Both Road Section Tunnel Construction Of Surrounding Rock Stability Study

With the development of the traffic construction in china, a mass of subways and intercity express railways will be constructed.When it is required to get across a city, people adopt tunnels undercrossing in most cases to save field and protect environment, and these tunnels will be constructed under the existing roads inevitably. In the process of construction, it is necessary to think over how to decrease their influence to the existing roads and ensure the roads'regular operation.In addition, the influence of traffic load towards tunnels could not be neglected. Therefore, with Liuyanghe tunnel built under an existing expressway as the background, this thesis is to investigate the stability of surrounding rocks and the mechanical property of supporting structure in the process of construction. This thesis is to explore the following problems:1.To analyze the settlement law of strata and road surface in the process of construction through the data measured.2. To build a three dimensional model with the finite element software-ABAQUS according to the specific condition of the tunnel;to stimulate the overall construction of three benches of the tunnel;to analyze the stability of surrounding rocks and the mechanical property of supporting structure in the construction of the tunnel, and to prove its accuracy by comparing it with the data measured; and to analyze the strengthen effect of double-layer pipe-roofs for the soil layer.3.To build a two dimensional finite element model,to stimulate traffic load with the user subroutine of finite element software—ABAQUS.To stimulate the condition of the construction with traffic load imposed onto the road on the basis of the upper and the middle benches have been excavated.4. To analyze the stability of surrounding rocks and the dynamic response of supporting structure when the motor load (one axle load 100kN) and the roller load are imposed onto the surface.And to analyze the main reasons which lead to the subsidence of road surface and the damage of tunnel's supporting structure.5.To provide the following suggestions for the design and construction of three-bench excavation of large section tunnels built under the existing roads:before excavating tunnels, advanced support by pipe-roofs should be carried out, one bench should be followed by another, the left half-section and the right half-section of the middle and the lower benches should be excavated alternately; locking anchors should be set at springer, and duct grouting with small tremie pipes should be carried out to improve the stability and carrying capacity of the soil at springer; the primary line should be sealed to be a ring as early as possible, the second line should be followed in time to play the integral carrying capacity of the supporting structure;traffic load should be calculated to select the parameter of supporting structure reasonably.