Effects Of Periodic Water-saturation On Shear Characteristics Of Saturated Sandstone-mudstone Mixture

Sand mud mixture is often used as the main building material for the bank fill projects in the Three Gorges reservoir area,such as embankments,pier bank slopes,and so on.The elevation of the water reservoir level will inevitably cause the sand and mud mix to undergo periodic water saturation.The periodic saturated effect makes the shear strength of the sand-mud mix decrease and the deformation increase,which may affect the safe use of the structure.It is of great scientific significance and engineering value to study the effect of periodic saturated water on the shearing characteristics of sand-mud mixes for solving the application of sand-mud mixes in water-related projects.This paper relies on the National Natural Science Foundation of China(No.51479012),“Research on the Deterioration Mechanism and Evolution of Periodically Full-Saturated Sand and Mudstone Mixtures”,to go on this study.Through the triaxial shear test of sand-shale mixture,the effect of periodic saturated water on the shear resistance of sand-shale mixture saturated condition was investigated.The specific research methods and results are as followed:(1)Through uniaxial compression tests of sandstone and mudstone,the uniaxial compressive strength,elastic modulus,sandstone and mudstone uniaxial compression tests of natural mudstones and sandstones are brittle and the failure surface runs through the whole.The sample has a certain angle between the failure surface and the vertical direction,and the damage surface of the sandstone is more obvious than the mudstone.(2)Through the triaxial shear test,the effect of periodic saturated water on the shear strength and deformation of sandstone and sandstone mudstone mixtures with different sample characteristics was obtained.According to the experimental results,the deviated stress peak of sand-shale mixture increases with the increase of dry density and particle gradation,and decreases with the increase of mudstone particle content;the peak value of volumetric strain decreases with the increase of dry density and particle grading and increase with the increase of mudstone particle content;axial strain increase with the increase of dry density,and increase with the increase of mudstone content during cyclic saturation cycle.The volumetric strain increment decreases with the increase of dry density and particle size distribution,and increases with the increase of mudstone content.(3)Based on the data of cyclic saturation effects on the shear strength and deformation of sandstone and sandstone mudstone mixtures under different test conditions,the overall confining pressure and stress level of the deviatoric stress of the sand mudstone mixture increases.High,decreases with increasing number of periodic saturated water;peak volumetric strain increases with confining pressure,and there is no obvious change in the stress level and periodic saturation frequency;strain increment during cyclic saturation cycle(Axial strain increment and volumetric strain increment)increase with the number of periodic saturated cycles,confining pressure,and stress levels.The sample of sandstone material and sand mudstone mixture mainly suffered from shear failure and shear failure.(4)According to the particle sieving results of sand-shale mixture,the particle breakage ratio B_g of sandstone and sand-mudstone mixtures with different characteristics under cyclic saturation increases with the increase of dry density and mudstone content and decreases with the increase of particle size distribution;under different test conditions,the particle breakage rate B_g of sandstone material and sand mudstone mixture increase with the increase of cyclic saturation cycle,confining pressure,and stress level.In general,the sand-shale mixture formed after the incorporation of mudstone particles has a higher rate of particle breakage than the sandstone material under the conditions of this study.