Influence Of Clay Content Research Articles

Development of an initial normal-loading direct shear tester of discontinuities, with subsequent passive changes in local normal load/stiffness allowable, and an investigation of the shear behaviours of discontinuities

A widespread case of discontinuity shearing is found among local shallow rock blocks sliding along non-planer, rough, non-anchored discontinuities, which is characterized by an initial normal load in addition to free subsequent changes in local normal load/stiffness, provoked by shear dilatancy (INL). The existing direct shear apparatuses of rock discontinuities fitted for those cases are rare, and there is a lack of understanding of the shear behaviours of discontinuities under such INL boundary conditions. Here, we develop an INL direct shear tester of discontinuities for shear strength. This tester takes advantage of the direct shear test apparatus modified after the YZ-5 model without a servo-controlled system to permit the accomplishment of those boundary conditions. Shear behaviours of unfilled and infilled discontinuities under INL boundary conditions are investigated. Moreover, the possible influence of clay content on those shear behaviours of infilled discontinuities is clarified. The developed tester made it possible to test the shear performance of the local shallow rock blocks sliding along non-planer, rough, non-anchored discontinuities. This work contributes to a limited body of research on the shear behaviours of discontinuities under those INL boundary conditions. Limitations of this work are also revealed.

Influence of clay content on repeated liquefaction resistance of sand using element test

Soil liquefaction is a major concern because of its potential to cause building collapse, roadbed settlement, and sand eruptions. Field investigations have shown that clayey sand, when liquefied during mainshock, may undergo multiple liquefaction events during the subsequent aftershocks. Although previous research has primarily focused on the initial liquefaction event in clayey sand, research on the mechanism responsible for repeated liquefaction is limited. Consequently, a series of cyclic triaxial experiments are conducted on sand with varying clay contents, and these samples are subjected to various earthquake sequences. The primary objective of this study is to evaluate the cyclic behavior of sandy soil with clay content and analyze its repeated liquefaction resistance under different load sequences. A comprehensive assessment is conducted to understand the evolution of the repeated liquefaction resistance. The test results indicate that clayey sand exhibits the lowest liquefaction resistance during the second liquefaction event. Repeated liquefaction is dominated by stress-induced anisotropy at earlier events and relative density at the final events.

Experimental study on the influence of clay content on the shear strength of silty soil and mechanism analysis

Experimental study on the influence of clay content on the shear strength of silty soil and mechanism analysis

Influence of Clay Content on Crack Evolution of Clay–Sand Mixture

Clay particles have an important influence on the cracking of clay–sand mixture, but the quantitative relationships between the clay content and crack evolution of the clay–sand mixture are still not clear. In order to explore the crack evolution process of the clay–sand mixture under different clay content conditions, we prepared nine groups of saturated clay–sand mixture samples with different clay contents and carried out drying experiments and Brazilian tests. The geometric dimensions and development forms of soil cracking were quantitatively analyzed by taking pictures of the sample cracks, image processing, and weighing the variation of the soil mass at the corresponding time during the drying process. The results showed that when the clay content was greater than 50%, the development process of the clay–sand mixture cracks can be divided into three stages: the formation stage of main cracks, the generation stage of the autonomously derived secondary fractures, and the stage of cracks widening. When it was less than 50%, the cracks in the development process of clay–sand mixture cracks had the characteristics of short length, dense crack spacing, no main cracks, and no obvious stage. The clay could add the tensile strength of the mixture and restrain crack development. The clay content had a significant effect on the shrinkage cracking and crack development process of soil, which shows that with the increase in the clay content, the tensile strength increases and restrains the crack development; the crack rate increases continuously and the width of cracks become larger; the lower the clay content, the lower is the crack rate and the smaller is the average crack width. The water content of samples with different clay soil contents all nonlinearly decreased with the increase in drying time, and the corresponding residual water content increased with the increase in the clay soil content at the same time. The water content of initial cracking, stable crack length, stable crack width, and stable block of the clay–sand mixture increased with the increase in the clay content, and the water content of the stable crack length was the same as that of the stable block number.

A Numerical Investigation to Determine the p–y Curves of Laterally Loaded Piles

This paper focuses on a numerical approach to finding the p–y curves for laterally loaded piles. The Drucker–Prager plastic model is employed and implemented within a finite element MATLAB code. The pre- and post-processing code for Gmsh and related numerical tools are established as well. The p–y curve results from this new approach have been validated and compared to the typical design equations of API (American Petroleum Institute) and Matlock. The validation reveals that the code leads to lower p–y curves than the API and Matlock equations when the horizontal displacement is less than 0.35 times the diameter of the pile (B). A sensitivity analysis of the number of elements and the interface thickness is presented. The results indicate that the obtained p–y curves are independent of the two factors. Finally, the influence of clay content on the p–y behavior is investigated by the implemented MATLAB code. When y < 0.15B, the same lateral capacity values are resulted at clay contents of 27.5% and 55%, and they are higher than the ones for 0% clay content. The p–y curves show a decreasing trend with increasing clay content after y > 0.15B.

Copolyamide-Clay Nanotube Polymer Composite Nanofiber Membranes: Preparation, Characterization and Its Asymmetric Wettability Driven Oil/Water Emulsion Separation towards Sewage Remediation.

To address the problem of ever-increasing oily wastewater management, due to its directional liquid transport property, membranes with asymmetric wettability can be effectively used for emulsion separation. This study reports the synthesis of electrospun polymer–clay nanocomposite nanofibers, using co-polyamide polymer (COPA) and halloysite nanotubes (HA) as filler. The influence of clay content on the morphological, thermal and dielectric properties of the polymer composite nanofiber was investigated comprehensively to address the material characteristics of the developed system. The surface structure analysis and contact angle measurements of the electrospun composite nanofibers confirms the change in surface roughness and wettability when the fillers are added to the polymer. The porosity of the composite electrospun nanofiber membrane was found to be 85% with an oil adsorption capacity of 97% and water permeability of 6265 L/m2 h. Furthermore, the asymmetric wettability-driven oil/water emulsion separation abilities of the as-synthesized membranes shows that the separation efficiency of the composite fiber membrane is 10% improved compared to that of the neat fiber membrane, with improved separation time.

Comparison of Various Permeability Methods Applied upon Clay Concretes–Statistical Evaluation

Abstract In this article, comparison of different permeability test methods was conducted using data obtained from measurements done on clay concretes. Two raw clay types were used as partial cement replacements for up to 40 % clay and employed to prepare 150-mm cubes of clay concretes at 0.70–0.85 water/cementitious ratios. Cylindrical specimens were cored from the cubes and used to conduct permeability measurements. The different permeability methods conducted include triaxial water permeability, air permeability, oxygen permeability, and water penetration. The tests were conducted using various fluid types consisting of air, gas, or water. Statistical analysis techniques were used to evaluate the permeability test methods. In addition, a leaching study was also conducted. It was found that the use of clay in concrete enhanced leaching of calcium, which, in turn, adversely influenced pore parameters and concrete permeability. Of the various tests used, the triaxial water permeability method was the most sensitive technique towards the influence of clay content in concretes, while the water penetration method was least sensitive and perhaps most suited for permeability testing of clay concretes. Of the methods evaluated, only the water penetration method and triaxial water permeability under a non-steady-state condition of testing were found to be interchangeable.

Influence of clay content on microstructure and flexural strength of in situ reaction bonded porous SiC ceramics

The aim of the present study is to reveal the effects of clay contents on in situ reaction bonding of SiC, phase development, microstructure, porosity and mechanical properties of porous SiC ceramics. Porous silicon carbide (SiC) ceramics are prepared in air at 1400 °C for 1 h using alumina as bond phase additive and variable amount of clay as sintering aids and compared their properties. The ceramics prepared with only alumina additive obtained with flexural strength of 28 MPa at porosity 38 vol% without any characteristic peak for mullite. The mullitization was almost completed at 1400 °C with addition of 3 wt% clay. It was found that the addition of clay strongly promoted the phase transformation towards mullite at lower temperature. A high flexural strength of 72 MPa was achieved at porosity level of 33 vol% in the sample prepared with 5 wt% clay due to the enhancement of necks at the contacting points.

The influence of clay content on submarine slope failure: insights from laboratory experiments and numerical models

Abstract Submarine slope failures pose risks to coastlines because they can damage infrastructure and generate tsunamis. Passive margin slope failures represent the largest mass failures on Earth, yet we know little about their dynamics. While numerous studies characterize the lithology, structure, seismic attributes and geometry of failure deposits, we lack direct observations of failure evolution. Thus, we lack insight into the relationships between initial conditions, slope failure initiation and evolution, and final deposits. To investigate submarine slope failure dynamics in relation to initial conditions and to observe failure processes we performed physical experiments in a benchtop flume and produced numerical models. Submarine slope failures were induced under controlled pore pressure within sand–clay mixtures (0–5 wt% clay). Increased clay content corresponded to increased cohesion and pore pressure required for failure. Subsurface fractures and tensile cracks were only generated in experiments containing clay. Falling head tests showed a log-linear relation between hydraulic conductivity and clay content, which we used in our numerical models. Models of our experiments effectively simulate overpressure (pressure in excess of hydrostatic) and failure potential for (non)cohesive sediment mixtures. Overall our work shows the importance of clay in reducing permeability and increasing cohesion to create different failure modes due to overpressure.

Test on Compaction Reinforcement Effect of Sand

In fracture or compaction grouting projects of sand layer, there exist many compacted sand regions on both sides of grout veins or around grout bulbs. It has an important effect on the final reinforcement effect of the sand layer that how much performance of the sand layer is improved after being compacted. Compression modulus, cohesion, and permeability coefficient are selected to be the performance indexes of the compaction reinforcement effect of sand. The relationship between the performance properties of sand and grouting pressure has been tested and analyzed. And influences of clay content and initial water ratio of sand on the compaction reinforcement effect have been studied. Results show that compaction can effectively improve the mechanical properties and impermeability properties of sand. Compression modulus of sand increases by 2∼18 times. The cohesion of sand increases from the scope of 9.4∼26 kPa to the scope of 40∼113.6 kPa. The permeability coefficient of sand decreases from the scope of 1.0 × 10−2∼ 8.33 × 10−4 cm/s to the scope of 2.19 × 10−4∼2.77 × 10−9 cm/s. When the clay content of sand is smaller than about 20%, sand cannot be reinforced effectively by compaction. Cohesion cannot be improved significantly and the permeability coefficient cannot be reduced markedly. A high initial water ratio of sand is beneficial to improve the compression modulus of compacted sand and goes against the improvement of cohesion of compacted sand. In addition, the initial water ratio has little effect on the permeability coefficient of compacted sand. In the end, fitting formulas have been developed to quantitatively describe the compaction reinforcement effect of sand by different grouting pressures.

Specific Heat Capacity of Soil Solids: Influences of Clay Content, Organic Matter, and Tightly Bound Water

The specific heat capacity of soil solids (cs) is a key parameter affecting heat storage and transfer in soils. In soil and geophysical applications,csis often assumed to be a constant with little variations across soils. In this study, we determined the specific heat capacities of nine soils by using differential scanning calorimetry (DSC), evaluated the effects of clay and organic matter (OM) contents on thecsof original and OM‐free soil samples at room temperature, and quantified the changes ofcscaused by the existence of tightly bound water (TBW). On average, the nine mineral soils had acsof 0.750 MJ Mg−1K−1, close to the commonly acceptedcsvalue. However, for the original soils dried at 105°C, clay content did not obviously influence thecsvalue andcsincreased linearly with both OM and TBW contents, indicating that inaccuratecsdata were likely if the changes in the OM fraction in soil solids and adsorbed TBW were ignored. In addition, relatively large values for the specific heat capacity of soil minerals (cm) were observed in fine‐textured soils compared with coarse‐textured soils. Two preliminary functions were developed for estimatingcmandcsfrom the soil's clay and OM contents.Core IdeasSoil specific heat capacity was measured via differential scanning calorimetry.The influences of clay, organic matter (OM), and tightly bound water on specific heat capacity were evaluated quantitatively.A linear relationship was developed between the specific heat of soil minerals dried at 200°C and clay content.The specific heat of soil solids dried at 105°C had a nonlinear relationship with clay and OM contents.

The Influence of Clay Content on Cave-ins in Tank Model Tests and Monitoring Indicators of Sinkhole Formation

Urban cave-ins may result from a sudden change in local hydrological, hydrogeological and anthropogenic conditions. Monitoring and predicting urban sinkholes is not straightforward, and solving the problem of urban cave-ins involves the incorporation of the fields of geodetics, geophysics and geochemistry. This paper examines the causes and consequences of sinkholes in sand-rich materials by using a small tank model apparatus. Tank model tests were conducted to simulate sinkhole formation, to gain a better understanding of the influencing factors of cavity formation, expansion and upward migration with different cavity water levels. Two commercial materials were used: Jumunjin sand and kaolinite clay. Materials with different grain-size distributions, i.e., sand (100% Jumunjin sand) and sand-clay mixtures (95% sand and 5% kaolinite clay), were considered to examine the roles of clay content in sinkhole risk. The test results show that the sand-rich materials exhibited a typical punching type of sinkhole subsidence and failure, and were very sensitive to changes in groundwater level, regardless of the grain-size distribution. The higher the groundwater level is, the higher the sinkhole risk is in terms of the speed of migration of the underground cavity fluids, cavity size and ground loosening. Therefore, sinkholes in urban areas covered with sand-rich materials are vulnerable to groundwater withdrawal. However, compared with pure sand, materials with small clay contents can reduce the time until collapse and the size of a sinkhole. Variations in pore water pressure may be used as a sinkhole indicator in areas where the ground deformation caused by groundwater depletion is considerable.

Evaluation of gas hydrate saturation by effective medium theory in shaly sands: a case study from the Qilian Mountain permafrost, China

Gas hydrate saturation calculation is a complex problem in the evaluation of gas hydrate reservoirs in the Qilian Mountain permafrost. From observations of the actual rock samples and experimental results from scanning electron microscopy images, gas hydrate reservoirs contain some extent of laminated and dispersed clay that affects the resistivity response of formation rocks. In light of this situation, we need to consider the influence of clay content when we evaluate the saturation of gas hydrate reservoirs in the studied area. We establish two kinds of resistivity models according to the distribution of clay and obtain corresponding methods to evaluate the saturation of gas hydrates based on the effective medium theory (EMT). The results show that the clay content in the shaly sand reservoirs varies over a large range, from 3.0 to 45.0%, and the average value is 19.4% indicating a high clay content overall. The comparison between experimental resistivity and simulated results show that the models based on EMT can be used to characterize the resistivity of reservoirs with different clay distributions. In the DK-2 well, the mean value of gas hydrate saturation obtained by the EMT is 35.6%, whereas that estimated using the Archie equation is 9.5%. In the DK-3 well, similarly, the mean value of gas hydrate saturation obtained by the EMT is 34.4%, whereas that estimated using the Archie equation is 15.5%. The gas hydrate saturation obtained from the EMT is higher than that obtained from the Archie equation because the former takes into account not only the content but also the distribution of clay. The method based on EMT is more effective for identifying and estimating gas hydrate reservoirs in the Qilian Mountain permafrost.

Experimental Study on Unconfined Compressive and Cyclic Behaviors of Mucky Silty Clay with Different Clay Contents

In this study, the unconfined compressive and cyclic behaviors of saturated mucky silty clay from the reclamation area of Dalian, which has two different clay contents, are investigated using the static and dynamic triaxial test systems. The influence of clay content on the residual strain and residual pore water pressure of undisturbed and reconstituted specimens are discussed. A scanning electron microscope (SEM) is used to observe the microstructures of the specimens. The unconfined compressive test results of the specimen with low clay content exhibits “collapse” characteristics. However, the corresponding specimen with high clay content exhibits a “sustained hardening” trend. The dynamic test results indicate that the residual pore water pressure, residual strain, and difference in the residual strain between the undisturbed and reconstituted specimens increase as the load increases. The ratio of the reconstituted residual strain to the undisturbed residual strain increases as the load increases, and this ratio is larger than the sensitivity of the soil. The residual strain of the specimen with high clay content exceeds the corresponding value of the specimen with low clay content. The stiffness degradation of the high clay content specimen is more obvious than that of the low clay content specimen. A power function-based residual strain model that contains the cyclic stress ratio (CSR) and number of cycles (N) is proposed. This model can be used to describe the residual strain with a CSR less than the critical CSR.

Eco-efficient earth plasters: influence of clay content, sand particle size and support

Earth construction, including the use of earth mortars, has been extensively used in the past. However, with the appearance of hydraulic binders, the use of earth strongly decreased for new construction and even to repair old earth buildings, whose best solution would be the use of compatible materials such as earth mortars.Due to the innumerable advantages of earth and with the growing concern on eco-efficient construction, the interest on earth construction has resurfaced, namely on earth mortars.In order to optimize the composition of an earth plastering mortar made with a defined clayish earth and two siliceous sands with different particle size, six compositions were assessed. Mortars with different volumetric ratios were applied in two different supports (on the back of a tile and on a brick) and planar specimens were also produced. Distinct characteristics were assessed, such as their visual appearance, shrinkage, surface cohesion, surface hardness, dry abrasion resistance, ultrasonic velocity, adhesive strength and thermal conductivity.It is possible to conclude that a higher clay content in the earth mortar composition increases the shrinkage and occurrence of cracking, the use of fine sand promotes high mass loss by abrasion, and the same mortar applied in different supports behave differently in terms of durability.

Hydration of Cement Minerals in a Hydraulic Dolomitic Binder

Dolomitic Roman cement was a widely used binder for construction purposes during the late 19th/ early 20th century in territory of Latvia. Because of its hydraulic properties and fast setting it was especially favorable for the usage for the cast elements of Art Nouveau style facades. The production of the material was discontinued in the middle of the 20th century. Nevertheless, there is a need of compatible material for restoration purposes that is not currently commercially available. A compatible binder has been synthesized from mixture of dolomite flour and clay. The research gives an insight of the ongoing chemical processes during the hydration of the cement minerals in the binder. The influence of clay content in compositions and of firing temperature on the physico-chemical properties and mineralogical composition of obtained material is estimated.

Experimental study on the liquefaction resistance of sand–clay mixtures: Effect of clay content and grading characteristics

ABSTRACTThis paper presents a laboratory study of the influence of clay content and grading characteristics on the liquefaction resistance of sand–clay mixtures. The study is performed using a triaxial apparatus on reconstituted sand–clay mixtures containing a low clay content ranging from 0 to 20%. The tests were performed on samples at a relative density of 73% under an initial confining pressure of 100 kPa. The results of this study indicate that the undrained shear strength (liquefaction resistance) of sand–clay mixtures is controlled by the percentage of clay fraction and grading characteristics of sand–clay mixtures. However, the results show that the increase in the clay content up to 15% reduces the resistance to liquefaction of the sand–clay mixtures. Also, the test results indicate that the undrained shear strength at the peak and the undrained residual strength and the maximal shear strength decrease with the increase in clay content. Indeed, they decrease with an increase in the uniformity coefficient and the coefficient of gradation, also it was found that they decrease with a decrease in the effective diameter and the mean particle diameter.

Engineering properties of unstabilized rammed earth with different clay contents

The physical and mechanical properties of unstabilized rammed earth with different clay contents were studied, which could provide a theoretical basis for the understanding of mechanical properties of unstabilized rammed earth and improve the construction design method and specification of RE buildings for sustainable development. The experimental results show that clay content has significant influences on the engineering properties of unstabilized rammed earth. For the fine-grained soil, the liquid limit, plastic limit and plasticity index increase gradually with the increase of the clay content. The influence of clay content on the optimum moisture content compared with the maximum dry density is more significant. The mechanical properties of unstabilized rammed earth are significantly affected by the clay content. There exist good linear relationships, which can be used for the mutual verification or calculation among the mechanical properties. An empirical model of unconfined compression strength with the FA/CA ratio as the main parameter is established, and the UCS may obtain the maximum with a FA/CA ratio of 5.77.

The effect of organic matter maturation and porosity evolution on methane storage potential in the Baltic Basin (Poland) shale-gas reservoir

Supercritical CH4 and subcritical CO2 and N2 gas adsorption measurements, combined with scanning electron microscopy (SEM) have been used to determine CH4 sorption capacity and pore characteristics for immature, mature and overmature shales from the Baltic Basin (Poland).Organic matter (OM) maturity exerts a dominant control on porosity evolution in micro- and mesoscale. In the Baltic Basin shales, the initial formation of micro- (<2nm) and mesopores (2–50nm) occurs in the oil window (beginning of catagenesis, vitrinite reflectance Ro~0.5-0.9%) due to primary cracking of kerogen that left OM highly porous. The expelled liquid hydrocarbons turned into solid bitumen that is responsible for pore blocking and significant decrease in micro- and mesopore volume in late mature shales (middle catagenesis Ro~0.9–1.2%). Micro- and mesopores were regenerated in advanced catagenesis (Ro~1.4–1.9%) due to secondary cracking of OM. The micropore volume in the Baltic Basin shales is mostly controlled by the OM content while the influence of clay content is minor and masked by OM.The CH4 adsorption in the Baltic Basin shales is predominantly controlled by OM micropore structure. The mesopore surface area and volume do not play an important role in CH4 sorption. The proposed adsorbed CH4 density equivalent (maximal absolute CH4 adsorption divided by micropore volume), revealed that the CH4 loading potential decreases in micropores with increasing maturity. The highest CH4 loading potential is linked to OM before metagenesis (Ro<2%) where the adsorbed CH4 density equivalent was found greater than the density of liquid CH4. This suggests that in addition to physical adsorption, absorption (dissolution) of CH4 in OM occurs. When OM content was reduced by the treatment with NaOCl solution, CH4 adsorption decreased significantly, suggesting that OM microstructure has much higher adsorption potential than that of clay microstructure.

Modeling the effects of microscale fabric complexity on the anisotropy of the Eagle Ford Shale

Microscale fabric influences the elastic properties of rock formations. The complexity of the microscale fabric of shale results from composition, platy clay minerals, kerogen, and their preferred orientation patterns. This microscale fabric is also the likely cause of the elastic anisotropy of the rock. In this paper, we have developed a comprehensive three-step rock-physics approach to model the anisotropic elastic properties of the Upper Eagle Ford Shale. We started with anisotropic differential effective medium modeling, followed by an orientation correction, and then a pressure adjustment. This method accounts for the microscale fabric of the rock in terms of the complex composition, shape, and alignment of clay minerals, pore space, and kerogen. In addition, we accounted for different pressure-dependent behaviors of P- and S-waves. Our modeling provides anisotropic stiffnesses and pseudologs of anisotropy parameters. The modeling results match the log measurements relatively well. The clay content, kerogen content, and porosity decreased the rock stiffness. The anisotropy increases with kerogen content, but the influence of clay content was more complex. Comparing the anisotropy parameter pseudologs with clay content shows that clay content increases anisotropy at small concentrations; however, the anisotropy stays constant, or even slightly decreases, as the clay content continues to increase. This result suggests that the preferred orientation of clay clusters is preserved at low clay concentration but vanishes at high clay concentration. This method could also be applied to other shales with carefully chosen parameters to model anisotropic elastic properties.