Shear Strength Of Soil Research Articles

Evolution of the Shear Strength and Microstructure of Undisturbed Lateritic Soil under the Influence of Alkali Contamination

Abstract With the progression of industrialization, alkaline contamination has become an increasingly serious issue in soil environments, significantly impacting the engineering properties and microstructure of soils. Undisturbed lateritic soil samples were immersed in sodium hydroxide solutions with pH values of 8.8 and 11.4, as well as in deionized water with a pH of 7.0, for soaking times of 1 day, 7 days, and 28 days. The influence of alkali contamination on the shear strength of the lateritic soil was quantified through consolidated slow shear tests. Additionally, scanning electron microscopy, thermogravimetric analysis, nitrogen adsorption tests, mercury intrusion porosimetry, and laser particle size analysis were employed to thoroughly explore changes in micromorphology, mineral composition, pore structure, and particle size of samples, aiming to establish a microstructural evolution model. At pH = 8.8, the cohesion and friction angle of samples are higher than that soaked in water and increase with the soaking time. At pH = 11.4, the cohesion significantly increases on the 1st day, relatively decreases by the 7th day, but remains higher than that at pH = 8.8. Subsequently, with an increase in soaking time, the cohesion continues to rise. The alkali solution dissolves the kaolinite minerals causing the pore structure to collapse. The elevated shear strength at pH = 8.8 is attributed to smaller particles tightly locking together to form a more stable structure. At pH 11.4, the significant increase in cohesion after 1 day is not only attributable to the reasons mentioned above but also attributed to the aluminum silicate gel’s bonding effect on particles. By the 7th day, gel dissolution reduces soil cohesion.

Geotechnical characterization of tropical soil via laboratory testing

This manuscript presents the evaluation of relevant geotechnical properties of the soil profile in the northern region of Campinas, which are important for geotechnical engineering practice and development in São Paulo State. Disturbed and undisturbed samples from the subsoil were collected through the excavation of inspection shafts at the experimental site for Soil Mechanics and Foundations research at the State University of Campinas, located at the Faculty of Civil Engineering, Architecture and Urbanism (FEC). Laboratory tests were conducted, including soil characterization, soil shear strength, soil compressibility, soil permeability, and soil suction tests. The characterization tests indicated that the upper soil layer is subject to surface effects and more direct weathering action, with noticeable variations in the liquid and plasticity limit values. The permeability test results showed no significant variation between the values obtained in the vertical and horizontal directions. The soil-water characteristic curves for the studied profile were bimodal, typical of tropical soils with macro and microaggregated structures.

RegionGrow3D: A Deterministic Analysis for Characterizing Discrete Three‐Dimensional Landslide Source Areas on a Regional Scale

AbstractRegional‐scale characterization of shallow landslide hazards is important for reducing their destructive impact on society. These hazards are commonly characterized by (a) their location and likelihood using susceptibility maps, (b) landslide size and frequency using geomorphic scaling laws, and (c) the magnitude of disturbance required to cause landslides using initiation thresholds. Typically, this is accomplished through the use of inventories documenting the locations and triggering conditions of previous landslides. In the absence of comprehensive landslide inventories, physics‐based slope stability models can be used to estimate landslide initiation potential and provide plausible distributions of landslide characteristics for a range of environmental and forcing conditions. However, these models are sometimes limited in their ability to capture key mechanisms tied to discrete three‐dimensional (3D) landslide mechanics while possessing the computational efficiency required for broad‐scale application. In this study, the RegionGrow3D (RG3D) model is developed to broadly simulate the area, volume, and location of landslides on a regional scale (≥1,000 km2) using 3D, limit‐equilibrium (LE)‐based slope stability modeling. Furthermore, RG3D is incorporated into a susceptibility framework that quantifies landsliding uncertainty using a distribution of soil shear strengths and their associated probabilities, back‐calculated from inventoried landslides using 3D LE‐based landslide forensics. This framework is used to evaluate the influence of uncertainty tied to shear strength, rainfall scenarios, and antecedent soil moisture on potential landsliding and rainfall thresholds over a large region of the Oregon Coast Range, USA.

Analysis on slope stability by anchorage based on soil creep with flood effect

In order to analyze the adverse effect of flood affection on slope stability, the analytical expressions of buoyancy force and capillary force, hydrodynamic pressure and impact force, and scour erosion were proposed based on the aging characteristics of soil shear strength and limit equilibrium theory. According to the load combination and flood action, shear failure occurs preferentially at the foot of slope. Then, the plastic zone continues to extend upward to produce traction landslide disaster mode. Furthermore, the power function relation between shear strength index and time was established. The nonlinear accelerated creep model was also obtained. At the same time, the safety factor formula for flood loading effect slope aging stability, the time-varying characteristic value of anchor force and the compensation value of anchor force were also obtained and used to research sliding mechanism. In addition, the numerical calculation example shows that the slope safety factor decreases by more than 20 % considering the effect of flood ascending scour and impact, and the compensation value of anchorage force increases obviously with time increasing. Simultaneously, the change rate of compensation value of anchorage force increases nonlinearly with the increase of design safety factor.

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.

Utilising the Ipzo parameter for more reliable estimates of undrained shear strength directly from CPTU data in saturated natural clay-like soils

Ramsey and Tho illustrated the ability of the Ipzo parameter to estimate plasticity index in a wide range of saturated natural soils and highlighted the potential of the Ipzo parameter for improving the reliability of estimations of other soil properties affected by plasticity index. In this note, an improved method is proposed for estimating undrained shear strength in clay-like soils using CPTU data, where clay-like is defined as Ipzo ≥ 12%. The improved method is validated using a geographically and geologically diverse “Nkt1-database” comprising 54 anisotropically consolidated undrained triaxial compression tests, with complementary CPTU measurements from 36 geological units at 18 globally distributed marine sites.

Experimental study on the effect of freeze–thaw cycles to the cohesion and moisture content of geogrid reinforced silty clay

The freezing and thawing cycle is one of the primary causes of damage and instability to buildings in seasonal frost regions. During this process, the mechanical properties of soil are affected, leading to settlement, cracking, or deformation of infrastructure. Mitigating or reducing the occurrence of building frost damage in seasonal frost regions has become an important subject of study. Freeze–thaw (F–T) action will influence the distribution of moisture inside the reinforced soil and change the strength of thawing soil, which is closely related to the main influencing factors, such as initial moisture content, compaction degree, reinforced spacing, number of freeze–thaw cycles (FTC), freezing temperature, and effective vertical stress. Cohesion is an important index to determine the shear strength of clay, which is important to analyze the change in cohesion after F–T. Meanwhile, cohesion is closely related to soil moisture content. This study conducted orthogonal experiments on these primary influencing factors (6 factors at 5 levels) through FTC tests, triaxial tests, and moisture content tests to determine the undrained cohesion and moisture content of the clay after FTC, thereby establishing the influence of reinforcement on soil strength under freeze–thaw conditions. Based on the experimental results, SPSS software was used to fit the regression equations of undrained cohesion and moisture content expressed by the main influencing factors at different heights of the clay. Optimization options for the main influencing factors were obtained with Matlab software when the highest undrained cohesion values 6.8, 10.6, 8.9 kPa and lowest moisture content values 24.0%, 24.3%, 26.2% appeared in upper, middle and lower parts of the testing clay structure respectively, in conditions of − 15 °C freezing temperature and 5 times FTC. And determined the optimal combinations of moisture content, reinforcement spacing, compaction density, and vertical load at different heights. Decreasing reinforced spacing in silty clay was beneficial for liquid underwater seepage after F–T. The redistribution of internal moisture in the soil sample strengthened its undrained cohesion, thereby increasing the soil's shear strength. Comparing reinforcement conditions at different locations, it was found that when there were 3 layers of reinforcement with a spacing of 150 mm between them, this spacing was optimal. It played a significant role in improving the soil's shear strength and enhancing its bearing capacity. For reinforced clay itself, the order of the main factors influencing the undrained cohesion of soil after F–T, from high to low, was initial moisture content, reinforced spacing, and compaction degree.

Hybrid artificial neural network models for bearing capacity evaluation of a strip footing on sand based on Bolton failure criterion

This paper employs the Bolton failure criterion, incorporating strength-dilatancy relationships, to analyze the bearing capacity factor of a strip footing on dense sand. Utilizing finite element limit analysis (FELA) based on the lower and upper bound theorems, the study presents the results as average bound solutions. By using the Bolton model, the b parameter is first calibrated and found that it should be about 3.50 to align the ultimate bearing capacity (qu) from FELA to have a good agreement with that from experimental test results from previous studies. The influence of parameters relevant to the Bolton failure criterion is analysed, showing that an increase in relative density (DR) significantly affects the variation in the bearing capacity factor (Nγ) at higher Q values, while lower Q values inhibit dilatancy due to soil crushing. The width of the strip footing (B) has a decreasing effect on Nγ at higher Q values, and the unit weight (γ) changes minimally impact Nγ within the range of 16–22 kN/m3. Additionally, an increase in the critical state friction angle (ϕcv) consistently increases Nγ, highlighting its direct correlation with soil shear strength. A hybrid artificial neural network (ANN) model integrates machine learning with four optimization algorithms: Imperialist Competitive Algorithm (ICA), Ant Lion Optimization (ALO), Teaching Learning Based Optimization (TLBO), and New Self-Organizing Hierarchical Particle Swarm Optimizer with Jumping Time-Varying Acceleration Coefficients (NHPSO-JTVAC). Comparative rank analysis of hybrid ANN models based on the selection of the optimal number of hidden neurons demonstrates that the ANN-TLBO model excels in predicting the bearing capacity factor, achieving a score of 48. This conclusion is corroborated by an error heatmap matrix, which indicates a minimized percentage of error relative to other hybrid ANN models. Importance analysis identifies particle crushing strength (Q) as the most significant factor influencing the bearing capacity factor (Nγ).

Mechanical and hydraulic characteristics of unvegetated or vegetated loess soils amended with xanthan gum

With the development of western and central China, the increasing construction of transportation infrastructures (e.g., roads, railways, etc.) has been producing a large number of man-made slopes in loess regions. Biopolymer as an eco-friendly stabilizing material, has a great potential to amend soils for the purpose of ground improvement and slope stabilization, with its application in vegetated soils particularly at the initial growing stage to support vegetation growth as well as offer reinforcement to unprotected soils being reported recently. In the current study, the contribution of xanthan gum (XG) to both mechanical and hydraulic behaviors of the unvegetated and vegetated loess soils subjected to climatic wetting–drying cycles under the impacts of degree of compaction and biopolymer content are explored, whilst the effectiveness of the two XG-based soil reinforcing methods (with and without vegetation) are compared. Results indicate that XG treatment improved the water-retention capacity of loess soils to an extent that even the degradation of water retention upon initial wetting–drying cycles could be mitigated particularly at higher degrees of compaction. The strengthened shear resistance of loess soils was observed, mainly attributed to the increased soil cohesion, whilst the friction angle remained almost constant. The unvegetated loess soils basically had an increased cohesion proportional to the XG content up to 1.00% of the dry soil mass, whilst the vegetated soils had the highest soil cohesion at a fixed XG content of 0.50% which corresponded to the mostly promoted vegetation growth. Although a dense soil structure inhibited the seed germination and growth of sprouts and roots, it contributed to the overall shear strength of the vegetated soils similar to its effect on the unvegetated soils. XG amendment outperformed planting vegetation at enhancing soil shear strength at a degree of compaction of 95% (comparable to those adopted for design of highway subgrade), whilst providing XG in combination with vegetation was able to result in a more sizable strength increment over the summation of gains in strength by utilizing XG and vegetation separately, suggesting the considerable potential of XG in assisting vegetated soils for ecological slope stabilization. The results obtained from the current research support the broader usage of biopolymers (either used alone or in combination with vegetation) as reliable geotechnical engineering materials in practical implementations.

Investigation of planar sliding deformation and analysis of the damage mechanism of a rocky landslide in Yaoping triggered by highway excavation in Hubei, China

During projects to build roads in China's mountainous areas, which are often characterized by the poor stability of rocky slopes, cases of deformation damage occur frequently. Because of the wide distribution of rocky landslides in the smooth layer, the unavoidable perturbation caused by engineering construction and the seriousness of landslide disasters, the destruction of this type of landslide and the research into prevention of the mechanism cannot be ignored. On 6 February 2023, a rock slide occurred in Yaoping village, Hubei Province, China. Using field investigations, Google satellite images, unmanned aerial vehicle photography, indoor testing and numerical simulations, we analysed the geological situation, deformation characteristics, damage process and triggering mechanism. The results show that the Yaoping landslide is a typical downward plane-sliding rock slide induced by the excavation of a highway. When strain softening occurs, the shear strength and friction coefficient of the slip zone soil are significantly reduced. Excavation caused the factor of safety of the slope to decrease substantially, with a maximum decrease rate of 60.7%. Excavation is considered to be the extrinsic factor that triggered the occurrence of the Yaoping landslide, while the reduction of landslide resistance caused by strain softening of the soil in the slip zone is the intrinsic direct factor that led to the occurrence of this type of landslide. The Yaoping landslide has obvious traction landslide characteristics. The landslide from deformation to destruction has four stages: creep at the leading edge of the landslide; traction deformation in the middle and back of the landslide; slip belt softening; and integral sliding. The prevention and control of this type of landslide requires a larger scope and depth of investigation, in order to identify in advance the possible soft surface in the rock layer, to speculate on the possible formation of landslide destruction mode, and to determine the support scheme and scope according to the geological conditions of the slopes on both sides of the highway. The slip zone soil of the Yaoping landslide was used to obtain the strength index of slip zone soil, which provides data support for the overall deformation characterization of the landslide. The results can provide a reference for the risk management and prevention of rock slides caused by human engineering activities during the excavation of roads.

SOIL IMPROVEMENT IN PROBLEMATIC BLACK COTTON SOIL BY USING DRY KOTA STONE SLURRY AND FLY ASH-A STATE OF ART OF REVIEW

Black Cotton Soil (BCS) is particularly rapid-expanding and swelling when it meets water. This trait of soil results in extremely low soil strength and other attributes. Soil stabilization by various stabilizers is required to enhance its characteristics. Stabilization is a technique used to improve the soil's structural integrity. Soil stabilization raises the subgrade's load-bearing capacity, allowing it to better support the pavement and foundation. This is accomplished by increasing the soil's shear strength and regulating its shrink-swell qualities. Expansive soils could have their engineering qualities enhanced via several different means. The problematic soils are either excavated and replaced with excellent, higher-quality material, or treated with an additive. This paper demonstrates an analysis for soil improvement in problematic BCS by using dry Kota Stone Slurry (KSS) and Fly Ash (FA). FA is a byproduct of coal combustion in thermal power plants. It consists of fine particles that are carried away with the flue gases during the combustion process. The findings highlight its potential to address soil-related issues, enhance agricultural productivity, and contribute to sustainable land utilization practices.

Application of recycled lignin powder as a sustainable additive for soil improvement against water resistance

To evaluate the engineering performance against water resistance of lignin-modified soil, unconfined compressive strength (UCS) tests and direct shear tests were conducted on silty sand modified with varying lignin contents (2%, 5%, 8%, 12%, and 15%) following wet-dry cycles. The results demonstrate that 8% lignin-modified soil has the highest UCS and shear strength. The addition of lignin to soil enhances its wet-dry durability, with soil modified by 8% lignin exhibiting the highest durability. The structural properties of lignin-modified soil subjected to wet-dry cycles can be quantified using a combined structural stability index and structural variability index. A model relevant to the structural properties was proposed to predict the shear strength of lignin-modified soil following wet-dry cycles. Notably, the addition of lignin to silty sand does not result in the formation of new minerals, indicating that lignin addition is an environmentally-friendly soil treatment.

Mineralogical and Engineering Properties of Soils Derived from In Situ Weathering of Tuff in Central Java, Indonesia

This paper presents the results of borehole investigations and laboratory tests carried out to characterize the soils derived from in situ weathering of tuff in Central Java, Indonesia. The 70 m thick weathering profile of the Quaternary tuff consisted of residual soil and completely to highly decomposed rocks. The relatively low dry unit weight and cohesion but high water content, porosity, plastic and liquid limits, and angle of internal friction of the soils in the present study were related to the dominance of halloysite clay minerals. The established relationships to predict soil shear strength parameters from the soil plasticity index and standard penetration test (SPT) N-values were examined, and linear and non-linear relationships for soils derived from in situ weathering of tuff were proposed.

Shear Strength and Collapsibility of Gypseous Soil Improved by Nanomaterials

Shear Strength and Collapsibility of Gypseous Soil Improved by Nanomaterials

Basalt Fibers versus Plant Fibers: The Effect of Fiber-Reinforced Red Clay on Shear Strength and Thermophysical Properties under Freeze–Thaw Conditions

Freeze–thaw cycling has a significant impact on the energy utilization and stability of roadbed fill. Given the good performance of basalt fiber (BF) and plant fiber (PF), a series of indoor tests are conducted on fiber-reinforced red clay (RC) specimens to analyze the shear strength, thermophysical, and microstructural changes and damage mechanisms of the RC under the freeze–thaw cycle–BF coupling, meanwhile, comparing the improvement effect of PF. The results indicate that the RC cohesion (c) first increases and then decreases with the increasing fiber content under BF improvement, reaching the maximum value at the content of 2%, and the change in the internal friction angle (φ) is relatively small. As the number of freeze–thaw cycles increases, cohesion (c) first decreases and then gradually stabilizes. The thermal conductivity increases with increasing moisture content, and the thermal effusivity increases and then decreases with increasing moisture content and fiber content. The heat storage capacity reaches the optimum level at a moisture content of 22.5% and a fiber content of 1%. Microanalysis reveals that at 2% fiber content, a fiber network structure is initially formed, and the gripping effect is optimal. The shear strength of PF-improved soil is higher than that of BF at a fiber content of 4–6%, and the thermal conductivity is better than that of BF. At the same fiber content, the heat storage and insulation capacity of BF-improved soil is significantly higher than that of PF.

Evolution of Soil Pore Structure and Shear Strength Deterioration of Compacted Soil under Controlled Wetting and Drying Cycles

This study investigates the evolution of soil pore structure and shear strength deterioration in compacted clayey soil under controlled wetting and drying (wd) cycles, which are expected to become more frequent due to climate change. Thirty soil samples were compacted at optimal moisture content and 90% maximum dry density. These samples were then subjected to 0, 1, 5, 10, and 15 controlled wd cycles from saturation to the wilting point, and volumetric changes were recorded during each cycle. After the wd treatment, the soil samples were scanned using X-ray computed tomography (CT) at 50 μm resolution and then sheared under unconsolidated–undrained and consolidated–undrained conditions in a triaxial test. Significant shrinkage and swelling of soil samples were observed during wd cycles, with average volumetric strain fluctuating between +12% at saturation and −5% at the wilting point. X-ray CT visualisation and analysis revealed higher porosity, more prominent pores, and increased pore length in soil samples with increasing wd cycles. Both undrained and effective soil shear strength markedly decreased with increasing wd cycles. CT-derived macroporosity and pore length were significant predictors of the soil’s undrained and effective shear strength when exposed to wd cycles. The findings emphasise the considerable impact of climate change, specifically wd cycles, on clayey soil, highlighting the need for consideration in the design of earth-based infrastructure.

Stabilizing fine-grained soil by electrically injecting Ca2+, CO32-, and HPO42- ions

This paper presents a new technique that can electrically inject stabilizing ions, which can be used to stabilize soil. Other processes also occur simultaneously during treatment such as electrolysis, dissociation, sorption, and exchange mechanisms, etc. The aim of the research is to evaluate the effectiveness of the injection of stabilizing ions (Ca2+, CO32-, and HPO42-) in enhancing the shear strength of fine-grained soils. The shear strength of the soil increased up to 127% after treatment when measured near the anode and up to 495% when measured near the cathode. The results show that the proposed method can significantly increase soil strength; hence, it overcomes bearing capacity problems in soft fine-grained soils with low hydraulic conductivity.

Optimasi Desain Geometri Lereng Material Old Dump Pada Usaha Penggalian Ulang Pit X PT. Bukit Asam Tbk

In doing slope design, it is necessary to pay attention to slope geometry and soil shear strength. Determination of slope geometry design also considers the balance between height and slope and production benefits. Research was conducted to analyze slope stability through physical and mechanical properties testing, limit equilibrium, and probabilistic Monte Carlo methods. The surface area of the Overburden stripping area in the 2024 RKP design is 8,172.79 m2. The production target is 2,000,000 tons of coal with a volume of overburden material that must be stripped of 29,000,000 BCM and obtained a Stripping Ratio value of 14.5. The results of the evaluation of the overall slope of the Old Dump material with an overall slope height of 66.582 m, a slope width of 447.69 m, an overall slope of 8.32˚ and a bench width of 25 m, a bench height of 6 m with a comparison ratio of 1:3 and a single slope angle of 18.43˚. Then the redesign was carried out and obtained recommendation results of 64.799 m overall slope height, 303.33 m slope width, 13.02˚ overall slope, and 25 m bench width, bench height at elevation 131-110 of 8 m with a comparison ratio of 1:2, single slope 26.57˚ and at elevation 110-50 of 8 m with a comparison ratio of 1:1.5, single slope 33.69˚.

Environmental Importance of Mulberry: A Review

Mulberry is a woody, deciduous tree that is economically important. It is regarded as a distinctive plant on the planet due to its widespread geological distribution across continents, ability to be cultivated in various forms, multiple uses of leaf foliage and positive impact in environmental safety approaches such as ecorestoration of degraded lands, bioremediation of polluted sites, water conservation, soil erosion prevention, and enhancement of air quality through carbon sequestration. Mulberry has a robust root system. Mulberry root systems can significantly improve soil shear strength and anti-erosive capacity. Mulberry plantations are extremely effective in suppressing sand storms and conserving water and soil. The review investigates the role of mulberry trees in carbon sequestration, ecorestoration, soil and water conservation, bioremediation of heavy metals and afforestation.

Shear strength equation of soils in a wide suction range under various initial void ratios

AbstractShear strength equation is a basic theory for solving many geotechnical engineering problems. Although the shear strength equation has received widespread attention, shear strength of clay under wide suction range and different initial void ratio conditions cannot be well predicted. This study aims to establish a new strength equation applicable to soils within a wide suction range. Considering the capillary and adsorptive parts of soil–water interactions, a cohesion expression related to the degree of adsorbed water saturation Sra and the effective stress related to the degree of capillary water saturation Src are proposed. After that, based on the Mohr–Coulomb theory, a shear strength equation of unsaturated soils in a wide range of suction under various is proposed. Five parameters are included in the equation. It is easy to calibrate them through shear tests on saturated and the fully dried soils. It is verified that not only the sandy clay till and clayed silt but also the expansive soil's shear strength in wide ranges of suction under various can be well predicted.