Effect Of Mineral Composition On Physical And Mechanical Properties Of Mudstone And Its Engineering Application

Mudstone is widely distributed in China,which is an unavoidable rock mass in civil engineering construction.For example,mudstone of Badong red bed is common in highway and railway construction in eastern Chongqing and western Hubei.Mudstone has the characterized of low strength and softening and disintegration when it meets water,it often leads to engineering problems such as foundation settlement and landslide.No matter what type of mudstone,the main factor determining its physical and mechanical properties is mineral composition,so in-depth study of the relationship between the mineral composition of mudstone and its physical and mechanical characteristics,engineering characteristics has important reference value and practical significance.The study of the influence of mineral components on the properties of mudstone is based on the analysis of mudstone with different mineral components.In this paper,mudstones with different mineral components were collected from all over the country,and the influence of mineral components on the physical and mechanical properties of mudstones was analyzed by basic physical experiments,disintegration tests and indoor rock mechanics tests,providing data support for subsequent numerical simulation.Finally,the influence of mineral composition on engineering characteristics of mudstone is analyzed by numerical simulation.The research results provide the calculation basis and guidance for civil engineering construction of slope in mudstone area.The paper mainly conducts in-depth research from the following aspects:(1)The basic physical properties of mudstone with different mineral components are tested through basic physical experiments.The results show that the chemical components of mudstone are roughly the same in different geological ages,but there are great differences in mineral components and content.Mineral composition and content have great influence on the density,water absorption and water content of mudstone.(2)The disintegration characteristics of mudstone with different mineral components were tested through laboratory disintegration experiments.The results show that the higher the content of clay minerals,such as montmorillonite,the faster and more complete the disintegration of mudstone,and the smaller the particle size of the mudstone.According to the mineral content and disintegration phenomenon,the disintegration of mudstone can be divided into four grades: non-disintegration,weak disintegration,medium disintegration and strong disintegration.The dry-wet cyclic disintegration test shows that the more strongly the disintegration of mudstone,the more obvious the change of mass ratio of the particle size of the mudstone.Finally,based on the change law of mudstone microstructure obtained by scanning electron microscope,the disintegration mechanism of mudstone is summarized as mixing mechanism.(3)The mechanical properties of mudstones with different mineral components were tested by indoor rock strength mechanical experiments,including point load test,uniaxial compression test,Brazilian splitting test and direct shear test.The results show that the content of clay minerals and montmorillonite is negatively exponential with the uniaxial compression and tensile strength of mudstones,but have no obvious relationship with illite and kaolinite content.The mudstone with higher quartz content presents obvious brittleness characteristics during uniaxial compression,while the mudstone with higher clay mineral content has obvious residual stress and presents plastic characteristics.According to the morphology of mudstone specimens after breaking,the deformation failure can be divided into three types: shear failure,swelling failure and mixed failure.In addition,the AE test results show that the higher the clay mineral content is,the less the cumulative AE count of mudstone is in the process of uniaxial compression,and the lower the energy released by the rock is.(4)Under dry and natural conditions,the shear strength of mudstone is negatively correlated with the content of clay minerals and montmorillonite.Under saturated condition,the shear strength of mudstone has a negative exponential relationship with the content of clay minerals and montmorillonite.With the increase of the content of clay minerals or montmorillonite,the internal friction Angle and cohesion of mudstone decrease greatly at first,then slowly decrease until stable.(5)The experimental data of physical and mechanical properties of mudstone with different mineral components provide data support for numerical simulation.FLAC3 D numerical simulation software is used to analyze the stability of mudstone slope in practical engineering cases.The results show that the mudstone slope with high content of hydrophilic clay minerals,such as montmorillonite,has potential slip surface in natural state,and the higher the content,the lower the safety factor and the worse the stability of the slope.In addition,with the increase of water content,the greater the slope safety factor decreases,the greater the damage degree,scope and volume of landslide.