Key Techniques For ∏ Type Underground Continuous Wall Construction Of Entry And Exit Of Shield Tunneling Terminal

In the construction of shield tunnel of urban subway,the operation of shield machine in and out of the tunnel is complicated and the construction is dangerous.Compared with the excavation of shield tunnel,its construction process is very important.As each step of the shield machine in the construction process of the tunnel in and out of the tunnel is very critical,a little negligence may cause a series of problems,such as water and sand gushing of the portal,soil subsidence at the end of the tunnel,damage of the upper buildings and pipelines,runaway of the head and instability of the shield machine,and so on.The method of soil reinforcement at the end of shield tunnel,the selection of construction technology and the accurate prediction of reinforcement effect are the key technical points to ensure the starting and arrival of shield tunnel can be controlled,economical and safe.The construction technology of shield inlet and outlet tunnel is studied in this paper.Based on the authorized invention patent,a construction method of shield in and out of tunnel,this paper first summarizes the reinforcement method of tunnel end and the technology of shield tunnel entry and exit when shield is in and out of the tunnel;then introduces the working principle and concrete construction process of the new shield tunnel construction technology;next analyzes qualitatively the influence of different deflection direction of the wing wall of II shaped ground connecting wall on the reinforcement effect through the indoor model test;numerical analysis is carried out on the reinforcement effect of shield tunneling in and out of the tunnel,and through the study of stress field and displacement field,the law and effect of the action of the wall wing wall are obtained.Thus,the theoretical analysis of the mechanical behavior of the method is further improved,and the practical value and practical significance of the technology are verified.The main work of this paper is as follows:1)Summarize the common ways of the entry and exit of the tunnel of shield machine,and expound the new innovative reinforcement methods that appear at present.Besides,contrast and analyze the excellence of the technology of the tunnel in and out of the shield machine in common use and get the unique superiority of the end soil reinforcement of the∏ shape ground connecting wall.2)The working principle of the tunnel in and out of the shield machine is systematically discussed,and the construction materials,technical principle and technological process of the construction technology of the tunnel in and out of the tunnel with the wall connecting the wall with the wall in the ∏ shape are introduced in detail.3)Analyze the influence of different wing wall deflection angle on the support effect of shield tunnel under two different conditions:small displacement and large displacement by taking the indoor model test.Summarize and conclude the regulation.The results show that the wing wall deflection angle has little effect on shield tunnel entry and exit tunnel support effect under small displacement;while in large displacement,wing wall angle deflection has a very significant effect.4)Numerical analysis software MIDAS/GTS NX is used to simulate shield in and out tunnel under dangerous working conditions.The effect of wall wing wall on shield in and out tunnel is confirmed,and the reinforcement effect of different wing wall length on the end soil of tunnel is further compared.The reasonable length range of wing wall in shield tunnel is obtained.The force law of wall connecting wall is discussed when the length of wing wall is different under dangerous condition.The results show that the reasonable length of the wing wall is about 6 m when entering the hole and 8 m when going out of the hole.5)By the numerical analysis on the inlet and outlet tunnel of the shield tunnel,it is concluded that the maximum settlement of the soil body at the end of the tunnel is only 3 mm when entering the tunnel and 5.4mm when going out.At the same time,the an analysis of the forces on the ∏ shape ground connecting wall is also made under different working conditions,which is beneficial to the reasonable arrangement of the GFRP bars in the tension area and provides the reference for the actual engineering.