| With the continuous improvement of China’s economic level and the accelerating process of urbanization,the foundation pit project has been greatly developed,researchers are trying to find a safer,more convenient,and more affordable way to carry out foundation pit support design.which includes the continuous promotion and gradual maturity of the application technology of soil nailing,soil nailing support has received more and more advantages due to its advantages such as simple process,rapid construction,and remarkable economic benefits.Designers love it.However,soil nailing also has its own limitations.For the currently applied soil nailing technology,most of it is aimed at soil layers with good self-reliance;and for sand pits,There are few cases of soil nailing because there are two major problems: First,it is not easy to form pores in the sand layer,and the normal construction of soil nails cannot be ensured;second,the calculation of the ground is based on the cohesion of the sand layer as zero.The pit is unstable.This has seriously affected the engineering application of soil nailing technology in the sand field.Sands do not have cohesion under dry and saturated conditions,but they exhibit properties similar to clayey soils under unsaturated conditions.In this paper,by controlling the moisture content of this single factor,through the triaxial test,direct shear test and supplemented by the matrix suction test to study,to obtain the sand-like cohesion force value,and its change with the moisture content;When the dry density is 1.511g/cm3 and the moisture content is 6%-9%,it seems that the cohesion force reaches the maximum value and can reach up to 10 kPa.In this paper,apparent cohesive of sand is introduced into application,starting with the porosity of sand,the stability analysis of the small diameter cavern of the non liner unsaturated sand is carried out,and based on the example of Foundation pit support in the energy Finance mansion,the numerical simulation and analysis of the flac3 d and the excavation and support of the whole pit are carried out.The value range of cohesive force for pore stability of sand formation is obtained,as well as the variation of axial force and displacement of soil nailing in the whole excavation process.With the help of the software of Flac3 d and Li Zheng Deep Foundation Pit,the calculation and analysis of the influence of different cohesive force values on the deformation and stability of foundation pit are carried out,and the actual value of the cohesive force in the soil stratum of the foundation pit is obtained by contrasting the monitoring data in the field,to illustrate the reliability and the feasibility of soil nailing in sand stratum application.Finally,the design of the foundation pit of Xi-an energy finance mansion is optimized by the application of the apparent cohesive force value.The research results of this paper can provide reference for the related practical engineering design and construction,and have certain reference value for the future analysis and research on sand-like cohesion. |
