The Influence Of Blasting Vibration On Underground Chambers

In the construction of water resources and hydropower engineering, a lot of underground chambers and tunnels are to be excavated and more and more powerstations employ underground powerhouse. Underground chambers are also adopted widely in other fields such as mining, transportation and national defence engineering etc. The influence of blasting vibration on existed adjacent underground chambers or surrounding rock mass of the tunnel under excavating is inevitable if the method of blasting is employed for excavation. So the study of the influence of blasting vibration on underground chambers is of great importantance both in theory and practice.The influences of blasting vibration on the stability of surrounding rocks mass and concrete lining of existed adjacent chambers, or excavating tunnel and the grouted rockbolts are studied and analyzed in the thesis.The wave function expansion method is used to analyze the interaction of blasting seismic wave and the adjacent chambers, the influences of such factors as the radius of tunnel, the frequency of incident blasting seismic wave, rock mass types etc, on dynamic response and safe peak partical velocity (PPV)of circular tunnel are discussed. The conformal mapping method is adopted to deduce the general solution of stress and displacement of arbitrary shape tunnels under the acting of the incident blasting seismic wave with different frequency and incident angle. Taking the arch tunnel with vertical sidewalls as the example, the distribution of stress and vibration velocity of rock mass is presented and analyzed, and then the safe peak particle vibration velocity is decided. The multi polar coordinate transform and complex function are used to study the dynamic response of shallowly buried circular tunnels under the blasting vibration. The influence of free surface on tunnels is discussed.The influence of blasting vibration on fresh concrete lining is studied. The finite element method (FEM) is employed to analyze the spatial distribution of temperature and thermal stress of fresh concrete lining, the wave function expansion method is used to study the interaction of blasting seismic wave and the circular tunnel with lining, thenthe safe PPV of fresh concrete lining with different age is decided by taking into account the thermal stress of concrete lining. Using the conformal mapping method, the influence of blasting vibration on the arch tunnel with lining is studied and the safe PPV of concrete lining is deduced under different incident angle.The numerical simulation method of dynamic FEM is employed to study the influence of the excavation of blasting vibration on surrounding rock mass and shotcrete of the tunnel itself under excavating, the safe distance for shotcrete is decided. The different responses of surrounding rock mass of tunnel caused by cut-hole blasting, production blasting and perimeter blasting on the excavating chambers are alse compared.The stress wave theory and wave function expansion method are used to analyze the interaction mechanisms of blasting seismic wave and the grouted rockbolts and deduce the analytical solution of stress and displacement of rockbolt, grout and rock mass body. Based on the stress and velocity calculated, the safe PPV for grouted rockbolt is decided.