Strength Of Cement-Soil Composite Pile Ultimate Bearing Mechanism Model

With the development of economy, the construction scale expands unce asingly, because of the requirements of bearing capacity, geological conditio ns, the cement soil pile single always can not meet the engineering require ments, so the development of the cement soil pile to the combined pile, st iff cement soil composite pile is one example. The national strength of soil-cement composite pile earlier in Japan, Southeast Asia, in our application is in the late nineteen eighties. In recent years, research of stiff cement soi1composite pile in China is increasing.Stiff cement soil composite pile is before the cement soil pile of initia1set, the core pile squeezed to cement soil pile by mechanical, cement soi1pile until after solidification, model pile core pile and cement soil share the load. Because the core pile and cement soil stiffness ratio, the strength of the cement soil causes low, cement soil cohesive force cannot make th e core pile effectively play the full role.This paper puts forward this conce pt of stiffened cement soil composite pile。It refers to the cement slurry a nd soil stirring equipment or jet equipment fully stirred to form cement soi1pile, inserted core pile and hoop combination of materials, form a pile w ith high strength. Stiffened cement soil composite pile stress characteristics is the core material and cement soil pile to bear vertical load, with the ho op material to improve the adhesive force and the constraint of cement soi1horizontal direction between the core pile and cement soil deformation, s o as to improve the bearing capacity.The geogrid has high strength, good occlusion effect between soil and geogrid, good flexibility, and the advantages of simple manufacture, conve nient transportation, the geogrid as hoop material.In this paper, through the3cement soil pile model,6reinforced ceme nt soil composite pile model and6stiffened cement soil composite model pile static load test, the model of the ultimate bearing capacity of pile, Q-S curve and stress-strain curve. Study on bearing mechanism limits using t he empirical formula method, static load test method, gray prediction meth od and the finite element analysis method of stiffened cement soil composi te pile model, the results are as follows:(1)Analysis of bearing capacity of6reinforced cement soil composite pile model and6stiffened cement soil composite pile model, experimental results show that:stiffened cement soil composite pile four core pile (this paper core pile for four reinforced) from the pile distance is40mm, the so il grille with obvious, reinforced cement soil composite pile model with th e same parameters as compared to the ultimate bearing capacity is increase d by12.5～12.7%. Four reinforced but stiffened cement soil composite pil e away from the pile distance is20mm, the geogrid is not obvious, reinfor ced cement soil composite pile model with the same parameters as compar ed to the ultimate bearing capacity is increased by0.4%～2.5%.(2)Through the static load test for3cement soil pile model,6reinfor ced cement soil composite pile model and6stiffened cement soil composit e model of ultimate bearing capacity of pile data, and refer to the research results of scholars at home and abroad, puts forward the calculation form ula of bearing capacity of stiffened cement soil composite pile limit, the fo rmula is as follows: N,=0.587mAft+0.263(1-m)fcu+0.949filiAnd coefficient of the regression analysis on the effectiveness of geog rids, the correlation coefficient R2=0.934.(3) Based on the grey GM (1.1) model of stiffened cement soil pile composite model to predict the limit bearing capacity, the stiffened cement soil composite model pile using new iterative GM model compared to the new information GM prediction model and unequal step GM prediction mo del has higher precision of ultimate bearing capacity. Thus, although the pr ediction of ultimate bearing capacity prediction has certain reliability model of stiffened cement soil composite model pile, but still with a new iterati ve GM (1.1) model is the optimal model of stiffened cement soil pile com posite model.(4) Using ANSYS software program to finite element analysis of stru cturecement soil composite pile model and stiffened cement soil composite pile model of stress and strain, The conclusion can be drawn that the geog rid addition can improve four overall, the decrease of core pile to avoid th e phenomenon of stress concentration stress, and change shape from the ce nter outward gradually increasing trend, especially the core pile away from the pile distance, the effect of geogrid significantly, this conclusion is con sistent with test.