巴东县杨家坪煤炭采空区岩体力学性质试验研究

对杨家坪煤炭采空区主要岩层进行了较系统的试验研究,包括岩体结构的野外调查、岩块与结构面室内试验及岩体力学参数经验估算,岩体结构面网络模拟等。对各种试验数据进行了分析整理,得到了岩块、结构面的物理力学性质参数。并用岩体工程分类及Hoek-Brown经验方法对各类岩体的力学参数进行了估算。在分析对比基础上,考虑了岩体所处地质条件,给出了各种岩体的计算参数建议值。有限元计算结果表明,建议参数值能较好地反映采空区岩体的力学性质。     

单轴压应力下砂岩岩块的变形和破坏研究

一、研究的目的和内容重视宏观的和微观的地质因素的岩体力学试验研究,有助于较真实地解释和确定岩块和岩体的变形、破坏的机理和力学的宏观现象,可以为选择和建立它们的破坏准则和强度理论,进行地壳岩体和工程岩体的稳定性分析评价等提供有用资料. 岩体是由宏观的结构面和结构体所构成,是地质体的一部分.岩体中包含着岩块.岩块和岩体的建造和改造决定了它们的物质组成和结构构造.     

基于量化的GSI系统和Hoek-Brown准则的岩体力学参数的估计

Hoek-Brown强度准则与Mohr-Coulomb强度准则相比,综合考虑了岩体结构、岩块强度、应力状态等多种因素的影响,可更好地反映岩体的非线性破坏特征,更符合工程实际,由该准则所估算的岩体力学参数可为最终确定岩体力学参数提供重要依据。基于引入的岩体体积节理数Jv和结构面条件因子JC量化的GSI(地质强度指标)围岩分级系统和Hoek-Brown强度准则来估计岩体力学参数,并结合具体的工程估算岩体的力学参数验证应用效果,其成果对工程设计和施工有重要指导意义。     

岩块与岩体的强度

本文以试验资料为依据,论述了岩块和岩体的单轴强度与极低应力区剪切强度参数之间的相互关系,并在简要介绍霍克—布朗强度准则的基础上,提出了确定岩体常数s与m的新方法,进而分别讨论了各向同性和各向异性岩体三轴强度的近似确定问题。     

岩体完整性系数确定及应用中的几个问题探讨

岩体完整性系数是一个与岩体质量和强度有关的地质参数,用于岩体完整程度划分、工程岩体质量分级等方面。然而不同的规范在岩体完整性系数的确定和应用等方面存在分歧。本文分析了岩体波速测试方法、岩体风化状态对岩体完整性系数的影响以及岩体体积节理数与岩体完整性系数的关系,并对岩体完整性系数应用中存在的问题进行了探讨。确定岩体完整性系数时,若岩块与岩体弹性波速的测试方法不同,应进行修正。所测试的岩块与岩体应处于相同的风化状态。采用岩体体积节理数确定岩体完整性系数时应考虑岩体中结构面的张开宽度和充填情况。应注意区分规范中围岩工程地质分类与岩爆判别中的围岩强度应力比的不同地质含义。     

贯穿裂隙岩体强度和破坏方式的模型研究

隧道等洞室开挖后,其周边通常会产生许多贯穿裂隙,直接影响到围岩稳定。研究贯穿裂隙岩体的强度及其破坏方式对于围岩加固等具有重要意义。基于库伦强度准则,通过建立数学模型,利用 - 坐标系下裂隙面和岩块的强度曲线位置关系研究了贯穿裂隙岩体强度和破坏方式。探讨了贯穿裂隙岩体强度与裂隙面的倾斜角、黏聚力和内摩擦角及岩块的黏聚力和内摩擦角间的关系,得到了贯穿裂隙岩体破坏方式的相关判据。数值算例表明该模型能够预测在任意最小主应力下贯穿裂隙岩体的强度和任意加卸荷路径下岩体破坏方式,与传统的利用 - 坐标系下裂隙面、岩块的强度曲线和摩尔应力圆的位置关系来判断岩体破坏方式的方法相比,该模型的方法更简便有效,结论更直观,能更好地为工程设计和岩体加固提供技术支撑。     

大跨度采空区软弱破碎岩体加固与利用

作者根据采空区岩体结构特征，通过内模拟试验和岩块尺寸效应试验，研究了岩体的变形和破坏特征，对矿柱和护顶矿柱分别提出了加固补强措施。     

块系岩体滑移失稳中低摩擦效应的理论与试验研究

深部岩体具有块状层次结构,深部动载造成岩块发生相互间的振动脱离产生低摩擦效应,从而极易诱发原先处于平衡状态的岩体的动力变形破坏。在前人研究基础上,将块系岩体振动简化为等效质量-黏弹性模型,引入岩石摩擦滑移速率弱化模式,最终得到块系岩体滑移失稳计算模型。通过计算分析块系岩体自身特性及外荷载特性对岩块间低摩擦效应的影响。理论计算表明：水平静力及外扰动保持不变,增大岩块间弹性系数或者减小黏性系数,更容易引发岩体低摩擦滑移。随着冲击扰动、水平拉力幅值的增加,岩块的水平残余位移量值增加,当它们幅值超过一临界值时,岩块发生自持续滑移失稳运动。冲击扰动诱发岩块间不可逆位移、动力滑移失稳的临界能量与剪切力水平密切相关,在较大的剪切内力条件下,极其微弱的动力扰动即可诱发较大的岩块间不可逆位移甚至岩块的动力滑移失稳,随着剪切内力的减小,诱发岩块滑移失稳的能量阈值不断增大,当剪切内力低于岩块动摩擦强度时,单次冲击扰动只能诱发岩块间的不可逆位移。初步开展扰动诱发含初应力紫砂岩块体滑移试验,试验结果与理论计算基本符合,证明该模型的可行性。     

基于GSI值量化和修正方法的岩体力学参数确定

为了准确确定岩体力学参数,通过综合分析多种地质强度指标(GSI)量化方法,提出了一种改进的GSI值量化和修正方法。首先,利用测线法估算结构面平均间距(d)和岩体块度指数(RBI)的改进型岩体块度率(RBR),根据岩体三维结构面网络,获得岩体体积节理数(Jv)和岩体结构等级(SR),然后采用上述参数和结构表面条件(SCR)及结构表面特性参数(Jc)进行了GSI值的定量化处理。为了克服GSI体系的缺点,考虑结构面产状和地下水对岩体力学性质的影响,提出了GSI值的修正方法和公式。以某铅锌矿体的矿岩体为例,根据改进的GSI值量化和修正方法及Hoek-Brown强度准则来确定矿岩体力学参数,通过与原位变形试验的对比分析,验证了该方法的精确性和可行性。该方法为从室内岩石力学试验合理地获取节理岩体力学参数提供了理论及实现的依据。     

鄂西高速公路岩体结构面强度参数试验研究

对湖北省西部某高速公路宜昌—恩施段主要岩体结构面(层面)的抗剪强度参数进行了较系统的试验研究,包括岩体结构面的野外地质调查、岩体结构面原位直剪试验、结构面室内模拟试验及岩体力学参数估值等。通过对各种试验数据进行整理、分析和对比,得到了岩体结构面强度参数。最后在岩体工程分类的基础上,利用Hoek-Brown经验方法对各类岩体结构面强度参数进行了估算。综合以上多种数据,并考虑岩体结构面所处具体地质条件,提出了各类岩体结构面强度参数建议值。     

节理岩体强度特征研究综述

随着岩体工程建设规模的加大,对节理岩体的研究提出了更高的要求,需要对节理岩体强度及其相关问题有全新的认识。在认真总结国内外节理岩体理论与试验研究的基础上,以节理岩体强度为主线,详细论述了理论强度准则、经验强度准则及其与强度有关的节理岩体试验、本构、数值模拟等内容,指出了节理岩体需进一步研究的几个关键问题。      

Capturing the complete stress–strain behaviour of jointed rock using a numerical approach

This paper presents the results of a series of numerical experiments using the synthetic rock mass (SRM) approach to quantify the behaviour of jointed rock masses. Field data from a massive sulphide rock mass, at the Brunswick mine, were used to develop a discrete fracture network (DFN). The constructed DFN model was subsequently subjected to random sampling whereby 40 cubic samples, of height to width ratio of two, and of varying widths (0.05 to 10 m) were isolated. The discrete fracture samples were linked to 3D bonded particle models to generate representative SRM models for each sample size. This approach simulated the jointed rock mass as an assembly of fractures embedded into the rock matrix. The SRM samples were submitted to uniaxial loading, and the complete stress–strain behaviour of each specimen was recorded. This approach provided a way to determine the complex constitutive behaviour of large‐scale rock mass samples. This is often difficult or not possible to achieve in the laboratory. The numerical experiments suggested that higher post‐peak modulus values were obtained for smaller samples and lower values for larger sample sizes. Furthermore, the observed deviation of the recorded post‐peak modulus values decreased with sample size. The ratio of residual strength of rock mass samples per uniaxial compressive strength intact increases moderately with sample size. Consequently, for the investigated massive sulphide rock mass, the pre‐peak and post‐peak representative elemental volume size was found to be the same (7 × 7 × 14 m). Copyright © 2015 John Wiley & Sons, Ltd.     

An anisotropic strength criterion for jointed rock masses and its application in wellbore stability analyses

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.     

节理岩体卸荷强度特性的试验研究

卸荷状态工程岩体的强度特性与传统的加载岩体有本质的区别。目前对于岩石卸荷强度特性的研究比较多见,但对于含节理的岩体在卸荷应力状态下的强度特性,尤其是节理面对其强度的影响研究实属少见。本文通过岩体三轴模拟试验研究了卸荷应力状态下节理岩体的破坏特征,突出考虑了节理面性质对卸荷强度的影响,在此基础上提出了节理岩体卸荷强度准则的一般表达式并进行了对比验证。     

Estimating the Strength of Jointed Rock Masses

Determination of the strength of jointed rock masses is an important and challenging task in rock mechanics and rock engineering. In this article, the existing empirical methods for estimating the unconfined compressive strength of jointed rock masses are reviewed and evaluated, including the jointing index methods, the joint factor methods, and the methods based on rock mass classification. The review shows that different empirical methods may produce very different estimates. Since in many cases, rock quality designation (RQD) is the only information available for describing rock discontinuities, a new empirical relation is developed for estimating rock mass strength based on RQD. The newly developed empirical relation is applied to estimate the unconfined compressive strength of rock masses at six sites and the results are compared with those from the empirical methods based on rock mass classification. The estimated unconfined compressive strength values from the new empirical relation are essentially in the middle of the estimated values from the different empirical methods based on rock mass classification. Similar to the existing empirical methods, the newly developed relation is only approximate and should be used, with care, only for a first estimate of the unconfined compressive strength of rock masses. Recommendations are provided on how to apply the newly developed relation in combination with the existing empirical methods for estimating rock mass strength in practice.     

改进的节理岩体变形模量经验确定方法及其工程应用

在节理岩体工程的数值计算及稳定性评价中,变形特征参数的选择至关重要。在原位试验受到各种条件无法进行时,经验确定方法不失为一种好的选择。本文在大量收集目前国内外节理岩体变形模量经验确定方法的基础之上,提出了改进的节理岩体变形模量经验确定方法,即尺寸效应折减与节理特征折减的二次折减法,并应用3个坝址与水电站的节理岩体工程实例进行分析验证,得出了一些有益的结论。     

Investigation on strength and stability of jointed rock mass using three‐dimensional numerical manifold method

This paper proposes a numerical model for jointed rock masses within the 3‐D numerical manifold method (NMM) framework equipped with a customized contact algorithm. The strength of rock sample containing a few sets of discontinuities is first investigated. The results of models with simple geometries are compared with the available analytical solutions to verify the developed computer code, whereas models with complex geometries are simulated to better understand the fundamental behavior and failure mechanism of jointed rock mass. Furthermore, the stability of jointed rock mass in an underground excavation is studied, where rock failure process is determined by the 3‐D NMM simulation. The simulation results provide valuable guidance on excavation process design and stabilization design in rock engineering practice. Copyright © 2012 John Wiley & Sons, Ltd.     

连通节理岩质边坡稳定性分析

节理岩体的剪切强度由结构面和相邻完整岩块的剪切强度共同决定,当结构面完全连通时,岩体的剪切强度完全由结构面决定。蒙特卡罗法能够根据结构面几何参数模拟岩体结构面的空间分布,通过深度优先搜索算法可搜索到连通的结构面,相对岩体而言,连通的结构面的剪切强度最小,即为节理岩质边坡的潜在滑动面,通过极限平衡法可以对一系列滑面进行稳定性分析。该方法是对节理岩质边坡稳定分析的补充。     

预制节理岩体试件强度及破坏模式的试验研究

采用相似材料模型试验对不同节理倾角、节理贯通度、节理组数、载荷应变率、试件长径比、节理充填物厚度及类型等7种工况下的预制节理岩体在单轴压缩下的峰值强度及破坏模式进行了研究。结果表明：节理岩体的破坏模式及峰值强度与节理构造形态密切相关。贯通节理岩体将产生沿节理面的剪切破坏或穿切节理面破坏,且与第1种破坏模式对应的岩体峰值强度更低。非贯通节理岩体的强度介于完整岩体和贯通节理岩体之间。随着平行节理组数的增加,岩体峰值强度逐渐下降。随着载荷应变率的增加,岩体峰值强度逐渐增大,相应地试件的破坏模式也变得更加复杂。试件长径比基本没有改变其破坏模式,完整试件仍主要是以张拉破坏为主,而节理试件仍以剪切破坏为主。随着长径比增加,试件峰值强度逐渐增大。随着节理充填物厚度增加,试件峰值强度降低。不同节理填充物对试件峰值强度也有一定影响。     

对碎裂结构岩体似连续介质特征的一点研究

通常情况下认为碎裂结构的岩体具有非连续介质的特征。但是随着西部大量水电工程的勘查和建设,遇到了一类比较特殊的岩体,这类岩体中裂隙发育,结构面间距很小,按照国标划分为碎裂结构岩体,但是其本身又具有较高的力学性质,表现为具有较高的变形模量、抗剪强度参数和完整性系数,并且具有似连续介质的特征,这与通常的碎裂结构岩体有本质的区别。本文将利用两个实例工程对这一现象进行初步的分析,得到了水电工程可利用岩体的一种新的评价方法。