Upper Bound Analysis Of Stability Of Shallow Tunnels For Unfavorable Conditions

The collapse accidents happened in the shallow tunnels during the excavation pose a great threat to the life and property of the workers. The analysis of the stability for shallow tunnels is therefore a research topic with important scientific value and high practical significance. The limit analysis can not only calculate the earth pressure but also estimate exactly the failure scope. Thus, on the basis of the Mohr-Coulomb failure criterion and the Hoek-Brown failure criterion, the upper bound theorem of limit analysis was employed to research the influence of a variety of factors on the stability of shallow tunnels, which can provide theoretical foundation and instruction for design and construction of shallow tunnels in the future. The main research achievements are as follows:(1) Based on the previous results, the failure mechanisms for shallow tunnels with a single hole and two holes were given. According to the principle of virtual power, the analytical solutions of earth pressure were derived, and SQP was applied to get the optimal solutions of earth pressure.(2) Making reference to the Mohr-Coulomb failure criterion, the influences of many factors, such as the nonlinear coefficient, lateral pressure coefficient, cohesion, buried depth, width, surface load and pore water pressure coefficient, on the earth pressure and failure plane for single tunnel and double tunnels were studied.(3) Based on the Hoek-Brown failure criterion, the effect of the geological strength index, rock constant, uniaxial compressive strength, disturbance factor, buried depth, width, surface load, pore water pressure on earth pressure and failure plane for shallow rock tunnels were presented.(4) Taking Eling tunnel of Jinggangshan as an example, the results agree well with data from site monitoring measurement, which validates the reasonableness of the correctness of this method.