Study On Safety Control Of Subway Shield Tunnelling Building And Structures In Soft Soil Stratum

In this paper,based on suzhou rail transit line 2 project,in view of the shield crossing 570 building engineering,through high-speed railway engineering,cutting through 14 root bridge of large diameter pile foundation engineering,integrated the material research,theoretical analysis,finite element simulation,field test and engineering research means such as field measurement analysis,want to build a set of subway shield tunnel through building safety control theory and technical measures.The major contents and achievements of the study are as follows:(1)In the powdery sand strata,the longitudinal influence of shield tunneling is:15m in front of the blade plate and 25m behind the tail of the shield.The transverse sedimentation tank is more consistent with the peck normal distribution.The settlement rule of soil layer is:the settlement value above the tunnel is the largest,the higher the settlement value,the lower the settlement value.For the soil layer on the side of the tunnel,its settlement value decreases with increasing depth.(2)Using theoretical calculation method,the mathematical relation of the increase of shield gap caused by poor shield configuration is calculated,which can provide guidance for the dynamic adjustment of synchronous grouting.According to the geological conditions of the weak powdery sand in suzhou,a new type of synchronous grouting slurry has been developed,which is good in injection and filling,moderate in strength and not easy to block the pipeline.A new kind of foaming agent which can adapt to the soft soil layer of rich water is developed.Its permeability,fluidity and internal friction Angle are good,and the effect of the application in field practice is also good.(3)Considering that the conventional grouting reinforcement scheme cannot meet the requirement of crossing high-speed rail,this paper proposes a new structure type and protection system based on the idea of isolation protection.The paper also points out that,when the field project is carried out,it is necessary to strengthen the grouting under the protection plate.(4)The train dynamic simulation model of the impact of security protection board was established,without considering the protection plate at the bottom of the bearing capacity of soil under the premise of calculation show that the design of protection plate can meet the requirements of specification of calculating the fatigue strength.Under the condition of train load,the paper analyzes the principle of soil dynamic stress diffusion.Considering the impact of train load,the paper suggests that the structure of shield tunneling should adopt deep buried pipe in the section of high-speed railway.(5)A new type of cutter can be used for continuous cutting reinforced concrete pile foundation.Considering of shield machine cutting pile foundation may encounter risks,paper puts forward a set of contains all kinds of cutting tool cutter disc assembly scheme,positive shells are installed on the knife dish knife,knife edge shells,center small seashells,copying shell knife,alternate cleat cutting knife,etc.(6)In initial hole in front of the shield cutting reinforced concrete pile foundation field test,analyzes the cutting cutting reinforced effect in the experiment effect,cutting tool,cutting concrete damage,cutting parameters and so on.The problem of the experiment is further optimized for the tool configuration.In this paper,a set of core control techniques for continuous cutting of large diameter pile foundation is presented.