As a widely distributed geological and engineering material,the soil-rock mixture always undergoes frequentative and short-term freeze-thaw cycles in some regions.Its internal structure is destroyed seriously,but the ...As a widely distributed geological and engineering material,the soil-rock mixture always undergoes frequentative and short-term freeze-thaw cycles in some regions.Its internal structure is destroyed seriously,but the damage mechanism is not clear.Based on the damage factor,the damage research of properties of soil-rock mixture after different times of freeze-thaw cycles is investigated.Firstly,the size-distributed subgrade gravelly soil samples are prepared and undergo different times of freeze-thaw cycles periodically(0,3,6,10),and indoor large-scale triaxial tests are completed.Secondly,the degradation degree of elastic modulus is considered as a damage factor,and applied to macro damage analysis of soil-rock mixture.Finally,the mesoscopic simulation of the experiments is achieved by PFC3D,and the influence on strength between soil-rock particles caused by freeze-thaw cycles is analyzed.The results show that freeze-thaw cycles cause internal damage of samples by weakening the strength between mesoscopic soil-rock particles,and ultimately affect the macro properties.After freeze-thaw cycles,on the macro-scale,elastic modulus and shear strength of soil-rock mixture both decrease,and the decreasing degree is related to the times of cycles with the mathmatical quadratic form;on the meso-scale,freeze-thaw cycles mainly cause the degradation of the strength between soil-rock particles whose properties are different significantly.展开更多
As a frequently-used roadbed filler,soil-rock mixture is often in the environment of freeze-thaw cycles and different confining pressures.In order to study the freeze-thaw damage mechanism of elastic modulus of soil-r...As a frequently-used roadbed filler,soil-rock mixture is often in the environment of freeze-thaw cycles and different confining pressures.In order to study the freeze-thaw damage mechanism of elastic modulus of soil-rock mixtures at different confining pressures,the concept of meso-interfacial freeze-thaw damage coefficient is put forward and the meso-interfacial damage phenomenon of soil-rock mixtures caused by the freeze-thaw cycle environment is concerned;a double-inclusion embedded model for elastic modulus of soil-rock mixtures in freezing-thawing cycle is proposed.A large triaxial test was performed and the influences of confining pressure and experimental factors on elastic modulus of soil-rock mixtures were obtained,and then the accuracy of the double-inclusion embedded model to predict the elastic modulus of soil-rock mixtures in freezing-thawing cycle is verified.Experiment results showed that as to soil-rock mixtures,with the increase of confining pressure,the elastic modulus increases approximately linearly.The most crucial factors to affect the elastic modulus are rock content and compaction degree at the same confining pressure;the elastic modulus increases with the increase of rock content and compactness;as the number of freeze-thaw cycles increases,the freeze-thaw damage coefficient of meso-structural interface and the elastic modulus decrease.展开更多
The waste dump of open-pit coal mine is remade of soil-rock mixture under the action of gravity,dynamic load of transportation equipment and earthquake,etc.By using artificial synthetic transparent soil,the developing...The waste dump of open-pit coal mine is remade of soil-rock mixture under the action of gravity,dynamic load of transportation equipment and earthquake,etc.By using artificial synthetic transparent soil,the developing process and migration law for soil-rock mixture are observed in the remade process.The mixture of fused quartz sand,liquid paraffin and n-tridecane is chosen as the material for synthetic transparent soil which is mixed with liquid paraffin and n-tridecane at a mass ratio of4.4at room temperature of17℃.Physical and mechanical properties of transparent soil are determined by physical test and compared with those in natural sandy soil.The results show that transparent soil and sandy soil have high similarity,in other words,transparent soil can be used for similar simulation experiments of soil-rock mixture.展开更多
The mesoscopic failure mechanism and the macro-mechanical characteristics of soil-rock mixture(S-RM) under external load are largely controlled by S-RM's meso-structural features. The objective of this work is to ...The mesoscopic failure mechanism and the macro-mechanical characteristics of soil-rock mixture(S-RM) under external load are largely controlled by S-RM's meso-structural features. The objective of this work is to improve the three-dimensional technology for the generation of the random meso-structural models of S-RM, for randomly generating irregular rock blocks in S-RM with different shapes, sizes, and distributions according to the characteristics of the rock blocks' size distribution. Based on the new improved technology, a software system named as R-SRM3 D for generation and visualization of S-RM is developed. Using R-SRM3 D, a three-dimensional meso-structural model of S-RM is generated and used to study the meso-mechanical behavior through a series of true-triaxial numerical tests. From the numerical tests, the following conclusions are obtained. The meso-stress field of S-RM is influenced by the distribution of the internal rock blocks, and the macro-mechanical characteristics of S-RM are anisotropic in 3D; the intermediate principal stress and the soil-rock interface properties have significant influence on the macro strength of S-RM.展开更多
Soil-rock mixture(S-RM)is a widely distributed geotechnical medium composed of "soil" and "rock block" different both in size and strength. Internal rock blocks form special and variable meso-struc...Soil-rock mixture(S-RM)is a widely distributed geotechnical medium composed of "soil" and "rock block" different both in size and strength. Internal rock blocks form special and variable meso-structural characteristics of S-RM. The objective of this work was to study the control mechanism of meso-structural characteristics on mechanical properties of S-RM. For S-RM containing randomly generated polygonal rock blocks, a series of biaxial tests based on DEM were conducted. On the basis of research on the effects of rock blocks' breakability and sample lateral boundary type(rigid, flexible) on macroscopic mechanical behavior of S-RM, an expanded Mohr-Coulomb criterion in power function form was proposed to represent the strength envelop. At the mesoscopic level, the variations of meso-structure such as rotation of rock block, and the formation mechanism and evolution process of the shear band during tests were investigated. The results show that for S-RM with a high content of rock block, translation, rotating and breakage of rock blocks have crucial effects on mechanical behavior of S-RM. The formation and location of the shear band inside S-RM sample are also controlled by breakability and arrangement of rock blocks.展开更多
土石混合体-基岩接触面是下伏基岩堆积体边坡稳定性的主要控制面,基覆面形态特征是重要的设计内容。为此,开展了不同基覆面形态参数条件下接触面室内大型直剪试验,研究了基覆面形态参数对接触面剪切力学特性的影响,探讨了接触面土石颗...土石混合体-基岩接触面是下伏基岩堆积体边坡稳定性的主要控制面,基覆面形态特征是重要的设计内容。为此,开展了不同基覆面形态参数条件下接触面室内大型直剪试验,研究了基覆面形态参数对接触面剪切力学特性的影响,探讨了接触面土石颗粒运动概化模式,建立了接触面剪切简化的复合幂-指数模型(composite power exponential model,CPE模型)。结果表明:随着粗糙度的增加,接触面抗剪强度不断增大,表观内摩擦角和表观黏聚力分别呈非线性上凸增长和似线性增长趋势,随着锯齿高度的增加,接触面抗剪强度先增大后减小,增加锯齿高度对表观黏聚力的影响较为明显;接触面剪应力-剪切相对位移关系曲线基本呈弱硬化型,土石颗粒骨架密实度随粗糙度的增大而减小,但随锯齿高度的增大呈先增大后减小,接触面土石颗粒运动主要表现为咬合、翻转和滑移,较高法向应力时会发生颗粒破碎和基岩尖端剪切破坏;模型参数k、b和n与无量纲化法向应力σ_(n)/Pa存在线性关系(σ_(n)为法向应力,P_(a)为标准大气压),拟合系数α_(i)(i=1,2)不受基覆面形态参数的影响,拟合系数βi和i分别与粗糙度R和锯齿高度D存在线性关系;简化CPE模型能够很好地模拟出不同基覆面形态参数条件下土石混合体-基岩接触面剪切变形全过程,模型适用性良好,参数的确定方法合理且可行。展开更多
基金Project(50908234)supported by the National Natural Science Foundation of ChinaProject(2017G002-K)supported by the Key Subject of Science and Technology Research and Development Plan of China Railway General Corporation
文摘As a widely distributed geological and engineering material,the soil-rock mixture always undergoes frequentative and short-term freeze-thaw cycles in some regions.Its internal structure is destroyed seriously,but the damage mechanism is not clear.Based on the damage factor,the damage research of properties of soil-rock mixture after different times of freeze-thaw cycles is investigated.Firstly,the size-distributed subgrade gravelly soil samples are prepared and undergo different times of freeze-thaw cycles periodically(0,3,6,10),and indoor large-scale triaxial tests are completed.Secondly,the degradation degree of elastic modulus is considered as a damage factor,and applied to macro damage analysis of soil-rock mixture.Finally,the mesoscopic simulation of the experiments is achieved by PFC3D,and the influence on strength between soil-rock particles caused by freeze-thaw cycles is analyzed.The results show that freeze-thaw cycles cause internal damage of samples by weakening the strength between mesoscopic soil-rock particles,and ultimately affect the macro properties.After freeze-thaw cycles,on the macro-scale,elastic modulus and shear strength of soil-rock mixture both decrease,and the decreasing degree is related to the times of cycles with the mathmatical quadratic form;on the meso-scale,freeze-thaw cycles mainly cause the degradation of the strength between soil-rock particles whose properties are different significantly.
基金Project(50908234)supported by the National Natural Science Foundation of China
文摘As a frequently-used roadbed filler,soil-rock mixture is often in the environment of freeze-thaw cycles and different confining pressures.In order to study the freeze-thaw damage mechanism of elastic modulus of soil-rock mixtures at different confining pressures,the concept of meso-interfacial freeze-thaw damage coefficient is put forward and the meso-interfacial damage phenomenon of soil-rock mixtures caused by the freeze-thaw cycle environment is concerned;a double-inclusion embedded model for elastic modulus of soil-rock mixtures in freezing-thawing cycle is proposed.A large triaxial test was performed and the influences of confining pressure and experimental factors on elastic modulus of soil-rock mixtures were obtained,and then the accuracy of the double-inclusion embedded model to predict the elastic modulus of soil-rock mixtures in freezing-thawing cycle is verified.Experiment results showed that as to soil-rock mixtures,with the increase of confining pressure,the elastic modulus increases approximately linearly.The most crucial factors to affect the elastic modulus are rock content and compaction degree at the same confining pressure;the elastic modulus increases with the increase of rock content and compactness;as the number of freeze-thaw cycles increases,the freeze-thaw damage coefficient of meso-structural interface and the elastic modulus decrease.
基金Project(2015QNA40)supported by the Fundamental Research Funds for the Central Universities,China
文摘The waste dump of open-pit coal mine is remade of soil-rock mixture under the action of gravity,dynamic load of transportation equipment and earthquake,etc.By using artificial synthetic transparent soil,the developing process and migration law for soil-rock mixture are observed in the remade process.The mixture of fused quartz sand,liquid paraffin and n-tridecane is chosen as the material for synthetic transparent soil which is mixed with liquid paraffin and n-tridecane at a mass ratio of4.4at room temperature of17℃.Physical and mechanical properties of transparent soil are determined by physical test and compared with those in natural sandy soil.The results show that transparent soil and sandy soil have high similarity,in other words,transparent soil can be used for similar simulation experiments of soil-rock mixture.
基金Project(51109117)supported by the National Natural Science Foundation of ChinaProject(20111081125)supported by the Independent Research Plan of Tsinghua University,ChinaProject(2013-KY-4)supported by the State Key Laboratory of Hydroscience and Engineering Project,China
文摘The mesoscopic failure mechanism and the macro-mechanical characteristics of soil-rock mixture(S-RM) under external load are largely controlled by S-RM's meso-structural features. The objective of this work is to improve the three-dimensional technology for the generation of the random meso-structural models of S-RM, for randomly generating irregular rock blocks in S-RM with different shapes, sizes, and distributions according to the characteristics of the rock blocks' size distribution. Based on the new improved technology, a software system named as R-SRM3 D for generation and visualization of S-RM is developed. Using R-SRM3 D, a three-dimensional meso-structural model of S-RM is generated and used to study the meso-mechanical behavior through a series of true-triaxial numerical tests. From the numerical tests, the following conclusions are obtained. The meso-stress field of S-RM is influenced by the distribution of the internal rock blocks, and the macro-mechanical characteristics of S-RM are anisotropic in 3D; the intermediate principal stress and the soil-rock interface properties have significant influence on the macro strength of S-RM.
基金Projects(51323014,51479095)supported by the National Natural Science Foundation of ChinaProject(20111081125)supported by Independent Research Plan of Tsinghua University,ChinaProject(2013-KY-4)supported by the State Key Laboratory of Hydroscience and Engineering Project,China
文摘Soil-rock mixture(S-RM)is a widely distributed geotechnical medium composed of "soil" and "rock block" different both in size and strength. Internal rock blocks form special and variable meso-structural characteristics of S-RM. The objective of this work was to study the control mechanism of meso-structural characteristics on mechanical properties of S-RM. For S-RM containing randomly generated polygonal rock blocks, a series of biaxial tests based on DEM were conducted. On the basis of research on the effects of rock blocks' breakability and sample lateral boundary type(rigid, flexible) on macroscopic mechanical behavior of S-RM, an expanded Mohr-Coulomb criterion in power function form was proposed to represent the strength envelop. At the mesoscopic level, the variations of meso-structure such as rotation of rock block, and the formation mechanism and evolution process of the shear band during tests were investigated. The results show that for S-RM with a high content of rock block, translation, rotating and breakage of rock blocks have crucial effects on mechanical behavior of S-RM. The formation and location of the shear band inside S-RM sample are also controlled by breakability and arrangement of rock blocks.
文摘土石混合体-基岩接触面是下伏基岩堆积体边坡稳定性的主要控制面,基覆面形态特征是重要的设计内容。为此,开展了不同基覆面形态参数条件下接触面室内大型直剪试验,研究了基覆面形态参数对接触面剪切力学特性的影响,探讨了接触面土石颗粒运动概化模式,建立了接触面剪切简化的复合幂-指数模型(composite power exponential model,CPE模型)。结果表明:随着粗糙度的增加,接触面抗剪强度不断增大,表观内摩擦角和表观黏聚力分别呈非线性上凸增长和似线性增长趋势,随着锯齿高度的增加,接触面抗剪强度先增大后减小,增加锯齿高度对表观黏聚力的影响较为明显;接触面剪应力-剪切相对位移关系曲线基本呈弱硬化型,土石颗粒骨架密实度随粗糙度的增大而减小,但随锯齿高度的增大呈先增大后减小,接触面土石颗粒运动主要表现为咬合、翻转和滑移,较高法向应力时会发生颗粒破碎和基岩尖端剪切破坏;模型参数k、b和n与无量纲化法向应力σ_(n)/Pa存在线性关系(σ_(n)为法向应力,P_(a)为标准大气压),拟合系数α_(i)(i=1,2)不受基覆面形态参数的影响,拟合系数βi和i分别与粗糙度R和锯齿高度D存在线性关系;简化CPE模型能够很好地模拟出不同基覆面形态参数条件下土石混合体-基岩接触面剪切变形全过程,模型适用性良好,参数的确定方法合理且可行。
