Study On Excavating Surrounding Rock Deformation Characteristics Of Near Reservoir Shuiniujia Tunnel

This dissertation relies on the monitoring measurement project of Shuiniujia No.1 tunnel(right next to the reservoir) of Sichuan Provincial road S205. The deformation laws of surrounding rock which belongs to the typical IV, V grade rock section and the large deformation section are analyzed combined with the measured data; analyze the reasons causing the deformation of Shuiniujia No.1 tunnel surrounding rock combined with the geological and hydrological factors; study the characteristics and laws of the asymmetry of surrounding convergence; analyze the effect(deformation) of the hydrostatic pressure and the softened rock mass on the right side of tunnel because of water on the tunnel surrounding rock when the reservoir level is the highest, finding out the direct cause of the convergence asymmetry by comparing three operating conditions; analyze the law of stress and deformation of tunnel surrounding rock and the tunnel initial support during the process and verify the design rationality of supporting parameters by simulating the process of Shuiniujia tunnel bench excavation. The following results are obtained:(1) The accumulated deformation value of the surrounding rock after 15 days of the top bar’s excavation is 50%-60%. The secondary lining construction can be carried out after 14 days of the section excavation. The expansion of the deformation is about 10% if the secondary lining construction is delayed for 3 months, but the surrounding rock remains stable.(2) The total surrounding convergence and the development trend of the asymmetry(Right is bigger than the left) gradually increases from the tunnel entrance to the exit, but the trend is gradually weakened.(3) The direct cause of the tunnel deformation asymmetry is: as the reservoir water level rising, water constantly seeping into the rock, softening the carbonaceous phyllite and weakening its intensity. So its resistance ability against high ground stress and the lateral pressure caused by rock expansion after excavation is weak.(4) Construction should pay attention to strengthening the support because of the stress concentration on both sides of the surrounding rock after the top bar’s excavation. The proposal is no anchor after the section excavation. The whole initial support meets the strength requirements and the design is reasonable.The research achievement of this dissertation has some reference value, for it provides the basis for the long term deformation monitoring after the completion of the tunnel and can guide the design and the construction of tunnels next to reservoirs in the future.