Research On Settlement Control Of Soft Soil Foundation In Metro Depots

In recent years,construction of subway project are urgently needed in our country to meet the need of economic development and improve people's livelihoods.Metro depot is built for the operation,parking,locomotive servicing and maintenance of subway trains.To ensure the normal work of metro depot,the stability of related structure foundation and the control of post-construction settlement are strictly required.For metro depot built on the soft soil,it is particularly important to explore how to deal with soft soil foundation and control its post-construction settlement.Based on the related projects of Guangzhou metro depots,the author systematically analysed the reinforcement techniques of soft soil foundation under metro depots by literature review,theoretical analysis and field monitoring,and put forward the metro depot soft soil foundation reinforcement method and its applicable conditions.Combined with engineering example,further study was conducted by the numerical simulation.It could bring good effects on the control of the settlement by using curtains made up of deep mixing piles around metro depots.Main research contents and results are as follows.(1)The main influence factors of soft soil foundation under metro depot included thickness of soft soil,properties of soft soil,change of ground water levels,stress history,loads and loading rate,foundation reinforcement methods,lateral displacement,etc.(2)Soft soil foundation reinforcement methods on metro depot mainly included preloading method,deep mixing pile technique and high-pressure rotary jet grouting pile technique.For special areas,pre-formed pile technique and CFG pile technique were also used.(3)In the process of soft soil foundation reinforcement,there were three mainly problems including excessive settlement,selection of filling for preloading and selection of pile types.(4)The large finite element software ABAQUS could well simulate the process of settlement of soft soil foundation by using plastic drainage boards and preloading method and it had good practical value in engineering.Plastic drainage boards could accelerate the consolidation settlement of soft soil foundation,shorten the construction time and increase the strength of soft soil foundation.Meanwhile,through simulation comparison,it was found that plastic drainage boards could make ultimate settlement larger.(5)It could bring good effects on the control of the settlement by using curtains made up of deep mixing piles around metro depots on soft soil foundations.Numerical simulation model was established based on ABAQUS and different influential factors like pile length and number of rows were studied.Meanwhile,in the process of soft soil foundation reinforcement,construction cost should be well considered when to determine the pile length and number of rows.