The Study On Stability Of The Overlapped Rock Of Tunnel With Small Spacing And Overlapped

Along with the acceleration of urbanization process and the rapid development ofour country’s economy, the development and utilization of underground space aresubjected to people’s extensive concern. As a new form of structure, the tunnel withsmall spacing and overlapped is becoming more and more popular in engineering.However, because the overlapped section of the tunnel has the features of complexstructure, small spacing, and the construction process will lead to the repeated stressredistribution of rock and the changes of the stress state of the tunnel structure itself,so it is meaningful to concern about the variation of its mechanical behavior duringthe construction process.On the background of FuXia Highway extension project DaPingshan Tunnel, Thepaper will further study on construction mechanical behavior of the overlappedsection of the tunnel base on the research methods of combination of in-situ test andstatic finite element analysis. Some research fruits and conclusions are obtained asfollows:1. The general mechanic principle of closed–space construction of undergroundengineering is systematically introduced and the emphasis is on the variation and theimpact range of the overlapping cavity during the excavation.2. The deformation of the overlapping rock has strong characteristics of timedistribution, the main performance as follows: in the initial time the overlappingsection’s deformation amount is large, development is rapid, the duration is longer.Relative to the surrounding convergence, crown settlement can reflect the strain ofsurrounding rock more visually.3. According to the actual situation of DaPingshan Tunnel it established thethree-dimensional numerical model, verified the applicability of the numerical model,and summarized the mechanical response and displacement and deformation law ofthe overlapping surrounding rock and the two tunnels’ primary support structures.4. Based on the numerical analysis method, we analyze that the mechanical response and displacement and deformation law of the overlapping surrounding rockand the two tunnels’ primary support structures with the net distance changes whenoverlapped tunnels in orthogonal condition, the net distance is0.5D,0.75D or1D.