Journal of Geotechnical and Geoenvironmental Engineering

This paper reports on the behavior of a grouted anchor instrumented with a fiber optic strain sensor in the grout body along the entire anchor length. During load tests up to the estimated pull-out capacity, the strain measurements indicate that a delamination occurs in the tendon bond length between the steel tendons and the grout body. The upper delaminated part of the grout body is under compression, whereas the lower bonded part of the grout body is under tension. This delamination gradually progresses as the anchor load increases. Furthermore, a significant part of the load is transferred from the anchor to the soil in the tendon free length. The anchor behavior is further modeled with a one-dimensional finite-element model that includes the steel tendons and the grout body, where an interface damage model is used to account for possible delamination of the interface. The numerical model confirms that the observed compressive and tensile strains in the grout can be related to a delamination of the steel strands in the tendon bond length. The experiment and numerical modeling demonstrate how optical fiber measurements in the grout body can be used, in operational conditions, to assess the anchor behavior, the mobilization of the soil resistance, and the estimation of the remaining anchor capacity.

A generalized methodology for evaluating the yield stress (${\sigma }_{\mathrm{p}}^{\prime }$) of soils from cone penetration tests (CPT) is presented in terms of net cone resistance (${\mathrm{q}}_{\mathrm{net}}={\mathrm{q}}_{\mathrm{t}}-{\sigma }_{\mathrm{vo}}$) and material index, ${\mathrm{I}}_{\mathrm{c}}$. The initial baseline expression is derived from a hybrid analytical solution combining spherical cavity expansion theory and critical state soils mechanics (SCE-CSSM) that gives a first-order estimate: ${\sigma }_{\mathrm{p}}^{\prime }=0.33{\mathrm{q}}_{\mathrm{net}}$ for intact clays. A commonality is found with an algorithm derived from statistical regression analysis for CPT data from calibration chamber tests on clean quartz-silica sands that gives the approximation: ${\sigma }_{\mathrm{p}}^{\prime }=0.33{\mathrm{q}}_{\mathrm{net}}^{0.72}$. A worldwide database of 93 field sites covering a wide diversity of geomaterials including clays, silts, sands, and mixed soil types was compiled to formulate a general relationship of the form: ${\sigma }_{\mathrm{p}}^{\prime }=0.33{\mathrm{q}}_{\mathrm{net}}^{{\mathrm{m}}^{\prime }}$. The exponent ${\mathrm{m}}^{\prime }$ decreases with mean grain size (${\mathrm{D}}_{50}$) and increases with both fines content (FC) and CPT material index (${\mathrm{I}}_{\mathrm{c}}$), specifically for uncemented, insensitive, and inorganic soils. Several case studies are presented to illustrate the application of the method to several well-documented sites.

Rectangular closed diaphragm walls (RCDWs) are often used as bridge foundations because of their advantageous properties such as high stiffness and construction efficiency, low cost, and minimal vibration and noise. However, there is currently a poor understanding of the seismic behavior of RCDWs used as bridge foundations in a liquefiable deposit, and this has limited the practical application of the same. This paper presents the results of three dynamic centrifuge tests that were conducted to investigate the seismic behavior and liquefaction mitigation capacities of RCDWs with one and two chambers in a gently sloping liquefiable deposit. Specific consideration was given to the performance effects of two integral parts of the RCDW foundation, namely, the RCDW frame and cap. The test results showed that an RCDW foundation was effective for mitigating liquefaction in the soil core. The RCDW frame mitigated the liquefaction by restraining the development of the shear strain and changing the distribution of the excess pore pressure in the soil core through its very high stiffness. The presence of the cap likewise altered the dissipation mode of the excess pore pressure in the soil core by inhibiting outflow and providing additional vertical stress on the soil core. The displacement mode of the multichamber RCDW foundation was also changed by the chamber effect. The results of the present study contribute to a better understanding of this emerging type of bridge foundation and promise to facilitate its practical application.

Shear-induced seismic slope displacement is estimated for earth structures or natural slopes due to shallow crustal earthquakes along active plate margins. The proposed procedure utilizes 6,711 two-component horizontal ground motion recordings from the updated NGA-West2 database to better capture this key source of uncertainty in assessing seismic performance. The fully coupled, nonlinear seismic slope displacement model captures the important influence of the system’s yield coefficient $k_y$, its initial fundamental period $T_s$, the ground motion’s spectral acceleration at a degraded period of the slope taken as $1.3T_s$, earthquake magnitude as a proxy for duration, and peak ground velocity and fault-normal effects for near-fault pulse motions. The procedure provides seismic slope displacement estimates consistent with observations from field case histories. A procedure for selecting the seismic coefficient used in pseudostatic slope stability analyses that is consistent with an allowable seismic displacement threshold is also presented. These procedures can be implemented rigorously within a probabilistic framework or used deterministically to evaluate the shear-induced component of seismic slope displacement.

Modernization of motorway infrastructure often involves widening of existing bridges which need to be retrofitted to sustain the increased loads. Whereas pier retrofit is relatively straightforward, pile group strengthening can be a challenging, costly, and time-consuming operation. Such major operation can be avoided by taking advantage of nonlinear foundation response. Within this context, the paper presents a comparative assessment of current practice, based on elastic foundation design, and of an alternative design approach that allows nonlinear foundation response. This allows for the exceedance of the conventionally defined (elastic) moment capacity of the foundation through load redistribution between piles during seismic shaking. Inspired by the widening of a Swiss bridge, a numerical study is conducted employing three-dimensional (3D) finite-element (FE) modeling. The analysis compares the widened bridge with retrofitted versus unretrofitted foundation. For moderate design-level seismic shaking, the performance is almost identical. For stronger shaking substantially exceeding the design limits, the unretrofitted foundation is advantageous because it reduces structural damage by dissipating energy through soil yielding, at the cost of increased—but totally tolerable—settlement.

This study explored a suitable technique of reducing pore-water pressures and deformations in poorly draining soil slopes subjected to rainfall. The reinforcing function of woven geogrid was coupled with the drainage property of nonwoven geotextile in the form of a hybrid geosynthetic material. A series of centrifuge tests was conducted with an in-flight rainfall simulator on silty-sand slopes representing 7.2 m height and $2\mathrm{V}:1\mathrm{H}$ inclination at $30\mathit{g}$ using the 4.5-m-radius beam centrifuge at the Indian Institute of Technology (IIT) Bombay, India. The surface settlements, displacement contours, strains experienced by geosynthetics, and pore-water pressures developed during a heavy rainfall event of $20\mathrm{mm}/\mathrm{h}$ were investigated. The unreinforced slope underwent toe failure with rainwater infiltration due to absence of either drainage or reinforcing elements. The geogrid-reinforced slopes experienced considerable deformations and increasing phreatic levels with rainfall due to insufficient drainage, accompanied by geogrid straining in the range of 38%–48%. Although the increase in phreatic levels decreased substantially in the geotextile-reinforced slope, an eventual slope failure was induced by rainfall due to inadequate reinforcement. In comparison, the crest settlements and slope face movements were 86% and 82% lower, respectively, in the hybrid geosynthetic–reinforced slopes, and phreatic levels at the slope base decreased 40%. Moreover, negligible peak strains on the order of 3%–8% were registered along hybrid geosynthetics throughout the rainfall event. A seepage-stability analysis was further conducted to investigate the reinforcing effects of geogrids, geotextiles, and hybrid geosynthetics separately in controlling the slope factor of safety with rainfall.

This study investigates the thermal and thermomechanical behavior of two energy piles with either double U-loop or spiral loop heat exchanger configurations. The piles were installed in a sandstone formation, and a heating-recovery-cooling-recovery cycle was applied to the piles. In both piles, the shaft resistance evaluated from the measured axial-strain distributions was greater in the heating mode than that in the cooling mode. In the heating model, radial expansion was detected. The radial stress at the pile–soil interface increased due to the high stiffness of the sandstone, which in turn increased the shaft friction. In the cooling stage, the radial contraction of the pile was measured, which in turn decreased the radial stress at the pile–soil interface. The amount of pile contraction was similar to the thermally induced free contraction, and consequently large pile settlement was measured at the top of the pile during cooling. The normalized heat-transfer rate shows similar thermal efficiency between heating and cooling, indicating the heat transfer was not much affected by the radial expansion and contract of the piles.

For conventional assessment of the bearing capacity of shallow foundations on level ground, dimensionless bearing capacity factors are used to establish the contribution of footing size, footing embedment, and soil shear strength. This study presents the derivation of an analytical approach toward evaluating the bearing capacity of shallow foundations influenced by the presence of a slope. The results are presented as dimensionless bearing capacity factors ($N_{cs}$, $N_{\gamma s}$, and $N_{qs}$) enabling consideration of the contribution of cohesion, soil weight, and embedment in the calculation of bearing capacity near slopes. The analytical nature of the work provides insight into the influence of the critical kinematically-admissible failure mechanism—either a slope stability or bearing capacity mechanism categorized as a face failure, toe failure, base failure, or crest failure. A set of design charts are provided for ease of application within the conventional bearing capacity formulation.

This study aims to examine the use of the discrete-element method (DEM) for prototype-scale analyses of large discontinuous deformations. As an example, this paper presents the results of large-scale modeling of a mobility cone penetration test using DEM. The analysis demonstrates the potential for very-large-scale fully three-dimensional discrete-element computations for simulation of uniquely difficult geotechnical problems involving discontinuous deformation such as cone penetration, plowing, and slope stability. The particle-scale resolution was achieved using several million particles as a straightforward application of high-performance computing with message-passing interface (HPC-MPI) techniques. The use of the discrete-element method for micromechanical studies versus prototype-scale engineering studies are discussed in detail. The former involves accurately depicting details such as particle size distribution and particle shape; the latter uses the computational particles, similar to finite elements, where characteristics of the particles are simplified to gain computational efficiency. The DEM inherently captures qualitative constitutive soil behavior; calibration procedures are directed at achieving accurate quantitative behavior. A key issue is defining the soil’s consolidation state because porosity cannot be specified as a material parameter but depends on particle placement and compaction. In addition to cone simulations in the near-surface environment, deep penetration simulations were used to examine the effect of confining stress on volume change. The cone tended to increase porosity at all stress levels, although the increase was significantly subdued by higher stress levels. The particle stress is presented in various formats to illustrate how cone resistance is developed.

The research focus of this paper is directed to investigate the behavior of a single model pile and pile groups in sand under both saturated and unsaturated conditions. Forty different model tests were performed on single piles and pile groups by varying the water-table level. Influence of matric suction, roughness of soil–shaft interface, dilation, and group action were investigated. Test results suggest that the ultimate load-carrying capacity of a single pile and pile groups increased by twofold to 2.5-fold, and settlements decreased significantly due to the matric suction’s contribution in comparison with saturated conditions. Erroneous results are likely if conventional soil-mechanics principles are extended in the estimation of pile group capacity and the group efficiency factor for unsaturated cohesionless soils. These errors can be attributed to neglecting the cumulative influence of matric suction and stress overlap in pile group behavior of sandy soils. This study highlights the need for rigorous interpretation of pile load test results taking account of the influence of matric suction when evaluating pile group capacity and group efficiency factor in engineering practice for unsaturated sandy soils.

This paper presents the first full-scale demonstration of the potential use of pipe–soil interaction-generated acoustic emission (AE) for early detection of buried pipe deformation. Full-scale tests were performed at the buried infrastructure research facility at Queen’s University, Canada, using a split box apparatus to impose differential ground motion on a steel pipe buried in dry sand, and to investigate the influence of stress level and patterns of deformation on AE generation. The pipe was instrumented with AE sensors, strain gauges, fiber optic strain sensing, and linear potentiometers, and surface deformation was measured using an automatic total station. AE measurements were used to interpret the evolution of the pipe–soil interaction behavior. AE activity correlated strongly ($R^2$ from 0.83 to 0.99) with both the rate and magnitude of pipe deformation at different burial depths, and quantified relationships are presented that enable interpretation of pipe–soil interaction behavior from AE measurements.

Soil arching exists in many geotechnical applications, including tunnels, buried pipes, and geosynthetic-reinforced pile-supported (GRPS) embankments. Soil arching has been mostly investigated using trapdoor tests under soil self-weight and/or uniform surcharge. In real applications, localized surface loading, such as traffic loading, may be applied onto soil and affect or degrade soil arching. Geosynthetic reinforcement is used in GRPS embankments or over buried pipes and may have effects on soil arching mobilization and degradation under localized surface loading. The effects of surface traffic loading and geosynthetic reinforcement on soil arching have not yet been well investigated. This study investigated the effects of static surface footing loading on soil arching mobilization and degradation in geosynthetic-reinforced and unreinforced embankments using trapdoor model tests under a plane-strain condition. These model tests consisted of both trapdoor and loading stages, which were used to evaluate the mobilization and the degradation of soil arching, respectively. The trapdoor test results show that the displacement of the trapdoor induced progressive mobilization of soil arching and geosynthetic reinforcement minimized soil arching mobilization due to the change of the soil deformation. Localized surface loading degraded soil arching. Single and double layers of geosynthetic reinforcement helped maintain soil arching under localized surface loading. The test results also show that the biaxial geogrid was more effective than the uniaxial geogrid with similar tensile strength and stiffness in carrying the load due to its better lateral restraint. Geosynthetic reinforcement increased the applied surface load required to fully degrade soil arching and eliminate the benefit of the geosynthetic.

This paper presents, evaluates, and discusses experimental results of soil–reinforcement interaction tests conducted using a new device developed to assess the mechanical interaction between soil and reinforcement considering varying reinforcement vertical spacings. The experiments involved testing a geosynthetic-reinforced soil mass with three reinforcement layers: one was actively tensioned and the two neighboring layers were passive. Shear stresses from the actively tensioned reinforcement were conveyed to the passive reinforcement layers through the intermediate soil medium. Soil-reinforcement interaction tests were conducted with varying reinforcement vertical spacings and normal stresses. The load conveyed to the neighboring reinforcement layers was found to increase with increasing load in the actively tensioned reinforcement layer. The magnitude of load transfer was found to increase with decreasing vertical spacing, while the normal stress was determined to have a negligible effect on the magnitude of load transfer for the case of active loads representative of working stress conditions. However, since the soil–reinforcement interface strength decreases with decreasing normal stress, the magnitude of load transfer was observed to decrease with decreasing normal stresses for comparatively large active loads.

Soil–water retention curve (SWRC) is a constitutive relation indispensable for analysis of fluid flow and moisture and stress distributions in unsaturated soils. Although the SWRC is traditionally formulated in the regime of positive matric suction, it is also relevant in the negative matric suction regime where pore water are pressurized. To date, no mathematical model is available for characterization of SWRC in both the positive and negative matric suction regimes. In this paper, the underlying mechanism for hydraulic hysteresis is analyzed especially in the regime of negative matric suction, and a novel SWRC scanning hysteresis model is developed for both the positive and negative matric suctions. To demonstrate the performance of the proposed model, the simulated results are compared with experimental data available in the literature, indicating that the new model can describe well the hydraulic hysteresis of unsaturated soils. The proposed model introduces only one parameter in order to describe the scanning hydraulic behavior and is general in the sense that the model can describe well the soil–water retention characteristics in both the positive and negative matric suction regimes.

Buried lined-corrugated high density polyethylene (HDPE) pipes have been applied to transport sewage for decades. During its service life, a pipe of this kind could suffer from differential ground motion as a result of various geohazards (e.g., differential settlement induced by tunneling, basement excavations, changes in water table). However, studies of this kind of behavior of thermoplastic sewers have largely been absent in the pipe research literature. A full-scale test was conducted to investigate the structural response of 600-mm diameter lined-corrugated HDPE pipe subjected to differential ground movements associated with a normal fault having dip angle of 90°. This normal fault was simulated in a facility called the Split Box, where half of the floor of the test pit rests on screw jacks that allow it to be lowered in a stepwise process. Strain gauges and optical fibers were used to measure strains in the longitudinal and circumferential directions on the inner or outer surfaces of the pipe. Vertical displacement and cross-section distortion of the pipe were monitored using digital images analyzed using particle image velocimetry (PIV). Test results show that pipe strains were distributed nonlinearly around the pipe cross sections, especially for those measured proximal to the fault. Maximum pipe diameter changes were also observed at pipe cross sections close to the fault. The test results were compared with two current calculation approaches (i.e., the three-beam method and the Kappa method) and it is found that these two methods both overestimated peak bending strains in the pipe relative to those observed in the test.

The effect of vibratory compaction on a sandy deposit was investigated using different types of in situ methods. An important objective was to determine the change in soil resistance and horizontal stress at different time intervals after compaction. The horizontal stress, measured by different in situ methods, showed a significant and permanent increase due to vibratory compaction. The overconsolidation ratio of compacted sand was estimated based on the increase in horizontal stress using different methods. The tangent modulus method is shown to be a powerful concept for evaluating the settlement of compacted soil by considering the increase in soil stiffness (modulus number) and overconsolidation. The modulus number derived from in situ tests was compared with data reported in the literature.

The Caminada Headlands is a beach and dune system that provides natural protection for back barrier marshes against storm surges and wave overtopping. Due to significant shoreline erosion and regional subsidence, a beach and dune restoration project was initiated in 2012 to replenish the shoreline front. Because of the underlying soft deltaic sediments, this restoration effort was expected to cause significant sediment settlement due to the increased stresses applied by the replenishment. To quantify the degree of settlement occurring within the compressive sediment layers and the fill, extensive geotechnical investigations were conducted in addition to the installation of settlement plates and subsurface settlement anchors. This paper presents the inverse settlement analyses using ${\mathrm{SETTLE}}^{\mathrm{3D}}$ and Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill (PSDDF) programs, which are based on Terzaghi small strain and finite strain theories, respectively. The model predictions show both software can replicate field settlement measurements, which are subsequently used to predict the end of primary consolidation for the Caminada Headlands and validate empirical correlations in the companion paper. Guidelines are also provided on conducting settlement and consolidation analyses to facilitate design of future coastal restoration and protection projects.