断裂岩石粗糙性与岩体抗剪强度和机理的实验研究

为了分析岩体的长期力学行为,揭示断裂岩体失稳破坏的机理,对岩石断裂面的粗糙性进行了实验研究。将边长为50mm的砂岩试件,分别通过纯剪破坏方式和巴西劈裂拉破坏方式,制作出2类存在粗糙面的断裂岩石,每类选取3个试件进行剪切蠕变实验。对加载过程中的断裂岩石进行激光扫描,计算岩石断裂面的粗糙度和起伏度。实验研究表明:剪切蠕变过程中,断裂表面有粗糙化或光滑化的趋势。构成断裂岩石长期抗剪强度的机制主要有两个:一是细观凹凸体的抗剪断能力,另一个是宏观凹凸体的抗摩擦能力。无论哪种破坏方式,在加载过程中,这两种机理都是交织在一起共同作用于受载岩体上,并随时间或剪位移的增加而相互转换的,而且所发挥作用的主次也有所不同。     

神东矿区不同赋存深度沉积岩抗拉强度与断裂韧度研究

为研究神东矿区不同赋存深度沉积岩抗拉及断裂性能,利用声发射监测系统对神东矿区不同赋存深度沉积岩样品巴西劈裂加载过程中的声发射参数进行监测,探讨了岩样抗拉强度、I型断裂韧度及两者比值k随赋存深度的变化规律;分析了劈裂破坏过程中损伤演化、破坏特征及前兆信息。结果表明:抗拉强度和断裂韧度随赋存深度增加而增大,且二者均与赋存深度呈幂函数关系,埋深-300 m以浅岩样的抗拉强度和断裂韧度分别在0. 5 MPa和0. 15 MPa·m1/2以下,而-300 m以深岩样则分别在1. 0 MPa和0. 15 MPa·m1/2以上;岩样抗拉强度与断裂韧度的比值k也随赋存深度的增加而增大,且与赋存深度呈对数函数关系,即埋深-300 m以浅岩样k值为2～3,-400 m左右k值为3～6,-500 m以下k值相对离散。同时,神东矿区不同赋存深度岩样破坏为张-剪混合型,张拉破坏贯穿整个破坏过程,但剪切破坏发生时间不同,即-300 m以浅岩样剪切破坏发生在峰后阶段,而-300 m以深岩样剪切破坏发生在峰前阶段;不同赋存深度岩样在峰值强度前均会出现破坏前兆点,-300 m以浅岩样(除中粗砂岩外)基本在应力峰值的70%～90%,而-300 m以深多在应力峰值的92%以上;可以看出沉积岩失稳预警时间随赋存深度增加而减少,且随深度增加其失稳破坏更加迅速且剧烈。     

岩石点荷载强度与单轴抗压强度关系研究

点荷载试验是一种在工程现场快速确定岩石单轴抗压强度的方法。自国际岩石力学协会建议采用以来,得到了广泛的研究和应用。点荷载强度指标和单轴抗压强度之间的变换关系式存在较大的不确定性,影响该关系的因素较多,例如修正系数、点荷载强度标准值等。以贵州紫金水银洞金矿多个采场顶板岩石的点荷载试验数据为基础,探讨了不规则点荷载强度指标IS和点荷载强度标准值IS(50)之间的修正系数F的变化情况,分析比较了目前常用的四种计算方法获得的点荷载强度标准值IS(50),并对点荷载强度标准值IS(50)与岩石单轴抗压强度σC进行曲线拟合和线性拟合比较,最后得到了该矿顶板的单轴抗压强度σC和点荷载强度标准值IS(50)之间的最佳关系式,这种拟合关系在该工程施工过程中得到了很好地运用,经实践证明这种关系式是可行的。     

脆性岩石循环加卸载试验及应变损伤参数分析

为研究不同应力状态循环加卸载条件下脆性岩石的强度、变形和损伤力学特性,对马城铁矿辉绿岩开展了单轴压缩、三轴压缩以及单轴、三轴循环加卸载等不同应力路径岩石力学试验,得到了脆性岩石在单轴和三轴条件下的强度、变形特征以及循环加卸载应力-应变曲线变化规律。给出一种岩石循环加卸载过程中相对应变损伤参数,结合现有损伤力学理论,对脆性岩石破坏过程中的损伤演化规律进行了研究。试验结果表明：①UCS条件下,循环加卸载峰值强度比平均单轴压缩峰值强度低10%~20%;CTC条件下,峰值强度出现离散性。②循环加卸载过程中弹性常量变化趋势跟岩石内部微裂隙的闭合、张开、扩展等断裂损伤机制密切相关。③岩石内部的损伤积累程度随循环次数的增加而不断增大,绝对应变损伤参数几乎不受围压作用的影响,而相对应变损伤参数受到围压的约束作用。     

Use of rock mechanical properties to predict the Bond crushing index

The crushing energy in mineral processing industry is usually determined by empirical Bond’s index, regardless of the mechanical properties of a rock. Although several attempts have been made to obtain the comminution energy based on theoretical approaches, it would be appropriate to examine this relation based on physical concept. In this study, with the purpose of correlating the strain energy of a rock to the corresponding energy estimated by Bond’s index, spherical and cubic shape specimens have been simulated during crushing process between two rigid jaws. The specimens are modeled as elasto-plastic medium considering Mohr–Coulomb failure criterion. To verify the obtained results, finite difference method is used to model the fracture behavior in four volcanic rocks. All possible stages that may occur in the processing zone of crushing cubic and spherical rocks are examined and the combination of crushing stages with the lowest and highest strain energies is calculated based on simulation using FLAC3D code. The obtained strain energies are in good agreement with those of Bond’s energy. During the size reduction process of hard volcanic rocks, although shear and tensile fracture occur simultaneously, the shear mode of fracture consumes a larger portion of the crushing energy.     

前岭煤矿岩浆侵蚀区域瓦斯赋存规律研究

前岭煤矿地质构造复杂,岩浆侵蚀严重,已发生多次煤与瓦斯突出。为有效指导该特殊地质条件下的瓦斯治理,基于矿井地质构造和岩浆岩侵蚀情况,采用实验室测试及现场调查试验研究途径,选择具有代表性的测点,研究复杂地质条件下岩浆岩侵蚀区煤层瓦斯赋存规律。研究结果表明:受上覆岩浆岩热解和变质叠加作用,煤层变质程度增大,区域瓦斯突出判定指标增加;岩浆的高温热解作用,引起了煤层的二次生烃,上覆岩浆岩岩床和向斜轴部低透气性围岩共同对瓦斯的集聚起到了良好的圈闭作用,从而造成向斜轴部瓦斯压力和瓦斯涌出量增加,煤层瓦斯突出危险性增大。     

石油工程岩石强度与变形尺度效应研究现状综述与展望

岩石强度与变形存在显著的尺度效应,致使实验室尺度的岩样强度与变形测试结果不能直接应用于工程范围的大尺度岩体或微纳米级尺度的岩屑(矿物)。实现岩石强度与变形的跨尺度表征,即基于常规岩心测试手段,结合跨尺度表征方法来预测其他尺度的岩石力学参数和变形规律对于油气高效、经济、安全开采具有重要意义。本文在充分调研了国内外关于岩石强度与变形尺度效应研究的基础上,介绍了当前研究岩石强度与变形尺度效应的主要理论、主要认识和影响因素,并对石油工程领域岩石强度与变形尺度效应的研究方向进行了展望。     

Genesis and evolution of discontinuities in geomaterials: Theory and a laboratory experiment

The authors designed and manufactured a test stand to study origination and evolution of discontinuities in rocks. Based on the laboratory experimental data obtained for artificial geomaterials and the new-developed geomechanical model, the state equation for shear deformation of a discontinuity is synthesized.     

直剪条件下含裂隙岩石变形特征研究

为研究直剪条件下含裂隙岩石破坏过程中的变形特征,使用PFC^2D对含裂隙岩石进行直剪试验,分析试验中岩石的破坏位移、破坏功、抗剪强度之间的关系,并从细观角度分析试验过程中试样内部的位移情况。结果表明：裂隙使得岩石在破坏过程中产生了更大的变形;破坏功与破坏位移具有正相关关系;含单裂隙岩石两侧的位移方向和大小各不相同,越靠近裂隙中部,裂隙两侧的位移差越大,挤压情况越严重;含交叉裂隙岩石分为多个不同的区域,各区域内的位移大小、方向不相同,存在裂隙两侧张拉和挤压情况,在直剪条件下,内部各区域发生张拉破坏和挤压破坏。     

高温冷却后花岗岩损伤演化规律研究

为了研究高温冷却后花岗岩损伤规律,通过对不同温度作用冷却后的花岗岩进行了单轴压缩试验,研究了花岗岩的力学特性,得到以下主要结论:(1)高温冷却后岩石的应力-应变曲线表现为脆性断裂特点,分为压密阶段、线弹性阶段、弱化阶段和破坏阶段4个阶段。(2)温度对岩石的力学性质影响存在2个温度阈值:在室温到第1温度阈值范围内,岩石的力学性质随温度升高而劣化;第1温度阈值范围到第2温度阈值范围内,岩石的力学性质随温度升高而逐步强化;超出第2温度阈值范围后再升温,岩石的力学性质呈劣化特征。(3)基于Weibull分布提出了损伤演化规律并推导了相应的本构方程,理论模型能部分反映岩石的力学特性。     

完整岩石试件和含有裂隙岩石试件在单轴压缩下破坏过程的数值模拟研究

应用RFPA岩石失稳和破坏失稳程序对完整岩石试件以及含有单一裂隙和交叉裂隙的岩石试件在单轴压缩下的破坏过程进行数值模拟研究。结果揭示了完整岩石试件和含有不同裂隙岩石试件破裂过程的发展规律,即岩石试件破坏一般都分为3个阶段:压密阶段、微裂纹萌生阶段和扩展以及断裂破坏阶段。不同的是随着加载的进行,完整岩石试件的破坏过程首先出现一个应力集中区,随后在中间、径向、侧向均出现裂纹,并且这些裂纹迅速扩展衍生许多新的次生裂纹,最终贯穿整个岩石试件。而含有裂隙的岩石试件的破坏过程是首先在裂隙的2端出现应力集中区,随后在裂隙的尖端产生裂纹并沿垂直裂隙方向发展并贯通整个岩石试件。     

岩石裂隙面粗糙度参数关系分析

粗糙度是解释岩石裂隙力学及渗流特性的重要参数.采用自制模具,在轴向中部劈裂岩样,形成垂直于岩样轴向的新鲜裂隙.通过测取7组47个圆柱形岩样裂隙面188条轮廓曲线,分析了粗糙度系数JRC、粗糙轮廓指数Rp、粗糙角i、分维D和截距A等参数的相互关系.结果表明:JRC与岩样组成矿物颗粒大小关系密切,粒径越大,JRC越大.JR...     

Localization of deformation and prognostibility of rock failure

The general regular patterns in localization of deformation at pre-failure stage in rocks under compression are found and analyzed (sylvinite, marble sandstone). Applicability of speckle-photography methods to problems on rock deformation and failure is proved. The authors define the self-sustained behavior of the localized plastic deformation in rocks under compression, due to effect of various plastic micromechanisms. The autowaves in rock specimens under compression propagate at a rate of ～10^?5–10^?4 m/s (0.3–3 km/yr), which is close to slow motions induced in the earth crust by an earthquake or a rockburst. The ratio of the experimental and calculated failure times is correlated with the coordinates of the failure points in the test rock specimens.     

Simplified method for determining the extent to which strain rate affects the strength and energy capacity of rock fracture

Conclusions The described method of determining the extent to which strain rate affects the energy capacity of rock fracture offers a number of advantages over the traditional method: Firstly, it enables us to reduce the number of specimens tested by at least a factor of two; secondly, it increases the validity of the conclusions, since two forms of activity (static and dynamic) are applied to the same specimen; and, thirdly, it makes it possible to evaluate the effect of strain rate on the energy capacity of fracture for rocks where twin specimens have a high scatter of mechanical characteristics. Mining Institute, Leningrad. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 29–35, July–August, 1990.     

Strength predictions for jointed rocks in confined and unconfined states

Most of the rational approaches to the design of structures on or in a rock mass are based on the strength response of the rock mass. Realizing this important aspect, the present investigation was undertaken to understand the strength response of jointed rocks. The objective was achieved by simulating joints in intact isotropic rock cores in the laboratory.Three materials, namely, plaster of Paris, Jamrani sandstone and Agra sandstone were selected. The intact specimens of these materials provided a wide range of compressive strength (σ_ci = 11.3−110MN/m²). A special technique was devised to develop joints varying in number and inclination. In all, about 250 uniaxial compressive strength (UCS) tests and 1300 triaxial tests on jointed and intact specimens of these materials were conducted. Based on this extensive experimentation, a joint factor J_f, has been evolved to account for the number of joints per metre length, inclination of the sliding joint and the shear strength along this joint. This factor is found to be uniquely related to the ratio of compressive strength of jointed rock to that of the intact rock irrespective of the type of rock. A strength criterion for jointed rocks is proposed and the parameters defining this criterion can be evolved simply by knowing the joint factor, compressive strength of intact rock and triaxial strength of intact specimens at two convenient confining pressures. The empirical relations developed have been verified with similar data for other jointed rocks and model materials.     

Three dimensional stress determination by hydraulic fracturing for underground excavation design

The authors have developed a hydraulic fracturing system for three dimensional stress determination. The calculation procedure introduces new interpretations based on information obtained through laboratory hydraulic fracturing of intact rocks. Hydraulic fracturing data incorporated in the system must include at least both the fluid pressure at steady flow in a longitudinal fracture artificially produced around the borehole and the shut-in pressure in a transverse fracture which is apt to develop along a natural joint. Stress states in impermeable rock can then be evaluated by the system without assuming the direction of principal stresses.In this paper, the principle of the new method for three dimensional stress determination and an outline of the measuring system are described first, and then the results are reported of in situ measurements at several sites where the new system was applied.     

Changes in the number of elastic pulses during uniaxial compression of ore and rock samples

Conclusions In laboratory investigations we observe a phenomenon in which the ratio of the number of periods of elastic vibrations at the point of measurement of the mechanical stress to their maximum number equal to the total number of vibration periods from the start of load application to complete fracture of the specimen is directly proportional to the mechanical stress; the proportionality coefficient has a sharp change at the elastic limit. The steepness of the front and the bend in the graph of σ vs N/N_max are different for rocks of different classes: Substantially elastic, strong, and brittle rocks have steep fronts and a bend reflecting the accumulation of marked potential energy which is converted into kinetic energy of flying fragments; plastic and jointed rocks have less steepness and a rather smooth bend, reflecting the dissipation of elastic energy before fracture. These indices may serve as signs of bump-prone rocks. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 110–112, July–August, 1978.     

损伤和破坏岩石的强度研究

根据单轴卸载试验,获得岩样相应的应力应变曲线和轴向应变-径向应变曲线,并得到不同程度的损伤岩样。与完整的峰前曲线相比较,推断不同损伤程度岩样的卸载点所处于的应力应变曲线的阶段。将损伤岩样和破坏形成的岩块浇注在混凝土中,通过剪切试验获得岩石的抗剪强度。剪切试验结果显示,在裂纹稳定发展阶段卸载,岩样的抗剪强度下降很小,可能强度的变化掩藏在个体差异中;在裂纹不稳定发展阶段卸载,岩样的抗剪强度明显下降,特别是卸载点靠近强度峰值时;单轴压缩破坏形成的岩块仍具有相当可观的材料强度。     

岩石撞击引发矿井瓦斯爆炸可能性的实验探索

针对煤矿瓦斯灾害诱发背景及原因,结合前期固体撞击实验成果,利用热红外成像技术进行了沉积岩类岩石的撞击实验,发现撞击瞬间,岩石撞击中心部位或飞溅破碎体温度达到最大值,撞击升温可达218 ℃,且温度保持在100 ℃以上的时间超过1 min;干燥岩石升温高于潮湿岩石,不规则岩石升温高于规则岩石,石灰岩升温高于砂岩.实验结果表明,岩石的撞击升温可能形成火源而引发瓦斯爆炸.在此基础上,针对岩石撞击升温的三大机理,即岩石破裂摩擦、岩石热弹效应及岩石物理机理,讨论并提出了防止因岩石撞击升温形成火源并引爆矿井瓦斯的某些措施与途径.     

两河口水电站初期导流洞固结灌浆试验施工工艺

两河口水电站初期导流洞发育有较多断层及绢云母板岩夹层,尤其是f25、f3、f8系列、f4、f28等断层由多条次级错动带组成,破碎带宽度大,岩体完整性差,围岩极不稳定。为了确保导流洞运行安全,需对导流洞洞内Ⅳ类、Ⅴ类围岩区域进行固结灌浆施工并根据要求进行灌浆试验。主要介绍了固结灌浆试验施工工艺。