Journal of Geotechnical and Geoenvironmental Engineering

The deep-mixing method (DMM) involves the mechanical mixing of in-situ soil with various stabilizing binders, which chemically react with the soil or the groundwater. Microstructural analyses are valuable tools to support ordinary geotechnical laboratory tests to assess the effectiveness of ground improvement works. This paper presents the results of microstructural analyses on in-situ retrieved samples and laboratory mixed specimens related to an actual deep mixing job site. Mercury porosimetry and X-ray computed Microtomography were used to determine the total porosity and to characterize the pore network of both types of samples. The results of the analyses allowed a qualitative understanding of the degree of mixing of the soil with the binder suspension under laboratory and field conditions. Additionally, an original correlation between total porosity and unconfined compressive strength was obtained based on the experimental data for cement-treated sandy soils at long curing time.

This paper presents a cyclic equivalent spring ($p\text{-}y$) model describing lateral soil resistance on offshore well conductors and piles in normally to lightly overconsolidated clays subjected to fatigue cyclic motions. Improved understanding and characterization of cyclic lateral soil response is critical in fatigue assessment of well conductors and piles subjected to dynamic fatigue loads. Key features of the model include nonlinear load-displacement behavior with stiffness degradation during cyclic loading. The model provides a full description of soil resistance during lateral loading, including an initial short-excursion monotonic loading stage, a transient stage of progressive degradation in stiffness from the first excursion, and a steady-state stage involving minimal changes in soil stiffness after a large number of load cycles. The model input parameters obtained from back-analysis of data derived from centrifuge tests on model conductors subjected to harmonic lateral loads are presented in this paper. This model has capabilities of simulating random load sequences. Fatigue damage in well conductors and piles arises from changes in axial and bending stresses, with the latter being more dependent on lateral soil response. Accordingly, the proposed model is evaluated primarily in terms of its ability to accurately predict bending moments when the spring model is used in conjunction with a laterally loaded soil-structure interaction model. The model successfully predicts the maximum change in cyclic bending moment (change in moment during a load reversal) and the location of the maximum cyclic moment along the conductor depth approximately within a 20% range. This performance evaluation was derived by comparing the model computations/predictions to the test data from the centrifuge program and validated within the tests displacement range of 0.1D. The current form of the model does not consider consolidation effects, which may significantly affect long-term loading predictions used in fatigue life assessments.

The paper examines the problem of the soil-structure interaction for buildings founded on piles throughout the comparative analysis between the seismic demand in compliant base and fixed base models. The aim of the work is to introduce a simple approach for evaluating the effects of soil-foundation-structure interaction (SFSI) for buildings founded on piles and, hence, to quantify the relevance of SFSI effects for this kind of structure. Inertial interaction analyses are carried out by idealizing the complete system as a linear SDOF on a deformable base represented by frequency dependent springs and dashpots. An application of the proposed methodology to a case study of a nine-story building resting on two well-studied subsoils, a deep clay layer from Piana del Fucino (Italy) and a pyroclastic deposit from Napoli, is presented and discussed. Reference is made to a complete seismic risk analysis in which the input signals are grouped into strips according to the conditional spectrum method. As a further objective, the effect of wall infills on the seismic demand in the reference buildings is investigated. The results show that for the pyroclastic deposit the seismic demand in the compliant model is comparable with that in the fixed base. By contrast, SFSI leads to a relevant reduction of the seismic demand for buildings on the clay layer. It is concluded that, contrary to the common belief, SFSI may also be relevant for tall buildings if they rest on soft soils.

Pipelines as infrastructure components are very vulnerable to geohazard-induced ground deformation and failure. Soil–pipe interaction (SPI) thus is very important for the assessment and design of resilient pipeline systems. Previous work on SPI modeling has been based on crude assumptions, such as representation of the soil as uncoupled three-dimensional bilinear springs, and quasi-static loading conditions. This paper proposes a simplified macroelement designed to capture the effects of dynamic SPI in cohesionless soils subjected to arbitrary loading normal to the pipeline axis. First, we present the development of a uniaxial hysteresis model that can capture the smooth nonlinear reaction force-relative displacement curves (FDCs) of SPI problems. Using the unscented Kalman filter, we derived the model parameter $\kappa$ that controls the smoothness of transition zone from linear to plastic using published empirical and experimental data. We extended this uniaxial model to biaxial loading effects, and showed that the macroelement can capture effects such as pinching and shear–dilation coupling. The model input parameters were calibrated using finite-element (FE) analyses validated by experiments. The FDCs of the biaxial model were verified by comparison with FE and smoothed-particle hydrodynamic (SPH) simulations for different loading patterns: cyclic uniaxial, 0-shaped, 8-shaped, and transient loading. Accounting for smooth nonlinearity, hysteresis, pinching, and coupling effects, the proposed biaxial macroelement showed good agreement with FE and SPH analyses, while maintaining the computational efficiency and simplicity of beam on nonlinear Winkler foundation models, as well as a small number of input parameters.

Subsurface geophysical investigations have the potential of providing information for the long-term monitoring of geotechnical assets. This research evaluates the suitability of vertically and horizontally orientated, embedded time-domain reflectometry (TDR) measurements for monitoring of near-saturated, fine-grained soils under vertical loading conditions. TDR measurements were carried out regularly during vertical loading and unloading of near- and fully-saturated soil mixtures containing fine sand, kaolinite, and bentonite. The results show that TDR probe orientation, in relation to the load direction, affects the values of TDR measured apparent permittivity (AP) and bulk electrical conductivity (BEC). The relationship between the soil void ratio and AP was found to be clearer when measured in the direction of loading, whereas AP and BEC, measured normal to the load application, appears to reflect changes in pore water pressure. BEC was found to be more variable and less obvious. It is concluded that monitoring relative changes in temporal AP and BEC using embedded TDR sensors can provide unique and valuable information on how a soil responds to loading under near-saturated conditions.

Desaturation has been a cost-effective and straightforward ground improvement method for liquefaction mitigation. Recent advancements in geotechnical numerical simulations have allowed for the simulation of desaturated soils in dynamic problems. The objective of this study was to evaluate the numerical capabilities of predicting liquefaction resistance for desaturated sands. A finite-element method (FEM) analysis was performed to simulate a large shaking table test (STT) that aimed to evaluate the desaturation ground improvement method for liquefaction mitigation. This paper consists of three parts: (1) a brief description of STTs carried out by the National Institute for Land and Infrastructure Management (NILIM). In the STTs, the degree of saturation $S_r$ was controlled to within approximately 80%–100%. (2) Simulation of elemental scale tests for desaturated sands under undrained triaxial cyclic conditions. (3) FEM analysis of the STTs. Numerical analyses were performed using LIQCA2D17. The results showed that the numerical analysis reasonably predicted the ground motion intensities and pore water pressure responses of the desaturated sand. The numerical analysis indicated that volumetric strains and pore water seepage induced changes in $S_r$ during loading. These phenomena resulted in a transition from desaturated to saturated conditions.

The dynamic cone penetration test (DPT) developed in China has been correlated with liquefaction resistance of gravelly soils based on field performance data from the ${\mathrm{M}}_{\mathrm{w}}7.9$ Wenchuan earthquake. With a diameter of 74 mm, DPT would be less sensitive to gravel size particles than the SPT or CPT and could be a viable assessment tool depending on gravel size and percentage. In this study, liquefaction resistance is evaluated using four DPT soundings with two hammer energies and shear wave velocity ($V_S$) measurements in Avasinis, Italy, where gravelly sand liquefied in the 1976 Friuli, Italy, earthquake. The DPT correctly predicted liquefaction at three sites where liquefaction was observed; however, it also predicted liquefaction in a highly stratified silt and silty gravel profile where ejecta was not observed. This failure appears to be a result of the “system response” of the profile, which impeded ejecta as identified at similar stratified sites in New Zealand. $V_{S1}$-based triggering curves often predicted no liquefaction at sites where liquefaction was observed, suggesting that the boundary curves may need to shift to the right for gravelly soils. Standard SPT energy corrections were found to be reasonable for the DPT.

Data obtained during and after major hurricanes in the Gulf of Mexico (GoM) in the past three decades provide valuable information about the design model uncertainties for fixed steel offshore platforms because multiple offshore platforms were loaded close to and/or beyond the predicted capacity and, in particular, because multiple damages/failures were observed in the jacket superstructures, and a three-pile jacket system was well documented and extensively studied in the postfailure stage. The objective of this paper is to extract information on the current fixed offshore platform design practice by comparing the predicted versus observed performance of 18 offshore platforms in five major GoM hurricanes using Bayes’ theorem. The Bayesian calibration indicates that the American Petroleum Institute design recipe, on average, (1) is close to being unbiased for assessing the safety margin for the jacket superstructure performance, (2) tends to be unbiased for the pile lateral capacity using the upper bound lateral bearing factor in $p\text{-}y$ curves with the mean yield strength of pile steel, (3) is slightly conservative by 5% for the pile axial capacity in clay, and (4) is conservative by close to 50% for the pile axial capacity in sand. It is concluded that a jacket system with four or more legs/piles is less likely to fail in the foundation system than in the superstructure.

This paper presents a new approach to assess the liquefaction triggering of saturated sandy soils based on comprehensive laboratory datasets in conjunction with the concept of binary packing material for sandy soils. The equivalent skeleton void ratio ($e_{sk}^{*}$) is used as an alternative state index for sandy soils with fines content ($FC$) less than a threshold value ($F{C}_{th}$). To characterize the liquefaction triggering curve for the correlation between the cyclic resistance ratio (${\mathrm{CRR}}_{15}$) in 15 cycles and the corrected shear-wave velocity ($V_{s1}$), a series of undrained cyclic triaxial tests as well as bender element tests have been performed on six types of saturated sandy soils. A remarkable finding of the laboratory investigation is that both ${\mathrm{CRR}}_{15}$ and $V_{s1}$ are virtually uniquely related with $e_{sk}^{*}$ for all six sandy soils. This finding is confirmed by the experimental data on ${\mathrm{CRR}}_{15}$ and on $V_{s1}$ for different sandy soils published in the literature. The parameters defining the relationships between ${\mathrm{CRR}}_{15}$ and $e_{sk}^{*}$ between $V_{s1}$ and $e_{sk}^{*}$ can be simply determined through a unique set of explicit expressions which incorporate some basic index properties of the host sand and fines. In this regard, the proposed procedure provides a significant advantage in the evaluation of liquefaction triggering of sandy soils in practice.

In geotechnical engineering, interference effects caused by the construction of closely spaced footings have a significant influence on the system behavior of each individual footing. As the mutual impact of two footings constructed in close proximity has only been analyzed for identical footings, our aim with this paper is to investigate the interfering effects of closely spaced nonidentical rough footings considering variations of stresses applied to both footings. Therefore, lower and upper bound simulations have been carried out using the finite-element limit analysis (FELA). A validation of the numerical model was accomplished by comparing results for interference effects of identical footings with existing studies in terms of interference factors ${\xi }_{\gamma }$. Furthermore, nonidentical footings with equally and differently scaled stresses were studied and corresponding failure mechanisms analyzed. In total, four types of failure mechanisms could be identified in which two mechanisms always compete each other, depending on friction angle, footing widths, spacing, and loading. In contrast to identical footings with combined failure mechanisms, the results show that for nonidentical footings, failure mechanisms most likely develop only below one footing.

The behavior of an energy pile in a group is different from that of an isolated energy pile due to thermal and mechanical interactions. This study aims to extend the load transfer method to consider the mechanical and thermal interactions of energy piles in groups. The load displacement curve of an energy pile in a group is modified from that of the isolated pile through a displacement factor to account for group effects. This paper presents the results of a full-scale field test of four operating energy piles over 12 months, against which the proposed method is validated. Temperature changes of $\mathrm{\Delta }\mathrm{T}=5°\mathrm{C}$, 10°C, 15°C, and 20°C were applied in the analyses. A comparison between the experimental and numerical results reveals the capability of the approach to provide information about the vertical displacement, vertical stress, and mobilized shaft resistance profile for an energy pile in a group subjected to both mechanical and heating thermal loads.

Interpretation of field vane tests in transient soils requires assessing partial drainage effects within the soil surrounding the vane. This subject is investigated in this paper using a nonlinear poroelastic model to simulate the rotation of a rigid cylinder in a nonlinear poroelastic medium. This simplified approach of a vane test yields analytical expressions that help to explore rate effects in silty materials. Analytical expressions were validated against experimental results in low permeability soils under undrained conditions as well as field vane tests performed on silty tailings. The dimensionless velocity $v/k$ is proposed for normalization of testing data allowing to assess the effects of normalized strength, stiffness, and extent of the influence zone. It is concluded that the ratio of the drained to undrained resistance is generally lower than 3. As further considerations of practical importance, the standard velocity of $0.1\mathrm{deg}/\mathrm{s}$ is not suitable to reach undrained conditions in silts. A solution is then established to account for possible errors induced by pore pressure dissipation, yielding a practical criterion for determining the undrained shear strength.

Displacement piles are driven to support a wide range of structures. Predicting their axial limiting capacities and load-displacement behavior is critical to many such engineering applications. Although field load tests may be conducted to check design assumptions, such tests can prove expensive and difficult to generalize. Numerical analyses undertaken to support design face uncertainty over the potentially important effects of pile installation because no well-developed method exists to predict the stresses applying during and after driving. Recent experiments have provided evidence regarding the stresses and strains developed around displacement piles during installation in sand that can help guide representative numerical modeling. This paper contributes to this development by reporting large displacement numerical analyses and linking these to high-quality experiments. The arbitrary Lagrangian–Eulerian (ALE) options available in ABAQUS 2016/Explicit have been employed to simulate highly instrumented calibration chamber tests made with closed-ended piles penetrated into sand. Predictions for the stress components developed during and after pile installation are presented, along with measurements made by other authors of the corresponding strain fields. The simulations’ broad agreement with the available experimental evidence indicates that the adopted ALE technique and soil modeling approach are appropriate for pile installation analysis in sands.

One-third of the global land area suffers from wind erosion, and its prevention is a critical issue in arid regions of the world. During a wind erosion event, the impacts of saltating grains on the surface cause abrasion of crusted soil surfaces. The topic of this study is to examine the efficiency of sand biocementation to diminish the wind erodibility of an aeolian sand. The erosion rate, number of emitted particles, and flux of the eroded mass from surface (as erodibility indicators) of the biocemented crust, formed by Bacillus megaterium, were measured in a wind tunnel at three different wind velocities; moreover, one extra condition with the presence of impacting particles at the lowest wind velocity was tested. According to the results of the tests, the biocemented crust could provide considerable protection for erodible aeolian sand against wind erosion (without impacting particles), diminishing the sand erodibility indicators by two to four orders of magnitude. However, with the impact of saltating particles, the formed crust could reduce erodibility indicators only by one order of magnitude.

Clayey/silty sands are widespread as naturally sedimentary soils such as marine deposits in estuaries and offshore locations. They belong to a unique class of gap-graded soils featuring a deficiency of certain range of particle sizes and behave differently from those containing pure sand aggregates. The fines improve the stiffness of host sands, which reduces the postconstruction settlement and arching effect of foundations and dams. In this study, a simple yet effective compression model is proposed for clayey/silty sands using the equivalent void-ratio concept. A structure parameter is incorporated into the model to denote the contribution of fines on the effective force chains of gap-graded mixtures. The structure parameter is affected by the particle-size distribution and basic features of sand aggregates. It can be approximated by a constant value, which represents a combination effect of the influence factors. The limit (inactive) void ratio of clayey/silty sands decreases linearly with the increase of fine content and the structure parameter. The proposed model contains only three model parameters, all of which have clear physical meanings and can be readily calibrated based on two conventional compression tests. Simulations using the newly proposed model revealed that it is versatile to capture key features of gap-graded mixtures, including the effect of initial void ratio, interaggregate void ratio, and fine content. The performance of the proposed model is verified with tests data for six clayey sands and five silty sands (or sandy gravel). The differences between the test data and model predictions for both clayey sands and gap-graded granular mixtures are marginally small. The model can be practically useful for predicting the deformation of clayey/silty sands.

The hospital building of the Federal University of Rio de Janeiro, Brazil, has been only partly occupied since its construction in the 1960s. The failure in 2010 of two columns in the unoccupied part led to the decision to demolish this area. After demolition, settlement of the adjacent block developed, and underpinning was needed. The underpinning consisted of the installation of micropiles (also known as root piles) incorporated into the existing footings by a new cap. Pile installation was achieved by rotary drilling with an auxiliary tube, and the debris was removed by water circulation. Then, rebars were placed, and cement-sand mortar was pumped in as the auxiliary tube was removed. Because significant settlement occurred when pile drilling, circulation water was replaced by compressed air, and piles with smaller diameters were adopted. Continuing settlements led to a change in the underpinning solution: the use of jacked piles. This paper addresses the observed settlement during underpinning and correlates them with the different underpinning processes. The micropiles produced considerable settlement during their installation, and the underpinned columns still underwent additional settlement before stabilization. Jacked piles produced very small settlement during their installation and practically stopped settlement when complete.

This paper focuses on the small-strain shear modulus ($G_{\max }$) of natural pumiceous (NP) sands, a type of crushable volcanic soil commonly found in the North Island of New Zealand. These sands are also compressible and lightweight, resulting in difficulty to accurately evaluate their geotechnical properties. To better understand the $G_{\max }$ dependency of these NP sands on effective confining pressure (${\sigma }_c^{\prime }$) and void ratio ($e$), bender element tests are performed on three types of locally sourced NP sands and, for comparison purposes, similar tests are conducted on hard-grained Toyoura sand. The results illustrate that the $G_{\max }$ of NP sands are considerably lower than that of Toyoura sand over a wide range of $e$ and ${\sigma }_c^{\prime }$. Furthermore, materials with higher pumice content show higher dependency on ${\sigma }_c^{\prime }$ and lower dependency on $e$ compared with those with lower pumice content as well as Toyoura sand. Particle characteristics (e.g., particle shape, particle-size distribution, particle crushing, pumice content, compressibility, and fines content) are taken into consideration to explain the different response of the tested materials.