Study On Support System And Safe Construction Method For Soft Rock Tunnel

Many rivers in our country and the water flow is abundant, water resource is the highest in the world. Hydropower as a clean renewable energy and its low cost is in line with the national policy of sustainable development in China. At present, strong demand for electric power in domestic economy and national focus on the utilization of clean energy brings unprecedented opportunities. But there are many engineering practical problems in that progress.Hydraulic tunnel is generally long and buried deep, passes through the complicated geological conditions. Stress of the surrounding rock will be secondary distribution after tunnel excavation, the stress concentration may occur in certain parts of situation. Large deformation and decrease of the stability of surrounding rock will happens when the stess is beyond the rock can withstand. Such problems will be frequently-occuring especially when tunnel passes through the geological areas such as soft and weak rock.Based on the practical engineering support of the hydraulic tunnel of Shangtong Dam in Muli River, this papper is aimed at studying the practical problems in applications when tunnel passes through complex geological conditions such as soft and weak rock. Through the documentary research, data monitoring of construction site, numerical analysis and stability evaluation, the papper mainly researches and expounds the following aspects:(1)Through the investigation, get familiar with the research status of soft rock at home and abroad, master the definition and classification of soft rock and the related mechanical properties. Get familiar with stability influence factors of soft rock, grasp the judgement rules and analysis method of its stability, understand the excavation and shoring method while the hydraulic tunnel pass through the weak geological conditions of surrounding rock;(2)Carried out the of the tunnel excavation of soft rock with FLAC3D. It includes numerical analysis of the excavation under different surrounding grade,different stress release rate, different depth of burial and different excavation and shoring methodes. So the deformation, stability and the mechanical behavior of surrounding rock after the tunnel excavation which under complex geological conditions can be studied;(3)Based on the numerical analysis of tunnel excavation of soft rock, such as evaluation of the bearing characteristics and its stability of the tunnel supporting system under complex geological conditions could be studied. Finally finding the reseanable excavation methods and supporting measures to provide a reference for practical engineering;(4)Conduct the data monitoring and measuring at construction site and focuse on the contrastive analysis of numerical analysis. Combined with the numerical analysis data and putting forward reserved deformation for the excavation of tunnel.