Clay Water Content Research Articles

Insight into the Effect of Fine Content on Liquefaction Behavior of Soil

The present paper presents different approaches which includes plasticity based criteria that helps in distinguish between liquefiable and non-liquefiable soils deposits having fine content. A brief review of the previous work has been mentioned to emphasise on the need of new parameters for liquefaction susceptibility of clayey soils. Clay content, liquid limit and water content are considered as key parameters that helps in liquefaction assessment. Several recommendations proposed by prominent researchers are described here to present wide range of plasticity index, liquid limit and other parameters that affects liquefaction behaviour of clayey soil significantly. But the differences in the range of plasticity index leads to confusion and misperception in determination of liquefaction susceptibility of fine grained soil. One of the high seismic zone site is analyzed using different approach which consider fine content of soil mass. It is found that for a better and proper segregation of the layers Bray and Sancio criteria may be adopted which uses plasticity as one of its input parameter and clearly differentiate site in between liquefiable, non-liquefiable and sites that may liquefy i.e. moderately liquefiable. This summarizes that plasticity is one of the significant criteria which draws a clear differentiating line between liquefiable and non-liquefiable soil deposits.

The influence of organic matter on the strength development of cement-stabilized marine soft clay

The organic matter within clay soil is one of the important factors affecting its engineering characteristics. In this study, the influence of organic matter on the strength evolution of cement-stabilized marine soft clay is evaluated by scanning electron microscopy (SEM) and unconfined compressive strength (UCS) testing. The experimental results show that the after-curing clay water content of the specimens increased with the organic matter content. However, the after-curing unit weight decreased with the organic matter content. The strength decreased with the increase in the amount of organic matter. The strength loss (SL) increased with the organic matter content. A new mathematical model was determined and then used to quantitatively analyze the strength of the investigated samples. A relationship between the strength and organic matter content was established. The evaluation of the accuracy of this new strength model was carried out by comparing the predicted values and measured values, and the results indicated that the deviation was mostly within 10%. Finally, the microscopic changes of the sample surface and influencing mechanism of the organic matter were revealed through SEM. A high soil strength is mainly due to a relatively low porosity, a dense microstructure and the formation of hydration products.

Electrical properties of frozen saline clay and their relationship with unfrozen water content

The unfrozen water content has a significant impact on the mechanical and thermal properties of saline soils during freezing, and their electrical properties measured by electromagnetic sensors can be a promising proxy of the unfrozen water content. This paper investigated the electrical properties and their relationship with the unfrozen water content of saline lean clay. Specimens with increasing concentration of sodium chloride were prepared for assessing their initial freezing points and unfrozen water content by the cooling test and the nuclear magnetic resonance relaxometry, respectively. In addition, the apparent dielectric permittivity and bulk electrical conductivity were measured by sensors based on frequency-domain reflectometry in the electrical property test. A significant variation was observed in both the apparent dielectric permittivity and bulk electrical conductivity of saline lean clay near the initial freezing point. They generally decreased linearly with decreasing temperatures above their initial freezing points and then dropped according to a power curve with temperatures below their initial freezing points. The bulk electrical conductivity of saline lean clay depended on salt concentration and ion conductive pathway, with the latter being dominant at temperatures below its initial freezing point. A new empirical equation was proposed for estimating unfrozen water content based on the apparent dielectric permittivity and initial salt concentration, and independent data validated its applicability of similar soils at relatively low salt concentrations. The proposed equation could be useful for the evaluation of the unfrozen water content of saline lean clay via the apparent dielectric permittivity and initial salt concentration.

Effect of land terracing on soil physical properties across slope positions and profile depths in medium and high altitude regions of Rwanda

Although land terracing is promoted as a management practice for effective soil conservation in hilly areas, construction of terraces causes changes in soil properties. This study evaluated the effect of land terracing on some soil physical properties across slope positions and profile depths in medium and high altitudes of eastern and north-eastern Rwanda. Soil samples were collected from top, middle and bottom slopes of four year-old terraced and non-terraced lands. Results showed that soil textures were mainly sandy clay loams. At medium altitude, silt (19.6, 18.6%) and hydraulic conductivity (237.9, 129.8 mm h−1) were significantly ( p < 0.05) higher in terraced than non-terraced land, while clay (29.2, 27.8%) and total available water content (TAWC) (222.2, 201.7 mm m−1) were higher in non-terraced than terraced land. At the high altitude, hydraulic conductivity (194.3, 124.1 mm h−1) was higher in terraced than non-terraced land, while soil bulk density (1.42, 1.35 g cm−3) and TAWC (251.6, 235.3 mm m−1) were higher in non-terraced than terraced land. Terracing increased silt content and hydraulic conductivity, and slightly decreased clay and water retention capacity. These changes are important in soil water and fertility management, and therefore need to be considered when using terraced lands.

Variation in Shearing Rate Effect on Residual Strength of Slip Zone Soils Due to Test Conditions

Shearing rate effect on the residual strength of slip zone soils is considerable for sliding or reactivated landslides. It is complicated and variably affected by external inducing factors, and its variation has not attracted much attention. Using drained ring shear tests on the slip zone soils from two selected landslides with the shearing rates of 0.1–20 mm/min, this study investigated the variation in the shearing rate effect on the residual strength under the influences of the clay fraction, water content, and normal stress. In addition, the shear zone structures were analysed using microscopic observations. The results show that the residual strength decreases with increasing shearing rate (i.e., negative rate effect) and exists a good linear relationship with the logarithmic shearing rates. The slope of the fitting lines of the residual stress ratios versus shearing rates is proposed to assess the shearing rate effects. Furthermore, the effect is significantly affected by the clay fraction, water content, and normal stress. The samples with the low clay fraction exhibit a more significant negative rate effect, and the effect weakens with decreasing water content and normal stress, which are associated with the variations in the shear zone structures due to particle breakage. Additionally, increasing shearing rates and shear displacement change the shear zone structures and thus induce a negative rate effect on the residual strength of the soils.

Field study on performance of jet grouting in low water content clay

One drawback to the application of jet grouting for soil improvement is quality control, especially the determination of the diameter and strength of the column, which depends on the technical specifications of the injection and soil type. It has been reported that the initial water content of the clay effects the erosion of cohesive particles. The compressive strength and diameter of a soilcrete column in clay/sand at different jet grouting specifications have been well documented. However, the effect of the initial water content of clay on the performance of the jet grouting method has not been reported. Researchers have not proposed technical specifications for single-fluid jet grouting in remoulded clay with a low water content. The present study carried out 10 full-scale tests to analyse the effect of single-jet grouting specifications on the diameter and uniaxial compressive strength of soil-cement columns in a reclaimed area with low water content clay. The clay-jet grout interaction was evaluated using a microstructural approach and revealed that there is insufficient cohesion between the particles of remoulded clay. The mechanisms of interaction between the particles and the jet grouting is a combination of erosion and penetration of the grout into the soil and into air-filled cracks. In this case, it caused the particles to behave in a manner that is similar to that of silt and sandy soil. The efficiency of jet grouting in this type of soil was better than in clayey soil with a high water content. Thus, the equation previously used to estimate the diameter of the column has been modified by increasing the reference diameter from 50 to 60cm for clayey soil with a low water content. The results show that an increase in the time interval and decrease in lifting step reduced the number of clayey clods in the core and increased the strength of the soil-cement. The maximum strength and diameter were achieved at an energy of 25MJ/m with an optimum injection pressure of 45MPa for single-fluid.

INFLUENCE OF CLAY CONTENTS ON DRAINED SHEAR STRENGTH PARAMETERS OF RESIDUAL SOIL FOR SLOPE STABILITY EVALUATION

Consolidated drained triaxial compression tests (CD) were conducted to determine the compression properties of remolded samples collected from hillslope in residual soil. The test results showed that the effective drained shear strength of residual soil was primarily affected by the degree of weathering according to depth, parent rock material, and clay contents and also influenced by initial moisture content. These samples were classified as silt soils of high to low plasticity. CD tests were performed on samples prepared under 100 and 200 kPa remolding pressure with three different confining pressures of about 50, 100 and 150 kPa. Predicted results showed that the soil strength increased with increasing samples’ density for those who prepared with a higher remolding pressure. According to the soil composition, a clear decrease in soil cohesion was observed for samples collected at a deeper depth, while a further increase in the effective internal friction angle was observed for samples collected with a lower depth. However, this explains the significant influence of clay contents that can be represented as a relevant relation. Therefore, the results indicated that the studied residual soils have physical and geotechnical properties that are highly dependent on the clay and initial water contents. Then, the concept of long-term stability analysis of hillslope of Balai Cerap area (in UTM/ Malaysia) was presented in the form of factors of safety as discussed later in this study by employing Geo-Studio program (SLOPE/W application) with Limit Equilibrium Method.

Mechanism, Stability and Remediation of a Large Scale External Waste Dump in China

This paper presents a study of the failure mechanism and control measures for a landslide at Dagushan Waste Dump. In addition to a summary of the site geological conditions, the observed landslide shape is described based on site investigations. It is shown that the dominant causes of the slope stability problem are softened silty clay due to rainfalls and the mechanical vibrations of a concrete batching plant at the slope toe. Failure mechanism analyses were performed by base friction test, which showed that the failure mode of Dagushan Waste Dump is a collapse-traction-push type landslide. Dump stability analyses were performed using the limit equilibrium method, which showed that safety factors of the waste dump decrease with the increase of water content of silty clay, and with the increase of average vibration acceleration of mechanical vibrations. The water content of silty clay has a much greater influence on dump stability than the average vibration acceleration. Remedial measures to stabilize the unstable zones include slope reshaping, platform compacting, drainage system ameliorating, and cracks filling. The results indicate that these measures are effective in controlling the landslide.

Experimental Study on Shear Properties of Interface between Clay and Cement Paste

According to the typical clay in Changzhou, the shear properties of interface between cement paste and clay were studied through changing water content of clay and water cement ratio of cement paste. Rules of shear strength, internal friction angle and cohesion of contact surface between cement paste and clay changing with water content were researched. The results show that when the water cement ratio and clay moisture content remain unchanged, the shear stress increases with the increase of normal stress. After reaching a peak value, the shear stress begins to decrease. When water cement ratio and normal stress remain unchanged, the shear stress decreases with the increase of water content. When the water cement ratio is constant, the internal friction angle decreases with the increase of water content. When the water cement ratio is 0.4 and 0.45, the cohesion decreases with the increase of water content. When the water cement ratio is above 0.5, the cohesion increases first and then decreases with the water content. 17% is the optimum moisture content, at this time, the cohesion is the greatest.

Water-sensitive Properties of Shear Strength of Bijie Red Clay under Direct shear Testing

In order to study the water-sensitive properties of Bijie red clay, the basic physical index test and direct shear test of different water content samples were carried out. The relation between shear strength index and water content of red clay was obtained, and the influence of critical water content on strength was analyzed. The testing results show that the shear strength index of Bijie red clay turns around the natural moisture content, because of the cracks generated with water losing. Then the functional relationship between cohesive force, internal friction angle and water content was established. Based on this relationship, it can reflect the quantitative influence of water content on intensity.

Stress Effects on Soil Freezing Characteristic Curve: Equipment Development and Experimental Results

Core IdeasA triaxial apparatus is developed to measure stress‐dependent SFCC.Unfrozen water content of clay and sand increases with increasing confining stress.Stress effects on the SFCC of clay are more significant than sand.The soil freezing characteristic curve (SFCC) defines the relationship between soil temperature and unfrozen water content. This curve is important for predicting water flow and heat conduction in frozen soils, as well as freezing heave and thawing settlement. So far, SFCCs reported in the literature were usually determined at zero stress. To investigate stress effects on SFCC, a stress‐ and temperature‐controlled triaxial apparatus was developed in this study. The unfrozen volumetric water content was measured using a newly developed noninvasive time domain reflectometry (TDR) probe. The new apparatus was used to measure SFCCs of two typical soils (i.e., clay and sand) at different stress conditions (i.e., 30, 100, and 200 kPa). Each specimen was subjected to compression, and then a cycle of freezing and thawing. As expected, for both soils, the saturated water content prior to freezing was smaller at higher stresses because of compression. During the subsequent freezing and thawing, the soil specimen at a higher stress was able to retain more liquid water than that at a lower stress. The higher unfrozen water retention capacity at higher stresses is mainly because the pore size of a soil specimen becomes smaller during compression. Hence, more water can retain a liquid state due to the enhanced capillarity. On the other hand, stress effects on the SFCC were found to be more significant for clay than for sand. This is likely because the stress‐induced change in pore size distribution is larger in clay due to its higher compressibility.

The effect of clay water content in the Jet Erosion Test

The understanding of the onset of breaching induced by surface erosion is fundamental to enable definition of the level of protection afforded by embankments and provision of standards for the design of new structures and the upgrading of existing ones. Compacted embankment materials are generally partially saturated due to seasonal variation in the water content. At the onset of the overflow process embankments undergo to a wetting process due to the changes at the outer surface boundary conditions (i.e. overflow). Erosion behaviour is known to be a counterbalance between gravity forces and shear erosion forces. However, as the particle size decreases (i.e. clayey soils), gravitational forces become negligible and electrochemical interaction between particles play a dominant role. Clay microstructure (e.g. particle configuration and inter-particle forces) changes with the hydro-mechanical stresses history. Thus, it is necessary to consider the microstructural changes in particle configuration to understand the influence of microstructure on the macroscopic behaviour of clay during erosion. Upon wetting, clay have a swelling/collapse behaviour. This research presents experimental results on erosion of clay samples compacted at the same initial dry density but with different compaction water content. The influence of different wetting times on erosion is also investigated. We show that for a given as-compacted water content, the longer the wetting stage, and hence the higher the sample water content, the more erodible the samples. Additionally, for samples compacted at the same dry density, the ones compacted on the dry side of optimum are more erodible than samples compacted at the optimum water content, despite the lower water content at formation. We hypothesise that this may be due to the formation of a different initial microstructure in sample on the dry side of optimum (i.e. bi-modal pore size distribution). Our results contribute to the fundamental understanding of time-dependent mechanisms that influence erosion of clay embankments during overflow and, hence, to embankment failure. In addition, these tests show how basic concepts of unsaturated soil mechanics can serve as a guide to ‘design’ the compaction conditions of embankment material.

Effects of clay properties in the landslides genesis in flysch massif: Case study of Aïn Draham, North Western Tunisia

Heavy rainfall in Aïn Draham province in the North-Western of Tunisia lead to the formation of some landslides which could poses danger to lives and properties. The geological outcrops of the region mainly consist of Numidian flysch rocks. In this study, field based 15 undisturbed samples were taken, from 11 boreholes drilled in 4 landslide points, to understand the real behaviour of soils when landslides occur. For this purpose, the geotechnical characterization of all samples was carried out. The grain size distribution shows that the clay and silt fractions prevail. The clay fraction ranges between 4% and 64% with an average of 40.4%, the silt fraction ranging from 19% to 71% averaging 39.8% and the sand fraction was between 6% and 44% with an average of 19.8%. The Casagrande plasticity chart indicates that 33.3% of samples were in the high plasticity group (CH group) and 66.6% having a medium to low plasticity. The water content varies between 12% and 31%. The direct shear strength test shows that the cohesions values range from 41 KPa to 77 KPa and the internal friction angle values range widely from 12° to 27°. A statistical approach was taken to determine the most important factors responsible for the decrease of the cohesion and friction angle which are in charge of slope failure. For this, a correlation matrix of all soil properties was done. The coefficients of correlation show that the clay fraction is the most correlated parameter to the cohesion with an index of −0.872. Unfortunately, the internal friction angle is very low correlated to all geotechnical parameters. The clay fraction, as the most correlated to the cohesion, and the water content, which depends on rainfall (landslide triggering factor), were considered as two independent parameters for the establishment of a multiple linear and non-linear regression models of the cohesion. The multiple linear model showed that the cohesion decrease with the increase of water content and especially the increase of clay fraction with coefficients of −0.083 and −0.441, respectively. The non linear model showed that the cohesion decrease exponentially and linearly with the increase of the clay fraction and water content, respectively. The statistical study of the effect of geotechnical parameters on the landslide triggering, shows that the clay formations and also the increases of soils clay fraction by alteration phenomena is the crucial factor in landslides genesis. During rainfall the increase of the water content of clayey soils decreases the shear strength of soils more and more.

Molecular insight into competitive adsorption of methane and carbon dioxide in montmorillonite: Effect of clay structure and water content

The microscopic competitive adsorption mechanism of methane (CH4) and carbon dioxide (CO2) is of fundamental significance for CO2 sequestration with enhanced gas recovery (CS-EGR) in clay-rich shale gas reservoirs, which is still in a preliminary research stage. In this study, the Na-montmorillonite models with various pore sizes and water densities were generated to gain insights into the CO2/CH4 competitive adsorption behaviors using the combined molecular dynamics and grand canonical Monte Carlo simulations. The effects and corresponding mechanisms of clay pore size, structure heterogeneity and water content on CO2/CH4 adsorption capacity, contribution of selectivity and isosteric adsorption heat were discussed in detail. Simulation results show that the Na-montmorillonite clay favors the preferential adsorption of CO2 over CH4, and the preferential adsorption of CO2 reduces with increasing clay pore size and pressure. Adsorbility factor is the major contribution for the CO2/CH4 adsorption selectivity in dry clay models, while the contribution of volumetric factor enhances with rising pore heterogeneity caused by increasing water content and decreasing pore size. The physical pore heterogeneity in the upper near-wall region resulted from Na+ distribution, associated with the difference of CO2/CH4 dynamic diameter is one reason for the asymmetrical CO2/CH4 density profiles, while the strong affinity between CO2/Na+ and substituted Al atoms in the upper tetrahedron is the other reason. Interestingly, a later increase of CO2/CH4 adsorption selectivity with further rising water density is observed, which is due to the solvation of Na+ in interlayer water phase, re-exposing some high energy adsorption sites for CO2 adsorption. This result provides implication that the CS-EGR efficiency can be potentially improved by increasing the water content in clay. This study gains deep insights into the CO2/CH4 competitive adsorption mechanism in montmorillonite clay at microscopic scale, and can open new potentials for tuning the application of CS-EGR in clay-rich shale gas reservoirs.

Experimental Analysis of the Influence of Soil Composition on Strength Characteristics

This study investigates the influence of soil composition on soil strength by performing direct shear test on various samples, including artificial soil with different components, artificial mixed soil with different amounts, natural soil with different moisture contents, and sandy soil with different sizes. The test results show that soil strength is determined by the joint effect of inter-particle friction and cohesion. Mineral composition and water content are the main factors affecting clay strength. Changes in the mineral composition and water content of clay alter the contact state and connection of its particles, thereby significantly affecting the macroscopic properties of the soil. Different grain compositions modified the shear deformation characteristics by altering the arrangement and intergranular engagement of the particles, consequently affecting the strength. The results of this study provide further insight into the micro and fine mechanism of the soil shear strength characteristics of different components. This study also offers guiding significance in engineering practice.

Effect of clay fraction and water content on rheological properties of sand–clay mixtures

Debris flow mobility can be expressed through rheological properties including yield stress and viscosity. These rheological properties are major parameters to describe and predict behaviors of debris flow. In the present study, the effect of clay fraction and water content on the rheological properties of sand–clay mixtures with coarse grain particles was investigated using a large vane rheometer. All soil mixtures showed non-Newtonian fluid behavior. When clay content was in the range of 5–30%, yield stress increased with an increase of clay fraction. Yield stress and plastic viscosity exponentially decreased with an increase in water content. Plastic viscosity became more sensitive to the change in clay fraction when water content increased. Empirical equations were proposed to estimate rheological properties of soil. The results indicated that yield stress and plastic viscosity are more sensitive to changes in water content than changes in clay fraction.

A method for calculating unfrozen water content of silty clay with consideration of freezing point

Abstract A physical calculation model for the content of unfrozen water of silty clay was proposed with a consideration of freezing point. The freezing point of bulk water, capillary water and bound water was calculated. The freezing point of bulk water was assumed to be constant in the calculation. The Kelvin equation and the theory of water activity were used to calculate the freezing-point changes of the capillary and bound water during the volume decrease, respectively. The influence of soil-particle size on the freezing point was taken into account in the model. In the calculation, the unfrozen water content at a negative temperature was defined as the sum of the volume of capillary and bound water whose freezing point was lower than the given temperature. By using silty clay from the Qinghai-Tibet Plateau as an example, the results of the model calculations were validated by using the measured data from time-domain reflection and nuclear magnetic resonance. The calculations for four existing models as proposed by other scholars were listed for comparison with our model. The results show that the calculated results of our model are precise and reflect the hysteresis effect of the unfrozen water content during freezing and thawing. The model validated an order of freezing in soil: bulk water froze first, most capillary water froze next, and most bound water froze last. This paper explains the existence of unfrozen water from the perspective of freezing-point change and provides a theoretical basis for the calculation.

Failure mode and dynamic response of a double-sided slope with high water content of soil

A double-sided slope with high water content in sandy clay was considered under the action of seismic load. Its failure mode and dynamic response were investigated using a hydraulic servo shaking table test. The typical characteristic of failure mode and dynamic responses of the double-sided slope were analyzed. Experimental results show that slope failure undergoes a process of progressive deformation. The slope failure mode can be explained as creep sliding landslide. AFA (Amplification Factor of Acceleration) at the surface and inner parts of the slope shows an increasing trend with the increase of relative elevation. The relationship between AFA and EAA (Excitation Amplitude of Acceleration) is nonlinear. An empirical formula is proposed to describe preferably the relationship between AFA, relative elevation and dimensionless EAA. The AFA at the middle and upper parts of the slope increases apparently with increasing EFA (Excitation Frequency of Acceleration).

Identifying the Impact Factors of the Dynamic Strength of Mudded Intercalations during Cyclic Loading

Despite reports on previous research associated with the dynamic strength of mudded intercalations during cyclic loading, a systematic investigation of the impact factors of this strength is still valuable. This work aimed at experimentally revealing the impact factors of the strength along with their impacts. The potential impact factors considered in this work include (i) water content, (ii) clay mineral composition, (iii) clay content, (iv) confining pressure, and (v) cyclic failure time. Specimens of mudded intercalations were collected from China and were remolded and prepared for a dynamic triaxial test under cyclic loads. The test results showed that the dynamic strength is impacted by water content (strongly), clay mineral composition (moderately), confining pressure (moderately), and cyclic failure time (weakly); no significant impact of clay content was detected. Moreover, the dynamic cohesion is correlated with clay mineral composition (strongly), water content (moderately), and cyclic failure time (weakly); no significant correlation with clay content or confining pressure was detected. Finally, the dynamic friction angle is correlated with water content (strongly), clay content (moderately), and cyclic failure time (weakly); no significant correlation with clay mineral composition or confining pressure was detected.

Vertical distribution of soil organic and inorganic carbon under different vegetation covers in two toposequences of the Liudaogou watershed on the Loess Plateau, China

Understanding the carbon (C) cycle of the terrestrial ecosystem and estimating the C sequestration potential in soils are critical to evaluate ecosystem function and security. The vertical distribution of soil organic carbon (SOC) and inorganic carbon (SIC) as well as their influencing factors under different types of vegetation in two toposequences of the Liudaogou watershed on the Loess Plateau of China were investigated. Results showed that the measured soil properties were differentiated into two groups: (1) one behaving relatively conservatively (pH, bulk density, silt content, and capillary and total porosity) with coefficient of variations (CVs) &lt; 10% and (2) the other encompassing more labile components (SOC, SIC, noncapillary porosity, clay, and sand and soil water content) with CVs &gt; 10%. Soil organic C under different vegetation covers in the two toposequences (0.62 to 5.12 g kg⁻¹) decreased rapidly with depth in the top 0 to 50 cm soil layer and then remained relatively stable over the 50 to 200 cm depth, which can be described by the exponential model. In contrast, SIC (4.11 to 18.69 g kg⁻¹) was much higher than SOC and showed distinct distribution patterns, which increased initially with depth and then decreased downwards except for the grassland in the west-facing slope (W-grassland) exhibiting an opposite trend. There were no significant differences of SOC either under different vegetation covers or in different slopes over the whole profile (<i>p</i> &gt; 0.05); however, significant differences of SIC were observed for both different vegetation covers in the same slope and for the same vegetation cover in different slopes (e.g., W-grassland versus W-forestland, W-grassland versus NE-grassland) (<i>p</i> &lt; 0.05). This study demonstrated that different soil properties could simultaneously affect SOC and SIC contents; thus attempts to model SOC and SIC based on the independent effects of individual soil property without consideration of their interactions would result in unsatisfactory prediction. We proposed models that quantitatively described SOC and SIC contents as a combined product of different soil properties for each vegetation cover in both northeast-facing and west-facing slopes using multiple regression analysis, which could improve the prediction of SOC and SIC contents for the study area from the simple linear regression models.