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岩石介质中多裂纹扩展相互作用及其贯通机制的数值模拟 总被引：14，自引：0，他引：14
运用岩石破裂过程分析RFPA^2D系统，通过对岩石试样中预置的一组右行右阶雁列式裂纹扩展过程的数值模拟，研究了非均匀岩石介中多裂纹扩展的相互作用模式及其贯通机制。数植模拟再现的受压混合型裂纹扩展过程中逐步演变的全场变形过程，以及与细观非均匀性有关的声发射和断续扩展模式的“岩桥”现象，清晰地揭示出多裂纹扩展的相互作用及其贯通机制。模拟结果说明，对于岩石这种地质介质而言，忽略其非均匀性影响，可能会掩盖岩石变形与破裂过程中的许多与非均匀性有关的特殊现象，包括声发射或微震模式、岩桥或雁行断裂等。 相似文献
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M. J. Selby 《地球表面变化过程与地形》1982,7(5):449-467
In identifying controls on rock slope form a distinction is made between: (1) rock slopes with joints which dip steeply out of a cliff and hence are subject to mass failure of the rock mass above a critical joint; and (2) rock slopes with inclinations which are either in equilibrium with the mass strength of their rocks, or have profiles which will develop towards strength equilibrium as cross joints open. In the first class of slope, stability results not just from the basic frictional resistance of the rock but also from the frictional roughness along the critical joint and from the normal stress acting across that joint. Stability may be reduced by weathering and loss of strength of the joint wall rock. As a result of normal stress variations with depth, induced by overburdens, high cliffs which are not undercut have a concave profile. The second group of slopes includes those with inclinations controlled at the scale of individual joint blocks, buttressed slopes and those on unjointed rock masses. Buttressed and unjointed rock masses develop towards a condition of mass strength equilibrium as cross joints open. Strength equilibrium slopes may be recognized by application of a rock mass strength classification proposed for geomorphic purposes. Eleven propositions are formulated which identify controls on rock slope development and some consequences of these controls. 相似文献
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L. N. Germanovich R. L. Salganik A. V. Dyskin K. K. Lee 《Pure and Applied Geophysics》1994,143(1-3):117-149
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基于线弹性断裂力学理论分析了垂直向地震作用对节理岩体地震动力破坏的影响。在仅考虑峰值时,最不利的单向地震动加速度方向是水平倾向坡外,双向则依据破裂机制是拉剪或压剪,加速度分别是水平倾向坡外与向下或向上的组合。地震动的幅值、作用方向及双向地震动的组合都可使岩体的破坏机制发生转化,并且是突变的、不可逆的。较低峰值的双向地震动产生的应力强度因子可能大于较高峰值的单向地震动所产生的应力强度应子。在岩体节理分布特征和静态应力场一定的初始条件下,第一个导致岩体中产生破裂的地震动加速度幅值及其方向的组合唯一地决定了岩体不可逆破坏发展的方向、机制及最终的破坏特征,其复杂性远大于静力作用时的情况。对岩体地震动力破坏问题的认识应充分考虑垂直向地震动的重要影响。 相似文献
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Testing the Validity of Simulated Strong Ground Motion from the Dynamic Rupture of a Finite Fault, by Using Empirical Equations 总被引：1，自引：0，他引：1
This paper is concerned with testing the validity of the ground motions estimated by combining a boundary integral equation method to simulate dynamic rupture along finite faults with a finite difference method to compute the subsequent wave propagation. The validation exercise is conducted by comparing the calculated ground motions at about 100 hypothetical stations surrounding the pure strike-slip and pure reverse faults with those estimated by recent ground motion estimation equations derived by regression analysis of observed strong-motion data. The validity of the ground motions with respect to their amplitude, frequency content and duration is examined. It is found that the numerical simulation method adopted leads to ground motions that are mainly compatible with the magnitude and distance dependence modelled by empirical equations but that the choice of a low stress drop leads to ground motions that are smaller than generally observed. In addition, the scatter in the simulated ground motions, for which a laterally homogeneous crust and standard rock site were used, is of the same order as the scatter in observed motions therefore, close to the fault, variations in source propagation likely contribute a significant proportion of the scatter in observed motions in comparison with travel-path and site effects. 相似文献
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受结构和赋存环境的制约,岩体力学性质及其力学参数具有显著的时间和空间变异性.岩体力学参数和岩体质量从不同的侧面反映了岩体力学性质,两者具有必然的关联性,故可用相对简单的岩体质量评价来选取岩体力学参数:按地质条件将岩体空间离散为若干连续微元体单元;采用Q、RMR和BQ等方法逐一对各单元开展岩体质量评价,并利用岩体质量与岩体力学参数间的关系(如Hoek-Brown经验准则)计算其力学参数;综合各单元的计算结果确定反映连续岩体空间内空间变异特征的力学参数.以某水电站地下洞室群为例,实现了工程区围岩力学参数的不连续取值. 相似文献
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爆破地震动效应的数值模拟分析 总被引：13，自引：0，他引：13
爆破设计中,场地条件复杂时经验公式的应用受到一定限制。本文采用波动有限元分析方法,研究复杂场地条件下工程爆破时场地的地震动效应,研究爆破地震动特征及衰减规律。根据某重点工程场地岩土参数的原位测试和试验结果,用自行研制的软件包进行场地爆破地震动效应的数值模拟分析,为工程爆破设计及施工前建筑物、仪器设备的加固提供了依据。施工试爆实测结果与本文数值模拟分析给出的结果一致,说明本文方法是可行的,对其它工程也有借鉴作用。 相似文献
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为了研究采用灌浆套筒连接装配式剪力墙结构的抗爆性能,应用显式动力分析软件LS-DYNA建立了现浇剪力墙和装配式剪力墙的有限元模型,对不同爆炸荷载下剪力墙的破坏形态和动态响应进行了模拟分析;扩充影响参数范围,进一步研究了墙体厚度和混凝土强度等级等因素对装配式剪力墙结构抗爆性能的影响。数值分析表明:对于装配式剪力墙,由于坐浆层处存在新旧混凝土的薄弱粘结面,爆炸作用下首先发生破坏,爆炸应力波聚集于坐浆层周围的墙体内部,导致局部发生脆性破坏;现浇剪力墙刚度分布比较均匀,爆炸作用下背爆面的混凝土首先被拉裂,最终发生弯曲破坏;增加墙体厚度、提高混凝土强度等级和改变炸药爆炸位置均可改善装配式剪力墙的抗爆性能。 相似文献
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Junichi Takekawa Hitoshi Mikada Tada-nori Goto Yoshinori Sanada Yuzuru Ashida 《Pure and Applied Geophysics》2013,170(4):561-570
The failure of brittle materials, for example glasses and rock masses, is commonly observed to be discontinuous. It is, however, difficult to simulate these phenomena by use of conventional numerical simulation methods, for example the finite difference method or the finite element method, because of the presence of computational grids or elements artificially introduced before the simulation. It is, therefore, important for research on such discontinuous failures in science and engineering to analyze the phenomena seamlessly. This study deals with the coupled simulation of elastic wave propagation and failure phenomena by use of a moving particle semi-implicit (MPS) method. It is simple to model the objects of analysis because no grid or lattice structure is necessary. In addition, lack of a grid or lattice structure makes it simple to simulate large deformations and failure phenomena at the same time. We first compare analytical and MPS solutions by use of Lamb’s problem with different offset distances, material properties, and source frequencies. Our results show that analytical and numerical seismograms are in good agreement with each other for 20 particles in a minimum wavelength. Finally, we focus our attention on the Hopkinson effect as an example of failure induced by elastic wave propagation. In the application of the MPS, the algorithm is basically the same as in the previous calculation except for the introduction of a failure criterion. The failure criterion applied in this study is that particle connectivity must be disconnected when the distance between the particles exceeds a failure threshold. We applied the developed algorithm to a suspended specimen that was modeled as a long bar consisting of thousands of particles. A compressional wave in the bar is generated by an abrupt pressure change on one edge. The compressional wave propagates along the interior of the specimen and is visualized clearly. At the other end of the bar, the spalling of the bar is reproduced numerically, and a broken piece of the bar is formed and falls away from the main body of the bar. Consequently, these results show that the MPS method effectively reproduces wave propagation and failure phenomena at the same time. 相似文献
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本文在考虑动态力源扰动的情况下,对岩石损伤对地震波辐射的影响及其震源表示进行了理论推导,证明了当有动态力源存在时,Ben-Zion和Ampuero于2009年给出的结果只是岩石非弹性响应对震源及相应地震波场的贡献,而非其全部.在此基础上,应用相关结果对岩石损伤破坏对地下核爆炸震源成分的影响进行了分析,给出了地下核爆炸情况下补偿线性偶极子源和构造应力释放与岩石损伤破坏之间的关系.结果表明,地下核爆炸补偿线性偶极子源主要来自于地表反射拉伸波和空腔回弹冲击波等造成的爆心上方锥形区域中的岩石破坏,而构造应力释放则主要来自于整个岩石破坏区内的构造应力松弛. 相似文献
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A numerical method of viscoelastic finite element coupled with spring-block model is developed to study temporal processes from the slow tectonic motion of large-scale crust to the rapid failure of small-scale faults. Our modeling demonstrates that the motion of crustal blocks is driven by forces from tectonic plate boundaries, and the deformation is distributed on faults for the stress accumulating. The coupling model generates earthquake sequences that display a magnitude-frequency scaling consistent with Gutenberg-Richter law. The frictional heterogeneities affect earthquakes occurrence and stresses distribution of crustal blocks. Rupture of earthquakes starts at the nucleation node, and propagates bilaterally along faults with the stress triggering, release and redistribution. The failure of faults releases part of crustal stresses, the stress state of crustal blocks near fault is affected by the rupture of local segments on the fault, and the stress state of crustal blocks far away from the fault is controlled by the seismic activity of the whole fault. 相似文献
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A numerical method of viscoelastic finite element coupled with spring-block model is developed to study temporal processes from the slow tectonic motion of large-scale crust to the rapid failure of small-scale faults. Our modeling demonstrates that the motion of crustal blocks is driven by forces from tectonic plate boundaries, and the deformation is distributed on faults for the stress accumulating. The coupling model generates earthquake sequences that display a magnitude-frequency scaling consistent with Gutenberg-Richter law. The frictional heterogeneities affeci earthquakes occurrence and stresses distribution of crustal blocks. Rupture of earthquakes starts at the nucleation node, and propagates bilaterally along faults with the stress triggering, release and redistribution. The failure of faults releases part of crustal stresses, the stress state of crustal blocks near fault is affected by the rupture of local segments on the fault, and the stress state of crustal blocks far away from the fault is controlled by the seismic activity of the whole fault. 相似文献
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为研究地震产生的应力波在断续节理岩体中的传播规律和应力分布趋势,首先,采用数值模拟方法分析应力波通过贯通节理的传播规律,并与已有理论研究结果进行对比,验证数值分析的准确性和适用性;然后,对应力波在断续节理岩体中的传播进行数值模拟,分析透射系数在水平方向的分布趋势以及不同节理连续性对波传播的影响,并结合波的衍射原理,给出定性的理论解释。结果表明:应力波通过断续节理时,节理的透射作用会使应力波振幅减小,引起波的衰减,岩桥的衍射作用则会使波阵面由平面变为曲面,波的传播方向发生改变,从而导致应力波振幅在水平方向的分布发生变化;应力波通过断续节理的透射系数与岩桥尺寸Lr和衍射角μ相关,当衍射角比较小时,透射系数主要受岩桥尺寸Lr的影响,当衍射角较大时,岩桥尺寸Lr和衍射角μ共同影响应力波在岩体中的传播。 相似文献
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In this paper,an explicit finite element method to analyze the dynamic responses of three-medium coupled systems with any terrain is developed on the basis of the numerical simulation of the continuous conditions on the bounda-ries among fluid saturated porous medium,elastic single-phase medium and ideal fluid medium.This method is a very effective one with the characteristic of high calculating speed and small memory needed because the formulae for this explicit finite element method have the characteristic of decoupling,and which does not need to solve sys-tem of linear equations.The method is applied to analyze the dynamic response of a reservoir with considering the dynamic interactions among water,dam,sediment and basement rock.The vertical displacement at the top point of the dam is calculated and some conclusions are given. 相似文献
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As the economy of China develops, an increasing number of key traffic projects have been undertaken in the west of China, where there are high, steep rock slopes. The collapse of dangerous rock masses, especially following a strong earthquake, is one of common geological disasters known in rock slope engineering. Therefore, it is important to study the collapse mechanism of dangerous rock masses induced by an earthquake and the analysis approach of its stability. This study provides a simple and convenient method to determine the collapse mechanisms of two types of dangerous rock masses (i.e. cantilever and upright) associated with the definition and calculation of the safety factor, which is based on the flexure theory of a constant-section beam by combining with the maximum tensile-stress criterion to depict the process of crack propagation caused by seismic waves. The calculation results show that there are critical crack depths in each form of the dangerous rock masses. Once the accumulated depth of the crack growth during an earthquake exceeds the critical depth, the collapse will occur. It is also demonstrated that the crack extension amount of each step is not a constant value, and is closely associated with the current accumulated crack depth. The greater the cumulative crack depth, the more easily the crack propagates. Finally, the validity and applicability of the proposed method are verified through two actual engineering examples. 相似文献
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Eva Caspari Mikhail Novikov Vadim Lisitsa Nicolás D. Barbosa Beatriz Quintal J. Germán Rubino Klaus Holliger 《Geophysical Prospecting》2019,67(4):935-955
Seismic attenuation mechanisms receive increasing attention for the characterization of fractured formations because of their inherent sensitivity to the hydraulic and elastic properties of the probed media. Attenuation has been successfully inferred from seismic data in the past, but linking these estimates to intrinsic rock physical properties remains challenging. A reason for these difficulties in fluid-saturated fractured porous media is that several mechanisms can cause attenuation and may interfere with each other. These mechanisms notably comprise pressure diffusion phenomena and dynamic effects, such as scattering, as well as Biot's so-called intrinsic attenuation mechanism. Understanding the interplay between these mechanisms is therefore an essential step for estimating fracture properties from seismic measurements. In order to do this, we perform a comparative study involving wave propagation modelling in a transmission set-up based on Biot's low-frequency dynamic equations and numerical upscaling based on Biot's consolidation equations. The former captures all aforementioned attenuation mechanisms and their interference, whereas the latter only accounts for pressure diffusion phenomena. A comparison of the results from both methods therefore allows to distinguish between dynamic and pressure diffusion phenomena and to shed light on their interference. To this end, we consider a range of canonical models with randomly distributed vertical and/or horizontal fractures. We observe that scattering attenuation strongly interferes with pressure diffusion phenomena, since the latter affect the elastic contrasts between fractures and their embedding background. Our results also demonstrate that it is essential to account for amplitude reductions due to transmission losses to allow for an adequate estimation of the intrinsic attenuation of fractured media. The effects of Biot's intrinsic mechanism are rather small for the models considered in this study. 相似文献
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Evidence of fluid interaction with normal faults comes from their varied role as flow barriers or conduits in hydrocarbon basins and as hosting structures for hydrothermal mineralisation, and from fault-rock assemblages in exhumed footwalls of steep active normal faults and metamorphic core complexes. These last suggest involvement of predominantly aqueous fluids over a broad depth range, with implications for fault shear resistance and the mechanics of normal fault reactivation. A general downwards progression in fault rock assemblages (high-level breccia-gouge (often clay-rich) → cataclasites → phyllonites → mylonite → mylonitic gneiss with the onset of greenschist phyllonites occurring near the base of the seismogenic crust) is inferred for normal fault zones developed in quartzo-feldspathic continental crust. Fluid inclusion studies in hydrothermal veining from some footwall assemblages suggest a transition from hydrostatic to suprahydrostatic fluid pressures over the depth range 3–5 km, with some evidence for near-lithostatic to hydrostatic pressure cycling towards the base of the seismogenic zone in the phyllonitic assemblages. Development of fault-fracture meshes through mixed-mode brittle failure in rock-masses with strong competence layering is promoted by low effective stress in the absence of thoroughgoing cohesionless faults that are favourably oriented for reactivation. Meshes may develop around normal faults in the near-surface under hydrostatic fluid pressures to depths determined by rock tensile strength, and at greater depths in overpressured portions of normal fault zones and at stress heterogeneities, especially dilational jogs. Overpressures localised within developing normal fault zones also determine the extent to which they may reutilise existing discontinuities (for example, low-angle thrust faults). Brittle failure mode plots demonstrate that reactivation of existing low-angle faults under vertical σ1 trajectories is only likely if fluid overpressures are localised within the fault zone and the surrounding rock retains significant tensile strength. Migrating pore fluids interact both statically and dynamically with normal faults. Static effects include consideration of the relative permeability of the faults with respect to the country rock, and juxtaposition effects which determine whether a fault is transmissive to flow or acts as an impermeable barrier. Strong directional permeability is expected in the subhorizontal σ2 direction parallel to intersections between minor faults, extension fractures, and stylolites. Three dynamic mechanisms tied to the seismic stress cycle may contribute to fluid redistribution: (i) cycling of mean stress coupled to shear stress, sometimes leading to postfailure expulsion of fluid from vertical fractures; (ii) suction pump action at dilational fault jogs; and, (iii) fault-valve action when a normal fault transects a seal capping either uniformly overpressured crust or overpressures localised to the immediate vicinity of the fault zone at depth. The combination of σ2 directional permeability with fluid redistribution from mean stress cycling may lead to hydraulic communication along strike, contributing to the protracted earthquake sequences that characterise normal fault systems. 相似文献