Research Into The Surrounding Rock Stability Of Tunnel Based On The Pressure Arch Theory And Stress Release Rate

The stress state of surrounding rock will change with excavation of tunnel. The self-stability of the tunnel and the division of deep or shallow tunnel are decisively affected by the formation of the pressure arch effect, which is regarded as key reference for the selection of stress release rate in the design of the tunnel support structure for weak rock with rheological properties,the intrinsic relationships among the structural design parameters of tunnel、the engineering geological conditions、the pressure arch effect and the rock stress release rate are studied in this paper by numerical simulation method,the research details are as follows:(1)Basing on Jinpenwan tunnel engineering at Jingxin highway, the pressure arch effect in the process of the tunnel construction is described, the stress path analysis method is adopted,the method for the definition of the pressure arch of tunnel and the determination of the inner and outer boundary are established.(2) By numerical simulation MIDAS /GTS, the pressure arch under the influence of the factors such as tunnel depth、tunnel span、rock mechanics parameters、demixion of tunnel rock、construction process is quantitatively studied. As can be seen from the numerical results, to form a pressure arching, arching tunnel there is a critical depth in a given geological conditions,tunnel span is the biggest factor affecting the critical depth of the arch.(3) Basing on whether the effective pressure arch of the tunnel is formed, the critical arch depth of the Jinpenwan tunnel is given and the Judgment and division of the tunnel deep or shallow depth is conducted. The comparison of the result with the measured data provides a reference for the dynamic design and construction of the tunnel.(4) A three-dimensional model of the Jinpenwan tunnel is established by using MIDAS / GTS software, the influences of the stress release rate to the pressure arch effect、the tunnel deformation and the force supporting structure is analyzed. The results indicated that: the stability of the surrounded rock is affected by the initial stress release rate in the construction process of the Jinpenwan tunnel with weak rock.