scholarly journals Effect of Cement Content on the Deformation Properties of Cemented Sand and Gravel Material

2019 ◽  
Vol 9 (11) ◽  
pp. 2369 ◽  
Author(s):  
Jie Yang ◽  
Xin Cai ◽  
Xing-Wen Guo ◽  
Jin-Lei Zhao
Keyword(s):  
Cement Content ◽  
Axial Strain ◽  
Constitutive Models ◽  
Volumetric Strain ◽  
Prediction Method ◽  
Confining Pressure ◽  
Cemented Sand ◽  
Initial Modulus ◽  
Deformation Properties ◽  
Sand And Gravel

Knowing the deformation properties of cemented sand and gravel (CSG) material can help construct reasonable constitutive models for the material, which can be used to simulate the structural performance of various practical projects including CSG dams. In this study, to investigate the effect of cement content on the deformation properties of CSG material, we employ triaxial compressive tests for cement contents of 20, 40, 60, 80, and 100 kg/m3 with a confining pressure range of 0.3–1.2 MPa, and theoretically analyze the results by the regression analysis prediction method. Here, we show that both cement content and confining pressure influence the deformation properties of CSG material: for an increase in cement content, the failure strain decreases and brittleness of CSG material increases; the initial modulus of the CSG material increased exponentially with increasing cement content or confining pressure; the peak volumetric strain and its corresponding axial strain increase linearly with increasing confining pressures, which decrease with increasing cement content; the initial tangent volumetric ratio can also be determined by the peak volumetric strain and its corresponding axial strain.

scholarly journals Unified Failure Strength Criterion for Terrace Slope Reinforcement Materials

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xuan Fang ◽  
Jie Yang ◽  
Jia-Ming Na ◽  
Zhen-Yuan Gu
Keyword(s):  
Cement Content ◽  
Strength Criterion ◽  
Confining Pressure ◽  
Material Strength ◽  
Failure Strength ◽  
Stability Calculation ◽  
Cemented Sand ◽  
Slope Reinforcement ◽  
Rate Of Increase ◽  
Sand And Gravel

This paper presents a study on the failure strength criterion of terrace slope reinforcement materials, such as lean cemented sand and gravel (LCSG) material, under a triaxial stress state. Cement content and confining pressure were selected as major factors to investigate their influence on the peak stress of terrace slope reinforcement materials based on experimental results and data from the literature. The mechanical properties of the LCSG samples, with cement contents of 60, 80, and 90 kg/m3, and noncemented sand and gravel materials were tested under four confining pressure levels (namely, 300, 600, 1000, and 1500 kPa). The results show that the strength of LCSG material improves as the confining pressure increases. When the confining pressure exceeds 1200 kPa, the rate of increase of the strength for LCSG material and other cemented grained materials declines generally. The material strength displays a linear increase with the growth of the cement content. When the axial load rises up to a certain value, damage will occur at the particle cemented site near the shear plane, and the resistance stress generated by the cementation shows a trend of growth first and then attenuation, and concurrently, the friction between particles increases by degrees. Based on the identified strength characteristics of LCSG material under different cement contents and confining pressures, a new strength criterion that incorporates the frictional strengths and the cementing strengths is proposed for LCSG and other similar materials. The results of this work can provide an important theoretical basis for the stability calculation of terrace slopes and LCSG dams.

scholarly journals Experimental Study on Mechanical Behavior of Lean Cemented Sand and Gravel Material in Unloading and Reloading Paths

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jie Yang ◽  
An-yu Yang ◽  
Yan-gong Shan ◽  
Miao-miao Yang ◽  
Jin-lei Zhao ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Hysteresis Loop ◽  
Triaxial Test ◽  
Volumetric Strain ◽  
Rate Of Change ◽  
Coarse Grained ◽  
Triaxial Tests ◽  
Water Drainage ◽  
Cemented Sand ◽  
Sand And Gravel

Lean cemented sand and gravel (LCSG) materials are subjected to unloading-loading when an LCSG dam is opened for water drainage and then refilled or a roadbed base is subjected to repeated wheel loads. To investigate the behavior of the LCSG materials under loading-unloading, previous studies utilized the complete loading triaxial test. In contrast, in this study, the consolidated drained triaxial tests in the unloading and reloading paths for materials with cementing agent contents of 60 and 100 kg/m3 under different confining pressures, for which each curve generates three loading-unloading cycles, were applied to investigate the unloading and reloading mechanical behavior. Experimental results indicated that the unloading and reloading behavior of the LCSG materials produced stress-strain curves exhibiting a crescent-shaped hysteresis loop, which differs from that exhibited by coarse-grained soil. Although the shape of the crescent-like hysteresis loop was preserved as stress levels increasing, it gradually expanded. Compared with that of the typical triaxial test, the cohesive force and the increasing internal friction angle increased. Further, as the confining pressure increased, the crescent-like hysteresis loops tapered, shear strength increased linearly, and the modulus of resilience increased nonlinearly; the latter’s rate of change, however, decreased. The change in volumetric strain was small during unloading as the stress level changed.

scholarly journals A Strain-Based Percolation Model and Triaxial Tests to Investigate the Evolution of Permeability and Critical Dilatancy Behavior of Coal

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 127 ◽  
Author(s):  
Dongjie Xue ◽  
Jie Zhou ◽  
Yintong Liu ◽  
Sishuai Zhang
Keyword(s):  
Axial Strain ◽  
Triaxial Compression ◽  
Sudden Change ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Percolation Model ◽  
Triaxial Tests ◽  
Transition Behavior ◽  
Orthogonal Experiments ◽  
Stress Dependent

Modeling the coupled evolution of strain and CH4 seepage under conventional triaxial compression is the key to understanding enhanced permeability in coal. An abrupt transition of gas-stress coupled behavior at the dilatancy boundary is studied by the strain-based percolation model. Based on orthogonal experiments of triaxial stress with CH4 seepage, a complete stress-strain relationship and the corresponding evolution of volumetric strain and permeability are obtained. At the dilatant boundary of volumetric strain, modeling of stress-dependent permeability is ineffective when considering the effective deviatoric stress influenced by confining pressure and pore pressure. The computed tomography (CT) analysis shows that coal can be a continuous medium of pore-based structure before the dilatant boundary, but a discontinuous medium of fracture-based structure. The multiscale pore structure geometry dominates the mechanical behavior transition and the sudden change in CH4 seepage. By the volume-covering method proposed, the linear relationship between the fractal dimension and porosity indicates that the multiscale network can be a fractal percolation structure. A percolation model of connectivity by the axial strain-permeability relationship is proposed to explain the transition behavior of volumetric strain and CH4 seepage. The volumetric strain on permeability is illustrated by axial strain controlling the trend of transition behavior and radical strain controlling the shift of behavior. A good correlation between the theoretical and experimental results shows that the strain-based percolation model is effective in describing the transition behavior of CH4 seepage in coal.

scholarly journals A New Type of Cemented Sand-Gravel (CSG) Mixtures for Water-Tightening of Hardfill Dams

2021 ◽  
Author(s):  
Sina Karimi ◽  
Hamed Farshbaf Aghajani
Keyword(s):  
Cement Hydration ◽  
Cement Content ◽  
Weight Ratio ◽  
Sem Images ◽  
Cemented Sand ◽  
Native Soil ◽  
New Type ◽  
Sand And Gravel ◽  
Compaction Properties ◽  
Native Soils

Abstract This paper aims to achieve a specific type of cemented sand-gravel mixtures with low permeability to implement in the impervious zone of hardfill dams. To this end, various mixtures are prepared by blending two native soils of sand and gravel with different amounts of kaolinite or bentonite additives in presence of various cement content. The compaction properties, uniaxial compressive strength, permeability and scanning electron microscope (SEM) images of mixtures are measured. According to the results, the cemented mixture containing 10% of kaolinite additive regardless of native soil type exhibits the maximum strength. However, the bentonite disturbs the cement hydration in the mixture, and the strength of mixtures especially with high cement content decreases with increasing the bentonite content. The permeability of mixtures is related to the amount of cement and fine additive in the mixture. The permeability of both cemented sand and gravel mixtures decreases with increasing the bentonite additive. However, the kaolinite additive has a limited influence on the permeability of cemented gravel mixtures. The lowest permeability is achieved in the mixture involving the higher amount of bentonite (with a weight ratio of 30%) in presence of adequate cement.

scholarly journals Experimental Research into the Evolution of Permeability of Sandstone under Triaxial Compression

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5065
Author(s):  
Liming Zhang ◽  
Shengqun Jiang ◽  
Jin Yu
Keyword(s):  
Axial Strain ◽  
Triaxial Compression ◽  
Testing Machine ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Rate Of Change ◽  
Peak Strength ◽  
Sudden Increase ◽  
Seepage Pressure ◽  
Confining Pressures

Failure tests on sandstone specimens were conducted under different confining pressures and seepage pressures by using an MTS triaxial rock testing machine to elucidate the corresponding correlations of permeability and characteristic stress with confining pressure and pore pressure during deformation. The results indicate that permeability first decreases and presents two trends, i.e., a V-shaped increase and an S-shaped trend during the non-linear deformation stage. The greater the seepage pressure, the greater the initial permeability and the more obvious the V-shaped trend in the permeability. As the confining pressure was increased, the trend in the permeability gradually changed from V- to S-shaped. Compared with the case at a high confining pressure, the decrease of permeability occurred more quickly, the rate of change becomes greater, and the sudden increase observed in the permeability happened earlier under lower confining pressures. Within the range tested, confining pressure exerted a greater effect on the permeability than the seepage pressure. In comparison with the axial strain, volumetric strain better reflected changes in permeability during compaction and dilation of sandstone. The ratio of crack initiation stress to peak strength ranged from 0.37 to 0.50, while the ratio of dilation stress to peak strength changed from 0.58 to 0.72. Permeabilities calculated based on Darcy and non-Darcy flow changed within the same interval, while the change in permeability was different.

The Study of Cemented Sand and Gravel Constitutive Model

2011 ◽  
Vol 243-249 ◽  
pp. 4596-4601
Author(s):  
Ming Quan Sun ◽  
Shi Feng Yang
Keyword(s):  
Constitutive Model ◽  
Axial Strain ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Cemented Sand ◽  
Shearing Strength ◽  
Sand And Gravel ◽  
Strain Increase ◽  
Peak Value

Basing on triaxial experiments, the paper conducts the research to Cemented Sand and Gravel constitutive model. Using virtual rigid spring method, the Cemented Sand and Gravel constitutive model with considering the softening characteristics of material is established, and parameters needed are determined, the model establishes the foundation of non-linear analysis of Cemented Sand and Gravel structure. Mechanical properties and constitutive model study of Cemented Sand and Gravel is key to Cemented Sand and Gravel faced eath-rockfill dam. Basing the Mechanical properties triaxial experiment of the material, the paper gives further discussion on the constitutive model of Cemented Sand and Gravel. From the results of the triaxial test, when the cemented material content is smaller than 20kg/m3, the stress strain curve agrees quite well with hyperbolic law to which the normal gravel test curve also obeys, the exception is the increase of shearing strength. If the cemented material content is more than 30kg/m3, there is a peak value on the stress strain curve, the curve (before peak value) shows that axial strain increase with deviatoric stress with the increment gradually changing slowly, i.e. the stress strain curve has obvious nonlinear feature. the curve peaks value at the axial strain =2％, the stress strain curve present softening pattern that deviatoric stress decreases with the strain increase if continuous applying axial load. When axial strain lies between 2% and 6%, the shearing strength of samples decreases rapidly, after this interval, the shear strength tends to the stable value in the final. It is core problem the paper try to solve that how to describe Cemented Sand and Gravel constitutive model.

Experimental Study on Engineering Properties of Cemented Sand and Gravel

2014 ◽  
Vol 580-583 ◽  
pp. 1846-1851
Author(s):  
Hua Fu ◽  
Jian Gang Feng ◽  
Hua Qiang Han ◽  
Hua Ling
Keyword(s):  
Permanent Deformation ◽  
Residual Deformation ◽  
Confining Pressure ◽  
Test Sample ◽  
Engineering Properties ◽  
Shear Tests ◽  
Cemented Sand ◽  
Sand And Gravel ◽  
Deformation Tests ◽  
Cementing Material

The static and dynamic triaxial shear tests and deformation tests on CSG (cemented sand and gravel) are conducted with different amount of added cementing materials. The mechanical indexes and parameters have obvious increments with mixing of cementing material and accumulation of curing days. However the increments will become mild with further adding of cementing material. The deformation curve of CSG test sample is similar to the curve of sand-gravel sample without mixing with any cementing material, and they both follow the trend of semi-logarithmic decrement law. The dynamic permanent deformation of CSG increases with the increments of confining pressure, consolidation stress and dynamic stress. Thus this deformation still can be calculated using the constitutive model of dynamic residual deformation proposed by Zhujiang Shen Academician.

scholarly journals Experimental Study on the Deformation and Permeability Characteristics of Raw Coal under the Coupling Effect of Confining Pressure and Pore Pressure

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Kangwu Feng ◽  
Kequan Wang ◽  
Yushun Yang
Keyword(s):  
Elastic Modulus ◽  
Pore Pressure ◽  
Coupling Effect ◽  
Axial Strain ◽  
Confining Pressure ◽  
Gas Pressure ◽  
Peak Strength ◽  
Permeability Evolution ◽  
Permeability Characteristics ◽  
Deformation Properties

The effects of confining pressure and pore pressure on the deformation and permeability characteristics of raw coal are studied experimentally. The deformation properties of raw coal by fracture and its permeability evolution laws under the coupling effect of confining pressure and pore pressure were further studied using a tri-axial servo-controlled seepage system for thermo-fluid-solid coupling of methane-bearing coal. The effects of confining pressure and gas pressure on the strength, elastic modulus, and permeability of raw coal were also analyzed. From the results, it was observed that rise in the confining pressure results in reduction of the initial permeability of raw coal and simultaneously increase its strength which results in higher axial deformation upon failure. Rise in gas pressure would increase the permeability and axial strain of raw coal on the whole and reduce its peak strength. Permeability first decreased and then increased during the loading of deviator stress, following a “V-shaped” change pattern. The results of sensitivity analysis indicated that confining pressure more significantly affected the peak strength and elastic modulus than gas pressure, while the gas pressure more significantly affected the permeability of the material than its confining pressure.

scholarly journals Small-Strain Dynamic Properties of Lean Cemented Sand and Gravel Materials under Different Cementing Agent Contents

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jie Yang ◽  
Xin Cai ◽  
Yangong Shan ◽  
Miaomiao Yang ◽  
Xingwen Guo ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Confining Pressure ◽  
Small Strain ◽  
Triaxial Tests ◽  
Dynamic Shear Modulus ◽  
Engineering Applications ◽  
Cemented Sand ◽  
Sand And Gravel ◽  
Cementing Agent

Lean cemented sand and gravel (LCSG) materials are increasingly being used in dams, embankments, and other civil engineering applications. Therefore, their mechanical properties and stress-strain behavior should be systematically understood. In this study, the small-strain dynamic properties of LCSG materials were examined. A series of dynamic triaxial tests were performed to investigate the effects of the confining pressure and cementing agent content of the material on its dynamic shear modulus (Gd) and damping ratio (λ). The results show that Gd increased and λ decreased with increasing confining pressure and cementing agent content; however, under the same confining pressure and cementing agent content, Gd decreased gradually in accordance with shear strain. Furthermore, new expressions were derived for Gd and λ, as well as for their maxima. The results of this study could provide a reference for practical engineering applications, including the construction of dams using LCSG materials.

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