Research On Distribution Law Of Loose Circle Of Tunnel Surrounding Rock Under High Stress

During the construction of tunnel,the disaster in engineering such as the tunnel surrounding rock in construction cracking,ejection,collapse,distortion in high geostress rock mass,which will be harmful to the subsequent operation of the security.By studying conditions of tunnel surrounding rock stress-strain state and distribution of surrounding rock loose zone under high geostress,the tunnel design and construction parameters can be optimized and efficient and safe construction can be protected.Based on systems commonly used interpretation of high geostress criteria and methodologies,as well as Hoek-Brown strength criterion theory,the paper proposed the theory of high geostress state determination of the formula.Through the introduction of the intermediate principal stress,the amendment of Hoek-Brown was achieved,which can be applied to the condition of high geostress.And the analytical solutions of district of surrounding rock stress,loosening of the plastic zone radius and radius of the circle were deduced by the Elasto-plastic theory.Using the proposed criterion of high geostress,a deep buried tunnel at Bao Han high speed is in high stress area.The tunnel surrounding rock stress,broken plastic zone and surrounding rock loose zone range can be analyzed by Typical sections ZK163+868 and YK163+775,according to the amended Hoek-Brown strength criterion for calculation of elastic-plastic theory,and finite element numerical simulation of MIDAS/GTS and acoustic field measurement.Results showed that three surrounding rock loose zone range is close and the distribution is consistent which proves that modified Hoek-Brown strength criterion can be accurately calculated the radius of surrounding rock loose circle.The tunnel surrounding rock loose circle of RADIUS in high geostress field was first decreased and then increased with the increase of the intermediate principal stress.And the trend increased with the support force decreased and is not evenly distributed,because the influence of tectonic stress loose circle radius is larger than the vertical direction in the horizontal direction.