Strengthing Effect Analysis Of Side Friction Of Dry Jet Mixing Pile Composite Foundation By Finite Element Method

Engineering practice shows that,the side friction of pile will be strengthened when the pile interact with the soil in the dry jet mixing(DJM) pile compound foundation, however the strengthening mechanism has not be confirmed. In this paper, the strengthening effect mechanism and bearing capacity property of DJM pile are analyzed by the 2D-σfinite element software. The specific contents are as follows.1) The history and function of DJM pile composite foundation are briefly introduced, and the research situation of strengthening effect is generalized.2) The basal principle of finite element method is given. A model based on some project in HanDan city which is created by 2D-σsoftware is used to analyze the interaction of pile-soil. The load-settlement curve gained from the model is consistent with the field data then the validity of the model and the calculation parameters are confirmed.3) This article study on the bearing capacity property of DJM pile, explore the strengthening mechanism, disclose the law of the pile body axial stress transfer and side friction resistance distribution along the pile body and so on and analyze the relationship between the strengthening effect and the pile body strength, pile length, compression modulus of the earth at the pile tip and the load on the top of the pile. The results show that the friction resistance will increase about 20%-130% inside 2-5 times diameter of above the tip of the pile when the value of the compression modulus of the tip soil is greater and equal 9MPa. The shorter the pile length is, the higher the increasing extent will be. The conclusion is directive to the design of the compound foundation.4) Put the study results into the design of the dilapidated houses reconstruction. Consider the strengthening effect mechanism and the value of the friction resistance in the strengthening area should multiply the corresponding intensifying factor. The loading test shows that the strengthening area and the intensifying factor can satisfy the engineering needs when the value of the compression modulus of the earth at the pile tip surpasses a certain cost. It is beneficial.