Analysis Of Blasting Vibration Effects And Its Reduction Measures In Excavating A Subway Foundation Pit

The urban subway stations pits are always near residential areas, shopping malls, office buildings or high-rise buildings which not only need to guarantee security of engineering project and stabilization of the side slope, but also have to take the structural safety and stability of the nearby buildings as a precondition. Meanwhile, blasting excavation is always used for digging hard rock., the excavation process will bring blasting vibration inevitably, which can cause damage to the neighboring building structures directly. In a word, It is necessary to carry out active control of the blasting vibration while blasting in the city.This thesis uses the blasting excavation engineering of Changsha Metro Line 1 North Station subway station pit as the research background, adopts a research technique combined theoretical analysis, finite element numerical simulation and field tests, and analyzes vibration response characteristics of foundation pit adjacent structures under different blasting conditions (cutting blasting, bench blasting of single-row and bench blasting of double-rows). The article carried out following research from theory and field tests and drawed corresponding conclusions:(1) Compared several different forms of blasting load model, a more reasonable load model was selected and the calculation method of blasting peak load was determined.(2) Conducted numerical simulation to working condition under three kinds of blasting conditions (cut blasting, bench blasting of single-row and bench blasting of double-rows) and analyzed all kinds of situations.(3) Through the analysis of the measured datas by field testing, vibration velocity of cutting blasting is larger than that of bench blasting; vibration velocity of double-rows bench blasting is larger than that of single-row bench blasting.(4) When using multi-millisecond blasting, vibration of blasting will occur staggering-peak cancellation and reducing-vibration interference and there is a certain probability of seismic wave superposition and the reinforcing response.(5) To improve the cutting effects of rock, he best delayed-time used in the blasting of Foundation Pit is ranged 25ms-50ms.