Application Research Of CFG Pile In Foundation Treatment Of Ballastless Track In Metro Parking Lot

Ballastless track,as a structure that directly affects the carrying vehicles in the subway parking lot,has limited geometric adjustment capabilities of the track system structure.Therefore,it is necessary to strictly control the settlement of the roadbed.In this paper,relying on the foundation treatment project of the ballastless track bed in Chengdu Huilong parking lot,by analyzing the effect and dynamic response of the CFG pile composite foundation,the on-site inspection test of the CFG pile composite foundation project,and using ABAQUS finite element software to establish a three-dimensional analysis of the CFG pile composite foundation The numerical model simulates and analyzes the settlement and internal stress distribution of CFG composite foundation,analyzes the reinforcement effect of CFG pile composite foundation,the bearing capacity of pile composite foundation and the settlement law of pile composite foundation.The following main research conclusions are obtained.1.When the load on the local foundation is small,the load ratio of the CFG pile is smaller than the load ratio of the soil,and as the load increases,the load carried by the pile gradually increases as a percentage of the total load,and the pile bears the load The load as a percentage of the total load gradually decreases.Through the comparative analysis of the thickness of the cushion layer,it can be seen that when the cushion layer is 300 mm thick,the pile-soil sharing ratio is close to 1,which can enhance the bearing capacity of the soil body and at the same time reduce the soil settlement.2.From the static load settlement test of the composite foundation with different pile lengths and different pile spacings,it can be concluded that when the maximum load is 302 k Pa,the cumulative settlement is between 14.52 mm and 10.86 mm,and the settlement difference is within 5 mm.The rebound amount is between 2.33 mm and2.13 mm,and the rebound rate is between 15.3% and 19.6%.It shows that the working state of CFG pile composite foundation is that pile and soil act together as a whole to bear the load together.3.The p-s curves of the four CFG pile composite foundations(pile lengths of 5.4m and 6.2m,and pile spacing of 1.2m and 1.6m)have the same changing trend of p-s curves,and the slopes of the curves are close to parallel,indicating that the pile materials are roughly the same.Through the comparison test of the two sets of piles with the same spacing and different pile lengths,it can be found that the smaller the pile spacing,the more significant the control of the pile length on the settlement change of the composite foundation,and the longer the pile length,the smaller the settlement change.The greater the pile spacing,the greater the settlement.4.The finite element simulation analysis results show that the influence trend of pile length and pile spacing on the settlement of composite foundation is consistent with the measured results.And the error between the simulation result and the actual measurement result is small,indicating that the established model has high accuracy.Through the established model to simulate the dynamic load generated by the train,the bearing capacity characteristics and settlement of the CFG pile composite foundation are analyzed,and it is concluded that the CFG pile composite foundation meeting the design requirements under the static load test can withstand the dynamic load generated by the train.The results of the thesis have reference value for the design and application of CFG pile composite foundation.