Strength Characteristics Of Soil Research Articles

Stabilization of Expansive Soils Using Flyash

Abstract: Soil plays an essential role in the construction of any civil engineering structure. It must be able to withstand the loads without breaking down. In some areas, the soil may not be strong enough to withstand the incoming loads. To address this, there are many methods of soil stabilization available, but some of these methods, such as chemical stabilization, lime stabilization, etc., can have an adverse effect on the soil's chemical composition. In this paper, we will be looking at the effects of fly ash on the strength gain of an expansive clay soil when combined with different percentages of fly ash, such as 0%, 5%, 10%, 15%, 20%, and 25%. We will also be looking at tests to determine the strength gain of the soil with and without fly ash. The results of the laboratory study will show that adding fly ash to the expansive clay soil reduces the soil's plasticity index and increases its MDD. The expansive clayey soil's strength characteristics have improved.

Shear strength degradation of gas hydrate-bearing sediment due to partial hydrate dissociation

Extraction of methane hydrate from subseafloor reservoir may potentially trigger seabed slides and induce subsidence. To address the problems, it is crucial to properly characterize the phase equilibrium condition of pore hydrate and the shear strength of the soil. As one of the key constitutive components, the phase equilibrium condition enforces a constraint over pore gas pressure, temperature and unhydrated water content. Such a constraint, however, has been traditionally ignored in analyzing the mechanical behavior of hydrate-bearing soil. In this paper, a series of stepwise hydrate dissociation tests was performed, and the phase equilibrium condition of pore hydrate was determined, providing an effective way to evaluate the unhydrated water content during hydrate dissociation. Meanwhile, a series of direct shear tests was also conducted to explore the shear strength characteristics of the soil. It is shown that the shear strength of the hydrate-bearing soil can be significantly influenced by pore gas pressure, unhydrated water content, hydrate saturation and several other factors. In particular, the measured shear strength depends upon the initial water content of the sample, pointing to a potential problem that the shear strength could be wrongly determined if not properly interpreted. A shear strength criterion, which enforces the equilibrium condition of pore hydrate, is developed for hydrate-bearing soil, establishing a link between the equilibrium condition and the shear strength. The proposed equation describes well the shear strength characteristics of hydrate-bearing soils, remarkably unifying the effects of pore pressure, temperature, water content and hydrate saturation.

Effect of industrial waste on the behaviour of expansive soil

The expansive soil has serious impact due to its unstable volumetric behaviour when it undergoes seasonal variations. In order to utilise the problematic expansive soil for any kind of work it needs to alter the behaviour of soil by stabilisation using addition of admixtures. From the economical point of view using industrial waste materials is the cost-effective technique. In this work the selection of industrial waste materials which comes from tile manufacturing such as Tile Waste Powder (TWP) and Foundry Sand (FS) outcome of metal casting industries as an admixture. The Tiles Waste Powder has the nature to improve the compaction behaviour of expansive soil because of its high lime content and Foundry sand are used to develop the strength behaviour of problematic soil due to the presence rich silica content. In this paper, untreated soil got treated using the different proportions such as 5,10, 15,20 and 25% of Tile waste powder and their corresponding the compaction and strength characteristics of the soil sample were determined under different curing periods. Also the tests have been conducted for optimum percentage of tile waste mixed along with varying percentage of Foundry Sand (4, 6, 8, 10 and 12%) in soil sample. The results was obtained from the standard proctor test, UCC and CBR test and it further analysis shows that the increasing the proportion of TWP rises the peak strength of the treated soil up to 20% for the maximum 28 days curing. Also, from the result analysis for the combination of FS and TWP by optimum percentage of Tiles Waste Powder (20%) with 12% of Foundry sand shows the increment in the strength characteristics of soil. The TWP and Foundry Sand can be effectively used in stabilization works in order to utilise the waste by effective minimization of disposal problems.

Учет переувлажнения грунтов при проектировании нагельного крепления склонов

Nail slope support has proven itself as an effective engineering protection measure, which is used to increase the stability of slopes, and involves the installation of drilling-injection ground nails together with a flexible cover system. The article considers the issue of improving the existing design methodology of this type of structure, which will include an assessment of the overall stability of the slope, an assessment of the local stability of the surface layer, considering soil moisture saturation, checking the strength of the nail on the ground and material, as well as checking the strength of the nail attachment (ground nail and steel network) on slice. To achieve this goal, there was carried out a selection of soil nailing support for the considered engineering-geological section using the Plaxis 2D PC and there was offered an analytical method for calculating slope stability. The authors also propose a method that can be used for assessing the strength characteristics of soils of the surface layer, considering excessive soil water saturation.

Shear bond and compressive strength of clay stabilised with lime/cement jet grouting and deep mixing: A case of Norvik, Nynäshamn

Abstract The strength of soil can significantly increase by stabilisation with binders. Adding binders in correct proportions to improve soil parameters is of paramount importance for earthworks. In this article, we presented a framework to explore strength characteristics of soil stabilised by several binders and evaluated using applied geophysical methods by estimated P-wave velocities. The core of our work is a systematic assessment of the effects on clay stabilisation from various binders on shear and compressive strength. The binders were combined from four stabilising agents: (i) CEM II/A, a Portland limestone cement; (ii) burnt lime; (iii) lime kiln dust (LKD) limited up to 50%; and (iv) cement kiln dust (CKD). Shear strength has shown a nonlinear dependence as an exponential curve with P-waves. Natural frequency analysis was modelled to simulate resonant frequencies as eigen values. Variations in strength proved that CEM II/A-M (Recipe A, 100% CEM II) has the best performance for weak soil stabilisation followed by the combinations: Recipe B (70% CEM II/A-M, 30% LKD), Recipe C with added 80% CEM II/A-M and 20% CKD, and Recipe D (70% CEM II/A-M 30% CKD). Recipe B has shown high values with maximum uniaxial compressive strength (UCS) at 13.8 MPa. The Recipe C was less effective with the highest value of UCS as 8.8 MPa. The least strength was shown in Recipe D, where UCS has maximal values of 3.7 MPa. The specimens stabilised by Recipe B demonstrated the highest P-wave velocity at 2,350 m/s, while Recipe C and Recipe D showed the highest P-wave velocity at 1,900 and 1,550 m/s. All specimens shown a gain of UCS with sharply increased P-wave speed during the 3 days of curing. The study contributes to the development of methods of soil testing in civil engineering.

RESEARCH OF METRO TUNNEL SEDIMENTS UNDER THE CONDITIONS OF A WATER-SATURATED FLOOD MASSIVE

Purpose: analysis and selection of an appropriate way to improve the strength characteristics of soils by strengthening in the zones of weakening and reducing deformations of the tunnel structures, substantiating the methods of strengthening the base of the subway tunnel structure and the soil massif during deposition in the conditions of the underground space. On the basis of the analysis, propose an expedient method and schematic fixing of a water-saturated non-washable soil massif with stabilization of sediments and propose a method for reducing deformations during vibration subsidence.
 Methodology: by using the survey and analysis of methods of strengthening the soil massif, geophysical methods of strengthening the foundations of the sandy water-saturated massif, a comprehensive approach is recommended for the implementation of increasing the level of strength of the subway tunnel.
 Originality: on the basis of the performed analytical studies, the parameters for strengthening the soil of the water-saturated alluvial massif were determined and the combined method of strengthening the soil massif and the method of reducing the vibration subsidence caused by the speed of the trains in relation to the force of gravity during the oscillation of the structure of the base of the subway tunnel in the water-saturated alluvial massif were proposed. optimization of works, reduction of work terms and the possibility of applying a combined scheme of filling wells with solution and using them in conditions of dense urban development.
 Findings and practical implications:  the combined scheme of strengthening the soil massif with the help of gas silicification and the installation of soil-polymer piles will allow to evenly reduce the sedimentation of the soil and the structure without harming the surrounding underground space and dense urban development, in particular, it will increase the strength characteristics and the service life of the distillation tunnel.
 Keywords: physical and mechanical properties; water-saturated alluvial massif; subway tunnels; shallow laying; geophysical methods; tunnel deposition; tunnel fastening, gas silicification; low viscosity polyurethane.

Applications of Microbially Induced Calcium Carbonate Precipitation on Non-Woven Geotextiles

Recently, an innovative ground improvement method known as microbially induced calcium precipitation (MICP) has been proposed as an alternative to conventional ground improvement techniques. Having numerous advantages such as being environmentally friendly and promoting sustainable solutions, MICP has been studied by researchers from various civil engineering sub-disciplines to solve problems related to crack propagation of concrete, insufficient soil strength characteristics, soil erosion, asphalt cracks, etc. This study aims at moving MICP one step further by introducing a hybrid approach that combines MICP and geotextiles to produce a good quality product for reliable field use. Within this scope, MICP is applied on non-woven geotextiles. Physical (imaging) and mechanical (puncture resistance) properties of non-woven geotextiles subjected to MICP treatments under soaking conditions are investigated. Puncture resistance tests are performed and the details of laboratory work including specimen preparation and MICP treatments are presented in this paper. This study, together with its implications for future works, also highlights the next steps to be taken for properly using the MICP method when other geosynthetics are used.

Study on the Fractal Characteristics of the Plant Root System and Its Relationship with Soil Strength in Tailing Ponds

To study the fractal characteristics of plant roots in tailing ponds and their effect on soil strength, the rhizosphere soil and roots of Amorpha fruticosa and Hippophae rhamnoides, which are widely distributed in ecological restoration areas, were collected. The fractal dimension, root fractal characteristics, soil strength characteristics, and interaction relationships of the two rhizosphere soils were studied. Fractal theory was used to derive the formula for calculating the safety factor of the slope considering the soil and root fractals. The results showed that (1) the fractal dimension of rhizosphere soil of A. fruticosa and H. rhamnoides decreased with increasing vertical profile depth. (2) The fractal dimensions of roots of A. fruticosa and H. rhamnoides decreased with increasing soil depth. (3) The cohesion of the root-soil complex first increased and then decreased, and the fractal dimension of roots was significantly positively correlated with the increase in cohesion. (4) The slope safety factor was positively correlated with the fractal dimension of the soil and root system. It established the theoretical formula of the slope safety factor modified according to the fractal dimension.

Evaluation of Strength Characteristics of Soil Stabilized with Nano Zinc Oxide—Cement Mixes for Low Volume Road Applications

Evaluation of Strength Characteristics of Soil Stabilized with Nano Zinc Oxide—Cement Mixes for Low Volume Road Applications

Technological regulation and monitoring of roadbed construction

Background: Long-term deformations of hydraulic structures on weak foundations and swamps lead to the need to develop new construction technologies that increase the bearing capacity of soils. The existing standards for the design of railways and highways are mainly focused on ensuring the safety of the roadbed at the operational stage. Meanwhile, the risks of loss of stability and stability of road sections also arise at the construction stage, especially when powerful heavy construction machinery and equipment are operating.
 Aim: Formation of a technical and technological system functioning on the principles of direct and feedback between the characteristics of the constructed roadbed and the parameters of construction equipment to ensure the safety and quality of work.
 Methods: Technological regulation of loads and impacts of construction machinery and equipment during the strengthening of the foundation and the construction of embankments of the roadbed.
 Results: The composition of the complex technology and the regime of regulation of construction loads have been developed to increase the bearing capacity of weak soils at the base of the roadbed of railways and highways. The features of geotechnical monitoring for the directed improvement of the strength characteristics of soils during the construction period are determined. The expediency of technological regulation of loads and impacts of construction machinery, equipment during the construction of the roadbed is shown.
 Conclusion: The complex technology of increasing the load-bearing capacity of the weak foundation of the roadbed consists in the consistent application of regulated modes of intensive impact on each layer of the foundation with the maximum permissible load during geotechnical monitoring.

Evaluation of the Strength Characteristics of Silty-Clayey Soils during Freezing-Thawing Cycles

Destructuring settlements due to frost heave during the structures’ exploitation are often not taken into account at the designing stage, although they are indirectly related to the bearing capacity of the soils. The objective of this research was analyzing the effect of the number of freezing-thawing cycles on the strength characteristics of soils. A paired experiment with various initial parameters (void ratio, initial moisture content, and the number of freezing-thawing cycles) was carried out. According to the experimental results, the cohesion largely depends on the above parameters which might lead to its decrease by up to three times. The angle of internal friction demonstrated an indefinite behavior during the freeze-thaw cycles, which is confirmed by a literature review. Freezing–thawing cycles significantly decrease the soil bearing capacity: up to 44% after 10 freezing-thawing cycles for soil with e=0.55 and  w=16.5%. However, in the case of e=0.75 and w=22.6%, it increased by 33%. A program based on the least-squares method was used to calculate the approximation coefficients of the dependence describing the changes in strength characteristics from the abovementioned parameters. Changes in strength characteristics must be taken into account when designing structures, as they can lead to additional settlement or even subsidence of the foundations.

Effect of Prior Cyclic Loading on Triaxial Compression Strength of Sliding Zone Soil of the Huangtupo Landslide

Earthquakes or cyclic loadings cause significant changes in the strength characteristics of soil. These changes, especially for sliding zone soil, can lead to catastrophic landslides. Taking into account this characteristic, this paper investigates the effects of prior cyclic loading on the consolidated undrained triaxial compression strength of sliding zone soil with the KTL triaxial automated system. Our experimental results indicate that the prior cyclic loading has a significant effect on the strength behaviour of saturated sliding zone soil. Under different confining pressures, cycle periods, and number of cycles, the samples exhibit the characteristics of strain-hardening. Deviatoric stress under cyclic loading condition is smaller than that with monotonic loading condition under different confining pressures, cycle periods, and number of cycles. As the confining pressure and cycle period increase, the failure stress ratio decreases. The axial strain exhibits a steep rise first and then stays stable under a cycle period of 90 s, while the axial strain shows a linear increase with an increase in the number of cycles under a cycle period of 10 s under confining pressures of 100 kPa and 400 kPa, respectively. The logarithmic relation correlates well with the failure stress ratio in the cyclic loading tests, which preliminary validates the applicability of logarithmic relation for sliding zone soil influenced by prior cyclic loading, providing a theoretical basis and guidance for the further understanding of strength characteristics of sliding zone soil.

Reuse of COVID-19 face mask for the amelioration of mechanical properties of fat clay: A novel solution to an emerging waste problem

Not only has the COVID-19 pandemic caused a global health crisis, but it has also changed the dynamics of waste generation around the world. This situation demands a productive solution for face mask (FM) waste management to solve several associated environmental issues. In the current study, a novel soil treatment method is proposed for the improvement of mechanical characteristics of fat clay by using FM as fiber reinforcement and silica fume (SF) as the cementitious agent in the form of a composite binary admixture (CBA). The performance of the proposed CBA is compared with SF and FM as the lone stabilizers by conducting extensive geotechnical testing. The SF treatment exponentially improves the strength characteristics of soil but it marginalizes the ductility of soil, inviting sudden failure and instability under dynamic loadings. It is observed that the proposed CBA not only improves the strength characteristics more than SF but also regulates the ductility and deformability of treated soil due to the presence of FM fibers. In addition, the policies and protocols on the logistics of collecting FM waste and making it ready for the proposed geotechnical application are reviewed; associated health risks, socioeconomic conditions and available technologies are the major governing factors to formulate and implement these policies. Moreover, the prolonged storage of COVID-19 FM waste for disinfection is found to be suitable for the proposed soil stabilization method as per the literature. The current study helps in achieving cost-effective filler/foundation material, solving COVID-19 FM waste problems and promoting resource conservation.

Stress-strain state of a borehole determined analytically using drilling-out as a technology of reducing differential settlement

The existing approaches for reducing the differential settlements of buildings and structures have their own advantages and disadvantages. Lowering of a building or part of it is one of the promising methods to reduce the differential settlements of shallow foundations resting upon weak silt-loam soils. The effect is achieved by drilling-out vertical boreholes in the immediate vicinity of the foundation from the minimal settlements. Method: Russian and foreign scientists have been involved in the development of calculation procedures for horizontal and inclined drilling-out of boreholes. It has been important to determine drilling parameters when using this technology and how soil characteristics and stress state of soils around the borehole influence the reduction of differential settlements. The paper discusses the influence of the strength characteristics of soils on the stress state of the soil massif around the borehole, as well as the influence of the borehole radius on the formed areas of limit state. The analytical solution is based on the well-known ratio used to determine the stress state around the borehole during pressure tests. Tangential and radial stresses are determined from this ratio; next, they are checked according to the condition of the strength law, and thus, the stress state around the borehole becomes evident. Result: The stress state of the soil around the boreholes has been calculated by the given method; it has made it possible to calculate the areas of soil destruction and determine the parameters of boreholes and their geometry depending on the purposes when regulating the settlements of slab foundations. It has been established that drilling behind the foundation contour in relation to drilling in the foundation contour makes it possible to increase the radius of the plastic deformation zone up to two times under the same soil conditions and well geometry.

The Strength Behaviour of Eggshell Powder Substitution on Soil-lime Stabilization

This study explored the investigation into enhancing soil strength characteristics using eggshell powder (ESP) as a lime substitution on soil-lime stabilization. The ESP was naturally available while using this material, which could reduce cost and other environmental effects. The influence of varying percentages of eggshell powder as a lime substitution in changes of the strength and durability is observed based on the unconfined compression test conducted on two soil and two lime types (hydrated lime and quicklime). Influence factors were studied, including soil and lime types, ESP content, curing time, and durability against wetting-drying (w-d) cycles. The unconfined compressive strength (UCS) and the durability values of ESP-stabilized soils decreased, while ESP content increased. However, this value was higher than the unstabilized ones. The ESP substitution on soil-lime stabilization marginally affected the strength and durability of soil-lime stabilization. The UCS increased with the increasing curing period for all specimens. Soils with more clay particles reacted better to both hydrated lime and quicklime. Additionally, strength development occurred in soil-quicklime mixtures more than in soil-hydrated limes. Based on a durability test, it was known that the maximum ESP substitution was 50% from the Optimum Lime Content (OLC); beyond that content, the strength of soil might dramatically be degraded.

Unconfined compressive strength prediction of soils stabilized using artificial neural networks and support vector machines

This study aims to improve the unconfined compressive strength of soils using additives as well as by predicting the strength behavior of stabilized soils using two artificial-intelligence-based models. The soils used in this study are stabilized using various combinations of cement, lime, and rice husk ash. To predict the results of unconfined compressive strength tests conducted on soils, a comprehensive laboratory dataset comprising 137 soil specimens treated with different combinations of cement, lime, and rice husk ash is used. Two artificial-intelligence-based models including artificial neural networks and support vector machines are used comparatively to predict the strength characteristics of soils treated with cement, lime, and rice husk ash under different conditions. The suggested models predicted the unconfined compressive strength of soils accurately and can be introduced as reliable predictive models in geotechnical engineering. This study demonstrates the better performance of support vector machines in predicting the strength of the investigated soils compared with artificial neural networks. The type of kernel function used in support vector machine models contributed positively to the performance of the proposed models. Moreover, based on sensitivity analysis results, it is discovered that cement and lime contents impose more prominent effects on the unconfined compressive strength values of the investigated soils compared with the other parameters.

Study on Tensile-Shear and Compressive-Shear Coupling Strength of Saturated Clay

Traditional soil strength research mainly focused on compressive shear or uniaxial tensile stress state, and rarely considered the tensile-shear coupling strength characteristics in soil. Based on the tensile-shear and compressive-shear coupling strength model established earlier, which consider the tensile-shear coupling strength comprehensively, relevant tests are carried out to verify the strength model. Different types of saturated clay are selected for the uniaxial tensile test, direct shear test and triaxial shear test. The strength model is verified based on experimental data and compared with the existing joint strength model, and the coupling strength model shows good applicability and accuracy. The result shows the strength model can accurately describe the nonlinear strength characteristics of soil under tensile-shear coupling stress.

Influence of freeze–thaw cycling on the soil mechanical properties of open-pit mine dump under different moisture contents

Freeze–thaw circulation under different moisture contents is the main influencing factor of the soil strength characteristics at a dumping site. The fine-grained sand materials of an internal dumping site in the Yuanbaoshan open-pit mine of China were selected as the research object; the changes of soil strength and deformation characteristics of 5 types of freeze–thaw (F–T) cycles were studied under 8 types of moisture contents. The stress–strain curve of soil sample shows strain hardening after different F–T cycles. The shear strength of the soil material decreases unevenly with increasing number of F–T cycles, and the greatest decrease in the shear strength occurs after the first F–T cycle. Under the condition of the same F–T cycles, the cohesion and internal friction angle (shear strength parameters) of the soil material decrease nonlinearly with increasing moisture content and decay in the form of a power function. For the same moisture content, the effect of F–T cycling on the internal friction angle of the soil is small, but the cohesion of the soil decreases as the number of F–T cycles increases, eventually stabilising. A quadratic polynomial equation can accurately describe the quantitative relationship between the cohesion and number of F–T cycles, at the same time, the unified regression equations of cohesion, moisture content and F–T cycle are established. The research results provide an important idea for the design of dumps and slope stability analysis, especially for the first year after dumping.

Impact of RBI Grade-81 on expansive soil strength characteristics

In this research, an attempt is made to understand the impact on strength characteristics of expansive soil treated with Road Building International Grade-81 (RBI-Grade-81) stabilizer. This stabilizer has a wide response spectrum range. A broad range of studies, such as Atterberg limit, Compaction, Unconfined compressive strength (UCS), and California bearing ratio (CBR) measures, are demonstrated on expansive soil and it is treated with percentages varying between 2 and 10% of RBI-Grade-81. Due to the creation of new cement materials, which is apparent in the SEM research micrographs, the improvement in intensity is achieved. The results suggest that considered stabiliser is effective in enhancing the engineering properties of expansive soil.

TO THE STATISTICAL ANALYSIS OF SOIL SHEAR TESTS RESULTS

The result of any shear tests, which are the most popular laboratory methods for determination the strength characteristics of soils, is a set of values of the ultimate shear resistance and the corresponding normal pressure along the shear section. The theoretical background for the analysis of the soil shear tests results is the theory of probability and mathematical statistics. At the same time, we have questions about the determination of the calculation values of soil strength parameters. So, during the processing of shear tests results according to a consolidated-drained scheme for sandy soils the calculation values of soil specific cohesion are often negative, which is incorrect. The article considers an example of processing of shear tests data of sandy loam for various normal pressures, and analyzes the results of statistical processing of soil tests. The normative methods for probabilistic assessment of soil strength characteristics are based on using of normal distribution law of a random variable. It is assumed that the valuesof a random variable can vary from -¥ to +¥, while the soil strength parameters can vary in a limited range, i.e. accept only positive valuesfrom 0 to +¥. This circumstance does not matter for the majority of clayed soils, which strength parameters are far enough from zero. However, it has a significant effect on the result for small sought-for values, particularly, in assessing of specific cohesion for sandy soils. Therefore, for such cases, the article presents a variant of the statistical processing of the shear tests results with using the reduced normal distribution law of a random variable.