The Mechanism Research Of Arch Tunnel Surrounding Rock Pressure

In recent years, as China’s high-speed railway and urban metro booming, thenumber of arch tunnel construction is also increasing. Among the large number ofconstruction, design and construction are also exposed many problems, so it isnecessary to conduct research arch tunnel rock pressure calculation method. Firstly,this paper based on elastic-plastic theory mechanical tunneling theory, usingnumerical simulation analysis method to study the tunnel surrounding rock pressurearch formation law, getting the result of single-hole tunnel rock pressure calculationmethod. Then it discussed the impact of the construction process on rock pressure,finally it get the arch tunnel surrounding rock pressure calculation method. Mainresearch work and achievements are as follows:(1)Pressure arch transfer mechanism was studied by using numerical simulationsoftware to establish a single hole tunnel in the two-dimensional plane model. Basedon the elastic-plastic theory, the impacts of the pressure arch range were determined,and further the boundaries of inside and outside the arch were also determined. Thedetermined conditions for the pressure arch inner boundary are: The point ofintersection of tangential stress curve and situ stress curve is the pressure arch innerboundary. If excavation tangential stress before and after the intersection does notexist, then put the tunnel profile as the pressure arch inner boundary. The determinedconditions for the pressure arch outer boundary is: Subtraction the after excavationtangential stress and situ stress, if the subtraction of the slope of the curve are verysmall, and the curve smoothing and stable, think the effective pressure arch wasbecome above the dome tunnel, put the stagnation as the pressure arch outerboundary.(2)According to the pressure arch mechanism, the calculation of the surroundingrock pressure arch theory was determined. The rock pressure is divided into two parts:the one part is the loose soil bellowing pressure arch internal boundary layer underthe action of its own weight of rock pressure, and the other part the internal pressure arch soil generated rock pressure due to deformation. And with reference to thetheory of Winkler model, it described in detail due to the pressure generated by thedeformation of the arch rock pressure calculation method. Finally, this calculationmethods and tunnel code recommended formula were compared and analyzed.(3)Based on the theory of the pressure arch rock pressure calculation methodwill be tunnel depth, tunnel span and rock mechanical parameters and other factors.Using Sensitivity analysis these above factors can be compared one by one thestrength of the each factor to rock pressure values. Taking into account the tunnelsurrounding rock pressure is determined by multiple factors together result to find outthe various factors and the relationship between rock pressures requires a lot ofcorrelation calculation. Because many factors need to consider, in order to notaffecting the results of the analysis in the premise of reducing the number of tests willbe used as research tools orthogonal. Finally, the MATLAB software is used tocalculate multiple linear regression orthogonal test data analysis, the practicalapplication of engineering to facilitate the rock pressure formula.(4)It considers the construction process on the rock pressure, using the finiteelement software to simulate tunnel construction process. It main analysissurrounding rocks disturbance and then the following pilot tunnel excavation on rockpressure generated by the impact of preceding pilot tunnel excavation. Theconsidering the impact of the construction process of rock pressure calculationsimulation results compared with a single hole in the tunnel surrounding rockpressure values under the same conditions, putting the ratio of pressure to rock archtunnel construction process as the impact factor. Finally, the impact factor added tothe pressure arch theory based on a single-hole pressure calculation formula Tunnel,obtained for arch tunnel surrounding rock pressure formula.