| With the rapid development of urban rail transit,subway lines are criss-crossed,and new subway tunnels will inevitably encounter the problem of going up or down existing tunnels at short distances.How to predict and control the impact of shield tunnel construction on existing tunnels and ensure the normal operation of subways has become a hot and difficult point in underground space development.However,the current urban construction is developing rapidly,and academic research often lags behind the needs of engineering.Therefore,the existing theories and methods are often insufficient to guide engineering construction.Among them,the construction control theory and technology under the condition of close-range or even ultraclose-range is a typical situation.In this paper,the shield tunnel from Xinyuan Road station to Dongcheng South Station of Dongguan Metro Line 1 crosses the existing Dongguan-Huizhou intercity tunnel project with a small clearance distance,and adopts the methods of numerical simulation calculation,monitoring data analysis and field test to study the control technology of the influence of the minimum distance construction on the surrounding environment.The main research contents and results of this paper are as follows:(1)The law of stratum settlement and stratum loss of the interval shield tunnel is analyzed,and the applicability of Peck formula is analyzed.The stratum loss rate of the interval is0.067%～3.24%,and the relationship between various factors and stratum loss rate is discussed.(2)the selection and the cross section of the similar geological conditions,pre tunneling experiment by adjusting the driving parameters to control the surface subsidence,get across the period of construction excavation parameters of reference,and then through the numerical simulation of strata displacement of the cross section on the study of the lower both the influence law of the tunnel,the parameter selection for the construction of the cross section on provided the scientific basis,It plays a role in the smooth construction of the upper span.(3)In order to maintain the stability of the stratum and limit the stratum displacement during the period of shield machine shutdown,warehouse opening and cutting historical anchor cable,the foundation in the cutting area of anchor cable is reinforced by grouting.In this paper,numerical simulation method is used to study the effectiveness of removing anchor cables and grouting reinforcement.The results show that,compared with the condition without grouting reinforcement,the settlement of the stratum after grouting reinforcement decreases by about40%.It can be seen that the grouting reinforcement of the stratum has a significant effect on controlling the surface settlement.At the same time,it is found that the grouting reinforcement in the shallow part of the foundation has little influence on the displacement deformation of the lower tunnel.(4)research in the past about shield machine vibration caused by the spread of the vibration acceleration and its related literature,to formulate the appropriate source of vibration acceleration time history,through the dynamic finite element calculation,the cross of shield construction on close to lower both the effects of the vibration of tunnel and vibration propagation characteristic,combining has been operating metro tunnel vibration measurements,It is considered that the vibration of the upper span shield machine has little influence on the vibration of the short-distance underpass tunnel. |
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