Study On The Anti-mining Deformation Performance Of Cement-Soil Pile Composite Foundation

In this paper,the composite foundation of cement-soil pile in mining area is taken as the research object.Through triaxial test in laboratory and numerical simulation,the variation law of mechanical properties parameters of composite foundation of cement-soil pile in mining process is studied.The influence of the change of pile strength and foundation soil strength on the anti-mining deformation performance of composite foundation of cement-soil pile is analyzed,and the bearing capacity of composite foundation of cement-soil pile in mining area is put forward.The recommended value of eigenvalue reduction coefficient.The main research contents and conclusions are as follows:（1）Based on similarity theory,a similarity model of cement-soil pile composite foundation is established.The mining process is simulated by lateral unloading and lateral loading tests,and the variation of equivalent cohesion and internal friction angle of cement-soil pile composite foundation during mining is studied.The test results show that mining mainly affects the soil between piles,but has little effect on the cement-soil pile,and the pile body does not damage.The equivalent cohesion of cement-soil pile composite foundation decreases and the equivalent internal friction angle decreases first and then increases due to mining.（2）Based on the process and results of triaxial test,the lateral unloading and lateral loading process under the combination of different cement-soil pile body strength and different foundation soil strength are simulated by ANSYS finite element software,and the variation law of equivalent cohesion and equivalent internal friction angle of cement-soil pile composite foundation is studied.The results show that under mining disturbance,the higher the cohesion of soil,the smaller the reduction of equivalent cohesion of cement-soil pile composite foundation,the higher the strength of pile body,and the smaller the reduction of equivalent cohesion of composite foundation.（3）Based on the comprehensive analysis of the results of laboratory tests and numerical simulation,it is proposed that the eigenvalues of bearing capacity should be reduced in the design of cement-soil pile composite foundation in mining area,and the recommended value of reduction coefficient is:when 200kPa<f_kz≤300kPa,the reduction coefficient is 0.88,When 300kPa<f_kz≤400kPa,the reduction coefficient is0.90,and when f_kz>400kPa,the reduction coefficient is 0.95.