Settlement Method For Calculating Pile-soil Stress Radio Of Rigid Pile Composite Foundation

In recent decades, rigid pile composite foundation as a kind of effective means of dealingwith the foundation gets a wide range of applications and obtains good engineering results inthe construction foundation and road engineering, etc. But its working mechanism ofreinforcing soft soil foundation, especially for the interaction between gravel cushion, rigidpile and the pile soil, loads the bearing capacity mechanism and the load sharing mechanisminto full play, is short of an indepth study. Its corresponding theory study is not perfect enough,and its structure is varied. The mechanism of each component is complex, so it is difficult toaccurately get soft soil geological survey data. The theoretical calculation value andengineering measured values have bigger difference, not to satisfy the development of theengineering practice of the theory achievements. So this article combined with the nationalnatural science fund project " some material of composite foundation bearing mechanism andaccording to the theory of deformation control design research". From the aspects of modeltest and theoretical study, the calculation of pile soil stress ratio of composite foundation withrigid pile was improved.Firstly this article summarizes the development of composite foundation at home andabroad, especially for the development of the rigid pile composite foundation, and morecomprehensively expounds the strengthening mechanism of rigid pile composite foundation;Then it introduces the general failure mode of rigid pile composite foundation and calculatingmethod of current carrying capacity; And then it summarizes the method for calculating thepile soil stress ratio at home and abroad, and discussed the advantages and disadvantages ofeach in the meantime. Finally, on the basis of the existing calculation of the stress ratio ofpile-soil, there were three problems to be solved in view of the rigid pile compositefoundation design: one is the determination of the stress ratio of pile-soil; the second isconsidering pile up fashionable settlement calculation problem; three is how to consider theeffect of pile group effect.Then based on the elastic theory, the pile composite foundation of pile body and soil is asa line of elastomer. Pile and soil under pile cap is regarded as composite pile. According to theequal displacement of pile and soil in the center, by the static equilibrium and deformationcoordination conditions on elastomer border without considering pile side friction with depthchange the formula of pile-soil stress ratio of rigid pile composite foundation is deduced.Under the same load and the replacement rate, compared the different loading plate sedimentation, the settlement of single pile is bigger than the settlement of pile group valuesfrom the calculation results. The calculation of pile soil stress ratio is need to consider theeffect of pile group effect.Finally this article takes the pile unit and the soil unit for force analysis, and the basicdifferential equations were established. The equivalent stiffness coefficients of the pile andunit thickness of soil around each pile were developed, taking into account the pile groupeffect and the interaction between pile and soil through the load transfer method. Based on therelation among pile-soil-cushion and boundary conditions, the pile-soil stress ratio and theinfluence of important parameters were obtained. In the meantime, the pile group effect andthe soil lateral pressure were taken into account in the proposed method. The pile-soil stressratio calculated agrees well with those measured from the model test of pile foundation,showing the rationality of the approach and having some guiding significance in theengineering practice.