Shear Strength Parameters Research Articles

Back analysis of the shear strength parameters of 3D landslides with Bayesian approach and reliability theory

To establish an accurate model for determining the shear strength parameters of sliding surfaces while considering the variability and uncertainty of geotechnical parameters, a reliability back analysis method for parameters based on Bayesian theory and a three-dimensional slope stability analysis method are proposed in this paper. First, the prior information of shear strength parameters is updated according to the field test information based on Bayesian theory. Then, combined with the reliability theory, the influences of different two-dimensional and three-dimensional sliding surface shapes on the parameters back analysis are studied. The results show that the uncertainty of parameters decreases with the increase in the amount of test data after introducing the test data to update the mastered parameter information based on Bayesian theory, and it is of great significance to consider the shape and three-dimensional effect of the sliding surface accurately to improve the accuracy of parameter determination and slope stability analysis.

Compaction and shear characteristics of recycled construction & demolition aggregates in subgrade: Exploring particle breakage and shape effects

Recycling construction and demolition (C&D) wastes into useable aggregates in subgrade applications offers significant sustainability benefits. However, the characteristics of recycled aggregates, including particle morphology, crushing strength, and shear behavior, differ substantially from natural aggregates. This paper presented an extensive experimental study on the compaction and mechanics performances of recycled concrete and brick aggregates, with a particular focus on the effects of particle breakage and shape characteristics. The compaction of recycled aggregate specimens comprising three structural types was evaluated using heavy Marshall compaction (HMC) and Superpave gyratory compaction (SGC). The compaction characteristics and particle breakage were examined, enabling a profound understanding of the compaction mechanisms associated with both methods. Furthermore, triaxial shear tests were performed to scrutinize the influences of particle shape, compaction degree, and confining pressure on shear characteristics. Results showed that after 80 gyratory rotations in SGC, the compaction degree of recycled aggregates aligned with the targeted results obtained from HMC. Changes in fractal dimension after compaction exhibited direct correlations with the two-dimensional shape distribution. Axial coefficient, fractal dimension and confining pressure most strongly influenced shear strength. In light of these insights, prediction models for shear strength parameters were proposed using multiple regression analysis. Overall, the study provides valuable insights into the relationships between aggregate morphology, compaction response, breakage behavior, and shear performance. These findings can facilitate optimized design and construction using recycled aggregates to advance sustainable infrastructure development.

Physical model test study on strength characteristics of gravel pile composite foundation

In gravel pile composite foundation stability design, the shear strength of composite foundation is critically important. However, due to the size limitation of test equipment, it is difficult to obtain its shear strength in field. This study designs a laboratory shear model test to obtain the shear strength of gravel pile composite foundation, where a total of four group tests were carried out, including two nature soils and two gravel pile area replacement ratios. The shear strength parameters obtained by the shear model tests are compared with the results of empirical formula methods such as the Chinese Standard Method and Priebe Method to verify the accuracy of these two methods. It is demonstrated that for the Chinese Standard Method, the empirical formula's results are smaller than the shear model test results when the pile-soil stress ratio b is 1. When the pile-soil stress ratio b is 1.5, the results are close to each other. For the Priebe Method, the empirical formula results are all larger than the shear model test results, and it is especially unsuitable for the mud soil.

INFLUENCE OF CRUSHED BRICK COLUMNS ON GEOTECHNICAL PROPERTIES OF EXPANSIVE SOIL

Utilization of crushed brick which is a common industrial material that is potentially wasted during the construction process in ground improvement can relieve its detrimental effects on the environment thereby reducing the waste disposal challenges. Hence, this study proposes its utilization as reinforcement to the soft clay soil. The tests mainly focused on the particle size distribution (PSD), specific gravity, Atterberg limit, proctor analysis as well as the shear strength parameters from Unconfined Compression Test (UCT). Coherently, the vibro-replacement method was deployed within a small-scale laboratory approach as a prediction model for the construction of a group of crushed brick columns. The column design was mainly classified into partially penetrated columns which have 60 mm and 80 mm height, and fully penetrated columns with 100 mm height. The mass of crushed brick used was approximately 1.07% - 4.56% of its total mass of specimen which produces the shear strength improvement rate from 11.00% - 18.55%. From the obtained results, the use of fully penetrated 100 mm diameter columns enhanced the undrained shear strength of kaolin clay to the maximum value, 26.20kPa or 18.55% as compared to the control sample with no reinforcement, which reduced the soil settlement and promoted the use of sustainable material in ground improvement.

Impact of initial conditions on the effectiveness of rolling dynamic compaction of granular soils

A finite element model (FEM) of rolling dynamic compaction (RDC) technology of a BH 1300 4 sided 8 tonne impact roller, developed previously by the authors, has shown to have reasonable agreement with that observed in the field. The use of this FEM is likely to provide high fidelity insights into the capability of the BH 1300 4 sided 8 tonne impact roller, namely in predicting the settlement and densification of an underlying granular material. A parametric study utilising this FEM with respect to initial density and shear strength parameters is undertaken to explore the relationship these properties have to the settlement and densification of a soil subject to RDC with a BH 1300 4 sided 8 tonne impact roller. The empirical relationships constructed within this study are validated against field trials from the literature of the roller improving sandy gravel fill at typical operating speeds of 10 km/h.

Stability Analysis of Waste Landfills on Potentially Unstable Territory

Abstract The article presents the stability analysis of two adjacent waste landfills located in a potentially unstable territory. One of the waste landfills is reclaimed and consists of ash. Municipal solid waste is actively deposited in the second landfill. In the space between the landfills, the expansion of the municipal solid waste landfill is planned, with a partial overlap of the reclaimed ash landfill. The instability of the area where the landfills are located is due to its susceptibility to the formation of landslides. The article presents the results of experimental verifications of the peak shear strength parameters of the ashes and the peak and residual shear strength of the soils forming the subsoil of both landfills and serve as input for stability analyses. The shear strength parameters of municipal waste are defined on the basis of literature research. The potential instability of both waste landfill territories was taken into account using the parameters of the residual shear strength of the subsoil. The stability analysis of waste landfills is expressed using both the peak and residual shear strength parameters of the subsoil of waste landfills. In addition, the effect of seismic loading on both landfills is considered in the stability analysis.

Constitutive Characteristics of Rock Damage under Freeze–Thaw Cycles

Freeze–thaw effect is one of the most important environmental conditions that rocks may be subjected to. Through laboratory model tests, the damage characteristics of rocks under the FTC were studied. Based on assuming that the strength of rocks subject to the FTC follows the Weibull distribution, the cumulative damage variable of the number of FTCs was introduced. A cumulative damage constitutive model of shear strength attenuation of rock that meets the Mohr–Coulomb criterion is established. The rationality and applicability of the proposed damage constitutive model are verified by comparing the results of rock shear strength parameters under cyclic freeze–thaw loads.

Stability Evaluation of Slope Based on Global Sensitivity Analysis

The uncertainty of parameters will have a significant impact on slope stability, where sensitivity analysis is a commonly used method in uncertainty research. However, traditional sensitivity analysis method costs much computation time. When calculating the sensitivity index of one parameter, all other parameters are taken as fixed values, and the uncertainty of all parameters cannot be considered simultaneously. Therefore, the variance-based and the moment-independent global sensitivity analysis (GSA) methods are both introduced to determine the influence of geotechnical parameters on slope stability in this study. To solve the importance index of GSA, the least angle regression algorithm, the kernel density estimation, and orthogonal polynomial estimation methods are developed to obtain variance-based importance index and the moment-independent importance index, respectively. The proposed methods allow all variables to change simultaneously within their variation range and have high computational efficiency. The results are in good at with those obtained by the variance-based Monte Carlo simulation method, which is considered as the exact solution forobtaining the importance index. The influence of the correlation between the shear strength parameters (c and φ) on the importance index is also studied, which indicates that the negative correlation will have a great impact on the importance index, which in turn affects the safety assessment of slope. Three engineering cases have been studied for engineering application, and the compared results indicate that the impact of the geotechnical parameters uncertainty on the safety factor (Fs) and failure probability (pf) are different. Therefore, the approaches based on GSA which can integrate the Fs with pf will be a promising approach for slope stability evaluation.

Enhancing geomechanical characteristics of calcium sulfoaluminate (CSA) cement-treated soil under low confining pressures

This study examines the efficacy of employing calcium sulfoaluminate (CSA) cement, an environmentally friendly binder, for enhancing the geomechanical characteristics of sand, particularly under low confining pressure conditions. A series of triaxial consolidated drained tests were performed on sand samples treated with varying content (5, 7, and 10%) of CSA cement and 10% ordinary Portland cement (OPC) under various low confining pressures (50, 100, 200, and 400 kPa). The test findings demonstrated the importance of cement content and confining pressure on the mode of failure, stress–strain and volumetric behavior, failure characteristics, and shear strength parameters of the treated quartz sand. After a curing period of 14 days, samples treated with 10% CSA cement exhibited a remarkable 212% increase in peak deviator stress and an 89% reduction in axial strain at failure, indicating higher initial stiffness compared to untreated samples under a 400 kPa confining pressure. Furthermore, the samples treated with 10% CSA exhibited higher peak deviator stress, initial stiffness, and strength development compared to those treated with 10% OPC. The scanning electron microscopy analysis provides insights into particle breakage and bond degradation processes, which increase with confining pressure in CSA-treated samples. Also, the mode of failure analysis reveals a transition from ductile to slightly brittle behavior with increasing cement content. Notably, the geomechanical properties of the treated material emphasized the significant impact of CSA cement on soil improvement. Thus offering a sustainable alternative for soil improvement in construction projects.

Effects of metakaolin and zeolite on the dispersion properties and shear strength of dispersive clay soil

ABSTRACT The current study used metakaolin and zeolite either separately or in combination at 0%, 2%, 4%, 6% and 8% of the soil weight to improve dispersive clay soil at optimal humidity levels. The samples were tested to determine the extent of change in the dispersion potential, as well as improvements in the shear strength of dispersive clay soil. The dispersive soil was obtained near the city of Ardakan in Iran and the extent of change in its soil dispersion potential was evaluated after 7 days of curing. The results of the pinhole test indicated that the addition of 2% zeolite plus 8% metakaolin to the soil considerably decreased the dispersion potential. Uniaxial testing after 7, 14 and 28 days of curing revealed that the UCS of the samples increased. The greatest increase was observed in samples containing 2% zeolite and 8% metakaolin after 28 days of curing. The direct shear test was carried out after 7, 14 and 28 days of curing on the unmodified soil and soil modified with optimal percentages of metakaolin and zeolite. The combined addition of zeolite and metakaolin was found to increase the shear strength parameters of the samples.

A comparative slope stability analyses of heavily jointed open-pit slopes using 3D limit equilibrium and finite element methods: a case study from Bingöl, Türkiye

ABSTRACT This study investigates the slope stability of Bingöl open-pit iron mine slopes using 3D limit equilibrium and finite element methods. The pit benches are 3 m wide and 6 m high, with an overall slope angle of 38°. The geological composition comprises slightly to moderately weathered and heavily jointed phyllite, micaschist, and gneiss. Shear strength parameters were determined through back analyses of already failed sections using the Hoek-Brown failure criterion and Geological Strength Index (GSI). Factor of safety values for static and dynamic conditions were calculated using 3D limit equilibrium and 2D finite element analyses. Results show good agreement between the two methods, with benches in the northern section exhibiting a significant decrease in safety factor under dynamic conditions, indicating near-limit equilibrium slopes.

The Use of Plastic Bottle Fibers in the Geotechnical Improvement of Tropical Soils from the Municipality of Viçosa - Brazil

Motivated by the environmental issues generated by the accumulation of waste from discarded plastic bottles and recognizing the utility of plastic properties in engineering, this research aimed to evaluate the application of plastic bottle fibers in the geotechnical improvement of tropical soils. In this context, the influence of quantity, roughness, and width of plastic bottle fibers on the shear strength parameters of soil- fiber mixtures, of two tropical residual soils, was analyzed. The fibers used in this study are made of Polyethylene Terephthalate (PET), generated from soft drink bottles, and added to the soil in different widths, textures, and contents. Results of the direct shear test showed higher shear strength for all soil-fiber systems compared to fiber-free mixtures. Additionally, the findings indicated that the systems with rough fibers presented better performances for clayey soil, whereas those with smooth fibers obtained better behavior for sandy soil. The cohesion results highlighted the better performance of mixtures with 0.5% fibers when compared to mixtures with 1% fibers. The enhancement of mechanical properties obtained in the studied soil-fiber systems demonstrates the potential application of these composites in geotechnical works.

INVESTIGATING SHEAR STRENGTH CHARACTERISTICS OF COHESIVE SOILS: STATISTICAL ANALYSIS IN KPK, PAKISTAN

It is crucial to determine the shear strength parameters (Cohesion (C) and Angle of internal friction (Φ) ) in order to encounter soil stability issues such as slope stability, bearing capacity and lateral earth pressure on retaining structures. The shear strength of cohesive soils is an essential parameter in Geotechnical Engineering design and construction. In Khyber Pakhtunkhwa (KPK), Pakistan, the soil is predominantly cohesive. it is essential to evaluate these parameters accurately to ensure safety and stability in civil engineering structures. In this research an effort has been made to evaluate statistically shear strength parameters of cohesive soils in KPK Pakistan. Engineers and construction experts can use the study's findings to influence judgments about the design and building of structures in the area. It highlights the importance of conducting proper soil testing and analysis before designing and constructing any engineering structure in the region. The study was conducted by collecting soil samples from different locations in KPK including Peshawar, Charsadda, Bannu, Swabi, Nowshera, Swat, Abbottabad, Haripur, Lakki Marwat, Tribal Areas, DI Khan, Mardan, and Kohat. The results of the statistical analysis indicate that the Cohesion(C) and Angle of Internal Friction (Φ) in KPK vary significantly across different locations, they are also presented in map of KPK showing values of Cohesion and Angle of Internal Friction using QGIS software. The average values of Cohesion (C) range from 12-47 kPa while mean values of Angle of Internal Friction (Φ) range from 16.2 – 41.1 degrees. The Standard Deviation & Coefficient of Variation was relatively high, indicating significant variation within each location.

Laboratory assessment of shear strength parameters of sand amended via subsequent biopolymer-based soil treatment and enzyme-induced calcite precipitation combinations

Current ground improvement practices predominantly rely on cement; however, interest in strengthening the ground in an environmentally sustainable manner is growing due to concerns regarding the environmental impact, such as the high CO2 footprint associated with cement usage. Biopolymer-based soil treatment (BPST) and enzyme-induced calcite precipitation (EICP) have emerged as promising methods for environmentally friendly ground improvement. While several studies have demonstrated the effectiveness of BPST and EICP individually, both methods have their limitations, which can be seen as complementary (for instance, EICP is more effective for coarse soils, whereas BPST is more effective for clayey soils). Recently, efforts have been made to combine BPST with EICP to address these limitations. This study considered four consecutive BPST-EICP combinations: 1) EICP alone, 2) BPST alone, 3) pre-EICP followed by post-BPST, and 4) pre-BPST followed by post-EICP. Laboratory experiments were conducted to assess the shear strength parameters (i.e., direct shear cohesion and friction angle) of sand treated using these four methods. The peak and residual shear strength parameters of the pre-EICP followed by post-BPST soil were the highest among all cases. However, each combination is suited to specific site conditions, such as soil type, groundwater conditions, and the purpose of ground improvement.

Influence of biochar in the calcite precipitation of sandy soil using sporosarcina ureae

The microbially induced calcium carbonate precipitation (MICP) technology is an emerging novel and sustainable technique for soil stabilization and remediation. MICP, a microorganism-mediated biomineralization process, has attracted interest for its potential to enhance soil characteristics. The inclusion of biochar, a carbon-rich substance formed by biomass pyrolysis, adds another degree of intricacy to this process. The study highlights the impact of the combination of biochar and MICP together, using a bacterium, Sporosarcina ureae, on soil improvement. This blend of MICP and biochar improved the soil in terms of its geotechnical properties and also enabled the sequestering of carbon safely. It was observed that addition of 4% biochar significantly increased the soil's shear strength parameters (c and φ) as well as its stiffness after 21 treatment cycles. This improvement was because the calcium carbonate precipitate, which acts as a crucial binding agent, increased significantly due to microbial action in the soil-biochar mixture compared to the pure soil sample. The excess carbonate precipitation on account of biochar addition was verified through SEM-EDAX analysis where the images showed noteworthy carbonate precipitation on the surface of particles and increment in the calcium mass at the same treatment cycles when compared with untreated sand. The collaboration between MICP and biochar effectively increased the carbon sequestration within the sand sample. It was observed that at 21 cycles of treatment, the carbon storage within the sand sample increased by almost 3 times at 4% biochar compared to sand without any biochar. The statistical analysis further affirmed that strength depends on both biochar and the number of treatment cycles, whereas carbon sequestration potential is primarily influenced by the biochar content alone. This strategy, as a sustainable and environmentally friendly approach, has the potential to reform soil improvement practices and contribute to both soil strength enhancement and climate change mitigation, supporting the maintenance of ecological balance.

Comparing shallow landslide susceptibility maps in Northeastern Türkiye (Beşikdüzü, Trabzon): a multivariate statistical, machine learning, and physical data-based analysis

This study endeavors to assess and compare the efficacy of various modeling approaches, including statistical, machine learning, and physical-based models, in the creation of shallow landslide susceptibility maps within the Besikduzu district of Trabzon province, situated in the Black Sea Region of Türkiye. The landslide inventory data, spanning from 2000 to 2018, was acquired through meticulous field surveys and analysis of Google Earth satellite imagery. Key topographic and geologic input parameters, such as slope, aspect, topographic wetness index, stream power index, plan and profile curvature, and geologic units, were extracted from a high-resolution 10 m spatial DEM (Digital Elevation Model) and a 1:25,000 scaled digital geology map, respectively. Additionally, soil unit weight and shear strength parameters, critical for the physical-based model, were determined through field samples. To evaluate landslide susceptibility, logistic regression, random forest, and Shalstab were employed as the chosen methods. The accuracy of susceptibility maps generated by each method was assessed using the area under the curve method, yielding impressive values of 0.99 for the random forest model, 0.97 for the logistic regression model, and 0.93 for the Shalstab model. These results underscore the robust performance of all three methods, suggesting their applicability for generating shallow landslide susceptibility maps not only in the Black Sea Region but also in analogous areas with similar geological characteristics.

Assessing changes in geotechnical properties of soil caused by oil contaminants

Soil pollution seriously threatens the integrity of geotechnical soil properties, considerably altering physical and mechanical characteristics. Therefore, the geotechnical characteristics of contaminated soils should be studied. Samples used in this study were obtained from Peshawar, Khyber Pakhtunkhwa Province, Pakistan. Tests such as Atterberg limits, direct shear strength, sieving analysis, consolidation, and unconfined compression were conducted. The internal friction angle, cohesiveness, and shear strength of the soil decreased when oil pollution was introduced, probably owing to the lubricating effect of oil, which also causes a decrease in the dielectric constant. Surprisingly, in certain cases, bioremediation could reduce soil swelling, relieve pressure from swelling, and prevent soil settlement. Oil contamination resulted in decreased permeability and mechanical strength in the analyzed soil samples. Importantly, the effect of oil contamination on the shear strength parameters is not uniform and depends on the soil type. A thorough study is required because of the long-term consequences of oil contamination, particularly the long-term aging effects on geotechnical soil properties and behavior. Therefore, these results must be compared with those of the most recent tests. Furthermore, future research should consider the complex interplay between the functional groups inherent in soil solids and the injected contaminated oil.

Experimental Study of Cationic-Modified Biopolymer for Increasing the Shear Strength of Sand

The application of biopolymers as a more environmentally friendly alternative to cement has emerged as an interesting research subject.The purpose is to enhance the shear strength of sandy soils. In this article, the selected biopolymer is cationic-modified starch. It is expected that cationic starch will have less water absorption properties since modified starch has cationic groups in place of the OH- groups found in the normal starch. This cationic-modified starch namely Amylofax. Five types of samples are created for this testing, including Sample A is prepared with the composition of (silica sand + 2% Amylofax T1100 (w/w) + 20% water (w/w))., Sample B consists of (silica sand + 2% Amylofax T2200 (w/w) + 20% water (w/w))., Sample C is comprised of (silica sand + 2% Amylofax T1100 (w/w) + 2% Glucomannan (w/w) + 20% water (w/w)), Sample D consists of (silica sand + 2% Amylofax T2200 (w/w) + 2% Glucomannan (w/w) + 20% water (w/w)), and Sample E includes (Ottawa sand + 2% cement (w/w) + 20% water (w/w)). The samples were tested using a direct shear test apparatus to determine the soil shear strength parameters (c) cohesion and (Ø) internal friction angle. After conducting the tests on the sand samples with the addition of modified starch biopolymer (cationic starch), it was found that the cohesion value was 961kPa, and the internal friction angle was 63°. These results indicate higher shear strength values compared to sand mixed with natural starch.

Research Enhancing Acidic Mine Wastewater Purification: Innovations in Red Mud-Loess.

This study investigates the adsorption of cadmium (Cd) by red mud-loess mixed materials and assesses the influence of quartz sand content on permeability. Shear tests are conducted using various pore solutions to analyze shear strength parameters. The research validates solidification methods for cadmium-contaminated soils and utilizes SEM-EDS, FTIR, and XRD analysis to elucidate remediation mechanisms. The findings suggest that the quartz sand content crucially affects the permeability of fine-grained red mud-loess mixtures. The optimal proportion of quartz sand is over 80%, significantly enhancing permeability, reaching a coefficient of 6.7 × 10-4 cm/s. Insufficient quartz sand content of less than 80% fails to meet the barrier permeability standards, leading to a reduced service life of the engineered barrier. Adsorption tests were conducted using various pore solutions, including distilled water, acidic solutions, and solutions containing Cd, to evaluate the adsorption capacity and shear characteristics of the red mud-loess mixture. Additionally, the study examines the behavior of Cd-loaded red mud-loess mixtures in various pore solutions, revealing strain-hardening trends and alterations in cohesiveness and internal friction angle with increasing Cd concentrations. The analysis of cement-red mud-loess-solidified soil demonstrates enhancements in soil structure and strength over time, attributed to the formation of crystalline structures and mineral formations induced by the curing agent. These findings provide valuable insights into the remediation of cadmium-contaminated soils.

Effects of Bio-enzyme on the strength properties of soil

Engineers regularly attribute the complexity of constructing parts on or by soils, those do not have sufficient strength to sustain the loads required leading them either all over construction or in the study life of the structure. The more areas of India shows of CH (Inorganic Clay of High Plasticity) clay soil characterized by more small portion, lower shear strength and lesser bearing capability. The unfortunate engineering performances of these soils has enforced Engineers to instrument charge competent and eco-friendly processes for increasing the engineering properties of these soils. As the conservative soil stabilizers like gravel, sand, etc. Are declining and suitable expensive day by day at an extremely quick rate, it becomes necessary to emerge for possible ecological stabilizers as their substitute. In current scenario the various Bio-enzymes have emerged as lesser cost stabilizers for soil stabilization. Bio-enzyme is a common, harmless, non-flammable, noncorrosive liquid enzyme formulation fermented from vegetable forms that creates the engineering behavior of soil, generates more soil compaction densities and more stability. One such Bio-enzyme, Terrazyme, has been applied in the current occupation to study its consequence on Atterberg Limits, Unconfined Compressive strength, and shear strength parameters of a CH soil. It has been confirmed that Terrazyme purifications of CH soil outcome in main development in Unconfined Compressive strength and Shear Strength parameters separately from Index characteristics. The entire characteristics are reliant on remedial time also. There is a specific best concentration for each characteristic in concern and it ranges from 0.2 ​ml/kg and 0.4 ​ml/kg of soil. Although, the more plastic clay soil is get to be addition responsive to Terrazyme purifications.