Study On Stability Influence Of Multi-Step Slope By Rainfall Infiltration

The climate conditions in China are complicated and diversified,especially in summer and fall,and longer periods of heavy rainfall happen constantly. However,landslides are more likely to generate by a certain amount of time,which would give a significant threat to the constructions security. Given all this,it is of great practical significance to study the factors on stability of multi-step slope influenced by rainfall infiltration.Based on summarizing and absorbing the research achievements of the pioneer works in stability anslysis methods of slope, multi-step slope and multi-step slope by rainfall infiltration and relying on a high slope formed by excavating a offices project in Sichuan province, the influence regularities of the stability coefficients of multi-step slope on the bridleways and the lower/upper slope angle changing in natural condition and rainfall infiltration condition was deeply studied by means of the numerical simulation. Then the cohesive force and internal friction angle was discounted combined with the achievements which had been got before by means of the upper bound method of limit analysis in this paper, after that,the discount parameter can be used for count the stability factor and follow on two practical slope engineering which have been verified, At last, the stress state also has been analysed by the numerical simulation in the natural conditions. The major tasks in this thesis include:(1). Relying on a high slope formed by excavating an office project in Sichuan province, the location of the high slope were fully investigated. Then combining the geological survey information offered by the designing institution,a typical two-stage slope model was built,and the corresponding coordinated values of the bridleways and the lower/upper slope angle were set up.(2). The stability change regulation of multi-step slope was analyzed by means of Lizheng Geological Structure Designing and a recommended simplified formula respectively in the state of nature condition under different bridleways and lower/upper slope angle,the changing rule of,which all show that:reducing the lower slope angle will benefit the stability of multi-step slope a lot;at specified lower slope angle condition,the linear increase of the bridleways results in a linear increase of the stability of multi-step slope,however, once above a certain value, the multi-step slope is very likely to be slipped by local. In general, keeping the lower slope angle to a minimum,increasing restricted the bridleways will be favorable to the stability of multi-step slope.(3). The stability change regulation of multi-step slope was imitated by numerical simulation software“Geo-Studio”after longer periods of rainfall infiltration under different bridleways and the lower/upper slope angle, at the same time, the corresponding natural conditions has also been compared. Results show that:rainfall infiltration would significantly reduce the slope failure, the change of slip surface and pore-pressure, the types of potential slope failure(eg: the majority of rainfall infiltration conditions will be slipped by local).(4). The logarithmic spiral slip surface was Curve-fit using MATLAB which was based on the curve of slip surface in rainfall infiltration condition by numerical simulation,then the limit analysis upper bound method can be used for the function relationship between the reduction factor and the cohesive force and internal friction angle in rainfall infiltration condition, finally, two examples were used to prove the feasibility of the function relationship. Results show that:the idea of cohesive strength and internal friction angle reducing is feasible in equivalent-transforming between natural condition and rainfall condition.(5). The numerical simulation software “FLAC3D”was used to simulate the force situation in soil region,and the appropriate strengthening modes for multi-step slope has been introduced and some better suggestions has been given to the practical slope.The achievements of this thesis are very important for practical application of the Stability Influence of multi-step slope by rainfall infiltration, which will work for the designing, construction and treatment of the high and steep slope.