水-岩和循环加卸载次序作用下砂岩动力特性损伤演化规律

Damage evolution of dynamic characteristics of sandstone under the sequential action of water-rock interaction and cyclic loading and unloading

库岸边坡消落带岩体处于长期水-岩作用和频发中低强度水库地震作用之下,岩体的力学特性劣化直接影响库岸边坡的动力响应及抗震能力。基于此,模拟库岸边坡消落带的环境条件,设计进行了模拟库水位周期性升降变化过程的水-岩作用试验,在试验过程中采用循环加卸载方式模拟地震作用的影响,并重点考虑了水-岩和循环加卸载的次序作用。研究结果表明:(1)在水-岩作用下,岩样的动力参数总体呈先陡后缓的指数形式变化,考虑水-岩和循环加卸载次序作用后,岩样动力参数的劣化速度和劣化趋势明显增大,说明频发中低强度水库地震对长期处于水-岩作用环境的岸坡岩体损伤发育有明显的促进作用。(2)在水-岩作用和循环加卸载作用下,岩样的微细观结构由密实状态逐渐趋于松散,对应的完整性劣化系数和次生孔隙率亦呈现先陡后缓的变化趋势,其中,周期性水-岩和循环加卸载次序作用下岩样的微细观结构变化最显著,含初始循环加卸载损伤的岩样次之,单独水-岩作用下岩样的变化趋势最小,不同方案下岩样微细观结构的变化及差别也决定了其动力特性的劣化规律。(3)在长期水-岩作用和频发中低强度水库地震作用下,库岸边坡岩体内部的损伤会逐渐累积发展,直接影响库岸边坡的动力响应特性及抗震能力,因此,在库岸边坡长期抗震性能分析评价中,应该比较系统地考虑岸坡岩体动力特性的劣化规律。

The rock mass in the hydro-fluctuation belt of the reservoir bank slope is subjected to long-term water-rock interaction and frequent moderate-low intensity reservoir earthquake.The deterioration of the mechanical properties of the rock mass caused by this directly affects the dynamic response and seismic capacity of the reservoir bank slope.Based on this,the settings of the fluctuating zone of the bank slope of the reservoir are simulated,and the water-rock interaction test to simulate the periodic rise and fall of the reservoir water level is designed and carried out.In the course of the test,the cyclic loading and unloading method is used to simulate the influence of seismic action,and the sequential action of water-rock interaction and cyclic loading and unloading is mainly considered.According to the test results,the following conclusions are obtained.(1)The dynamic parameters of the rock sample generally change exponentially from steep to gentle under the water-rock interaction.After considering the sequential action of water-rock interaction and cyclic loading and unloading,the deterioration rate and trend of dynamic parameters of rock samples increase obviously,indicating that frequent moderate-low intensity reservoir earthquakes can obviously promote the damage development of bank slope rock mass in the environment of water-rock interaction for a long time.(2)Under the action of water-rock interaction and cyclic loading and unloading,the microstructure of rock samples gradually loosens from the compacted state,and the corresponding integrity degradation coefficient and the secondary porosity also show a trend of steepness and then slowness.Among them,the microstructure changes of rock samples under the sequential action of periodic water-rock interaction and cyclic loading and unloading are the most significant,followed by the rock samples with initial cyclic loading and unloading damage,and the change of rock samples under the water-rock interaction alone is the smallest.The changes and differences of the microscopic structure of the rock sample under different schemes also govern the degradation law of its dynamic characteristics.(3)Under the long-term water-rock interaction and frequent moderate-low intensity reservoir earthquakes,the internal damage of the reservoir bank slope will gradually accumulate and develop,which will directly affect the dynamic response characteristics and seismic capacity of the reservoir bank slope.Therefore,the degradation law of the dynamic characteristics of the bank slope rock mass should be systematically considered in the analysis and evaluation of long-term seismic performance of reservoir bank slope.