Soil Tensile Strength Research Articles

Exploring an eco-friendly approach to improve soil tensile behavior and cracking resistance

Soil tensile strength is a critical parameter governing the initiation and propagation of tensile cracking. This study proposes an eco-friendly approach to improve the tensile behavior and crack resistance of clayey soils. To validate the feasibility and efficacy of the proposed approach, direct tensile tests were employed to determine the tensile strength of the compacted soil with different W-OH treatment concentrations and water contents. Desiccation tests were also performed to evaluate the effectiveness of W-OH treatment in enhancing soil tensile cracking resistance. During this period, the effects of W-OH treatment concentration and water content on tensile properties, soil suction and microstructure were investigated. The tensile tests reveal that W-OH treatment has a significant impact on the tensile strength and failure mode of the soil, which not only effectively enhances the tensile strength and failure displacement, but also changes the brittle failure behavior into a more ductile quasi-brittle failure behavior. The suction measurements and mercury intrusion porosimetry (MIP) tests show that W-OH treatment can slightly reduce soil suction by affecting skeleton structure and increasing macropores. Combined with the microstructural analysis, it becomes evident that the significant improvement in soil tensile behavior through W-OH treatment is mainly attributed to the W-OH gel's ability to provide additional binding force for bridging and encapsulating the soil particles. Moreover, desiccation tests demonstrate that W-OH treatment can significantly reduce or even inhibit the formation of soil tensile cracking. With the increase of W-OH treatment concentration, the surface crack ratio and total crack length are significantly reduced. This study enhances a fundamental understanding of eco-polymer impacts on soil mechanical properties and provides valuable insight into their potential application for improving soil crack resistance.

Experimental study on tensile strength of granite residual soil during drying and wetting

The tensile strength of remolded granite residual soil under different water content conditions, during wetting and drying, was investigated using a self-made horizontal direct tension apparatus. The variations in tensile strength and the microcosmic mechanism of shrinkage crack formation and development were elucidated from the perspectives of suction stress and cementing force. Experimental results indicated that the tensile strength of granite residual soil initially increased and then decreased under different water content conditions. During the wetting process, the tensile strength followed a similar trend, but the peak strength (10 kPa) was lower compared to that under different water content conditions (22 kPa). The drying process exhibited three stages of tensile strength variation: a linear increase stage, a stationary stage, and a slight decrease stage. The peak value of the tensile strength during drying was much higher (reaching approximately 84 kPa) than that under different water content conditions and the wetting process. The tensile strength of remolded granite residual soil was solely controlled by suction stress under different water content conditions and in the wetting process. However, in the drying process, the tensile strength was also influenced by the cementing force, resulting in a peak value four times higher than that under different water content conditions and seven times higher than that in the wetting process. Suction stress served as the source of tensile stress in the soil during the drying process, and the development of cracks caused by suction stress led to a reduction in the overall tensile strength of the soil. Suction stress acted as both a contributor and a destroyer of soil tensile strength. During the drying process, the soil sample exhibited weakly acidic pH and gradually weakened hydrophilic ability. This led to the formation of stronger binding forces within the soil skeleton. Consequently, for soil samples with the same moisture content, the tensile strength during the drying process was much greater than in the other two situations. This study provides an alternative perspective on the source of soil tensile strength and its main controlling factors.

Global Research Trends in Engineered Soil Development through Stabilisation: Scientific Production and Thematic Breakthrough Analysis

Soil, a naturally occurring resource, is increasingly used as a construction material. Stabilisation strengthens soil, which is weak as an engineering material. Stabilising soil changes its physical qualities, enhancing its strength. Soil stabilisation increases the shear strength and load-bearing capacity. Soil stabilisation refers to any endeavour to change natural soil for engineering purposes using physical, chemical, mechanical, or biological methods, or a mix of these. Strengthening road pavements includes improving the load-bearing capacity, tensile strength, and performance of unstable subsoils, sands, and waste materials. Due to market demands and scientific advances, the number of soil-stabilising additives has increased. These innovative stabilisers include reinforcing fibres, calcium chloride, sodium chloride, and cross-linking water-based styrene acrylic polymers, which are geopolymers that boost the load-bearing capacity and tensile strength of soil. Many materials are being explored for soil stabilisation. In this article, the authors investigated the direction of soil stabilisation research. Scientometric analysis identifies stabilisation challenges and research trends in the field. This study analysed research patterns by countries, authors, institutions, keywords, and journals from 1959 to 2023; in 2021, 150 articles were published, which was the highest number in a year. Citations peaked at 3084 in 2022. With 253 publications and 3084 citations, India was the most productive country. Iran and France published the fewest, 34 and 33, respectively. The Islamic Azad University and the National Institute of Technology had the fewest published articles with 17 articles. This work can help track soil stabilisation research and will serve as an information document for future research.

Effects of Drying and Wetting Process on the Tensile Strength of Granite Residual Soil

The tensile strength of granite residual soil has different changing laws during the wetting and drying process which often appears after rainfall. The microscopic relationship between tensile strength, bond force, and absorbed suction was studied using a self-developed soil tensile strength tester. The results show the following. (1) The change in tensile strength with saturation is a convex curve with a peak; according to the drying and wetting path, there are differences in peak value and amplitude of variation. (2) The sample with a higher fine particle content has a structure that is denser and has fewer pores, while an increase in gravel content will significantly reduce the tensile strength of the soil. (3) Absorbed suction and bond forces are important factors that control tensile strength in the drying process. The bond force contributes more than 70%, the tensile strength is in invariable constant saturation, and the wetting process is mainly controlled by absorbed suction.

Effect of oxide nanoparticles on soil water retention curve and soil tensile strength

Generally, nanotechnology plays very important roles in various applied scientific fields. Iron and magnesium nanoparticles can cause positive or negative changes in physical and mechanical properties of soil, especially in long periods. The aim of this study was to investigate multi-year effects of nanoparticles on soil water retention and tensile strength of the aggregates. Samples of a loamy soil were mixed with 1%, 3%, and 5% levels of MgO or Fe3O4 nanoparticles, in three replications, and incubated for three years. Water contents were measured at different matric suctions of 0, 1, 2, 4, 6, 10, 30, 100, 1500 kPa. The van Genuchten model was fitted to the moisture data. Tensile strength was measured on 2–4 mm aggregates at matric suctions of 30 and 1500 kPa. The results of this research showed that the levels of 1% and 3% of nano-iron oxide significantly increased water retention to 0.64 and 0.63, respectively, compared to the control (0.39) and 5% nano-magnesium oxide (0.19), which is probably due to the increase of adsorption surfaces in the treated soils. Water content at field capacity and permanent wilting point conditions in 5% magnesium nano-oxide treatment were decreased to 0.25 and 0.13, respectively, compared to other treatments, due to the increased soil vulnerability and affecting soil fine pores. Iron oxide nanoparticles did not have any significant effect on soil tensile strength. Based on the results of this study, physical and mechanical properties of soil could be affected by use of nanoparticles.

General variational solution for seismic and static active earth pressure on rigid walls considering soil tensile strength cut-off

General variational solution for seismic and static active earth pressure on rigid walls considering soil tensile strength cut-off

Roles of vetiver roots in desiccation cracking and tensile strengths of near-surface lateritic soil

Desiccation cracking is a major cause of shallow failure of lateritic soil slopes. Knowledge of soil tensile strength helps better understand the cracking behavior of vegetated lateritic soil. This study aims to examine the surficial cracking behavior and tensile strength of remolded lateritic soil containing horizontally arranged vetiver roots. Desiccation cracking tests, root pullout tests and direct tensile tests were performed on lateritic soil considering various porosities, degrees of saturation, and root contents. The mechanism underlying the root reinforcement was analyzed by scanning electron microscopy. The results demonstrate that adding 0.4% grass roots can reduce the crack width and crack intensity factor, and thus mitigate crack developments in lateritic soil. The interfacial shear strength exhibits a decreasing trend with increasing root diameter. As the root content increases from 0% to 1.0%, the tensile strength of lateritic soil increases to reach the peak at a root content of 0.4%-0.5% and then drops greatly. This is why the optimal root content in resisting crack development is about 0.4%. Microscopic tests show that the interfacial shear strength originates from the friction, interlocking force, cementation and capillary force between the rough root surface and surrounding soil particles. A power function-based empirical equation expressed by the root diameter and porosity is proposed to estimate the interfacial shear strength of rooted lateritic soil. Additionally, a semi-theoretical equation of the tensile strength of rooted lateritic soil is deduced based on the tensile strength of soil matrix and the interfacial shear strength between the roots and soil matrix. This equation considers the root content and root diameter distribution and is applicable to the soil of different state parameters (e.g., porosity, degree of saturation and water content). The results could provide insights into the mitigation of desiccation cracking in lateritic soil slopes with root-reinforcement technology.

Changes in salinity, aggregates and physicomechanical quality induced by biochar application to coastal soil

ABSTRACT Coastal clayey soil has a great potential for food production and safety while poor physico-mechanical properties have impeded its sustainable utilization. A field experiment was conducted to assess the influence of biochar on physicomechanical properties of coastal clayey soil. The biochars were applied to the coastal soil with the rate of 0, 1%, and 3% (w/w), respectively. Compared with control treatment, the application of three biochars (at the rate of 3%) had significantly improved soil fertility, i.e. organic carbon, total nitrogen, available nitrogen and available phosphate, respectively. Biochar treatments significantly increased soil porosity, and aggregates stability, while reduced the soil salinity compared to the control treatment. Meanwhile, biochar application significantly increased the plastic index of coastal clayey soil while decreased soil tensile strength and shrink swell properties compared to the control. Biochar clearly altered soil pore characteristics, consequently rebuilding the new ions leaching channels. Overall, the cow manure biochar (650 °C) at the rate of 3% treatment showed maximum efficiency on soil salinity, fertility, physicomechanical properties, and crop yield. The biochar amendment improved coastal soil by ameliorating soil pore space and structure, improving soil tillage operation and rice yield, decreasing salt stress, and reducing mechanical strength.

Dynamic of Change in Soil Physical Properties and SoyBean Growth through The Application of Biochar on Lombok Vertisols

Vertisol is a type of soil whose mineral fraction is dominated by 2:1 type clay minerals (smectite) which have the property of swelling-shrinking periodically as the soil water content changes. However, these physical properties can be improved by the application of biochar so that it can support plant growth. The aim of this study was to evaluate the effect of biochar on changes in the physical characteristics of vertisols soils and growth performance of soybean plants. This research was conducted in Kawo Village, Pujut District, Central Lombok. This study was designed to test the application of two types of biochar, namely rice husk biochar (BS) and corn cob biochar (BJ) at several doses, namely 0, 15, 30 and 60 g/kg of vertisols soil and design using a randomized block design with 6 replications. The parameters measured were unit weight, soil density, porosity, soil tensile strength, available water capacity, aggregate stability, cole value, crack pattern and soybean growth test. The results showed that the application of biochar could improve the physical properties of vertisol soil and also has implications for improving the growth of soybean plants. Observational data showed that a dose of 60 g/kg of biochar, both rice husk and corn cob biochar, showed better changes in soil physical properties compared to biochar doses of 15 g/kg, 30 g/kg and without the addition of biochar. Besides that, the treatment of rice husk and corn cob biochar at a dose of 60 g/kg gave better vegetative growth of soybean plants.

Growth Mechanism of Ice Lens in Saturated Clay Considering Surface Charge

The main purpose of this study is to reveal the growth mechanism of ice lens in saturated clay. The deformation and fracturing of clay skeletons caused by ice crystal growth during the freezing process are gradually discussed, and a theoretical model for the whole process of ice lens growth considering the surface charge is proposed. Firstly, the electrical properties of clay surfaces and the pore structure characteristics of frozen clay are introduced, and the stress of pore walls during the growth of single pore ice crystals is calculated. Secondly, the values of parameters in the theoretical formula of separation pressure between adjacent clay particles are given when considering the linear elasticity of clay. Finally, the formation mechanism of the new lens is described, and the crack growth velocity equation is given. This paper shows that: there is a good consistency between the soil tensile strength of the macroscopic dimension and the intergranular separation pressure of the molecular dimension in judging the production conditions of the new lens; the formation of the new ice lens is the result of the destruction of the pore structure and the propagation of cracks caused by the growth of ice crystals, and more pore freezing can be caused only when the infiltration path of the ice crystals is formed in the pore structure. In order to verify the model, the ultimate compressive strength of soil calculated in this study was compared with the existing test results, and the rationality and correctness of the model are discussed. This study is of great significance to accurately understand the frost heave process.

A study to investigate the effect of different proportion of ultrafine slag and calcium-based activator for sustainable crack mitigation of marine soil

Marine soils are prone to cracking and shrinkage during drying. Various infrastructure facilities constructed on marine soils may experience safety and stability issues due to cracking of soil, that results in accelerated ingress of water, increase in compressibility of soil, reduction in bearing capacity of soils, slope erosion and reduction in its stability. Hence studies focused on sustainable crack mitigation are necessary to improve its engineering properties. In this regard, the present study explores the role of ultrafine slag (US) with calcium-based activator (lime(L)/cement (C)) for sustainable crack mitigation of marine soil (MS). Crack and shrinkage intensity factor (CSIF) has been utilized to quantify the cracking and shrinkage characteristics for unstabilized and stabilized marine soil. The study confirms CSIF reduction upto 50 % for MS + 12 %US + 3 %L, while crack mitigation has been achieved for different combinations (MS + 7 %US + 3 %L, MS + 12 %US + 3 %L, MS + 13 %US + 2 %L, MS + 9 %US + 1 %C, MS + 13.5 %US + 1.5 %C). It has also been observed based on indirect stability test (crumb test) that MS + 12 %US + 3 %L exhibits enhanced stability to water inundation, followed by MS + 7 %US + 3 %L, as compared to other combinations of stabilized soil that exhibited effective crack mitigation. The evaluation of cone penetration resistance (an indirect measure of shear and tensile strength of soil) of unstabilized and stabilized marine soil specimen, at different water contents, suggests that tensile strength of soil shall be higher than tensile stresses at all times, for crack mitigation. The findings of the study may be useful towards possible utilization of ultrafine slag with lime/cement for stabilization of in situ marine soil/dredged material in offshore/near shore environment.

Tensile Strength of Class F Fly Ash and Fly Ash with Bentonite Addition as a Material for Earth Structures.

The behavior of soils under tensile stress is of interest to geotechnical engineers. Tensile strength of soils is often associated with tensile fractures that can generate a privileged flow path. The addition of bentonite improves the plastic properties of the soil, therefore the study was conducted for the compacted class F fly ash and fly ash with various bentonite additions. An amount of bentonite was: 5, 10 and 15%, calculated in weight relation to dry mass of samples. The tensile strength of compacted clay was also established, for comparison. Laboratory tests were carried out using the direct method (breaking) on cylindrical samples and the indirect method (the Brazilian test) on disc-shaped specimens. For this purpose, a universal testing machine with a frame load range of ±1 kN was used. It is stated that bentonite considerably influences the tensile strength of the fly ash evaluated with both methods. The tensile strength values obtained with the Brazilian method are comparable or higher than those obtained with the direct method. The achieved tensile strength values of compacted fly ash, improved by 10−15% of bentonite addition, are comparable with the results obtained for clay used in mineral sealing, while the strain at maximum tensile strength is similar in the direct test and lower in the indirect test.

Comparison of Test Methods for Determining the Tensile Strength of Soil and Weak Rocks

Tensile strength is a key parameter governing tensile cracking and subsequent failure of soil or rock mass. Existing methods for measuring tensile strength are mainly designed for hard materials and come with inherent problems. As such, they are continuously being adapted and improved by the scientific community. In line with this effort, we recently developed two new tensile test methods for application to soil and weak rocks, namely, the inner hole fracturing test (IHFT) and horizontal compression test (HCT). In this study, we compared the performance of these newly developed methods and the three most commonly used approaches for tensile strength determination, namely, the uniaxial direct tensile test (UDTT), Brazilian test (BT) and three-point bending test (TPBT). Results show that IHFT and HCT exhibit distinct advantages over the three conventional methods when testing soil and weak rocks: first, IHFT and HCT can overcome the eccentric force problem that is a main challenge in UDTT and BT, and second, results obtained from these tests are highly reproducible and stable. Between IHFT and HCT, the latter is found more suitable for routine laboratory testing because of simpler and easier procedure, more stable and reliable results and uniform stress distribution within specimens.

Unconfined Compressive Strength and Splitting Tensile Strength of Lime Soil Modified by Nano Clay and Polypropylene Fiber

Here we study the effects of nano clay and polypropylene fiber on the unconfined compression and splitting properties of lime soil. Through a series of unconfined compressive strength (UCS) tests and splitting strength (STS) tests, the mechanical properties of lime soil (LS), nano clay modified lime soil (NLS), fiber modified lime soil (FLS), nano clay and fiber composite modified lime soil (NFLS) are analyzed, and the volume calculation formula of each phase in NFLS is deduced. Nano clay content αn, porosity volume η and lime volume LVi as independent variables, and the prediction models of UCS and STS of NFLS were established. Furthermore, the microstructure of LS, NLS, FLS and NFLS was analyzed by scanning electron microscope (SEM). It can be concluded that (1) with the increase in nano clay content, the UCS and STS of LS and FLS gradually increase. With the increase in fiber content, the UCS of LS first increases and then decreases, while the UCS and STS of NLS and STS of LS increase with the increase in fiber content, and the optimal fiber content is 0.75%. (2) UCS and STS of NFLS and η/LVi meet the linear relationship. The empirical formulas of UCS and STS established in this paper have a prediction accuracy of less than 10%. The strength of NFLS can be predicted according to the dry density of the sample and the content of each component material. (3) Nano clay can fill the pores of LS and promote the pozzolanic reaction between lime and soil, while fiber mainly plays a reinforcing role in LS, so as to improve the UCS and STS of LS. In NFLS, nano clay can improve the interfacial properties between fiber and LS, so as to improve its UCS and STS. This study can provide a reference for the modification technology of lime soil.

Influences of the geotechnical characteristics on the durability and tensile strength of soil with additives- A review

Expansive soils exhibit problems in the foundations of the structures during loading and unloading, but by overcoming these problems, the soil is stabilized with additives in the proper percentages. Later on, the stabilized soil was affected and showed more problems with weather conditions subjected to durability characteristics such as freeze, thawing, wetting, drying, sorptivity, and diffusivity. This paper deals with the previous studies on the influence of the geotechnical properties on durability and the tensile strength of the soils with additives. The geotechnical properties, mainly of index and engineering, varied with durability. This paper also explains the previous methodologies like freeze–thaw cycles, wetting–drying cycles, sorptivity-diffusivity, and tensile strength with stabilizing agents. The durability characteristics changed due to drastic variations in temperatures and affected more of the soil.

Development of polymer binder for properties enhancement of soil cement

The use of polymer emulsion for soil stabilization has been used to improve the engineering properties of natural soils. This study investigated the feasibility of using styrene-butadiene (SB) emulsion, acrylic copolymer and blending of SB and acrylic copolymer (SB/acrylic) to improve the properties of concrete-stabilized soil. The influence of polymer content and blending ratio on the unconfined compression strength (UCS), indirect tensile strength (ITS) and water permeability of concrete-stabilized soil were investigated. The results reveal that the addition of SB, acrylic copolymer and SB/acrylic change the behavior of the concrete-stabilized soil from brittle to ductile behavior. The UCS and ITS of concrete-stabilized soil decrease with increasing polymer content due to the high water content of polymer emulsion in the mixture. The increase in acrylic ratio in SB/acrylic blend results in a decrease in UCS, ITS and toughness of concrete-stabilized soil. The purposed mixture holds promising application value in sustainability road construction.

The Effect of Geotextile Layers and Configuration on Soil Bearing Capacity

The term "reinforced soil" refers to a composite material with high tensile-strength components that enhance the soil's tensile strength. One of the most common kinds of geosynthetic fabric utilized for soil reinforcement is geotextiles. This article investigates woven geotextile's potential benefits in enhancing the maximum load-carrying capacity of footings resting upon silty sand soil. The foundation was constructed of a 10 mm thick strong carbon steel plate of 100 mm×100 mm. The factors examined in this research were the first geotextile layer's depth, the geotextile layer's width, the number of layers of reinforcing material, and the vertical spacing between geotextile layers. The impact of geotextile strengthening configurations on the load-carrying capacity of strengthened soil foundations was also studied. The results of the experiments indicated that geotextile reinforced soil could help to grow the soil bearing capacity. The testing findings revealed that the system with three geotextile layers, 0.25B vertical distance among geotextile layers, and a geotextile width of 5B, B denotes the plate's width, achieves the most significant bearing capacity. The test findings also revealed that the reinforcement configuration greatly impacted the reinforced silty sand on the foundation's behavior.

Sample dimension effect on equations controlling tensile and compressive strength of cement-stabilized sandy soil under optimal compaction conditions

The porosity/cement ratio (η/Civ) has been applied as a key parameter for the understanding of tensile and compressive strengths of a wide range of soils-cement mixtures, although the focus has been restricted to non-optimal compaction condition, which does not fully reflect the field execution process. Also, distinct sample dimensions have been utilized in the research area without taking this effect into account. Recognizing these needs, this study aims to evaluate the sample dimension effect on the equations controlling the mechanical behavior by η/Civ, under optimal compaction conditions. Using sandy soil, Unconfined Compressive Strength (UCS or qu) and Indirect Tensile Strength (ITS or qt) tests were performed from distinct curing period, cement type and content, based on conventional (127×100 mm) and reduced dimension (105×50 mm) specimens. The addition of both cements did not show significant variations in compaction parameters, which affected the η-qu and η-qt relations. The use of η/Civ ratio proved to be a suitable parameter for dosing, considering both sample dimensions under optimal compaction conditions. A unique exponent related to the increment of qu and qt along 7 and 28 curing days was obtained by each cement type, regardless of the sample dimension, leading to an average of 0.13 qt/qu relationship. Finally, mixtures molded in reduced dimension showed 20% higher strengths when compared to conventional dimension, despite the cement type and content, porosity, and curing period.

Liquid-Bridge Contact Model of Unsaturated Granular Materials and its Application in Discrete-Element Method

In the past, the capillary effect is rarely considered for microcontact models when two adjacent particles are separated by a certain distance. In this paper, a liquid-bridge contact model of unsaturated particles is presented, which is applied to the discrete-element software PFC. Based on this, simulations of uniaxial tensile for unsaturated soils under (2D) situation are carried out, and influence of a water retention angle on uniaxial tensile strength are studied. The simulation results show that the uniaxial tensile strength of unsaturated soil decreases gradually with the increase of the water retention angle, obvious cracks generate at both ends of the soil samples, and the soil sample possesses a residual strength. According to the particle displacement field, velocity field, and contact force chain, the failure forms of samples with different water retention angles are determined. Based on the rose diagram of normal contact force, the changes of its direction and value during failure process are observed directly, so as to analyze the evolution law of contact force for unsaturated soils.

Tensile Strength of Compacted Clays during Desiccation under Elevated Temperatures

Abstract The tensile strength of unsaturated soils is a critical factor controlling the initiation and propagation of desiccation cracks, which can threaten the structural integrity of natural and man-made earthen structures and slopes. Several engineering applications involve unsaturated soils subjected to elevated temperatures (e.g., earthen structure-atmospheric interaction under prolonged droughts, nuclear water disposal, energy piles, ground source heat pumps). Although the temperature dependency of desiccation cracking is demonstrated in the literature, critical gaps remain regarding the characterization of the tensile strength under elevated temperatures. The main objective of this study is to investigate the effect of elevated temperature on the tensile strength of unsaturated clays during desiccation. To accomplish this objective, a novel testing setup that can be used to directly determine soil tensile strength during desiccation was placed in an oven to measure the tensile strength of two compacted clayey soils of medium to high plasticity under different temperatures ranging from 20°C to 60°C. The clays are compacted at 95 % of their respective maximum dry unit weights over a range of water contents from dry to wet of optimum to investigate the influence of initial water content on tensile strength. The results demonstrated that the tensile strength decreased with increasing temperature. At the optimum water content, a tensile strength reduction of 36 % and 27 % in the highly plastic clay and the medium plastic clay, respectively, was observed when the temperature increased from 20°C to 60°C. Additionally, for the partially saturated condition, the initial water content affected the tensile strength significantly. Temperature-induced changes in key factors contributing to the tensile strength of unsaturated clays are discussed to provide further insight into tensile strength of clays at elevated temperatures. The findings of this study can contribute toward a more realistic analysis and design of earthen structures subjected to elevated temperatures.