Shear Strength Of Soil Research Articles

Validation, Reliability, and Performance of Shear Strength Models for Unsaturated Soils

Soil shear strength is the most fundamental property when designing structures in the ground and should be carefully assessed and understood. Several empirical models were introduced to predict the shear strength of unsaturated soils. However, there is uncertainty regarding the applicability and sensitivity of these prediction models. This paper presents a comprehensive verification study to assess the reliability and validity of the existing theoretical models. The results obtained from the prediction models are compared to measured data using thirty experimental data sets. A performance classification program is also conducted to assess the suitability of the analytical models for different soil types as well as over a wide range of matric suctions, saturation degrees, soil densities, soil plasticity, and clay activity. The impact of each single parameter is clarified by the microstructure studies, which also provides insight into the mechanics of unsaturated soils. The results indicated that the applicability of models is more appropriate for sandy soils rather than for clayey ones. The performance of shear strength models tends to decrease with an increase in matric suction, initial density, plasticity index, and clay activity. It is, therefore, recommended that the shear strength estimation models should be carefully selected depending on the soil type and properties. Besides, the analysed results pointed out that the choice to assume the factor chi in the equation of Bishop equals the saturation degree is only suitable for medium-dense soils with low matric suction. This assumption is particularly not effective for clayey soils, or dense soils with high matric suction.

Quantifying root-induced soil strength, measured as soil penetration resistance, from different crop plants and soil types

A common soil mechanical property for assessing soil strength is soil penetration resistance (PR) or soil cone index (CI), which is related to the undrained shear strength of saturated and cohesive soil. Plant roots can increase soil strength, but physical conditions may confound this. Pot experiments were conducted using 70 cm soil columns, three soil types (beach sand, erosion-prone soil, and two typical arable soils), and four crop plants (maize, sorghum, Napier, and vetiver grass). We tested the hypothesis that plant roots impact soil strength, measured as soil PR, and the induced soil strength differs based on plant species. The CI and root system architecture (RSA) traits were measured. Napier grass grown in arable soils recorded higher total biomass. Together with maize, Napier grass had a more significant root length density, particularly at 25–40 cm depth. The CI increased with increasing depth, with a 57–99% increase in CI in the bottom layer compared to the top layer of the soil column. The overall CI of soils grown to Napier grass (2.0 and 2.3 MPa) and maize (1.7 and 2.2 MPa) were similar, but both were higher than the soils cultivated with the other crop plants and unplanted control. The overall CI of the SEA sand of ∼2.0 MPa was 36%, higher than that for the arable soils. Soil moisture content did not significantly increase CI, but the interaction of soil bulk density and root system traits could be implicated in increased CI of root-permeated soils. It is concluded that (i) roots growing in arable soils can increase CI and hence soil strength, possibly due to the binding effect of root systems, even when the transpiration effect of plants on soil moisture is low; (ii) crop plants contribute differently to soil strength, and (iii) Napier grass could offer a rapid growth and establishment option when considering plants for soil reinforcement and stability.

Effects of Physical and Mechanical Properties of Soft Soil on Subgrades Performances in Lubuk Bayas Village, Serdang Bedagai Regency

Generally, the existence of soft soil in Indonesia will be a problem in the construction of highway construction. One factor that influences and needs to be known in road construction is the characteristics of the subgrade where the pavement construction will be placed on it. Poor soil characteristics can cause bumpy road surfaces, cracks, or other road damage. Therefore, before carrying out a soil improvement, it is necessary to know its characteristics through the physical and mechanical properties of the subgrade. This research was conducted in Lubuk Bayas Village, Serdang Bedagai Regency, North Sumatra Province. Tests of physical properties in this study include sieve analysis, water content, specific gravity, plasticity limit test, and liquid limit test. The soil shear strength test and California Bearing Ratio (CBR) test were carried out to test the mechanical properties using a Dynamic Cone Penetrometer (DCP). From the results of testing the physical properties of the soil, it was found that Samples 1, 2, and 3 were fine-grained soils with the percentage of soil passing the No.200 sieve greater than 50%. The USCS classification system shows that samples 1 and 2 of the soil are in the Lean Clay (CL) group, while sample 3 is in the Fat Clay (CH) group. Samples 1, 2, and 3 include soils with high plasticity because the PI value is >17. The results of testing the mechanical properties of the soil Sample 1 obtained the value of c = 0.1299 kg/cm2 and Ø = 13.2°, in Sample 2 obtained the value of c = 0.1075 kg/cm2 and the value of Ø = 11.2° and in Sample 3 obtained the value of c = 0.1275 kg/cm2 and the value of Ø = 11.9°. DCP testing on samples 1, 2 and 3 obtained CBR values of 5.35%, 4.73% and 3.15%. From the CBR results, it can be seen that the soil in this location has a low soil bearing capacity, so if it is to be used as a subgrade layer, it will be necessary to repair the soil first so that structural damage does not occur in the future. Soil improvement can be made by stabilizing the soil using natural materials to maintain environmental sustainability. Natural materials that can be used include sand with certain gradations, stone ash, palm shell ash, and various other natural materials.

Effect of Degree of Saturation on soil-nail Pullout Resistance

Soil nailing is a technique which is used to reinforce and strengthen the existing ground conditions. This is done by installing closely spaced, passive, structural inclusions known as nail into the soil and these nails helps to improve the overall shear strength of soil. The nail pullout resistance is the shear stress at the grout-soil interface. The soil-nail pullout resistance depends on many parameters. Among the factors influencing the soil-nail pullout resistance, degree of saturation of the soil is an important factor. As degree of saturation of soil mass change with the moisture content of the soil, the pullout resistance may decrease during the intense rainfall. However, verification of pullout tests on soil-nail are not conducted under the worst condition. Hence, measured pullout resistance may not be a safe parameter for design. As such, in this research study, the effect of degree of saturation on pullout resistance was studied by conducting a series of laboratory tests using a laboratory pullout box. Especially designed waterproof cap was used to apply back pressure to saturate the soil within the pullout box. Variation of earth pressures close to the grouted nail were observed during the tests. It was evident from the results that higher the degree of saturation, lower the pullout resistance. Maximum pullout resistance was observed when the degree of saturation is near the optimum moisture of the soil. When the soil is sufficiently dry, lower pullout resistance was observed due to low bond strength between grout surface and surrounding dry soil.

A Systematic Study to Strengthen the Sub Grade of the Pavement by Stabilization of Expansive Soil with Molasses and Jute Fibre

Abstract: Expansive soils, commonly referred to as Black cotton soils (BC), possess undesirable engineering properties such as low bearing capacity and high compressibility. To address these challenges, various stabilizers have been used to enhance the strength of expansive soil, including jute fiber and molasses. This thesis focuses on investigating the effects of incorporating jute fiber as a stabilizer and molasses as an additive to improve the properties of expansive soil. The objectives of this study are to enhance the shear strength of expansive soil by blending jute fiber and molasses mixtures. Jute fibers of different lengths (1cm, 2cm, 3cm, and 4cm) and various percentages (0.5%, 1%, 1.5%, and 2%) are used as stabilizers. Molasses is employed as an additional stabilizer with varying percentages (5%, 8%, 12%, and 15%). Laboratory investigations reveal that the addition of 12% molasses and 1.5% jute fiber significantly reduces the liquid limit, plastic limit, and plasticity index of the expansive soil, while simultaneously increasing the maximum dry density and California Bearing Ratio (CBR). Furthermore, cyclic load test results demonstrate a 62% improvement in the load carrying capacity of the treated expansive soil subgrade flexible pavement compared to untreated expansive soil flexible pavement. Utilizing construction wastes like molasses offers an alternative to reduce road construction costs, especially in rural areas of developing countries. Additionally, jute fiber provides effective reinforcement for expansive soils. These findings highlight the potential of jute fiber and molasses as sustainable and cost-effective stabilizers for enhancing the performance of expansive soils in construction projects

Meningkatkan Stabilitas Lereng Berdasarkan Pengujian Karakteristik Tanah

Kediri Regency has diverse potential and wealth, including natural resources, culture, and tourism. One example is the Dolo waterfall located in Jugo Village. In January 2023 there was an avalanche caused by heavy rainfall in the mountainous area of Jugo Village, Mojo District, Kediri. The landslide disrupted road access to tourist attractions, infrastructure and also affected the economy. Several studies have revealed that soil type, shear strength, and soil consistency properties are important in influencing a slope’s stability level. However, the discussion of landslide prevention efforts regarding soil and slope characteristics is still limited. This study aims to determine soil type, consistency properties, shear angle, soil cohesion, and slope safety factors in Jugo Village, Mojo District, Kediri Regency. Research begins with a survey and sampling, then testing is carried out in the laboratory and calculated the slope safety factor (Fs). The results revealed that the characteristics of the soil in Jugo Village influenced the landslides that occurred. Both the type of soil, the consistency limit, and the shear strength of the soil indicate that the slope is unstable, this is also indicated by the calculation value of Fs <1. The results of this study can be used as a reference in planning and carrying out slope stability at that location so as to prevent landslides in the future. The effort that can be done is to change the slope to 35° so that the slope becomes stable.

Experimental Analysis and Remediation Rate of Copper and Nickel Contaminated Industrial Site Soil Using Biochar

Abstract: The most crucial element for construction purposes is healthy and good soil. Through the incorrect disposal of carcinogenic compounds, which seeps into the earth and degrades soil quality, heavy metals and metalloids can contaminate soil. The goal of this project is to turn biomass into biochar and re-apply it to the soil in order to disrupt the source-receptor pathway, which will lead to heavy metal-free soil and an improvement in soil characteristics. Biochar is a material made of waste biomass that is highly porous, carbon-rich, and fine-grained. Pyrolysis is a process in which biomass is subjected to thermochemical conversion without oxygen. Rice husk biomass was pyrolyzed in a muffle furnace at temperatures between 500 and 700 °C to create the biochar that was employed in this experiment. Through physical adsorption or an ion exchange mechanism, biochar has the ability to remove heavy metal ions like copper and nickel. The soil used in this study was gathered from the Kurumbapalayam, Coimbatore, electroplating factory. AAS was used to evaluate soil samples in order to measure the amount of heavy metals present. A method that is useful for calculating the amounts of trace elements contained in the soil sample is the use of an atomic absorption spectrometer (AAS). In order to determine the presence of metal oxide X-Ray Diffraction was done and to know the connection between the biochar and the soil, scanning electron microscopy (SEM) was done. Using a direct shear test, the shear strength of soil treated with various amounts of biochar was evaluated. Additionally evaluated were the soil's compaction characteristics and pH fluctuation in response to the addition of various biochar percentages. The outcome shown that adding biochar to the soil neutralises heavy metals and enhances the characteristics of the soil.

Interface Shear Strength Behavior of Cement-Treated Soil under Consolidated Drained Conditions

This paper presents a series of laboratory tests to determine the shear strength and interface shear strength of cement-treated silty soil under consolidated and drained conditions. The test variables include the effective normal stress, cement content, and curing period. Experimental results indicated that the effective shear strength and interface shear strength of cement-treated soil specimens increased significantly as the cement content increased. After 28 days, the average shear strength ratio increased from 1.28 to 2.4, and the average interface efficiency factor improved from 1.15 to 1.55 as the cement content increased from 3% to 10%. It resulted from an increase in grain size and the fraction of sand-sized particles in the treated soils, approximately in two-time increments for the specimens treated with 10% cement content after 28 days of curing. In addition, the peak and residual values of the shear strength and interface shear strength of the cement-treated soil specimens were determined to assess their brittle behavior under high shear deformation. Last, two new empirical models are introduced herein. The first power equation is to predict the shear strength ratio of cement-treated soil at 28 days of curing using the soil-water/cement content ratio. The other proposed model is useful for assessing the rate of shear strength and interface shear development of cement-treated soil specimens within 56 days of curing.

Evaluating the Undrained Shear Strength of Kalimati Soil Using Field Vane and Unconfined Compression Test; a Study on Applicability of Bjerrum’s Correction Factor

Rapid urbanization and geological challenges in Kathmandu have made it crucial to understand the geotechnical properties of the soil in the region. This study here focuses on the undrained shear strength of silty clay in Kalimati, Kathmandu, and investigates the applicability of Vane Shear tests and its parameters over other shear strength tests from other methods. Geotechnical investigations were carried out at three locations within the Kathmandu Engineering College premises and in-situ and laboratory tests were conducted on undisturbed and disturbed samples. Then the study compared the field vane shear strength, undrained strength from unconfined compression tests, and laboratory vane shear strength of the samples. For the field vane shear test the correction factor as suggested by Bjerrum was used and the results indicate that this method overestimates the shear strength in Kalimati soil, indicating no adjustment is necessary. The findings of this study have important implications for the design and construction of structures in the region, and contribute to a better understanding of the geotechnical properties of Kathmandu soil.

Bearing capacity of shallow foundations accounting for seismic excess pore pressures

The method of characteristics has been used to develop a rigorous solution for the evaluation of seismic bearing capacity of shallow foundations resting on homogenous fully submerged soil accounting for the effect of earthquake-induced pore water pressures. The solution, derived with reference to both the Hill and Prandtl plastic mechanisms, is essentially referred to the bearing capacity factor Nγ, is of general validity and has been checked against finite element analysis results. An original empirical expression providing the corrective coefficient to be introduced in the usual trinomial bearing capacity formula has been proposed, accounting for the reduction in bearing capacity due to combined effect of soil inertia and earthquake-induced pore water pressures. It has also been demonstrated that, even considering earthquake-induced excess pore pressures, the soil and superstructure inertial effects are still decoupled. This allowed introducing an overall corrective coefficient accounting for both the inertial (soil and superstructure) and excess pore pressure effects, computed as the product of the corresponding corrective coefficients. Finally, original simple equations were derived giving a threshold value of the excess pore pressure ratio required to trigger a bearing capacity failure in the static post-seismic conditions because of the soil shear strength reduction.

Influence of stone content on face stability for tunnels in sandy cobble strata

As a result of the complex geological conditions of sand-cobble stratum, various types of problems may arise during construction of tunnels crossing sand-cobble stratum, the most prominent of which is the stability problem of the face. In order to study the stability of the tunnel face in sand-cobble stratum, first, a continuous medium model of sandstone soil is established, and numerical simulation is carried out on the three-axis compression test of sandstone soil to analyze its micro-mechanical characteristics. Second, a calculation model of simulated sandstone strata excavation is established by FLAC3D finite difference software. Then, the safety factor K calculated by the strength reduction method is introduced as the evaluation index of the face stability, and the face stability of sand-cobble tunnels with a series of stone content, tunnel burial depth and tunnel diameter are analyzed. The results show that the macro stress-strain curve of sand-cobble soil in the three-axis compression test can be divided into linear stage, elastic-plastic stage and ideal plastic stage, and the shear strength of sand-cobble soil increases with the increase of stone content. In the process of tunnel excavation, the stability of tunnel face increases with the increase of stone content in the stratum; while the tunnel buried depth and diameter increase, the stability of tunnel face decreases. These results provide a reference for predicting the instability and failure of sand-cobble tunnels, which is critical for the construction and safety of tunnels in sand-cobble stratum.

TOTAL AND MATRIC SUCTION MEASUREMENT OF UNSATURATED SOILS IN BAGHDAD REGION BY FILTER PAPER METHOD

Soil suction is one of the most important parameters describing the moisture condition of unsaturated soils. The measurement of soil suction is crucial for applying the theories of the engineering behavior of unsaturated soils.The filter paper method is one of the soil suction measurement techniques In this paper, five soil samples were collected from five sites within Baghdad city – al-Rasafa region. These soils have different properties and they were prepared at different degrees of saturation. For each sample, the total and matric suction were measured by the filter paper method at different degrees of saturation. Then correlations were made between the soil properties and the total and matric suction. It was concluded that the suction increases with decrease of the degree of saturation. The relationships between the total and matric suction and the filter paper water content are approximately linear and indicate decrease of suction with increase of the filter paper water content. The total and matric suction increase with the decrease of the soil shear strength.

Heavy Logging Machinery Impacts Soil Physical Properties More than Nematode Communities

Mechanized logging equipment causes considerable soil disturbance, but little information is available regarding thresholds for impacts on soil nematodes—critical members of soil foodwebs which perform important ecological functions. We examined responses of nematode communities and soil physical characteristics to the increasing number of passes (one, three, or nine) by a tracked feller buncher during thinning of a xeric mixed conifer forest in New Mexico, USA. Within and between the harvester tracks, we measured soil surface penetration resistance and shear strength, quantified bulk density at four depth increments up to a maximum depth of 27 cm, and characterized nematode assemblages in the upper 10 cm. Eight months after treatment, nematode communities were less impacted than soil physical properties by harvester passes. Total nematode abundance was unaffected by any level of feller buncher disturbance, and sensitive K-selected nematode groups were reduced only at nine passes. Conversely, soil compaction occurred with a single pass and extended deep into the soil profile to at least 23–27 cm. The first pass also decreased surface penetration resistance and shear strength, indicating disruption of soil surface structural integrity. Additional passes did not further increase bulk density or decrease surface structural integrity. Our results indicate that low levels of logging machinery traffic may have negligible effects on nematode communities, but nevertheless emphasize the importance of minimizing areas subjected to disturbance because of impacts on soil physical properties.

Optimized ANN-based approach for estimation of shear strength of soil

Optimized ANN-based approach for estimation of shear strength of soil

Sediment penetration performance of a portable underwater robot for core sampling

AbstractAs described in this paper, we investigate the sediment penetration performance of a portable underwater robot with a helical screw pipe using marine thrusters with limited force. First, we derive a mathematical model based on an empirical and simple method using the undrained shear strength of cohesive soil to provide a rough estimate of maximum penetration depths. Then, we perform numerical analysis for estimating the maximum depth of sediment penetration and for designing a sampling pipe. Additionally, we use experimentation to investigate the relation between the penetration depth of the helical screw pipe and the force of marine thrusters mounted on the portable underwater robot. After testing the penetration performance in a water tank, we conduct a field experiment at Lake Biwa and obtain results of the penetration depths. The maximum penetration into the lake sediment is at least 0.30 m. The results demonstrated the possibility of using the derived mathematical model to make a rough estimation of the maximum penetration depth for clay sediments. Additionally, we can use non‐powerful thrusters equipped with small autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) for sediment sampling. The proposed method is also applicable for the installation of underwater sensors using small AUVs and ROVs.

Feasibility of soil oxidation-reduction potential in judging shear behaviour of hydrocarbon-contaminated soil

This study investigates the indicative role of oxidation-reduction potential (ORP) and pH of hydrocarbon-contaminated soils on their shear characteristics, contributing to safer and more efficient ex-situ remediation and management processes. The presence of hydrocarbons alters the soil's shear strength by affecting the hydration shell thickness, fluid's dielectric properties, and ion/electron exchange, as well as the soil's electrochemical force, which in turn affects the ORP and pH. The relationship between hydrocarbon concentrations in contaminated soils (0.1–15%) and corresponding ORP/pH values could be fitted linearly with a good correlation coefficient r (0.978), highlighting the potential of ORP/pH as an indicator for pollutant occurrence. Furthermore, the relationships between ORP/pH and shear strength, as tested in our study and obtained after processing from relevant literature sources, exhibited a strong fit (r = 0.976–0.995). The Mohr-Coulomb criterion modified using the ORP/pH parameter was established, which could improve the fitting effect of these relationships (r = 0.988–0.996), verifying the reliability of the novel criterion and application feasibility of ORP/pH. In future research, this modified criterion can be employed to conveniently assess the shear strength of contaminated soil by considering the shear behaviour of virgin soil and the ORP/pH values of the contaminated soil.

Application of Mobile-Based Augmented Reality Technology Concepts in Interactive Learning Systems for Liquefaction Phenomena for the Deaf

One of the natural disasters currently happening in Indonesia is an earthquake. An earthquake is a condition where the earth shakes due to volcanic activity and collisions due to the movement of the earth's plates. Earthquake activity causes many problems. One of them is liquefaction. Liquefaction is an event that indicates a loss of soil shear strength due to an increase in pore water pressure. This occurs because the earthquake load occurs so quickly and briefly. Liquefaction is an illustration of the effect of an earthquake so that the soil layer loses its strength. The public rarely knows the phenomenon of earthquakes and liquefaction. Not many people know how the process of the movement of the earth is the forerunner of earthquakes, especially people with hearing impairments. They could only feel an earthquake. Therefore, there is a need for education that can be conveyed to the public. Educational techniques in the virtual form will be a special attraction for people, especially people who are deaf or hard of hearing. Augmented Reality (AR) technology is a technology where virtual objects and real objects are combined. The AR is used to create virtual and interactive learning media. This study produced an application as a learning media that utilizes AR technology with the Marker Based Tracking method. The technology was developed using the MDLC (Multimedia Development Life Cycle) method for the learning media to be more interactive. The results of the tests concluded that the application could be used as an interactive learning medium to increase knowledge about earthquakes and the effects of liquefaction on the community.

Numerical Modelling for effect of rainfall on unsaturated soil slopes

Expansive soils are predominant in many parts of the world. Expansive soil treated as problematic soils, as economic and design a safe slope on expansive soils is major challenge for civil engineers. Expansive soils were compacted under unsaturated condition, in various construction projects. Major failures reported in many countries around the world are due to swell shrinkage characteristics causing unstable slopes. Fills and compacted soils have an inherent suction when they are first compacted. The suction is the most important factor which affects the shear strength of unsaturated soil. variation of suction in unsaturated soil is an important factor considered for solving issues like slope stability and bearing capacity failure in unsaturated soil. Rainwater infiltration are major triggering factor for failureof expansive soil slopes. The strength of unsaturated soil changes with water evaporation and infiltration. Due to infiltration of rainwater into the soil a significant change in the pore water takes place. Hence, this fluctuation in pore water pressure responsible for the distinct mechanical behavior of unsaturated soil under different Geotechnical problems.A numerical modeling was done with Plaxis LE software, considering parameters of unsaturated soil. As the changes in pore-water pressure and moisture content are a function of the flow of moisture through the soil-atmosphere boundary.The effect of soil type, rainfall intensity, location of ground water table, permeability functionsareconsidered to reproduce the soil-atmosphere interaction. Obtain results illustrates the combine effect of suction and increase of saturation due to rainfall on slopes. It was observed that rainfall increase the induced matric suction and increase the positive pore water pressure finally results in slope failures.

Mechanical and Microscopic Properties of Cement Composite Expansive Soil with Graphene Oxide: Ecofriendly Modification Material

Cement composite soil is a more stabilized method in expansive soil foundation projects, but it is essential to find an ecofriendly modification material to reduce the content of cement and its pollution for the environment. A series of unconsolidated–undrained (UU) triaxial tests were conducted to investigate the modification effect of graphene oxide (GO) on cement-stabilized expansive soil (CS), and the contents of GO were 0.05%, 0.1%, 0.15%, and 0.2%, respectively. The test results show that (1) the deviatoric stress–strain curves of CS gradually change from a weakly softening type to a strongly softening one after adding GO. (2) The compressive strength, shear strength, and toughness of GO-modified cement-stabilized expansive soil are better than CS, and the optimal GO content is 0.05%. (3) Microscopic tests show that GO can promote the hydration reaction of cement and reduce the internal pores of CS. Consequently, the mechanical properties and microstructure of CS can be significantly improved after adding GO, and it is feasible to replace a part of the cement with GO in expansive soil foundation projects.

Rate-dependency of residual shear strength of soils: implications for landslide evolution

Shear-rate weakening or strengthening behaviours can effectively control landslide runouts, defining sudden runaway sliding or years-long slow-creep phases. These behaviours are partly controlled by the properties of the basal material. Understanding its stress–strain–time response is crucial in physically-based assessments of landslide dynamics and the associated risk. We investigate the frictional resistance of a calcium bentonite, a kaolin and a quartz sand by means of a conventional ring-shear apparatus under normal stresses representative of landslide shear zones. Results for the fine-grained soils, in line with literature on pure clays, indicate important velocity strengthening, whereas small shear-rate effects were observed in sand. As long as effective stresses remain constant, a velocity strengthening response can exert a feedback that, under certain conditions, counteracts perturbations in boundary conditions and prevents fast runouts on pre-existing shear zones. Accordingly, we argue that specifically testing for shear-rate-dependency and incorporating observed behaviours in model formulations can be beneficial for better predicting landslide fates.