Field Test And Numerical Simulation Analysis Of Influence Of Blasting Vibration On Adjacent Chamber

It's inevitable that blasting construction will have an adverse effect on the safety of underground chamber. The side wall of adjacent chamber will have tensile stress and shearing stress when blasting seismic wave reach the border of side wall of adjacent chamber. For those underground chambers with small clear distance and large section in blasting excavation, if the tensile stress or the shearing stress induced by blasting seismic wave was large enough, it would lead to tensile failure or shear failure in surrounding rock of adjacent chamber. In most countries, the peak vibration velocity are considered as basis for safety estimation of underground chamber under blasting vibration and different safety standards for blasting vibration are established. Generally speaking, the rule of blasting seismic wave propagation can be obtained based on field blasting vibration test and blasting vibration strength can be predicted so as to limit blasting vibration velocity within safety vibration velocity range by adopting relevant measures.There are three parallel diversion tunnels arranged along the right bank of dam site of a hydropower station. These diversion tunnels are near each other with clear distance between tunnel walls of 30~40m only and having large excavated section as well as severe interference of blasting excavation, so the safety become a major issue. Based on in-situ blasting vibration test and numerical simulation of Influence of blasting vibration on adjacent underground chamber, some research results are obtained as follows:(1)Based on in-situ blasting vibration test, the blasting seismic wave propagation disciplines of underground diversion tunnels in complicated conditions were studied. Based on Sadaovsky empirical formula, regression analysis was conducted to obtain propagation discipline of blasting vibration velocity along adjacent diversion tunnel straight wall facing blasting. For field test results, the horizontal particle peak velocity of blasting vibration was large than the vertical particle peak vibration velocity; Controlling horizontal vibration velocity was the key.(2)The numerical simulation were conducted to study on the vibration response of diversion tunnel by adopting simplified triangle load as impact load model for blasting breaking area. Distributions of particle vibration velocity, stress and displacement surrounding the adjacent diversion tunnel wall were obtained by numerical simulation.(3)For numerical simulation, the vibration velocity of adjacent diversion tunnel facing blasting was far greater than that of not facing blasting. The side wall facing blasting was the main area where the breaking tended to occur. Considering the maximum shearing stress, the maximum tensile stress, the maximum displacement and vibration velocity of tunnel wall and rock tensile strength was relatively small, the tensile failure tended to occur in adjacent tunnel straight wall facing blasting where the tensile stress may first reach tensile strength of rock when the blasting impact load continued to increase.(4)Due to large static stress of rock mass under static load, the stability analysis of adjacent chamber under blasting vibration should be considered together with effect of static load and dynamic load. Moreover, the chamber shape should also be considered when assessing the stability of underground chamber.