共查询到20条相似文献，搜索用时 46 毫秒
1.
节理岩体几何结构非常复杂,研究其渗流特性对于指导含水岩层稳定性分析具有重要价值。应用离散裂隙网络模型DFN方法,基于VC++6.0软件平台,建立了平面渗流分析方法,分析了节理岩体不同几何分布情况下的渗透率张量特征,通过定义渗流定向性系数对岩体渗流的定向性特征进行了定量分析。结果表明：单组节理岩体渗流具有明显的各向异性特征,渗流定向性随着节理角度变化显著;节理随着节理贯通性增加,节理渗透率呈现对数增加趋势;两组节理情况下,各向异性特征随着节理组间夹角变化;两组节理岩体渗流特征研究中,正交分布下,岩体仍存在各向异性,但渗流定向性系数较低;当节理倾角服从正态分布时,随着节理倾角标准差增大,渗透率增加;两组节理夹角不同时,节理渗透主方向倾角随着夹角增大而相应增大,基本沿两组节理夹角方向的角平分线方向。 相似文献
2.
为了研究煤岩水力压裂的起裂压力和水力压裂裂缝扩展规律,采用型煤试样,利用自主研发的水力压裂实验系统,参照现场压裂施工制定了“施加三向应力-顶部注水”的煤岩水力压裂物理模拟实验方案并开展了水力压裂实验,分析了不同条件下泵注压力和水力压裂裂缝。实验结果表明:压裂液泵注排量越大,起裂压力越大。三向应力满足最大水平主应力σH > 垂向应力σv > 最小水平主应力σh,水力压裂裂缝沿着垂直于σh的方向扩展。σv和σh一定,随着σH的增大,煤岩起裂压力先增大后减小,水力压裂裂缝扩展路径越平直。当σH远大于σv和σh时,水力压裂裂缝扩展路径越复杂,分叉缝角度越大。研究结果可为煤岩水力压裂理论的完善提供一定的参考和借鉴。 相似文献
3.
4.
节理对卸荷条件下岩体的力学性质有重要影响。通过含2条不同间距预制断续节理岩体的三轴卸荷破坏试验,研究了节理岩体在卸荷应力条件下的应力-应变特征、强度、变形特征、破坏规律及节理间距对岩体力学性质的影响。研究表明：相比于完整岩体,节理岩体卸荷破坏时从峰值强度跌落至残余强度过程中轴向应变较大,为完整岩体的3～4倍,岩体破坏时极限强度明显低于完整岩体,脆性特征不如完整岩体明显;节理岩体卸荷破坏时,变形模量有较大幅度的降低,其降低程度是同条件下完整岩体的6～7倍,节理间距越大,变形模量降低程度越大;与含预制节理岩样三轴加载试验结果相比,节理岩体卸荷条件下破坏程度更为强烈,除剪切破裂面外,沿最大主应力方向分布的不同级别的张性裂隙非常发育,预制节理的间距对岩体破坏形态影响不大。 相似文献
5.
为研究交叉节理的存在对岩体破裂机制的影响,采用3D打印技术制备了可模拟岩体交叉结构面的节理模型,通过相似材料浇筑形成含预制交叉节理的试件,并基于数字图像相关技术（DIC）分析了单轴压缩下试件裂纹起裂、扩展及破坏模式。研究结果表明：采用3D打印技术制作的闭合节理模型,可以有效替代传统的切割、插缝等方法形成的张开型节理裂隙。基于此展开的试验结果表明,交叉节理存在会显著降低试件强度,且随着交叉角度的增大,试件强度先升高后降低,在45o和60o之间达到最大值,峰值应变与强度呈现相反的变化规律;裂纹扩展过程可分为微裂隙闭合阶段、微破裂发展阶段、主节理起裂扩展阶段和次节理迅速延伸阶段,这与应力?应变曲线各阶段一一对应。研究还发现,在交叉节理岩体中,次节理对破裂的影响主要体现在峰后阶段,结合最大畸变能理论表明,其对主节理尖端应力分布影响较小,主节理对岩体的破坏起绝对控制作用,这对岩体工程有一定的指导意义。 相似文献
6.
裂纹扩展方向的确定对分析岩桥破坏机制和岩体抗剪强度参数具有重要意义。首先以断裂力学观点推导了复杂应力条件下裂纹尖端应力分布函数的表达式,以节理岩体尖端的扩展裂纹可分为张拉裂纹和剪切裂纹为前提,基于Griffith破坏判据,提出了张拉裂纹扩展方向(张裂角)的计算公式;基于Mohr-Coulomb判据,提出了剪裂纹扩展方向(剪裂角)的计算公式。通过新判据与试验和其他判据的结果对比表明,该判据能准确判断张拉裂纹扩展方向,而剪裂角的扩展方向有待进一步试验验证。分析表明:在单向拉应力作用下,张裂纹扩展方向均有偏向于最大主应力方向的趋势,张裂纹与最大主应力夹角小于15°;双向拉应力作用下,随着微裂纹倾角变大,张裂纹有远离最大主应力方向的趋势;单轴压缩作用下,张裂角随裂纹倾角的增加而减小,而两者的和为先减小后增加。 相似文献
7.
白乃庙金矿区节理组合分析 总被引：1，自引：0，他引：1
白乃庙金矿区共发育3组共轭剪切节理,即东西向剖面共轭剪切节理,北东向和北西向平面共轭剪切节理,北北东向剖面共轭剪切节理.此外还发育张节理和局部节理.通过节理组合分析以及节理与主应力关系分析,确定出节理的成因、形成顺序以及节理与控矿断裂之间的成生联系. 相似文献
8.
The Schöllenen Gorge in the Reuss Valley of the Central Swiss Alps (Figs. 1 and 2) is a famous tourist attraction and ideal location for the study of the properties and formation mechanisms of uplift and post-uplift unloading joints. The gorge is situated in the southern part of the Central Aar Granite, a granitic batholith which intruded about 300 million years ago. The magmatic fabric of this batholith (Fig. 4) has only been locally modified during Alpine tectonic and metamorphic overprinting, mainly in the vicinity of ductile-brittle shear zones. The up to 600 m deep gorge provides an ideal opportunity to study the complex fracture systems of the batholith, and tunnels of the Göschenen hydropower system allow the study of the fracture patterns below ground surface. Outcrop, tunnel and remote mapping of fractures in the study area lead to the recognition of two probably syntectonic (Oligocene-Miocene) joint sets (S and Q joints) and three generations of uplift and post-uplift joints (unloading joints). The frequent S joints run nearly parallel to the Alpine schistosity, i.e. striking approximately E–W and dipping steeply to the south (Figs. 5 and 7). The less frequent Q joints dip steeply to SW; the angle between the two joint sets ranges between 60 and 80 degrees. The first generation of uplift joints (called L- joints) is subhorizontal and probably related to Alpine extensional veins filled with fissure quartz (Zerrklüfte). These veins formed during the late Alpine (Miocene) uplift of the Aar Granite (Mullis 1996). A first generation of post-uplift joints (T1 joints) strikes parallel to the valley axes and dip with 30–45 degrees towards the valley bottom. This set probably formed during an earlier stage of glacial valley erosion in the Pleistocene (Figs. 9–11). The youngest generation of post-uplift joints (T2 joints) is orientated parallel to the present ground surface of the Schöllenen Gorge and to erosional surfaces with glacial striations (Figs. 9–11 and 21). The frequency and size of these joints seems to decrease with depth below the ground surface. In one tunnel, post-uplift joints could be observed within a horizontal and vertical distance from the ground surface of 150 and 80 meters. Post-uplift joints only form in granites with a primary fabric that has not been intensively overprinted by brittle or ductile Alpine tectonic deformations. Fractographic investigations, i.e. investigations of crack propagation markers on joint surfaces, confirm this relative age of the fracture sets and give valuable insights into the formation mechanisms of post-uplift joints. Post-uplift joints show intense and 5–10 meter long plumose markings and only rarely arrest lines (Figs. 18a and 20). It can be shown that sets of post-uplift joints join at pre-existing (uplift and syntectonic) fractures to form large (50–100 m sized) curved exfoliation structures (Fig. 19). The growth direction of the post-uplift joints is mainly in subhorizontal directions (Figs. 19 and 20). Fractographic markings, spatial and depth distributions as well as the relative size of post-uplift fractures are explained within the mechanical framework of uniaxial and biaxial compression tests on intact granite samples and samples with artificial flaws. Most of these experiments have been carried out in the framework of studies related to brittle failure (spalling and rockbursting) around deep mining drifts and tunnels in hard rock’s (e.g. Hoek & Bieniawski 1965, Read et al. 1998, Eberhardt et al. 1999). As suggested already by Holzhausen & Johnson (1979), post-uplift fractures form as extension fractures in a compressive stress field with small confining stress. Laboratory tests carried out on artificial Griffith cracks suggest that the macroscopic fracture size is mainly controlled by the ratio of the smallest to the largest principal stress (σ3/σ1), the so-called spalling limit. In steep slopes this ratio should increase with depth below ground surface (Fig. 24c), leading to smaller exfoliation fractures with increasing depth. The spatial occurrence of post-uplift fractures along the surface topography is a function of the deviatoric stress level (Fig. 24a) and/or the development of local tensile stresses (Fig. 24d). Preliminary numerical simulations of these failure criteria in a multistage glacial erosion model (Fig. 23) allow some of the observed patterns of post-uplift fracture distributions to be reproduced. post-uplift joints in steep glacial valleys play an important role in valley erosion and in connection with the risk of rock falls, the safety of traffic corridors, and the inflow of water to near-surface tunnels and hydropower caverns. The depth dependant sizes, frequencies and hydraulic conductivities of these fractures can be directly related to the occurrence and magnitudes of the corresponding hazards. 相似文献
9.
Mapping the state of fracture around cavities 总被引：3，自引：0，他引：3
The state of stress around cavities is heterogeneous. Consequently, the state of fracture may also vary from point to point. Under compressive loading, cavity may be in one of four possible states: pre-fracture (pre-microfracture initiation), microfracture propagation (initiation to the onset of dilata dilatancy to failure) and post-failure. These four states are separated by the crack initiation stress, the crack damage stress and the failure stress. fracture events with confining pressure is examined with reference to three intact rocks: a brittle granite, a semi-brittle limestone and a ductile sal
The maximum principal stress (σ1) at crack initiation, crack damage (onset of dilatancy), yielding and failure are established as a function stress (σ3). For a single intact rock, all four fracture events can be represented using one function (the Rocker function) with a single fac various fracture states.
The proposed fracture criteria, based on the experimental data, are combined with the existing state of stress to prepare a fracture map around an elli intact Lac du Bonnet granite. The state of stability is expressed through a newly defined stability factor, the unconfined strength ratio (USR), wh to the traditional safety factor. In contrast to the conventional safety factor in rock mechanics (SFstrength/σ1), which is σ3
10.
在深部工程中经常会遇到层状岩体,由于高应力的影响,在工程活动中发生因层状结构面诱发的岩体灾害问题。这与深部工程中的真三向高应力环境及层状结构面产状密切相关。为此,基于一种取自某深部金属矿山的层状硬质片岩,开展了考虑片理方位的真三轴压缩试验研究,获取了该片岩在两种片理加载方位下,不同应力差条件时,试样的变形、强度及破裂数据。结果表明,该硬质片岩的力学特性受片理加载方位和应力条件影响较大。具体表现在,当中间主应力σ2平行片理走向时,试样的脆性更强,且最小主应力σ3 越小脆性越强。当σ2垂直片理走向时试样的强度更高,但强度随σ3增加而增加的敏感性较弱。当σ2平行片理走向时,试样的破坏均以沿片理的剪切为主;而当σ2 垂直片理走向时,试样在低σ3 时,主要发生穿片理的拉破坏,高σ3 时,则转变为沿片理的剪切破坏。试验结果对陡倾层状硬质岩体工程的稳定性评价有一定的启示意义,即当片理走向与洞轴线的夹角较小时,浅层围岩片理面的法向应力释放程度较高,易发生受片理结构控制的脆性破坏;反之,夹角较大时,岩体的稳定性较强。 相似文献
11.
The results are given for all the determinations made by the co-operating laboratories of major elements in the six NIMROC rock samples (granite, syenite, lujavrite, norite, pyroxenite and dunite) prepared by the National Institute for Metallurgy in 1966. Relevant statistical data are given for the sets of results for each major constituent, and recommended values for all constituents except Al2 03 , Na2 0, K2 0and CO2 in dunite, Fe2 O3 , MgO and CO2 in the granite, Fe2 3 and CO2 in the norite and CO2 in the pyroxenite.
This report and that on the trace and minor elements issued in 1978 complete the revision of the recommended values. It is suggested that analysts should concentrate rather on those constituents for which the results have shown such a wide scatter that they can be of no usc for reference purposes, than on those for which the ualues are fairly well established. 相似文献
This report and that on the trace and minor elements issued in 1978 complete the revision of the recommended values. It is suggested that analysts should concentrate rather on those constituents for which the results have shown such a wide scatter that they can be of no usc for reference purposes, than on those for which the ualues are fairly well established. 相似文献
12.
Agust Gudmundsson 《地学学报》1992,4(4):464-471
The divergent plate boundary in Iceland is characterized by 40–80 km long and 5–10 km wide swarms of tension fractures (∼102 m long) and normal faults (∼103 m long). The upper part of the crust is mainly composed of lava flows, with abundant columnar joints that are mostly perpendicular to the lava contacts. The lava flows are horizontal at the surface of the rift zone but become tilted at the rate of 1° for every 150 m depth in the crust. At the surface of the rift zone the joints are vertical and parallel to the vertical principal stress. Because of tilting of the lava pile, the columnar joints become oblique to this stress, hence becoming potential shear fractures, and form echelon sets at greater depths in the crust. Theoretical considerations suggest that normal faults start to nucleate on sets of en echelon columnar joints and/or large-scale tension fractures at crustal depths of 0.5–1.5 km. The width (depth) must be the smallest (controlling) dimension of many faults. Nevertheless, there is a positive linear relation (r = 0.91) between maximum throw and length of the Holocene faults. If the faults grow as self-similar structures, the throw-length relationship can be explained by a similar relation between fault length and width. 相似文献
13.
构造应力对裂缝形成与流体流动的影响 总被引：3，自引：1，他引：2
裂缝是低渗透储层流体流动的主要通道,控制了低渗透油气藏的渗流系统。低渗透储层裂缝的形成与流体密切相关,高流体压力引起岩石内部的有效正应力下降,导致岩石剪切破裂强度下降,使岩石容易产生裂缝。高孔隙流体压力还造成某一点的应力摩尔圆向左移动,可以使其最小主应力(σ3)由压应力状态变成拉张应力状态,从而在岩石中形成拉张裂缝。裂缝的渗透性受现今应力场的影响,通常与现今应力场最大主压应力近平行分布的裂缝呈拉张状态,连通性好,开度大,渗透率高,是主渗透裂缝方向。构造应力对沉积盆地流体流动的影响主要表现在三个方面:(1)构造应力导致的岩石变形,不仅提供了流体流动的通道,而且还改变了岩石的渗透性能;(2)在构造强烈活动时期,构造应力的快速变化是流体流动的重要驱动力;(3)岩石中应力状态影响多孔介质的有效应力,从而影响介质中的渗流场。当作用在含流体介质上的构造应力发生改变时,岩石孔隙体积变小,构造应力首先由岩石的骨架来承担;当岩石孔隙体积减小到一定程度时,构造应力由孔隙流体来承担,从而影响岩层渗流场的变化。 相似文献
14.
Wollastonite and scapolite in Precambrian calc-silicate granulites from Australia and Antarctica 总被引：2，自引：0，他引：2
Abstract Scapolite, wollastonite, calcite, diopside, grossular-andradite garnet and sphene occur in calc-silicate rocks in the granulite terrain of the Arunta Block, central Australia. This assemblage buffers the CO2 activity at a low value, so that any coexisting fluid phase must be H2 O rich and CO2 poor ( X co2 = 0.2-0.3). In contrast, the H2 O activity in the surrounding felsic and mafic granulites was low. Thus fluid activities during granulite facies metamorphism were locally buffered in various rock units and fluid flow appears to have been restricted or fluid may have been absent. Late retrograde rims of garnet and garnet-quartz separate phases formed in the high-grade stage. Formation of these rims would have required either an influx of water-rich fluid or a decrease in pressure. Evidence from the surrounding granulites shows that in one locality, the calc-silicate rocks had undergone late isobaric hydration; in another locality, minor uplift had occurred soon after peak P-T conditions. In both, scapolite had partly broken down to plagioclase-calite. A calc silicate rock from the granulite terrain of Enderby Land, Antarctica, contains scapolite, wollastonite, calcite, diopside, quartz and sphene; this assemblage also indicates low CO2 activities. In this rock, wollastonite has broken down to calcite-quartz, to indicate isobaric cooling without influx of hydrous fluid. 相似文献
15.
结构面力学性质的定量鉴定 总被引：8，自引：0，他引：8
变形带力学性质的鉴定是地质力学研究中的先行基础步骤.近来出现一些新的概念和方法,可用以定量表征变形带的力学性质.天然变形带通常是一般剪切作用的产物,是纯剪切(共轴缩短或伸展)和简单剪切的组合.为了定量说明两者间的相对贡献,提出了运动学涡度(Wk)这一物理量,并简单地定义为cos υ.υ是主变形面内两特征方向间的夹角.纯剪切的υ=90°,Wk=0;简单剪切的υ=0°,Wk=1.一般剪切的υ介于0°和90°之间,Wk为0到1.运动学涡度符号的正负分别代表变形带的减薄和增厚.υ可通过极摩尔圆法求出.主压应力(σ1)方向与Wk的关系为Wk=sin2ξ.ξ是σ1与变形带法线间的夹角.因此,可用以确定变形带的Wk和力学性质.根据最大有效力矩准则,韧性变形带与主压应力(σ1)方向间的夹角为55°,可用以确定古应力轴的方向,并可能确定变形时差应力的大小. 相似文献
16.
《Journal of Structural Geology》1988,10(6):541-553
Two-dimensional boudinage in a flattening type of bulk deformation, with equal layer-parallel extensions in all directions, leads to the development of roundish or polygonal outlines of boudins in plan-view. As combined experimental and theoretical studies show, chocolate tablet boudinage with two sets of mutually perpendicular boudin axes may form in different ways. (1) Unequal layer-parallel extension in the matrix results in one set of extension fractures forming perpendicular to the greatest principal stress in the matrix. Once these long narrow boudins are formed, the greatest principal stress in the brittle layer becomes approximately parallel to the long axis of the boudin. As a result a second set of fractures forms normal to the first set. (2) In lineated rocks the anisotropy of tensile strength leads to the sequential formation of two sets of extension fractures, parallel and perpendicular to the lineation. Depending on the orientation of the lineation the boudin axes may or may not be parallel to the principal stresses in the matrix. (3) Boudins with rectangular plan-view may also form when two successive events of unidirectional boudinage are superposed on one another. Irrespective of the direction of principal extensional strain rate in the matrix, the second generation extension fractures are likely to form approximately perpendicular to the first generation boudin axes. 相似文献
17.
In this paper, an anisotropic strength criterion is established for jointed rock masses. An orientation distribution function (ODF) of joint connectivity, is introduced to characterize the anisotropic strength of jointed rock masses related to directional distributed joint sets. Coulomb failure condition is formulated for each plane of jointed rock masses by joint connectivity, where the friction coefficient and cohesion of the jointed rock mass are related to those of the intact rock and joint and become orientation dependent. When approximating joint connectivity by its second‐order fabric tensor, an anisotropic strength criterion is derived through an approximate analytical solution to the critical plane problem. To demonstrate the effects of joint distribution on the anisotropic strength of jointed rock masses, the failure envelopes are worked out for different relative orientations of material anisotropy and principal stress axes. The anisotropic strength criterion is also applied to wellbore stability analyses. It is shown that a borehole drilled in the direction of the maximum principal in situ stress is not always the safest due to the anisotropic strength of the jointed rock mass. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
18.
天然岩体中常含有多组相互交叉的贯通节理,它们的存在极大地削弱了岩体的力学性质。为了研究含两组交叉贯通节理岩体的强度及破坏特征,基于弹塑性数值流形方法,对不同应力状态下,节理倾角和节理间距不同的岩体压缩试验进行数值模拟。结果表明：岩体强度随节理倾角的变化曲线呈现出多波峰、多波谷特点,岩体强度随节理间距变化曲线符合负指数函数形式。根据节理状态,两组节理岩体的破坏模式可以分为3种：岩块破坏、沿一组节理滑移和沿两组节理滑移。两组节理均会影响岩体强度,一组起主要作用,另一组起次要作用,并且节理组之间存在相互影响。通过对数值计算结果进行回归分析,基于一组节理岩体强度预测模型,量化节理组之间的相互影响,提出适用于含两组交叉贯通节理岩体的强度预测模型。模型形式简单,使用方便,可为实际工程中正确评估岩体强度提供指导性意见。 相似文献
19.
A. Ghazvinian V. Sarfarazi W. Schubert M. Blumel 《Rock Mechanics and Rock Engineering》2012,45(5):677-693
Particle flow code 2D (PFC2D) was adopted to simulate the shear behavior of rocklike material samples containing planar non-persistent joints. Direct shear loading was conducted to investigate the effect of joint separation on the failure behavior of rock bridges. Initially calibration of PFC was undertaken with respect to the data obtained from experimental laboratory tests to ensure the conformity of the simulated numerical models response. Furthermore, validation of the simulated models were cross checked with the results of direct shear tests performed on non-persistent jointed physical models. Through numerical direct shear tests, the failure process was visually observed, and the failure patterns were found reasonably similar to the experimentally observed trends. The discrete element simulations demonstrated that the macro-scale shear zone resulted from the progressive failure of the tension-induced micro-cracks. The failure pattern was mostly influenced by joint separation, while the shear strength was linked to the failure pattern and failure mechanism. Furthermore, it was observed that the failure zone is relatively narrow and has a symmetrical pattern when rock bridges occupy a low percentage of the total shear surface. This may be due to the high stress interactions between the subsequent joints separated by a rock bridge. In contrast, when rock bridges are occupying sufficient area prohibiting the stress interactions to occur then the rupture of surface is more complex and turns into a shear zone. This zone was observed to be relatively thick with an unsymmetrical pattern. The shear strength of rock bridges is reduced by increasing the joint length as a result of increasing both the stress concentration at tip of the joints and the stress interaction between the joints. 相似文献
20.
PAUL A. STUDEMEISTER 《Journal of Metamorphic Geology》1985,3(1):79-90
Abstract Two Archaean synvolcanic stocks with contact aureoles occur in the Wawa greenstone belt near Wawa, Ontario, Canada. The Gutcher Lake and Jubilee stocks consist mainly of granitoid trondhjemite with feldspar laths mottled by white mica + calcite + epidote and rimmed by clear albite. Biotite is partly or wholly pseudomorphosed by chlorite + sphene; some epidote is partly altered to calcite + chlorite. The granitoid phase grades into a foliated phase of quartz + albite + white mica + calcite + chlorite near fracture zones traversing the stocks.
The alteration of the Gutcher Lake stock along its foliated margin involved addition of K2 O, H2 O + CO2 , MnO, plus Rb; loss of CaO plus Sr; and a shift in Fe+2 /Fet from 0.66 to 0.81. The alteration of the Jubilee stock along the Darwin Shear involved addition of H2 O + CO2 ; loss of Sr; and no significant shift in Fe+2 /Fet . The greenschist alteration also modified the contact aureoles bordering both stocks.
One interpretation is that regional metamorphism in the Archaean overprinted a greenschist assemblage on both stocks. The alteration was intense near fracture zones and sporadic remote from fractures. Lower integrated water to rock ratios along the Darwin Shear compared to the margin of the Gutcher Lake stock may explain the comparatively lower perturbation of the element abundances and redox state of iron. 相似文献
The alteration of the Gutcher Lake stock along its foliated margin involved addition of K
One interpretation is that regional metamorphism in the Archaean overprinted a greenschist assemblage on both stocks. The alteration was intense near fracture zones and sporadic remote from fractures. Lower integrated water to rock ratios along the Darwin Shear compared to the margin of the Gutcher Lake stock may explain the comparatively lower perturbation of the element abundances and redox state of iron. 相似文献