Research On Influence Of Shallow Buried Eccentric Pressure Tunnel Entry And Blasting Construction On Adjacent Existing Tunnel

The increasing scale of tunnel construction is bound to lead to poor geological conditions and shallow buried bias pressure at the tunnel portal,and the impact of blasting construction of new tunnels on adjacent operating railway tunnels.Taking Caozigang tunnel as the engineering background,this thesis studies the impact of shallow buried eccentric pressure tunnel entry and blasting construction on the adjacent existing high-speed railway tunnel.The research results aim to provide scientific basis and technical support for the safe construction of Caozigang tunnel,and provide some reference for similar engineering practice.The main research contents and achievements of this thesis are as follows:(1)Considering the actual working conditions of Caozigang tunnel,the four construction methods are compared and selected by numerical simulation,and the reasonable construction scheme is CD method excavation supplemented by advance pipe shed support.Due to the action of bias,the displacement of deep buried side is greater than that of shallow buried side;Since the right tunnel is excavated first,the displacement value of the right tunnel is greater than that of the left tunnel.The application of pipe shed will significantly improve the stress on the upper part of the initial support,and the maximum tensile stress appears at the right arch foot of the right tunnel.The cumulative value and deformation rate of surface settlement,vault settlement and peripheral convergence of Caozigang tunnel are within the safe range.(2)In engineering practice,the unsaturated nature of rock and soil must be considered when studying the supporting force required by the tunnel face,and the supporting force is affected by many factors.The rock mass strength of Caozigang tunnel decreases with the increase of saturation.The inflection point of the curve is that the saturation is 0.4.When the saturation is 0.4,the rock mass strength is reduced by 88%,the equivalent cohesion is reduced by 58%,and the internal friction angle is reduced by 41%.According to the calculation,the supporting force required to ensure the stability of the tunnel face at the entrance section of Caozigang tunnel is 64.02 kpa.(3)Based on the blasting scheme of Caozigang tunnel and Sadovsky formula,the maximum vibration velocity of the existing high-speed railway tunnel lining under various working conditions is preliminarily obtained,and the dynamic response law of the lining is obtained by numerical simulation under two adverse working conditions.When Poisson’s ratio is fixed,the propagation velocities of transverse and longitudinal waves increase with the increase of E/ρ.The preliminary calculation results show that the maximum vibration velocity of the lining of the existing high-speed railway tunnel is within the safe allowable range of 1cm/s.The numerical simulation results show that under the two adverse conditions,the maximum vibration velocity of the existing high-speed railway tunnel lining is between the arch crown and arch waist on the blasting side,and the velocity is within 1cm/s.There is a positive correlation between blasting load and charge density.Under the two adverse working conditions,the charge density can be increased to1.3 times and 1.1 times respectively.