Study On Reinforcement Of Soft Soil Ground By Vacuum Preloading Method

Vacuum preloading method is an effective method in consolidation the soft soil foundation,which has been widely used in port,airport,highway and other fields.Many researchers and engineers have done a lot of work on the consolidation theory and results using the vacuum preloading method.However,the study of the reinforcement effect in consolidation the soft soil foundation using vacuum preloading method is little.Based on the existing research,the reinforcement of soft soil foundation by vacuum preloading method has been studied in theory,numerical simulation and the artificial neural network.The consolidation theory in the aspect of soft soil foundation by vacuum preloading method mainly originates from the consolidation theory of vertical drainage soft soil ground.As the calculation model,single well model is a Merchant model,which has viscoelastic material property.The effect of viscoelastic parameters and vacuum attenuation coefficient on average pore pressure and consolidation for the analysis was studied by the mathematical programming software.The conclusions could be described as followings: with the increases of vacuum attenuation coefficient and viscoelastic parameters,the consolidation rate decreased and the average pore pressure increased at the same depth.The parameters had more obvious influence on average pore pressure rather than average degree of consolidation.The reinforcement effect in consolidation of the soft soil foundation in Q2 is monitored,which is the vacuum preloading treatment area in Tianjin port economic zone.Based on the theory of Biot,vacuum preloading was simulated by using FLAC3 D finite difference software.According to the equivalent permeability coefficient,the simplified plastic drainage plate is calculated into the natural foundation in the simulation process.The variation of the soft soil foundation pore pressure and vertical settlement had been studied.The dissipation of pore water pressure promoted the reduction of effective stress of soil,and the soil consolidation settlement.The calculation results reach a good agreement with the experimentalresults.In this paper,the BP artificial neural network is used to predict the settlement and pore water pressure.Firstly,the data of settlement and pore water pressure of S2 are trained,which is used for deep vacuum preloading in Tianjin Port Economic Zone.BP neural network is reliable by training samples,for settlement and pore water pressure with the prediction.BP neural network is more stable in the prediction of settlement value,and is very close to the measured value.However,in the prediction of pore water pressure value,BP neural network has instability phenomenon.Individual predictive value of relative error up with the measured,indicating that BP neural network can be used for engineering to predict,but requires professionals to predict the settlement and pore water pressure during the process,in order to ensure the reliability.