巷道围岩应力及力学性质的套筒致裂试验研究

本文介绍了用套筒致裂量测岩体应力及力学性质的方法及量测结果。研究结果表明,岩体的基本参数——主应力的大小和方向、岩体的弹性和刚性,可以用成本低廉的钻孔套筒致裂装置进行量测。用套筒致裂法不仅能测出岩体在弹性阶段的变形特性,而且能测出非弹性阶段的特性,从而可为矿山应力监控方法提供可靠的数据基础。     

地下硐室围岩应力状态及相关参数测量结果的分析与评价

在深埋及压力硐室工程中,采用水压致裂法测定围岩三维应力状态,宜首先判定围岩应力的分布状况。在具有应力松弛圈、应力集中区与不受开挖影响的正常应力分布域情况下,只有分别进行计算分析,才能更为真实地揭示出硐壁围岩的三维应力分布特征。对于确定压力硐室围岩自身承载能力的水力劈裂测试成果,只有结合裂隙性状、岩层结构状况等进行全面分析,才能准确评价围岩的抗载强度。由于在高压力作用下,岩体中存在的软弱结构面有可能被张裂或扩展,从而改变岩层的透水性,因此只有按照工程运行状态下围岩实际承受的压力进行高压压水测试,才能得到岩层透水性的可靠资料。     

地下硐室围岩应力状态及相关参数 测量结果的分析与评价

 在深埋及压力硐室工程中，采用水压致裂法测定围岩三维应力状态，宜首先判定围岩应力的分布状况。在具有应力松弛圈、应力集中区与不受开挖影响的正常应力分布域情况下，只有分别进行计算分析，才能更为真实地揭示出硐壁围岩的三维应力分布特征。对于确定压力硐室围岩自身承载能力的水力劈裂测试成果，只有结合裂隙性状、岩层结构状况等进行全面分析，才能准确评价围岩的抗载强度。由于在高压力作用下，岩体中存在的软弱结构面有可能被张裂或扩展，从而改变岩层的透水性，因此只有按照工程运行状态下围岩实际承受的压力进行高压压水测试，才能得到岩层透水性的可靠资料。     

设集中排水的水工压力隧洞含水围岩弹塑性应力分析

本文依据《水工隧洞设计规范SDB4-84》,将外水压力作场力处理,且注意到水荷载有着荷载历史这一特点,系统地讨论了水工压力隧洞含水围岩渗透水压力分布规律,建水了设集中排水的水工压力隧洞衬砌与围岩在施工期和运行期的弹塑性应力分析方法,给出了相应的解析计算公式。     

水泥砂浆体中三向压力传感器的测量特性

 确定三向压力传感器实测应力与其周围待测介质初始应力的关系是实现其应力测量的必要条件。为了解三向压力传感器在实际应用中的测量特性,利用RMT岩石力学试验系统对自行研发的三向压力传感器进行标定,研究各个传感面的重复性和线性度,得到各个传感面的标定系数。以水泥砂浆为材料,浇筑制成嵌入三向压力传感器的立方体试样(边长：600 mm),并利用自行研制的真三轴试验加载装置,研究重复荷载作用下水泥砂浆体中三向压力传感器实测应力随外部加载应力状态的变化规律。水泥砂浆体的孔隙结构使得三向压力传感器的实测应力存在滞后现象,但在重复荷载作用下,水泥砂浆体中的孔隙结构逐渐被压密,三向压力传感器的实测应力曲线逐渐趋于稳定。静水应力状态加载条件下,三向压力传感器的实测应力与其对应方向的加载应力呈线性相关关系;非静水应力条件下,三向压力传感器的实测应力不仅与其对应方向的加载应力呈线性相关关系,而且与其对应方向的加载应力与其它两个方向的加载应力之差,也成线性相关关系。在此基础之上,提出了用于描述介质初始应力状态对三向压力传感器实测应力影响规律的数学关系。     

煤层底板陷落柱突水模拟及机理分析

岩溶陷落柱是中国北方型石炭二迭系煤田的一种特殊塌陷，广泛分布于20个煤田45个煤矿区，其导致的突水具有隐蔽性、突发性且与岩溶水有天然联系等特点，对煤矿安全生产危害极大。为研究煤层底板陷落柱破坏特征及突水机理，采用FLAC^3D模拟分析了陷落柱影响下采面推进过程的不同阶段。数值模拟及实验显示，由于陷落柱的面积有限，矿压和水压力联合作用下使其发生弯曲并形成拉张破坏的可能性较小，一般产生剪切破坏，虽然升、降错动产生的剪应力、上凸弯曲产生的拉应力和压应力的三重作用导致煤层底板岩层失稳破坏，但以剪应力作用为主：同时，陷落柱的存在改变了煤层底板的地质环境和岩体结构，底板有效隔水层厚度减小，岩体强度降低，应力．应变分布不均，局部应力集中系数增大，使关键层的最小主应力进一步降低，一旦承压水压力大于关键层的最小主应力，承压水的渗水软化和压裂扩容即起作用，使底板岩层破坏裂隙沿最薄弱方向进一步扩展，导致裂隙贯通，最终形成管涌，发生突水。特别是，陷落柱的边壁、工作面底板压缩区与膨胀区的分界线重合在一条线上时，是底板岩层发生剪切破坏的最佳状态，最容易发生底臌突水。     

高压引水隧洞陡倾角断层岩体高压压水试验研究

结合一抽水蓄能电站高压岔管区高压压水试验,详细介绍了具有陡倾角断层岩体的高压压水试验方法及试验成果。探讨了岩体高压下水力劈裂区扩展的波动理论和渗透破坏特性,明确了岩体与土体渗透破坏形式差异。试验首次对岩体内的渗透压力和变形进行了同步测量,以了解高压条件下岩体的渗透变形特性。在高孔隙压力作用下,岩体的变形发展试验成果表明,岩体应力和稳定性分析过程中孔隙压力的作用不可忽视,因此采用耦合理论对高孔隙压力环境下的工程岩体进行分析有助于降低围岩失效风险。     

Mining-induced stress change and consequences of stress path on excavation stability — a case study

For stability assessments as well as for support design, it is important to understand the factors leading to detrimental stress changes. Stress changes not only influence the demand on the rock support, they also change the support capacity of frictional support components such as plain cablebolts. Stress and stress changes are commonly predicted by numerical models but it is rarely possible to verify these predictions. This study presents a practical example illustrating the usefulness of stress change measurements in providing an accurate picture of the mining-induced stress changes and their value for numerical model calibration. Stress changes, associated with mining of the 565#6 stope at Winston Lake Mine, were measured by four CSIRO HI stress cells, two in the hangingwall and two in the back of a sill drift. In order to obtain the full stress history of the hangingwall, stresses at the installation time were calculated by use of a three-dimensional boundary element program — MAP3D. Two types of rockmass failure were observed at this mine: hangingwall delamination and collapse leading to ore dilution, and wedge-like failures in the backs of sill drifts. All stress cells were located such that they were affected by these failure mechanisms. Using measured and predicted stress paths, this study explains the nature of these two failure modes, as experienced at Winston Lake Mine. Excellent correspondence between measured and predicted stresses is achieved for both the hangingwall and the back of the sill drifts. Modelled stress rotations in the hangingwall follow closely the stress rotations determined in the field, except at the end of the monitoring campaign when the stress cells were affected by inelastic straining of the host rock. These measurements assist in understanding the failure processes and in defining the limitations of the adopted numerical models.     

深部隧洞裂隙围岩渗透特性及衬砌外水压力变化规律

高外水压岩是影响隧道开挖过岩围岩稳定及衬砌结构安全的关键因素之一,基于裂隙介质渗流经典理论,给出围岩、衬砌不同渗透系数下的外水压岩解析解,采用数值方法对隧洞二次衬砌后的外水压岩作用特性进行仿真模拟,探讨裂隙围岩岩衬砌渗透系数对渗流场的影响,围岩、衬砌渗透和排水措施岩外水压岩的相关性。研究表明岩体和衬砌渗透系数之比是影响衬砌外水压岩的关键,正确的灌浆、排水设计对外水压岩折减系数影响较大,是减小衬砌外水压岩的有效措施。结论对高压水作用下裂隙岩体渗流及衬砌外水压岩研究具有重要理论意义,对高水压下围岩注浆及衬砌结构材料选型、参数选择等具有重要岩岩实用价值。     

坚硬顶板水压致裂控制理论与成套技术

煤矿坚硬顶板具有硬度大、整体性好、分层厚度大等特点,导致诸多围岩控制与安全难题。水压致裂可改造顶板岩体结构,控制工作面顶板的冒落;提出坚硬顶板水压致裂控制的理论与成套技术框架。采用真三轴实验系统等研究揭示水压裂缝的扁椭球体典型形态和空间转向扩展形态,给出围压主应力差、排量、层面与原生裂隙等对水压裂缝扩展的影响规律,考虑围岩的应力应变状态与控顶效果,阐明定向压裂临空坚硬悬顶的断顶线位置适当内错煤柱的原理。给出采动岩体水压致裂的时空关系及确定方法。针对裂缝形态的控制要求,提出定向水力割缝致裂等系统的控制致裂方法,在此基础上研制煤矿井下高压(60 MPa)水压致裂的成套装备。针对不同类型工程特点,控制水压主裂缝扩展、翼型裂纹扩展和吸水湿润作用,使顶板及时充分冒落,实现围岩弱化、应力转移、诱导矿压破煤等功能。研发了工作面端头悬顶、切眼及中部坚硬顶板、坚硬顶煤弱化、综放面初采瓦斯、临空巷道冲击地压和大变形等控制成套工艺技术。成套技术与装备已在大同矿区、神东矿区等推广应用。与传统爆破弱化顶板相比,水压致裂弱化顶板管理简单、扰动小、安全性高、工程量少、作用范围大、控制距离远,且经济成本不到其1/10,在深部开采中更具有优势。     

新型引水式电站中水压致裂地应力测量技术应用研究

在中国西南某新型引水式水电站工程中使用水压致裂技术开展了原地应力及相关岩体力学参数测试。结果表明,工程区现今应力场状态以NNW向挤压为主,最大主应力值为7.35～8.16 MPa,方向约为N33～52°W,倾角约26～39°。气垫调压室三维原地应力状态的最大主应力值为10.63 MPa,最小主应力为4.98 MPa;围岩岩体抗劈裂强度高值区在5.50 MPa以上,低值区为3.00～3.50 MPa。根据围岩应力分布非均匀性遵循的一般性规律,结合原地应力测量与裂隙围岩原地承载能力测试结果的各自特点,提出了利用地应力测量数据、原地承载力测试结果、弹性模量数据综合评估承压洞室围岩最小主应力的方法,给出气垫式调压室部位最小主应力综合评估值2.86 MPa。并分析了地应力状态对地下厂房、引水隧洞、气垫调压室稳定性的影响。     

天荒坪抽水蓄能电站岔管区域高压渗透试验

天荒坪高压渗透试验旨在揭示高压岔管所在岩体在高内水压力作用下的稳定和渗透性，以论证可否建造高压钢筋混凝土岔管，并为设计提供允许水力坡降、渗水量、地应力参数及为工程措施提供依据。３只试验孔的试验结果表明，岔管区域总体上环境地应力足够高，但是，２＃岔管附近存在地应力低、渗水量大的局部岩体，需采取工程措施加以改善     

秦岭北缘某深埋引水隧洞应力场特征研究

岩体初始地应力场是研究地下洞室围岩稳定状况和隧洞选线的重要依据。应用水压致裂法对秦岭北缘某深埋引水隧洞应力进行测定,结果显示隧洞围岩应力等级属于中低～高应力水平,应力量值呈σ_H＞σ_h＞σ_z特征,最大水平主应力方向为近NE向,与区域构造主压应力方位接近一致。基于实测数据,对工程区应力场进行回归反演,并结合区域构造应力对隧道沿线的深埋和浅埋段应力场分布规律进行了研究,以期为引水工程的设计和施工提供参考。     

An overview of rock stress measurement methods

This paper presents an overview of methods that have been used to estimate the state of stress in rock masses, with the emphasis on methods applicable to hard rocks and Scandinavia. Rock stress is a difficult quantity to estimate because the rock stress measuring techniques consist of perturbing the rock, measuring displacements or hydraulic parameters, and converting the measured quantities into rock stresses. There are two main types of method: those that disturb the in situ rock conditions, i.e. by inducing strains, deformations or crack opening pressures; and those that are based on observation of rock behaviour without any major influence from the measuring method. The most common methods are briefly described including their application areas and limiting factors.     

A laboratory study of stress arching around an inclusion due to pore pressure changes

When the pore pressure in a porous rock changes, stress arching will occur within the rock and the surrounding region. Stress arching ratio is defined as the total stress changes in the porous rock to the pore pressure change in the region. The region may have the same or different elastic moduli with the surrounding rock, which is usually referred to as inclusion or inhomogeneity. Stress arching is responsible for many geomechanical problems encountered during production or injection; in addition, it is a crucial parameter in stress estimation during field development. This paper aims to present laboratory measurements of vertical stress arching ratio in a material surrounding the inclusion (inhomogeneity). To the authors' knowledge, few laboratory experiments have been reported on direct measurement of stress arching. The inclusion is a cylindrical sandstone (44 mm in diameter and 50 mm in height) embedded in a larger cylindrical sandstone (150 mm in diameter and 154 mm in height), both of which are made synthetically. These two parts are separated and sealed by a internal polyurethane sleeve. Vertical stress changes are recorded by a mini hydraulic sensor embedded in surrounding rock. Laboratory results are compared to those obtained by numerical models. These models are checked with analytical formulations. The results of numerical models show a good agreement with laboratory data. The numerical results also indicate that the sensor response is affected by elastic properties of the internal sleeve. According to the sensitivity analysis performed, in the absence of the internal sleeve, properties of the inclusion have significant effects on the surrounding stress arching induced.     

地球物理场中煤层气渗流控制方程及其数值解

 为探索地球物理场中原地煤层气运移能力对煤层气储集和富集能力的影响,以地应力场、地温场中煤层气连续性方程、气体状态方程、吸附方程、渗流方程为基础,建立了应力、温度影响下的煤层气渗流控制方程。方程体现了地应力和地温对煤层气压力、含量、渗透率和孔隙率的影响,其中,应力和温度通过影响煤层气压力影响吸附量,通过影响煤层气压力和孔隙率影响游离量;温度还通过影响吸附常数b影响吸附量;不同的应力、温度组合条件下,渗透率的变化机制不同。通过Kaiser声发射原岩应力测试实验、不同温度下煤的甲烷等温吸附实验、不同温度及有效应力下煤体中甲烷渗流实验以及煤的孔隙率、工业分析等实验,研究应力、温度影响下的煤层气渗流特征。不同温度下煤的甲烷等温吸附实验表明,吸附常数a随温度变化不明显,b随温度升高而下降;不同温度、不同有效应力条件下煤的甲烷渗流实验表明,小有效应力条件下,煤体中甲烷渗透率随温度升高而升高;大有效应力条件下,渗透率随温度升高而下降。以实验数据和原始地质资料为基础,采用有限差分法,进行了地球物理场中原地煤层气渗流运移能力的一维、二维数值模拟。计算表明：研究区现今原地煤层气渗流运移导致的煤层气散失甚微,低渗煤层具有良好的储集和富集能力,但不利于后期开采,卸除地应力和升高温度是提高煤层气抽采率的有效途径。     

Hydromechanical interactions in a fractured carbonate reservoir inferred from hydraulic and mechanical measurements

Hydromechanical coupled processes in a shallow fractured carbonate reservoir rock were investigated through field experiments coupled with analytical and numerical analyses. The experiments consist of hydraulic loading/unloading of a water reservoir in which fluid flow occurs mainly inside a heterogeneous fracture network made up of vertical faults and bedding planes. Hydromechanical response of the reservoir was measured using six pressure–normal displacement sensors located on discontinuities and two surface tiltmeters. A dual hydraulic behavior was characterized for low-permeability bedding planes well connected to high-permeability faults. Displacement responses show high-variability, nonlinear changes, sometimes with high-frequency oscillations, and a large scattering of magnitudes. Initial normal stiffnesses and effective normal stresses along fault planes were estimated in the field by interpreting pressure–normal displacement relations with a nonlinear function between effective normal stress and normal displacement. Two-dimensional discontinuum modeling with transient fluid flow was performed to fit measurements during hydraulic loading tests. Results show that the hydromechanical behavior of the reservoir is restored if a high stiffness contrast is allocated between low- and high-permeability discontinuities. Thus, a dual-permeability network of discontinuities will likely also be a contrasting stiffness network, in which the deformation of major flow-conducting discontinuities is significantly influenced by the stiffness of the surrounding less-permeable discontinuities.     

Rôle des fluides dans le comportement hydromécanique des roches fracturées hétérogènes: Caractérisation in situ et modélisation numérique

Hydromechanical coupled processes in a shallow fractured rock mass were investigated in situ through field experiments and numerical simulations. The experimental approach consists of performing simultaneous and multi-frequency measurements of fluid pressures and displacements at different points and on different fracture types within a carbonate reservoir. Two kinds of experiments were conducted at the Coaraze Laboratory Site (France):

1. At the fracture network scale, a global hydraulic loading by groundwater level change shows that the coupling between fluid flow and deformation is simultaneously governed by a dual-permeability hydraulic behaviour and a dual-stiffness mechanical behaviour. The following fluid flow and hydromechanical conceptual scheme was established: first, a transient flow only occurs in faults with high permeability; second, when a steady-state flow is reached in faults, water flows from faults into lower permeability bedding planes. The intact rock matrix is practically impervious but the connectivity between the discontinuities is high. When fluid pressure changes occur within the fracture network, the hydromechanical coupling is direct in the highly permeable faults where a pressure change induces a deformation change. No direct hydromechanical coupling occurs within the lower permeability zones where deformation is not directly correlated with pressure changes. This means that the mechanical deformation of the bedding planes and rock matrix is induced by the fault deformation.
2. At the single fracture scale, the hydromechanical behaviour was evaluated by performing hydraulic pulse injection testing. This test was monitored using high-frequency (f = 120 Hz) hydromechanical measurements conducted with innovative fiber-optic borehole equipment. The hydromechanical response is simultaneously monitored at two measuring points spaced about 1 m apart within the plane of the sub-vertical fracture. Observed fluid pressure versus normal displacement curves shows a characteristic loop-shaped evolution in which the paths for loading (pressure increase) and unloading (pressure decrease) are different. The test was evaluated by coupled hydromechanical modelling using a distinct element technique. By matching the loop behaviour, modelling indicates that the pulse pressure increase portion allows the fracture hydromechanical properties to be determined while the pulse pressure decrease portion is strongly influenced by the hydromechanical effects within the surrounding fractured rock mass. A sensitivity study shows that the key parameters to coupled hydromechanical processes in such fracture systems are the initial hydraulic aperture and normal stiffness of the fracture, the stiffness of the rock matrix and the geometry of the surrounding fracture network.

     

不同场热-水-应力耦合过程二维有限元分析

从建立应力平衡方程、水连续性方程、能量守恒方程和弹塑性矩阵入手,提出了一个饱和-非饱和孔隙介质中的热-水-应力耦合模型和开发了相应的有限元程序.为验证本耦合模型及程序的可靠性和重点探讨不同场的热-水-应力耦合过程,以高放射性核废料地质处置的Prototype Repository Project(PRP)原位试验为模拟对象,对一个处置试验坑道近场进行了水单场、热-水耦合、水-应力耦合、热-应力耦合和热-水-应力耦合条件下的数值分析,考察了工程屏障及围岩中的温度、饱和度及应力的变化、分布情况,并得出了一定的认识.     

Empfehlung Nr. 10 des Arbeitskreises 3.3 “Versuchstechnik Fels” der Deutschen Gesellschaft für Geotechnik e. V.: Indirekter Zugversuch an Gesteinsproben – Spaltzugversuch

Indirect tensile test of rock samples – splitting tensile test. The Commission on Rock Testing of the Deutsche Gesellschaft für Geotechnik e. V. (German Geotechnical Society) is compiling suggestions for rock testing in laboratory and in‐situ and for performing monitoring of rock masses and civil engineering structures. The revised version of recommendation No. 10 deals with the splitting tensile test (Brazilian Test) on rock samples and incorporates for the recent developments of testing machines and testing procedures since the first version from 1985. The requirements for the testing machines and specimens are given as well as the procedures to perform the test and to evaluate the data. Essential modifications regard the definition of standard testing layouts for splitting tensile tests on anisotropic rock samples. The splitting tensile strength of a rock sample is determined in an indirect tensile test. A cylindrical shaped specimen is loaded by linear distributed loads until failure. The tensile strength is determined on the basis of the elasticity theory.