Research On Swelling Characteristic Of Swelling Rocks Under Wetting-drying Cycle

The physical and mechanical characteristics of the swelling rocks subjected to water will produce a large degree of change.When humidity and temperature changed,the rock mass would form micro-fissures,its entity integrity would decline and its physical and mechanical characteristics would also deterioration.It will make the safety and stability of engineering buildings decreased and easily cause various geological disaster.In this paper,the subject investigated is Swelling red sandstone in Zhuzhou area of Hunan Province and the research purposes are the swelling characteristics and its influencing factors subjected to different drying temperature and wetting-drying cycle.The micro-structure,mineral composition,swelling characteristics and its influencing factors of the swelling rocks are analyzed by which the results of free swelling ration experiments,swelling stress experiments,lateral constraint swelling ration experiments,a series of on these red swelling rock,such as scanning electron microscopy(SEM)experiment and X—ray diffraction experiment.The main content and work in the thesis are as following:1.The primary voids and structure,elemental content and mineral composition of the swelling rocks are analyzed by which the results of scanning electron microscopy(SEM)experiment,Electronic Differential System micro-element analysis and X—ray diffraction experiment are analyzed by Digital Imaging System,Energy Spectrum Analysis and Jade 6.0 software.The microscopic swelling mechanism of the swelling rocks was studied by it.The results of experiments: The original pores of the swelling rocks are more,The main mineral components of the swelling rocks: quartz,calcite,feldspar,mica,kaolinite,chlorite,illite,nontronite,montmorillonite;the main elements: O,Mg,Al,Si,K,Ca,Fe.2.The time history of the swelling rocks' swelling characteristics is analyzed by the results of swelling stress experiments,lateral constraint swelling ration experiments and free swelling ration experiments.The results of experiments: The time-history curves of swelling stress,lateral constraint swelling ration and free swelling ration are clearly divided into three stages:rapid expansion period,deceleration expansion period and slow stabilization period.The increment of swelling stress,lateral constraint swelling ration and free swelling ration.The increment of the swelling stress,the lateral constraint swelling ration and the free swelling ration mainly appear at the rapid and deceleration expansion period,and it is more than 95%.But The increment appearing at slow stabilization period is very small.3.With increasing of the cycles,the swelling stress and the lateral constraint swelling ration show increasing at first,and then gradually decreasing;and the increment of the sample's height also show increasing at first,and then gradually decreasing.The maximum increment of the sample's height appears in the third cycle.With increasing of the cycles,the sample's height show increasing before each cycle test;but the free swelling ration show decreasing.With increasing of the drying temperature,the swelling stress,the lateral constraint swelling ration and the free swelling ration show increasing,and they initial rate show growing.When the drying temperature is from 30?to 60?,they increment is very small,but when the drying temperature is from 60?to 105?,they increment is very more.When the drying temperature is from 30?to 60?,the changing of the sample's water content is very small,but when the drying temperature is from 60?to 105?,the changing of the sample's water content is very more.4.If the swelling rocks belongs to sheet-like structure,it's large porosity is relatively low,and it's surface pores are mainly dissolved pores,it will show a large amount of expansion.If the swelling rocks belongs to grain structure,and it's large porosity is relatively high,and it's surface pores are mainly intergranular pores,it will show a small amount of expansion.