共查询到19条相似文献，搜索用时 218 毫秒
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用超声脉冲法研究了不同性质岩块构成的样品破裂前的波速变化。样品为长方形大理岩板,中心镶嵌大理岩、辉长岩、花岗岩,砂岩圆块。实验表明,样品破裂时裂纹穿过低强度镶嵌岩块而绕过高强度镶嵌岩块。在第一种场合样品破裂前,镶嵌岩块內波速变化显著,在第二种场合样品破裂前镶嵌岩块內波速变化不大。穿过两种岩石界面的波速测量表明,波速下降的起始点提前到样品破坏应力的60%左右。样品破裂前波速总的变化趋势是下降,但不是单调下降而呈现起伏。这说明介质不均匀性会对岩石破裂前的波速变化规律产生不可忽视的影响。 相似文献
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砂岩和页岩的弹性波性质是通过地震资料推断储层物性和流体分布的基础.岩石波速测量常用超声波(105～106 Hz)脉冲法,低频岩石物理实验技术的发展为研究弹性波在岩石中的衰减和频散奠定了基础.本文系统总结了前人在高频和低频下测量砂岩和页岩弹性波性质的方法和实验结果,并结合矿物弹性性质和岩石物理模型,分析了压力、温度、矿物组成、孔隙结构、流体、频率等因素对岩石波速和衰减的影响.由于孔隙和微裂隙随压力增加而逐渐关闭,干燥砂岩和页岩的P波和S波速度在低压下随压力非线性增加,高于临界压力呈线性增加.干燥岩石样品的波速随温度增加而缓慢线性降低,频散效应可以忽略.而含流体砂岩和页岩的衰减和频散受温度、压力、流体饱和度、流体黏度、孔隙结构和频率等多种因素的影响,含流体砂岩和页岩的泊松比和逆品质因子Q-1显著高于干燥样品.低压下砂岩的波速与孔隙度负相关,而影响页岩波速的因素更为复杂,页岩的波速、衰减和频散的各向异性都高于砂岩.将跨频段岩石物理实验与数字岩石物理技术相结合,可为勘探地球物理的方法创新和资料解释提供可靠依据. 相似文献
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山西裂谷带地壳岩石波速的研究 总被引：2，自引：2，他引：2
通过实验建立了岩石成分与波速的关系,波速和岩石的各向异性,矿物相变在波速曲线中的反映以及实验温度和压力对波速的影响,尤其得到了高温下的新资料.用实验数据结合地球物理、地质资料建立了山西裂谷带与相邻太行山隆起区地壳各层圈的物质组成,对比说明,两构造单元下地壳的岩石组成是不同的.最后分析了盆地下地壳中部的组成、水和环境条件,认为低速带是由岩石部分熔融造成的. 相似文献
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本文用超声波地震模型实验方法,对引起有机玻璃样品P波速变化的尺度因素和环境因素进行了实验研究。结果表明,当样品厚度小于一个波长时,样品尺度和环境介质对样品P波速都有明显影响。当样品厚度由使用换能器的1/16个波长增加到3个波长时,P波速变化约16％。在低于样品P波速的液体中测量,样品的P波速增加,增加的幅度与液体的波速有关。文中还对纵波和拉伸波的转换现象作了初步探讨。 相似文献
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本文用单轴,三轴不等压和围压下混凝土样品的地震波变化特征实验,对含孔隙度混凝土样品破裂过程中的Vp、Vs、Vp/Vs、Ap、As、Ap/As进行了综合实验研究。结果表明:1.含孔隙度混凝土样品对地震波振幅的影响较显著。2.样品破裂过程中Vp、Vs、Vp/Vs、Ap、As、Ap/As有一个明显的变化过程。3.在样品临破裂前地震波振幅变化的各向异性非常明显。4.地震波振幅的衰减与样品强度、性质、结构和受力状态有关,即样品强度高,受力状态为(σ>0,σ2=σ3=0)振幅衰减慢,反之振幅则衰减快。5.性质相同的样品,波速随密度的增加而增大,由于密度和孔隙度有关,故波速也受孔隙度的影响。6.含孔隙度混凝土样品与小岩石样品有着某种相似性,因此,混凝土样品的实验结果同样对地震波波速异常有启示。 相似文献
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本文研究了在不同的应力途径下岩石破坏的条件和破裂的前兆.选定了三种应力途径进行研究:在一定应力状态下增加最大主应力σ1, 保持σ2, σ3不变, 使岩石破坏（A 型）;减小最小主应力使岩石破坏（B 型）;增加最小主应力岩石不破坏（C 型）.通过实验得到了济南辉长岩和昌平花岗岩 A 型途径和 B 型途径破裂强度的比较.对三种途径岩石的体应变、声发射和波速Vp, 进行了对比研究.A 型途径的破裂前兆表现与许多作者的结果相符合.B 型途径岩石断裂前处于"过密"状态, 与此相联系的声发射增加和波速Vp下降出现得很晚.C 型途径岩石处于超膨胀状态, 出现了声发射增加和波速Vp下降而岩石并未破坏的现象. 相似文献
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高压下岩石弹性波速度几种测量方法的比较实验研究 总被引：2，自引：0，他引：2
在高压高温条件下测量岩石弹性波速是获得岩石在地球内部的各种力学和热力学数据的主要途径, 也是研究地球内部物质结构和组成的重要手段. 近年来, 用固体作为传压介质的高压高温岩石弹性波速测量方法发展较快, 然而目前各个实验室在高温高压条件下所测量出的岩石弹性波数据, 还没有进行过严格的对比. 为了对比各实验室的实验测量结果, 对3种测量方法进行了比较实验研究, 并与流体传压介质透射法的测量结果进行了对比. 实验表明, 3种测量方法在其适用压力范围内的测量结果都能相互对比. 其中Kern所使用的六面体样品脉冲透射法适用于压力温度较低的地壳类岩石样品的测量. 柱状样品脉冲反射-透射法在适用压力范围、加热温度和测量精度方面均有一定优势. 柱状样品脉冲透射法虽然在压力较低时测量精度较低, 但样品长度大, 组装简便, 适用于样品量大, 要求压力较高的实验. 因此在实际应用中, 后两种方法可进行相互校正和相互补充. 相似文献
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本文对济南辉长岩经历不同应力途径后岩石晶粒内的微破裂特征的观测进行了研究.实验中岩石样品首先承受较高的围压(使应力差达到岩石强度的80%),然后分别按 A,B,C 三种途径进行实验.三种途径已在另一文中作了叙述(见地震学报第2卷第3期237页).实验结束后,将岩石样品切开,制成标准薄片及光片.通过显微镜的观测发现,三种应力途径所引起的微破裂性质明显不同.在 B 型实验中,长石晶粒内的微裂纹表现得短小,其长度多数不超过长石晶粒短轴的长度.整个岩石样品内微裂纹的分布密集于较小的范围内.在 C型实验中,倾斜裂纹数量增多,长石晶粒中的裂纹比 A 和 B 实验更长和更多,出现一种星状的微裂纹.观测到的辉长岩的微观现象可能说明与岩石标本过密、超膨胀现象有关. 相似文献
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高温高压实验弹性波速研究及其地球动力学意义 总被引：6，自引：2，他引：6
本文在收集，整理国内外有关高温高压实验岩石，矿物弹性波速研究资料的基础上，对高温高压实验弹性波速研究的目的，内容进行了概述，并对国内外这一领域研究的历史，现状及有关实验技术方法进行了综述，其中重点介绍了我国在高温高压岩石波速研究方面的进展及所取得的成就，并对高温高压弹性波速研究的地球动力学意义进行了讨论。 相似文献
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A. Schubnel O. Nishizawa K. Masuda X. J. Lei Z. Xue Y. Guégen 《Pure and Applied Geophysics》2003,160(5-6):869-887
— A set of experiments on four samples of Oshima Granite at 15, 40 and 60 MPa confining pressure have been performed in order to investigate the damage behavior of granite submitted to deviatoric stress. In addition an experiment on one sample of Toki Granite at 40 MPa confining pressure was performed, in order to compare and elucidate the structural effects. Using acoustic emission data, strain measurements and elastic wave velocities allow to define consistently a damage domain in the stress space. In this domain, microcracking develops. The microcracking process is, in a first stage, homogeneous and, close to failure, localized. Elastic wave velocities decrease in the damage domain and elastic anisotropy develops. Using Kachanov's model (1993), elastic wave velocities have been inverted to derive the full second-order crack density tensor and characterize the fluid saturation state from the fourth-order crack density tensor. Crack density is strongly anisotropic and the total crack density close to failure slightly above one. The results indicate that the rock is saturated in agreement with the experimental conditions. The model is thus shown to be very appropriate to infer from elastic wave velocities a complete quantitative characterization of the damaged rock. 相似文献
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利用较大岩石样品,实验研究了加载时同时向样品内注水过程中穿过样品超声波波速和尾波Ｑｃ值的变化特征。结果表明,在压力作用下,岩石破坏前通过岩石的尾波Ｑｃ值下降,如果有压力水进入,则岩石的尾波值Ｑｃ会大幅下降。因此,我们可以认为,地壳岩石破坏发生地震前的尾波下降的物理机制是岩石在压力产生扩容裂隙及流体进入裂隙双重作用的结果。 相似文献
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Petrophysical measurements were carried out on dry specimens of mica-gneiss, amphibolite and serpentinite from KTB core samples and samples of surface outcrops in order to determine the effect that a deviatoric stress field, as observed at the KTB area, may have on the in-situ rock properties. Simulating the variation of the actual principal stresses and temperature with depth, seismic wave velocities, densities, linear and volumetric strain (porosity) have been measured, taking into account the overall spatial orientation of the foliation at the KTB area with respect to the principal stress axes. Comparison with respective data evaluated for lithostatic pressure conditions revealed that the stress-related (crack-related) effect on wave velocities respectively on velocity anisotropy is in the range 1–3%, due to microcracks which are selectively closed or kept open by the deviatoric stress. The effect of the deviatoric stress is particularly documented by shear wave splitting due to microfractures that are oriented normal to the minimum principal stress axis. 相似文献
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Hydraulic fracturing reservoir reconstruction technology is crucial in the development of shale gas exploitation techniques.Large quantities of high-pressure fluids injected into shale reservoirs significantly alter compressional(P)and shear(S)wave velocities,rock mechanical parameters,and anisotropic characteristics.In this study,differentiated hydraulic fracturing petrophysical experiments were carried out on Longmaxi Formation shale under pseudo-triaxial stress loading conditions.The effects of stress loading methods,and water-rock physical and chemical reactions on P-and S-wave velocities and rock mechanical parameters were compared.The experimental results showed that isotropic stress loading may increase the P-and Swave velocities and Young’s modulus of dry shale kldnsample.Furthermore,it may lead to a weakening of the corresponding anisotropy.In contrast,differential stress loading was able to improve the anisotropy of Young’s modulus and accelerate the decrease in the compressive strength of shale in the vertical bedding direction.The water-rock physical and chemical reactions prompted by hydraulic fracturing was found to"soften"shale samples and reduce Young’s modulus.The influence of this"soften"effect on the compressional and shear wave velocities of shale was negligible,whilst there was a significant decrease in the anisotropy characteristics of Thomsen parameters,Young’s modulus,and Poisson’s ratio.The negative linear relationship between the Poisson’s ratios of the shale samples was also observed to lose sensitivity to stress loading,as a result of the"soften"effect of fracturing fluid on shale.The results of this study provide a reliable reference point and data support for future research on the mechanical properties of Longmaxi shale rocks. 相似文献
16.
H. Spetzler 《Pure and Applied Geophysics》1978,116(4-5):732-742
Fracture and frictional sliding are considered as phenomena involving brittle failure. Brittle failure is preceded by the formation of small (subcritical) cracks. In non-water-saturated rock, the distribution, shape and size of these suberitical cracks determine the change in the physical properties prior to failure. A model is proposed which suggests that the spatial and temporal distribution, shape and size of subcritical cracks within a stressed rock depend upon the rate of deformation and the volatile content.As a rock is stressed beyond about 50 percent of its ultimate failure stress, dilatancy is initiated. With increasing stress a broad zone of cracks develops within the dilatant region. The seismic velocities through this zone decrease markedly and the cracks grow more numerous., changing in size and shape. Before brittle failure of the rock occurs, the subcritical cracks interact, leading to a concentration of the zone. During the stage when the zone narrows, the seismic velocities in crease in the surrounding volume due to local rotation of stresses and consequent closure of some cracks. In most laboratory experiments the stage during which the velocity increases and the now intense deformation zone becomes narrow is very short and difficult to observe experimentally. At very low strain rates and with volatiles present, the crack growth and subsequent interaction lead to the narrowing of the intense deformation zone and therefore to an observable increase in velocity.The above is based upon an interpretation of a number of experiments. Using optical holography we have observed the development and subsequent intensification of a deformation zone. Ultrasonic velocity measurements showed a distinct anomaly (decrease followed by an increase) before failure. The anomaly was only detectable at our lowest experimental strain rates (3×10–8/sec). 相似文献
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2004年印尼8.7级强震前昌黎台的远场电性异常特征探讨 总被引：1，自引：0，他引：1
分析了在2004年12月26日印尼8.7级地震前河北昌黎台记录到的自然电位及电场异常, 结果显示昌黎台自电位、 电场正常时段观测到的半日、 半月潮汐波周期变化在震前1个多月发生畸变, 周期消失, 变化幅度相应减小, 震后快速恢复, 且潮汐波记录比震前正常时段更加清晰。 该台地电阻率的观测结果显示起始下降变化比较平缓, 震前一周左右, 变化加剧, 出现多次阶变。 究其原因, 在强震发生前断层的蠕滑作用导致孔隙压力变化, 产生一种可以在岩石中传播的应变波, 由于台站下方岩土层对小应变信号具有很好的放大作用, 所以记录到了这种小幅度的应变波, 也就是远场的静态应变效应。 随着地震临近, 应力作用加强, 远程应变波引起台站下方水位、 水化学性质以及岩石孔隙度、 渗透率等的改变, 导致电阻率、 电场大幅度的阶变, 这反映了远场应变波的动态效应。 当然就异常幅度而言, 应变波的效应还嫌弱一些, 因此昌黎台异常变化可能还叠加了震源区激发的电磁波。 相似文献
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利用新方法制作出含可控裂缝的双孔隙人工砂岩物理模型,具有与天然岩石更为接近的矿物成分、孔隙结构和胶结方式,其中裂缝密度、裂缝尺寸和裂缝张开度等裂缝参数可以控制以得到实验所需要的裂缝参数,岩样具有真实的孔隙和裂缝空间并可以在不同饱和流体状态下研究流体性质对于裂缝介质性质的影响.本次实验制作出一组具有不同裂缝密度的含裂缝人工岩样,对岩样利用SEM扫描电镜分析可以看到真实的孔隙结构和符合我们要求的裂缝参数,岩样被加工成八面棱柱以测量不同方向上弹性波传播的速度,用0.5 MHz的换能器使用透射法测量在饱和空气和饱和水条件下各个样品不同方向上的纵横波速度,并得出纵横波速度、横波分裂系数和纵横波各向异性强度受裂缝密度和饱和流体的影响.研究发现流体对于纵波速度和纵波各向异性强度的影响较强,而横波速度、横波分裂系数和横波各向异性强度受饱和流体的影响不大,但是对裂缝密度的变化更敏感. 相似文献