Journal of Geotechnical and Geoenvironmental Engineering

Embodied energy (EE) and carbon dioxide (${\mathrm{CO}}_2$) emissions assessments have become more common as sustainable development considerations are incorporated into geotechnical practice. To date, methods developed to conduct such assessments are deterministic; however, given the inherent variability in nature and in industrial processes, deterministic calculations for the EE and ${\mathrm{CO}}_2$ emissions of a project are an incomplete representation of reality. In this paper, the development of a framework to account for uncertainty in assessments of total project EE and ${\mathrm{CO}}_2$ emissions is described, using the construction of rammed aggregate columns for foundation support of a new dormitory building on the Virginia Tech campus as a case history. The framework uses the Streamlined Energy and Emissions Assessment Model (SEEAM) method and Monte Carlo simulation to generate simulated data sets of total EE and ${\mathrm{CO}}_2$ emissions, based on variability in both the EE and ${\mathrm{CO}}_2$ coefficients and the subsurface conditions. EE and ${\mathrm{CO}}_2$ emissions estimated using actual construction quantities served as the reference case to which all predictions were compared. The framework assumes the EE and ${\mathrm{CO}}_2$ emissions coefficients follow a lognormal distribution. The subsurface conditions of interest are considered to follow the best-fit distributions to histograms of values obtained from the geotechnical investigation. Using the Monte Carlo simulated data, the means, standard deviations and confidence intervals for total EE and ${\mathrm{CO}}_2$ emissions can be determined. In addition, statistical inference can be used with the simulated data to determine if different project alternatives result in significantly different EE and ${\mathrm{CO}}_2$ emissions. This information can assist geotechnical engineers in making more sustainable project decisions, thus adding value to their services.

The uplift load test is the most widely used technique for assessment of the performance of micropiles. Although this static load test is easy to perform and interpret, it is expensive, slow to implement, and cannot be used systematically because it destroys the micropile. A new methodology based on a simple low-strain dynamic load test (LSDT) is proposed to develop a systematic and inexpensive method for assessment of performance of a large number of micropiles. The advantage of this methodology is that it is easy to carry out, requires low-impact energy compared with a classical dynamic load test, and allows immediate interpretation. After describing the proposed methodology, the calibration, and the subsequent validation of the test method, results from full-scale micropiles at an experimental site and three real sites are presented. The results show that the methodology proposed allows confirming micropile performance under service loads in real time without disturbing the micropile.

Microbially induced calcite precipitation (MICP) is a promising biocementation process that can improve the geotechnical properties of granular soils through the precipitation of calcite. In this study, a large-scale biocementation experiment was completed to evaluate differences in improvement obtained using a bioaugmentation approach with S. pasteurii and a biostimulation approach, which stimulated native ureolytic microorganisms to complete the process. Two identical 1.7-m-diameter soil tank specimens containing a 0.3-m-thick layer of sand were treated using three wells at a well-to-well spacing of 1.2 m. Treatments were applied daily over 12 days and were designed to evaluate differences between tanks by creating a nonuniform spatial distribution of improvement. During treatment, shear wave velocity and biogeochemical changes were monitored spatially and temporally. Post-treatment, cone penetration tests were completed to assess improvement, and samples were obtained for calcite content measurements. Similar final improvement was observed between tanks, with highly cemented regions achieving shear wave velocities over $960\mathrm{m}/\mathrm{s}$ and increases in tip resistances of over 419%. Results suggest that biostimulation may enable comparable biocementation improvement at the meter scale.

Small unmanned aerial vehicles (sUAVs) were used to reconnoiter, image, and model the effects of soil liquefaction at two separate sites following the M8.2 and M7.6 earthquakes near Iquique, Chile, on April 1 and 2, 2014, respectively. Geotechnical investigators performed conventional observations/measurements at the two sites using traditional reconnaissance methods, and virtual observations/measurements using sUAV-based remote sensing and structure from motion (SfM) computer vision. Two types of sUAV platform/sensor combinations were evaluated for this study. Comparisons between the traditional and sUAV-based reconnaissance methods were performed and observations are discussed. The sUAV-based point cloud models of the sites were between 770 and 2,600 points per square meter depending on the camera that was used, with average model dimensional error ranging from $\pm 1.0$ to $\pm 3.5\%$. Lateral spread displacement measurements from the UAV-based three-dimensional models were generally within 9 cm of the lateral spread displacements measured in the field, and measured vertical deformations from the models generally agreed well with the deformations reported by previous investigators. This study demonstrates that sUAVs can be useful instruments for post-disaster geotechnical surficial site reconnaissance.

Frozen soils, including seasonally frozen soils and perennially frozen ground, or permafrost, exist extensively in Alaska and other cold regions. During past earthquakes, extensive damages were observed in pile foundations, and frozen ground appears to be the direct cause of at least some of those damages. This paper analyzes frozen soil lateral resistance and its effects on pile foundations during earthquakes based on the testing results on reinforced concrete-filled steel-pipe piles embedded in deep seasonally frozen silts under large deflection and recommends an analysis tool for seismic design practices. Pile performance data measured in the test—including bending moment and deflection—were used to back-calculate the $p\text{-}y$ values for the top half-meter of frozen silt. A $p\text{-}y$ curve for frozen silt is proposed based on the experimental data. Results from modeling the test pile using the proposed $p\text{-}y$ curve agree well with the test results. The proposed $p\text{-}y$ curve was further validated by independent field test data. It is concluded that the proposed $p\text{-}y$ curve is capable of modeling both seasonally frozen and perennially frozen silts in frozen soil-pile interaction analyses during short-term lateral loading. Recommendations are provided on how to select soil parameters for constructing frozen-silt $p\text{-}y$ curves.

The effects of an underwater explosion on a tunnel buried below submerged ground were studied through a combination of physical model tests, utilizing a geotechnical centrifuge, and numerical model analyses, using an explicit dynamic hydrocode program. Centrifuge tests conducted at $70g$ on reduced-scale physical models were used to assess the effects of 0.9 t of explosives on a 5.5-m-diameter prototype tunnel. The numerical model was subject to a two-stage validation process to compare the pressures in water and strains on the tunnel by comparing with theoretical and experimental results, respectively. The strains in the tunnel were found to increase with water level above the ground surface; this continued up to a certain point, after which the strains remained constant. The point after which the strains remained constant was found to depend on the mass of explosives. As expected, the strains were found to increase with reduction of soil cover above the crown. This approach may be useful in designing new underwater tunnels and in evaluating mitigation measures for existing tunnels.

This paper provides a theoretical derivation for the unconfined compression strength of artificially cemented granular soils. The proposed developments are based on the concept of superposition of failure strength contributions of the soil and cement phases. The granular matrix obeys the critical state soil mechanics concept, whereas the strength of the cemented phase can be described using the Drucker-Prager failure criterion. In the process, the analytical relation is suitably adjusted to parallel a recently proposed empirical relationship that links unconfined compression strength of artificially cemented granular soils to an adjusted porosity/cement ratio parameter. Although the proposed analytical relation fits the experimental data for different granular soils and cement curing time well, further parametric analysis offers the possibility of exploring the effect of some material parameters on the unconfined compression strength of artificially cemented granular soils.

A series of bender element tests and drained and undrained monotonic triaxial compression and extension tests were performed on air-pluviated samples of Hostun sand. Samples were prepared to different initial void ratios, consolidated under various isotropic and anisotropic stress states, and sheared using different stress paths and a wide range of deformations to characterize the sand’s stress-strain response. The results suggest that the sand’s small-strain behavior essentially depends on the current void ratio and mean effective stress. Within the medium to large strain range, a state-parameter approach in conjunction with the critical-state framework can successfully predict the distinctive states of the sand’s monotonic response, namely the phase-transformation, peak-stress-ratio, and critical states. Furthermore, the data are used to examine a stress-dilatancy relationship often incorporated in constitutive models. The characterization presented herein aims at assisting the efficient calibration of numerical models and provides insight into this sand’s behavior, thus supporting the interpretation of results of physical modeling involving this sand. This paper highlights the importance of characterizing sand’s behavior over the full strain range and shows that accurate predictions of the critical state and small-strain stiffness are crucial to assess other aspects of the sand’s behavior.

The work investigates the behavior of a deep excavation which forms part of a 100 m wide basement excavation located in Boston, Massachusetts. Two different types of tied-back retaining walls were used, i.e., a soldier pile tremie concrete wall and a traditional reinforced concrete diaphragm wall. The glacial marine clay (Boston Blue Clay) deposit was modeled with the Kinematic Hardening Model for Structured soils (KHSM), its reduced bubble model version (KHM) and the well-known Modified Cam Clay (MCC) model. The difference between the models is the prediction of softening with loss of structure as plastic strains occur. The values of the optimised soil parameters used in the simulations were obtained by a careful calibration of the models against a range of advanced laboratory and field tests performed at the site. Comparison of the available horizontal wall movements monitoring data with the undrained finite-element predictions revealed a very satisfactory agreement when the KHM was used in conjunction with a small-strain elastic formulation. The relatively small increase in lateral wall deflection in the presence of initial structure accounted for in the KHSM confirms that the small-strain properties of the soil control the magnitude of excavation deformations. Finally, using a coupled-consolidation analysis and the KHSM, an excellent agreement between the observed and measured pore water pressures and ground movements of the excavation base was achieved.

In 2012, a mechanically stabilized earth (MSE) wall was demolished in Virginia due to road realignment activities, providing an opportunity to assess the condition of the steel-bar mat reinforcement after 36 years in service. Steel and backfill samples were collected from various locations throughout the wall. The remaining zinc thickness from the galvanized steel was measured utilizing three different techniques; the electrochemical properties of the backfill were also measured. It was found that corrosion was highest at the joint between the pavement and moment slab and in locations downstream of a drainage pipe through the wall. By industry design standards, the electrochemical properties of the backfill, specifically the chlorides and resistivity, indicate the backfill collected is aggressive; however, the wall was in good condition, with an estimated service life of 150 years based on the measured corrosion. This article provides an overview of this case study, the testing performed, and the results; it also examines methods to estimate initial thickness of the zinc coating for insights on the performance of galvanized steel used in earthwork applications.

This paper describes investigation, testing, analysis, and slope history used to determine the two-phase failure mechanism involved in the 2014 landslide near Oso, Washington. The first phase involves a slide mass located above the frequent landslides in the lower portion of the slope and extends to near the slope crest. This slide mass had a large potential energy, which moved downslope, and pushed the water-filled colluvium that had accumulated along the slope toe across the valley, resulting in it flowing almost 1.5 km. Evacuation of the Phase I slide mass left the upper portion of the slope unbuttressed and oversteepened, causing a second landslide (Phase II) but it primarily remained on the source slope because the back edge of the Phase I slide mass prevented further movement and the dense and unsaturated upper soils did not undergo a significant strength loss like the water-filled colluvium.

Frozen soils, including both those seasonally frozen and perennially frozen, exists extensively in Alaska and other cold regions. During past earthquakes, widespread damage was observed in deep foundations in the ground, and frozen ground appears to be the direct cause of at least some of that damage. The aim of this paper is to investigate the effects of seasonally frozen soil on deep foundations during lateral loads induced by earthquakes, ice, wind, vehicular impacting, and other loads with a short duration, and to recommend simplified tools for design practices. Two identical reinforced concrete-filled steel pipe piles were tested to large deformations at unfrozen and frozen soil conditions to demonstrate the effects of seasonally frozen soil on the lateral behavior of steel pipe piles. The pile tested at unfrozen condition behaved as a rigid pile, and the other at deep seasonally frozen condition formed a very shallow plastic hinge. Pile performance data in deep seasonally frozen silts were used to evaluate the fixity depth approach parameters, which include depth-to-maximum-moment, depth-to-fixity, and analytical plastic hinge length. In addition, the test data were used to calibrate a finite element (FE) model for assessing the effects of varying seasonally frozen soil depths on the pile lateral behavior and fixity depth approach parameters. These fixity depth approach parameters for various frozen soil depths can be used to account for the effects of seasonally frozen soil on pile lateral behavior in design practices.

Slopes in soil and rock are often defined in terms of their static and pseudostatic factors of safety. For the case of sliding along a single plane, a simple equation relates the pseudostatic factor of safety to the static factor of safety, the slope of the failure plane, and the friction angle for the single plane model and gives remarkably accurate estimates for more complicated analyses. A further result is that the horizontal seismic coefficient necessary to bring the pseudostatic factor of safety to 1.0 increases as the slope of the failure plane increases. This result is counterintuitive, but it arises because of the complicated interactions among the parameters defining the factors of safety.

A comprehensive testing program was completed on municipal solid waste (MSW) at the Cozzo Vuturo landfill, located in the periphery of Enna (Sicily, Italy) to evaluate the representative dynamic waste material properties. The small strain shear modulus, the strain-dependent normalized shear modulus reduction, and the material damping relationships of MSW were investigated using field and laboratory tests. The seismic dilatomer Marchetti test (SDMT) was used to derive the shear wave velocity profiles and the dynamic properties of the deposited waste materials. Measurements of wave velocities were also completed using a seismic refraction tomography and a multichannel analysis of surface waves (MASW) to estimate the vertical distribution of the compression wave velocity ($V_P$) and shear wave velocity ($V_S$), respectively. The dynamic properties of MSW were also investigated using combined resonant column, torsional shear (RCTS) and cyclic triaxial devices (CTX). In this paper a comparison between SDMT, MASW, and laboratory test results is reported. A good agreement has been found between the dynamic properties of the waste materials derived by the in situ and laboratory tests completed in this study and those reported in the literature.