拉裂-坠落式岩质崩塌失稳过程声信号特征模拟试验研究

Acoustic signal characteristics during the crack-toppling rock collapsedeveloping process based on a simulation experiment

岩体崩塌是西南岩溶山区广泛分布的地质灾害,崩塌失稳过程极为迅速,常规监测手段难以有效监测预警。根据岩体崩塌孕育发展力学过程,开展分级蠕变和自然渐变2种工况下的拉裂型崩塌相似模拟试验,采用声发射系统和无线微震传感器研究崩塌模型失稳过程声信号特征。研究结果表明:位移和应变场均仅在主破裂发展瞬间产生突变,难以提供指示失稳破坏的前兆信息;高频声发射信号的多种时域和频域参数在2种工况下的岩体崩塌相似试验中均表现明显的阶段性特征,可为岩体崩塌失稳提供有效的失稳前兆指示;采用滑动窗口法分析了试验全过程的微震波形信号,根据主频特征可清晰区分3类信号,低频信号在加速损伤阶段出现突降;根据2种工况下相似模拟试验声发射和微震信号的特征,崩塌发展过程可分为渐变阶段、主控面加速损伤阶段和失稳破坏阶段,模拟自然渐变荷载下主控裂纹贯穿失稳更为突然。研究成果为发展岩溶山区岩体崩塌监测预警方法和技术提供了支撑。

Rock collapse is a typical geological disaster widely distributed in karst mountain areas of southwest China.The rock collapse occurrence process is extremely rapid,which is difficult in monitoring and early warning using traditional monitoring techniques.According to the mechanical process of rock collapse development,the simulation test was carried out on crack-toppling collapse under two conditions(multi-step creep and natural gradual loading),and the acoustic signal characteristic during the development of the modelled collapse was monitored by using the acoustic emission system and the wireless microseismic sensor.Results are as follows.The displacement and strain fields were almost unchanged until the sudden collapse of the rock collapse model,indicating no useful warning information could be provided by the displacement monitoring.Various time-domain and frequency-domain parameters of high-frequency acoustic emission signals show obvious stage characteristics during the development of the collapse model under two conditions,which could provide useful precursory indication for the rock collapse.The microseismic waveform signals throughout the test were analyzed by a sliding window method,and three types of signals could be clearly distinguished according to the characteristics of dominant frequency that the low frequency signals show a sudden drop in the accelerated damage stage.According to the characteristics of acoustic emission and microseismic signals during the development of the rock collapse model,the development process can be divided into the gradual evolution stage,the accelerated damage stage of the primary crack and the failure stage.The penetration of the primary crack under natural gradual loading is more abrupt.The research results could provide support for the development of rock collapse monitoring and early warning methods and technologies in karst mountainous areas.