Study On The Development Of Cracks In Yunnan Red Clay Under Dry And Wet Cycles

The subject that the development of laterite crack under the wetting-drying cycles is put forward in this paper,which is based on the background of the influence of extreme climate on Yunnan laterite,the research object is the Yunnan laterite.The characteristics of water translocation,crack development,microstructure and crack development mechanism of wetting-drying cycles laterite under different influence factors which includes the initial water content,initial dry density,test temperature,and the number of wetting-drying cycles were studyed by the vertical soil column water translocation test,wetting-drying cycles test and microstructure test combined with image processing,The result of this study has a important reference value for laterite area of Yunnan prevention and its cracks control.Characteristics of water translocation of laterite under wetting-drying cycles shown:The amount of water immigration in laterite decreases with the increase of its the initial dry density and initial water content in the process of wetting.However it decreases with the increase of its initial dry density of the laterite in the process of drying and it keeps the same amount with the increase of initial water content.After wetting-drying cycles,the laterite surface water content decreased,the internal water content increased,and the dry density decreased.The influence of water content on the development of crack in laterite under wetting-drying cycles shown:The laterite cracks during the wetting process,the higher the initial water content of the laterite,the earlier the crack occurs;The crack increases with the increase of the initial water content of the laterite during the drying process.The number,length and area of crack is positively correlated with initial water content.The crack width has a peak value with initial water content increasing first and then decreasing.The influence of dry density on the development of laterite crack under wetting-drying cycles shown:The laterite cracks during the wetting process,the higher the dry density of the laterite,the earlier crack occurs.The crack increases with the increase of the initial dry density of the laterite during the drying process.The number,length and area of crack increases with the increase of the initial dry density,the crack width has a peak value with initial dry density increasing first and then decreasing during the wetting-drying process.The influence of temperature on the development of laterite crack under wetting-drying cycles shown:The higher the temperature of the laterite,the less times it cracks;When the test temperature is low,there is no crack in the laterite.With the increase of temperature,the cracks increase during the wetting process.When the temperature further increase,the sample crack in drying process;The number,length and area of cracks are positively correlated with temperature,the crack width is positively correlated with temperature in the wetting process,and the crack width has a peak value in the drying process.The microstructure characteristics of laterite under wetting-drying cycles shown:The connection pattern of laterite particles is that the frame structure and the stack structure exist at the same time before wetting-drying cycles.After wetting-drying cycles,the connection of laterite particles is changed from frame structure to the stack structure;With the increase of the water content,dry density and temperature,the frame structure decrease,and the stack structure increase;After dry wetting-drying cycle,the void ratio and the number of particle increase,the roundness decrease,and the variation of fractal dimension and orientation are related to the initial dry density and initial water content.Development mechanism of laterite crack under wetting-drying cycles:The mechanism of laterite crack under wetting-drying cycles can be explained with four aspects:theory of electric double layer,theory of soil colloid,swelling force and kinetic energy of water molecular;The increase of water content,dry density and temperature magnify the deterioration effect on laterite under the wetting-drying cycles,and shorten the development period of the fracture;The development process of crack includes crack gestation period,crack formation and crack development period and crack stabilization period.