Analysis Of Disintegration Characteristics And Microscopic Mechanism Of Red Bed Soft Rock In Central Sichuan Province Under Dry-wet Cycle

The red layer soft rock is widely distributed in China.The fresh rock layers exposed by the excavation of the project are prone to disintegration under the action of natural and dry alternating wet and dry cycles,which is detrimental to the stability and safety of slopes and roads.Impact.Based on a high-speed railway project in central Sichuan,this paper selects the fresh red layer soft rock just excavated as the research object,and conducts the disintegration test under the condition of dry-wet cycle.The disintegration characteristics and microscopic of the red-layer soft rock The mechanism was analyzed and the relationship between swelling and disintegration was studied.The main research work is as follows:Firstly,the fresh and weakly weathered soft rock retrieved at the site was taken as the research object,and the basic physical property test,the penetration test,the uniaxial compressive strength test and the expansive test were carried out.The density and water content of the red rock soft rock in the Sichuan Basin were studied.Basic understanding of basic characteristics such as permeability and strength has been made.According to the Classification Standards for Railway Engineering Geotechnical,the red-layer soft rock samples are divided into expansive and non-expanded rocks.Secondly,the disintegration test of red-layer soft rock under dry-wet cycle conditions was carried out.The state change and characteristics of red-layer soft rock disintegration were observed.The particle size variation of soft rock disintegration after several wet-dry cycles was analyzed.The effects of initial water content and water immersion time on the degree and rate of disintegration were analyzed.The development law of swelling property of red layer soft rock was compared and the relationship bet,ween swelling and disintegration was studied.Finally,the X-ray diffraction(XRD)and scanning electron microscopy(SEM)analysis of the disintegration times of different cycles and different particle groups during the test were carried out to obtain the changes of clay mineral composition and microstructure in the cyclic disintegration test of mudstone.Using MATLAB mathematics software to carry out digital quantitative analysis of SEM images,analyze the structural changes of red-layer soft rock after disintegration in dry-wet cycle from the angle of surface porosity and maximum particle area in the image,so as to analyze the red-layer soft rock Further understanding of the disintegration mechanism.