Experimental Study On Loess Slope Water&Gas Transformation Law Under Dry-wet Cycle And Stability Analysis

Rainfall and sunshine of water near the surface of unsaturated loess was very great influence.With the continuous development and construction in the loess area,water &gas transformation of unsaturated loess slope under the dry-wet cycles has caused attention in the field of geotechnical engineering.The rainfall infiltration and evaporation of water will cause the changes of unsaturated loess slope in the pore water pressure and pore air pressure and matrix suction.At the same time, the slope soil shear strength are changes,so the slope produces displacement.In addition,effect of water field and temperature field in depth but also has a direct impact on the position of the sliding surface of slope destabilization.Rainfall as the main cause of the instability of unsaturated loess slope has become the consensus,but the effect of the dry-wet cycle on unsaturated loess slope is not perfect. The study clearly unsaturated loess slope under the condition of dry-wet cycle of moisture content,pore water pressure and pore air pressure and soil displacement variation,in the process of landslide treatment, we can save the project investment scientifically and reasonably.In this paper, the research object of Ma Lan loess in Lanzhou.The combination of qualitative and quantitative analysis,system analysis and research on the change law and the stability of the unsaturated loess slope under dry-wet cycle condition.Then have made some valuable achievements.First of all, this paper carries out the experiment of physical characteristics.Determination of the grading curve,optimum water content, maximum dry density, liquid-plastic limit and the permeability coefficient of filling of the Ma Lan loess,prepare for after work.Secondly, indoor model test is carried out in this paper.We use the "bottle" approach to increase the water content of slope soil,and use the direct illumination to simulate the water evaporation in the soil. The model test using the water sensors,temperature sensors, large range dial indicator and homemade soil pressure testing device.The indoor model test of dry-wet cycle conducted a total of three groups.Recording and monitoring the change of water field,temperature field,soil displacement,the soil pressure and other related physical quantities of unsaturated loess slope under the effect of dry-wet cycle.Research on the law of water&gas transformation influence factors of deformation and failure of unsaturated loess slope under dry-wet cycle condition.Finally,we use module SEEP/W in the Geo-Studio software,to simulate the transient seepage field in the unsaturated loess slope under different rainfall.The distribution of pore water pressure and volumetric water content of loess slope under different time periods are obtained.After that, the result of unsaturated seepage analysis is coupled to VADOSE/W,set the sunshine condition,the slope temperature distribution and temperature field of water fieldeffect in continuous heating condition is obtained.At last, the results of seepage analysis coupled to the SIGMA/W and SLOPE/W module to calculate the displacement of the slope and the variation of the strain field.Use this result to analysis the slope stability,discuss the variation of shear strength with depth and the safety coefficient with rainfall time.This paper analyze the indoor model test and the numerical simulation get some important conclusions.It will provide theoretical support and design basis for practical engineering.