Soil Behavior Research Articles

Measuring shrinkage of expansive soils using a novel automated high‐frequency setup

AbstractSoil shrinkage characteristic curves are used to describe the shrinkage behavior and hydraulic properties of unsaturated soils. To construct soil shrinkage characteristic curves, a high‐data‐density measurement method is needed that relates water content to soil volume changes. We present a fully automated soil shrinkage measurement setup, based on the simplified evaporation method, to characterize the shrinkage behavior of undisturbed natural expansive clay soils. The high data density creates the opportunity to produce soil shrinkage characteristic curves without the need for a mathematical model. The technique allows for resaturation of the samples after drying, enabling differentiation between reversible and irreversible shrinkage. The setup consists of the commercialized HYPROP2 apparatus combined with optical distance sensors to measure the horizontal and vertical dimensions of the samples, yielding data on the sample volume, weight, and soil water suction. The measurement frequency is once per 10 min, and the measurement period is up to 4 weeks, providing a detailed time series of the drying and shrinkage characteristics. The setup can capture the different shrinkage phases and offers the opportunity to relate the soil shrinkage characteristic curve to soil water suction. The measurement data acquisition rate and accuracy enable detailed interpretation of soil water retention curves for nonrigid soils and are shown to be essential for understanding and quantifying the shrinkage potential of several types of deposits.

Enhancing Deep Excavation Optimization: Selection of an Appropriate Constitutive Model

To minimize the impact on nearby structures during deep excavations, choosing an appropriate soil constitutive model for analysis holds significant importance. This study aims to conduct a comparative analysis of various constitutive soil models—namely, the Mohr–Coulomb (MC) model, the hardening soil (HS) model, the hardening soil small strain (HSS) model, and the soft soil (SS) model—to identify the most suitable model for the lacustrine deposit. To implement these models, the soil’s index properties and mechanical behavior were evaluated from undisturbed soil samples. The numerical simulation and verification of these properties were carried out by comparing the laboratory test results with the outcome of the finite element method; the most suitable constitutive soil model for the soil was identified as the HSS model. Upon analyzing the wall deflection and ground settlement profiles obtained from respective constitutive models, it was observed that the HS and HSS models exhibit similar characteristics and are well-suited for analyzing typical lacustrine soil. In contrast, the MC and SS models yield overly optimistic results with lower wall deflection and ground settlement and fail to predict realistic soil behavior. As a result, this research highlights the significance of selecting the appropriate constitutive soil model and refining the parameters. This optimization process contributes significantly to the design of support systems, enhancing construction efficiency and ensuring overall safety in deep excavation projects.

Effects of elevated temperature and treatment duration on selected index and engineering properties of lateritic soils

Lateritic soils are important to various engineering applications, especially in tropical regions, where they serve as key components in road construction, embankments, and other geotechnical structures. This study investigated the combined effects of elevated temperature and heating duration on the index and engineering properties of lateritic soils derived from two distinct parent rocks (charnockite and quartzite) in Ado-Ekiti, Nigeria. Disturbed lateritic soil samples were heated in a furnace at various temperatures (100, 200, 300, and 400 °C) for two designated durations (2 and 3 h). Standard geotechnical tests were conducted to evaluate Atterberg limits, compaction parameters, and unconfined compressive strength. The results showed that elevated temperature led to a decrease in the plastic limit, liquid limit, plasticity index, optimum moisture content (OMC), and UCS for both soils, though the extent varied between the two parent rocks. For instance, at 400 °C for 3 h, the plasticity index decreased by 47.82% for charnockite-derived soil and 55.22% for quartzite-derived soil. At the same temperature for 2 h, it decreased by 38.79% for charnockite-derived soil and 48.92% for quartzite-derived soil. Similarly, UCS decreased by 29.83% for charnockite-derived soil and 25.97% for quartzite-derived soil at 400 °C for 3 h, while at 400 °C for 2 h, UCS decreased by 21.20% for charnockite-derived soil and 23.48% for quartzite-derived soil. Conversely, maximum dry density (MDD) increased with temperature, rising by up to 20.64% for charnockite-derived soil and 14.66% for quartzite-derived soil at 400 °C for 3 h, and by 18.29% for charnockite-derived soil and 12.62% for quartzite-derived soil at 400 °C for 2 h. Longer heating durations (3 h) generally caused more pronounced changes in soil properties compared to shorter durations (2 h). For instance, OMC decreased by 13.41% for charnockite and 14.18% for quartzite at 400 °C for 3 h compared to a 2-h duration. Statistical analyses indicated that temperature had a significant influence on most properties, while the effect of heating duration was less consistent. These findings highlight the need to consider both temperature and heating duration when evaluating the engineering behavior of lateritic soils exposed to elevated temperatures. Practical implications include potential adjustments in construction practices and design parameters for road construction and embankments in regions prone to high temperatures, such as those experiencing frequent forest fires.

Improving Shear Strength and Microstructural Behavior of Black Cotton Soil Treated with Construction Demolished Waste

With its expansive character and low bearing capacity, black cotton soil presents considerable obstacles to construction projects. These challenges can be difficult to overcome. There is a tendency for it to rise and compress in response to variations in the amount of moisture present, and it also has weak strength properties, which makes construction activities more difficult. This study explores the possibility of stabilizing black cotton soil with recycled construction and demolition (C&D) waste in order to address these issues. Various C&D waste materials, like concrete, bricks, mortar, and other debris, are examined for their potential to enhance the shear strength of black cotton soil. The paper assesses the effectiveness of incorporating C&D waste blends ranging from 5% to 25% to mitigate soil swelling and shrinkage with improve shear strength. Previous to determining the soil's shear strength, index properties were assessed. Unconfined compression strength tests (UCS) are carried out on compacted specimens handled with C&D waste blends, with curing periods of 1 day, 7 days, and 28 days at room temperature. A comparison investigation showed that there was a comparable increase in UCS and a decrease in axial strain at failure as the amount of C&D waste in the soil rose. Micro-analyses displayed that the main factors prompting the interacting behavior of soil amended with C&D waste include changes in the gradation, cohesiveness, and the interplay between the particles, the mineralogical makeup, and the elemental, chemical, and microstructural components. The research aims to offer insights into sustainable methods for strengthening the performance of black cotton soil while reducing waste generation in construction activities.

Influence of degree of saturation on the thermal conductivity of soils: Experimental and comparative model analysis

The thermal conductivity can characterize thermal behaviour of soils in different engineering studies: environmental, geothermal, geotechnical and buildings construction. However, accurately measuring and predicting this parameter poses a challenging task. Measuring this parameter can be very complex, considering several factors, such as soil heterogeneity and external climatic conditions. In addition, predictions models may not capture all the nuances of real-world soil conditions, leading to less accurate predictions of ?. The objectives of this paper encompassed two primary aspects: (i) Evaluation of laboratory tests of thermal conductivity of unsaturated soil. (ii) Assessment of five highly recommended soil thermal conductivity models to determine their validity and strengthen their trustworthiness. The studied material consisted of calcareous tufa locally available in Beni-Saf region (Algeria). The tested samples were compacted to the Standard and Modified Proctor Optimum (SPO, MPO) followed by drying periods under laboratory conditions. The thermal conductivity of samples was evaluated using transient method. The models’ predictive results of the thermal conductivity were assessed with different criteria such as Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), and Coefficient of Determination R². Furthermore, this work also attempts to deliver an in-depth discussion of the effect of degree of saturation Sr on the thermal conductivity of soils.

Three-Dimensional Spectral Element Method Implementation for Evaluating Rooted Soil Behavior in Slope Stability Analysis

Bioengineering techniques are being increasingly adopted as a sustainable solution to soil slope instability. Despite their recognized benefits, however, the mechanistic contribution of vegetation to slope stability remains inadequately understood due to the intricate nature of soil–root interactions and the complexity of root architectures. Most existing research predominantly offers qualitative assessments of vegetation effectiveness. This study aims to numerically substantiate the role of vegetation as a bioengineering technique for soil slope stabilization. Various plant species used commonly for soil stabilization were identified, and undisturbed soil samples were collected to quantify the shear strength parameters of the soils from both barren and vegetated slopes, along with root tensile strengths. A comprehensive topographic survey was conducted to capture the precise topography of the study area. Utilizing these primary data, in this work we develop 3D models for five representative plants within each species category and employ the Spectral Element Method (SEM), an advanced higher-order formulation of the finite element method (FEM), within the 3D domain to evaluate the factor of safety for the soil slopes. The SEM offers superior accuracy and stability in numerical computations. The results obtained through the SEM were corroborated through the FEM modeling and were found to be consistent with other established methodologies. This innovative approach of 3D SEM aims to quantitatively assess the impact of vegetation on soil slope stability and provide a more rigorous understanding of bioengineering applications in geotechnical engineering.

Multistep procedure for estimating non-linear soil response in low seismicity areas—a case study of Lucerne, Switzerland

SUMMARY The impact of non-linear soil behaviour on seismic hazard in low-to-moderate seismicity areas is often neglected; however, it may become relevant for long return periods. In this study, we used fully non-linear 1-D simulations to estimate the site-specific non-linear soil response in the low seismicity area, using the city of Lucerne in Switzerland as an example. The constitutive model considers the development of pore pressure excess and requires calibration of complex soil models, including the soil dilatancy parameters. In the absence of laboratory measurements, we mainly used the cone penetration test data to estimate the model variables and perform inversion for the dilatancy parameters. Our findings, using Swiss building code-compatible input ground motions, suggest a high probability of strong non-linear behaviour and the possibility of liquefaction at high ground motion levels in the case study area. While the non-linearity observations from strong-motion recordings are not available in Lucerne, the comparison with empirical data from other sites and other methods shows similarity with our predictions. Moreover, we show that the site response modelled is largely influenced by the strong pore pressure effects produced in thin sandy water-saturated layers. In addition, we demonstrate that the variability of the results due to the input motion and the soil parameters is significant, but within reasonable bounds.

Numerical simulation of rainfall-induced deformations of embankments considering the coupled hydro-mechanical behavior of unsaturated soils

This paper presents numerical simulations of the deformation response of unsaturated embankments subjected to rainfall infiltration using a coupled hydro-mechanical constitutive model for unsaturated soils. The constitutive model accounts for the influence of degree of saturation on the stress–strain behavior and the influence of void ratio on the water retention behavior. The constitutive model was implemented in the finite difference program FLAC, calibrated using triaxial test data, and validated using measurements of wetting-induced deformations of embankment models from centrifuge tests. The validation demonstrates that the constitutive model can capture the coupled hydro-mechanical behavior of unsaturated soils under wetting conditions. Simulations of the hydro-mechanical response of unsaturated embankments subjected to rainfall infiltration indicate that the differential settlement across the top surface of the embankment between the centerline and shoulder increases significantly during rainfall infiltration, which could result in severe damage to overlying transportation infrastructure. As the rainfall infiltration increases, shear strains accumulate and form a potential failure surface at a shallow depth of approximately 2 m from the slope surface. Insights into the hydro-mechanical response of unsaturated embankments subjected to rainfall infiltration gained will be useful for considering climate change effects in design and construction of compacted embankments.

Classification of expansive soils among problematic soils in the brazilian semiarid from artificial neural networks

The climatological and geomorphological conditions of the Brazilian semiarid region favor the formation of potentially expansive soils. The development of neural networks to identify and classify expansive soils in Pernambuco, and the need to export to soils across the semiarid region of Brazil is investigated in this study using a Multi-Layer Perceptron (backpropagation). The neural network was developed using 87 experimental data points, divided into three groups. The Training Group, consisting of 53 samples, using data inputs: sand percentage, clay percentage, plasticity index, activity index, and geological, pedological, and climatological classification. Selection Group, made up of 17 samples, was used to select the best network architecture, genetics algorithms formed of 7 inputs and 3 hidden nodes. The Test Group used 17 samples to evaluate the predictive accuracy of the expansion potential, obtaining an accuracy rate of 88,2%. This network was validated by applying it to 67 samples of problematic soils of the collapsible, expansive, and soft type from the Brazilian semiarid region, reaching an accuracy of 76,1%. Probabilistic Neural Networks were found to be efficient in evaluating the behavior of expansive soils, with the ability to deal with the absence of sample input data, demonstrating the ability to capture movement trends in the expansion of the soil surface, indicating the functions that introduce the effects of the composition potential on the expansion behavior, and determining the limit values of each of the input variables for the samples from the database used.

A New Model for Evaluating the Behaviour of Swelling Soils

In many areas around the world, there are clayey soils that have the potential to change their volume caused by the variation in their water content. Increasing or decreasing the water content caused the clayey soils to swell or shrink, respectively. This phenomenon may cause the uplifting and settlement of structures, which may lead to considerable financial damages. The estimation of swelling displacement without addressing the swelling rate have been published by several research works. This drawback leads to the development of a new model that takes into account the swelling behavior of soils with time. The model, which consists of two hyperbolic curves, was compared with swelling test results performed on soil samples taken from several locations in Israel. Data test results were used to compare the newly introduced model with other existing mathematical models found in the literature. This analysis shows that the new model represents more accurately the behavior with time of the swelling clayey soils measured in laboratory test results than the existing hyperbolic models.

Seismic response assessment of tapered piles in sandy soils: A numerical investigation

For the same volume, tapered (non-prismatic) piles have premium advantages over conventional (prismatic) cylindrical piles with respect to the axial and lateral load resistance and, thereby, are considered an economical alternative to prismatic piles. While previous investigations have studied the behavior of tapered piles subjected to different dynamic loading conditions, their seismic response has not yet received a comprehensive examination. This study aims to investigate the seismic response of tapered piles in sandy soils using non-linear three-dimensional (3D) finite element analyses. A total of 3084 cases were studied using MIDAS software to consider a wide range of parameters, including variations in soil density (Dr), taper angle (θ°), slenderness ratio (L/DAvg), and different earthquake recorded data. A parametric analysis was also undertaken to investigate the behavior of the pile lateral displacement, pile bending moment, and frictional resistance. The findings of the study reveal that tapering enhances the lateral stiffness of the pile, resulting in reduced lateral deflections and decreased sensitivity to changes in L/DAvg and ground motion intensity. Furthermore, under higher ground motion intensity, improved pile stiffness through tapering contribute to an increase in bending moments experienced by the pile. Another significant observation is the substantial improvement in frictional resistance due to soil densification. This emphasizes the critical importance of considering the soil behavior and its density in the design of pile foundations, particularly when aiming to withstand seismic loads effectively. These insights offer valuable guidance for designing pile foundations that can reliably endure the dynamic forces present during seismic events.

Effect of Tire-Rubber Inclusion on The Physical and Mechanical Be-havior of Granular Soils

Effect of Tire-Rubber Inclusion on The Physical and Mechanical Be-havior of Granular Soils

X-ray microstructural insight into the mechanical behaviour of ligth-weight cemented soils

Light-weight cemented soils (LWCS) – that is, materials prepared by mixing natural soil, water and cement with air foam, are characterised by a heterogeneous microstructure, consisting of large foam-induced voids distributed in a cemented porous matrix. The reduced volume weight coupled with a good mechanical strength makes LWCS suitable for many geotechnical applications. However, the role of the microstructure on their macroscopic mechanical behaviour is not completely clear. A novel experimental investigation on the mechanical response of LWCS under triaxial loading paths using in situ x-ray microtomography is presented here, focusing on the evolution of foam-induced porosity. The tomographies are acquired during the shear phase of multiple triaxial compression tests, performed at different confining stress levels. Image analysis is employed for obtaining porosity maps and incremental strain fields of the samples. At low confining stress, the sample deformation essentially consists in the progressive opening of sub-vertical dilatant fractures connecting the foam-induced voids. At higher confining stresses, localised compactions develop in the cemented matrix along the directions coherent with the deviatoric load path. The results presented above indicate that the deformation and failure mechanisms of LWCS strongly depend on the mean stress level.

Iron Behaviour and Soil Properties in Hydromorphic Soils of Beni Moussa, Tadla Plain, Morocco

Abstract This study aims to determine the behaviour of iron and its relation to the physicochemical properties in the hydromorphic soils of the Tadla plain (Morocco). An extensive analysis using Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) from a statistical perspective was employed to ensure a comprehensive examination. The results reveal that the organic matter (OM) shows very high values, likely due to the collected samples near the sewerage network. Magnetic susceptibility (MS) measurements indicate that all the samples have positive and low values, indicating an abundance of paramagnetic minerals (such as ilmenite, siderite, and clay minerals). The iron concentration [ppm] increases from the top to the bottom of the Rivers, suggesting migration in a reduced form. Pearson’s correlation coefficients indicate that OM is positively correlated with cation exchange capacity (CEC) (r = 0.83) and electrical conductivity (EC) (r = 0.85) but negatively correlated with MS (r = –0.57) and iron oxide (r = 0.42). Calcium carbonate content (CaCO3) is positively correlated with sand (r = 0.49), but negatively with MS (r = –0.7). Iron (Fe) is positively correlated with frequency-dependent (FD) (r = 0.7), but negatively with sand (r = –0.608). Clay is strongly negatively correlated with silt (r = –0.88) and oxalate extractable iron oxides (Feo) (r = –0.55), respectively. These findings suggest that the physicochemical features of Beni Moussa hydromorphic soils are strongly linked and that iron in the soil is required for the stability of specific soil components.

Performance and behaviour of prebored and precast pile with floating pile tip based on A full-scale field static axial load test

This study investigates the load transfer mechanism of a Prebored and Precast pile (PP pile), constructed installed in accordance with the rules applicable to the Hyper-Straight pile method (HS pile), in clay soils. While the HS pile method, developed in Japan, typically results in high bearing capacity piles in various soil types, its performance in clay soils remains understudied. Our research focuses on a unique configuration where the pile tip “floats” within a soil–cement mixing (SCM) column near the bottom of the borehole, a condition that significantly influences the system’s performance.We conducted a full-scale axial static load test on a 500 mm diameter and 140 mm thickness straight shaft precast prestressed concrete spun pile. The pile was instrumented with vibrating wire strain gauges (VWSG) and displacement measuring devices (tell-tales), embedded 15 m deep in a 750 mm diameter SCM column (15.75 m long). The pile tip was positioned 75 cm above the bottom of the borehole, creating a floating condition within the SCM material. Both the pile and the surrounding SCM were instrumented to provide comprehensive data on the system’s behavior.The test involved two loading–unloading cycles. The 1st Cycle reached a maximum load of 3627 kN, resulting in a 75.52 mm pile head settlement. The 2nd Cycle achieved a maximum load of 4181 kN, leading to a 118.04 mm pile head settlement. In the 1st Cycle, we observed upward movement of the SCM material around the shaft after the pile skin friction reached its maximum capacity. Stress at the pile tip exceeded the unconfined compressive strength of the SCM material, indicating potential local shear failure.Contrary to expectations based on HS pile performance in other soil types, the ultimate bearing capacity of our pile was determined to be 2000 kN, comprising 545 kN from skin friction and 1455 kN from end bearing. This result aligns more closely with the behavior of conventional bored pile rather than the “hyper” capacity typically associated with HS pile. Consequently, we classify our pile as a “prebored and precast pile,” like systems used in China and Korea.Our study concludes that the strength of the SCM material and the pile tip location significantly influence the pile’s bearing capacity in clay soils. These findings highlight the critical impact of soil type on the performance of piles constructed using the HS method. The observed behavior suggests that current design methods for HS pile may overestimate capacity in clay conditions, emphasizing the importance of soil-specific analysis and testing.This research contributes to the understanding of PP pile behavior in clay soils, providing valuable insights for geotechnical engineers. It underscores the need for refined prediction models and design methods specific to these soil conditions, paving the way for more accurate and reliable foundation designs in regions with predominant clay soils.

Shear constitutive model for various shear behaviors of landslide slip zone soil

Shear constitutive model for various shear behaviors of landslide slip zone soil

Determining the Effects of Operational Parameters and Geotechnical Conditions on the Behavior of Soil–Cement Columns Using a Small-Scale Physical Model in Sandy Soil

Determining the Effects of Operational Parameters and Geotechnical Conditions on the Behavior of Soil–Cement Columns Using a Small-Scale Physical Model in Sandy Soil

Bayesian-Based Approach in Soil Characterization for Tophole Design

Summary This paper addresses Bayesian-based data-driven site characterization (DDSC) methods for estimating soil parameters used in tophole casing design. Different models are applied to data sets of piezocone tests (CPTu) conducted in Brazilian fields, and their performance is compared to some characterization techniques currently used by the oil and gas industry. Regression models are crucial for soil characterization for tophole casing design. Data-driven methods consist of a powerful tool for this purpose, allowing handling uncertainties originating from soil variability. This paper addresses regression models devoted to sparse data, namely geotechnical lasso (Glasso) and Gaussian process regression (GPR) from a Bayesian perspective considering prior knowledge of site information. This approach provides statistical information on soil parameters like undrained shear strength, supporting structural analysis of wellhead systems, and conductor/surface casing strings. Data sets were collected from in-situ CPTu tests conducted in the Campos basins in eastern Brazil. The first case study addressed primary CPTu data, including cone tip resistance, friction sleeves, and total pore pressure, to characterize undrained shear resistance as a random variable. In this context, the parameter was modeled using Phoon’s modified Bartlett test to calculate sample sizes that ensure stationarity. This approach presented relevant results in assessing the probability of failure for conductor and surface casing design based on the operator’s internal design criteria. In these applications, more robust techniques were used to improve data characterization. Glasso and GPR models are used to model parameter tendencies and evaluate the random data. These methods differ in prior probability density functions adopted—Laplace and Gaussian, respectively—and they are compared with regression techniques widely used in design practice. All the models were trained to estimate undrained shear resistance. Preliminary results confirm that the technique improves the characterization of soil strata and undrained shear strength, with a beneficial effect on the analysis of offshore tophole structural design cases. Some metrics, such as mean absolute error (MAE) and root mean squared error (RMSE), indicate that GPR outperforms other methods. This is an innovative methodology applied in real-case scenarios with data ceded from the partner operator. The formulation evaluates uncertainties associated with the spatial heterogeneity of the material, continuously improving robustness with each new project data. This enables a better understanding of soil behavior in specific oil fields and can assist the decision-making process in well design, improving operational safety. Furthermore, the results of the statistical modeling support reliability-based analysis to deliver probability-based indicators for well integrity design.

An experimental and theoretical study on the creep behavior of silt soil in the Yellow River flood area of Zhengzhou City

We took the silt soil in the Yellow River flood area of Zhengzhou City as the research object and carried out triaxial shear and triaxial creep tests on silt soil with different moisture contents (8%, 10%, 12%, 14%) to analyze the effect of moisture content on silt soil. In addition, the influence of moisture contents on soil creep characteristics and long-term strength was analyzed. Based on the fractional derivative theory, we established a fractional derivative model that can effectively describe the creep characteristics of silt soil in all stages, and used the Levenberg–Marquardt algorithm to inversely identify the relevant parameters of the fractional derivative creep model. The results show that the shear strengths of silt soil samples with moisture contents of 8%, 10%, 12% and 14% are 294 kPa, 236 kPa, 179 kPa and 161 kPa, respectively. The shear strength of silt soil decreases with increasing moisture content. When the moisture content increases, the cohesion of the silt soil decreases. Under the same deviatoric stress, the higher the moisture content of the silt soil, the greater the deformation will be. The long-term strength of silt soil decreases exponentially with the increase of moisture content. If the moisture content is 12%, the long-term strength loss rate of silt soil is the smallest, with a value of 32.96%. The calculated values of our creep model based on fractional derivatives have a high goodness of fit with the experimental results. This indicates that our model can better simulate the creep characteristics of silt soil. This study can provide a theoretical basis for engineering construction and geological disaster prevention in silt soil areas in the Yellow River flood area.

Development of the triaxial equipment: a state of art

Triaxial shear testing is one of the most crucial investigations in geotechnical laboratories. It is essential for designing specific projects and understanding soil behavior in geotechnical engineering. Since Casagrande developed the modern shear apparatus at Harvard University, it has been refined to provide a more accurate characterization of shear strength behavior. This research paper aims to offer a concise overview of triaxial equipment development, focusing on apparatus that is easy to set up, prepare, and operate reliably, while remaining cost-effective. The primary objective is to contribute to the accurate determination of suitable techniques and devices that meet specific testing objectives. We review the theoretical background of both the triaxial apparatus and the direct shear box and illustrate the basic working principles of various volume change measurement techniques using triaxial devices. We also present different operational principles employed in designing volume change devices for soil testing. Our analysis reveals that some of these devices require complex operational techniques and equipment, making them challenging to use for repetitive testing. Consequently, we conclude that the ideal volume change device for soil mechanics testing should prioritize robustness and ease of operation.