Study On The Dynamic Stability Of High Rock Slope Induced By Blasting Vibration

Many large hydropower stations that are being built or to be built are mostly located at the high-mountain-and-gorge areas in the southwest and northwest of China. The slope of dam abutment is often be excavated in strips which are always long and narrow. The arrangement of construction road is very difficult. In order to speed up the construction progress, large scale deep-hole bench millisecond blasting is usually adopted. The scale of a single blast is large, which brings the problem of the dynamic stability of high rock slope induced by blasting vibration.The influence of blasting vibration on the dynamic stability of high rock slope is a complex dynamic problem in rock engineering, which relates to geology, explosion mechanics and rock dynamics, etc. It's a key technical problem that is urgently waiting to be solved in the construction of some large hydropower stations located at the high-mountain-and-gorge areas in the southwest and northwest of China. To do further study on the problem is of both high theoretical and practical importance.A series of research works have been done in the thesis, such as the characteristics of blasting vibration, the dynamic response of high rock slope containing fault, the numerical analysis methods of the dynamic stability of high rock slope and the safety criteria of slope induced by blasting vibration, etc. The following achievements have been obtained:An equivalent method for the acting of blasting load in the simulation of blasting vibtation is put forward. Three methods are compared, including (a) simulate the blasting load through calculating the propagation of detonating wave along cylindrical charges, (b) directly acting the blasting load on the boreholes wall to simulate blasting load, and (c) acting the equivalent blasting load on the cross section including row of boreholes . It is concluded that, it is feasible to use the method of acting equivalent blasting load on the cross section including row of boreholes to simulate blasting vibration in middle-and-far field.The characteristics of blasting vibration load and the superposition of blasting vibration wave induced by millisecond blasting are studied. By comparing the simulation of single-hole blasting and multiple-hole blasting, the influences of characteristics of blasting source, properties of rock mass, delay intervals, distance from blasting source and delay accuracy of detonator, etc, are analyzed. The relationships of the magnification coefficient after superposition versus the distance from blasting source are presented through numerical simulation. By using the method of genetic algorithm, the possible maximum magnification factor caused by the superposition of blasting vibration due to the delay error of detonators is studied.The dynamic response of high rock slope containing fault under the action of blasting seismic wave is studied. The influence of the thickness of fault, the occurrence of fault and the wave impedance of the filled media in fault etc, on the propagation of blasting seismic wave is analyzed. The attenuation laws of the amplitude and the spectrum of blasting seismic wave behind fault is determined. The superposition effect of blasting seismic waves behind fault is discussed. The partial dynamic stability of high rock slope containing faults under the action of blasting vibration is evaluated. Combined with the excavation blasting work of the left-bank abutment slope of Jingping Hydro-power station cascade-â… , the dynamic properties of slope under blasting vibration is analyzed. The advantages and disadvantages of different excavation methods are compared, which offers a reference for the engineering practices.Based on the Sarma method of Limit Equilibrium Analysis, the dynamic stability of high rock slope under blasting vibration is analyzed using time history analysis method, and case study is conducted combined with the excavation blasting of the slope of Jingping Hydro-power station Class-â… . The variation of frequency spectrum, amplitude and phase of blasting vibration could be taken into account in the method proposed. The dynamic stability factor varying with time is obtained. It is indicated that the influence of the frequency of blasting vibration should be taken into account during analysis, and it is safe to select the minimal value from the time history of dynamic stability factor to evaluate the dynamic stability of slope.The safety criteria for blasting vibration during the excavation of slope are studied. By calculating of the dynamic response of high rock slope under blasting vibration with Dynamic Finite Element Method, the safety threshold of PPV for rock slope induced by blasting vibration is decided through the statistic relationship between the peak value of tensile stresses and the PPV on the sidestep according to the failure law of maximum tensile stress, and the reasonable monitoring position of blasting vibration is also proposed. The research result obtained has been applied during the excavation of the rock slope in Xiaowan hydropower station.