Experiment Researchon The Behavior Of Unsaturated Residual Soil Slope Under Wetting-drying Cycles

In recent years,building of infrastructure makes the residual soil slope exposed to natural environment derectly.Slope soil experience wetting and drying for a long time influenced by seasonal climate factors,and the soil is repeatedly in the process of soil unsaturated and saturated.The changes of soil water content and suction affect the properties of soil and slope stability.Therefore,it is necessary to research on the strength of the unsaturated residual soil and the response regularity of the slope under wetting-drying cycles.In the dissertation,experimental studies and physical model test studies were undertaken on an undisturbed residual soil from South east of Fujian area in order to discuss the variation of shear strength with the change of water contain and the cyclic number,and the response regularity of water contain,pore water pressure and deformation under wetting-drying cycles.The main results obtained are as followed:(1)The variable law of the strength of unsaturated residual soil under wetting and drying cycle is discussed by straight scissors test,and the relationship between strength and moisture content&cyclic number of unsaturated residual soil under wetting and drying cycle effect is discussed.based it on,attenuation formula of strength is established correspondingly.(2)On the basis of the relationship between the amount of strength attenuation and cyclic number,the S-shaped function is adopted for fitting.The results show that the S-shaped function can well describle the attenuation rules of cohesion with the change of cyclic number.The results also have an important reference value for further reveal the influence of wetting-drying cycles on deterioration mechanism of granite residual soil and long-term stability of residual soil slope in South east of Fujian.(3)According to the results of model test monitoring data,we can find that with the number of cycles increasing,the peak water content of surface soil and the peak pore water pressure of deep soil are decreasing,but the peak water content of deep soil and the peak pore water pressure of surface soil are increasing.The deformation of slope crest soil has a tendency to the down slope direction with the increase of wetting-drying numbers,and the tendency of the deformation of slope surface soil in the down slope direction is more and more obvious with the the increase of wetting-drying number.(4)Wetting-drying cycle range mainly affects the response time of the suction and moisture content,change rate and change range,and the change trend of moisture content and suction is not affected by the range of the wetting-drying cycle.