Under The Condition Of High Ground Stress Soft Rock Tunnel Deformation Analysis And Control Research

Large deformation problems of the weak rock tunnels in high ground stress has always been a challenge on construction safety of tunnel. With the implementation of the One Belt And One Load, The Midwest development will be a new momentum of China’s economic in the future.The rapid development of economy is based on convenient transportation, High-speed railway is the main transportation between connection area. It is conceivable that a new upsurge in high-railway construction is making in the Midwest of China. But the most of midwest areas with the complex terrain and high altitude are mountains. It often suffered the long, large, and deep tubes, and is affected by the seismic fault belt and the geological tectonic movement in the rail construction. Especially weak rock tunnels with high ground stress, in the process of excavation, is easy to appear the phenomenon of large deformation destruction.In the article, set in Songpan tunnel construction of Chenglan high-speed railway, the author prosesses numerical analysis for the soft rock tunnel under the effect of different lateral pressure, and inverse analysis for parameter of weak rock by combining the Songpan measured data, in order to provide guidance for the subsequent construction.The biggest characteristic of weak rock tubes excavation is large deformation in high ground stress area. Chiefly, the author elaborates the domestic and overseas research achievements about large deformation in soft rock tunnel excavation at high ground stress area, to learn the domestic and overseas research status about the large deformation problem of weak rock tunnel.Secondly, the paper introduce the discipline of ground stress and the judgment standards of high ground stress. Whether the country rock of tunnels are situated in high ground stress depends on country rock’s strength ratio rather than unsophisticated obsolute value of high ground stress, and also states the mechanism of the deformation of tunnels’ country rock, to lay a theoretical foundation to the research of this paper.Thirdly, through the finite element software MIDAS/GTS, high ground stress area deformation characteristics of soft rock tunnel under the action of horizontal stress in high ground stress area were studied. As a result, under different lateral pressure coefficients, tunnel face excavation has impact of different level on the deformation of country rock, when the lateral pressure coefficient of country rock is greater than 1, the maximum vertical displacement of the tunnel transfer to the waist of arch. As the lateral pressure coefficient changed from small to big, the horizontal displacement of the tunnel goes first outward extrusion, and then gradually goes inward convergence, and shows linearly increasing, but displacement of arch presents linearly decreasing. In combination with the field measured deformation data of the tunnel, the coefficient of lateral pressure of country rock can be approximately determining, and it provides the basis for parameters of country rocks’ back analysis and calculation.Finally, taking the large deformation of Songpan tunnel construction in Chenglan railway, this paper proceeds the mathematical regression analysis for the horizontal displacement of the tunnel and the displacement of arch, at the same time, uses the highest mathematical function to forecast the ultimate displacement. According to the final deformation of country rock, using the golden section method and MIDAS/GTS, country rock elastic modulus E and the lateral pressure coefficient K were calculated and back calculated, to get the elastic modulus and coefficient of lateral pressure of surrounding rock. And it used the measured data that were calculated in the same section of the construction period to verify the parameters of surrounding rock, to prove the rationality and feasibility of the back analysis in parameters of country rock.This paper have some practical value in engineering, and can provide reference and model for the dynamic construction of the tunnel in the treatment and utilization of the measured data.