测量岩体应力波的压电应力计

本文介绍一种用于岩体爆炸测量的新型压电应力计--RS 型应力计.它利用压电晶体的压电效应直接测量应力。由于外壳采用爆炸现场测点处的岩芯材料制成,避开了应力测量中难以解决的匹配问题.实践表明:只要保证 RS 型应力计按规定工艺要求制作,并进行系统的标定和回填,对中硬和坚硬岩体中自由场和毛洞周边的爆炸应力测量是可行的。     

Influence of an Inclined Rock Stratum on In-Situ Stress State in an Open-Pit Mine

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.     

用于煤层底板突水机理研究的岩体原位测试技术

底板突水是底板受采动应力和承压水水压共同作用的结果。开拓和采动打破了原有地应力的平衡状态,为达到新的平衡,某些应力相对集中的地方,会释放应变能,使岩体构造发生变化;而承压水的水压对底板隔水层的作用主要是压裂扩容作用与渗水软化作用。本文介绍了由岩体原位应力测试技术、室内三轴渗透仪测定技术和计算机有限元模拟技术组成的岩体应力测试综合技术及其在煤层底板突水预测中的应用。      

Investigating the capability of deformation rate analysis method in stress estimation: a case study of water conveyance tunnel of Gotvand Dam

Knowledge of the magnitude and orientation of the initial in situ stress of rock mass in underground spaces in mining, construction, and oil projects are so vital; hence, putting it aside could not only cost a lot rather incur some irrecoverable damage. Various methods are available to estimate in situ stress in rock mass. However, the most commonly used one, i.e., hydraulic fracturing (HF) method is considered expensive and time consuming. As a matter of fact, laboratory methods based on drilled “core” have become prevalent these days considering them simple, cheap, and quick. Taking into account one such procedure, i.e., deformation rate analysis (DRA), the current research tries to review the DRA capability in determining the magnitude of initial in situ stress is in different parts of stress–strain curve. Further, an investigation was made about the usage of DRA method for both brittle and ductile rocks. To compare the DRA and hydraulic fracturing methods in in situ stress measurement, the water conveyance tunnel of Gotvand Dam was selected as a case study. The DRA tests were conducted on core samples prepared from blocks of tuff (as brittle) and soft sandstones (as ductile) from shallow quarry. The results show that the DRA method is suitable for all types of intact rock and that this could easily estimate in situ stress values. A comparison between in situ stress values obtained by DRA and those of HF method show the feasibility of geotechnical project, simplicity, speed, and low cost.     

大埋深高地应力关山隧道围岩变形破坏分析

甘肃省关山隧道是一条受高地应力影响的大埋深硬脆性闪长岩铁路隧道,位于青藏高原东北缘,构造活跃,运动速率较大,且方向变化显著的六盘山挤压隆升构造区。在隧道开挖过程中围岩变形破坏现象明显,围岩等级低于前期岩体质量分级,表现出强烈的岩体质量劣化和各向异性。针对该问题,除了采用矿物成分和微结构分析寻找原因,还通过现场结构面统计分析对围岩质量劣化和各向异性进行描述,同时运用自行研发的钻孔电视进一步分析开挖前后一定时间间隔内围岩的渐进式变形和破坏。钻孔电视试验结果表明,尽管闪长岩作为一种硬脆性岩体,单轴抗压强度（UCS）高于现场地应力值,但其变形和破坏却普遍发生,开挖过程中新生裂隙迅速发育,原先在高地应力下闭合的裂隙也会重新张开和发展,围岩劣化,稳定性降低。为了进一步分析围岩的变形破坏过程,设计了变压力大小和方向的单轴抗压试验,试验中闪长岩的单轴压力值低于单轴抗压强度,试验结果与钻孔电视试验观测结果吻合,证明了在开挖引起的地应力剧烈变化条件下硬脆性闪长岩结构劣化,存在变形破坏的可能性。在大埋深高地应力条件下,除了岩体的各向异性,地应力的变化也是硬脆性围岩稳定性的重要考量因素。     

Approaches to stress monitoring in deep boreholes for future CCS projects

There is no monitoring technology available to observe possible changes of stress in the rock mass of a CO₂ reservoir or its cap rock formations. Any development of a stress-monitoring technique must be related to the natural regional stress conditions and must be adjusted to the possibly changing in situ stress conditions due to CCS activity. As a step towards an in situ stress-monitoring probe, a lab scale device was developed and used for investigations on the practicability of a hard-inclusion tool for stress monitoring. In situ stress conditions, as deduced from the Altmark Gas Field, were applied to evaluate the efficiency and the limits of this stress-monitoring technique. At lab-scale the applied stresses resp. stress differences with moderate amounts of 9?C15?% of the vertical stress component Sv coincide sufficiently with the resulting strain answers of the hard inclusion tool (i.e., a steel tube corresponding to the liner in the borehole). Therefore, it was possible to re-calculate the stresses and to compare them with the applied ones. The resulting coincidence, however, can be disturbed at high pressure levels due to rock failure around the borehole with extended deformations. In addition, the results are influenced by the mechanical behaviour of the surrounding rock mass type. Nevertheless, a further development of a hard inclusion probe for monitoring of stress changes in deep boreholes can be successful and may be the only possible way to detect stress changes without fracturing damages in deep boreholes.     

Microseism Induced by Transient Release of In Situ Stress During Deep Rock Mass Excavation by Blasting

During deep rock mass excavation with the method of drill and blast, accompanying the secession of rock fragments and the formation of a new free surface, in situ stress on this boundary is suddenly released within several milliseconds, which is termed the transient release of in situ stress. In this process, enormous strain energy around the excavation face is instantly released in the form of kinetic energy and it inevitably induces microseismic events in surrounding rock masses. Thus, blasting excavation-induced microseismic vibrations in high-stress rock masses are attributed to the combined action of explosion and the transient release of in situ stress. The intensity of stress release-induced microseisms, which depends mainly on the magnitude of the in situ stress and the dimension of the excavation face, is comparable to that of explosion-induced vibrations. With the methods of time–energy density analysis, amplitude spectrum analysis, and finite impulse response (FIR) digital filter, microseismic vibrations induced by the transient release of in situ stress were identified and separated from recorded microseismic signals during a blast of deep rock masses in the Pubugou Hydropower Station. The results show that the low-frequency component in the microseismic records results mainly from the transient release of in situ stress, while the high-frequency component originates primarily from explosion. In addition, a numerical simulation was conducted to demonstrate the occurrence of microseismic events by the transient release of in situ stress, and the results seem to have confirmed fairly well the separated vibrations from microseismic records.     

电爆冲击波对储层致裂效果影响因素的数值模拟研究

电爆冲击波在油气储层增渗解堵中具有巨大应用潜力,为了解各因素对电爆冲击波致裂效果的影响程度,本文采用ANSYS/LS[CD*2]DYNA软件,通过改变地应力、弹性模量、抗拉强度参数进行数值模拟。结果显示,地应力对致裂效果具有强烈的抑制作用,在双向等压地应力作用下,裂纹区形状为圆形,并且随着地应力的增大,岩体破裂度、破裂半径均逐渐减小。在双向不等压地应力作用下,随水平主应力差值增大,裂纹扩展方向由圆形逐渐转变为椭圆形,具有沿最大水平主应力方向扩展的特点;弹性模量对致裂效果具有重要影响,随着弹性模量的增大,岩体破裂度、破裂半径均呈增大趋势;随抗拉强度增大,岩体破裂度、破裂半径均减小。     

Estimation of the rock mass deformation modulus using a rock classification system

It is often difficult to directly obtain specific design parameters of interest. In these situations, estimation based on empirical correlations is an alternative. The deformation modulus of a rock mass, which is important to know for engineering projects, is measured by in situ tests, such as plate bearing, flat jack, pressure chamber, borehole jacking and dilatometer tests. Nevertheless, these in situ tests are expensive, time consuming and sometimes even impossible. Many attempts have been made to estimate the E modulus using easy-to-obtain parameters of a rock mass. This paper reviews previous studies and the equations that have been developed. In addition, this study presents a new relation developed using a database of 82 dilatometer test results gathered from two dam sites and a tunnel site. Statistical analyses were performed to correlate accessible rock parameters with measured E modulus values from in situ tests. Knowing that discontinuity characteristics and the strength of rock materials are the most important contributors to rock deformability, the focus was on identifying parameters that are affected by the mentioned properties. Among the tested parameters, RMR (Rock Mass Rating) showed the best correlation with the E modulus. Statistical analyses resulted in a new empirical equation that has an acceptable estimation ability.     

In-Situ strain measurement by photoelastic bar gages, 1. The method

A technique is described for measuring recoverable strain in situ using bridged photoelastic bar gages and a simple reflecting polariscope. Rosettes of 0.2 × 0.4 × 4-cm bars are bonded to the rock for 0.6 cm at each end. Change in strain is measured following overcoring with a 10-cm bit. Correction for strains in the order of 30 · 10^?6/°C, due to differential thermal expansion between rock and gage, are made by monitoring dummy gages mounted on free blocks. Bar gages have been satisfactorily tested against foil resistance gages. Rosettes mounted closely adjacent on a free granite block showed a reasonable homogeneity of response.     

我国某地下油库预可行性研究地应力测量及其应用分析

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(S_H,S_h)都远大于对应深度处的垂向应力(S_v),三向主应力的关系为:S_H > S_h > S_v,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。      

地应力与岩体模量关系的理论及试验研究

岩体模量（弹性模量及变形模量）是工程岩体力学特性的基础参数之一,研究地应力状态与岩体模量之间的关系具有重要意义.基于静弹性热力学模型原理,结合弹性理论,推导了水平主应力与岩体性质参数的定量关系,并对地应力与岩体模量的关系进行了探讨.在此基础上,以赣龙铁路梅花山隧道为依托,开展了围岩应力及岩体模量参数的现场测试工作,并将实测成果与理论分析进行对比.结果表明：当埋深影响较小时,花岗岩中的水平主应力与岩体模量呈线性正相关关系;当埋深相差较大时,深度对地应力及岩体模量的影响均不可忽略,水平主应力与岩体模量一般呈非线性关系,需要进一步研究;对花岗岩中的岩体弹性模量和变形模量与水平主应力之间的相关性进行对比发现,岩体变形模量与水平主应力的相关性更好.研究成果可为工程岩体力学参数取值及评价提供借鉴.     

COMPUTATION ANALYSIS OF THE STRESS-WAVE PARAMETER OF ROCK MASS DURING STRIP EXPLOSIVE CHARGE BLASTING

Based on the principles of overlapping stress-wave of all elements charge blasting ,the basic computation graph of stress wave parameter during strip explosive charge blasting was abtained .consequently ,a computation method of open-hole blasting was postulated .combined with in situ data ,a computer program in fortran code was designed and then the calaulation of stress-wave parameter of rock mass during open-hole strip charge blasting was made ;The consistency of computed results with observed data wasfine .The laws of stress-wave propagation and the stress distribution characteristics for open and closed-hole blasting were discussed .The computed data were compared and evaluated with in situ data .these data could be used as a basis of reference in practical engineering .     

条形药包爆炸时岩体中应力波参数的计算分析

水利、铁道、冶金等工业部门,在基坑开挖、隧道掘进,矿山开采等作业中通常用圆柱状条形药包.此外,某些工程如洞库爆炸也可看成条形药包.显然,这类药包在岩体中爆炸时,应力波的传播和动应力的分布均不同于球形药包的爆炸而具有自己的特点.这些特点直接影响爆破破岩机理和对地下工程施加动荷载的特征,以及对它的动态稳定性的评价.     

隧道围岩中全长注浆岩石锚杆的应力分布分析

在弹性状态下,根据锚固体的受力情况建立了锚固体的摩阻力分布模型。根据此模型,结合隧道围岩位移变化函数推导了全长注浆岩石锚杆在围岩变形下的全长受力分布函数。并结合工程实例,分析了锚杆的应力分布特征,得出了注浆岩石锚杆在围岩变形中受力的基本特征。     

Stress‐dependent elastic wave velocity of microfractured sandstone

A model for the stress‐dependent elastic wave velocity response of fractured rock mass is proposed based on experimental evidence of stress‐dependent fracture normal and shear stiffness. Previously proposed models and previous experimental studies on stress‐dependent fracture stiffness have been reviewed to provide a basis for the new model. Most of the existing stress‐dependent elastic wave velocity models are empirical, with model parameters that do not have clear physical meanings. To propose the new model, the rock mass is assumed to have randomly oriented microscopic fractures. In addition, the characteristic length of microfractures is assumed to be sufficiently short compared to the rock mass dimensions. The macroscopic stress‐dependent elastic wave velocity response is assumed to be attributed to the stress dependency of fracture stiffness. The stress‐dependent fracture normal stiffness is defined as a generalized power law function of effective normal stress, which is a modification of the Goodman's model. On the other hand, the stress dependency of fracture shear stiffness is modeled as a linear function of normal stress based on experimental data. Ultrasonic wave velocity responses of a dry core sample of Berea sandstone were tested at effective stresses ranging from 2 to 55 MPa. Visual observation of thin sections obtained from the Berea sandstone confirms that the assumptions made for microstructure of rock mass model are appropriate. It is shown that the model can describe the stress‐dependent ultrasonic wave velocity responses of dry Berea sandstone with a set of reasonable material parameter values. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

非均质共面断续节理岩体拉伸剪切破裂机制研究

工程开挖面附近卸荷扰动区的岩体,受结构面和拉应力共同影响作用,其变形和破坏具有拉剪复合特征。为研究节理岩体的拉剪力学特性,基于颗粒离散元法针对共面断续节理岩体开展了系列数值模拟研究。通过假设粒间接触的力学参数服从Weibull分布表征岩体的非均质性,探讨了非均质性、均质度、法向拉应力和节理连通率对节理岩体拉剪强度和破坏模式的影响。研究表明:拉剪应力条件下非均质性节理岩体主要沿阶梯型破裂面破坏,剪应力-水平位移曲线可以分为线性变形阶段、非线性变形阶段、峰值及峰后阶段;随均质度提高,节理岩体的剪切强度逐渐增加且提升幅度逐渐减弱,趋于均质岩体,岩体中微裂纹由弥散型分布向破裂面集中;节理岩体峰值剪切强度和法向拉应力的大小呈非线性负相关关系;岩体剪切强度随节理连通率增加而显著降低。     

Rock bursting phenomena in a superficial rock mass in southern central Sweden

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     

应变软化模拟与圆形隧道衬砌分析

在岩土工程中,有许多类岩体呈现应变软化特性。在应变软化过程中,如果多个材料强度参数分析发生变化,就很难给出软化问题的解析解。已有的文献研究表明,在经典的弹塑性理论框架下,模拟岩土介质的应变软化过程依然值得深入研究。利用应变软化材料强度参数随塑性应变增加而弱化的特点,提出了将应变软化过程简化为一系列的脆性应力跌落与塑性流动过程的思想,应变软化行为的模拟转化为一系列脆塑性过程的分析。将这种模拟应变软化过程的思想方法用于求解均匀初始应力场中应变软化介质内的圆形隧道开挖问题,研究了衬砌对减少岩土开挖扰动的作用以及考虑应变软化对衬砌内力的影响。数值结果表明,对于应变软化岩土材料,忽略其强度软化的行为是偏于危险的。