Study Of Influence On Stability Of Filled Slope By Rainfall

As the engineering and construction projects become more and more in therecent years, the filled slope is widely distributed in the hills, mountains and placeswith undulation terrain. The accidents caused by the filled slope are often heard in theengineering community. Raining is the most important and staple environmentalfactor which affects the stability of the slope and might finally lead to the slide.Taking the filled slope in the research area as object, basing on the basic theoryofnon-saturated soil, saturated-unsaturated seepage theory, combining theengineering geological conditions and the features of the filled slope, this article hasdone the research on the filled slope rainfall physical simulation experiment. Throughthe observation on the change of the filled slope models’ pore water pressure, thecorrelation is summarized on different conditions like rainfall duration, rainfall type,pre-precipitation, and the change of the seepage field in the latter part is analyzed.Then by using of the finite element software the simulation parameters inversion andthe numerical calculation on the seepage field and stress-strain are done. Based onwhat was done before the influence on the filled slope by the rainfall can be analyzed.The main research contents and results:1. Based on what has been done before, through the deep research on unsaturatedsoil mechanics and saturated-unsaturated seepage theory, the influencing factors ofsoil-water characteristic curve is perfected, the basic law of slope rainfall infiltrationis investigated and the influence on unsaturated soil slopes by rainfall infiltration isanalyzed.2. Through the investigation of the engineering geological conditions and theanalysis on the fill slope’s characteristic, by use of similarity theory， this article builta side slope rainfall physical simulation system and carried out physical simulationexperiment. Based on the analysis on rainfall experiment on filled slope theconclusion comes out that the relationship is the corresponding between the rise and fall of the pore water pressure and the start and stop of the rain and there’s a certaindelayed effects. During the rising of porewater pressure, the relationship between thepressure values and the time in the depth of0.25m and0.50m is:u_w=-0.0168t~2+0.2528t+0.2171、uw=-0.0095t~2+0.1162t+0.1238. The early raining stagehas the direct affect on the pore water pressure in the slope body. The dissipation ofthe pore water is slow in the later raining stage. The pore water pressure is the overalldownward trend during the dissipation but will increase at a rate for a short time foronce.3. Based on the filled slope rainfall physical simulation experiment, through theparameter inversion of the soil-water characteristic curve, the parameters of the slopesoil is gotten. By use of the finite element numerical model the seepage field of thefilled slope can be simulated on condition of raining. The analysis shows that duringthe rain the slope surface will saturate first. The saturated zone are scattered in the topof the hill platform and the inflection point position, then the saturated zone ishorizontal expansion and through the surface and are mainly distributed in the table5m depth from the slope or less with the vector direction of flow parallel to the slopedown to the distribution of water along the region converged towards its base corner.The deeper the filled slope is, the smaller influence by the rainfall is on the seepagefield.4. Through the physical modeling and numerical simulation, this articleinvestigated the formation and development of law of the saturated zone of the filledslope on condition of raining and put forward that the development of the saturationregion is mainly divided into5stages:①Stage of partial surface saturation.②Stage ofsurface saturation region breaking-through.③Stage of slope’s foot saturation regionexpanding.④Stage of slope’s foot saturation region moving.⑤Stage of the bottomsaturation region rising.5. Through the numerical simulation of coupled calculation of the finite elementsoftware, this article analyzed the stress and strain situation of the filled slope after24hours raining. After the continuous rainfall the shear stress concentration occurredmainly at the elevation of200m～210m (The actual elevation) and has a paralleldistribution along the slope which was about3m away from the slope vertical distance.The displacement along the X direction is mainly occurred on the middle of the slopeand decreases little by little in direction of both sides and the top. The displacementalong the Y direction is mainly occurred inside the slope body and decreases indirection of the bottom and outside. The maximum displacement of the slope in the X-direction is1.569m before the rain and3.280m after. The maximum displacementof the slope in the Y-direction is-1.645m before the rain and-3.358m after.