Experimental Study On Pile Bearing Capacity Of Natural Ground Test Of Deep Excavation Engineering

Because normally the pile foundation grade of some high-rise buildings is class A,pile test is needed in the early stage of the project.In order to save a lot of time and cost,pile test is needed on the natural ground,to provide design basis for the design unit.In order to solve such engineering problems,in this paper the bearing capacity of foundation piles based on natural ground test is researched,combined with a specific project,engineering experience is accumulated for future pile tests,and experimental conclusions with certain practical significance and value are summarized.The bearing capacity and the failure mechanism of piles and the vertical bearing capacity test method is summarized systematically in this paper.Base on discussion and analysis,the conclusion is as follow:vertical compression static load test should be selected first,in testing the pile bearing capacity.Self-balanced static load test should be chosen,when the test is limited by the conditions of the site and the loading capacity of the equipment,but the influence of the elastic compression deformation of the pile and other parameters on the final result should be considered.According to the specific conditions of a comprehensive building,according to the test purpose,the conditions of rock and soil and the requirements of design for pile test,the pile test plan is developed,and tests it practically.The test data is successfully collected,and the vertical compressive bearing capacity of the test pile is determined.Then the pile of the comprehensive building is tested by static load test,and the following conclusions are drawn through the analysis of the test data processing:(1)the test results show that the reinforcement coefficient of the grouting side resistance is 2.6,and the stiffness of the pile and soil is greatly improved.(2)test results show that the small settlement of 38%ground test pile settlement than in the pit bottom test pile,the main reason is the excavation pit test,pile lateral soil due to the loss of upper soil,stress changes,unloading springback,consolidation degree of small,small to change the friction resistance and the test on the ground with a covering effect,resulting in larger relative displacement between pile and soil.(3)the location of engineering pile is different from that of foundation pit,and the settlement deformation is different.When the engineering pile is near the middle part of the foundation pit,the static load settlement and deformation is larger than that of the engineering pile near the foundation pit.(4)when the natural ground test of deep foundation pit is used to determine the bearing capacity of the test pile,the effect of the effect of the overlying soil on the invalid section should be considered according to the specific conditions.For destructive static load test,we should carefully analyze and deal with the data based on the test data,and consider the situation that the side friction reduction of the effective section will be reduced if the invalid section is covered,so as to avoid the insufficient or excessive deformation of the bearing capacity of the engineering pile.(5)the results of numerical simulation show that there are very little differences between the two working conditions of the ground test pile bearing capacity,the elimination of lateral resistance measures and the elimination of lateral resistance measures.The same pile length under the condition of foundation pit depth,ground test and test pit difference of two conditions more.The same excavation depth,pile length,different ground tests and test the bottom two conditions more.Finally,this paper analyzed the similarities and differences of the pile settlement,internal force of pile body and pile side resistance,under two different kinds of load condition through the finite element numerical simulation software ANSYS.The numerical results are basically consistent with the test results.