detailed response of undrained torsional shearing of two sands isotropically and anisotropically consolidated to a range of consolidation stresses and relative densities. Anisotropic consolidation does not appear to alter the mobilized angle of shearing resistance at failure and phase transformation during torsional loading. However, anisotropic consolidation greatly affects the response of the two sands; flow deformation was observed for anisotropically consolidated loose specimens in contrast with limited flow deformation exhibited by their isotropically consolidated counterparts. For the specimens exhibiting brittleness, the instability line is well defined for both isotropically and anisotropically consolidated specimens and it appears to have the same slope in a Mohr-Coulomb diagram independent of the consolidation path followed. However, differences are observed in the peak strength, strength at phase transformation, and peak stress ratio. A stress level dependency of the stress paths and stress-strain curves is observed for both sands, which is exacerbated at higher consolidation stress levels for anisotropically consolidated specimens. Finally, the stiffness variation for both isotropically and anisotropically consolidated specimens over a range of strains is presented herein.

During penetrating of a drag anchor in seabed soils, complex interaction happens between the anchor and installation line. It is important to clarify the properties of the drag force and drag angle at the shackle of the anchor, which are especially meaningful to the design and theoretical analysis of drag anchors. The interactional properties between the drag anchor and installation line are theoretically and experimentally investigated in the present work. Based on mechanical models for the embedded line and drag anchor, analytical expressions that can predict the drag force at the shackle for both cohesive and noncohesive soils are derived. Theoretical methods are also developed to predict not only the evolution but also the exact value of the drag angle at the shackle during anchor penetration. All the analytical methods are examined by comparing the predicted drag force and drag angle with available experimental data. A detailed parametric analysis is also performed to explore the effects of different parameters on the drag force and drag angle and to determine reasonable values of several key parameters, including the lateral soil pressure factor $K$, the angle of interface friction $\delta$, and the bearing capacity factor $N_q$.

Under the same stress state, a soil behaves differently when it follows drying and wetting processes because of hysteresis. The purpose of this study was to understand the shear strength characteristics of unsaturated soil under multiple cycles of drying and wetting. A series of unsaturated consolidated drained (CD) triaxial tests were conducted using three different sand-kaolin mixtures. All sand-kaolin mixtures experienced hysteresis during multiple cycles of drying and wetting processes. The CD test results indicated that the specimens on the drying paths have higher shear strengths than those on the wetting paths owing to the hysteresis effects on the soil during drying and wetting processes. The differences between the shear strengths on the drying and wetting paths of the first cycle were found to be more significant than the differences between the shear strengths on the drying and wetting paths of the subsequent cycles. The specimens on the first-cycle wetting path and the subsequent cycles of drying and wetting paths had similar shearing characteristics; generally, they had lower axial strain at failure and exhibited less ductility, more stiffness, and dilative behavior during shearing compared to the specimens on the first-cycle drying path. In addition, the predictions of the drying and wetting shear strengths of different sand-kaolin mixtures as computed from the shear strength equation showed good agreement with the measured data obtained in this study.

An interesting phenomenon, designated as an apparent creep of saturated sand, is described on the basis of experimental data obtained from triaxial quasi-drained-controlled tests. In such tests, external stresses were kept constant while the pore pressure was cyclically changed (intrinsic cyclic loading). It is a kind of cyclic loading that takes place in seabeds, where the pore pressure changes cyclically because of the action of water waves. During the experiment, both vertical and horizontal strains were recorded. It is shown that these strains gradually increase as functions of the number of loading cycles in such a way that the volume of the specimen is constant, and only the deviatoric strain increases. The experimental curve resembles the creep curve for solid materials, in which real time is replaced by the number of loading cycles. The experiments are described and discussed, and a simple model of the phenomenon observed is proposed.