Mudstone Particle Research Articles

Investigation on the cyclic shear properties of steel-crushed red mudstone particles interface

The cyclic shear characteristics between the structure and soil are critical to the bearing capacity of an infrastructure. In this study, the cyclic shear behavior of the interface between rough steel and crushed red mudstone particles under constant normal load (CNL) and constant normal stiffness (CNS) boundary conditions are investigated using an improved large-scale cyclic shear apparatus. Under the two normal boundary conditions, the variation rule of the interface shear stress with shear displacement is similar, and the interface generally exhibits softening behavior during cyclic shear. Nevertheless, the interface shear strength and deformation values are not equal for the two boundary conditions, i.e., under the CNL boundary condition, higher interface shear strengths are usually obtained, and more significant normal densification behavior is exhibited compared to the CNS boundary condition. The peak shear strength of the interface has a linear relationship with the normal stress, which conforms to the Mohr-Coulomb failure criterion. Additionally, the influence of water content on the interface deformation and cyclic shear strength under the above boundary conditions are explored. The water content does not change the interface volumetric response pattern but is reflected in the magnitude. Regarding interface shear strength, the interface softening phenomenon is more significant with increased water content. The interface shear strength of the initial and residual states is analyzed, while the relationship between the interface shear strength parameters and water content is established.

Effects of nitrogen fertilizers on the bacterial community diversity and the weathering of purple mudstone in Southwest China.

Rock weathering is crucial in the development of soil. Yet the role of bacteria in the fine particle-forming process of purple mudstone is not fully understood, especially under nitrogen fertilization. In this study, the particles (0.25 mm to 1 mm) of purple mudstone from Penglai Group (J3p) were selected as the test material. Two nitrogen fertilizers, i.e., urea (U) and ammonium bicarbonate (AB), and four application levels (0, 280, 560, and 840 N kg∙ha-1) with 18 replications were designed in an incubation experiment. The weathering indices and bacterial community structure of the purple mudstone particles were investigated after 120 days of incubation. The results showed that the weathering indices of purple mudstone particles in the AB treatment were higher than that in the U treatment at the same fertilization levels and a reducing trend was observed with increasing nitrogen fertilizer levels under the same nitrogen fertilizer application types. The diversities of the bacterial community were extremely significantly altered by nitrogen fertilizer application (p < 0.01). The effect of the nitrogen fertilizer application level on the beta diversity of the bacterial community (R2 = 0.34) was greater than that of the nitrogen fertilizer application type (R2 = 0.20). Through stepwise regression analysis, the positive effects of nitrification of Nitrobacter (Nitrolancea) (R2 = 0.36), the Phosphorous-dissolving bacteria (Massilia) (R2 = 0.12), and N-NO3- (R2 = 0.35) on the weathering indices of J3p purple mudstone particles could be observed. Structural equation modelling indicated that nitrogen fertilizer application level affects the abundance of the dominant species at the genus level (Nitrolancea and Massilia), and key environmental factor (N-NO3-), which in turn accelerated the weathering indices (59%). Our findings imply that the enhancements of nitrification of Nitrobacter (Nitrolancea) and of phosphorus solubilization of Phosphorous-dissolving bacteria (Massilia) by nitrogen fertilization are the key factors affecting the weathering indices of J3p purple mudstone particles.

Study on Secondary Brine Drainage and Sand Control Technology of Salt Cavern Gas Storage

Geological conditions of salt cavern gas storage in China are characterized by dominantly layered salt layers with a high content of insoluble mudstone. After the water leaching of the salt layer, a large amount of sediment accumulates at the bottom of the gas storage cavity. During the gas injection process, only the clean brine above the sediment can be expelled, leaving a brine layer of 2–5 m and a large amount of brine in the pore space of the sediment. To increase storage capacity, it is urgent to explore the secondary gas injection and brine drainage technology to further expel residual brine in pores of the sediment at the cavern bottom. The sediment is relatively loosely packed and is composed of mudstone particles, which easily migrate and block the brine withdrawal pipe. In this paper, firstly, the mineral composition, particle size and distribution characteristics of the sediment at the bottom of the salt cavern are fully understood by XRD and sieve analysis methods. Then, a lab simulation device suitable for secondary gas injection and brine drainage of a high-salinity salt cavern with a diameter and height of 25 cm was designed and built. A screen sand control experiment, a gravel pack artificial wall sand control experiment and chemical cementing sand were simulated. The effects of gas injection, brine drainage pressure, brine layer height and insoluble particle size on sand production and liquid drainage were studied. The influence factors of brine withdrawal on the sand control in secondary brine drainage were intensively investigated, and finally, the gravel pack artificial wall sand control technology system was recommended. The optimal construction parameters for secondary brine discharge are recommended as follows: Under the condition of gravel packing with the same particle size, the trend of sand content with different artificial wall thicknesses is not obvious, and a 2 cm wall thickness is the best in the overall experiment, corresponding to 28 cm in the field. The larger the particle size of the gravel pack, the better the sand control, and the best gravel size is 10–20 mesh. The injection pressure should be as low as possible.

Laboratory test and prediction model of dynamic resilient modulus of carbonaceous mudstone coarse-grained soil

Carbonaceous mudstone is widely distributed in southwest China. With the rapid development of transportation construction in this region, the use of carbonaceous mudstone for subgrade filling has good economic and environmental benefits. At present, studies on the dynamic characteristics of carbonaceous mudstone coarse-grained soil are few. The shape characteristics of mudstone particles and the compaction characteristics of subgrade fillings with different grades are analyzed then dynamic triaxial tests are conducted to explore the variation of the dynamic resilient modulus MR of carbonaceous mudstone coarse-grained soil under different stresses and physical states. The influence of different gradation, confining pressure σ3, dynamic deviatoric stress σd, moisture content w, and degree of compaction K on MR of carbonaceous mudstone coarse-grained soil was studied. Results indicate that the particle shape index of carbonaceous mudstone is insensitive to particle size. With the increase in the gradation parameter D, the optimal moisture content wopt of the sample increases, whereas the maximum dry density ρdmax initially increases, and then decreases. MR is positively correlated with σ3 and K, but negatively correlated with σd and w. The decrease of MR caused by w decreases gradually with the increase of D. When w≤ 1.1 *wopt, the increase in D reduces MR, but when w= 1.2 *wopt, the trend changes to a positive correlation between MR and D. Carbonaceous mudstone subgrade filling can be used for the highway with light or medium traffic load grade. The recommended gradation parameter D ranges from 2.43 to 2.63. A resilient modulus prediction model considering the influence of gradation, stress state, moisture content, and physical state is proposed and its rationality is verified. The research results can provide reference for the design of carbonaceous mudstone coarse-grained soil subgrade.

Effect of dry-wet cycles on dynamic mechanic and microstructure of cemented broken mudstone

The secondary utilization of abandoned mine is usually accompanied by water erosion, cyclic impact, and induced earthquake, which induces a great engineering challenge for the mudstone stratum reconstruction. Consequently, this paper carried out ultrasonic detection, split Hopkinson pressure bar (SHPB) impact, thermogravimetry, and mercury intrusion porosimetry tests to investigate the dynamic performance and microstructure of reinforcing mudstone under water erosion. The results show that the dynamic compression strength (DCS) and strain-rate enhancement effect of cemented broken mudstone (CBM) firstly increase and then decrease with the increase of dry-wet cycles, the maximum growth is 15.38% for CBM in 3 dry-wet cycles while the maximum drop is 19.63% for that in 9 dry-wet cycles. The dry-wet cycles mainly affect the DCS by changing the elastic limit strength, and promote the carbonization of Ca(OH)2 to produce up to 9.365% CaCO3 during the cemented matrix’s hydration. In the late dry-wet stage, the deterioration of internal mudstone particles induces pore cracks and causes up to 19.63% decrease in DCS. This study reveals the evolution law of dynamic mechanical properties of CBM under water erosion, and provides experimental reference for the reconstruction of abandoned mine.

Particle size distribution analysis of mudstone based on digital image processing

Mudstone is becoming increasingly important for unconventional oil and gas development. The morphological characteristics of clastic are not only contributions to the 3D framework of mudstone, but they can clearly affect the physical properties of a mudstone reservoir, including surface area, pore-size distribution, and porosity. However, it is very difficult and time-consuming to measure the particle size distribution (PSD) of mudstone because of its small particle size and strong cementation. However, because of the importance of oil and gas extraction, it is urgent to develop a fast, accurate, and objective analysis method to measure the PSD of mudstone. Based on a comparison of various PSD measurement methods commonly used in the energy industry and geology, the best PSD measurement method for mudstone should be digital image processing. Two imaging methods, trainable Weka segmentation (TWS) and black mudstone particle size measurement, were used to analyze sections of the early Silurian Longmaxi mudstone of China’s Sichuan Basin. The PSD data obtained by manual measurement, TWS, and the contribution method are compared. Image analysis finds that the particle sizes of all samples fall in the range of coarse silt to clay, and the average sizes fall in the range of coarse silt to fine silt. The skewness, kurtosis, standard deviation, and other distribution characteristics parameters find minor errors, and the relative error is less than 15%. The Pearson correlation coefficient of the 10th quantile of TWS, black mudstone particle size measure, and manual measurement were calculated, which found R2 values typically ranging between 0.64 and 0.87. Kolmogorov-Smirnov test results find that the data obtained by the three measurement methods are from the same distribution at the level of 0.05. Analytic results find that the method presented is effective, cost-efficient, and could avoid artificial errors.

Erosion Effect on Non-Darcy Hydraulic Characteristics of Limestone and Mudstone Mixture

In order to study the water inrush mechanism of faulted rock mass, a series of erosion seepage experiments were carried out to test the non-Darcy hydraulic properties of a limestone and mudstone mixture. The test results are employed to verify and modify a classic permeability prediction model. Based on the evolution of mass loss rate, the erosion process can be divided into four stages, i.e., particle rearrangement, severe erosion, mild erosion, and stable seepage. During the erosion, the sample height decreases gradually, the water pressure at outlet grows first and then keeps stable, and the porosity and permeability decrease slightly first, then grow gradually and finally keep stable. The hydraulic properties show a more significant variation in the sample within high mudstone particle contents. Through the comparison of test results and the predicted results by the classic Carman-Kozeny model, it is found that the accuracy of the model is greatly affected by lithology. Based on this investigation, a revised model is proposed which introduces a proportional coefficient related to the rock composition, so as to increase the predicted precision in variable rock composition. The forecast accuracy of the revised model is much higher than the classical one in permeability although it decreases with the increase of mudstone content.

Experimental Investigation into Cyclic Shear Behaviors in the Interface Between Steel and Crushed Mudstone Particles

In the waterway construction projects of the upper streams of the Yangtze River, crushed mudstone particles are widely used to backfill the foundations of the rock-socketed concrete-filled steel tube (RSCFST) pile. The mudstone particles are prone to being crushed, which influences the mechanical properties of the soil and the interface between the soil and the steel cased on the RSCFST pile. The crushing of the particles will be aggravated by reciprocating shear of the interface when the pile experiences repeating lateral loads. The reciprocating shear of the interface may, therefore, weaken the bearing capacity of the pile. In this study, we develop a new apparatus to study the mechanical properties of the steel–soil interface under a reciprocating shear condition. With this apparatus, a set of large-scale direct shear experiments are carried out with two different boundary conditions, that is, a constant stress boundary and a constant stiffness boundary, respectively. Comparative experiments and parallel experiments are carried out to study the physical properties of steel–mudstone particle interface and the stability of the apparatus. Parallel experiments show that the instrument has good stability. The comparative experiment results also reveal the differences of the shear behaviors of the interface under two conditions. Analysis of the experiment results shows that the normal stiffness condition is closer to the real boundary condition when the soil–steel interface is cyclically sheared. The particle crushing and the attenuation of normal stress is the main reason causing the degrading of the interface.

Erosion Effect on Non-Darcy Hydraulic Characteristics of Limestone and Mudstone Mixture

In order to study the water inrush mechanism of faulted rock mass, a series of erosion seepage experiments were carried out to test the non-Darcy hydraulic properties of a limestone and mudstone mixture. The test results are employed to verify and modify a classic permeability prediction model. Based on the evolution of mass loss rate, the erosion process can be divided into four stages, i.e., particle rearrangement, severe erosion, mild erosion, and stable seepage. During the erosion, the sample height decreases gradually, the water pressure at outlet grows first and then keeps stable, and the porosity and permeability decrease slightly first, then grow gradually and finally keep stable. The hydraulic properties show a more significant variation in the sample within high mudstone particle contents. Through the comparison of test results and the predicted results by the classic Carman-Kozeny model, it is found that the accuracy of the model is greatly affected by lithology. Based on this investigation, a revised model is proposed which introduces a proportional coefficient related to the rock composition, so as to increase the predicted precision in variable rock composition. The forecast accuracy of the revised model is much higher than the classical one in permeability although it decreases with the increase of mudstone content.

Characteristics of Heavy Metal Ion Adsorption by Silty Mudstones in Coal Mine Goafs

Coal mine goafs can be used to store and purify mine water; therefore, they are important for mitigating the environmental impact of mining on ecologically fragile areas in Western China. Coal gangue in goafs can reduce turbidity, suspended matter, total hardness, and chemical oxygen demand (COD) in mine wastewater. Because gangue in goaf areas is rich in clay minerals, they serve as ion exchange sites. We investigated the adsorption of heavy metal ions by silty mudstones in the Ulan Mulun mine. The adsorption kinetics and isothermal adsorption characteristics of four heavy metal ions, i.e., Pb(II), Cd(II), Cr(III), and Mn(II), were investigated using batch experiments. Under a pH of 6.75 and temperature of 20°C, the adsorption capacity of silty mudstone particles (&lt;74 μm) was 6.3012 g, 1.5701, 1.2571, and 1.3729 mg/g for Pb(II), Cd(II), Cr(III), and Mn(II), respectively. Based on the experimental results, quantitative relationships between the adsorption quantity per unit of rock surface and the equilibrium concentration of heavy metals in solution were developed using Langmuir, Freundlich, and D–R equations. The relationships were used to obtain the equilibrium concentration of the solution. Finally, the ratio of the f value of the water-rock contact area in the goaf to the water volume was calculated and analyzed. The f value was inversely proportional to the average vertical opening of gaps between gangues in the goaf. The adsorption rate functions for Pb(II), Cd(II), Cr(III), and Mn(II) in the goaf were obtained, and the corresponding adsorption capacities were calculated. The adsorption capacities were controlled by the f value and adsorption properties of the gangue. These results can be used in future studies on mine wastewater treatment.

Failure Mechanism of Horizontal Layered Rock Slope under the Coupling of Earthquake and Weathering

In order to further reveal the dynamic failure process of horizontal complex layered rock slope in the coupling action of earthquake and weathering, based on the three‐dimensional particle flow software PFC3D, the rock triaxial test was first carried out to obtain the macroscopic rock mechanics parameters. Secondly, PFC3D was used to establish a three‐dimensional discrete element model of slope under 4 modes. Finally, the Wenchuan earthquake wave dynamic input is used to simulate the coupling effect of each model slope on earthquake‐weathering. Under the progressive failure process, the results show that, during the triaxial test, the mudstone particles and sandstone particles exhibited shear failure and tensile failure, respectively. The seismic failure mode of the horizontal complex layered rock slope model is divided into tensile fracture‐horizontal sliding failure (cavity depth 1.5 m and fissure depth 25%), tensile cracking‐caving‐dumping failure (cavity depth 3 m and fissure depth 37.5%), caving‐dumping‐rotation failure (cavity depth 4.5 m and fissure depth 50%), and caving‐slip‐rotation failure (cavity depth 6 m and fissure depth 62.5%), and the maximum vertical displacement of Model 2 can reach 6.2 m, and the maximum positive horizontal displacement is 7.8 m. With the deepening of the weathering degree, the coordination number of the rock block shows the attenuation advance effect and the elevation attenuation effect during the seismic period of 2–15 s. The total energy dissipation of the slope can be divided into two stages: fracture collision and overall collapse. The energy dissipation is more concentrated in the rock fracture collision stage, accounting for 89% to 95% of the total energy.

Effects of periodic saturation on K0 for a sandstone-mudstone particle mixture

Sandstone-mudstone particle mixture (SMPM) is one of the main materials, which has been widely used for filling in and around reservoirs for water conservation projects. During the periodic rising and falling of the water level, the fill material for the embankments, dam, and other waterfront features will also undergo drainage-saturation cycles. The deformation and coefficient of lateral pressure at rest K0 may be affected by periodic saturation. In this study, a device is modified for testing the K0 for gravel-soil under periodic saturation. In order to investigate the effects of periodic saturation on K0, a series of experiments were performed for SMPM under different vertical stress and saturation cycling. K0N values of SMPM containing 20% mudstone particles under periodic saturation were obtained. The results shows that the K0N initially increased, but eventually reached a stable value with the increasing number of periodic saturation cycles. The magnitude of the coefficient increment was also found to be related to the stress condition. K0N is a logarithmic function of the saturation cycling time. By calculating K0N with the proposed empirical formula, the deformation and stress distribution of the SMPM filler in waterfront engineering works can be calculated with greater precision.

Effects of Wet–Dry Cycle on the Shear Strength of a Sandstone–Mudstone Particle Mixture

Shear strength of a sandstone–mudstone particle mixture, filled along the bank of a large reservoir and subjected to wet–dry cycle induced by the rise–lower cycle of water level, may be affected by the wet–dry cycle. To investigate the effects, two-type triaxial tests, without and with the wet–dry cycle, were carried out. The experimental data indicate that the shear strength, denoted by peak deviator stress (σ1 − σ3)f, angle of shearing resistance φ, nonlinear shear strength indicators φ0 and φd, or linear shear strength indicators φ* and c, is reduced by the wet–dry cycle. With the increment of cycle from 1 to 20, the decrement of shear strength, denoted by the parameters mentioned above, is increasing in a logarithmic relationship. Furthermore, the effect is also related to the confining pressure and stress level selected in the tests. Based on analyzing experimental data, several logarithmic functions, used to predict the shear strength of the mixture after the wet–dry cycle, were suggested. Due to the effect of the wet–dry cycle, stability of a slope, filled in waterfront conditions using the mixture, is reduced.

A promising SPEEK/MCM composite membrane for highly efficient vanadium redox flow battery

A novel composite membrane blended the sulfonated poly (ether ether ketone) (SPEEK) with modified carbonaceous mudstone (SPEEK/MCM) has been developed for vanadium redox flow battery (VRB). Using a strong acidification treatment, a large amount of hydrophilic oxygen functional groups was introduced on the modified carbonaceous mudstone (MCM) particles, which has been evidenced to enhance the proton conductivity. It is found that the MCM particles help to retard the permeation of vanadium ions through the membrane. With these merits, the VRB single cell based on our novel SPEEK/MCM membrane exhibits outstanding device performance. Notably, the coulombic efficiency (CE) of the cell is as high as more than 99% and the per-cycle capacity loss is only 0.15% under a high current density of 120 mA cm−2. Our work provides a simple method to prepare low cost and high-performance membranes for VRB. More importantly, the SPEEK/MCM membrane has promising potential in other battery applications.

Rheological Behavior and Modeling of a Crushed Sandstone-Mudstone Particle Mixture

A mixture of sandstone and mudstone particles is often used as the main filling material for many agriculture-related and civil engineering projects, including rock-fill dams and foundations. The long-term rheological deformation experienced by rock-fill dams and foundations filled with this mixture is much bigger than that of coarse-grained and cohesive soils, due to the deterioration and softening of the mudstone particles. This study focuses on the rheological deformation of a sandstone-mudstone particle mixture, prepared by mixing sandstone and mudstone particles, based on the content by weight of four mudstone particle types. Confined uniaxial compression tests were performed to test the rheological deformation of 24 samples of the mixture, and a stress-strain curve was obtained for each test. On the basis of compression curves, the rheological process of the mixture was divided into four phases: linear, attenuation rheological, secondary attenuation rheological and stable phases. The three defining features of the curve, namely the rheological attenuation factors, attenuation rheology critical strain and limited rheological strain, were then determined and modeled. A segmented rheological model was then proposed, based on a modified attenuation rheological constitutive model for coarse-grained soil. The modelled results compared well with the experimental data, and the modelled compression-curve prediction was able to describe the two-stage attenuation rheology features (attenuation rheological and secondary attenuation rheological phases) of the sandstone-mudstone particle mixture.

Shear strength of sandstone–mudstone particle mixture from direct shear test

The mixture mixed by crushed sandstone and mudstone particles are gradually used as a kind of fillers in geotechnical engineering. However, the engineering practice goes ahead of the theory, the engineering features of this particle mixture have not been well revealed. Based on series of direct shear tests in laboratory, shear strength of the sandstone–mudstone particle mixture and its influencing factors are investigated in this paper. The curves of nominal shear stress against relative lateral displacement for test materials are obtained. Particle size distribution, mudstone particle content of experimental materials, initial dry bulk density and water content of test specimens are listed as four important influencing factors and they are carefully analyzed with single factor analysis method. The rule of the four important factors influencing on the engineering features of this particle mixture are derived, respectively. The experimental results can be used as a reference for this kind of filling project. The conclusion of this paper is beneficial to the popularization and application of the mixture with crushed sandstone and mudstone particles.

Wetting-induced axial and volumetric strains of a sandstone mudstone particle mixture

ABSTRACTIn this study, the deformation induced by the first wetting typically referred to as wetting deformation of a sandstone–mudstone particle mixture is examined. Wetting deformation can lead to collapse-inducing cracks. The cracks may weaken the strength of the structure. To investigate the first wetting-induced deformation of the sandstone and mudstone particle mixture, three triaxial tests were conducted. Two of the triaxial tests used saturated soil and dry soil. These tests were used to calculate the strain under the condition of minimized deviator stress ratio at wetting. The third triaxial test accesses various deviator stress ratios at wetting. Additionally, the influence on axial and volumetric strain of wetting at varying levels of the confining stress and deviator stress ratios at wetting was evaluated. The wetting axial and volumetric strains were found to increase with an increased confining stress and deviator stress ratio at wetting. The relationships between the wetting axial strain and deviator stress ratio at wetting yielded a logarithmic curve for various levels of confining stress. In contrast, the wetting volumetric strain yielded a direct relationship with the deviator stress ratio at wetting for various levels of confining stress. Based on these results, two equations for predicting the wetting axial and volumetric strains are suggested.

Experimental Investigation on Hydraulic Properties of Granular Sandstone and Mudstone Mixtures

The caved zone during longwall mining has high permeability, resulting in a mass of groundwater storage which causes a threat of groundwater inrush hazard to the safe mining. To investigate the hazard mechanism of granular sandstone and mudstone mixture (SMM) in caved zone, this paper presents an experimental study on the effect of sandstone particle (SP) and mudstone particle (MP) weight ratio on the non-Darcy hydraulic properties evolution. A self-designed granular rock seepage experimental equipment has been applied to conduct the experiments. The variation of particle size distribution was induced by loading and water seepage during the test, which indicated that the particle crushing and erosion properties of mudstone were higher than those of sandstone. Porosity evolution of SMM was strongly influenced by loading (sample height) and SP/MP weight ratio. The sample with higher sample height and higher weight ratio of SP achieved higher porosity value. In particular, a non-Darcy equation, for hydraulic properties (permeability κ and non-Darcy coefficient ζ) calculation, was sufficient to fit the relation between the hydraulic gradient and seepage velocity. The test results indicated that, due to the absence and narrowing of fracture and void during loading, the permeability κ decreases and the non-Darcy coefficient ζ increases. The variation of the hydraulic properties of the sample within the same particle size and SP/MP weight ratio indicated that groundwater inrush hazard showed a higher probability of occurrence in sandstone strata and crushed zone (e.g., faults). Moreover, isolated fractures and voids were able to achieve the changeover from self-extension to interconnection at the last loading stage, which caused the fluctuation tendency of κ and ζ. Fluctuation ability in mudstone was higher than that in sandstone. The performance of an empirical model was also investigated for the non-Darcy hydraulic properties evolution prediction of crushing and seepage processes. The predictive results indicated that particle crushing and water erosion caused the increase of hydraulic properties, being the main reason that the experimental values are typically higher than those obtained from the predictive model. The empirical model has a high degree of predictive accuracy; however, κ has a higher predictive accuracy than ζ. Furthermore, the predictive accuracy of κ increases and ζ decreases with increasing weight ratio of SP.

Effect of Particle Size Distribution on Soil-Steel Interface Shear Behavior

The performance of rock-socketed concrete-filled steel tube piles is strongly dependent on the shear behavior of the interface between the steel and the surrounding soil. The effects of particle size distribution (PSD) on soil-steel interface shear behavior were investigated for a soil mixture composed of crushed sandstone and mudstone particles. Tests were conducted using a strain-controlled direct shearing apparatus. The results showed nonlinear relationships between the shear strain and the stress and revealed dilation of the specimens during the shearing process. The shear strength of the interface was found to be linearly related to the normal stress, obeying the Mohr-Coulomb criterion. Relationships between the shear strength parameters and PSDs were established. In combination with fractal theory, these were used to assess the variation of interface shear strength and the disintegration of particles in shear processes. With knowledge of the variation of the fractal dimensions of the PSD, an approach for evaluating the evolution of interface shear strength parameters was proposed based on the effect of PSD on shear behavior.

Closure to “anisotropic hydraulic conductivity and critical hydraulic gradient of a crushed sandstone–mudstone particle mixture”

ABSTRACTA closure is presented to the discussion of Anisotropic hydraulic conductivity and critical hydraulic gradient of a crushed sandstone–mudstone particle mixture by Salahou, Jiao, and Yousif (2017). The relationship between the critical hydraulic gradient and the uniformity coefficient can be limited to two curves. The internal erosion mechanism of soils with different particle grade curves is different. The maximum diameter of fine particles of different particle grade curves can be calculated by a lot of methods. The density of the original paper is the average density. The anisotropic hydraulic conductivity is caused by uneven density distribution. The hydraulic conductivities are tested on the saturated soils. The saturated hydraulic conductivity can be regard as a constant value for a saturated soil.