The Research And Application Of The Scope Of End Pre-reinforcement Of Shield Construction Of Guangzhou Metro

Shield construction was widely used in the urban subway,electric power,municipal etcs construction of underground tunnel,as it has mang advantage such as:the high mechanization degree,the high speed and safety,the of little impact on the environment etcs. In the construction of shield tunnel,The construction of the Shield beginning or arriving is the key link of the tunnel construction.If the construction undeserved,it may take place such as landslides,floods,soil instability etcs safety problems.In order to avoid such as problems that may occur in the construction process of the shield beginning or arriving,it need to reinforce the end soil that to ensure the shield tunnel starting and through in a timely manner.This paper taking the Huadu square station~Ma’An Shan part(forshort Hua Ma section) of the Guangzhou track traffic on the 4th line as the engineering background of the subway tunnel,combining with the engineering practice,using the engineering experience, theoretical analysis and numerical simulation etcs methods,carrying on the analysis and research to the reinforcement method,the theory reinforcement and numerical simulation of the the end soil of the the departure of the subway tunnel shield beginning(Ma’An Shan park).Specific work content is as follows:(1) By practice in the subway tunnel engineering of HuaMa interval in Guangzhou rail transit, understanding of shield beginning project profile and the project of shield beginning reinforcement methods and construction technology, on this basis to understand the advantages and disadvantages of various end reinforcement method and its applicable condition, grasping the emphases and difficulties of the construction in the end soil of the shield beginning,in order to realize the subway tunnel shield beginning the effective control of engineering security;(2) On the basis of the classical strength theory, throughing establish the mechanics and mathematical model of the end soil, using the elastic mechanics,the higher soil mechanics and higher mathematics method to deduce the theoretical solution of the longitudinal and transverse reinforcement range of the end soil. and for the Ma’An Shan park station as the actual engineering conditions example analysis,in order to providing theoretical reference for the actual engineering construction;(3) Using the three-dimensions finite difference numerical simulation software FLAC3 D, in the shield beginning the door dismantling that is the most unfavorable conditions,starting from the displacement field and damage field, stress field to conduct numerical simulation,first ensure that transverse reinforcement range for 3m,length of longitudinal reinforcement scope in turn 3m,6m,10 m,15m to conduct numerical simulation to determine the reasonable numerical solution of the longitudinal reinforcement;and then guarantee the reasonable scope of longitudinal reinforcement constant,transverse reinforcement scope in turn shield on both sides of the 1m,2m,3m,4m range end reinforcement scope to conduct numerical simulation,to determine the reasonable scope of transverse reinforcement,further to provide reference for engineering construction and theoretical study.The main research results:(1)Ma’An Shan park station shield beginning engineering under high water pressure of sand layer, the soft hard strata,it has characteristics of the big permeability coefficient,the bad construction parameters control,the anti formation bearing capacity etcs.The threefold high-pressure jet grouting pile reinforcement method is suitable for sand,sand gravel, silt and soft clayey soil, etc, formed by jet grouting pile high strength,good durability,and its operation is simple, can be good,material source wide,price is low,and many other advantages,that can be applicable to the Ma’An Shan park station shield beginning engineering soil consolidation.(2) By the elastic thin plate theory,sliding instability theory of soil,soil disturbance, limit equilibrium theory and the structure of the end of the loose circle of related knowledge and reinforcement analysis, establish the corresponding mechanical calculation model, through the elastic mechanics knowledge, advanced soil mechanics and higher mathematics analysis method, deduces the theoretical solution of end soil consolidation scope, and will saddle the park station engineering instance for example analysis, The results show that compared with the actual reinforcement in the longitudinal and tunnel on both sides were similar, the tunnel arch bottom sand soil and arch bottom ash carbon calculation deviation along the soil layer, the main reason is probably not consider the actual geological conditions and strengthening the influence of such factors as soil;(3)By the numerical simulation results indicate: in consideration of different longitudinal and transverse reinforcement range of disruption field and displacement field, stress field and the shield originating check water requirements, according to the theoretical research results and practical engineering geological conditions, finally confirmed the project of shield starting end soil consolidation is: take 10 m longitudinal reinforcement length, the lateral reinforcement length 3m, take 5m depth direction for the tunnel roof reinforcement, tunnel under the center without reinforcement.As long as guarantee the construction quality, can meet the requirements of strength and stability of the shield originating;(4) This study for Guangzhou metro shield tunnel construction or other similar high water pressure of sand soil, the soft hard strata under the construction condition of engineering, which has some reference value and application promotion.