Sandstone Mudstone Particle Mixture Research Articles

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.

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.

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.

Deformation of a sandstone–mudstone particle mixture induced by periodic saturation

ABSTRACTThis study focuses on the evaluation on deformation induced by periodic saturation of a sandstone–mudstone particle mixture. Two types of triaxial tests, without and with periodic saturation, were performed. The strain–stress relationships from the two types of tests indicate that the periodic saturation may induce an increment of axial strain (Δε), and the Δε values are related to the ratio of confining to atmospheric pressure (σ3/pa), stress level for periodic saturation (L), and number of periodic saturation or cycles (N). The values of Δε are increasing along logarithmic curves with increment of N value from 1 to 20, and increase along straight lines with increasing L value from 0.18 to 0.82 or σ3/pa value from 1 to 4. Based on the analyses of experimental data, a logarithmic fitting equation, which is a function of N, L, and σ3/pa, is suggested to predict the Δε value. And based on the fitting equation and simple analyses on stress state, another equation, which may be used to estimate the settlement induced by periodic saturation of a large-area foundation filled using the sandstone–mudstone particle mixture, is also suggested.

Discussion of (anisotropic hydraulic conductivity and critical hydraulic gradient of a crushed sandstone–mudstone particle mixture)

ABSTRACTA discussion is presented here to the work of Wang and Qiu including some notes about the analysis and the correlations of the results. First, we show that there is no clear relationship between the critical hydraulic gradient and the uniformity coefficient. Also we show that the internal erosion mechanism of soils with bimodal structure is different from that for soils with no bimodal structure. Finally, we emphasis that the anisotropy in the hydraulic conductivity is not related to the uneven compaction only but also to the particle arrangements and connectivity between pores.

Experimental study on interaction between compressibility and permeability of a crushed sandstone–mudstone particle mixture

ABSTRACTThe present study focuses on the compressibility and permeability characteristics of a crushed sandstone–mudstone particle mixture (SMPM). Two type of laboratory tests, which are compressibility–permeability test (CPT) and compressibility test only (CTO), are performed. Based on the test data, the effects of the seepage action on the compressibility and ones of the void ratio (e) on the permeability are analyzed. The rate of consolidation of the crushed SMPM is also discussed. The values of compressibility index (Cc) obtained from the CPT are greater about 1.32–4.81% than ones obtained from the CTO, but the values of preconsolidation stress (σp) obtained from the CPT are smaller about 2.34–9.83% than ones obtained from the CTO. The slope of fitting line of e∼logK (where K is the coefficient of permeability, and log is the logarithm to base 10), defined as the permeability index (Kc), ranges from 0.146 to 0.337 with an average of 0.226. The value of Cc/Kc, used to evaluate the rate of consolidation, ranges from 0.905 to 1.250 with an average of 1.031. The rate of consolidation of the crushed SMPM may be analyzed by Terzaghi’s theory due to the average value of Cc/Kc very close to 1.0.

Compression characteristics of an artificially mixed soil from confined uniaxial compression tests

The present study focuses on the compression characteristics of a crushed sandstone–mudstone particle mixture. The mixture is artificially prepared by mixing sandstone particles and mudstone particles (MP) on the basis of five scheduled particle size distribution (PSD) curves and six MP contents by weight. In order to investigate the compression characteristics, 120 confined uniaxial compression tests are performed. The compression curve for each specimen, which represents the relationship between the logarithm (base 10) of the applied stress and void ratio, is obtained from test data. Two defining features of the compression curve, namely the compression index (I c) and pre-compression stress (σ p), are determined. The effects of two-type factors on the two parameters I c and σ p are analyzed. Factors of the first type are the properties of tested material, which include the PSD curve [the characteristics of which are denoted by the median particle diameter (D 50), gravel content (G c), non-uniformity coefficient (C u), curvature coefficient (C c), characteristic size (α), PSD shape (β)], and MP content by weight (MPc). Factors of the other type are the properties of the specimen, which include the initial water content (w), initial dry bulk density (ρ d), and initial void ratio (e 0). The results indicate that both the parameters I c and σ p are correlative with the properties of the tested material and specimen.

Anisotropic hydraulic conductivity and critical hydraulic gradient of a crushed sandstone–mudstone particle mixture

ABSTRACTThis paper describes the development of a modified instrument used to measure the anisotropic hydraulic conductivity of coarse soils. Then, based on this modified instrument, horizontal and vertical hydraulic conductivities and critical hydraulic gradients of a crushed sandstone–mudstone particle mixture are measured. Using this data, we investigate the effects of particle size on the anisotropic hydraulic conductivity. The testing results indicate that the anisotropic hydraulic conductivity coefficient, which is defined as the logarithm value of the ratio of the horizontal hydraulic conductivity to the vertical conductivity, ranges from 0.079 to 0.358. This means the horizontal hydraulic conductivity is 1.20 to 2.28 times to that of the vertical conductivity. The anisotropic coefficient decreases as the uniformity coefficient increases. Meanwhile, the critical hydraulic gradient increases with an increase in fine particle content.

Experimental Study on the Anisotropic Hydraulic Conductivity of a Sandstone–Mudstone Particle Mixture

AbstractThis study focuses on the anisotropic hydraulic conductivity of a sandstone–mudstone particle mixture. Permeameter tests were performed in the laboratory. The effects of the mixture’s dry bulk density and mudstone particle content on its anisotropic hydraulic conductivity were investigated accordingly. Both the horizontal and vertical hydraulic conductivities were compared based on the calculation results from empirical grain-size formulas and tests. The best predictive formula for the hydraulic conductivities was found to be the Terzaghi empirical formula. It was found that the average horizontal hydraulic conductivity is about 2.0 times more than that of the vertical one. The anisotropy ratio initially increases and then decreases with the increase of the mudstone particle content by weight. A maximum ratio of 2.946 was obtained when the mudstone particle content reached about 60% by weight.

Effects of particle size on compaction behavior and particle crushing of crushed sandstone–mudstone particle mixture

The compaction behavior and particle crushing during compaction of the crushed sandstone–mudstone particle mixture, which is used as a filling material, are investigated in the present study. The value of the maximum dry density, deduced from a standard compaction test, ranges from 2.08 to 2.13 g/cm3, and that of the optimum moisture content from 8.18 to 10.62 %. The value of the maximum dry density increases, then decreases with the increment of the median particle diameter and gravel content. But the value of the optimum moisture content decreases, then increases with the increment of the median particle diameter or gravel content. The value of the average relative breakage ranges from 0.09 to 0.30, and it increases with the increment of the median particle diameter and gravel content. Compared to the mixture of sandstone particles only with the same grain size distribution curves, the mudstone particles mixed into sandstone particles may slightly increase the maximum dry density and decrease the amount of particle crushing.

Shear Strength of a Crushed Sandstone-Mudstone Particle Mixture

The present study focuses on the shear strength of a crushed sandstone-mudstone particle mixture. The mixture is widely used as a main filling material in many geotechnical engineering works. In order to investigate the shear strength of the mixture, triaxial tests under different confining pressures in laboratory are performed for 108 specimens with different dry densities and water contents. The dry density of the specimens ranges from 1.80 to 2.10 g/cm3, and the water content from 4.00 to 9.00 % and to saturation. In the tests, four confining pressures, which are 100, 200, 300 and 400 kPa, are applied. The testing results indicate that the angle of shearing resistance of the mixture in unsaturated state ranges from 16.90 to 32.98°. The angle of shearing resistance is generally decreasing with the increase of the confining pressure. With the increase of the dry density, the angle of shearing resistance increases. The angle is generally increasing then decreases as a parabola with the increase of the water content. The wetting may decrease the value of the angle about 0.4 to 2.7°.

Effects of Mudstone Particle Content on Shear Strength of a Crushed Sandstone–Mudstone Particle Mixture

The present study focuses on the shear strength, deformation, and particle crushing of sand which is mixed by crushed sandstone and mudstone particles. Two triaxial tests—one for unsaturated specimens and the other for saturated specimens—were performed, along with sieve analysis tests. Results obtained from the triaxial tests indicate that, with the increment of the mudstone particle content by weight, the angle of internal friction decreases, the cohesion increases and then decreases, and both the initial angle of shearing resistance at the atmospheric pressure and decremental angle increase and then decrease. Compared to the unsaturated specimens, the deviator stress or normalized deviator stress of the saturated specimens at the same axial stress may decrease due to the wetting action. Thus, the shear strength of the tested materials may be reduced by the wetting action. Results of sieve analysis tests indicate that the mixing of some mudstone particles into the sandstone particle mixture may reduce the amount of particle crushing, but the wetting action may increase the amount. The amount of the crushed particle may arrive at a minimum of 40% of mudstone particle content by weight.

Effects of Compaction Effort on Compaction Behavior and Particle Crushing of a Crushed Sandstone-Mudstone Particle Mixture

The present study focuses on the effects of compaction effort on the compaction behavior and particle crushing of a mixture of crushed sandstone particles and mudstone particles. Compaction tests under five different compaction efforts on the mixture were performed. Testing results indicate that the values of the maximum dry density and the average relative breakage of the mixture are nonlinearly increasing with the increase of the compaction effort, but the variation of the optimum moisture content is independent of the increase of the effort. Compared to a crushed sandstone particle mixture with the same grain size distribution and the same compaction effort, the maximum dry density of the crushed sandstone-mudstone particle mixture may be increased, the optimum moisture content reduced, and the average relative breakage during compaction reduced too, by the mixing of a small quantity of mudstone particles.

Effects of mudstone particle content on compaction behavior and particle crushing of a crushed sandstone–mudstone particle mixture

The present study focuses on the compaction behavior and particle crushing, during the compaction, of a crushed sandstone–mudstone particle mixture. Compaction tests and sieve analysis tests, in laboratory, were performed. The effects of the mudstone particle content, by weight, on the maximum dry density, the optimum moisture content and the average relative breakage were analyzed. Testing results indicate that the values of the maximum dry density and the optimum moisture content of the mixture are increasing then decreases with the increase of the mudstone particle content. While the mudstone particle content is about 60%, the maximum dry density is near its maximum. The average relative breakage, during the compaction, is decreasing quickly then increases slowly with the increase of the mudstone particle content. While the mudstone particle content is about 40%, the average relative breakage is near its minimum. Compared to those of a crushed sandstone particle mixture, the maximum dry density of the crushed sandstone–mudstone particle mixture is greater, and the average relative breakage, during the compaction, is smaller.