Journal of Geotechnical and Geoenvironmental Engineering

Data from 58 high-quality liquefaction case histories from the Darfield and Christchurch earthquakes are utilized to investigate the efficacy of current liquefaction aging correction procedures. Toward this end, liquefaction case histories are analyzed in which aging corrections are and are not applied, and the resulting predictions are compared to the actual liquefaction response of the deposits. An error-index is calculated to quantify the efficacy of aging corrections. While all the sites located in the Christchurch area are classified as Holocene, based on their geological age, their liquefaction response is influenced more by the geotechnical age of the soil deposits. Aging correction was determined to be beneficial for the liquefaction assessment of soils that experienced recurrent liquefaction (i.e., geotechnical young deposits). However, aging corrections were determined to exacerbate the liquefaction assessment of relatively old (greater than $\sim 62–580\text{years}$) soil deposits.

This research paper illustrates the application of a new liner leak detection technique which uses the concept of electrical resistivity to detect leakages in municipal solid waste (MSW) landfills. Liner leakage was simulated in the laboratory using the controlled leakage of landfill leachates into the soil layer beneath the liner. Resistivity testing was then conducted to evaluate the performance of this technique. Various resistivity profiles were obtained at regular time intervals to investigate the effect of leakage duration and electrode location on the resistivity of soil. The resistivity showed a sharp decrease with an increase in the leakage duration. The resistivity decreased with an increase in the proximity to the leak point. The resistivity of soil was obtained at leakage durations above 30 min for the first leachate specimen and above 130 min for the second leachate specimen. Based on the leak detection test results, new empirical correlations and analytical modeling are also presented. The technique was found to be effective in the timely detection and location of liner leakages, irrespective of the leakage duration. The use of graphical presentations, empirical correlations, and analytical expressions developed in this study can assist in actively monitoring the lining systems and taking timely action for contamination control.

In this study, a latex membrane with a diameter of 50 mm and thickness of 0.5 mm is used to encase an injection hole. The gap between the membrane and the nail rod is fixed to achieve compaction grouting and to prevent fracturing and permeating; hence, a regular grout bulb is easily formed and locked into the soil matrix to provide a pullout force for a compaction-grouted soil nail. For this type of soil nail, two series of physical model tests for an embedded soil nail and a soil nail with a predrilled hole (the soil sample was moistened and could sustain the hole without collapsing during the placement of the nail rod) were conducted to study the influence of the installation methods on the performance of a compaction-grouted soil nail. The results of the two series of tests were compared, and some conclusions were drawn: First, the aforementioned installation methods for a soil nail had little impact on the mass of injected grout, whereas the shape of the cured grout bulb showed some differences based on the type of soil response. Second, compared with that of an embedded soil nail, the pullout force of a postplaced soil nail remarkably decreased because the hole drilled for installation led to a gap between the soil nail and the surrounding soil. In addition, the loss rate correlated with the grouting pressure (i.e., the diameter of the grout bulb). Third, because of the lower soil densification, dilation, and squeeze effect, a slower growth rate (with increasing grouting pressure) of the pullout force (i.e., resistance) was found for the postplaced soil nail relative to that of the embedded soil nail, during which the efficiency of the increasing pullout force decreased.

This paper presents a laboratory investigation of undrained triaxial shear behavior of a natural low-plasticity silt from Halden, Norway in the intact, disturbed, and reconstituted states. Sherbrooke block sample and reconstituted specimens were subjected to simulated tube sampling in a triaxial stress path cell system prior to reconsolidation and undrained shear to assess the effects of disturbance on undrained shear behavior, undrained shear strength, and effective stress friction angle. Shear stress and pore-pressure development were evaluated relative to that measured for the undisturbed reference state, i.e., that measured on specimens from the intact block sample. Specimens trimmed from fixed-piston tube samples collected from the field site were tested for comparative purposes. Collectively, the results demonstrated that neither the volumetric method of evaluating sample quality for clays nor shear wave velocity tracked sample disturbance well for this low-plasticity silt. Relative to the reference intact block sample tests, simulated tube sampling resulted in an increasingly pronounced dilative-type behavior during postdisturbance undrained shear and a general increase in undrained shear strength. Specimens from the block sample that were subjected to simulated tube sample disturbance had similar stress–strain behavior as that from conventional anisotropically consolidated triaxial compression tests conducted on specimens from the tube samples, suggesting that significant alteration of the intact soil state occurred during tube sampling. Practical suggestions for selection of undrained shear strength for intact low-plasticity silts that exhibit dilative behavior such as the Halden silt are proposed.

The objective of this study is to investigate the effects of an inclined base plate on the end bearing capacity of embedded piles and soil behavior below a pile base according to the vertical stress and inclination angle of the base plate. Two types of model piles were prepared: a conventional pile with a flat base plate with a diameter of 50 mm and piles with an inclined base plate with a diameter of 56 mm. Load tests were conducted using model piles with a diameter of 50 mm incorporated with load cells and bender elements in a calibration chamber. The end bearing capacity, unit end bearing capacity, and shear wave velocity increase for all model piles with an increase in the vertical stress and in the inclination angle. The increment in the end bearing capacity may result from the increased projected area, the increased contact area between the inclined base plate and soil, and increased horizontal effective stress. The unit end bearing capacity also demonstrates a good relationship with the shear wave velocity, which is a function of the horizontal effective stress below the pile base. This study suggests that piles with inclined base plates may be effectively used in the embedded pile method to improve the end bearing capacity.

In this study, the effect of pile surface roughness on the lateral load–carrying behavior of piles embedded in sand was investigated. Centrifuge tests were conducted on various model piles with different degrees of surface roughness. The effects of the pile surface roughness, given by the normalized roughness, $R_n$, on the lateral-load capacity and lateral displacement were analyzed. From the centrifuge tests, it was observed that the lateral-loading capacity markedly increased with the pile surface roughness. The effect was most significant within low degrees of surface roughness up to $R_n$ of 0.024. Surface roughness parameters for the $p\text{-}y$ method were proposed as a function of $R_n$, which could explain the effect of the pile surface roughness on calculated lateral load–displacement curves. Finite element analyses were performed to assess and compare the experimentally and numerically determined effects of the pile surface roughness. The numerical simulation of laterally loaded piles does not fully reproduce the experimental effect of surface roughness on the lateral-load response, which needs to be properly considered in the analysis.

Three Pleistocene-age sand deposits from 100,000 to 1.2 million years old in the South Carolina Coastal Plain were characterized with the cone penetrometer test and samples were tested in a cyclic triaxial system to determine their cyclic resistance to earthquake-induced liquefaction. The current empirical methods used for evaluation of the cyclic resistance of the soils to liquefaction are limited due to their dependence on young, Holocene-age soil deposits less than 10,000 years old. The results of this work show that the cyclic resistance ratio of the Pleistocene-age deposits is greater than that of the Holocene-age deposits using two readily available methods of analysis and considering the adjustment for fines content. The cyclic resistance ratios derived from laboratory cyclic triaxial tests that have been adjusted for field conditions and with the cone penetrometer test data indicate that the cyclic resistance ratios for the Pleistocene soils exceed the Holocene clean sand base liquefaction curves using both methods. The cyclic resistance ratios of the Holocene clean sand base curve are exceeded over a range from 0.6% to 43.3% and one of the methods indicates an age-related progression of the cyclic resistance ratio.

The critical state (CS) concept is a theoretical framework that models the constitutive behavior of soils, including sand and other granular materials. It supports the notion of a unique postfailure state, where the soil ultimately experiences continuous shearing with no change in the plastic volumetric strain. However, the published literature has frequently noted the nonconvergence of sand specimens with different initial densities to a unique CS in the compression plane due to many factors such as specimen fabric, particle morphology, breakage, and grain size distribution. This paper examines the CS for poorly graded (uniform) glass beads and 3 different types of silica sands using 50 conventional triaxial compression (CTC) experiments, 12 oedometer tests, and in situ synchrotron microcomputed tomography (SMT) scans for 10 CTC experiments. The results of the 50 CTC experiments revealed a diffused CS zone in the compression plane, which was further examined using the in situ SMT scans. A thorough three-dimensional image analysis of the SMT scans accurately quantified the evolution of the local void ratio ($e_{\mathrm{local}}$) versus axial compression within zones of intensive shearing toward the center of the specimen. The evolution of the void ratio was also measured using the entire volume of the specimen ($e_{\mathrm{global}}$). At the CS, the $e_{\mathrm{local}}/e_{\mathrm{global}}$ ratio was assessed to be $\sim 1.25$ when a single shear band developed within the scanned specimens and $\sim 1.1–1.15$ for specimens that failed via external bulging that was internally manifested by the development of multiple shear bands. This finding suggests that the CS zone in the compression plane can be attributed to the common wrong consideration of $e_{\mathrm{global}}$ evolution in lieu of $e_{\mathrm{local}}$ within the developing shear bands. Furthermore, the lack of shear band development in uniaxial compression has made the results of the oedometer test reliable in quantifying the CS parameters in the compression plane.

Dynamic load testing and signal matching is commonplace for pile capacity verification but can be subject to nonuniqueness and uncertainty. Whether this uncertainty may be reduced with additional measurements requires further study. The instrumented Becker penetration test (iBPT) configured as a reusable test pile provides direct measurements of the dynamic response at the pile base and shaft. The distribution of static shaft friction in tension also is measured. This paper examined the sensitivity and potential improvements of such measurements in signal matching techniques. Different solution procedures were devised to analyze the same impact events, but incorporating static and dynamic iBPT measurements to varying degrees. The results suggest that whereas predictions of total ultimate capacity from signal matching generally are robust, differentiation of shaft versus base capacity may be more uncertain. Despite the nonunique solutions, dynamic predictions of shaft capacity agree reasonably well with static measurements.

The operator of the Groningen gas field is leading an effort to quantify the seismic hazard and risk of the region due to induced earthquakes, including overseeing one of the most comprehensive liquefaction hazard studies performed globally to date. Due to the unique characteristics of the seismic hazard and the geologic deposits in Groningen, efforts first focused on developing relationships for a Groningen-specific liquefaction triggering model. The liquefaction hazard was then assessed using a Monte Carlo method, wherein a range of credible event scenarios were considered in computing liquefaction damage-potential hazard curves. This effort entailed the use of a regional stochastic seismic source model, ground motion prediction equation, site response model, and geologic model that were developed as part of the broader regional seismic hazard assessment. No to minor surficial liquefaction manifestations are predicted for most sites across the study area for a 2475-year return period. The only sites where moderate surficial liquefaction manifestations are predicted are in the town of Zandeweer, with only some of the sites in the town being predicted to experience this severity of liquefaction for this return period.

A laboratory modeling program has been conducted to evaluate the hydraulic conditions required for backward erosion piping (BEP) to initiate and progress in sandy soils. The first stage of BEP consists of loosening the soil near the unprotected seepage exit face from which the piping initiates. As the differential head on the system increases, the loosened zone increases in size to reach equilibrium with the increasing hydraulic gradient near the seepage exit. Laboratory models were performed on sandy soils to model the development of BEP and measure the hydraulic regime surrounding the developing loosened zones. Inverse analyses were performed using three-dimensional finite-element (FE) seepage analyses to assess the critical gradients needed to initiate soil loosening and create or expand the loosened zone. By analyzing the observed behavior and data of piping development with the inverse-analysis procedure, exponential and linear fit equations were developed to define the relationship between effective stress and the critical gradient at the boundary of the loosened zone. The exponential relationship was shown to have a moderately better fit of the data than the linear relationship, indicating that internal friction resistance in addition to overburden weight contributes to the resistance to soil loosening.

Soil-bentonite (SB) cutoff walls are commonly employed to control groundwater flow and contaminant migration, and the hydraulic conductivity ($k$) of the SB backfill is a critical parameter in these applications. In this study, an evaluation of backfill $k$ was conducted for a large-scale SB cutoff wall (approximately 200 m long and 7 m deep) constructed and instrumented for field research. Measurements of $k$ (more than 150 in total) were obtained via (1) laboratory (flexible-wall and rigid-wall) tests on specimens molded from surface grab samples of the field-mixed backfill collected during construction, (2) laboratory (flexible-wall) tests on undisturbed backfill specimens prepared from Shelby tube samples taken from the wall, and (3) in situ (slug) tests conducted at 12 different locations within the wall. The laboratory tests were conducted in stages over a range of applied effective stresses (${\sigma }^{\prime }=6.9$, 13.8, 20.7, and 34.5 kPa) that encompassed the range of mean in situ effective stresses measured in the backfill (6–12 kPa) via embedded earth pressure and pore pressure sensors. At a given ${\sigma }^{\prime }$, flexible-wall $k$ values for the undisturbed specimens were similar to those for the laboratory molded specimens. However, $k$ decreased with increasing ${\sigma }^{\prime }$ in all of the laboratory tests, as expected, and the differences between $k$ values measured at the lower stresses (6.9–13.8 kPa) and those measured at the higher stresses (20.7–34.8 kPa) were statistically significant. The flexible-wall tests underestimated $k$ relative to the slug tests, but the differences generally were small (on average, within a factor of 2) when considering only the flexible-wall specimens tested at the lower applied stresses (6.9–13.8 kPa) that more closely matched the in situ stresses. The results demonstrate the importance of conducting laboratory $k$ tests on SB backfill at stresses representative of the in situ stresses, which are limited by frictional load transfer along the sidewalls and tend to be lower than expected based on an assumed geostatic stress distribution.

The interaction between a spudcan and an existing footprint is one of the major concerns during the reinstallation of jack-up rigs. This paper reports the results from a series of centrifuge model tests undertaken to assess the efficiency of a recently developed novel spudcan shape with a flat base and four holes through the base to ease spudcan–footprint interactions. The experimental program was carried out at $200\mathit{g}$ in a beam centrifuge. The footprints were created either manually using a cutting tool or through spudcan penetration and extraction allowing a typical operation period as well as an elapsed time prior to reinstallation. While the former allowed a consistent evaluation of the benefits of spudcan shape, removing the additional variability due to soil strength heterogeneity, the latter allowed for examining the effect of real field footprints. For manually created shallow footprints in soft clay, comparing the responses with those on a generic spudcan, it was possible to show that the novel spudcan reduced the maximum horizontal force and moment by up to 47%–62% and 28%–36%, respectively. The critical offset distance was found at $0.75D$. For manually created deep footprints in stiff clay, the reductions were 20%–59% and 9%–45%, respectively. The critical offset distance was found at $0.5D$. For footprints created by penetrating and extracting a spudcan, the critical offset distance was identified at $0.75D$. The efficiency of the novel spudcan was calculated with the reduction of maximum horizontal force and moment by 42%–59% and 21%–62%, respectively.

A full-scale field test program was carried out to investigate the effects of drilling for tieback anchors on the surrounding ground. The test anchors were drilled from the ground surface through a soft clay deposit and into bedrock. Five different drilling methods were compared. All methods caused excess pore pressures in the surrounding clay, up to 70 kPa, extending several meters away from where drilling took place. This impact on pore pressures was for most drilling methods significantly larger than what has been observed for driven piles in clay. High penetration rate combined with water flushing during drilling through soft clay is the main reason for the effects on the pore pressure. Drilling with a down-the-hole hammer and air flushing through a layer of moraine and into bedrock in one of the test areas (Area B) caused significantly larger excess pore pressures and ground settlements than the other drilling methods. Approximately half of the maximum resulting settlements of 12 mm in Area B was most likely caused by reconsolidation of remolded clay around the casing tubes. Drilling with water-driven hammer in Area C had less effect on both pore pressures and ground settlements.

This paper presents a methodology developed for soil classification and state parameter ($\psi$) evaluation for granular soils based on seismic cone penetration measurements. The method uses a two-stage soil classification system that is first applied to categorize soil groups and identify drainage conditions. The ratio of the small strain shear modulus and the cone tip resistance $G_0/q_t$ is the basic element for soil classification that, on a subsequent stage, is combined to the state parameter $\psi$ to identify sands that potentially exhibit strain softening response upon undrained loading.

The empirical approach adapting the Stress History and Normalized Soil Engineering Properties (SHANSEP) concept relates the average overconsolidation ratio (OCR) of plastic soils to the average pile side adhesion normalized to the effective overburden stress. Additional pile case histories were identified and used to expand an existing database and slightly revise the side adhesion design model. The data set then was used to calibrate resistance factors for the SHANSEP-based design model within the Load and Resistance Factor Design (LRFD) framework. The resistance factors derived provide a significantly greater nominal capacity than those presently available in the AASHTO code due to the accuracy of the SHANSEP-based design approach. For example, piles loaded in compression and for bridge spans with a dead-to-live load ratio of three returned resistance factors equal to 0.875 and 0.769 for reliability indexes of 2.33 and 3.09, respectively, in the absence of variability in OCR. Resistance factors then were calibrated in consideration of the uncertainty in OCR to allow the practitioner to directly consider the uncertainty in stress history in the reliability of the SHANSEP design approach. Reductions in the resistance factors ranged from 2% to 67% for coefficients of variability in OCR ranging from 5% to 50%. The reliability-based SHANSEP approach for side resistance represents a significant improvement over currently accepted design models in the AASHTO code and can be directly used to justify improved site investigation.

Aspects related to differences in the behavior of plate load tests (PLT) bearing on highly porous, lightly bonded weathered clay in its natural structured and dynamically compacted states are addressed in this paper. Dynamic compaction is a ground improvement technique involving the release of a substantial weight from an elevation to the ground. The studied bonded residual soil presents specific characteristics, such as high stiffness at small deformations due to natural cementitious bonding, high porosity (higher than 50%), and high hydraulic conductivity (about ${10}^{-5}\mathrm{m}/\mathrm{s}$). Due to dynamic compaction, soil stiffness is reduced at small strains from the breakage of cementitious bonds caused by the impact of the heavy weight. Additionally, porosity is reduced from 55% to approximately 49%, and the degree of saturation is increased from approximately 73% for the natural soil condition to approximately 90%. The angle of internal shearing resistance (${\varphi }^{\prime }$) increased from 30.5° to 35.4°. The applied pressure-displacement results of PLT that rests on natural and dynamically compacted soils were assessed. The young modulus from PLT ($E_{field}^{\prime }$) for the naturally bonded state is higher than $E_{field}^{\prime }$ of PLT on a dynamically compacted state for displacements up to approximately 20 mm. This phenomenon occurs because the latter displayed the bond damage due to tamping that overcame the effects of porosity reduction. In contrast, at large displacements, the effects of the soil porosity reduction caused by heavy tamping are more effective than the effects of bond breakage that ends up increasing the bearing capacity of the PLT from 215 kPa on naturally bonded soil to 297 kPa on dynamically compacted soil.