Research On Disintegration Characteristics Of Red-bedded Mudstone Under Hygrothermal Conditions

Red-bed mudstone are widely distributed in the central and western region of China,including red conglomerates,sandy conglomerates,argillaceous rocks,sandy shales and siltstones,and most of them have disintegration characteristics,that is,water swelling and shrinkage,resulting in cracking and fragmentation,especially in subtropical continental monsoon humid climate areas such as Hunan,where there are abundant rainfall and alternation of dry and wet under the influence of various temperatures.The bad environment has a great impact on the road-bed filling treatment,tunnel surrounding rock stability and slope stability.Therefore,the experimental study of red mudstone disintegration under hot and humid conditions can provide a theoretical basis for engineering.This article mainly carries on the research from the following aspects:The mineral composition,chemical composition and microscopic characteristics of mudstone are analyzed and tested,and the relationship between mudstone disintegration and mineral composition is analyzed.XRD test shows that red mudstone contains montmorillonite and chlorite,and has strong hydrophilicity.SEM test can observe the distribution structure and cementation degree of mineral composition of red mudstone.The initial strength and mechanical properties of mudstone are determined by the micro-cracks,micro-holes in structure,mineral particles and mineral aggregates.Through a series of indoor geotechnical tests on the parameters of red mudstone,the physical and hydraulic properties of red mudstone are revealed.It is concluded that red mudstone is a kind of mudstone with very low durability,and its disintegration and fragmentation ability is very strong if it is in the condition of wet-dry alternation.The laboratory immersion test and dry-wet cyclic disintegration test of red mudstone in different areas under different humid and thermal conditions were carried out.The disintegration mechanism of red mudstone under the combined action of water and temperature and the optimum dry-wet cyclic disintegration conditions were discussed.The variation of particle size under different humid and thermal conditions was analyzed,the disintegration mechanism of red mudstone under the influence of various factors was explained,the the evaluation criteria of disintegration speed and disintegration stability was put forward·By introducing fractal theory,the change rule of fractal dimension of particle size distribution during wet-dry cyclic disintegration of red mudstone under different hydrothermal conditions is discussed.It is concluded that when disintegration is stable,the fractal dimension tends to be stable from 2.38 to 2.53.The fractal dimension can reach 2.53,15 and 45 degrees centigrade under the stable condition of 25 degrees centigrade disintegration.The fractal dimension can reach 2.50 after the disintegration tends to be stable,and 2.38 after the 35 degrees centigrade disintegration tends to be stable.