Soil Behavior Research Articles

Increasing the Performance of Ring Foundation to Lateral Loads by using a Skirt Foundation

In numerous engineering foundation designs, the influence of lateral loads is frequently underestimated in calculations. Consequently, recent studies have increasingly concentrated on comprehending the behavior of soil and foundations when subjected to lateral load influences. The present study aims to examine the performance of ring foundations, a common engineering solution employed in the construction of tall and slender structures that are vulnerable to lateral loads, such as those exerted by wind forces. The objective of this study is to enhance the lateral resistance of ring foundations by incorporating skirt foundations. The efficacy of skirt foundations was evaluated through a series of tests conducted on sandy soils of varying densities, ranging from dense to medium loose sand. Subsequently, lateral loads were applied to the ring foundations, both with and without skirt foundations. The results demonstrated that the lateral resistance increased in proportion to the ratio between the inner and outer diameters. Furthermore, the improvement rate was enhanced by the addition of the skirt foundation. Additionally, the lateral resistance increased with increasing the skirt foundation depth, reaching a maximum of approximately 50-100%. Similarly, an increase in the skirt inclination ratio to 450 resulted in a lateral resistance increase of up to 650%.

Effects of ground motion characteristics on liquefaction response of earth dams using a non-Darcy hydro-mechanical model

During earthquake-induced excitations, significant pore pressure gradients can develop in earth dams, limiting the applicability of Darcy’s law for fluid flow. This study investigates the behavior of a liquefied earth dam subjected to various seismic excitations with differing frequency content, aiming to enhance insights into the effects of dynamic loading on fluid–structure interactions. To accurately capture the soil’s response, the Pastor-Zienkiewicz generalized plasticity model is employed to represent realistic soil behavior. Additionally, a modified Forchheimer equation is used to address varying permeability through a non-Darcy flow law. Numerical simulations, performed using a finite element code developed in Fortran, are validated through comparative analyses with previous studies. The results show that in low-permeability regions, changes in earthquake frequency content have minimal impact on discrepancies between the predicted results of Darcy and non-Darcy models. However, the non-Darcy model generally estimates horizontal displacements to be around 4% higher on average in these regions. This difference increases as earthquake frequency content decreases, reaching up to 6%. In contrast, in permeable regions, the non-Darcy model predicts significantly higher horizontal displacements, with an average increase of approximately 20% for high-frequency seismic events and 8% for low-frequency ones. Additionally, in high-permeability regions, the non-Darcy model deviates notably from the Darcy model as peak ground velocity increases, particularly affecting the upstream shell and clay core of the dam. This disparity becomes more pronounced as the input motion’s frequency content decreases, resulting in elevated pore pressures and slightly reduced vertical displacements in these regions.

Ultrasonic Analysis of the Influence of Structure on Tropical Soil Behavior

Ultrasonic Analysis of the Influence of Structure on Tropical Soil Behavior

Dynamic Mechanical Properties and Damage Evolution Behaviors of Ice-Rich Frozen Soil with Various Initial Moisture Contents

Dynamic Mechanical Properties and Damage Evolution Behaviors of Ice-Rich Frozen Soil with Various Initial Moisture Contents

Seepage and stability analysis of hydraulically anisotropic unsaturated infinite slopes under steady infiltration

An analytical model is derived for predicting the flow field and stability of an unsaturated infinite slope subjected to steady infiltration. The proposed model is novel because it accounts for the hydraulic anisotropy of unsaturated soil. The governing equation for steady-state seepage in an infinite slope is established in terms of matric suction under a constant surface flux boundary condition. On the basis of the available experimental findings on the hydraulic anisotropy behavior of unsaturated soils, the relative hydraulic conductivity for a soil under unsaturated conditions with respect to the soil at saturation is postulated to be a direction-independent scalar. This postulation simplifies the governing equation to a form that is directly solvable via the relative hydraulic conductivity and the saturated hydraulic conductivity tensor. To enable sophisticated applications, an exponential law and a power law that are well established in the unsaturated soil literature are used to relate the relative hydraulic conductivity to the matric suction and the effective degree of saturation, respectively. Closed-form solutions are derived for the matric suction, the flow net (potential function and stream function), and the effective degree of saturation. Analytical solutions are also derived for the soil unit weight and overburden stress. These solutions are incorporated into the unsaturated infinite slope stability formula constructed on a suction stress-based effective stress failure criterion. Hydraulic anisotropy has been shown to directly affect the flow field and the change in matric suction, which, in turn, drastically affects the slope safety factor against shallow landslides. This finding demonstrates that neglecting hydraulic anisotropy can cause a considerable overestimation of the safety factor, resulting in an unsafe slope stability prediction. The proposed model is useful for preliminary evaluation of the long-term stability of unsaturated slopes during wet periods and the antecedent slope conditions for shallow landslide initiation under transient infiltration.

Evolution of mechanical behavior in granular soil during fine particle loss simulated by salt dissolution: Insights from ring shear tests

Fine particle loss in soil is one of the main causes of slope instability and geotechnical structure failure. Loss of fines can cause instability in granular assembles by changing the fabric and microstructure of the sample. However, real-time monitoring of the evolution of mechanical behavior in granular soils during the particle loss process is still poorly explored. This study presents a novel approach by simulating fine particle loss through salt dissolution in ring-shear tests, offering real-time insights into the mechanical evolution of granular soils under realistic stress conditions. Meanwhile, the shear resistance, shear displacement, vertical displacement, salt content, and acoustic emissions were simultaneously recorded. The test results showed that the instability of the sample was triggered by the loss of fine particles. With a gradual loss of fine particles, both the vertical and shear deformations and the void ratio increased. The evolution of shear resistance in the sample can be divided into three stages: stress weakening, then strengthening, and finally recovery to the initial value. We infer that the evolution of shear resistance originated from the collapse and rearrangement of its granular fabric and microstructure. Additional evidence for this hypothesis was provided by high-frequency acoustic emissions (approximately 150 kHz), suggesting buckling of the force chains accompanying the particle loss process. Furthermore, the sample experienced greater shear deformations and stress weakening that developed under a larger initial fine content or a higher normal stress. This finding may provide valuable insights into the mechanical behavior of granular soil during the fine particle loss process.

Characterising geomaterial shakedown and related deformation accumulation from cyclic triaxial tests

Permanent deformation accumulation in soils and unbound granular materials under repetitive loading leads to surface rutting in roads and deterioration of track geometry in railways, eventually requiring costly and disruptive maintenance. Cyclic or repeated load triaxial tests are a convenient test method to characterise the permanent deformation behaviour of different soils under high numbers of load repetitions and a large volume of data is available. Existing empirical functions either take no account of shakedown, leading to an over-prediction of deformations at a high number of load cycles, or those that do take account of shakedown contain a high number of regression parameters that make them difficult to use. A simple empirical function with only one input parameter is proposed to characterise the accumulation of permanent axial strain in cyclic triaxial tests on a wide range of geomaterials undergoing shakedown deformations. It is shown to give predictions of a similar accuracy to existing functions at low numbers of load cycles and increased accuracy at high numbers of load cycles. It is shown to be applicable to soils ranging from a high plasticity clay to a rail ballast, across a range of stress states, stress history and strain levels provided that ratcheting deformations do not occur. The single input parameter has a physical meaning and is related to the permanent deformation required to reach the shakedown condition. Since the proposed function predicts the slowing rate of deformation accumulation towards shakedown not covered by the commonly-used existing functions, it could lead to more economical designs of applications involving high numbers of load repetitions. Its broad application to both coarse granular materials and fine-grained soils should streamline the design of applications involving layers of both these material types without the need to change empirical function.

A thermo-mechanical model for saturated and unsaturated soil–structure interfaces

Shear behaviour of soil–structure interfaces greatly affects the performance of geotechnical structures. The soil–structure interfaces in geothermal structures (e.g., energy pile and energy wall) are often subjected to varying temperature and suction conditions. However, there is no constitutive model to simulate the coupled effects of suction and temperature on the shear behaviour of soil–structure interfaces. In this study, a thermo-mechanical model was newly developed based on the bounding surface plasticity framework to predict the thermo-mechanical behaviour of saturated and unsaturated interfaces. A power function was used to calculate the degree of saturation at the interface and improve the evaluation of suction effects on interface shear strength. A linear relationship between temperature and interface critical state friction angle was proposed to incorporate thermal effects. New equations were also proposed to describe the critical state lines (CSLs) in the void ratio versus stress plane ( e-[Formula: see text]) and to model the shearing-induced deformation at various temperatures and suctions. The experimental data from different interfaces in the literature were used to evaluate the model capability. Comparisons between measured and computed results suggest that this model can well capture the coupled effects of temperature, suction, and net normal stress on the shear behaviour of interfaces.

On stress ratio equations in three-dimensional stress space for modelling soil behaviour

Constitutive models and failure criteria of soils, rocks, and other materials often need to be extended beyond the triaxial state where they are usually defined, for plane strain, axisymmetric, or three-dimensional analyses. This extension is commonly done by making the stress ratio a function of the Lode angle. This process turns two-dimensional yield, plastic potential, bounding, dilatancy and similar surfaces into three-dimensional shapes such as cones and bullets. The equations used have a range of shapes on the octahedral or π-plane between Mohr-Coulomb’s irregular hexagon and Drucker-Prager’s circle. Nine stress ratio generalization equations popular in soil mechanics are evaluated based on numerical stability, agreement with available data, and ease of implementation. The computed limits on their convexity, and the flexibility they offer in the calibration process are discussed. At the end, a new equation that satisfies all these criteria while remaining simple and easy to calibrate is proposed, implemented in a finite element model, and demonstrated to improve numerical stability and efficiency.

State parameter predictions based on cone penetration test simulated with MPM: an application to tailing deposits

The 'state parameter', which compares the current void ratio with the critical state void ratio, plays a crucial role in quantifying sandy soil behavior. In-situ methods, such as cone penetration tests (CPTs), can quantify the mechanical state of sand. However, establishing a direct relationship between cone resistance and the state parameter requires a complex back-analysis of the processes occurring in the soil during the test. Currently, a cavity expansion solution is being used to relate the state parameter to the cone resistance, necessitating the use of a calibrated scaling equation. In this study, 600 MPM CPT simulations are performed – which employ the critical state NorSand model - to derive a direct predictive equation for estimating the state parameter from CPT tests. This eliminates the need for a scaling equation. The predictive equation computes cone resistance as a function of the NorSand parameters and the state parameter of the soil. The accuracy of this predictive equation is subsequently evaluated by comparing the results against the chamber test data of tailings deposits, showing promising performance.

Dielectric and Emissivity Behavior of Soil of Rehand River of Surajpur Chhattisgarh at X-Band Microwave Frequency

Abstract: Microwaves are a form of electromagnetic radiation consisting of electric and magnetic fields oriented at right angles to one another. They operate within a frequency range of approximately 0.3 GHz to 300 GHz, corresponding to wavelengths from 1 meter to 1 millimeter. This paper explores a theoretical model for estimating the emissivity and dielectric constant of soil samples as they relate to moisture content. The emissivity of these soil samples was measured at X-Band frequencies for both vertical and horizontal polarizations. The results indicate that emissivity is higher for vertical polarization than for horizontal polarization. Additionally, the dielectric constant shows a gradual increase with rising moisture content.

Scaling law for correcting the gravel content effect due to scalping techniques by DEM investigations

Scalping techniques are commonly employed to handle oversized particles in gravelly soils for performing laboratory tests, which will cause significant gravel content (GC) effect on the predicted mechanical behaviors of prototype soils. To solve this obstacle, this study tries to establish the scaling law for correcting the GC effect, which controls the same equivalent skeleton void ratio between the prototype and model soils. The proposed scaling law characterizes the mechanical parameters using the newly introduced indexes including the degree of heterogeneity and the scaling factor for parameter A of the Harding equation. Then a series of DEM simulations of element tests were performed on sand-dominant gravelly soils to parameterize and check the applicability of the proposed scaling law. The simulation results show that both the converted shear responses and shear modulus reduction curves through the proposed scaling law are highly consistent with that of the prototype soils. This suggests that in dealing with deformation problems from small to medium strains, Rocha’s assumption is highly applicable for correcting the GC effect. When the adopted scalping techniques control the change in GC (ΔGC) below 20 %, the predicted liquefaction resistance will be very close to that of the prototype soils regardless of the earthquake magnitudes. However, when ΔGC is larger than 40 %, the prediction error in liquefaction resistance will be larger. Based on these simulation results, it is recommended that when selecting scalping techniques for laboratory tests on gravelly soils containing oversized particles, it is preferred that ΔGC be kept below 20 %.

Towards construction of embankment on soft soil: a comparative study of lightweight materials and deep replacement techniques

Planning embankments demands comprehensive studies to select suitable materials, enhance soil stability, ensure optimal performance, and comply with building code requirements and sustainability standards. This study offers an evaluation of various alternatives and their effectiveness for constructing embankments on weak soil using the 2D finite element software Plaxis 8. It highlights the convergence of different techniques, offering flexibility in selecting the optimal strategy for projects. The behaviour of multilayer clayey soil under an embankment of lightweight filling materials such as mixed sawdust or geo-foam and that carrying an embankment of traditional fill material improved by deep replacement techniques like concrete piles (CP), deep-mixing columns (DMC), stone columns (SC), and sand piles (SP) were compared considering factors like stress distribution, pore water pressure, and settlement of the soil. The results demonstrate that lightweight materials reduced settlement by 11–98% and stress by 5–89%, while deep replacement techniques reduced settlement by 8.5–75% and stress by 44–88%. Notably, the study underscores the effectiveness of DMC in promoting soil reuse compared to CP.

Salinity Effects on the Physicochemical and Mechanical Behavior of Untreated and Lime-Treated Saline Soils

Salinity Effects on the Physicochemical and Mechanical Behavior of Untreated and Lime-Treated Saline Soils

Digital image-based measurement of degree of saturation on moving soil

This paper presents a novel methodology that combines Particle Image Velocimetry - Numerical Particles (PIV-NP) and Short-Wave Infrared Spectral Imaging for the non-invasive measurement of displacements and degree of saturation on moving soils. This allows for continuous monitoring and visualization of soil behavior and provides valuable insight into the deformation patterns and moisture evolution. The method was applied to a small-scale dam failure experiment. The methodology offers an integrated, comprehensive, and non-invasive approach to investigating soil physical models by simultaneously measuring displacements, strains, velocities, and degree of saturation in soils in motion.

Investigation of Compressibility and Shear Strength Behavior of Soft Soil Stabilized by Bottom Ash and Waste Fishing Net

Investigation of Compressibility and Shear Strength Behavior of Soft Soil Stabilized by Bottom Ash and Waste Fishing Net

Dynamic response analysis of monopile-supported offshore wind turbine on sandy ground under seismic and environmental loads

Monopiles are the most widely adopted foundation type for Offshore Wind Turbines (OWTs) in shallow waters. With the expansion of the construction of OWT, the number of OWT farms in seismic regions increases globally including the coastal areas of Japan and China. It is necessary to evaluate the impact of earthquakes including the vibration and soil liquefaction on the OWTs supported by the monopile foundation, while the effects of liquefaction on offshore structures, especially for OWTs with monopiles, have not been sufficiently studied. This study investigates the seismic response of the monopile-supported OWTs with the use of an advanced soil model. A three-dimensional numerical model is built, and dynamic analyses are carried out using the OpenSees framework. The pressure-dependent multi-yield (PDMY03) constitutive model is used to simulate the dynamic soil behavior. The applicability of the large-diameter pile modeling method for proper soil-pile interaction modeling in this numerical analysis is first validated through centrifuge tests on monopiles subjected to lateral loading. The dynamic analyses are then carried out to demonstrate the seismic response of the entire OWT system. The numerical results indicate that the contribution of higher modes of vibration is becoming of increased importance for large wind turbines and soil-structure interaction plays a significant role in the dynamic response. Moreover, the monopile-supported OWT in dense sand deposits experiences substantial lateral displacement and rotation under the combined action of wind and earthquake loads when liquefaction occurs.

Investigating the geomechanical behavior and mechanism of clay stabilization with natural zeolite and nano-magnetite under accelerated curing conditions (ACC)

Chemical stabilization is a commonly used technique for ground improvement. Traditional methods of chemical soil stabilization rely on additives such as cement and lime, which are relatively expensive and not environmentally friendly. Therefore, using accessible natural pozzolans, such as zeolite, in soil stabilization is an effective and economical option. This study investigated the effect of zeolite and nano-magnetite on the geomechanical behavior of fine-grained clayey soil. Unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), and electrical conductivity (EC) tests were performed on both stabilized and unstabilized samples. The samples were cured under standard curing conditions (SCC) and accelerated curing conditions (ACC). The UCS and UPV results for the clay sample containing 5% zeolite and 1% nano-magnetite showed significant increases of 85% and 48% under SCC and 174% and 59% under ACC, respectively, compared to untreated clayey soil. Additionally, the clay mixture containing 5% zeolite and 1% nano-magnetite, which achieved the highest UCS and UPV values under ACC, exhibited increases of 166 kPa and 100 m/s, respectively, compared to SCC. Moreover, the EC value decreased by approximately 51% and 60% for the samples with the highest strength in SCC and ACC, respectively. Based on Scanning Electron Microscope (SEM) imaging and Energy Dispersive Spectroscopy (EDS) analysis, the impact of zeolite and nano-magnetite on improving compaction and promoting hydrothermal reactions was evident, supporting the higher geomechanical results obtained. Overall, the findings suggest that using zeolite and nano-magnetite offers a cost-effective and eco-friendly solution for stabilizing clayey soil in civil engineering projects.

The 9th Victor de Mello lecture: reflections and speculations

The paper reviews the published literature on some aspects of fabric and particle behaviour in cohesionless soils. It uses insights from Discrete Element Modelling and Microcomputed Tomography to speculate on reasons for the difference in behaviour observed between moist tamped and sedimented sands at the same global void ratio and stress state. It is suggested that inhomogeneities in the form of macrovoids in moist tamped samples trigger localisation, collapse and the development of a local scale chain reaction. It questions whether a similar sequence applies at the field scale and whether expansive partial drainage influences the rate of propagation of the chain reaction. The paper offers reasons why the use of critical state based on moist tamped samples to assess the stability of tailings, may not be the best approach, and suggests that identifying instability lines for sedimented samples at appropriate void ratios and principal stress directions, may be preferable. Critical state reflects behaviour at large strains where initial and evolving inhomogeneities affect identification of relevant void ratios; instability lines reflect behaviour at small strains where inhomogeneities probably initiate collapse. The paper emphasises the importance of spatial variations in local void ratios in loose material, the importance of anisotropy of collapse potential and of load-controlled rather that strain-controlled shearing.

Comparison of the efficacy of carbonation and conventional curing for remediation of copper-contaminated soils by ladle slag

Soil contamination poses an increasing challenge for global sustainable development. Traditional remediation methods, such as using ordinary Portland cement (OPC) for treating contaminated soils, are limited by high CO2 emissions, significant energy consumption, and natural resource depletion. A sustainable approach utilizing steel production waste (ladle slag, LS) to efficiently remediate copper (Cu)-contaminated soils was proposed in this study. The efficacy of this remediation using carbonation and conventional curing methods was compared. Cu-contaminated soils, spiked with varying initial concentrations, were treated with 10 % LS and subjected to both conventional and carbonation curing for different durations. Leaching behavior, strength development, and chemical and mineral properties of LS-remediated Cu-contaminated soils were assessed. The results demonstrated that both CO2 and conventional curing significantly reduced Cu leaching in contaminated soils by 4–5 orders of magnitude compared to untreated soils. CO2 curing achieved these reductions in a shorter time (56–72 hours) than conventional curing (28–56 days). Additionally, CO2 curing sequestered up to 8 % CO2 in the soils. However, higher Cu concentrations hindered carbonation reactions, lowering CO2 sequestration. While CO2 curing improved soil strength, increased initial Cu concentration diminished this effect. During CO2 curing, the formation of Ca- and Mg-carbonates contributed to microstructural densification and binding, thereby improving strength. These carbonates also encapsulated Cu, preventing its leaching. In contrast, the addition of Cu enhanced hydration reactions and improved the strength development of Cu-contaminated soils subjected to conventional curing. Conventional curing produced calcium aluminum silicate hydrate, which effectively bound soil particles, filled pores, and encapsulated Cu, reducing its leaching.