一维块系地质块体波动特性的试验和理论研究

Propagation properties of stress waves in one-dimensional geo-block medium

深部岩体具有块系等级构造特性,俄罗斯深部矿山原位量测得到的摆型波(μ波)产生于动力冲击作用下(如深部地震、岩爆和封闭核爆等)块系岩体的运动,是一种不同于传统纵波和横波的新型非线性弹性波。为了证明μ波的存在,并对块系块体介质中应力波传播特性及块体材料、尺寸和结构形式的影响进行研究,利用自主研发的深部岩体动态特性试验系统,分别对6种具有不同特征尺寸的花岗岩和水泥砂浆块系块体模型和连续块体模型进行一维低速冲击试验。试验表明:对于两种结构形式的介质,一维冲击作用下,块体(测点)三向加速度幅值均随冲击能量提高近似线性增加。对于块系块体介质,块体三向加速度幅值随块体个数增加呈一阶指数衰减,并且衰减系数与冲击能量无关;冲击能量仅仅改变加速度波谱密度幅值,而对三向振动极值频率没有影响,并且块体越多,能量越大,块体振动波谱趋于低频波的趋势越强;通过对比试验结果和原位量测结论(关于μ波无量纲冲击能量判据,波速和振幅,波谱峰值频率等),证明了块系介质中出现的低频低速波就是μ波;通过对5种块系块体模型三向加速度频谱进行分析,证明其振动极值频率满足定量的规范序列关系(2^(1/2))i f 0,推广了原位测量试验结论。并且上述规律中,块体材料和尺寸效应不明显,而对于连续块体介质上述规律均不成立。最后,分别采用黏弹性夹层和刚性块体、集中质点以及弹性块体三种理论计算模型对冲击作用下块系块体运动参数进行分析,计算结果和试验曲线吻合较好,并讨论了夹层参数的敏感性。

Deep rock mass is a block-hierarchical structure.Pendulum-type wave（μ wave） discovered in Russian deep mines is a new type nonlinear and elastic wave,which is induced by the motion of geo-blocks under external pulse（such as deep seismic,rock burst and confined nuclear explosion） and different from the traditional longitudinal or transverse waves.In order to confirm the existence of the μ wave,the propagation properties of stress wave in blocks medium as well as the influences of the block materials,dimensions and geo-structures are studied.Based on the multipurpose testing system developed by the authors,one-dimensional low-speed impact tests are carried out on six granite and cement mortar blocks and continuum block models with different characteristic dimensions,respectively.For both block and continuum models,three-dimensional acceleration amplitudes of each sub-block（measured points） increase almost linearly with the increase of the vertical impact energies.For block models,three-dimensional acceleration amplitudes of each sub-block attenuates exponentially（one order） with the increase of the disturbed sub-block,and the decay coefficients are independent on impact energies.The increasing impact energies only increase the amplitude of the spectral density,and have nearly no effect on the 3D local maximal frequencies.The more the number of the blocks and the larger the external pulse,the more obvious of the tendency that the dominant frequencies develop toward low frequency region.Through comparison of the model test data with the in-situ measurements（critical energy for emergence of μ wave,amplitude and velocity,and the maximum spectral frequencies,etc.）,the low-frequency and low-velocity waves occurring in blocks models are validated as μ wave.Based on the analysis of spectral densities time histories of 3D accelerations of five block models,the frequencies corresponding to the local maximums of spectral density curves of three-directional acceleration time histories satisfy quantitative canonical sequences of （2^（1/2）） i f 0,which extends the conclusions of in-situ tests.The effects of material and dimension of model blocks are not obvious,and the above laws are not validated by continuum block medium.Finally,the visco-elastic interlayer and rigid blocks,concentrated mass as well as elastic blocks analytical models are established for theoretical analysis of acceleration time histories.The calculate results agreed well with the test data,and the effects of the parameters of interlayer are discussed.