Study On Bearing And Deformation Properties Of Rammed Soil-Cement Pile Composite Foundation

Rammed soil-cement pile composite foundation possesses many characters such as cheap cost of fabrication, simple construction, controlling quality easily etc.. Rammed soil-cement pile composite foundation reinforce weak ground which have a lot of advantage and have already applied to the practice of projects extensively today.Rammed soil-cement composite foundation is originated in HeBei province recently. However the theory of rammed soil-cement composite foundation is dropped behind the practice of rammed soil-cement composite foundation .This results in the limitation of the development of rammed soil-cement composite foundation.So it is indispensable to investigate composite foundation in the abstract. It has been put high value and attention in geotechnical engineering. Based on in-situ test, a study and analysis was made on bearing action of rammed soil-cement composite foundation in the paper. A test on load distribution, pile-soil stress ratio, cushion action and deformation of rammed soil-cement composite foundation is performed.This paper will analyze the mechanical properties of reinforced ground by means of model of locale loading test and the application of finite element analysis software. The calculation results show that the method is practical and applicable. Also, it will consider the no-linear character of composite foundation. Some essential rules of the load distribution, cushion effects, deformation characters, stress field, strain field and the relation between the length of pile and settlement will be gained .These tests and analyses are valuable for the treatment of soft soil foundation in the neighborhoods of Hebei Province and Beijing.At last, some essential conclusions is drawn :1. The pile-soil stress of rammed soil-cement pile composite foundation is changeable constantly with the load course and there is a extreme value(n_max<6.1).The load of pile and soil grows with the increasing of the total load.When the total load p<310kN, the sharing load curves of pile and soil is straight lines and they will appear the flex point when the total load p between 300⁴00kN. The load that the body of piles share will be reduced suddenly and the piles will be yielded and destroyed.2. The deformation character of rammed soil-cement pile composite foundation proves that the compression deformation occurs in reinforced zone in low level of load.When the load is in certain level, the compression deformation of subjacent layeris come into being which is main factor of the settlement of the composite foundation.3. The methods of computing settlement and bearing ability of rammed soil-cement pile composite foundation are limited because the conditions of the building site is different and the surveying value has error in situ. And the errors can be reduced by choosing and regulating the design parameter appropriately through finite element analyzing software Ansys.4. The character of the strain of rammed soil-cement pile composite foundation is concluded as followrthe pile and soil is coordinated deformation and the strain deformation is settlement funnel in shape. The settlement funnel of the strain deformation becomes narrow in radial direction with the increasing of the total load and the strain of pile is increasing.The variation of the stress field is complex. The distribution of stress is homogeneous in low stress level.In general stress level, the ellipsoid stress zone is appearing in the upper part soil.The negative frictional resistance zone is turning up and it will disappear with the increasing of the load.5. Increasing length of pile can improve the bearing ability of composite foundation to certain degree, but the function of increasing pile length constantly is very weak to improve the bearing capacity. Engineering design need adopt rational and economic pile length The reasonable pile length(8¹0m) is suggested at last.