Cfg Pile Composite Ground Kiki Bed Coefficient And Its Applications

How to determine the coefficient of composite subgrade reaction is a necessary problem that engineer must to face, when they design building foundation using elastic foundation model. But, the codes for design of composite subgrade have not clear rules specify about this. So, This is a problem that calls for immediate solution in engineering design.By analysis the mechanism of CFG pile composite subgrade, Winkler subgrade model, and the definition of the coefficient of subgrade reaction, and the method of determining the coefficient of natural subgrade reaction at present, The authors hold one method of determine the coefficient of CFG pile composite subgrade reaction is using the method that code recommended to calculate composite modulus, calculating the deformation of subgrade afterward, then inverse calculating the coefficient of CFG pile composite subgrade reaction. Another method is using the p-s curvilinear figure which got by static test, directly calculating the coefficient of CFG pile composite subgrade reaction.In order to verify the dependence of two methods, author selected seven actual projects in zhengzhou with differ region, differ geological condition and differ pressure of foundation bottom, detailedly described the general situation of projects, the geological conditions and primary parameters of CFG pile composite subgrade design, then calculated the coefficients of CFG pile composite subgrade reaction of them through two methods. Also made use of the result of settlement observation of three actual projects, calculated the coefficient according to the definition of subgrade reaction, and compared them with the result calculated through two methods. Through comparison, it can be found that the result acquired by using composite modulus inverse calculating the coefficient of subgrade reaction have a great deviation with the date that practically measured, and the result acquired through static test have a approximate scaling relation with the date that practically measured. Through analysis, the author consider that the method using composite modulus inverse calculating the coefficient of subgrade reaction is not dependable, the result of the coefficient of subgrade reaction acquired through static test can be used by necessary corrected. According to statistic data of actual project, approximate span of the coefficients of CFG pile composite subgrade reaction be offered, it can be referenced in design of local project.During the course of research, the author made a long-term trace test in one of the actual projects, measured and analyzed the stress in pile and soil, made a exact settlement observation, and measured the stress of the steel bar in foundation, then gave some suggestions in design of raft foundation on CFG pile composite subgrade.