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1.
随着页岩气开采、废水回注和CO2地质封存工程活动的进行,储层应力环境改变诱发地震的问题得到广泛关注,研究储层岩石变形破裂和声发射规律对于理解诱发地震活动具有重要意义。本文选取了页岩、致密砂岩和白云岩开展三轴压缩声发射试验,获取了空间裂缝形态,揭示了不同类型储层岩石的变形破裂过程和声发射特征。结果表明：(1)页岩的扩容应力与峰值应力比最高,其次为白云岩和致密砂岩,表明页岩主要发生脆性破坏。(2)岩石结构对裂缝扩展和强度具有明显影响,页岩层理发育,抗压强度和裂缝形态各向异性显著。当层理角度为0°时,试样发生剪切-拉张复合型破坏。当层理角度为30°和60°时,试样主要发生剪切破坏。当层理角度增大至90°时,试样主要发生拉张破坏。致密砂岩破裂形成剪切主裂缝,白云岩形成两条剪切主裂缝和微裂缝。(3)不同类型储层岩石破裂过程声发射特征差异显著。页岩在扩容应力点附近有少量声发射活动,达到峰值应力时,声发射活动迅速增强。致密砂岩仅在破裂瞬间有少量声发射活动。相比之下,白云岩在裂缝非稳定扩展阶段和峰后阶段声发射活动显著。因此,在工程实践中需要根据微震监测调整施工措施,避免页岩作为储... 相似文献
2.
《Russian Geology and Geophysics》2014,55(10):1223-1228
Earthquake nucleation and fracture propagation in deformed rocks generate elastic waves, within acoustic frequencies. Strain-induced acoustic waves appear both in field tectonic structures and in laboratory samples, thus making laboratory acoustic emission (AE) data from load tests suitable to interpret natural seismic processes. However, laboratory tests are commonly run at room temperature, while the natural rocks at the earthquake origin depths are as hot as hundreds of degrees centigrade. We report AE data for thermally and mechanically loaded granites subjected to impact fracture at different temperatures. The energy distribution in the time series of acoustic signals emitted from fine-grained granite fits a power law of the type of the Gutenberg-Richter relationship at temperatures from 20 to 500 C. Medium- and coarse-grained samples behave in this way only within 300 C but show a Poissonian (random) AE energy distribution above 300 C. 相似文献
3.
通过对含水砂岩进行单轴加载声发射试验,获取声发射信号。对整个加载过程声发射信号进行FFT变换,发现随着加载地进行,声发射信号的峰值频率由60 kHz下降到40 kHz,平均主频比自然状态下的砂岩平均主频降低了1 kHz;通过分析能量和岩石声发射事件数之间的关系,发现能量与对应声发射事件数之间的比值越大,说明能量是由较大的破裂导致的,而能量值与对应声发射事件数之间的比值越小（数量级在104以下）,说明能量是由多个小破裂同时产生积聚而成的;用Welch法做功率谱估计,发现得到的声发射信号其功率谱大致分为A、B两种,B类功率谱对应信号的相位突变性强。选取一些较大能量信号,计算这些信号出现之前的B类型功率谱出现的几率,发现越接近破裂出现B类型功率谱的几率越大。研究结果为分析岩石破裂全过程的声发射特性提供了一条新的思路,也为声发射应用于岩石破裂失稳预报奠定了一定的工作基础。 相似文献
4.
本文主要研究花岗岩和砂岩两种脆性岩石的详细声发射特征。通过对花岗岩和砂岩样品进行单轴压缩试验,并在试验过程中监测样品破裂全程的声发射信号。对试验结果的分析包含了力学特性分析和声发射特性分析,声发射特性分析使用了多种参数:累积声发射计数、累积声发射能量、AF值、RA值、b值。研究主要获得了如下结果:（1）获取了岩石样品的变形参数与强度参数,并分析了其离散性;（2）岩石样品内部颗粒的胶结强度与结构的均匀性对累积声发射计数、累积声发射能量的影响;（3）需要通过进一步试验研究来确认采用AF和RA值来区分岩石类材料张拉和剪切裂纹模式的合理性及其阈值;（4）砂岩样品在接近破坏时,微裂缝活动仍然占据主导地位。文章对脆性岩石样品在单轴压缩条件下的力学特性和声发射特性进行了详尽细致的分析,发现了单轴压缩条件下脆性岩石的一些重要特性,为进一步的试验研究工作提供了基础。 相似文献
5.
I. M. Simanovich 《Lithology and Mineral Resources》2007,42(1):75-83
The simplest intergranular cleavage and foliation of clayey rocks are typical of postsedimentary lithogenesis of folded terrigenous complexes at passive continental margins if the rocks do not contain metamorphic minerals. Cleavage zones coincide with metagenesis (anchimetamorphism) zones. Cleavage is often superimposed on the rock fabric formed in the process of subsidence lithogenesis (e.g., in the Verkhoyansk terrigenous complex). In other cases, cleavage in terrigenous rocks is regarded as the final stage of the development of their microfabric formation related to folding (e.g., Jurassic sequence of southern Dagestan). 相似文献
6.
进行岩石摩擦滑动变形演化过程的声发射特征试验研究。以数字散斑相关方法和声发射系统为试验监测手段,采用双面剪切模型试验方法,开展界面摩擦滑动速率与声发射振铃计数、界面摩擦滑动位移与声发射累计能量、试件变形能密度与声发射b值的对应关系研究。结果表明：（1）声发射振铃计数演化受岩石界面摩擦滑动速率影响,界面摩擦滑动速率的突变与声发射振铃计数激增有较好对应关系;（2）界面摩擦滑动位移与摩擦滑动过程中声发射累计能量演化趋势具有较好的对应关系,可以利用声发射累计能量对岩石摩擦滑动位移的变化趋势进行定性判断;（3）通过声发射b值演化分析可以得出,在剪应力缓慢增长阶段,界面摩擦滑动以随机分布的小尺度微破裂为主;在剪应力线性增长阶段后期,界面摩擦滑动以锁固段的大尺度微破裂为主;在剪应力波动增长阶段,岩石摩擦滑动失稳既可能是由小尺度微破裂为主引发的状态转化,又可能是由以锁固段大尺度微破裂为主引发的稳定状态转换。 相似文献
7.
Shear and extensional veins formed during the reactivation of the Magdala shear system at Stawell in western Victoria, Australia,
contribute to the formation of the auriferous Central and Basalt Contact lodes. Within this shear system is a range of fault
rocks accompanied by steep-dipping (>65°) quartz-rich laminated shear veins and relatively flat-lying extensional veins. Both
vein sets appear to have been a primary source for the host rock permeability during fluid flow in a regime of significant
deviatoric stresses. The macro- and microstructures suggest that the dilatancy, that produced mineralized veins, formed under
conditions of overpressure generated by fluid infiltration late in a tectonic regime. A new microfabric analysis technique
is used to investigate the quartz-rich veins, which allows rapid integration of the microstructure with the crystallographic
preferred orientations (CPOs). Both the shear and extensional quartz veins have a random CPO with ∼120° dihedral angles between
the quartz–quartz grains, which is typical of a metamorphic equilibrium microfabric. The microstructures indicate that the
quartz has undergone extensive grain adjustment in the solid-state, with grain shape and size affected by interfacial solution
(pressure solution) effects. These features are consistent with inferences from experimental rock deformation studies, where
grain boundary migration is enhanced in a water-rich environment. The onset of solution-transfer processes (pressure solution)
developed as the quartz microfabric stabilized and continued to modify the CPO and microstructure significantly. It is concluded
that grain growth and pressure solution are coupled diffusive mass transfer processes, related to fluctuations in pore fluid
pressures in a region undergoing deformation at near lithostatic pressures. 相似文献
8.
根据目前岩石声发射确定Kaiser点存在的问题采用小波包分析研究方法,在单轴加载岩石声发射试验的基础上,首先提出了基于小波包变换的Kaiser点信号的信噪分离方法,其次确定了Kaiser点信号的频率范围,最后利用小波包分析对岩石声发射信号的能量分布特征进行研究,得到了砂岩Kaiser点信号的特征频带。结果表明,小波包分析是处理岩石声发射Kaiser点信号的一种有效的方法,进而为AE法测量地应力确定Kaiser点奠定了一定的试验基础。 相似文献
9.
为了研究盐穴能源地下储库建造过程中,腔体围岩处在地温、卤水和地应力地质环境中盐岩的损伤演化特点,利用声发射技术分析盐岩受不同温度的饱和卤水作用后的单轴压缩损伤破坏过程。试验发现：在一定温度的饱和卤水中浸泡30 d后盐岩的单轴抗压强度和弹性模量有所降低,但降低的平均幅度很小;卤水对盐岩主要表现为溶蚀作用,而浸泡弱化作用非常小;单轴压缩过程中盐岩的应力-应变曲线与声发射-应变曲线具有较好的一致性,卤水浸泡后盐岩的累计声发射数随卤水的温度升高略有增加;卤水作用后盐岩试件的声发射率和累计数要小于无卤水作用盐岩;盐穴建造期盐岩受一定温度的卤水作用后盐岩的强度将出现一定弱化,但卤水也会促进损伤盐岩体的重结晶恢复,盐岩的这种特性有利于盐穴建造期安全和稳定。 相似文献
10.
Richa Shukla P. G. Ranjith S. K. Choi A. Haque Mohan Yellishetty Li Hong 《Rock Mechanics and Rock Engineering》2013,46(1):83-93
Acoustic emissions (AE) and stress–strain curve analysis are well accepted ways of analysing crack propagation and monitoring the various failure stages (such as crack closure, crack initiation level during rock failure under compression) of rocks and rock-like materials. This paper presents details and results of experimental investigations conducted for characterizing the brittle failure processes induced in a rock due to monocyclic uniaxial compression on loading of two types of sandstone core samples saturated in NaCl brines of varying concentration (0, 2, 5, 10 and 15 % NaCl by weight). The two types of sandstone samples were saturated under vacuum for more than 45 days with the respective pore fluid to allow them to interact with the rocks. It was observed that the uniaxial compressive strength and stress–strain behaviour of the rock specimens changed with increasing NaCl concentration in the saturating fluid. The acoustic emission patterns also varied considerably for increasing ionic strength of the saturating brines. These observations can be attributed to the deposition of NaCl crystals in the rock’s pore spaces as well some minor geo-chemical interactions between the rock minerals and the brine. The AE pattern variations could also be partly related to the higher conductivity of the ionic strength of the high-NaCl concentration brine as it is able to transfer more acoustic energy from the cracks to the AE sensors. 相似文献
11.
开展火烧岩烧变温度的识别对于火烧岩的形成及演化具有重要的指导意义。基于热Kaiser效应,通过火烧岩在热处理过程中的声发射累计能量以及参数RA(上升时间/振幅)和AF(平均频率)值的变化,对陕北神木张家峁火烧岩的阈值温度进行了预测。结果表明:火烧岩热声发射特征能有效识别火烧岩烧变温度,与火烧岩经历温度的岩相学分析基本一致;研究区火烧岩存在显著的地层烧变温度梯度,第1—第5层岩石烧变阈值温度逐渐升高,对于第6层和第7层岩石,最高温度超过700℃,对于第8层岩石,阈值温度为245℃;当热处理温度较低时,岩石内部沿晶拉张裂纹发育,超过600℃后,穿晶剪切裂纹所占比例开始增加,声发射信号出现二次增长,同时声发射出现平静期,累计能量曲线出现多个平台。火烧岩烧变温度的识别,对于煤矿防治水及围岩稳定性研究等具有重要的现实意义。 相似文献
12.
不同岩石破裂全过程的声发射序列分形特征试验研究 总被引：3，自引：0，他引：3
通过对不同岩性的岩石进行单轴压缩声发射试验,获取岩石破裂全过程中的载荷-轴向变形曲线及声发射参数,观察试件破裂失稳时的破坏情况,分析破坏过程的载荷变化关系。着重对比了不同岩石的不同力学性质、岩石声发射序列的时域特征和声发射序列的分形特征。研究结果表明,采用声发射率、能率可以很好地描述岩石破裂损伤的整个阶段;计算岩石声发射率、声发射能率的关联维数,可得出岩石破裂过程的声发射序列具有分形特征;岩石破裂过程的声发射分维值D反映了岩石内部微裂隙的统计演化规律;不同岩性的岩石破裂过程的声发射参数序列的分形特征具有一定的共性;归纳总结出岩体声发射序列分维曲线的演化模式,即波动→持续下降演化模式,提出可以将分维值的持续下降作为岩体破裂失稳的前兆。 相似文献
13.
在分析岩质边坡失稳过程中岩体力学性质和声发射产生的微观机理基础上,通过岩石声发射试验和岩质边坡声发射监测实例,研究了岩质边坡声发射特征,提出了岩质边坡失稳破坏的基本力学分类及其声发射的监测预报方法和判据,实现对岩质边坡失稳的预测预报。研究结果表明,边坡破坏前存在一次或多次声发射高峰。应用AE技术可以确定边坡在变形过程中应力集中活跃区;以抗滑力减小为主的岩质边坡,其失稳预报判据为大事件率在15次/ min以上,预报时间为几分钟至数小时。以下滑力增大为主的岩质边坡失稳的预报判据为大事件率在26次/ min以上,破坏时间为第一次声发射峰值期后的30～45 d。 相似文献
14.
为了客观重复制作与原岩结构面的岩性、表面形态和力学性质完全一致的试样,集成三维扫描和三维雕刻技术,提出了原岩结构面试样重构新方法。采用该方法制作了具有相同表面形态的大理岩结构面试样,开展了不同法向力下的直剪试验,并采用声发射技术对结构面剪切破坏过程进行了监测。结果表明：重构结构面试样与原始结构面试样具有高度相似性;结构面剪应力-剪切位移曲线可分为两类：剪胀滑移型和剪断跌落型;剪切破坏后结构面可明显地划分为两个区域：剪胀脱开区和剪断磨损区;提出了结构面剪切强度新公式,理论公式与试验结果更接近;结构面剪切过程中剪应力、能量率、计数、撞击率随时间的变化规律具有较好的一致性,声发射定位位置与剪切过程中结构面损伤破坏区域基本吻合。 相似文献
15.
Influence of Unloading Rate on the Strainburst Characteristics of Beishan Granite Under True-Triaxial Unloading Conditions 总被引：3，自引：2，他引：1
X. G. Zhao J. Wang M. Cai C. Cheng L. K. Ma R. Su F. Zhao D. J. Li 《Rock Mechanics and Rock Engineering》2014,47(2):467-483
Rockburst is a sudden and violent failure of rocks and it often occurs in hard rocks in highly stressed ground. Strainburst is classified as one type of rockburst and it often occurs in rocks near or at the excavation boundary. Deep insight into the strainburst phenomenon is essential for safe underground construction at depth. In this paper, an experimental laboratory study on the strainburst behavior of Beishan granite is presented. Based on in-situ stress measurement data from the Beishan area in China, a series of tests under different unloading rates were performed to investigate the strainburst process using a true-triaxial strainburst test system which was equipped with an acoustic emission (AE) monitoring system. In addition, a high-speed video camera was used to record and visualize the initiation and ejection of rock fragments as well as the sudden dynamic failure (strainburst) of the test samples. AE characteristics associated with the cumulative energy and frequency–amplitude distributions were analyzed. Characteristics of the microscopic structure of a fragment generated from one test were observed using a scanning electron microscope. The experimental results indicate that the degree of violence during failure and the associated AE energy release in the strainburst process are dependent on the unloading rate. When the unloading rate is high, the rock is prone to strainburst. On the other hand, as the unloading rate decreases, the failure mode changes from strainburst to spalling. In addition, the cumulative AE energy is not sensitive to unloading rates greater than 0.05 MPa/s. When the unloading rate is less than 0.05 MPa/s, the cumulative AE energy shows a marked decreasing trend during rock failure. 相似文献
16.
An Integrated Study of the Dynamics of Electromagnetic and Acoustic Regimes During Failure of Complex Macrosystems Using Rock Blocks 总被引：1，自引：0，他引：1
Kamel Baddari Anatoly D. Frolov Victor Tourtchine Fayçal Rahmoune 《Rock Mechanics and Rock Engineering》2011,44(3):269-280
The development of the failure process in complex macrosystems using large rock samples subjected to biaxial compression has
been studied by means of electromagnetic radiation (EMR) and acoustic emission (AE). In order to increase the stage of macrofailure
development, a special procedure of rock loading was used to reveal regularities of nucleation and evolution of electromagnetic
and acoustic structures. The synchronised measurements of EMR and AE allowed the control of the stress–strain state in the
rocks and the structural developments of fracturing. Non-homogeneous distribution of the rock spatial crystalline structure
subject to load leads to a mosaic distribution of EMR and AE characteristics. As a result, the crack scale effect may be observed
in the EMR and AE structure behaviours. The EMR and AE following the failure at different levels behave differently according
to the difference in the scale and type of cracks. Intense high-frequency EMR pulses were recorded during the initial stage
of microcrack generation occurring prior to major failure of material. This was not the case for AE. The nucleation and development
of the macroscopic progressive failure evolution caused an alternation in energetic and frequencial properties of electromagnetic
and acoustic events. It has been detected that the tensile cracks were more efficient than shear cracks in capacity of EMR
generation. The analysis of self potentials allowed reaching the maximum of registered anomalous variations in the stage of
microcracking interaction. This stage showed an increase in the EMR activity, which implies the nucleation of microcracks
in various regions of rock interfaces. The gradual accumulation of these defects led to weakening some parts of the rock along
with a disintegration of electric anomalies, increase of AE and a significant fluctuation in the rate of EMR. When crack concentration
attains its critical value, which results in the formation of dangerous macroscopic failure of higher level, AE shows an intense
activity as well as an EMR lower frequency. The hierarchical development of rock failure using the ratio of the average crack
size and the mean distance between cracks as a statistical concentration criterion is used to control the boundary of the
transition from small dispersed cracks accumulation to gradual crack merger and the formation of the main macrofailure. These
results could be transferred into larger scale levels to forecast dynamic events in the earth crust. 相似文献
17.
Richard P&#x;ikryl 《Engineering Geology》2006,87(3-4):149-162
Rock microfabrics were quantified by image measurement system (petrographic image analysis) of thin sections. Along with common measured parameters (grain area and size, length of major and minor axes and their orientation), some quantitative parameters (aspect ratio, grain boundary smoothness) and fabric coefficients (micropetrographic quality index (K), “texture” coefficient (TC), indexes of interlocking (t) and grain size homogeneity (g)) were determined. The reliability of these parameters for the evaluation of geomechanical properties was tested on the set of granitic rocks showing pronounced variability in rock mechanical properties. None of the tested rock fabric coefficients or parameters proved a close correlation to rock mechanical properties except grain size. Based on experimental findings, the grain size is, along with porosity, the controlling factor of rock mechanical properties of genetically and mineralogically similar rocks. Obliteration of the real effects of rock fabric parameters on the mechanical properties of rocks by application of complex fabric coefficients disables their practical use in petrography applied to geomechanics. 相似文献
18.
通过开展含预制单裂隙花岗岩的真三轴单面临空岩爆试验,并利用高速摄像系统和声发射（acoustic emission,简称AE）系统监测岩爆过程,探究了不同产状裂隙岩石的破坏模式、强度变形和声发射演化特性,分析了裂隙产状与岩爆过程及弹射动能之间的关系,对比了含裂隙岩石岩爆发生机制与无裂隙完整岩石的差异。有关力学特性的分析表明,随着裂隙倾角的减小,岩样破坏模式大体呈现由“内剪外劈”向“Z型斜剪”变化的趋势,裂隙对岩石强度的削弱作用不断增大。当裂隙倾角小于30°时,岩石峰值应力普遍仅为完整岩样的一半左右;小倾角裂隙的长度越大,岩样岩板劈裂现象变得显著,形成岩爆坑略微变大,且强度折减幅度越大,峰值轴向应变相应变小;裂隙位置向临空面靠近会加剧岩板的劈裂效应,塑性阶段普遍会产生较大变形并萌生大量裂纹,当裂隙已出露且切断临空面将不易形成岩爆坑。有关岩爆过程及弹射动能的分析表明,随着裂隙倾角的减小,岩样弹射动能呈现先显著降低后小幅回升的变化规律,30°倾角为转变拐点;岩样内部裂隙距临空面越近,裂隙岩样的弹射动能越小;树脂填充裂隙使得岩样弹射动能极大提升,而水泥填充的则无明显提升。有关声发射特征的分析表... 相似文献
19.
脆性对岩石破裂机制及声发射特性具有重要影响。采用花岗岩及大理岩两种不同岩性的岩石,开展了单轴压缩及声发射测试试验,获取了两种岩石的强度及变形特性,并对其脆性大小进行定量评价,分析了单轴压缩过程中两种岩石声发射能量演化特性,结合声发射b值计算结果及其物理意义,对比了两种岩石破裂机制的差异性。结果表明:(1)试验所采用的两种岩石,花岗岩的σcd/σp之比介于0.676~0.745之间,平均为0.706,而大理岩的σcd/σp之比介于0.439~0.615,平均为0.52;(2)基于脆性评价指标,结合试样宏观破坏现象及形态,本次试验采用的花岗岩其脆性大于大理岩;(3)岩石脆性程度越大,在裂纹不稳定扩展阶段,在产生相同的轴向压缩变形的情况下,环向变形量越大;(4)强脆性的花岗岩在裂纹不稳定扩展阶段持续出现高能级的声发射信号,而弱脆性的大理岩则表现出能量持续降低的变化趋势,峰值强度后,弱脆性的大理岩其高能级能量的声发射信号更活跃;(5)单轴压缩下,与大理岩相比,花岗岩破坏过程中大尺度的破裂事件所占比例较大。 相似文献
20.
Indicators of critical point behavior prior to rock failure inferred from pre-failure damage 总被引：4，自引：0，他引：4
To investigate possible indicators of critical point behavior prior to rock failure, the statistical properties of pre-failure damage were analyzed based on acoustic emission events (AE) recorded during the catastrophic fracture of typical rock samples under differential compression. AEs were monitored using a high-speed 32-channel waveform recording system. Time-dependent statistics, including the energy release rate, b-value of the magnitude–frequency distribution, fractal dimension and spatial correlation length (SCL) of the AE hypocenters were calculated for each data set. Each parameter is a function of the time-to-failure and thus can be treated as an indicator of the critical point. It is clear that the pre-failure damage evolution prior to catastrophic failures in several common rock-types is generally characterized by: 1) accelerated energy release, 2) a decrease in fractal dimension and SCL with a subsequent precursory increase, and 3) a decrease in b-value from 1.5 to 0.5 for hard rocks, and from 1.1 to 0.8 for soft rocks such S–C cataclasite. However, each parameter also reveals more complicated temporal evolution due to either the heterogeneity of the rock mass or the micro-mechanics of shear fracturing. This confirms the potential importance of integrated analysis of two or more parameters for successfully predicting the critical point. The decreasing b-value and increasing energy release may prove meaningful for intermediate-term prediction, while the precursory increase in fractal dimension and SCL may facilitate short-term prediction. 相似文献