Research On Time And Space Effect And Support Time Of Large Cross Section Tunnels Under Shallow Buried Unsymmetrical Pressure

With the development of this economy,in recent decades,China's transport facilities has made brilliant achievements in the construction of transport infrastructure throughout the country.With the development of traffic construction,the tunnel project has become an important part of traffic engineering.It has made great achievements in the construction of tunnel engineering.However,in the trend of traffic infrastructure construction,there are many unavoidable Problems,such as,tunnel design and construction to operate,these problems are endless.This paper is Based on the construction of Langshan Dongshan Tunnel Project,due to the large number of construction processes during the construction of Dongshan Tunnel,left and right hole of the tunnel have been constructed Successively,and the phenomenon of constant perturbation of the surrounding rock has been tracked and measured.Combining theoretical analysis with three-dimensional numerical model,this paper has conducted a more in-depth analysis for time and space effects and support time research of the shallow buried bias large cross-section tunnel.The main research contents are as follows:1.a number of typical sections of the project are analyzed by field test statistical analysis and regression analysis of the relationship between the displacement of the surrounding rock,the spatial relationship of the surrounding rock,the relationship between the displacement of the surrounding rock and the time of the tunnel support.The main conclusions drawn from the statistical analysis data are that the displacement of the vaults in the step-step step of the large-section tunnel is much larger than that of the dome.2.The three-dimensional model is established,and the dynamic construction process is simulated.Displacement of surrounding rock,the stress of the surrounding rock,the stress of the supporting structure,the dynamic change of the stress in the middle wall of the tunnel and the stress of the secondary lining are analyzed.It is concluded that the influence of the excavation of the surrounding rock of the tunnel on the surrounding rock displacement does not have the influence of tunnel excavation.The vertical displacement of the surrounding rock of the tunnel is larger than the horizontal displacement.The displacement of the surrounding rock of the right hole is larger than that of the left hole.The displacement of the first hole is affected by the excavation disturbance caused by the excavation disturbance.The stress intensity of the arch on both sides of the tunnel in the bias state is more concentrated,and the stress intensity of the two sides of the arch is obviously larger than the other side.In the step excavation construction,the amount of displacement caused by the excavation of the upper step is much larger than that of the lower step excavation.The displacement rate of the upper step excavation is 70% ~ 80% of the total displacement change.3.The analysis of the optimal support time of the displacement of thesurrounding rock of the shallow buried and large cross section tunnel is carried out,In the combination of the above several methods to obtain the secondary support for the project under the best support time for 25~30d,from the face of the face of the distance of 30~35m...