Study On The Stability Of Loess Slope Upon Wetting

Loess in China is world-famous for its large thickness,full stratum and vast expanse of distribution.It spreads out from the“Central Loess Plateau”on a plane,covering an area of 6.3×10~5 square kilometers.Loess landslides are one of the serious geological problems.Among the many factors that leading to loess landslides,there are wetting effects caused by rainfall and irrigation.Therefore,it is of great theoretical and practical significance to study the law of wetting deformation of loess slope and the problem of wetting stability.In order to further understand the stability of loess slope,Loess in Tianshui and Heifangtai in Gansu province have been taken as the research object.According to the complex stress history and frequency of human activity under the loess cliff in Tianshui area,and long-time and large-scale farmland irrigation in Heifangtai area,there have much large scale of landslides.So different experimental studies have been carried out on the loess in these two places,including the triaxial test study of loess landslide caused by infiltration,the experimental study on the influence of stress history on the wetting deformation of Tianshui loess and the centrifuge model test of the Heifangtai loess.From the results of experiments,main research findings can be presented as follows.(1)In the ACU test of the two loess samples,the deformation develops slowly and the trend is almost the same,but in the SDL test,deformation occurs suddenly,which indicates the process of wetting has changed the deformation mode of the loess,making the deformation of the loess slope more rapidly and uncontrollably.(2)After the simulation of stress history of Tianshui loess,then the ACU test and the SDL test have been conducted;the shape of the wetting deformation of Tianshui loess is analyzed and discussed.During the wet process,the deviatoric stress development of the samples with different pre-consolidation pressures is almost the same,indicating that the influence of stress history on the bearing capacity of the soil is negligible;in the process of wetting deformation,the samples with high pre-consolidation pressure levels are completely destroyed and cost more time,but the process of losing the bearing capacity is more rapid;with the increase of the pre-consolidation pressure,the dilatancy phenomenon is more obvious when the loess sample is sheared.(3)Through two groups centrifugal model experiment of Heifangtai loess landslide induced by infiltration,the wetting deformation characteristics of the loess slope during the rise of water table and surface irrigation infiltration are studied respectively.It shows that the rise of water table while leads the infiltration zone moving to the surface of slope,and the groundwater overflows from the surface of loess slope,which cause the strength reduction of the slope.The centrifugal model test of surface irrigation shows that the irrigation can cause the increase of water content obviously during the depth of 2m below the surface and let the cracks develop heavily at the top of slope.The instability of the edge structure of the loess slope leads to the occurrence of landslide.