Research On Prestressed Anchor Cable Support And Ground Stress Test Technology Of High Ground Stress Tunnel

In areas with high in-situ stress and with the development of the tunnel towards deep burial year by year,the tunnel is faced with the threat of high in-situ stress,which inevitably leads to large deformation and other disasters,seriously affecting the safety of tunnel construction and operation.At present,the concept of increasing support stiffness is facing many problems.Prestressed anchor cable support belongs to active support system,which provides a new solution for the control of tunnel large deformation.At the same time,it is a necessary and fundamental work to carry out the in-situ stress test when the prestressed anchor cable is used for support.The deformation characteristics of the tunnel under high ground stress are analyzed by monitoring and measuring data of the construction of the tunnel.FLAC3d was used to simulate and analyze the stress and deformation characteristics of surrounding rock under the condition of prestressed anchor cable support.This paper studies the method of testing the in-situ stress by hollow inclusion method,probes into the new technology of drilling and relieving the stress by using the principle of acoustic rock fragmentation,and preliminarily analyzes the feasibility of testing the in-situ stress by polarization method.The main research work is as follows:（1）Based on the monitoring data of no.2 inclined shaft and exit of positive tunnel of muzhailing highway tunnel,the deformation characteristics under high in-situ stress of muzhailing tunnel are analyzed,and the supporting effect of prestressed anchor cable is analyzed through the displacement of arch roof,arch waist and arch bottom.The monitoring analysis shows that the conventional support measures such as steel arch support fail to effectively restrain the tunnel deformation,and the prestressed anchor cable support significantly reduces the deformation amount and deformation rate of the tunnel arch roof,arch waist and arch bottom.（2）FLAC^3dwas adopted to simulate the change law of arch roof,arch waist and arch bottom displacement under the condition of anchor cable support,and to simulate the effect of joint support of tunnel anchor cable and anchor rod under the condition of high ground stress.The simulation results show that the convergent displacement of the tunnel decreases with the length of prestressed anchor cable increasing,the spacing decreasing and the preload increasing.（3）Based on the stress relief method of hollow inclusions,the principle,technology and equipment of drilling and stress relief technology based on the principle of acoustic rock fragmentation are discussed.The acoustic wave hole formation and stress relief have the advantages of high quality of hole formation,small disturbance to surrounding rock and small disturbance to the hollow inclusion in the process of stress relief.（4）Based on the birefringence of polarized wave when it passes through rock mass,the function of stress based on birefringence index is preliminarily discussed,and then the stress is analyzed and calculated,this method has low test cost and high test speed.