Optimization Of Construction Scheme For Extra Large Tunnels

With the rapid development of China's economy,transportation is also changing,it can be predicted.there will be more and more large span tunnel.This paper combines a tunnel engineering science and technology project with a large cross section tunnel as the engineering background.The simulation of the large cross-section tunnel project in the weak surrounding rock is carried out.First,the construction method of the tunnel is simulated to determine what kind of construction method is the most reasonable.Under the construction method of the tunnel with large cross-section,the excavation method of the tunnel,the construction scheme of the tunnel,the surrounding rock of the tunnel,the displacement of the tunnel,the deformation of the tunnel,the plastic zone and the loose area And so on,and with the actual measured data for comparative analysis,used to study these rules and the impact of the tunnel.1?On the basis of the above construction method and the construction plan optimization,it is necessary to study the regularity of the tunnel with the change of the span.We selected two lanes,three lanes,four lanes of the road tunnel for numerical simulation.The vertical and lateral displacements of the surrounding rock of the tunnel increase with the increase of the span.The compressive stress of the surrounding rock on both sides of the tunnel and the stress of the vault and the arch rock are the greater the span.The plastic zones of the three tunnels are approximately similar in shape and the smaller the span is,the smaller the affected area is smaller.In the case of integrated stress,displacement,plastic zone and deformation,the span has a great influence on the tunnel when the span is from two lanes to three lanes.When the span is from three lanes to four lanes,the changes to the tunnel.2?The construction method of the super-large tunnel is compared with the selection method,and the most suitable construction method.Based on the method of double side wall guide,the thickness and excavation method of core soil are simulated.The thickness of the core soil is 3m,5m and 8m,and the core with the thickness of 5m is the most reasonable.While the same thickness of the core soil,three-step excavation is better than two-step excavation.3?Numerical Simulation Study on Different Construction Sche mes of Extra Large Tunnel.Through the strain,stress and plastic zone,the displacement of the surrounding rock of the first excavation is smaller than that of the first excavation.Large cross-section tunnel construction sequence in the just digging,strain,stress gap,the first deep after the shallow depth of about 85% to 95%.With the excavation continues the gap gradually narrowed.The depth of the shallow the plastic zone and loose area to be smaller than the depth of the deep excavation program.The overall comparison of the two construction sequence,the first deep after the shallow excavation order is better than the depth of the deep.The excavation footage of the large section tunnel is simulated.When the excavation footage is 2m,3m,5m and 6m,it is found that the excavation footage is 3m optimal.The results show:...