应力波在具有梯度应力岩石中的传播衰减规律及机理

Due to the effect of in-situ stress field and stress redistribution caused by excavation unloading, surrounding rock has been subjected to gradient static stress when propagating of blasting stress wave in underground rock mass engineering. Gradient stress may change the rock void ratio and closing degree of structural plane, result in the gradient generalized wave impedance of rock, and ultimately have a great influence on the transmission and reflection rule, the study about these is in the blank. Complicated in-suit stresses in rock mass are simplified as linear and nonlinear gradient stress. The specimens are manufactured by aluminum, weathered sandstone and similar materials. The tests of stress wave propagation in specimens with different gradient stresses are carried out based on own designing test loading device. The quantitative relations between gradient stress and gradient longitudinal velocity, gradient wave impedance are established by researching test results. The wave equations of specimens are established by the relationships between gradient stress and gradient longitudinal velocity, and are solved in time domain and frequency domain respectively. On the basis of analyzing different frequency bands energy changes by wavelet packet tools, the effect of gradient stress on stress wave amplitude and frequency dispersion characteristics are studied by associating with numerical simulation. Stress wave propagations in specimens with gradient stress are studied based on the relationship between gradient stress and gradient wave impedance, and the influence mechanisms of gradient stress on stress wave propagation are announced. The results will establish a theoretical basis for stability analysis of surrounding rock under blasting excavation and wave propagations in complicated rock-mass.

爆破应力波在地下工程围岩体中传播时，由于原岩应力及开挖卸荷导致应力重分布等因素的影响，围岩体已具有梯度静应力。梯度应力使岩体沿梯度应力方向具有不同的孔隙比，使其波阻抗呈梯度变化，造成应力波的透反射规律发生较大改变，目前对此研究处于空白状态。本项目考虑线性和非线性两种形式的梯度应力，选用铝杆、较风化的砂岩和相似材料制备试件，基于自行设计的梯度应力加载试验装置，对试件进行不同应力梯度下的应力波传播试验，研究梯度应力与梯度纵波波速和梯度波阻抗之间的定量关系，建立材料具有不同梯度应力时的波动方程，分别求其频域和时域解。基于试验数据，利用小波包工具分析其频谱特性，结合数值模拟，研究应力波幅值时空变化规律和频散特性。基于梯度应力与梯度波阻抗关系，分析具有梯度应力时应力波的传播过程，揭示梯度应力对岩石中应力波传播的影响机理。研究成果为工程岩体爆破开挖围岩稳定性分析和复杂岩体中应力波传播研究奠定理论基础。

爆破应力波在地下工程围岩体中传播时，由于原岩应力及开挖卸荷导致应力重分布等因素的影响，围岩体具有梯度静应力。本课题分别通过对岩石具有不同均匀静应力和梯度静应力工况进行研究，表征出变化静应力和梯度静应力对岩石应力波传播衰减特性的影响规律及机理。主要研究成果如下：.(1) 研究了不同轴向静应力工况下岩石应力波的传播衰减特性，建立了具有一维静应力岩石应力波传播模型。应力波波速和响应频率随轴向静应力先增大后减小，而时空衰减系数先减小后增大。.(2) 研究了围压对岩石应力波传播衰减特性的影响。随着围压的增加，长、短试件反射系数的绝对值逐渐减小；短试件透射系数逐渐增大，长试件透反射系数与围压均呈二次函数关系。 .(3) 建立了具有一维静应力变截面岩石应力波传播模型，轴向静应力越大，应力波波形下降沿越陡，卸载峰值应力越大；幅值空间衰减系数随静应力的变化率与变截面率呈正相关关系。.(4) 研究了冲击速度和轴向静应力对岩石能耗特性的影响。岩石耗散能随冲击速度的增加呈二次函数关系递增；轴向静应力越大，递增幅度越来越小。.(5) 研制了一套对岩石长试件模拟梯度应力环境的试验装置，该试验方法和系统能较好地对试件模拟施加线性或非线性梯度静应力环境。.(6) 利用自主研发的梯度静应力试验装置，进行了不同梯度静应力工况下的应力波传播试验，研究了具有梯度静应力岩石应力波波形、幅值等应力波传播衰减特性及其机理特征。研究表明应力波波宽随应力梯度的增加而逐渐减小，应力波幅值随传播距离和时间均呈指数形式衰减。幅值空间响应强度βx随应力梯度k的增大近似指数式减小，空间衰减系数αx随应力梯度k先增加后减小，其中k=15.6MPa/m为由增加到减小的临界点。.(7) 基于试验数据，研究了具有梯度静应力岩石应力波频谱、主频等应力波频散特性及其机理特征。随着梯度静应力的增加，频谱线的开口大小逐渐增大，且频谱线的整体位置逐渐降低。应力波信号主频随着应力梯度的增加而逐渐增大，主频随传播距离的增加而增大。