Mechanical Properties Of Clay Research Articles

Effect of repeated freeze-thaw cycles on mechanical properties of clay

To investigate the variation in the mechanical properties of clay under freeze-thaw cycles (FTCs), a series of experiments were conducted in the laboratory. Samples with different water contents and dry densities were subjected to FTCs ranging from 0 to 11 times. Then, cohesion, shear strength, internal friction angle and elastic modulus were obtained using triaxial test. The results show that with the increase in the number of FTCs, the shear strength, cohesion and elastic modulus decreased, while the internal friction angle increased slightly. However, the variation in the internal friction angle is not obvious, and the maximum increment is within 4°. The cohesion exhibited the most decrease after the first freeze-thaw action. Besides, under a same number of FTCs, four mechanical properties are significantly affected by water content and dry density. The shear strength, cohesion, elastic modulus and internal friction angle decrease with water content while increasing with dry density. Additionally, the elastic modulus is associated with confining pressure, which increases with confining pressure. This study provides evidence for the variation in mechanical properties of the soils subjected to FTCs and guides the design and construction of the cold regional engineering.

Mechanical properties of defective kaolinite in tension and compression: A molecular dynamics study

Influenced by the external environment, clays often contain a large number of lattice defects inside, and the defects have an essential influence on the physical and mechanical properties of clays. In order to reveal the mechanical properties and deformation failure mechanism of defective kaolinite, kaolinite containing Si vacancy defects was constructed, and the mechanical properties of two types of perfect/defective kaolinite were investigated under uniaxial tensile and compressive conditions, respectively, by using molecular dynamics methods. The anisotropy of the micromechanical behavior of kaolinite and the formation mechanism was revealed. Based on the radial distribution function between atoms, the cutoff distance of individual bonds inside the crystal was determined, and the evolution rules of individual bonds inside the crystal during the deformation and destruction were elucidated. Results showed that the introduction of point defects caused different degrees of reduction in the peak strength and elastic modulus of kaolinite, and the decrease was related to the loading direction, and the decline was more significant for parallel clay layers (x- and y-) than for perpendicular clay layers (z-), with pronounced anisotropy. When the defected kaolinite was extended along the x- and y-directions, the silicon‑oxygen tetrahedral and aluminum‑oxygen octahedral sheets were fractured, and the broken sites were concentrated at the defected locations; when extended along the z-direction, the failure was dominated by the fracture of interlayer hydrogen bonds. When the defective kaolinite was compressed along the x- and y-directions, the failure was mainly caused by the gradual accumulation of the bending of the clay layer, which was distinctly different from the direct fracture under the tensile condition, and when compressed along the z-direction, the clay layer collapsed until it was failure. The tendency of the broken bonds within kaolinite corresponded well with the stress-strain curve, the number of broken bonds increased with the increase of strain, and the number of broken bonds of various bonds stabilized when the crystal structure was destroyed. The bond-break types and the number of bonds broken under different simulation conditions were somewhat different, affected by the layered structure of kaolinite and the loading patterns.

Compressive and Tensile Strength of Nano-clay Stabilised Soil Subjected to Repeated Freeze–Thaw Cycles

Abstract Improvement of the mechanical properties of clayey soils by additional elements to enhance the strength under numerous freezing and thawing cycles has been considered as a serious concern for engineering applications in cold regions. The objective of the current study is to investigate the effect of nano-clay as a stabiliser on the mechanical properties of clay. To this end, the clay specimens were prepared by adding various percentages of nano-clay ranging from 0.5% to 3% by dry weight of soil and were experimentally tested under the uniaxial compression and tensile splitting tests under different curing times (0, 7 and 28 days) after experiencing various freeze–thaw cycles ranging from 0 to 11. It can be concluded from the results that nano-clay particles may be used as a stabiliser in geotechnical applications to improve soil property. The results indicate that the optimum moisture content (OMC) of specimens increases and the maximum dry density (MDD) decreases with the increasing nano-clay content. The specimens containing about 1% nano-clay recorded maximum values of unconfined compressive strength (UCS) as well as tensile strength. For example, the addition 1% nano-clay increased the UCS and tensile values of clay specimens under the curing time of 28 days by 34% and 247%, respectively. In addition, the long-term durability of specimens against freeze–thaw cycles increases further with the addition of nano-clay content ranging from 2% to 3%.

Effects of freeze–thaw actions on mechanical properties and constitutive model for diesel-contaminated soil

Oil pollution is widespread in frozen regions around the world, and the mechanical properties of clay are highly susceptible to prolonged freeze–thaw cycles and diesel pollution. In order to study the properties of diesel-contaminated clay at the influence of freeze–thaw cycles, the laboratory tests are performed here, based on which the mechanical properties of diesel-contaminated soil under freeze–thaw cycles are studied. Additionally, the effects of freeze–thaw cycles and contents of diesel on the microstructure of clay are studied by scanning electron microscopy. The results show that the shear strength and strength parameters of soil samples decrease with the increase of diesel content and freeze–thaw cycles. Moreover, the scanning electron microscopy (SEM) results show that the freeze–thaw cycle and the increase in diesel content increase the number of large pores and decrease the number of small pores. The soil particles coagulate and form larger pores after the soil sample undergoes freeze–thaw and diesel pollution. The appearance of macropores leads to soil compaction worse and soil strength decrease. Based on the poromechanics, the diesel-contaminated soil is considered as porous material, and a constitutive model with consideration of the influence of freeze–thaw cycles and diesel content is established. The model can model the test results and the main features of diesel-contaminated soil can be duplicated relatively well. Therefore, the study can provide some help in understanding diesel-contaminated engineering under freeze–thaw cycles in cold regions.

Effect of the Addition of Nano Alumina on the Mechanical Properties of Clay

Effect of the Addition of Nano Alumina on the Mechanical Properties of Clay

The construction stability of large section tunnel considering the deterioration of clay mechanical properties

The stability of large-section clay tunnels is closely related to the mechanical behavior of the surrounding rock. The mechanical behavior of the surrounding rock is characterized by the coupled response of the physico-mechanical properties of the clay material and the tunnel construction conditions. Therefore, this paper proposes a numerical experimental study based on the response surface method to quantitatively link the stability of large-section clay tunnels with construction factors. It will provide a basis for quantitatively guiding the tunnel construction plan adjustment to ensure its stability. Firstly, the tunnel stability reserve is evaluated by considering the deterioration of physico-mechanical properties of clay surrounding rocks, and the relationship between the tunnel stability index and construction factors is established according to Taylor’s theorem. Secondly, the response surface method and the steepest ascent method are used to find the optimal fitting relationship between the tunnel stability reserve factor and tunnel construction factors. Finally, the analysis of a tunnel application shows that (a) the stability evaluation considering the deterioration of physical and mechanical properties of clay is well representative; (b) the “curved” region of the response of the tunnel stability reserve factor can be effectively determined by the steepest slope method; (c) for the “curved” region, a second-order response surface is more appropriate. This research will reveal the coupling relationship between tunnel stability, physico-mechanical properties of clay, and tunnel construction conditions, which will contribute to the development of intelligent tunnel construction.

Effect of Fabric Layering Sequence and Architecture on Mechanical Properties of Clay, Jute, and Glass Fibers Reinforced Polyester Laminated Hybrid Composites

ABSTRACT Hybrid laminated composites are attracting a lot of attention these days. Indeed, mixing natural and synthetic fabrics in the same matrix completely exploits the components’ greatest properties. However, it has been proven that the use of particles such as clays increases the material performance. Hence, the aim of this study is to produce a new hybrid laminated composite system using the hand lay-up method and compression molding techniques. For this, a layering sequence of plain-woven jute fabrics and different architecture of E-Glass fibers (matt and plain-woven roving fabrics with different grammage) were selected to strengthen a polyester resin modified with a tiny amount of clays. The effects of hybridization, layering sequence, and weaving architecture were evaluated by means of mechanical tests. The dispersion and distribution of the charges in the polymeric matrix were also investigated by studying the material rheological properties. We conclude that the proposed hybridization may result in an optimal, superior, and cost-effective laminated composite that fits all the requirements of a given structure.

Upaya Peningkatan Nilai CBR Tanah Lempung Menggunakan Campuran Kapur, Abu Sekam, dan Serat Fiber

Soil is an important element in supporting development activities in the world of civil construction. One type of soil that is often found in South Sumatra is clay. Clay soil is a type of fine-grained soil that is strongly influenced by water content. Each type of clay has a different carrying capacity value. Therefore, an analysis is needed to test the effect of adding a mixture of materials to the clay. A test was carried out to see the effect of adding mixed materials to the soil. In this test, soil samples were taken from the Banyuasin district and mixed with materials in the form of fiber, husk ash, and lime. For variations in soil mixture testing, 0.1% fiber, 2.5% husk ash, and lime consist of 2.5%, 5%, and 7.5%, as well as plain water. The test results show that the addition of a mixture of fiber, husk ash, and cement can improve the physical and mechanical properties of clay, where the optimum addition variation in the 4th variation is a mixture of soil + fiber 0.1% + husk ash 2.5% + lime 5%, which is 52.49%.

Shear Strength Improvement of Clay Soil Stabilized by Coffee Husk Ash

Finding alternatives to natural resources is important for a sustainable future and is essential to infrastructure projects. Among these replacements is the use of coffee waste as soil stabilizers. Coffee husk ash (CHA) is a solid waste obtained by the processing of coffee beans on a farm or factory. The main aim of this study is to determine the geotechnical properties of clay soil treated with CHA to develop a low-cost, environmentally friendly alternative composition. Laboratory tests were conducted to investigate the influence of CHA on the physical properties and the mechanical properties of clay. The CHA concentration was adjusted from 5% to 25% by the dry weight of clay in 5% increments. The clay classification of the mixture becomes coarser following the addition of the CHA. At 25% CHA, a peak UCS of 130.83 kN/m2 was measured compared with the untreated clay of 89.17 kN/m2. In addition, the cohesion values and internal friction angles of soil for 0% and 25% CHA increased from 80.1 kN/m2 to 148.7 kN/m2 and from 16.1° to 25.8°, respectively. It was found that CHA can improve the strength of clay by forming a pozzolanic and hydration process that fills soil voids and binds particles together.

Mechanical Properties of Clayey Soil Reinforced with PET Considering the Influence of Lime-Stabilization

Reusing waste plastic can be considered as an important issue in terms of economical as well as environmental concerns. Stabilization of clayey soil is a well-utilized approach to improve the mechanical properties concerning the geotechnical aspects. Meanwhile, the effect of concurrent employment of both lime and waste plastic fibers with different contents and various shapes on mechanical properties of clay is not evident. This research presents the mechanical characteristics of clayey soil reinforced with Plastic Polyethylene Terephthalate (PET). Both unstabilized and lime-stabilized clay are considered as unreinforced materials and the plastic strips and pellets are separately utilized as reinforcement substances. Various tests namely standard Proctor compaction test, point load test (PLT) and drop-weight impact loading test are performed to assess the effect of reinforcement and stabilization on mechanical behavior of clayey soil. The concurrent influences of using PET and adding lime confirm that positive effect of lime stabilization on strength is more meaningful. Meanwhile, the limited content of 1.5% of PET shows the maximum strength for reinforced clayey soil. Generally, reinforcement with strips leads to the exhibition of higher strength based on the point load strength index and more flexibility based on the applied impact loads in comparison with pellet particles.

Peningkatan Daya Dukung Tanah Lunak dengan Menggunakan Tanah Campuran Well Graded

Soft clay is often a problem in the implementation of highway construction because clay has great development potential and low carrying capacity. This research was conducted by stabilizing soft clay soil with a mixture of well graded soil. Soft clay samples were taken from Punggur and well graded soils were taken from Kampung Tua Belian. The study used a mixture of 20%, 30%, 40%, and 50% well graded soil stabilization materials and an immersion period of 4 days. This research covers the physical and mechanical properties of clay in terms of optimum moisture content, laboratory CBR, and free compression test (UCT). The data obtained from research activities were analyzed descriptively in the form of tables and graphs of relationships. The results showed that the soft clay from Punggur had a specific gravity of 2,497 with the addition of well graded soil composition up to 50%, the liquid limit decreased to 67.75%, the plastic limit decreased to 37.69%, and the plasticity index decreased to 30.07%. . The addition of well graded soil composition up to 50% changed the Unified system, the soil type changed from the OH group to SC-SM, while according to the AASHTO system, the soil type did not change. The value of laboratory CBR and free compression test (UCT) increased along with the increase in the composition of the well graded soil.

Secondary development of a thermo-elastoplastic constitutive model for saturated clay in ABAQUS

Some projects, such as application of energy piles, underground storage of nuclear waste, geothermal development and laying of heat pipes, are necessary to consider the effect of temperature on the mechanical properties of clay. Test results have shown that clay may show two different phenomena: the shear strength of soil increases (thermal hardening) or decreases (thermal softening) with an increase in temperature. In order to describe these two different thermo-mechanical behaviors of clay, a new thermal elastoplastic constitutive model of saturated clay, in which the influence of temperature on pre-consolidation pressure and critical state parameter M of clay are taken into considerations, is proposed based on sub-loading modified Cam-clay model. The secondary development of the new model on ABAQUS was completed by preparation of the UMAT material subroutine. Through comparing the theoretical results with test results, it is known that the proposed constitutive model is capable of describing the thermal hardening and thermal softening behavior of clay well. And the correctness of the proposed constitutive model was verified. Finally, based on the proposed model, the generating mechanism of the thermal hardening and thermal softening behavior of clay are discussed macroscopically in terms of the influence degree of temperature on pre-consolidation pressure and critical state parameters.

Strength and consolidation properties of clay modified by nano bentonite

Nano bentonite is a new kind of soil modification material, which can effectively improve the physical and mechanical properties of clay. The development of new soil modification technology has been a research hotspot in geological engineering, geotechnical engineering and road engineering. The purpose of this study is to test and analyze the strength and consolidation characteristics of clay modified by nano bentonite, and to explore the new clay materials applied in modern geological engineering. In this study, an installation test was carried out on the preparation of nano bentonite, and the compressive condition of the bentonite was observed. After that, the viscosity strength of nano bentonite was compared with that of undisturbed soil by the control variable method, and the nano bentonite was divided into experimental group and control group. The viscosity strength and consolidation characteristics of nano bentonite were observed and analyzed by changing temperature, nano bentonite content, pressure and pore ratio. The results show that the consolidation coefficient of the sample without adding nano bentonite is 8.7 × 10–3 cm2/s, which is 6.6 × 10–3 cm2/s lower than that of 2% nano bentonite. It shows that the consolidation coefficient decreases with the increase of consolidation pressure and the decrease of void ratio. The nano bentonite modified clay is also more stable in road or building construction. The method of this study has brought a certain value for the research of nano materials in soil materials.

Influence of Organic Matter Content on Engineering Properties of Clays

Most natural sedimentary clay contains organic matter, and even a small amount of organic matter will have a great impact on the physical and mechanical properties of clay. In order to clarify the influence of organic matter content on clay soil, the illite-quartz mixture was mixed with natural amorphous peat soil (organic matter content is 50%) in different proportions for studying the influence of different organic matter contents on the physical properties (specific gravity, Gs; moisture content, w ; void ratio, e; liquid limit, w L ; plastic limit, w p ; plasticity index, Ip) and shear characteristics (cohesion, c; friction angle, φ) of clay soil. The experimental results found that, with the change of organic matter content, the specific gravity and void ratio of clay changed linearly, while the water content, Atterberg limit, shear strength, cohesion, and friction angle changed nonlinearly with the increase of organic matter content. Moisture content and Atterberg limit have a turning point when OC = 7.5%. Shear strength, cohesion, and friction angle all have obvious turning points when OC = 7.5% and OC = 37.5%. The variation of moisture content and Atterberg limit with organic matter content indicates that OC = 7.5% may be the limit value for the different forms of organic matter in the clay. When OC ≤ 7.5%, the organic matter in clay is in the bound state; when OC > 7.5%, the bound organic matter reaches saturation; and the free organic matter gradually increases. The change law of shear strength characteristics with organic matter content shows that the interaction between minerals and organic matter exhibits different shear characteristics under different organic matter content. When OC ≤ 7.5%, clay shows mineral properties, when 7.5% < OC ≤ 37.5%, clay shows mineral-free organic matter properties, and when OC > 37.5%, clay shows free organic matter properties.

CARACTERIZAÇÃO MICROESTRUTURAL E PROPRIEDADES FÍSICAS E MECÂNICAS DE ARGILAS DA REGIÃO NORTE DO ESPÍRITO SANTO

O objetivo deste trabalho foi determinar as propriedades mineralógicas, físicas e mecânicas de argilas do norte do Espírito Santo. Foram analisadas duas argilas na forma como recebido (amostras A e B) e dois traços (2A-5B – amostra C; e 3A-4B – amostra D) utilizadas para confecção de tijolos. Para caracterização mineralógica utilizou-se as técnicas de fluorescência de raios X, microscopia eletrônica de varredura, difração de raios X, distribuição granulométrica, análises térmica diferencial e termogravimétrica e limites de Atterberg. Avaliou-se também absorção de água, porosidade aparente, massa específica aparente, retração linear após queima e limite de resistência à compressão de corpos de prova com 12 mm de diâmetro por 24 mm de altura, confeccionados por prensagem uniaxial, secados a 110°C por 24 h e sinterizados a 850°C, 900°C e 950°C, a 5°C/min com permanência por 2h nessas temperaturas. Os resultados das propriedades mineralógicas das amostras A e B apresentaram-se de acordo com a literatura. Os resultados das propriedades físicas e mecânicas apontaram para a utilização da amostra D como matéria prima para fabricação de tijolos.

Study on the Mechanical Properties of Clay- Fly Ash Mixture

Study on the Mechanical Properties of Clay- Fly Ash Mixture

Mechanical behavior of micaceous clays

This study aims to investigate the effect of mica content on the mechanical properties of clays. Commercially available ground mica was blended with a locally available clayey soil, at varying mica contents by mass of 5%, 10%, 15%, 20%, 25% and 30%, to artificially prepare various micaceous clay blends. The preliminary testing phase included consistency limits and standard Proctor compaction tests. The primary testing program consisted of unconfined compression (UC), direct shear (DS) and scanning electron microscopy (SEM) tests. The test results showed that the liquid and plastic limits exhibited a linear, monotonically increasing trend with increase in mica content. The rate of increase in the plastic limit, however, was found to be greater than that of the liquid limit, thereby leading to a gradual transition towards a non-plastic, cohesionless character. The soft, spongy fabric and high water demand of the mica mineral led to higher optimum water contents and lower maximum dry unit weights with increasing mica content. Under low confinement conditions, i.e. the UC test and the DS test at low normal stresses, the shear strength was adversely affected by mica. However, the closer packing of the clay and mica components in the matrix under high confinement conditions offsets the adverse effects of mica by inducing frictional resistance at the shearing interface, thus leading to improved strength resistance.

Correlation analyses of effects of temperature on physical and mechanical properties of clay

In determining the physical and mechanical parameters of clay, it is sometimes necessary to determine them indirectly from other parameters since they cannot be measured directly from laboratory or field tests. In order to determine the effect of temperature on the behavior of clay, an indirect approach is used here by analyzing the changes of mass ( $$\Delta m$$ ), density ( $$\rho$$ ), porosity ( $$\phi$$ ), P-wave velocity ( $${v_p}$$ ), thermal conductivity ( $$\lambda$$ ), specific heat capacity (c), resistivity (R) and uniaxial compressive strength (f) of clay from eastern China for a temperature range between 20 and 800 °C. The results indicate that temperature has a significant effect on these parameters. Comparisons between $$\Delta m$$ and $$\rho$$ , $$\Delta m$$ and $${v_p}$$ , $$\rho$$ and $${v_p}$$ , $$\phi$$ and $$\lambda$$ , $${v_p}$$ and f, R and f show a linear change among these parameters,whereas the relationships among $$\Delta m$$ and $$\phi$$ , $$\phi$$ and $${v_p}$$ , $$\phi$$ and R, $${v_p}$$ and $$\lambda$$ , $$\phi$$ and f are exponential. It is difficult to obtain these relationships by using regression analysis with high levels of accuracy. Further refinement is therefore required.

Some observations considering undrained shear strength, liquidity index, and fluid/solid ratio of mono-mineralic clays with water–ethanol mixtures

The mechanical properties of clays are influenced by the characteristics of the fluid in the pore space. The liquid limit reacts differently to the permittivity, ε, of the fluid: for smectites the slopes are positive, for kaolinite and illite they are negative and smaller. This dissimilarity can be explained by the structural differences between swelling smectites with solvated interlayer cations and nonswelling clay minerals such as kaolinite and illite. Undrained shear strengths, cu, of Ca–smectite, but not Na–smectite, correlate with the actual fluid ratio. Regressing cu against the liquidity index, IL, yields two different regression lines for Na–smectite and Ca–smectite. For the first time it is shown that normalizing cu to the ε of the pore fluid results in a single regression line for both smectitic clay types. As kaolinites and illites possess significantly less exchangeable cations than smectites, this yields significantly smaller ranges for Atterberg limits and reduces the impact of ε on almost pure particle–particle interactions. In addition, the much larger particle sizes of the kaolinite and illite may dominate the undrained shear strengths, as normalization of cu to ε did not change the relationship to either the actual water content or the liquidity index.

The Preparation and Properties of Clay Bonded Silicon Carbide by Using Silicon Carbide Dusting Powder

In this paper, clay bonded silicon carbide was prepared through pressureless sintering process with silicon carbide dusting powder as raw materials and clay as sintering additive. The effects of the ball-milling method, sintering temperature and clay contents on the density, microstructure and mechanical properties of clay bonded silicon carbide refractory were studied. The planetary ball-milling was a good method to improve the density of the green body, and the density was increased simultaneously with an increase of the clay content. The liquid phase derived from low-melting eutectic mixtures of clay could prevent the superlative oxidation of silicon carbide. The mass increment of sintered samples decreased firstly and then increased at the sintering temperature range from 1250 to 1500 °C. The open porosity of samples decreased with the clay addition at a content range from 10 to 30 wt.%. The bending strength of the samples decreased firstly and then increased with the clay addition increasing. The optimum condition for preparing clay bonded silicon carbide with silicon carbide dusting powder was sintering at 1350 °C with 20 wt.% clay, and the obtained sample with a porosity of 24% achieved the bending strength of 78±7 MPa.