The Study On The Stability Of Coarse Grained Soil High Embankment Under The Effect Of Transient Saturated Zone

High embankments need to be built when the expressway went across mountainous areas.With good permeability,high bearing capacity of engineering properties,coarse grained soil are widely used as material of high embankment in Hunan province.As the rain strikes Hu Nan province frequently,which leads to varying degrees catastrophic phenomenon such as slope sliding and uneven settlement of embankment and shortens the service life of embankment.Based on the national natural science fund project "research on the spatio-temporal evolution and disaster inducing mechanism of transient saturated zone of coarse-grained soil high embankment slope under extreme rainfall conditions(51508042)",first of all,similarity theory was used to establish the parameter relationship between the indoor model and the prototype embankment.Then,the model was used to research the seepage characteristics of coarse grained soil high embankment slope under long-time heavy rain and short-time rain storm.According to the researching results,revise the soil water characteristic curves of numerical simulation.Finally,introducing the seepage calculation results into FLAC3D,calculated the stability and the development of plastic zone of coarse grained soil high embankment slope.The researching results are shown as follows:(1)Based on indoor model test and numerical simulation software,the framework of coarse grained soil was chose as the researching object,and a stability calculation method of coarse grained soil high embankment was put forward which comprehensive considered the effect of matric suction,pore water pressure,seepage force and severe.It could truly reflect the effect of rainfall on slope stability.(2)According to the result of indoor test,with the rainfall going on,the transient saturated zone developed into the embankment layer by layer.The transient saturated zone show "S" type under long time heavy rainfall.The transient saturated zone show "J" type under short time rainstorm.The thrust occurred mainly in the deep embankment slope under the condition of long time heavy rainfall.With the duration of short time rainstorm increased,each monitoring point of the slope thrust increased.After rainfall,the thrust continued increasing.(3)According to the results of numerical simulation,the plastic zone firstly occurred on the slope surface and gradually developed to the foot of embankment stage,then,the plastic zone connect the whole embankment and the safety factor coefficient decreased quickly under long time heavy rainfall.After rainfall,the areas of plastic zone distributed at the foot of slope decreased gradually and the safety coefficient tend to be stable.The plastic zones were mainly distributed on slope surface and the safety coefficient decreased slowly.After rainfall,the plastic zone areas continued increasing and expanding into the embankment slope which led the safety coefficient decreased.By studying the effect of transient saturated zone distribution and development on stability under two kinds of rainfall,it has guiding significance on drainage designing and durability maintenance for the expressway of coarse grained soil high embankment slope.