Research On The Calculation Method Of Stability And Nail Tension Of Soil Nailing Wall

As an important form of foundation pit support,soil nailing wall is widely used in foundation pit engineering because of its simple technique,fast construction speed and low cost.However,the lag in the research on the mechanism and design method of soil nailing often lead to unreasonable design and even engineering accidents.The limit analysis upper limit method is introduced into the analysis and computation of soil nailing wall.The overall stability,the form of failure,the development of the sliding surface and the distribution of the tensile force of the soil nail are analyzed.The results of computation are compated with the the results of other theories and field measurement.The factors affecting the adjustment coefficient of soil nail tension are analyzed by numerical simulation method.The main work and conclusions are as follows:(1)The overall stability failure can be divided into face failure,pullout failure and nail tensile failure,The factors affecting surface failure and pullout failure are analyzed by limit analysis.The safety factor of face failure and pullout failure is calculated.The results show that face failure may occur in some cases,so it is not appropriate that only the safety factors of pullout failure and nail tensile failure are checked in present design method.(2)Using limit analysis method,the development of the sliding surface is analysed.It is pointed out that there are two forms of sliding surface:slope bottom surface and slope foot surface,and the significance of two forms of sliding surface in practical engineering is discussed.(3)A method based on the plastic limit analysis method and unbalanced power distribution to calculate the axial force of soil nail is developed,and the computation results show good agreement with the results of the field measurement.(4)The computation results of FLAC3 D shows that the adjustment coefficient of soil nail tension will be affected by the slope angle,the overload at the top of the slope,the strength of reinforced soil,and the strength of foundation soil.