Experimental Study And Design Method Of Compressive Bearing Capacity Of Grouting Helical Pile

Because of its various forms,high bearing capacity,and its ability to be used in complex geological conditions,pile foundations have become increasingly widely used in the field of construction.As a new type of different pile,helical pile has many advantages,such as short construction period,green environmental protection,less site requirements and higher bearing capacity.In recent years,the application field of helical pile is constantly expanding,and it has its application scene in civil buildings,bridge foundation,subgrade construction,and building foundation reinforcement.However,the research on the soil strength loss and recovery around the pile after the installation of helical pile is relatively lack,and the design theory is not mature enough.In this paper,The vertical bearing performance and theoretical calculation of the helical pile after being screwed into the soil are studied,by both two methods,the pile static load test and the finite element numerical simulation.The main research is on the design parameters of spiral piles and the soil around the piles before and after grouting.The influence of strength on its ultimate compressive bearing capacity.The research results obtained are as follows:(1)According to the static load test,the grouting situation of the helical pile and the density of the helical plates are studied respectively.The vertical ultimate bearing capacity of helical pile is judged by the load displacement curve.The results show that grouting can significantly improve the ultimate bearing capacity of helical pile.when the number of plates increases,multiple displacement surfaces will be formed in the soil,causing the load-displacement curve to enter the excessively nonlinear section earlier,and the residual strength of the soil after failure less(2)Perform numerical simulation analysis on test data.After reaching the ultimate compressive bearing capacity,the bearing capacity factor under the helical plates of the helical pile after grouting is 1.6～2.0 times that of the ungrouting,which is 10.0～11.0;The load-bearing factor of the helical plate near the pile tip is 2.9-2.3 times that of ungrouting,which is 28-31;the strength of the damaged surface soil is 120%-160%of the original soil strength.(3)Numerical simulation analysis of the helical plate size of the grouting helical pile,the distance between the helical plate near the pile tip and the pile tip,and the helical plate thickness after grouting.It shows that the failure mode of the grouting helical pile is cylindrical shear model,and the failure surface is concentrated in the contact area between the soil under the helical plate and the soil around the pile.(4)Comprehensive test results,improve the original ultimate bearing capacity formula of helical piles,and obtain the ultimate bearing capacity calculation formula of grouting helical piles,and compare them with the test results and numerical calculation results,Verified the accuracy of the formula.