scholarly journals A Simulation Study on the Swelling and Shrinking Behaviors of Nanosized Montmorillonite Based on Monte Carlo and Molecular Dynamics

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Kaiwen Tong ◽  
Jianhua Guo ◽  
Shanxiong Chen ◽  
Fei Yu ◽  
Shichang Li ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Hydrogen Bonds ◽  
Water Content ◽  
Deep Level ◽  
Expansive Soils ◽  
Relative Concentration ◽  
Expansive Soil ◽  
Basal Spacing ◽  
Swelling And Shrinking

Montmorillonite is the main mineral source for the swelling and shrinking of expansive soils. The macroscopic phenomena of soil are affected by the action of deep-level nanosized minerals. In order to illustrate the nanoscale mechanism from the molecular level, a combination of Monte Carlo and molecular dynamics was used to explore the swelling and shrinking characteristics of montmorillonite. The results showed that the basal spacing, free swelling ratio, and void ratio were positively correlated with water content but were inversely proportional to the change of CEC. The hysteresis phenomena of swelling and shrinking were the most significant at a water content of 40%. Compared with the expansive soil, the nanoscale shrinkage curve of montmorillonite also included three stages of normal shrinkage, residual shrinkage, and no shrinkage. The relative concentration of water molecules conveyed information such as the thickness and position of the hydration film and explained the difference in swelling and shrinking caused by the above variables. The changes in the number and length of hydrogen bonds revealed the order of formation and the process of destruction of hydrogen bonds during the reaction. The similarity of the trends between the basal spacing, binding energy, and the number of hydrogen bonds indicated that the swelling and shrinking of the crystal layer are a reflection of the molecular interaction, and the hydrogen bonding is particularly critical.

scholarly journals Molecular Dynamics Simulation of Nanoscale Elastic Properties of Hydrated Na-, Cs-, and Ca-Montmorillonite

2022 ◽  
Vol 12 (2) ◽  
pp. 678
Author(s):  
Lianfei Kuang ◽  
Qiyin Zhu ◽  
Xiangyu Shang ◽  
Xiaodong Zhao
Keyword(s):  
Molecular Dynamics ◽  
Water Content ◽  
Elastic Properties ◽  
Bonding Strength ◽  
Stable State ◽  
Dynamics Simulation ◽  
Basal Spacing ◽  
Stiffness Tensor ◽  
Interlayer Water ◽  
Out Of Plane

The knowledge of nanoscale mechanical properties of montmorillonite (MMT) with various compensation cations upon hydration is essential for many environmental engineering-related applications. This paper uses a Molecular Dynamics (MD) method to simulate nanoscale elastic properties of hydrated Na-, Cs-, and Ca-MMT with unconstrained system atoms. The variation of basal spacing of MMT shows step characteristics in the initial crystalline swelling stage followed by an approximately linear change in the subsequent osmotic swelling stage as the increasing of interlayer water content. The water content of MMT in the thermodynamic stable-state conditions during hydration is determined by comparing the immersion energy and hydration energy. Under this stable hydration state, the nanoscale elastic properties are further simulated by the constant strain method. Since the non-bonding strength between MMT lamellae is much lower than the boning strength within the mineral structure, the in-plane and out-of-plane strength of MMT has strong anisotropy. Simulated results including the stiffness tensor and linear elastic constants based on the assumption of orthotropic symmetry are all in good agreement with results from the literature. Furthermore, the out-of-plane stiffness tensor components of C33, C44, and C55 all fluctuate with the increase of interlayer water content, which is related to the formation of interlayer H-bonds and atom-free volume ratio. The in-plane stiffness tensor components C11, C22, and C12 decrease nonlinearly with the increase of water content, and these components are mainly controlled by the bonding strength of mineral atoms and the geometry of the hydrated MMT system. Young’s modulus in all three directions exhibits a nonlinear decrease with increasing water content.

scholarly journals Studi Regangan Axial dan Lateral pada Tanah Ekspansif

2017 ◽  
Vol 19 (2) ◽  
pp. 121-127
Author(s):  
Lisa Fitriyana ◽  
Abdul Rochim
Keyword(s):  
Water Content ◽  
Expansive Soils ◽  
Retaining Wall ◽  
Expansive Soil ◽  
Axial Direction ◽  
Lateral Strain ◽  
Membrane Thickness ◽  
Test Results ◽  
Measurement Tools ◽  
Digital Caliper

Swelling and shrinkage abilities of soils are dangerous for buildings. According to Hardiyatmo (2014) There are two types of swelling in expansive soils that are the movement of lateral (horizontal) and axial (vertical). Oftentimes the deformation of soils cannot be supported by building stiffness. This damage can be seen in retaining walls, tunnel walls, and etc. With the aims to identify an expansive soil and to know its lateral and axial strains, an experimental study was performed. Swelling tests were conducted in a specimen having diameter (d) of 4,5 cm and height (h0) of 2 cm with the variations in : 1) water content wopt = 31% and 18%; 2) vertical pressure (pv) 1 kPa, 3.5 kPa and 6.9 kPa; and 3) membrane thickness (t) 0.7 mm and 0.5 mm. The strain in the axial direction was measured with a dial gauge that was set vertically parallel whereas the lateral strain is by measuring changes in diameter of the specimen with a digital caliper measurement tools. Based on the analysis on the identification results, the observed soil is classified as expansive soil with the expansion potential is high average. The test results show the same potential for the occurrence of lateral and lateral strain if the lateral retention (e.g. retaining wall) is weak. The largest lateral and axial soil development occurred at water content w0 = 18% are 15.7% and 15.8% respectively.

Effect of Heating Borehole Spacing on Plasticity of Expansive Soil

2020 ◽  
Vol 38 (7A) ◽  
pp. 1062-1068
Author(s):  
Falah H. Rahil ◽  
Husam H. Baqir ◽  
Nabeel J. Tumma
Keyword(s):  
Water Content ◽  
Representative Sample ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Heating System ◽  
Unit Weight ◽  
Initial Water Content ◽  
Initial Water ◽  
Dry Unit Weight ◽  
Laboratory Models

This paper presents the effect of spacing between boreholes heating on plasticity of expansive soils. The expansive soils used were prepared artificially by mixing Kut clay with different percentages of bentonite. Nine laboratory models of expansive soils having dry unit weight of 17.8 kN/m3 with 6% initial water content were prepared inside a steel box of (300 mm × 300 mm × 400 mm height).  A special heating system generates 400 Co for six hours was designed and manufactured for this purpose using 12 mm diameter electric heaters inserted through boreholes. Square pattern boreholes of 170 mm length with spacing (4.16d, 6.25d and 8.33d) were used. A representative sample were taken after heating from the center of the square pattern for measuring the plasticity of the soils. The results showed that the plasticity index remarkedly decreases compared with that before heating and increases with increasing bentonite and the spacing. It is also indicated that an expansive soil could be changed from high to low plasticity

scholarly journals Molecular Dynamics Simulation in the Interlayer of Mixed-Layer Clays Due to Hydration and Swelling Mechanism

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 586
Author(s):  
Yu Yang ◽  
Sanjeev Adhikari ◽  
Guoyuan Xu
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonds ◽  
Interaction Energy ◽  
Mixed Layer ◽  
Bound Water ◽  
Swelling Behavior ◽  
Dynamics Simulation ◽  
Basal Spacing ◽  
Water Interaction ◽  
Swelling Mechanism

The swelling behavior of clay minerals is widely known for its importance in soil and environmental sciences and its detrimental effects in engineering fields. Although more than 70 percent of all clays are of mixed-layer types, the vast majority of the previous experiments and simulations are focused on pure clays, which cause the swelling mechanism of the widespread mixed-layer clay (MLC) and its role in soils are little understood, especially the most common illite-montmorillonite (I-M) mixed-layer clay (MLC). This paper reports on a molecular dynamics (MD) study of the differences in swelling behavior between I-M MLCs containing K+ and Na+ and Na-montmorillonite (MMT). It captures the evolution of quantitative properties such as basal spacing d, interaction energy, and many hydrogen bonds in the clay interlayer, increasing hydration for the first time through the scripts. It is found that MLCs have smaller swellings than Na-MMT due to the asymmetric interlayer charges and mixed counterions in the I-M interlayer. However, in terms of the interaction energy for the in-depth reason of swelling, it is found that the clay-clay interaction energy and the clay-ion interaction energy drop, while the clay-water interaction energy increases with increasing hydration. In addition, the attractive interaction of clay-bound water seriously promotes swelling, and it is mainly composed of Coulomb interaction and Van der Waals interaction. The higher the K+ concentration, the more noticeable these phenomena are. Besides, it is also reported that the number and distribution mechanism of hydrogen bonds in MLCs are very different from that of pure clay. This work provides insight into the molecular mechanism for initial swelling and clay-bound water interaction in widespread MLCs. This will help to decipher its specific role in soils and minimize clay swelling.

The Tests on the Lime-Treated Expansive Soils Compaction Characteristics

2013 ◽  
Vol 405-408 ◽  
pp. 548-553
Author(s):  
Xin Zhong Wang ◽  
Rui Liu ◽  
Shu Jun Peng
Keyword(s):  
Water Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Dry Density ◽  
Maximum Dry Density ◽  
Compaction Characteristics ◽  
Lime Content ◽  
Compaction Energy ◽  
Wetting Time ◽  
Lower Height

The compaction characteristics of the lime-treated expansive soils from the planning airport in China's Ankang were studied through the heavy compaction tests. The results show that all these elements such as lime content, water content, soil height, wetting time have a certain effect on dry density. As the lime quality ratio increases, the optimum water content under heavy compacting standard of improved soils increases but the maximum dry density decreases. With the increase of lime content, the effect of water content on dry density decreases while the water content near to its optimum value. Soils with the lower height have higher dry density when compaction energy, lime content and water content unchanged. As the wetting time increases, the maximum dry density shows a decreasing tendency until after 48 h it remained stable. It indicates that with the same lime content the order of primary factors influence on dry density are water content, wetting time, soil height. Finally, the lime stabilizing principle to expansive soil is explained through by applying scanning electron microscope technique.

scholarly journals Characterization of the Undrained Shear Strength of Expansive Soils of High Water Content

2018 ◽  
Vol 206 ◽  
pp. 01002
Author(s):  
Zheng Su ◽  
Daokun Qi ◽  
Xinju Guo ◽  
Xiaojuan Xi ◽  
Liang Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Friction Angle ◽  
High Water ◽  
Ease Of Use ◽  
Triaxial Tests ◽  
High Water Content

In recent years, engineering constructions increase rapidly in western and central areas of China, where expansive soil widely distributes. Since expansive soil is sensitive to water content, the characterization of its shear strength should be carefully conducted. For simplicity and ease of use, the Mohr-Coulomb criterion is often adopted to describe the shear strength of expansive soil. In this paper, the physical meaning of the cohesion and frictional strength of expansive soil are explained, and the variations of the strength parameters with water content are investigated. By fitting to the experimental results from direct shear test and triaxial tests, the changing characteristics of cohesion and friction angle with water content are obtained.

scholarly journals Pengaruh Kadar Air Awal Dan Surcharge Pressure Pada Uji Karakteristik Pengembangan Tanah Ekspansif

2017 ◽  
Vol 23 (2) ◽  
pp. 124
Author(s):  
Wilis Diana ◽  
Edi Hartono ◽  
Anita Widianti
Keyword(s):  
Water Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Dry Density ◽  
Initial Water Content ◽  
Expansive Clay ◽  
Initial Water ◽  
Swelling Properties ◽  
Swell Percent ◽  
Swell Pressure

Expansive soils experience volumetric changes due to water content changes. These volumetric changes cause swell and shrink movement in soils, which in turn will inflict severe damage to structures built above them. A Proper understanding of how the expansive soil behaves during the wetting/drying process is essential for assessing the mitigation action of expansive soil hazard and design suitable foundation. The structures that build above expansive soil bed are susceptible to heave and to withstand swell pressure, thus the swell pressure must be considered in the design. This study focuses on swelling properties of two expansive clay from Ngawi, East Java and Wates, Yogyakarta. Laboratory test on disturbed samples is used to identified and to measured swelling properties. A series of swelling test was performed under constant soil dry density. The influence of initial water content and surcharge pressure on swelling properties (i.e swell percent and swell pressure) of compacted samples were investigated. The swelling properties test used ASTM standard 4546-03 method B. It was found that the lower initial water content the higher the swell percent, but the swell pressure seems not to be affected by initial water content. At the same initial water content, swell percent decrease with the increase of surcharge pressure, but swell pressure remains unchanged.

scholarly journals Factors affecting the swelling pressure for Jerash expansive soil

2021 ◽  
Vol 3 (2) ◽  
pp. 44-51
Author(s):  
Talal Masoud ◽  
Abdulrazzaq Jawish Alkherret
Keyword(s):  
Water Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Dry Density ◽  
Initial Water Content ◽  
Content Increase ◽  
Initial Water ◽  
Factors Affecting ◽  
Water Content Increase

  In this study for factors effecting the swelling pressure of jerash expansive soils were investigated in this study, effect of initial dry density and effect of initial water content on the jerash expansive soil were investigated.It show that as the initial dry density decrease from 1.85 gm/cm3  to1.25 gm/cm3 , the swelling pressure also decrease are from 3.1  to 0.25gm/cm2   also it show that as the initial water content increase from 0%to 15% , the swelling pressure of jerash expansive soil decrease from 2.65 gm/cm2  to 1.35 gm/cm2  .  

scholarly journals Study on Soil-Water Characteristics of Expansive Soil under the Dry-Wet Cycle and Freeze-Thaw Cycle considering Volumetric Strain

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Lisi Niu ◽  
Aijun Zhang ◽  
Jiamin Zhao ◽  
Wenyuan Ren ◽  
Yuguo Wang ◽  
...  
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Expansive Soils ◽  
Volumetric Strain ◽  
Expansive Soil ◽  
Volumetric Water Content ◽  
Dry Density ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

This paper targets the expansive soils in Heilongjiang and Ankang to explore the influence of initial dry density, dry-wet cycle, and freeze-thaw cycle on the soil-water characteristics. The centrifuge method was used to obtain the soil-water characteristic curves (SWCCs) with different conditions. The volumetric strain of SWCC was modified based on the shrinkage test, and the corresponding fitting equations considering different factors were established. The results show that the volumetric water content is modified to consider the volume shrinkage effect of expansive soil, and the modification is more obvious in the high matric suction range. The smaller the initial dry density is, the worse the water-holding capacity of the sample is, and the smaller the air intake value is. The greater the time of the dry-wet cycle is, the greater the saturated volumetric water content of the sample is, and the corresponding water-holding capacity is significantly reduced. When the dry-wet cycle increases to a certain extent, the structure becomes stable. With the increase of the freeze-thaw cycle, the saturated volumetric water content first decreases and then increases. Similarly, after several times of the freeze-thaw cycle, the structure is basically stable. The fitted Gardner model equations under different conditions were proved to be able to describe the SWCCs of the two targeted expansive soils.

Numerical Methods for the Kinetic Theory of Fluids

2018 ◽  
Author(s):  
Sauro Succi
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Numerical Methods ◽  
Kinetic Theory ◽  
Computational Efficiency ◽  
Lattice Boltzmann ◽  
Direct Simulation Monte Carlo ◽  
Particle Methods ◽  
Direct Simulation ◽  
Simulation Monte Carlo

This chapter provides a bird’s eye view of the main numerical particle methods used in the kinetic theory of fluids, the main purpose being of locating Lattice Boltzmann in the broader context of computational kinetic theory. The leading numerical methods for dense and rarified fluids are Molecular Dynamics (MD) and Direct Simulation Monte Carlo (DSMC), respectively. These methods date of the mid 50s and 60s, respectively, and, ever since, they have undergone a series of impressive developments and refinements which have turned them in major tools of investigation, discovery and design. However, they are both very demanding on computational grounds, which motivates a ceaseless demand for new and improved variants aimed at enhancing their computational efficiency without losing physical fidelity and vice versa, enhance their physical fidelity without compromising computational viability.

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