Journal of Geotechnical and Geoenvironmental Engineering

Changes in geosynthetic clay liner (GCL) properties over time are examined for the case in which the GCL (1) rests directly on a ${\mathrm{Ca}}^{++}$ rich soil ($1,700–1,800\mathrm{mg}/\mathrm{l}$ ${\mathrm{Ca}}^{++}$) and (2) a 30 cm foundation soil ($200–300\mathrm{mg}/\mathrm{l}$ ${\mathrm{Ca}}^{++}$) overlying the ${\mathrm{Ca}}^{++}$ rich soil. Results for a control case in which the GCL rested only on the foundation soil are also reported. The moisture content increased to 108% and then remained constant in the control case. The moisture and calcium uptake from the underlying soil caused the moisture content of GCL to increase to 96 and 86% in the first 279 days of the experiment for the cases with and without foundation soil, respectively. The moisture content then decreased to 80 and 67% after 1,100 days under isothermal condition with and without the foundation layer, respectively. After 1,100 days (three years), the hydraulic conductivity of the GCL increased (attributable to cation exchange) from approximately $3\times {10}^{-11}\mathrm{m}/\mathrm{s}$ initially to approximately $7\times {10}^{-11}$ and $2\times {10}^{-10}\mathrm{m}/\mathrm{s}$ with and without the foundation layer. Changes in swell index (SI) and exchangeable cations were measured and correlated to changes in hydraulic conductivity.

Estimation of the pulling forces during installation is an important step in the successful design of a horizontal directional drilling project. Moreover, estimation of the postinstallation loads is important for the prediction of the long-term performance of the installed pipe. An algorithm is developed to calculate the short and long-term response of steel (elastic) and polymeric (viscoelastic and viscoplastic) pipes installed using horizontal directional drilling. The program simulates the movement of the pulling head, calculates the installation loads, and employs nonlinear, time-dependent constitutive models to calculate the polyethylene pipe response. The program is evaluated by comparing its calculations with known solutions, as well as with other commonly used load estimation methods. After evaluation, the analysis is used to analyze a typical horizontal directional drilling installation. It is shown that the pipe experiences cyclic response during installation and a combination of creep and stress relaxation in the long-term.

This paper presents a simplified approach for reliability analysis of basal heave in a braced excavation considering the spatial variability of soil parameters, The first-order reliability method (FORM) with a variance reduction technique is employed to model the spatial variability in lieu of the conventional random field modeling (RFM). The proposed approach yields results that are comparable with those obtained using the conventional RFM approach that relies on Monte Carlo simulation. The proposed approach requires much less computational effort, is easy to use, and has potential as a practical tool for reliability-based design that has to deal with spatial variability of soils.

The common design approach of compaction grouting for ground improvement works is oversimplified and does not account for the effects of soil properties and grouting variables. The obtained improvements therefore appear inconsistent with the predicted ones. This paper presents the results of a field test conducted at Tokyo International Airport to evaluate the effectiveness of compaction grouting under well-controlled conditions. The test consisted of 87 compaction grout piles injected in three cases of different pile diameters and spacings. The paper also discusses the effects of soil properties, replacement ratio, and injection sequence on the effectiveness that is evaluated in terms of the standard penetration test $N$-value and cone penetration test tip resistance, and the variation of effectiveness with depth. A new design procedure that accounts for the effects of initial soil properties is introduced. It has been found that the injection sequence has a significant effect on the grouting mechanisms and effectiveness; this effect is discussed for both high and low compressibility soils. Significant observations are also made on relatively shallow treatments, the associated ground surface heave, and the corresponding improvement.

Large deflection is mobilized in elevated piles of nonnavigable piers and some flexible protective systems subjected to lateral ship collisions. Because the current bridge design specifications are only suitable for the design of rigid foundations, new analysis and design methods are required for these flexible elevated piles. A large-scale lateral static load test and an additional three impact tests on piles in low liquid limit silt (ML) soil were carried out in a large soil tank. Both static and dynamic soil pressures on the pile shaft were measured, and then the soil-pile interaction was studied in detail. Based on the results, static hyperbolic $p\mathrm{\text{-}}y$ curves of the piles were derived for dynamic $p\mathrm{\text{-}}y$ curve models. Through investigations of three linear and nonlinear soil-pile dynamic interaction models, the dynamic $p\mathrm{\text{-}}y$ curve models with nonlinear static stiffness coefficients and constant damping coefficients are recommended for the analysis of piles subjected to lateral impact loading. Verified by three impact tests with different impact energies, a dynamic collision analysis model involving the dynamic $p\mathrm{\text{-}}y$ curve model is presented for the analysis of collisions between ships and elevated piles.

The addition of liquids to municipal solid waste landfills, a practice sometimes performed under pressure to promote moisture distribution, has the potential to affect slope stability as a result of increased pore water pressure (and reduced shear strength) in the landfilled waste. Liquids addition into waste by using buried horizontal trenches was modeled to determine pore water pressure distributions, and the resulting effect on slope stability was assessed for different operational strategies. Model results using typical mechanical properties for solid waste found that pressurized liquids addition under a sloped landfill surface was possible without inducing a slope failure, providing liquids distribution was not obstructed. A reduction in the factor of safety occurred when simulating a poorly functioning leachate collection and removal system, a low-permeability cover layer within the landfill, a seepage control strategy using low-permeability soil, high liquids addition pressures, and waste permeability decreasing with depth. The sensitivity of the model results to input parameters was evaluated and graphically presented. The results demonstrate how pressurized liquids addition has the potential to affect slope stability and provide important insights for engineers charged with designing and permitting such systems.

A capillary barrier as a cover system is a two-layer system of distinct hydraulic properties to prevent water infiltration into the underlying soil by utilizing unsaturated soil mechanics principles. This paper illustrates the application of the capillary barrier system on a slope that experienced shallow slip failures to prevent future rainfall-induced slope failures. In this study, the capillary barrier system was designed as a cover system for residual soil slopes with a steep slope angle under heavy rainfall conditions of the tropics. The capillary barrier system was constructed using fine sand as the fine-grained layer and granite chips as the coarse-grained layer. Both layers were contained in a cellular confinement system. The slope was instrumented with tensiometers and piezometers. The tensiometers were installed at different depths from about 0.5 m to 2.0 m below the slope surface. An adjacent original slope without the capillary barrier system was also instrumented using tensiometers to investigate the performance and effectiveness of the capillary barrier system in reducing rainwater infiltration and maintaining negative pore-water pressure in the slope. The detailed installation of a matric suction measurement device is discussed comprehensively in this paper. The measurement results showed that the capillary barrier system was effective in maintaining the negative pore-water pressures during rainfalls, particularly on the crest of the slope.

A simple method to predict the uplift displacement of a manhole and trench-backfill settlement due to liquefaction is proposed. The conventional equilibrium of vertical forces acting on a manhole is solely a function of such forces acting and is incapable of predicting the uplift displacement. In this paper, the proposed method adds variables including the uplift displacement, $\Delta f$, and settlements of backfill, $\Delta s$, under the condition that the volume of an uplifted portion of a manhole is equal to a settled volume of a trench-backfill. To date, the method is verified through comparison with the results of 1-G and centrifuge model tests. A new safety factor, which takes into account the amount of manhole uplift and backfill settlement, is also derived.

During the past few decades, soil nailing has been widely used for stabilizing slopes and excavations. The nail-soil interface shear resistance in the passive zone of a slope or excavation is a critical parameter in design. In this paper, an analytical study is proposed to investigate the progressive pullout response of a soil nail. Pullout process is divided into three typical phases: (1) the initial pure elastic phase during which the nail-soil interface follows a linear elastic stress-displacement relationship; (2) the elastic-plastic phase during which a transition point presents dividing the elastic and plastic zones; and (3) the final pure plastic phase. A comparison study between calculations and laboratory test data are presented to examine the effectiveness of the method. In addition, a comprehensive parametric study is performed to assess the effects of several key factors on the pullout resistance of a soil nail. These factors include the length and diameter, length of plastic zone, and the elastic modulus of a soil nail. Main research findings are presented and discussed to gain a better understanding of the progressive interaction between soil and soil nail.

A class of granular materials is presented that was obtained from quarried intrusive igneous rock, further processed to match the grain-size distribution of typical Apollo samples. Texture, mineralogy, and chemical composition have been investigated; and the material is classified as basaltic andesite. A series of triaxial compression tests have been performed to assess the influence of confining stress on the shearing behavior at medium to low stress levels. A medium sand is used as reference. In one of the test series, corundum was added to simulate the glass particles found in the lunar regolith. Both stress-strain curves and volumetric strains are reported. All samples tested exhibit a purely dilatant behavior at low confining stress levels. Shear strength can be expressed either by a curved Mohr-Coulomb envelope or by a linear one with a cohesion intercept. Results are shown to agree well with those obtained on common lunar soil simulants.

The static behavior of Mississippi River Valley silt was characterized using triaxial compression testing. Silt specimens, especially overconsolidated ones, showed dilation behavior. There was no unique critical state among specimens with different overconsolidation ratios (OCRs). With OCRs of 1, 2, and 8, the specimens exhibited normal behavior and dilated more as effective consolidation pressure dropped. However, for an OCR of 4, the specimens showed opposite behavior and dilated more as effective consolidation pressure rose. The friction angle of the silt was computed on the basis of several failure criteria, and the limiting strain was found to be the best one owing to better consistency and rational results of the friction angle. The silt showed a unique behavior compared with sand and clay: The critical state line was not parallel to the normal consolidation curve in the $e\mathrm{\text{-}}ln{p}^{\prime }$ space; the stress-strain behavior can be normalized by effective consolidation pressure. The normalized shear strength of overconsolidated specimens was correlated to that of a normally consolidated specimen using Ladd et al.’s equation with an $m$ value of 0.58 for low-plasticity silts. However, the normalized shear strength of overconsolidated silts cannot be related to OCR directly. It was indicated that at least the normalized shear strength of a normally consolidated specimen needs to be tested for low-plasticity silts to obtain the normalized shear strength of overconsolidated specimen using Ladd et al.’s equation.

The results of experimental studies on the stress-strain behavior of Chicago glacial clays are presented and discussed. This paper describes small strain responses as a function of stress path rotation angle. Undrained compression and extension tests with three different preshear stress paths were conducted on high quality, hand-cut block samples obtained at two different depths from the excavation for the Block 37 project in Chicago. One preshear stress path was applied to investigate the stress-strain response representative of the in situ conditions via a recompression technique. The other two preshear stress paths were selected to isolate the effects of recent stress history such that the only difference between the two sets of paths was the direction of loading to a common effective stress condition. A period of drained creep at constant effective stress was imposed on all specimens prior to shearing to negate the possible effects of creep on the small strain responses. The results are discussed in terms of secant shear modulus, shear strain, and stress path rotation angle. The results of experiments show that recent stress history affects the small strain behavior of compressible Chicago clays.

Original laboratory setups are used to study the moisture retention properties of municipal solid waste taking into account the porous medium’s structural evolution from compression. A controlled suction oedometer allowed the moisture retention curves (MRCs) of compacted samples to be determined for both wetting and drainage with a matric suction range of 0 to 10 kPa. Another setup utilizing an extraction plate was used to determine a drainage MRC for a noncompacted sample with matric suction varying from 0 to 450 kPa. The experimental results demonstrated the complexity of municipal solid waste (MSW) porous medium compared to soil. The MRC of lightly and uncompacted samples did not exhibit a measurable air-entry suction. Moreover, significant hysteresis between the wetting and drainage MRCs was observed. The experimental MRCs were interpreted with two different models, and a pore size distribution evolution with compression was proposed. Finally, the concept of field capacity in relation to the moisture retention properties is discussed.

This paper describes an interesting slope failure in a liner system of a municipal solid waste containment facility during construction because the sliding interface is not the geomembrane (GM)/compacted low-permeability soil liner (LPSL) but a soil–soil interface within the LPSL. Some of the lessons learned are as follows: (1) compaction of the LPSL should ensure that each lift is kneaded into the lower lift so a weak interface is not created in the LPSL; (2) the LPSL moisture content should be controlled so it does not exceed the specified value, for example 3–4% wet of optimum, because it can lead to a weak interface in the LPSL; (3) drainage material should be placed over the GM from the slope toe to the top to reduce the shear stresses applied to the weakest interface; and (4) equipment should not move laterally across the slope if it is unsupported but up the slope while placing the cover soil from bottom to top.

This paper describes a full-scale experiment of pile-supported embankments on soft soil, which is conducted within the French national research project, Amélioration des Sols par Inclusions RIgides (ASIRI), to provide a new design method. This experiment shows the great influence of a granular platform reinforced with geosynthetics in load-transfer mechanisms. The measurements of geosynthetic strains highlight that the maximum strain takes place at the vicinity of pile heads during the construction of an embankment. Measurements also show that the load-transfer behavior of a platform reinforced by a single geotextile is different from that of a platform reinforced by two geogrids, although the final settlement is the same in both sections. From the important measurement data of this full-scale experiment, some considerations on the design and the efficiency evaluation have been proposed.