Liquid Plastic Limit Research Articles

Study on microscopic pores and physico-mechanical properties of red clay modified by calcium carbonate

Red clay as a special soil has a high liquid-plastic limit, water swelling and water loss shrinkage. To solve the problems red clay was modified by calcium carbonate produced in Hezhou, Guangxi. The Liquid-plastic limit, water loss shrinkage, nuclear magnetic resonance (NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and consolidated drained (CD) triaxial shear test were carried out on the modified soils. The results show that when the calcium carbonate content is 20%, the plastic limit is 24.38 and the liquid limit is 38.67, which are reduced by 35.04% and 22.16%, respectively. The Montmorillonite content in the modified soil is reduced by 27.7%. The shrinkage coefficient decreased from 0.325 to 0.102. The NMR test shows that the content is 5% and 10% would lead to a decrease in the macropores and an increase in the micropores pores. The phenomenon is the opposite (15% and 20%). All contents led to the porosity increase. The calcium carbonate content of 5% was selected for triaxial shear tests to obtain the stress-strain curves. The Duncan-Zhang was used to predict the modified soil. The model has a large error in the prediction of the peak of the principal stress difference, but the overall trend is relatively consistent. Therefore, the correction coefficient related to the confining pressure was introduced. The corrected model fits the triaxial shear test well. The research provides a method for the liquid-plastic limits and shrinkage properties of modified red clay, explores the influence of calcium carbonate content on microscopic pores, and the correction of the model provides a theoretical basis for practical application.

Experimental Study on the Effects of Heavy Metal Pollution on Soil Physical Properties and Microstructure Evolution

Soil heavy metal pollution poses a formidable challenge for environmental protection professionals. This study delves into the impact of zinc and lead pollution on the particle size distribution, liquid-plastic limit, permeability, shear strength, and other pertinent physical and engineering properties of clay. The alterations in the microstructure of soil contaminated by heavy metals were scrutinized using a scanning electron microscope. The findings reveal that as the concentration of heavy metals in contaminated soil rises, there is a concurrent decrease in the liquid limit, plasticity index, and silt content. This, in turn, leads to the deterioration of the original fluidity and plasticity of the soil, accompanied by a reduction in fine particles. Resistivity tests indicate that an escalation in water content results in a decrease in resistivity, an increase in porosity leads to an increase in resistivity, and an elevation in the concentration of heavy metals precipitates a sharp decline in resistivity due to the heightened conductivity of heavy metal ions. Heavy metal pollution induces structural changes in the soil, particularly in pore size, thereby influencing the permeability coefficient.

Influence Mechanism of Water Content and Compaction Degree on Shear Strength of Red Clay with High Liquid Limit.

To investigate the influencing factors and mechanisms of shear strength of red clay with a high liquid limit, which was selected at different milepost locations based on the Nanning Bobai Nabu Section Project of the Nanning Zhanjiang Expressway, the basic physical properties of red clay were determined using a liquid plastic limit test, compaction test, inductively coupled plasma optical emission spectrometer (ICP-OES), and X-ray fully automatic diffractometer (XRD). Red clay with a high liquid limit was selected. Furthermore, the direct shear test was used to study the effect of different water contents and compaction degrees on the shear strength. The experimental results demonstrate that under the same compaction degree, the shear stress of the soil sample increases significantly with an increase in normal stress, and the greater the water content, the smaller the shear stress of the soil sample. At 200 kPa, the shear strength of soil samples with 24% water content is 57%, 46%, and 35% of the shear strength of soil samples with 15% water content under different compaction degrees(K) of 86%, 90%, and 93%, respectively. Under the same moisture content, the shear stress of the soil sample shows an increasing trend with an increase in the degree of compaction, and the greater the compaction degrees, the greater the shear stress of the soil sample. The cohesion c and internal friction angle φ of soil samples increase with an increase in the compaction degree, but the increase in cohesion c is also affected by the water content. Under the condition of low water content, the cohesion c of soil samples can be increased by 1.06 times when the water content is 15% and by 0.47 times when the water content is 18%. Under the condition of high water content, the cohesion c of soil samples with 21% water content only increases by 0.3 times, and that with 24% water content only increases by 0.35 times.

Engineering Properties and Environmental Impact of Soil Mixing with Steel Slag Applied in Subgrade

The purpose of this study was to evaluate the feasibility of the large-scale application of steel slag (SL) in subgrade. Subgrade materials with three kinds of SL proportions were first prepared. Then, a compaction test, liquid-plastic limit combined-measurement test, and a California bearing ratio (CBR) test were applied to determine the best proportion between SL and intact soil (S), i.e., SL/S. Subsequently, static and dynamic tests and a volume stability test were carried out for soil mixed with SL at the optimum proportion (SSL). In addition, a composition analysis of infiltration fluid and a permeability test of SSL were performed. The test results showed that compared to S, the physical properties of SSL were significantly improved, especially the liquid-plastic limit, as well as the soil water stability. The optimum proportion of SL was determined as 50% of soil by mass. At the optimum proportion, SSL had the highest CBR value of 60%, which had both economic and engineering compaction performance, leading to a large-scale utilization rate of SL. The static and dynamic characteristics showed that the addition of SL would greatly improve the shear strength and dynamic modulus of soil, mainly expressed as the increase of internal friction angle. The volume stability of SSL could also meet the requirements of the Chinese specification. After adding 2% cement, the strength and stability of SSL was further improved. In addition, the environmental impact test proved that the infiltration liquid did not pollute surface water nor underground secondary water. Although the permeability coefficient of SSL with the optimum proportion of 50% was higher than that of pure soil, it still belonged to the normal value of clay and silty clay, and good impermeability would ensure the controllability of potential trace elements. Based on the test results of mechanical properties and environmental impact, SSL proved to have the potential for green road material engineering properties. This study proposes a reliable and practical method to promote the utilization of steel slag.

Weak Expansive Soil Physical Properties Modification by Means of a Cement-Jute Fiber

Sixteen groups of comprehensive tests have been conducted to investigate the modifications in the physical properties of a weak expansive soil due to the addition of a cement jute fiber. The tests have been conducted to analyze the liquid plastic limit, the particle distribution and the free expansion rate. The results show that: (1) With an increase in the cement-jute fiber content, the free expansion rate of the modified expansive soil gradually decreases, however, such a rate rebounds when the fiber content exceeds 0.5% and the cement content exceeds 6%. (2) With an increase in the cement percentage, the particle unevenness coefficient (Cu) and curvature coeffi- cient (Cc) of the modified expansive soil tend to grow gradually. The Cc coefficient reaches 1.0 when the cement content is 6%. The unevenness coefficient of 16 soil samples is greater than 5.0, however, the Cu coefficient decreases when the cement content reaches 6%. (3) The plastic limit of soil increases as the cement content is made higher, while the liquid limit and plastic index decrease gradually. When the content of the modified material is 2% + 0.1%~2% + 0.7% (Cement content + jute fiber content), the change of particle size distribution is most obvious. (4) When the contents of cement and jute fiber are is 6% and 0.5%, respectively, the modification induced in the physical properties of soil samples corresponds to the best case.

Experimental study of the effect of bound water on the shear strength and structural units of Malan loess

The structural specificity and hydrological sensitivity of loess have a big impact on its strength, deformation and long-term stability and safety. This topic is being actively researched, and focuses on the macromechanical behaviour of the shear strength of loess and its micromechanisms from the perspective of bound water. In this study, based on the combined determination of isothermal adsorption and the liquid–plastic limit, bound water is analysed qualitatively and quantitatively, and the entire humidity sequence is divided in a new method. The shear strength of Malan loess measured by the direct shear test is also analysed to investigate the relationship between bound water, shear strength and basic structural units. The results show that the adsorption patterns for the Malan loess in the three regions studied are approximately the same but, at the same humidity, their maximum moisture content ( W мг ) was, from highest to lowest, 7.13% in Chan he, 6.54% in Yan'an and 5.54% in Hei fang tai, which is related to clay minerals and their contents in the soil. In addition, the change in strength of the loess is divided into three stages using the maximum moisture content ( W мг ) and plastic limit ( W P ) as the characteristic moisture content. The patterns of strength change for the loess in the three regions is similar throughout the moisture content sequence: all stages show a negative correlation between moisture content and shear strength but the internal mechanism of each stage is not the same due to the different connection forces between the basic structural units of the loess. The change in bound water content caused by the cementation of glue and clay particles also yields certain changes in cohesion, which is linearly fitted to the shear strength and its parameters. Finally, the bound water in the soil changes the microstructure of the soil, and determines the combination characteristics and contact mode of the ‘core clothes’ in the microagglomerate structure of the loess. This study describes the essence of soil–water structural interactions and provides theoretical references for applications in geotechnical engineering fields such as slope protection and road construction.

Screening Additives for Amending Compacted Clay Covers to Enhance Diffusion Barrier Properties and Moisture Retention Performance

The cover systems in contaminated sites have some problems, including desiccation cracks, which would lead to degradation of the barrier performance. This study presented a systemic laboratory experimental investigation on the liquid–plastic limit, moisture retention, hydraulic conductivity (k), and gas diffusion barrier properties of amended compacted clay by attapulgite and diatomite for controlling desiccation cracks and migration of water and volatile organic compounds (VOCs). The results showed that the attapulgite could enhance the moisture retention and liquid limit of amended compacted clay. Diatomite could reduce the gas diffusion coefficient (Dθ) significantly. The compacted clay amended by the dual-additives component of attapulgite and diatomite could enhance the liquid limit, moisture retention percent, gas barrier property, and hydraulic performance compared with the unamended clay. Based on the experimental data obtained, the dosage of additives was targeted to be 5%. The moisture retention percent of dual-additives (attapulgite 4% and diatomite 1%) amended clay increased by 82%, the k decreased by 25%, and the Dθ decreased by 42% compared with unamended clay. Scanning electron microscopy (SEM), BET-specific surface area test method (BET), Mercury Intrusion Porosimetry (MIP), and thermogravimetric analysis (TGA) indicated the enhancement mechanism of additives-amended compacted clay.

Variations in the mineral structures dominating solute mobilization during clay compaction

Microbial-mediated redox reactions typically control the solute mobilization in groundwater systems, in which the clay aquitard is usually a triggering factor of the release of the dissolved organic carbon, ammonium, and iron into the aquifer during pore water discharge and clay compaction. However, solute mobilization inside the aquitard during clay compaction is generally mistaken for a similar water–rock interaction process in aquifers controlled by microbial-mediated redox reactions. Through a simulation experiment on argillaceous sediment compaction, we tested the currently accepted solute mobilization mechanism and determined that the variation in the mineral structure dominates it. The variation in the mineral structure occurs in low symmetry minerals, such as clay minerals, and is controlled by the sediment moisture content, the liquid-plastic limit, and the effective stress. When the sediment moisture content decreases to below the plastic limit through pore water discharge and compaction, sudden changes in the mineral structure occur, releasing iron and capturing ammonium through variations in the relative position of the Si-O tetrahedrons and isomorphism of similar atoms without the participation of microbial-mediated redox reactions. These results suggest that the biochemical reactivities of organic carbon, iron, and ammonium are sometimes overestimated, i.e., when the role of the physical processes is ignored, in solute mobilization during clay compaction, which warrants more attention and investigation.

Analysis of Mechanical Properties of Loess with Cement Incorporation Ratio

Taking loess as the research object, the influence of cement content on mechanical properties of loess was studied. Firstly, the basic physical parameters of loess were obtained through laboratory physical index test, and improved by using Portland cement. Secondly, under different incorporation ratios (3%, 5%, 7%, 9%), heavy compaction test and liquid-plastic limit test were carried out respectively to obtain mechanical parameters of cement-improved loess. Finally, the shear strength parameters and compressive strength of the improved soil samples are obtained by unconsolidation undrained triaxial shear test and unconfined compressive strength test. The results show that the liquid limit, plastic limit and plastic index of loess improved by adding cement increase compared with the original soil sample, indicating that the binding force between soil particles is improved and the plasticity is enhanced. The variation range of dry density and water content has no obvious relationship with the content of cement. At the same time, the compressibility of soil is reduced and the collapsibility of soil is eliminated. With the increase of age, the strength of cement-modified soil also increases. Through unconsolidated and undrained triaxial shear tests and unconfined compressive strength tests, the strength of loess improved significantly after adding cement, and the strength of soil-cement increased with the increase of cement content, and water stability was obviously improved.

Analysis of Mechanical Properties of Loess with Lime Incorporation Ratio

Taking loess as the research object, the effect of lime content on mechanical properties of loess was studied. Firstly, the basic physical parameters of loess were obtained by laboratory physical index test and improved by lime. Secondly, the mechanical parameters of lime-modified loess were obtained by heavy compaction test and liquid-plastic limit test under different incorporation ratios (3%, 5%, 7%, 9%). Finally, the shear strength parameters and compressive strength of improved soil samples were obtained by unconsolidated and undrained triaxial shear test and unconfined compressive strength test respectively. The results showed that the liquid limit, plastic limit and plastic index of the loess improved by adding lime increased compared with the original soil sample, indicating that the binding force between soil particles was improved and the plasticity was enhanced. The variation range of dry density and water content had no obvious relationship with the dosage of lime. At the same time, the compressibility of soil is reduced and the collapsibility of soil is eliminated. With the increase of age, the strength of lime-modified soil also increases. Through unconsolidated and undrained triaxial shear tests and unconfined compressive strength tests, the strength of the loess improved by adding lime is significantly improved, and the strength of soil-cement increases with the increase of the dosage, and the water stability is obviously improved.

Experimental Study on Physical Mechanical Properties and Microstructure of Diatomite Soil in Zhejiang Province, China

Diatomite soil is a kind of bio-siliceous soil with complex composition and special structure, the physical and mechanical properties of diatomite soil are very important for the engineering project. In this paper, the physical properties, mechanical properties, and microstructure of diatomite soil in Zhejiang Province are studied by geotechnical tests and microscopic tests from the macroscopic and microscopic perspective. The results show that: (1) The diatomite soil has special properties different from other soils, including small particle size, low specific gravity value, high liquid-plastic limit, and low compressibility, and the strength indexes c and φ of diatomite soil will decrease with an increase in soil water content; (2) in the triaxial test, when the dry density of diatomite soil increases from 1.30 g/cm3 to 1.50 g/cm3, the effective internal friction angle of diatomite soil increases from 5.6° to 14.5° and the effective cohesion increases from 30.9 kPa to 49.6 kPa. The stress–strain curve of diatomite soil changes from weak softening type to weak hardening type when the confining pressure is above 200 kPa; (3) the diatomite soil has high porosity due to its unique microstructure; it is rich in aluminum oxides and minerals, which will greatly reduce the engineering performance of diatomite soil.

Physico-mechanical properties of thick paleosol in Q1 strata of the Chinese Loess Plateau and their variations during tunnel excavation

To cope with the increasing demand for traffic capacity in the Chinese Loess Plateau, building additional tunnels are required in the thick paleosol strata of Q1 strata. The thick paleosol strata consist of multiple paleoclimatic stratigraphic units, and the behavior and properties of the paleosol in each unit, which are believed to be quite different from those of common loess, remain scarcely investigated. In this work, we focused on the thick paleosol strata in Eastern Gansu of the Chinese Loess Plateau, the physico-mechanical properties of the paleosol in different paleoclimatic stratigraphic units were analyzed, and the relationship between the chemical properties, microstructures, and physico-mechanical properties of the paleosol was discussed. Besides, the water content of the paleosol was measured on site during the tunnel excavation in the thick paleosol strata, and the trends of the physico-mechanical properties of the paleosol during the excavation were also explored. We found that in the thick paleosol strata, the dry density, water content, liquid plastic limit, swelling potential, and mechanical strengths of the paleosol samples from different paleoclimatic stratigraphic units did not show large discrepancies, but obvious differences could be found in the grain size, maximum swelling pressure, and maximum swelling strain. The subtle variation of the water content had modest effects on the contact mode and cementation degree of the particles, but it could considerably influence the hydration film thickness of the clay mineral particles, which explains the distribution of mechanical properties of the paleosol samples. During the tunnel excavation in the thick paleosol strata, the paleosol around the tunnel sustained high and stable mechanical strength, while its swelling pressure and water content showed a consistent trend. The results can provide basic parameters for the stability analysis of the tunnel built in the thick paleosol strata.

Experimental Study on Physical-Mechanical Properties of Expansive Soil Improved by Multiple Admixtures

The treatment of expansive soil is always a difficult problem in engineering. Using coal gangue, fly ash, and other solid waste to treat expansive soil has gradually become a new way of energy saving and environmental protection. Most of the existing studies focus on using one or two kinds of admixtures to improve expansive soil, but there are few studies on improving expansive soil with multiple admixtures. In this paper, the expansion and shrinkage deformation and strength characteristics of expansive soil modified by coal gangue, fly ash, and lime are studied experimentally. Nine groups of different mixing schemes were designed through orthogonal tests, and the physical and mechanical properties of the improved expansive soil under different mixing ratios were tested. The sensitivity analysis of the test results was carried out to study the effect of each admixture on the improved expansive soil under different mixing ratios, and the optimal mix ratio under different conditions was obtained. The optimal mix ratio is 8% for coal gangue, 11% for fly ash, and 6% for lime. Further scanning electron microscopy (SEM) tests were carried out to analyze the microstructure of the improved expansive soil and explore the improvement mechanism of the multiadmixture. The results show that the optimal moisture content and the maximum dry density of the expansive soil with ash are decreased, and the properties of liquid plastic limit, free expansion rate, shear strength, and unconfined compressive strength of the expansive soil are improved obviously. Through the analysis of the comprehensive balance method, it is found that the content of lime has the greatest influence on the improvement effect of expansive soil, followed by that of coal gangue, and the least is that of fly ash. SEM structure analysis reveals that the particles of improved expansive soil are mainly aggregates, the soil structure is dense, particle agglomeration increases, and the overall structure is stronger. The research results can provide reference for the improvement of expansive soil with various admixtures and the resource utilization of coal gangue, fly ash, and other solid wastes.

Experimental Study on Physical Properties of Octadecylamine Modified Expansive Soil

Taking weak expansive soil as the research object, octadecyl primary amine (octadecylamine) was mixed into remolded expansive soil as a water repellent, and modified samples with different octadecylamine content were configured. The water-repellent grade of the modified expansive soil was measured by the dripping water penetration time method, the boundary moisture content test of the modified expansive soil was carried out, and the change law of the liquid plastic limit of the modified expansive soil with different octadecylamine content was analyzed. The results show that with the increase of the octadecylamine content, the liquid limit of the expansive soil gradually decreases, the plastic limit gradually increases, and the plasticity index gradually decreases. The above research results can provide a test basis for the engineering application of modified expansive soils.

Experimental investigation into non-collapsible loess-like soil's engineering geological properties under the influence of freeze–thaw cycles

Recurrent freeze–thaw cycling is a powerful weathering process that subjects soil to frost heave and thaw settlement. The cycling significantly changes the soil structure and leads to particle recombination, ultimately causing deterioration of the soil's properties. Herein, we investigated the effect of freeze–thaw cycles on loess-like soil in seasonally frozen regions; specifically with respect to the engineering geological properties, such as changes in grain-size distribution, liquid–plastic limit and collapse behaviour. The results indicate that over the course of 20 freeze–thaw cycles, the soil samples’ dry density decreased, the particle diameter of each soil fraction changed in a bi-directional manner (large particles were broken into finer sizes and fine particles agglomerated into larger particles), and the liquid limit and plasticity index first increased and then decreased. An increase in the initial water content resulted in more significant changes. In contrast to the undisturbed soil samples, the freeze–thaw cycles caused non-collapsible remoulded loess-like soil to collapse. Furthermore, microscopic evaluation allowed us to determine the collapse mechanism. Essentially, after the freeze–thaw cycles, the quantity of micropores in the soil decreased, whereas that of medium pores and macropores significantly increased. In addition, a trellis structure, similar to the typical loess structure, was generated.

Experimental Study on Model of Red Mud Duncan-Zhang Model of an Aluminum Company in Shanxi

This paper takes the red mud, an auxiliary product of aluminum smelting industry in an aluminum factory in Shanxi Jinzhong as the research object, and tests the basic physical and mechanical parameters and Duncan-Zhang model parameters of red mud. According to the geotechnical test procedure, the parameters such as particle size gradation and liquid plastic limit of red mud were obtained. The stress-strain relationship curve of the red mud material was obtained by the triaxial consolidation compression test. The Duncan-Zhang model parameters of the red mud material were obtained according to the experimental data, which provided a reference for the stability analysis and calculation of the red mud yard in the future.

Experimental study on the basic physical properties of diesel contaminated soil

In order to study the change of the properties of petroleum contaminated soil, the samples of diesel contaminated soil with different degrees of pollution were prepared manually, and their basic physical properties were tested through the particle test, specific gravity test and liquid plastic limit test. The results show that the diesel oil has a great influence on the particle size composition of soil, and the diesel oil makes the content of silt decrease, while the clay increase obviously; the specific gravity of soil sample decreases with the increase of oil content, and it is smaller than the proportion of unpolluted soil sample; the influence of diesel oil on the liquid-plastic limit of soil is different, the plastic limit of soil decreases with the increase of oil content, and the liquid limit increases first at a certain oil content, it reaches a peak value and then decreases.

Improvement of loess characteristics using sodium alginate

Loess often has poor engineering properties due to its loose accumulation and strong collapsibility. Therefore, improvement of the soil is necessary to meet the needs of engineering. In the current work, the improvement effect of sodium alginate added in different proportions to loess was studied. Limited water content test and particle size grading test were conducted to study the effect of sodium alginate on the basic physical parameters of soil. In addition, unconfined compressive strength test (UCS) and consolidated undrained test (CU) were used to analyze the changes in the mechanical properties of the soil after improvement. Additionally, permeation and disintegration tests were used to study the change in the soil’s water stability. What’s more, the microscopic mechanism of sodium alginate improved loess was also proposed based on the results of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that sodium alginate not only can change the liquid-plastic limit and particle size gradation of loess but also improve the strength, shear parameters, and water stability of loess. SEM and XRD studies revealed that sodium alginate changed the microstructure of the loess, formed a colloidal material to encapsulate the soil particles, filled the pores between soil particles, and caused aggregation of the clay material in the soil to form larger particle size via flocculation. These results show that sodium alginate can be used as a more environmental friendly and sustainable additive to replace the traditional soil stabilization additives, such as cement or lime to stabilize loess.

Experimental study on seismic behaviour of adobe wall reinforced with cold–formed thin–walled steel

Abstract Currently, adobe is one of the building material commonly used in towns and villages. However, the damage of the adobe houses during earthquakes is severe. To reduce the severe damage, this study aimed to improve the seismic behaviour of the rural adobe houses. A series of tests were conducted on the seismic behaviour of the adobe walls. The material property tests were performed on raw materials and the particle size distribution, liquid–plastic limit, optimum moisture content and maximum dry density of soil were analyzed. The mechanical behaviour of the adobe and mud bricks was characterized by conducting the axial compression test. The stress–strain curves of the bricks were analyzed. The elastic modulus was obtained and the relationship between the modulus of elasticity and compressive strength of adobe bricks and mud bricks was established. The quasi–static loading tests were performed on an unreinforced adobe wall and an adobe wall reinforced with 1 mm thick cold–formed thin–wall steel. A comparative analysis of the failure mode, hysteretic performance, stiffness, ductility and energy dissipation capability was performed. Besides, strains at key locations of the reinforced adobe wall were studied. It indicated that the seismic behaviour of the reinforced wall was much better than that of the unreinforced wall. The cracking load, ultimate load, ductility coefficient and energy consumption were increased by 43.34%, 79.10%, 440% and 560%, respectively. The results indicated that the application of cold–formed thin–walled steel enhanced the seismic performance of the adobe wall significantly.

Calculation Methods of Seepage Coefficient for Clay Based on the Permeation Mechanism

The existing empirical methods of the seepage coefficient for clay have difficulty in parameter acquisition and are poor in calculation accuracy, and it is possible to find reasonable ones based on the mature empirical methods of coarse‐grained soil. Firstly, the permeation mechanism of clay was analysed including influencing factors, spatial process, and parameter calculation, and the ineffective and effective voids were defined; then the empirical methods of clay and coarse‐grained soil were summarised and listed. Secondly, clay was put equivalent to coarse‐grained soil according to bound‐water consolidation, and the parameter “equivalent void ratio” was introduced to establish the equivalent calculation methods. Finally, the liquid‐plastic limit method determining the volume of ineffective voids was explained, and the feasibility of equivalent calculation methods was evaluated by three examples. The results show that seepage, permeation, and effective permeation are three different concepts; groundwater permeates in clay via the effective void. For certain soil, the increasing sequence of permeability coefficients is the seepage coefficient, permeation coefficient, and effective permeation coefficient. Introduction of the “equivalent void ratio” unifies the calculation of the seepage coefficient for clay and coarse‐grained soil. The maximum of the bound‐water content is about 0.9 time the size of liquid limit. The Mesri equation and the equivalent calculation method of Terzaghi or Curson–Karman are suitable for calculating the seepage coefficient of clay for the closest results to experimental values.