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1.
There is a large database of triaxial stress measurements at the El Teniente Mine, Central Chile, but the complex geology, severe topography, and proximity of all measurements to extensive mining excavations made interpretation of the stress field difficult. The measurements were analyzed using three-dimensional numerical stress analysis and decomposition of the stress field into gravitational and tectonic components. By removing gravitational stresses plus local effects from the tectonic component of the stress field a calculation of the far-field tectonic stress tensor is made. It is shown that variations in the tectonic component of stress are related to shear zones cutting through the mine. The far-field major principal component of the tectonic stress field was found to be oriented approximately N–S. This is consistent with the most recent direction of local shortening based on kinematic analysis of faults, but is perpendicular to the direction of regional crustal shortening. There appears to be a limiting envelope to the magnitude of the stress field implying that the shear zones are in a state of limiting equilibrium with regional tectonic driving forces. 相似文献
2.
测定岩石经历的最高古应力状态实验研究 总被引：9，自引：1，他引：8
当前国内外尚无测定三维古构造应力场的理想方法.提出了一种新方法: 从待测地点取大岩心或新鲜石块, 从6个以上方向取岩石试样, 每方向至少10个试样, 以声发射的广义抹录不净现象, 测定岩石经历的各主要构造运动期的最大主应力值.而后, 统计出岩石记忆的最高古应力状态的最大主应力值σmt.由于岩石对最高古应力状态在各取样方向的正应力σmn尚有记忆, 只不过隐藏于各期较低古应力状态的最大主应力值之间, 不易区分, 故以σmt为目标, 通过“AE反演搜索法”, 则可将隐藏的各σmn搜索出来, 从而计算出岩石经历的最高古应力状态.以准平面应力状态模拟实验检验了该新方法的可行性. 相似文献
3.
为研究水力压裂时地应力对破裂压力和水力裂缝的影响规律,采用水力压裂试验系统,以相似材料作为研究对象,进行了水力压裂物理模拟试验,并借助煤岩断面三维扫描系统、位移计提取了水力裂缝信息。试验结果表明,随着主应力差的增大,破裂压力逐渐降低,破裂时间也逐渐缩短;随着主应力差的增大,破裂面的表面积逐渐增加,破裂面变得逐渐粗糙;围压相近时水力裂缝易出现转向、分叉,压裂液的动力效应越明显;水力裂缝张开度随着主应力差的增大而逐渐减小。研究结果可为水力压裂试验的进一步研究、裂缝网络系统的建立提供参考。 相似文献
4.
Contact mechanism of a rock fracture subjected to normal loading and its impact on fast closure behavior during initial stage of fluid flow experiment 
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下载免费PDF全文 Fast closure of rock fractures has been commonly observed in the initial stage of fluid flow experiments at environmental temperatures under low or moderate normal stresses. To fully understand the mechanisms that drive this fast closure, the evolution of local stresses acting on contacting asperities on the fracture surfaces prior to fluid flow tests needs to be evaluated. In this study, we modeled numerically the asperity deformation and failure processes during initial normal loading, by adopting both elastic and elastic–plastic deformation models for the asperities on a real rock fracture with measured surface topography data, and estimated their impact on initial conditions for fluid flow test performed under laboratory conditions. Compared with the previous models that simulate the normal contact of a fracture as the approach of two rigid surfaces without deformations, our models of deformable asperities yielded smaller contact areas and higher stresses on contacting asperities at a given normal stress or normal displacement. The results show that the calculated local stresses were concentrated on the contacts of a few major asperities, resulting in crushing of asperity tips. With these higher contact stresses, however, the predicted closure rates by pressure solution are still several orders of magnitude lower than that of the experimental measurements at the initial stage of fluid flow test. This indicates that single pressure solution may not likely to be the principal compaction mechanism for this fast closure, and that the damages on contacting asperities that occur during the initial normal loading stage may play an important role. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
5.
S. Y. Wang S. W. Sloan S. G. Fityus D. V. Griffiths C. A. Tang 《Rock Mechanics and Rock Engineering》2013,46(5):1165-1182
Rock is a heterogeneous geological material. When rock is subjected to internal hydraulic pressure and external mechanical loading, the fluid flow properties will be altered by closing, opening, or other interaction of pre-existing weaknesses or by induced new fractures. Meanwhile, the pore pressure can influence the fracture behavior on both a local and global scale. A finite element model that can consider the coupled effects of seepage, damage and stress field in heterogeneous rock is described. First, two series of numerical tests in relatively homogeneous and heterogeneous rocks were performed to investigate the influence of pore pressure magnitude and gradient on initiation and propagation of tensile fractures. Second, to examine the initiation of hydraulic fractures and their subsequent propagation, a series of numerical simulations of the behavior of two injection holes inside a saturated rock mass are carried out. The rock is subjected to different initial in situ stress ratios and to an internal injection (pore) pressure at the two injection holes. Numerically, simulated results indicate that tensile fracture is strongly influenced by both pore pressure magnitude and pore pressure gradient. In addition, the heterogeneity of rock, the initial in situ stress ratio (K), the distance between two injection holes, and the difference of the pore pressure in the two injection holes all play important roles in the initiation and propagation of hydraulic fractures. At relatively close spacing and when the two principal stresses are of similar magnitude, the proximity of adjacent injection holes can cause fracturing to occur in a direction perpendicular to the maximum principal stress. 相似文献
6.
The generation of intraplate earthquakes has been attributed to perturbations in the stress regime, either due to surface
and sub-surface loading or strength weakening of the rock mass. The present work aims at estimating the intraplate stresses
associated with topography and crustal density inhomogeneities beneath the Deccan Volcanic Province (DVP). A layered crustal
model with irregular interfaces of small amplitude has been used for elastostatic stress calculations. The computed principal
stress differences show a significant concentration at 5–20 km depths beneath the western side of the region. The maximum
magnitude of principal stress difference occurs beneath the Karad at a depth of 10 km with a value of 60 MPa. The deviatoric
stress estimates are further superposed on inferred stresses due to the regional plate tectonic forces. These results show
principal stress difference concentrations beneath the Koyna, Poona and Karad regions which may thus be more vulnerable to
brittle failure. It is also seen that the principal total stress directions point to the strike slip motion at Koyna, similar
to that which is associated with the 1967 Koyna earthquake. 相似文献
7.
为了避免均质和非均质模型不能较好地模拟围岩的层裂或板裂化现象,将岩石视为等效连续介质,即颗粒体材料。颗粒被视为弹性材料,而颗粒之间的界面破坏后被视为摩尔-库仑材料。颗粒和界面均被离散为正方形单元。采用FLAC研究了不同侧压系数时圆形巷道围岩中的剪切应变增量、最小、最大主应力等的分布规律。研究发现,颗粒体材料模型在压应力作用下诱发出的拉应力值接近于在模型边界上所施加的最大压应力,而最大压应力是所施加的最大压应力的数倍。这些结果意味着均质和非均质模型的计算结果是偏于不安全的。另外,最小主应力和剪切应变增量的等值线图均显示,这些量的高值区的距离大致相等,这与V形岩爆坑内的板裂化现象类似。围岩层裂现象的原因是环向的高压应力和径向的高拉应力的共同作用的结果。 相似文献
8.
The rock deformation and failure tests are performed along various stress paths under true triaxial stress state.
The experimental results have shown that the change of three principal stresses (the increase of the maximum principal stress, the decrease of the minimum principal stress, the decrease of the confining pressure and the increase or decrease of the intermediate principal stress ) can lead to deformation and failure in rocks. The strength, the deformability and the failure precursors of rocks are related with stress paths.
Based on the results of the study, the problems of the stress path in rock engineering are discussed. 相似文献
9.
The purpose of this paper is to clarify the concept of residual stress in rock. Residual stress is stress near a point in a body subjected to zero external tractions and to zero temperature gradients, excluding body forces. Thus, residual stresses can develop in rock if there are local phase transformations, inelastic strains, or differences in thermal or elastic properties. In these cases, residual stresses can result from changes in temperature, applied stress or configuration of the body.Analysis of residual stresses at the scale of mineral grains within a polycrystalline aggregate such as rock is virtually intractable. One can, however, obtain important insights into residual stresses within bodies with widely spaced sources of residual stress, such as inclusions, and within bodies comprised of multilayers. The analyses indicate that patterns of residual stress in rock can be expected to be extremely complicated. For example, study of residual stresses in a body containing a circular inclusion indicates that:
- 1. (1) There is a single state of residual stress within an inclusion but the state within the surrounding medium is variable. Thus, values of residual stress within rocks reported in the literature generally are of minor value because the sizes and shapes of the sources and the positions of the measurements relative to the positions of sources of residual stresses in the bodies have not been determined.
- 2. (2) Residual stresses within an inclusion can be tensile or compressive, even though the applied stresses were compressive, depending upon the source of residual stress.
- 3. (3) The magnitudes and orientations of residual stresses in an isolated body of rock containing one or more inclusions depends upon the size and shape of the body. The same general conclusions are derived from an analysis of residual stresses in a simple multilayered body.
- 4. (4) In addition, however, the anisotropy of a multilayered body tends to cause principal residual stresses to parallel the layers rather than to parallel the applied stresses that were responsible for inducing the residual stresses. Thus, without identifying the sources of residual stresses in a body, one cannot infer the directions of principal tectonic stresses that might have been responsible for the residual stresses.
10.
本文运用水压致裂地应力测量方法,对我国某地下油库预可行性研究工程场区两个钻孔进行了地应力测量。测量结果表明:最大和最小水平主应力(SH,Sh)都远大于对应深度处的垂向应力(Sv),三向主应力的关系为:SH > Sh > Sv,应力大小在该深度范围属中等偏大级别;工程场区最大水平主应力方向近EW方向,与测点外围确定的区域最大水平主应力总体方向较为一致;建议未来地下硐库长轴按近EW分布,地应力状态、岩体结构构造、岩石强度等基本保证了其岩体稳定性。 相似文献
11.
Wenhui Tan P. H. S. W. Kulatilake Hongbao Sun 《Geotechnical and Geological Engineering》2014,32(1):31-42
In-situ stress plays a major role with respect to deformation and stability around underground or surficial excavations located at significant depth. Many sedimentary rock masses are more or less horizontally bedded. However, a possibility exists to have one or few inclined rock strata such as dikes in these horizontally bedded formations. It is important to know how the in situ stress changes from a purely horizontally bedded situation to a horizontally bedded rock mass that contains one or few inclined rock strata. This paper presents such an investigation using the largest open-pit metal mine in China—as a case study. This mine has a bedded rock mass with one steeply inclined rock stratum. For the bedded rock mass, the vertical stress was calculated based on the overburden above each lithology. The available in situ stress measurements conducted at the mine were used to estimate the ratios of horizontal to vertical stress. Numerical modeling was performed for the two scenarios: (a) the horizontally bedded system subjected to both the in situ and boundary stresses and (b) the mine lithological system that includes an inclined stiffer (denser) stratum intruding softer horizontally bedded system subjected to only boundary stresses to investigate the influence of an inclined rock stratum on the computed stress field. Thirty points were selected to compute the stresses on six planes of the inclined rock stratum. Due to the discontinuous nature of the geologic system at the interface between the stiffer inclined stratum and softer horizontally bedded system, one principal stress has become normal to the interface plane and the other two have become parallel to the interface plane with all three being perpendicular to each other. Presence of the stiffer inclined rock stratum has given rise to (a) increase in normal stresses up to about 120 % in the inclined rock stratum and (b) new shear stresses approximately in the range ?10.0 to 15.0 MPa. This means, because most of the rock masses are not purely horizontally bedded, estimation of in situ stress through measurements as well as application of in situ stress in numerical modeling associated with underground or surficial excavations located at significant depth is a difficult exercise. A better way to estimate the in situ stresses for complex geologic systems may be through application of appropriate boundary stresses to the geologic system in a numerical model. 相似文献
12.
地应力测量及其地下工程应用的思考 总被引：16，自引：1，他引：15
国内外地应力实测资料证实,地表附近构造应力受多种影响因素的干扰,经常叠加着非构造应力(如地形等引起的应力)。为此,本文讨论了地应力测量及其地下工程应用值得注意的问题。地应力测量前应充分考虑测量孔位的选定和地形地貌、岩性、断裂等的影响;地应力测量后应对测值的各种影响因素和可靠性进行分析、进行岩石力学性质校正和对比分析以及测值的代表性分析等;工程应用应考虑具体工程所处不同构造部位、不同岩性、不同岩体结构、不同深度等局部地应力状态的变化和差异,此外,工程本身不同的设计结构、尺寸等引起的局部地应力状态变化也需予以充分考虑。 相似文献
13.
深埋特长隧道工程的高地应力问题越来越受到重视,如何准确高效地确定工程区地应力状态,是目前关注的重点和难点。针对深埋特长隧道地应力状态的确定问题,我们提出了基于多源数据的初始原地应力方向综合确定和应力量值预测及复核的综合解决方案。通过勘察阶段有限钻孔的地应力测试,并结合区域多源地应力资料,可以综合确定地应力方向并利用修正的Sheorey模型预测隧道轴线地应力;针对预测结果,在隧道开挖施工过程中,进一步利用有限钻孔的水压致裂地应力测试检验预测结果并复核隧道应力状况。结果表明,桃子垭隧道水平最大主应力方向为N15°W~N40°W,实测三向应力关系为SH≥Sv＞Sh;钻孔附近的应力预测值在区域实测应力量值变化范围内,隧道埋深最大处的水平最大、最小应力值分别达24 MPa和16 MPa;隧道施工过程中的4个钻孔应力量值复核结果显示,除了局部受到岩性变化、断裂破碎带等影响出现偏差,本文预测结果与实测应力量值基本一致。笔者发展的原地应力综合预测及复核方法,一方面可以快速有效地预测深埋特长隧道等线状工程的原地应力状态,有效降低初始勘察阶段地应力测试成本,另一方面,应力量值的复核保证了应力预测结果的可靠性,可以为隧道施工方案的及时变更及预算调整等提供有力依据和数据支撑。 相似文献
14.
The link between stress and hydrologic properties was examined at two sites that are distinguished by different rock types
and different stress states. This investigation is based upon the analysis and interpretation of geophysical logs obtained
in water wells at the two locations. At the northeast site (Newark Basin), the hydrologic characteristics of sedimentary rocks
are dependent upon the relationship to the current regional stress field of two primary types of orthogonal features that
serve as preferential pathways for fluid flow. Subhorizontal bedding-plane partings are highly transmissive near the surface
and delineate transversely isotropic fluid flow at shallow depths. With increasing depth, the subhorizontal planes become
less dominant and steeply dipping fractures become more influential hydrologically. These high-angle features define anisotropic
flow pathways that are preferentially oriented along strike. At the southwest site (west Texas), extrusive rocks are subjected
to topographically modified tectonic and gravitational stresses that vary spatially within a valley setting. The attendant
changes in stress invariants cause fracture connectivity within the rock mass to systematically increase with depth along
the valley flanks, but to remain relatively low in the central valley. The degree of fracture connectivity predicted within
this valley configuration is consistent with variations in transmissivity determined at several well locations. In each of
these cases, the idealized understanding of the hydrologic system is enhanced by considering the effects of regional and local
stresses that act upon the fractured-rock aquifer.
Electronic Publication 相似文献
15.
16.
拟建中尼铁路位于印欧板块碰撞推挤的前缘地带,区域深大断裂发育,地震频发,新构造活动强烈,应力状态复杂。基于中尼铁路交通廊道震源机制解及原地应力测量资料,分析中尼铁路沿线区域构造应力场分布特征,进一步讨论现今构造应力场对铁路方案和重要工程设置的潜在影响。研究结果表明,研究区震源深度主压应力优势方向在板块碰撞边界为NEE向,高原内部则表现出明显的非均匀性特征。中国境内日喀则至吉隆段主要处于拉张-剪切应力环境,尼泊尔境内区段处于印欧板块推挤控制的挤压应力环境。在缺少中尼铁路沿线原地应力实测资料的现状下,结合邻区实测数据分析认为,该区地壳浅表层应力结构以逆断型为主,水平最大主压应力优势方向为NE向。基于研究区内主应力方向分布特征将中尼铁路沿线划分为日喀则―萨迦、萨迦―定结、定结―吉隆、聂拉木、吉隆―讷瓦果德和加德满都共6段。根据构造应力场分析结果并基于σθmax/Rc理论对铁路隧道工程围岩岩爆可能性进行了讨论,结果表明最大水平主应力方向与隧道轴向夹角较大时对隧道围岩稳定性不利,且隧道埋深越大则围岩岩爆的可能性越大。中尼铁路大多区段轴向与最大水平主应力方向呈大角度相交甚至近垂直,当隧道埋深较大时具有发生岩爆的可能,需重点防护。研究结果可为中尼铁路交通廊道工程勘察选线提供参考。 相似文献
17.
Plane Strain Testing with Passive Restraint 总被引：1，自引：0，他引：1
A plane strain condition for testing rock is developed through passive restraint in the form of a thick-walled cylinder. The so-called biaxial frame generates the intermediate principal stress that imposes a triaxial state of stress on a prismatic specimen. Major and minor principal stresses and corresponding strains are accurately measured, providing data to calculate the elastic (Young’s modulus and Poisson’s ratio), inelastic (dilatancy angle), and strength (friction angle and cohesion) parameters of the rock. Results of experiments conducted on Indiana limestone in plane strain compression are compared with the results of axisymmetric compression and extension. With proper system calibration, Young’s modulus and Poisson’s ratio are consistent among the tests. The plane strain apparatus enforces in-plane deformation with the three principal stresses at failure being different, and it allows one to determine the Paul-Mohr-Coulomb failure surface, which includes an intermediate stress effect. 相似文献
18.
SummaryRock Bursting Phenomena in a Superficial Rock Mass in Southern Central Sweden Rock bursting phenomena have been observed in connection with excavation of two shallow sited rock tunnels in the Forsmark area in southern, central Sweden. The tunnels are excavated in gneiss granite and the rock cover varies between 5–15 m. The stress release occurred locally in the tunnels which indicates significant variations in rock stresses.In situ measurements of the triaxial stress situation carried out in the area show values of the principal stresses in the horizontal plane of a magnitude in excess of 20 MPa in the superficial rock mass. The rock stress measurements indicate a clear correspondence of the directions of the highest compressive stress and the rock foliation. There is also a clear correspondence between the directions of a vertical and a horizontal joint set and the highest compressive stress. The three-dimensional stress tensor indicates that the horizontal fractures are exposed to the smallest closure pressure, i. e. the vertical stress, which set should therefore be most open. The horizontal joint set in the superficial rock mass has a significantly higher value of aperture than the vertical sets which may be a consequence of the stress situation in the rock mass. The rock bursting is not attributed to a breakage of the rock matrix, but merely to a propagation of already existing small fractures and potential fractures. The stress situation in the Forsmark area may be regarded as an uniaxial stress field in the horizontal plane.With 12 Figures 相似文献
19.
In this paper, it was determined that all of the three-dimensional principal stresses increase with depth and that both the maximum and the minimum stresses tend to be aligned in the horizontal orientation. The numerical simulation model was built using the software FLAC3D to simulate two times, as in two different states of original rock stress, respectively; this simulation was used to investigate how the original rock stress affects the gas outburst risk. The results suggest that an outburst is most likely to happen when the maximum original rock stress is perpendicular to the roadway, rather than parallel to the roadway. The results were demonstrated to be correct by a field experiment. The results suggest that most of the roadways in gas outburst risk coal mines should be designed to lie parallel to the maximum stress direction to avoid the high stress concentration in front of the heading face, thereby reducing the gas outburst risk. 相似文献
20.
钻孔岩芯饼状断裂破坏机制 总被引：2，自引：1，他引：2
本文首先阐述岩芯饼状断裂及其特征, 进而用断裂力学的理论与方法对岩饼破坏进行了断裂扩张机制的分析, 不但合理地解释了断裂特征及断裂破坏机制, 且以二滩坝址为例, 分析了产生钻孔岩饼的微裂纹条件及应力条件, 为定量地评价坝址地应力状态, 包括其大小及方向提供了一种新的方法。上述不仅具有重要的理论意义, 而且具有重要的工程实际意义。 相似文献