Study On Settlement Of Deep Soft Soil Composite Foundation

Soft soil is widely distributed all over the world.If it is not treated directly as engineering foundation,there will be problems of excessive settlement and insufficient bearing capacity.How to effectively treat the soft soil foundation is a common problem in geotechnical engineering.The common soft soil foundation treatment measures include replacement and filling method,drainage consolidation method and cement soil mixing pile method,etc.reasonable selection of treatment scheme according to local geological conditions is the key to ensure foundation stability.Based on the foundation treatment project of Bogota Metro Line 1 depot,through the methods of geological data analysis,indoor model test and finite element analysis,under the premise that the foundation treatment scheme is cement soil mixing pile + geocell flexible raft foundation,the reinforcement effect of the treatment area and the influencing factors of composite foundation settlement are studied.The main research contents and achievements are as follows:(1)According to the geological data,through comparison,the scheme of cement soil mixing pile + geocell flexible raft foundation is selected,and the specific scheme is put forward.(2)The indoor model test is carried out to simulate the settlement deformation of composite foundation under load.In the process of the test,through a series of proportioning tests,the proportion of model soil suitable for this test is obtained,and it is proved that the combination of quartz sand,barite powder,calcium carbonate powder and paraffin oil can better simulate soft soil.(3)The finite element software is used to model and calculate the model test,and the results are in good agreement with the model test,which verifies the correctness of the model test and the rationality of using the finite element software to carry out this kind of analysis.(4)The influence of pile length,pile diameter and cushion modulus on the settlement value of composite foundation is studied by using finite element software.It can be seen that increasing pile length,increasing pile diameter and increasing cushion modulus can effectively reduce the settlement value of composite foundation,but there are certain limits.With the increase of pile size and cushion modulus,the effect of reducing settlement value of composite foundation is worse.(5)Through the calculation of the settlement value of the rolling stock section area of Bogota Metro Line 1 by the finite element software and the standard method,it can be seen that the scheme of cement soil mixing pile + geocell flexible raft foundation can improve the foundation in this area,the settlement value of foundation is obviously reduced,and the post construction settlement and annual settlement value meet the engineering design requirements.(6)The initial design scheme of composite foundation is optimized,and the optimization scheme is given.