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1.
变形模量作为表征岩体变形特征的重要参数,是岩体工程设计的基础力学参数之一。在综合前人研究的基础上提出了基于三维结构面网络模拟确定岩体变形模量的方法,编制了三维结构面网络模拟及计算RQD值的程序。以西南山区某水电站坝址区岩体为实例,在概率统计各组优势结构面几何要素分布形式的基础上,采用Monte Carlo法生成三维结构面网络模型,据此获得岩体三维RQD值,利用RMR法进行质量评价和变形模量的确定,并与钻孔资料统计法和原位试验结果进行对比分析。结果表明:基于钻孔资料统计的估算结果与原位试验相对误差达31.62%,且其估算值偏低;基于三维结构面网络模拟的估算结果与原位试验相对误差仅为2.56%,估算结果精度较高。该方法考虑了岩体质量的空间各向异性,对岩体的质量评价和参数确定更为合理,研究成果为该工程的优化设计提供了合理的计算参数。 相似文献
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三维网络结构岩体力学是岩体力学的一个分支。根据笔者20余年对裂隙岩体研究的心得,阐述了三维网络结构岩体力学的主要特点、研究对象,基本架构、主要研究内容与未来的展望。将岩体结构控制论归结为材料强度控制、结构类型控制、渗流通道控制和几何边界控制4个方面。技术层面的主要内容包括三维RQD估算、岩体表征单元估算技术、结构块体搜索技术、定向投影岩体结构面三维连通率估算技术以及岩体三维渗径搜索技术等。理论层面主要由球面投影理论、概率统计理论、随机动力学、几何拓扑理论、块体理论、非线性系统理论和裂隙岩体多尺度等效结构模型等构成。强调足量的随机不连续面地质信息的原位统计取样是三维网络结构岩体力学的基础,岩体随机不连续面三维网络数值模拟技术是三维网络结构岩体力学的核心技术。 相似文献
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Changes in the hydraulic conductivity field, resulting from the redistribution of stresses in fractured rock masses, are difficult to characterize due to complex nature of the coupled hydromechanical processes. A methodology is developed to predict the distributed hydraulic conductivity field based on the original undisturbed parameters of hydraulic conductivity, Rock Mass Rating (RMR), Rock Quality Designation (RQD), and additionally the induced strains. The most obvious advantage of the methodology is that these required parameters are minimal and are readily available in practice. The incorporation of RMR and RQD, both of which have been applied to design in rock engineering for decades, enables the stress-dependent hydraulic conductivity field to be represented for a whole spectrum of rock masses. Knowledge of the RQD, together with the original hydraulic conductivity, is applied to determine the effective porosity for the fractured media. When RQD approaches zero, the rock mass is highly fractured, and fracture permeability will be relatively high. When RQD approaches 100, the degree of fracturing is minimal, and secondary porosity and secondary permeability will be low. These values bound the possible ranges in hydraulic behaviour of the secondary porosity within the system. RMR may also be applied to determine the scale effect of elastic modulus. As RMR approaches 100, the ‘softening’ effect of fractures is a minimum and results in the smallest strain-induced change in the hydraulic conductivity because the induced strain is uniformly distributed between fractures and matrix. When RMR approaches zero, the laboratory modulus must be reduced significantly in order to represent the rock mass. This results in the largest possible change in the hydraulic conductivity because the induced strain is applied entirely to the fracture system. These values of RMR bound the possible ranges in mechanical behaviour of the system. The mechanical system is coupled with the hydraulic system by two empirical parameters, RQD and RMR. The methodology has been applied to a circular underground excavation and to qualitatively explain the in situ experimental results of the macropermeability test in the drift at Stripa. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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为研究裂隙岩体结构效应对其等效力学参数的影响,引入基于离散元的合成岩体技术,通过可控的改变三维岩体结构网络中的结构参数,制作相应的合成岩体试件,开展计算机模拟试验研究。结果表明：随岩体中裂隙体积密度增大,裂隙的变形参数和强度参数随裂隙密度增加而减少,其中等效弹性模量对结构面密度变化最为敏感;随岩体中裂隙倾角增加,岩体等效弹性模量随之单调增加,且等效弹性模量的离散程度（标准差）随倾角增加而减小,而各强度参数指标则先减少而后增加,形成一个U形变化规律;岩体等效力学参数均随结构面尺寸增加而减小,同时等效力学参数的离散程度（标准差）随结构面直径增加而增加,其中单轴抗压强度指标变化最为敏感;岩体等效力学参数对裂隙尺寸和产状的离散程度不敏感。该研究结论可为其他结构效应研究提供一种新思路。 相似文献
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准各向同性裂隙岩体中有效动弹性参数与弹性波速关系的研究 总被引：4，自引：0，他引：4
从弹性波在介质中传播的特点和弹性波法在岩体工程中的实际应用情况方面,分析了弹性波在含裂隙岩体介质中的传播特征。将岩体中裂隙呈随机分布的裂隙岩体似为准各向同性裂隙岩体,根据能量平衡原理、岩石断裂力学理论和卡氏最小功能定理(Castiglano’s theorem),确定了准各向同性裂隙岩体的有效动弹性参数( 、 、 )与裂隙密度参数(Xv)的数学关系。在此基础上,根据各向同性介质中传播的弹性波理论,建立了准各向同性裂隙岩体中弹性波速( 、 )和 / 与裂隙密度参数(Xv)之间的关系。理论研究表明,在此裂隙岩体中,有效动弹性参数和弹性波速与裂纹密度参数之间相互的关系均近似成倒数函数的非线性关系;裂隙密度参数增加,有效动弹性模量( )也减少,弹性波速( , )也减小;在裂隙密度参数较小时,此裂隙岩体的有效弹性模量和弹性波速随裂隙密度参数的变化较大,说明裂隙体的有效弹性参数和弹性波速对裂隙体非常敏感。 相似文献
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利用RQD估算岩体不同深度的平均渗透系数和平均变形模量 总被引：2，自引：1，他引：1
渗透系数是进行裂隙岩体渗流模拟的必备参数,变形模量是工程岩体数值模拟的必备参数。大量研究中忽视了渗透系数和变形模量随深度变化这一重要规律,从而影响模拟结果的可靠性。为此,探讨了利用极易获取的RQD（岩石质量指标）资料估算不同深度的渗透系数和变形模量的可行性。通过以某花岗岩体为例,研究发现,RQD均值随深度增大,渗透系数均值随深度减小,其相关性很好。因此,利用RQD估算不同深度的平均渗透系数是可行的。根据RQD随深度的变化,利用经验公式估算了不同深度的变形模量均值和变化范围。估算得到的变形模量与实测结果基本一致。 相似文献
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Rock Mass Rating (RMR) measurements from 65 sites within Huntly East underground coal mine are presented. All measurements are in coal, for which the dominant discontinuities are vertical cleat. Basic RMR values using two discontinuity spacings are presented: overall RMR based on the average spacing of all individual discontinuities; and cleat zone RMR based on the average spacing between zones of cleat. Cleat orientations are highly variable, but on average approximately parallel horizontal stress axes (face cleat follows maximum horizontal stress axis, butt cleat follows minimum horizontal stress axis).Contours of RMR variations throughout the mine are used to compare rock mass conditions with geological structure. It is apparent that: (1) RMR is least within downthrown fault blocks, and particularly immediately on the downthrown sides of faults, and greatest in upthrown fault blocks; and (2) RMR contours parallel horizontal stress axes within fault-bounded blocks, and bend to parallel faults at block boundaries. From similar contours for parameters contributing to RMR, the Rock Quality Designation (RQD), groundwater rating, and discontinuity condition rating create most of the observed variations in RMR. RQD is determined from the measured discontinuity frequency and hence is a measure of the degree of fracturing of the rock mass. This is interpreted as influencing the groundwater and condition parameters directly by allowing greater water ingress. Discontinuity frequency is greatest (least spacing) in the immediate vicinity of faults, and in downthrown fault blocks, generating low RMR values. Within fault blocks RQD varies little, so RMR contours align with cleat orientations.As RMR contours, faults, stress field and cleat orientation are clearly interrelated, there is unequivocally a connection between RMR and structural geology; this allows some predictive capacity in terms of ground conditions. If geological features can be accurately defined through either drilling programs or seismic surveys, then ground conditions may be predicted before panels are driven. 相似文献
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Stochastic seismic wave interaction with a slippery rock fault is studied, based on the principle of conservation of momentum
at the wave fronts along the fault. By using the displacement discontinuity method, the wave propagation equations are derived
for incident longitudinal-(P-) and shear-(S-) waves, respectively. This is an extension of the study by Li and Ma (2010) for
blast-induced wave propagation across a linear rock joint. Stochastic seismic waves are generated from a frequency spectrum
and used to analyze the seismic wave interaction with a rock fault having a Coulomb-slip behavior. Parametric studies are
carried out to investigate the effect of the intensity and impinging angle of the incident seismic waves on wave propagation
across a slippery rock fault. Results show that the transmission of the incident P-wave is almost not affected by the fault,
on the contrary, this is not the case for an incident S-wave, due to the occurrence of a relative slip which is related to
the impinging angle of the incident S-wave. A quantitative study is presented which is of help in understanding the propagation
and attenuation laws of seismic waves in discontinuous rock masses. 相似文献
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Experimental studies were carried out in laboratory in order to investigate the effects of fracture on compressional (P) wave and shear (S) wave velocity propagation and therefore the relations between seismic properties and rock mass parameters. The discontinuity index, Id, fracture density parameter C, linear fracture parameter Γ and the rock quality designation (RQD) were used to describe the rock mass parameters. These parameters are analyzed and then related to the seismic properties. Four vertical aligned fractures were created on an intact calcarenite block, 0.6 m long, 0.4 m thick and 0.4 m width, by sawing. The measures were carried out in four different blocks of cacarenite, having the same physical properties, and in four different phases: in first block the fractures were filled with air; in the second block the fractures were filled with “terra rossa”; in third block the fractures were filled with wet “terra rossa” and in the fourth block the fractures were filled with clay. The test results were statistically analysed using the method of least squares regression and polynomial relationships with high correlation coefficient were found between the fractured rock parameters and P-wave, S-wave velocities and Vp/Vs ratio. The investigations suggest that the P-wave and S-wave velocities decrease with increasing the fracture parameters, while the Vp/Vs ratio increases with decreasing the fracture parameters.
Furthermore the results of the experimental studies were applied on the seismic refraction tomography data acquired in a great measurements campaign undertaken in the Adriatic salentina coast (south Italy) in order to monitor the coastal erosion.
The geophysical results, using the polynomial relationships between the fractured rock parameters and P-wave velocity, are in good agreement with the geomorphological and geological results. 相似文献
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Statistical analysis of some main geomechanical formulations evaluated with the Kaniadakis exponential law 总被引：1，自引：1，他引：0
Pierpaolo Oreste 《Geomechanics and Geoengineering》2018,13(2):139-145
The following paper reviews four well-known geomechanical equations, i.e. the elastic modulus of the rock mass as function of the Rock Mass Rating (RMR) system, the relation between Rock Quality Designation (RQD) and spacing distribution of the natural discontinuities in the rock mass, the distribution of the discontinuity spacing along a straight line for a rock mass and the intact rock strength in function of the specimen diameter by using a power-law flat tails equation based on the theory of Kaniadakis. The results show that by using novel formulations, the experimental data are better approximated by the power-law flat tails statistical approach, which shows a trend similar to ordinary exponential for a certain part of the interval of variability of x; the tails, however, follow the power law for extreme values of x. It was, therefore, possible to obtain new formulations able to better represent some fundamental aspects of geomechanics. 相似文献
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铁路岩质边坡的RQD研究 总被引：3，自引：0，他引：3
以宝成铁路略阳站前后一段铁路工程边坡为例,采用蒙特卡洛原理和方法,计算模拟铁路边结构面概率参数,利用统计结果估算边坡岩体的岩石质量指标ＲＱＤ,提出方向ＲＱＤ的概念,初探方向ＲＱＤ值在铁路工程边坡中的应用及铁路开挖工程活动与自然地质环境间的相互影响。 相似文献
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基于现场试验的岩体变形模量尺寸效应研究 总被引：6，自引：4，他引：2
岩体力学参数具有随机性和不确定性,合理确定岩体力学参数是岩土工程稳定性分析的基础和关键。以某水电站前期研究的110个钻孔弹模测试数据为研究样本,对其进行了统计特征分析,确定变形模量的概率分布特征更符合Weibull分布。以钻孔弹模仪承压板尺寸为岩体变形模量研究的样本尺度,岩体由该尺度的岩样叠加而成,建立了不同尺寸的立方体岩体数值分析模型,按照Weibull分布随机给出各岩样的变形模量,在此基础上对不同尺寸的岩体分别进行5 000次单轴压缩试验的数值模拟,得到了不同尺度岩体等效变形模量的变化特征,确定了岩体等效变形模量的REV。基于现场实测岩体变形模量与概率统计理论相结合研究岩体变形模量是一个新的尝试,可为该水电站工程岩体力学参数的合理取值提供依据。 相似文献
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This paper evaluates the existing equivalent medium methods for jointed rock mass and further develops the equivalent viscoelastic medium method proposed by the authors. The advantages and limitations of different equivalences to the discontinuous rock mass are discussed. Theoretical derivation of stress wave propagation through the equivalent viscoelastic medium is carried out by adopting the Fourier transformation method, and the parameters of the equivalent viscoelastic medium method are determined analytically. The frequency dependence and the wave attenuation phenomenon can be properly described when the imaginary terms of the complex moduli of the rock mass are included. The results show that the equivalent viscoelastic medium method is able to predict the effective velocity and the stress wave transmission coefficient in a rock mass more accurately than the conventional effective elastic moduli methods. An example of the stress wave propagation through rock mass with parallel joints shows that the equivalent viscoelastic medium method is promising and worthy to be further explored for application in practical rock engineering problems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Zekai en 《Mathematical Geology》2000,32(8):985-999
An important factor in the rock quality assessment analysis from discontinuity measurements along a scanline is the correlation of intact lengths. The autorun model and first order autorun coefficient are proposed as a method for objectively quantifying intact length correlation structure and discontinuity occurrences along any scanline. Necessary definitions for the methodology are presented on a quantitative basis such as the alternative intact length percentages and experimental autorun coefficient. An expression is proposed for the number of discontinuity occurrences along a scanline depending on the scanline length, alternate intact length percentages, and the autorun coefficient. Monte Carlo simulation technique is used with a suitable autorun model to verify this expression. A mathematical expression is derived for the expected Rock Quality Designation (RQD) value by taking into account the correlation of the intact lengths. Additional simulations show the validity of the new RQD expression. With the methodology proposed much less engineering experience and judgment are required in estimating the RQD value from scanline measurements. The application of the methodology has been presented for some field data. 相似文献
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选用三参数标准线性固体作为岩石本构,提出了一种考虑岩体黏弹性的位移不连续模型;根据一维黏弹性波的特征线法,推导了节理处质点速度、应力和应变递推公式。首先,基于分离式霍普金森压杆（SHPB）对砂层进行试验,得到其应力-应变关系,并换算出砂层节理的法向刚度;接着,通过一维强间断黏弹性波的波速公式、高频波衰减系数以及任一频率下的衰减系数,确定出数值算法中的三参数。最后,基于自制的摆锤装置,探讨了一维应力波在节理岩体中的传播规律,试验中以两根长1 000 mm、直径为68.50 m的岩杆作为入射和透射杆,以3 mm砂层模拟节理。试验和数值结果吻合度良好,进一步验证了该方法的可靠性。 相似文献
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Summary ?Strain-dependent hydraulic conductivities are uniquely defined by an environmental factor, representing applied normal and
shear strains, combined with intrinsic material parameters representing mass and component deformation moduli, initial conductivities,
and mass structure. The components representing mass moduli and structure are defined in terms of RQD (rock quality designation)
and RMR (rock mass rating) to represent the response of a whole spectrum of rock masses, varying from highly fractured (crushed)
rock to intact rock. These two empirical parameters determine the hydraulic response of a fractured medium to the induced-deformations.
The constitutive relations are verified against available published data and applied to study one-dimensional, strain-dependent
fluid flow. Analytical results indicate that both normal and shear strains exert a significant influence on the processes
of fluid flow and that the magnitude of this influence is regulated by the values of RQD and RMR. 相似文献
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Numerical computations of rock dissolution and geomechanical effects for CO2 geological storage 
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下载免费PDF全文 The paper is motivated by the long‐term safety analysis of the CO2 geological storage. We present a methodology for the assessment of the geomechanical impact of progressive rock dissolution. The method is based on the use of X‐ray tomography and the numerical dissolution technique. The influence of evolution of the microstructure on the macroscopic properties of the rock is analysed by using periodic homogenization method. The numerical computations show progressive degradation of all components of the stiffness (orthotropic) tensor. Moreover, the evolution of associated mass transfer properties (as tortuosity and conductivity tensors), by using the periodic homogenization method, is also calculated. The correlation between the mechanical parameters and the transfer properties during the dissolution process is presented. The results show that the highest increase of the hydraulic conductivity (in direction Y) is not associated with the highest decrease of Young modulus in this direction. Moreover, the highest decrease of Young modulus (in the direction X) is not associated with percolation in this direction. Finally, an incremental law to calculate settlement, in case of a rock with evolving microstructure, is proposed. The solution of the macroscopic settlement problem under constant stress and drained conditions showed that the geomechanical effects of the rock dissolution are rather limited. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献