岩质边坡抗震稳定性的能量方法研究

ENERGY ANALYSIS OF SEISMIC STABILITY OF ROCK SLOPES

地震荷载作用下边坡失稳判据是岩土力学研究的热点和难点,综合运用极限分析和波动理论,从功率角度出发,提出外力功率等于内能耗散的岩质边坡能量稳定性评价方法。借助强度折减法和超载系数法,通过安全系数对单节理边坡进行定量化安全性评估。以P波倾斜入射单节理边坡为例,首先,研究边坡的自稳临界高度和应力波入射节理透反射基本规律;其次,在边坡临界自稳高度范围内,研究应力波作用下边坡临界高度的动态变化情况;最后,根据外力功率等于内能耗散的判断准则,通过强度折减法和超载系数法,分析动荷载作用下单节理边坡动态安全系数的变化,计算块体极限滑动时所需的能量。研究表明:边坡节理面的黏聚力越高,其自稳临界高度越高,动荷载作用下边坡动态临界高度也越高,抗震性能也越好;随着入射P波峰值强度的增大,边坡动态临界高度降低的幅度也增大;随着入射角度的不断减小,边坡动态临界高度变化的幅度不断增大,表明地震作用下边坡破坏的可能性不断增大;边坡动安全系数的变化趋势与透射应力的变化趋势相反;边坡的高度越高,块体越不稳定,其极限滑动时所需的能量也越少。

For the geological disasters of slope failure under seismic loads,the failure criterion has been a hot and difficulty issue in rock mechanics. The main objective in the study is to combine the limit analysis and wave theory to carry out a new evaluation of slope stability from the perspective of power,that is,the rate of external work is equal to the rate of energy dissipation. By means of the methods of strength reduction and overload factor,the factors of safety were adopted to evaluate the quantitative safety of the rock slope. The oblique incident P wave across a single joint in jointed slope was considered. The variations of the critical height of jointed slopes and the transmission and reflection of stress waves were investigated. Then,within the critical height of jointed slopes,the variation of the critical height was studied under the stress wave. Finally,based on the energy criterion that the rate of external work is equal to the rate of energy dissipation,the variations of FOS were investigated by means of the methods of strength reduction and overload factor. The sliding energy of the block in limit state was also calculated. The investigations revealed that the higher the cohesion of the joint,the higher the self-stable height of the jointed slope. Therefore,the higher critical heights of the jointed slope during earthquakes result in the significant improvement of the seismic performance of the jointed slope. As the peak strength of the incident P-wave increases,the reduction degree of the critical height of jointed slope also increases. As the incidence of the stress wave decreases,the variation degree of the critical height of the jointed slope also gradually increases,indicating that the failure possibility of the slope is also increasing during earthquakes. The variation of FOS is just opposed to that of the transmitted waves. The higher the rock slope is,the more unstable the block is. Therefore,the corresponding sliding energy is decreasing as the jointed slope is in limit state.