A Study On Reliability Of The Slope Protected By Soil Nailing

Soil nailed wall has been used widely for slope stability and foundation excavation in China, and it demonstrates a great deal of advantage and suitability. At present, safety factor method is adopted to soil nailing design and analysis. Because of the randomicity of physical mechanical property of soil is not considered, some soil nailed walls which are safe enough according to safety factors damage soon when they are put into use. Thus, if reliability analysis method was introduced into soil nailed wall design and analysis, a lot of damage could be decreased. Therefore, some scholars at home and abroad have done some work on introducing reliability method into soil nailed wall design and analysis. Based on the previous research, this paper conducted the following several aspects of research.(1) The random variables which affect soil-nail retaining structure's reliability were analyzed. The results show that inner friction angle of soil, unit weight, cohesion, interfacial bond strength, steel's yielding strength, etc., are random variables which obey normal distribution. According to reliability theory, performance function was established for strength failure and stability failure of soil nailed wall. The reliability index of every failure mode was computed by design point method in the first order second moment theory in structural reliability analysis.(2) Two failure modes pullout failure and tensile failure of soil nail were regarded as serial system. On the base of reliability index of single failure mode, the reliability index was computed by step-by-step equivalent plane method, and then the failure probability of single soil nail failure in every row also was computed.(3) Reliability calculation process of internal stability was simulated by Monte-Carlo method. Superior calculation accuracy of design point method was proved by error analysis.(4) About the sequence of soil nail failure, internal force redistribution of many super statically determinate structures, was set up by the deformation compatibility of panel. And then taken a actual engineering for example and used the calculation model to find main path of soil nail failure.(5) The influences of the soil nail arrangement and design parameter on soil-nail retaining structure's reliability were discussed based on a actual engineering. Thus the results can be referenced for engineering design.