Back Analysis Of M-value Of Soil In Foundation Pit

In foundation pit engineering,due to the plane vertical elastic foundation beam method has clear computation mode and simple calculation process,it is widely used in practical engineering.The horizontal reaction coefficient of soil—m value is very important,it not only affects the deformation and internal force of retaining structure,but it also determines the design of support structure and the choice of enclosure program.Being limited by experimental conditions,the present engineering survey reports can not provide the horizontal bedding coefficients of different soil layers correctly.Although the existing procedures and guidelines has given the reference value,but there is a wide range for choosing the m value,it is uncertain and random.Accurate and reasonable m value not only reflects the actual working state of the structure,but also provides reference for similar engineering design,which has important engineering significance.Based on the measured horizontal displacement monitoring data,this paper uses reciprocal analysis of the spline function and the positive analysis of the elastic fulcrum method to invert the equivalent m values of the foundation pit.Research works are as follows:(1)Based on assumptions and simplified calculations,the horizontal reaction coefficient of soil is analyzed by the elastic fulcrum method,and then get the related coefficients ?1??2,presented an equivalent m-value formula which includes soil gravity ?,excavation depth h,side pressure coefficient k0 and shear strength index.(2)According to certain smoothing criterion and approximation criterion,smoothing spliine function is used to smooth the horizontal displacement monitoring data is.Then,use B-spline function to interpolate the smoothing data to obtain the displacement spline function,differentiate it,back-calculate the force of foundation pit support.(3)The mechanical calculation model is established according to the elastic fulcrum method of plane bar structure,the matrix displacement method is used to calculate the deformation and internal force of foundation pit supporting pile.(4)As the back analysis parameters,?1??2have a large number of combinations of parameter which is enumerated within its range of values,put them into the positive analysis model to calculate,the deformation and internal force of the support pile corresponding to each combination is obtained.Use the actual deformation and back analysis of the internal force as a constraint,filter the parameters corresponding to the positive analysis values within the allowable tolerance range,so?1??2 are determined,and then use back analysis to obtain the equivalent m value indirectly.(5)Select an actual project,in accordance with the back analysis method for the inversion to determine the coefficient of ?1??2,and calculate the m value of foundation pit soil in next condition,put it into the mechanical calculation model of the foundation pit,get the deformation and internal force of the next condition of the foundation pit support pile,compare them with the actual value of the displacement and the internal force inverse,verify the reliability of the inverse analysis results and the feasibility of the inverse analysis algorithm.