裂隙岩体中弹性波传播特性试验及宏细观损伤本构模型研究

以不同加载方式下裂隙岩体中弹性波传播特性试验为基础,首先通过对比试验中弹性波波速、波幅与岩体宏观损伤的关系,给出了采用弹性波波幅来表征的裂隙岩体宏观损伤变量;其次利用统计强度理论定义了岩石的细观损伤变量,并基于连续损伤理论建立了宏、细观裂隙耦合的裂隙岩体损伤本构模型;最后结合试验数据对该模型进行了验证与分析。研究表明:完整岩体中细观裂隙的起裂和扩展对岩体中传播弹性波的波幅和波速的影响较小,而裂隙岩体中宏观裂隙的张开和闭合对弹性波波幅和波速的影响较大。裂隙岩体在外力作用下时,弹性波波速和波幅的变化规律类似,相较于弹性波波速,弹性波波幅对裂隙岩体宏观损伤的变化表现的更敏感,可用来定义裂隙岩体的宏观损伤变量。不同加载方式下裂隙岩体的损伤特性与宏、细观裂隙以及其所处的应力状态相关,基于宏、细观裂隙耦合的裂隙岩体损伤本构模型可以较好地反映不同加载方式下裂隙岩体的损伤力学特性。在三轴压缩试验中,宏观裂隙对岩体轴向压应力方向上损伤的影响主要体现在试验的中后期阶段,在三轴拉压试验中,宏观裂隙对岩体轴向拉应力方向上损伤的影响贯穿于试验全过程中。     

岩石声发射特性试验研究

对取自柿竹园矿的花岗岩、矽卡岩,进行声发射特性试验研究以及岩石的声波波速测试,得到岩石的纵波速度及在受单轴压力下岩石破坏过程中的应力-应变以及声发射参数与应力、时间之间的关系,为矿山的安全生产、避免地压灾害提供了决策依据。     

深部冲击倾向煤岩循环加卸载的纵波波速与应力关系试验研究

研究了单轴循环加卸载条件下深部冲击倾向煤岩样应力与纵波波速的耦合关系,基于煤岩试样在弹性阶段纵波波速变化梯度大,塑性阶段波速变化趋于平缓的特征建立了应力与纵波波速之间的试验关系模型,并对模型参数进行了分析。研究表明：①由于闭合的孔隙和裂隙又重新张开,颗粒之间的压实程度减弱,煤岩试样卸载过程中,随着应力的降低,波速也降低;②部分裂隙和孔隙在压密阶段发生永久闭合,造成应力降低后再无法张开,因此下一循环的开始纵波波速值要大于第一个循环开始时的波速值;③与实测值的相关系数计算结果表明,试验关系模型具有较高的拟合度,很好地体现了试样纵波波速变化对载荷的敏感程度。     

含水率对红砂岩特征应力及声发射特性的影响

为了探讨含水率对红砂岩特征应力及声发射响应特征的影响,利用RMT-150C岩石力学压力试验机和PCI-II AE win型声发射系统开展了不同含水率条件下红砂岩试件单轴压缩试验。对水侵蚀作用下红砂岩的物理力学参数及特征应力演化机制进行了分析,探究在不同含水率条件下声发射(宽、窄频带)时间序列模式的演化规律,同时基于累计声发射事件数与统计力学理论构建了红砂岩的损伤演化模型。试验结果表明:(1)P波波速随着含水率增加呈现先减小后增加的变化趋势,当含水饱和度达到临界值时,P波波速会降到最低值;(2)窄频带接收传感器接收的声发射信号与红砂岩内部颗粒间的摩擦作用息息相关,而宽频带接收传感器接收的声发射信号与红砂岩内部裂纹演化存在着内在联系;(3)水对声发射事件率(宽频带)在裂纹非稳定扩展阶段影响相对较为显著,对特征应力与强度的比值影响甚微,但对各阶段应变百分比作用效果相对较为明显,随着含水率的增加,红砂岩试件的失效模式由脆性破坏逐渐向延展性破坏转变;(4)随着含水率的增加,声发射事件率(窄频带)活跃期呈现后移的变化趋势,干燥、自然与饱和状态下岩石试件声发射模式分别为主震型、前震–主震–后震型和群震型;(5)基于声发射累计事件数(宽、窄频带)与统计力学理论构建的损伤演化模型可将不同含水率条件下红砂岩试件的损伤过程分为4个阶段:初始损伤阶段、损伤稳定发展阶段、损伤加速发展阶段及损伤破坏阶段。     

盐岩三轴压缩破坏与声波声发射特征试验研究

利用岩石声波-声发射一体化测试系统与应力加载装置,系统地研究了三轴压缩试验中盐岩的变形破坏特征与声波声发射活动规律。结果表明：（1）三轴加载试验中,盐岩的破坏过程分为压密与弹性压缩阶段、裂纹产生与稳定增长阶段、裂纹加速增长阶段和应变硬化阶段。阶段Ⅰ中,盐岩纵横波波速略微上升,并伴随少量的声发射事件;阶段Ⅱ中,盐岩的声发射活动开始活跃,超声波波速稳定;阶段Ⅲ和阶段Ⅳ中,岩石的声发射事件数量大幅度上升,纵波波速保持稳定,横波波速呈现明显地下降趋势。（2）盐岩的声波与声发射特征与试验围压应力密切相关。围压水平越低,受载盐岩破坏过程中的波速变化率越大;围压水平越高,盐岩超声波波速变化率越小。根据对试验数据的分析,当盐岩轴向应变达到10%,围压条件为5、10、15、20 MPa时盐岩的声发射事件数量分别为16 271、8 764、3 041、906个,围压对盐岩破坏过程的声发射活动有较大的影响,显示了围压致密效应。     

基于超声检测的软岩单轴流变损伤试验

采用软岩相似材料进行了2种不同流变加载方式下的单轴流变损伤破坏试验,并通过超声检测技术获得了软岩在各级流变阶段的超声信号。试验结果表明:软岩相似材料具有强烈的黏、弹、塑性变形特征,选用西原模型对软岩各级流变过程进行模拟较为合适;当应力达到或超过软岩试件单轴抗压强度的80%时,纵波波速曲线才会在流变过程中持续下降,出现可检测损伤迹象,而首波振幅曲线波动大,检测结果不准确;以波速定义损伤变量,得到了软岩流变过程损伤演化曲线。试验结果能为软岩工程长期流变下的结构稳定性提供依据。      

砂岩的高温损伤与模量分析

通过定义砂岩试样压缩破坏过程的4个阶段模量,对高温（25℃～1 000℃）后砂岩压缩破坏的应力-应变全过程进行定量研究。分析砂岩高温后的模量特征和超声特性,并基于压缩模量定义高温作用后砂岩试样的热损伤因子,对不同温度作用后的砂岩试样进行损伤分析,发现高温后砂岩压缩破坏具有明显的阶段性特征;4个阶段的阶段模量随温度的变化规律各有不同;压密模量与纵波波速具有很强的相关性;基于压密模量定义的高温后砂岩试样热损伤因子避开了基于纵波波速定义方法,未考虑温度对密度和泊松比影响的缺陷,更具科学性;25～200 ℃温度区间内砂岩试样热损伤对温度最敏感。研究成果对高温环境岩石工程具有一定的指导意义。     

岩石声波-声发射一体化测试装置的研制与应用

为了研究岩石破裂过程中的超声波波速值和声发射活动规律,自主研发了一套岩石声波、声发射一体化同步测试装置,它主要由声波测试系统、声发射测试系统和数据采集、存储、处理系统三部分组成。声波和声发射测试系统通过试验机底座接口与数据采集、存储、处理系统相连,并受后者控制,可以独立的同步监测岩石的波速与声发射信息;数据采集、存储、处理系统可以实时采集、存储两类声学数据,并实现二者的识别、筛分及后期处理。为了验证该装置的适用性,将其应用于盐岩、大理岩、花岗岩的单轴加载试验及盐岩的三轴加载试验中,均获得了较为理想的波速-应力变化规律、岩石声发射活动趋势及震源定位图。结果表明,所研发的测试装置可以满足单轴、三轴应力状态下岩石破裂过程中声波与声发射信息的同步监测,设备性能稳定,测试数据精度较高,可为探索岩体的破裂损伤机制及损伤评价提供重要的研究手段。     

基于弹性波波速的降雨型滑坡预警系统

降雨是诱发滑坡最主要的因素。为减少滑坡灾害造成的人员伤亡和经济损失,滑坡早期预警系统成为了最佳选择之一。根据弹性波传播的基本原理和基于降雨型滑坡变形破坏的特点,提出利用弹性波波速来反映边坡表面土体含水率和位移的变化。开发研制了一套三轴渗流-弹性波测试三轴仪和相关系统。该装置能让水从底部渗入土体,模拟降雨入渗土体的过程,同时能测试弹性波波速。试验过程中同步测试含水率、变形和弹性波波速的变化。还进行了降雨滑坡模型试验。利用三轴弯曲元注水试验和降雨滑坡模型试验,深入分析和研究降雨引起的土体滑坡过程与弹性波波速演化规律,揭示波速与含水率和变形的耦合关系。研究结果表明,弹性波波速随着含水率的增大而缓慢减小,随着变形的增大而急剧减小,临近失稳时,波速骤然减小。根据试验结果对含水率和变形导致弹性波波速减小可能的机制进行了解释,提出弹性波在波速骤然减小时发出滑坡预警。研究结果为滑坡防灾减灾和预测预报提供新的方法和可靠的依据。     

花岗岩样品高温后损伤的试验研究

对河南省某地产25块花岗岩样品进行高温预热处理,测量了加温前后弹性纵波波速,并对样品进行单轴压缩应力-应变全过程试验。通过以上试验,给出如下结果：温度对岩石损伤变化的作用;温度对岩石裂隙密度和损伤应变能释放率的影响。实验结果验证了花岗岩的塑性应变主要与偏斜应力产生的形状改变比能有关,而与体积改变比能的关系不大。     

波速测试技术在场地抗震评价中的应用研究

波速测试技术是地震勘探方法之一,也是一种简便、快速、准确的原位测试技术。它通过获取的地震波在经过不同深度的岩、土层的直达波旅行时,求得纵波、剪切波波速,进而通过弹性波理论,计算出岩、土层动弹性力学参数,同时也可以根据剪切波的波速,来划分场地土类型和建筑场地类别,以及计算卓越周期,这些参数可以为场地抗震设计及地震安全性评价提供依据。这里简述了波速测试技术的工作原理和野外实测技术,以及数据处理和资料解释全过程,并且结合某一建筑场地的实例,说明了波速测试技术在场地抗震评价中的应用及其效果。     

不同岩性及含水率的岩石声波传播规律试验研究

利用智能声波仪对红砂岩、大理岩和花岗岩试样在干燥及饱和条件下进行了声波纵波透射试验,研究声波在岩石中传播的速度特征,同时利用傅里叶变换及小波变换研究声波在岩石中传播的波形、波幅衰减规律、波谱特征。结果表明： （1）红砂岩、大理岩和花岗岩在饱和状态下的纵波波速比其在干燥状态下略高。（2）岩石纵波速度受到岩石的致密程度、孔隙度、密度及硬度的影响。（3）在同样的激发信号下,饱水的砂岩、大理岩、花岗岩岩样声波信号能量集中在低频部分较多,而干燥岩样声波信号能量集中在高频部分较多。（4）饱水的3种岩样声波信号能量衰减较快,尾波不发育;干燥的3种岩样声波信号能量衰减较慢,尾波较发育。（5）穿过岩石的声波信号的波速、波形的时域特征、频域特征及时-频域特征能在一定程度上反映出岩石内部的孔隙及微裂隙的发育情况和岩石含水情况等特征。     

Experimental studies on the effects of fracture on the P and S wave velocity propagation in sedimentary rock (“Calcarenite del Salento”)

Experimental studies were carried out in laboratory in order to investigate the effects of fracture on compressional (P) wave and shear (S) wave velocity propagation and therefore the relations between seismic properties and rock mass parameters. The discontinuity index, I_d, fracture density parameter C, linear fracture parameter Γ and the rock quality designation (RQD) were used to describe the rock mass parameters. These parameters are analyzed and then related to the seismic properties. Four vertical aligned fractures were created on an intact calcarenite block, 0.6 m long, 0.4 m thick and 0.4 m width, by sawing. The measures were carried out in four different blocks of cacarenite, having the same physical properties, and in four different phases: in first block the fractures were filled with air; in the second block the fractures were filled with “terra rossa”; in third block the fractures were filled with wet “terra rossa” and in the fourth block the fractures were filled with clay. The test results were statistically analysed using the method of least squares regression and polynomial relationships with high correlation coefficient were found between the fractured rock parameters and P-wave, S-wave velocities and V_p/V_s ratio. The investigations suggest that the P-wave and S-wave velocities decrease with increasing the fracture parameters, while the V_p/V_s ratio increases with decreasing the fracture parameters.

Furthermore the results of the experimental studies were applied on the seismic refraction tomography data acquired in a great measurements campaign undertaken in the Adriatic salentina coast (south Italy) in order to monitor the coastal erosion.

The geophysical results, using the polynomial relationships between the fractured rock parameters and P-wave velocity, are in good agreement with the geomorphological and geological results.     

基于人工鱼群算法和SCA等效理论的井中横波速度预测方法

在建立页岩岩石物理模型的基础上,根据等效自相容近似(SCA)岩石物理模型,构建出岩石的纵波速度、横波速度与岩石密度、组分和孔隙度等的定量关系,得出使理论纵波速度和实际纵波速度最接近的孔隙纵横比,进而将该孔隙纵横比作为约束条件来实现横波速度预测。反演算法利用人工鱼群算法来计算最佳孔隙纵横比,并将预测的横波速度与实际测得的横波速度对比,证明了人工鱼群算法的有效性。     

Experimental and texture-derived P-wave anisotropy of principal rocks from the TRANSALP traverse: An aid for the interpretation of seismic field data

A representative suite of deformed, metamorphic rocks from the TRANSALP reflection seismic traverse in the Eastern Alps was studied in the laboratory with respect to elastic properties and whole-rock texture. Compressional wave (P-wave) velocities and their anisotropies were measured at various experimental conditions (dry, wet, confining pressure), and compared to the texture-related component of anisotropy. Here ‘texture’ refers to crystallographic preferred orientations (CPOs), which were determined by neutron texture goniometry. In gneisses and schists P-wave anisotropies are mainly controlled by the microcrack fabric. In marbles and amphibolites CPO contributes very significantly to anisotropy. At 200 MPa confining pressure the degree of anisotropy is between 5% and 15%, depending on rock composition and/or CPO intensity. Special emphasis was also put on discussing possible effects of fluids on seismic velocity and anisotropy. Distributions of water-filled microcracks and pores are distinctly anisotropic, with maximum contribution to bulk rock velocity mostly parallel to the foliation pole. Decreasing P-wave velocity and increasing anisotropy of immersed samples may be explained by crack-induced changes of the elastic moduli of bulk rock. The main conclusion regarding interpretation of TRANSALP data is that strong reflections in the deep Alpine crust are probably due to marble–gneiss and metabasite–gneiss contacts, although P-wave anisotropy and boundaries between zones of ‘dry’ or ‘wet’ series may contribute to reflectivity to some extent.     

岩石脆性临界破坏的波速特征分析

根据岩石加载破坏过程中应力-应变和波速-应变曲线所反映的的波速变化特征,研究了岩石声波传播速度与其加载变形过程的相关性。研究表明:岩石破裂前波速及特征参数随着变形破坏阶段变化会有显著改变,特别是应力水平到达70%⁸0%之后,当加载破坏过程中岩石的裂隙大量增加后波速参数出现突变。这是由于在膨胀点附近岩石中微裂隙迅速丛集式增长,改变了岩石内部的微观结构,导致岩石波速降低。伴随着波速降低,波速走时急剧增大,离散度增大;S波和P波的振幅减小,但其振幅比急剧增大;S波、P的波Q值也会出现突变。通过对岩石加载过程中的波速变化与应力-应变曲线之间的关联性分析,利用波速信息变化可以实现对岩石脆性破裂前兆的识别。     

Experimental Study on Acoustoelastic Character of Rock Under Uniaxial Compression

This paper made a research about the change rule of elastic wave velocity with stress applied on rock from theoretical and experimental aspect. Firstly, a mathematical model of P-wave velocity and confining pressure of rock was set up from the point of acoustoelastic character. Effect of axial stress on P-wave velocity in granite and sandstone during uniaxial compression process was studied experimentally by using GAW-2000 rock mechanical testing system and RSM-SY5 ultrasonic wave testing system, and the relation curves of axial stress with P-wave velocity were obtained. Based on test data, acoustoelastic theoretical formulas of granite and sandstone were established and the best empirical formulas were fitted by using regression method. Meanwhile, a comparative analysis of the empirical and theoretical calculated values was carried out. Finally, the reliability of applying acoustoelastic theoretical formula in hard rock range was further verified based on the experimental data of granitic gneiss. The results show that the P-wave velocity experiences a rapid increase, gentle increase and then a sharp fall during the uniaxial compression process. The B-value in acoustoelastic theoretical formula (proportion coefficient determined by elastic modulus and third-order elastic constant) decreases exponentially with axial stress. The acoustoelastic theoretical formula can effectively reflect the relationship between rock acoustic velocity and stress within the allowable error, which can be the theoretical foundation of acoustoelastic geo-stress measurement of subsurface rock mass.     

Long-Wavelength Elastic Wave Propagation Across Naturally Fractured Rock Masses

Geophysical site investigation techniques based on elastic waves have been widely used to characterize rock masses. However, characterizing jointed rock masses by using such techniques remains challenging because of a lack of knowledge about elastic wave propagation in multi-jointed rock masses. In this paper, the roughness of naturally fractured rock joint surfaces is estimated by using a three-dimensional (3D) image-processing technique. The classification of the joint roughness coefficient (JRC) is enhanced by introducing the scan line technique. The peak-to-valley height is selected as a key indicator for JRC classification. Long-wavelength P-wave and torsional S-wave propagation across rock masses containing naturally fractured joints are simulated through the quasi-static resonant column (QSRC) test. In general, as the JRC increases, the S-wave velocity increases within the range of stress levels considered in this paper, whereas the P-wave velocity and the damping ratio of the shear wave decrease. In particular, the two-dimensional joint specimen underestimates the S-wave velocity while overestimating the P-wave velocity. This suggests that 3D joint surfaces should be implicated to obtain the reliable elastic wave velocity in jointed rock masses. The contact characteristic and degree of roughness and waviness of the joint surface are identified as a factor influencing P-wave and S-wave propagation in multi-jointed rock masses. The results indicate a need for a better understanding of the sensitivity of contact area alterations to the elastic wave velocity induced by changes in normal stress. This paper’s framework can be a reference for future research on elastic wave propagation in naturally multi-jointed rock masses.     

P- and S-wave velocities and densities in silicate and calcite rocks from the Peloritani Mountains, Sicily (Italy): The effect of pressure, temperature and the direction of wave propagation

The Peloritani Mountain Belt (north-eastern Sicily) represents the connection between the Southern Appenninic Range and the Appenninic Maghrebid Chain. The lithotypes outcropping in a 36 km long and approximately 8 km wide area in the eastern part of the Peloritani Mountains are considered to represent most properly the composition of the lower crust. We selected 7 representative samples of silicate rocks (amphibolite, paragneisses, augen gneiss, phyllitic quartzite, pegmatitic rock) and 3 samples of calcite rocks (calc-schist, marbles) for the petrophysical measurements. Measurements were done on sample cubes of dry rocks in a multi-anvil apparatus. Raising of pressure gives rise to velocity increase, but the rate is different in the silicate and calcite rocks and closely related to progressive closure of microcracks. Linear behaviour is approached above about 200 MPa. Increasing temperature at 600 MPa decreases velocities in most silicate and in the calcite rocks with almost linear slopes. Substantial anisotropy of P- and S-wave velocities and shear wave splitting is found in both rock types. The residual anisotropy observed above about 200 MPa is attributed to lattice preferred orientations (LPO) of major minerals. 3D velocity calculations for an amphibolite, a paragneiss and a marble sample based on the LPO of hornblende, biotite and calcite, respectively, confirm the experimental findings of a close relationship between velocity anisotropy, shear wave splitting, shear wave polarization, lattice preferred orientation and the structural frame of the rocks (foliation, lineation). In the silicate rocks, the intrinsic (600 MPa) average P-wave velocities and Poisson's (Vp / Vs) ratios exhibit a tendency for a linear increase with densities, whereas the three calcite rocks cluster at markedly higher P-wave velocities and Poisson's (Vp / Vs) ratios, compared to their densities. In the silicate rocks, there is also a linear trend for an inverse relationship between the SiO₂ content, density and the Poisson's (Vp / Vs) ratio, respectively.     

不同损伤程度下岩石力学参数变化的声波测试

声波波速变化可有效表征岩体损伤程度。通过对岩样进行人工预损,利用声波检测标定岩样的不同损伤程度,然后通过三轴压缩试验来研究不同损伤程度下岩石的力学特性,建立了声波速度下降幅度与岩体力学参数变化幅度间的关系。研究表明,当岩样的声波速度下降5%～8%时,黏聚力c值降低15%～25%,内摩擦角? 值则升高14%～32%,因此,用声波速度的下降幅度来描述岩体参数的变化是可行的。根据现场实测的岩体损伤区内的声波速度的变化值,可以从一定程度上估计岩体参数的跌落情况,从而更进一步地说明损伤区内岩体的承载力。