Study On Disintegration Characteristics Of Strongly Weathered Mudstone In Drawdown Area Of Three Gorges Reservoir

Rocks in drawdown area are in the environment of cyclic wetting-drying conditions during the course of reservoir operation and be prone to disintegrate and adversely affect the stability of mudstone slope,even cause slope instability.In order to study the disintegration characteristics of strongly weathered mudstone,we developed,a set of device(SGRYBJY-2016)which can not only simulate the stress and cyclic wetting-drying conditions,but also used to perform disintegration test for soft rock.The disintegration test,material composition change and macro meso structure test were carried out on the mudstone specimens,based on the results of the tests mentioned above,the disintegration mechanism of the mudstone in drawdown area was revealed.The specific research contents and results in this dissertation are summarized as follows:(1)Firstly,Simulation tests on the stress and cyclic wetting-drying conditions of drawdown area were done to determine the durations of wetting and drying.The test results show that while mudstone in the stress from three directions is 0MPa,the wetting time was 4 days and the drying time was about 1 day;while in two direction stress state,the wetting time is 3 days and the drying time is 1 day.(2)Secondly,mudstone disintegration test under stress and wetting-drying cycles was carried out,after each cycles,the parent rock and its disintegration was tested,and take some samples from the parent rock to pull X ray diffraction,energy dispersive spectroscopy,scanning electron microscopy and water absorption test,chemical composition of soaking solution was also tested.Obtain the mudstone composition,particle size distribution and macro meso structure changes with the increase number of wetting-drying cycles.(3)Thirdly,According to the water absorption and grain size test results,mathematical model of water absorption and slake durability index with the increase number of wetting-drying cycles was established,while the stress from three directions is 0MPa,the water absorption is logarithmic function change,the disintegration index for the exponential function change;while mudstone in two direction stress state,water absorption and disintegration index is both change like exponential function.(4)Finally,Analyz the mudstone composition,particle size distribution and macro meso structure changes with the increase number of wetting-drying cycles in cyclic wetting-drying and stress conditions,the disintegration mechanism of strongly weathered mudstone was revealed.