地下洞室开挖爆破围岩松动圈的数值分析计算

根据数值计算提出了在地下洞室开挖爆破中,确定围岩松动圈的方法。给出了地下洞室开挖爆破的三维弹塑性损伤有限元计算方法。该方法论述了爆破荷载、重力荷载和开挖荷载的计算、施加以及迭代的方法,可以合理反应爆破对围岩稳定的影响和锚固支护施加的效果;结合岩石松动圈的实测方法,推导了判定围岩开始松动的损伤系数阈值公式,可以结合数值计算得到的洞周围岩损伤系数分布,确定在开挖爆破作用下围岩松动圈的范围。对实际工程的分析计算表明,根据数值计算判定的围岩松动范围与实测松动范围的规律基本一致,量值吻合较好,其结果为地下洞室开挖爆破的围岩松动圈的确定提供了有效的方法。     

The influence of an excavation damaged zone on the thermal-mechanical and hydro-mechanical behaviors of an underground excavation

In Korea, a reference disposal system, KRS, was proposed in 2006 after 10 years of research and development. In the KRS, the high-level radioactive waste repository is considered to be located in a crystalline rock likes granite. For a validation of the feasibility, safety, and stability of the KRS, an underground research tunnel, KURT was constructed in Nov. 2006. During the construction of KURT by a controlled blasting, the size and characteristics of an excavation damaged zone(EDZ) were investigated by in situ as well as laboratory tests. The possible influences of an EDZ around a tunnel on the thermal, hydraulic and mechanical behaviors of the near field were investigated by using hydro-mechanical and thermo-mechanical coupling analyses. From this study, it was found that the existence of an EDZ can influence the thermal, hydraulic, and mechanical behaviors of the near field and it was recommended that an EDZ should be considered as an important parameter during the design of underground repositories.     

深埋隧洞爆破开挖荷载诱发围岩损伤特性

深埋隧洞爆破开挖荷载构成复杂,对围岩损伤区的孕育发展具有重要影响。利用颗粒流程序（PFC）软件,讨论了不同初始地应力状态下爆炸荷载及地应力瞬态卸载所分别诱发围岩损伤的特性,并通过锦屏2级水电站引水隧洞爆破开挖损伤区检测数据对数值模拟的结果进行了验证。研究表明,爆炸荷载和地应力瞬态卸载所诱发的围岩损伤程度和范围均随地应力量级的提高而显著增大;爆炸荷载作用条件下损伤区的分布有随着侧压力系数的增大而向应力集中区发展的趋势,而地应力瞬态卸荷所产生的围岩破坏以受拉破坏为主,表层损伤区沿开挖呈轮廓均匀分布的趋势;在相同的初始地应力状态下,爆炸荷载和地应力瞬态卸荷所分别诱发的围岩损伤区深度均明显小于实测值,考虑二者的耦合效应后,计算值与实测值基本吻合。这说明这两种荷载是高应力条件下爆破开挖荷载的主要成分,但二者耦合作用对围岩的损伤大于它们单独作用效应的线性叠加。     

基于量纲分析的巷道围岩松动圈预测模型

为更合理地确定巷道围岩松动圈厚度,引入量纲分析理论,提出新的巷道围岩松动圈预测方法。选取岩石单轴抗压强度Rc、围岩节理系数F、围岩重度?、巷道埋深H、最大水平主应力?Hmax、巷道跨度B等物理量,应用量纲分析法构建巷道围岩松动圈厚度L与上述物理量间的无量纲关系式,其中L/H表征松动圈厚度L与巷道埋深H成正比,F表征巷道围岩的结构特征,?H/Rc、?Hmax/Rc 表征巷道围岩的力学特征,B/H表征巷道的几何特征。结合实测数据,推导了各无量纲量间的定量函数表达式,残差平方和为0.003 1,相关系数为0.937 9。选取3个矿山巷道围岩松动圈测试实例对所建立的松动圈预测模型进行验证,结果表明该方法计算结果与实测结果较吻合,平均相对误差为7.38%,能满足工程需要。     

Characterising and modelling the excavation damaged zone in crystalline rock in the context of radioactive waste disposal

This paper describes current knowledge about the nature of and potential for thermo–hydro–mechanical–chemical modelling of the excavation damaged zone (EDZ) around the excavations for an underground radioactive waste repository. In the first part of the paper, the disturbances associated with excavation are explained, together with reviews of Workshops that have been held on the subject. In the second part of the paper, the results of a DECOVALEX [DEmonstration of COupled models and their VALidation against EXperiment: research funded by an international consortium of radioactive waste regulators and implementers (http://www.decovalex.com)] research programme on modelling the EDZ are presented. Four research teams used four different models to simulate the complete stress–strain curve for Avro granite from the Swedish Äspö Hard Rock Laboratory. Subsequent research extended the work to computer simulation of the evolution of the repository using a ‘wall-block model’ and a ‘near-field model’. This included assessing the evolution of stress, failure and permeability and time-dependent effects during repository evolution. As discussed, all the computer models are well suited to sensitivity studies for evaluating the influence of their respective supporting parameters on the complete stress–strain curve for rock and for modelling the EDZ.     

高地应力条件下大型地下厂房松动区变化规律及参数反演

松动区是控制地下洞室围岩变形及失稳的重要因素。以锦屏一级水电站为例,结合声波测试及多点位移计监测成果,对高地应力和低强度应力比条件下大型地下厂房围岩松动区的分布及变化特征进行分析,并采用BP网络和遗传算法对围岩参数进行反演。研究表明,声波测试的围岩松弛深度与多点位移计监测得到的围岩主要变形深度具有一致性,围岩松弛深度变化趋势与岩壁位移变化也存在对应关系,两者结合可以对围岩松动区的变化规律进行连续的分析。高地应力和低强度应力比条件下的松动区深度远大于一般应力条件,由于围岩应力状态调整、岩体破坏所导致的卸荷松弛成为围岩松弛的主要因素。开挖过程中,由于围岩应力状态的逐步调整,导致围岩的破坏和松弛的渐进发展,其中松弛深度在水平向的扩展较为明显。反演得到的松动区岩体变形模量及黏聚力较未松动岩体有明显降低,而摩擦角降低较少。因此,对松动区岩体进行灌浆加固,将有助于提高松动区岩体的变形模量和粘聚力,从而增强围岩的稳定性。     

A method for assessment of excavation damaged zone (EDZ) of a rock mass and its application to a dam foundation case

Excavation of slope is an unloading process, and also an energy releasing process when the stress in the rock mass is unloaded, leading to the rebounding deformation towards the free face. And then a zone, namely excavation damaged zone (EDZ), will be formed near the excavation boundary, where the rock is damaged or disturbed and its physical, mechanical and hydraulic properties are greatly changed. This paper is to put forward a new method to quantify the extent and damage degree of the EDZ according to the unloading strain energy which is released in the process of excavation. A simple relationship between unloading strain ε and accumulative opening displacement T of cracks, , is proposed to describe the damage degree of rock mass in the EDZ, where h is the depth variable in normal direction of the open cracks.This method is used to assess the EDZ of the dam foundation at Xiaowan hydropower station in southwestern China by the accumulative opening displacement curves of cracks along boreholes based on boreholes camera photos. We find that the EDZ can be naturally divided into two sub-zones, i.e. the excavation heavily disturbed sub-zone (EHDZ) and excavation slightly disturbed sub-zone (ESDZ), according to the variation of unloading strain ε. Two inflexions of the accumulative opening displacement curve indicate the lower limits of EHDZ and ESDZ respectively.     

Study of the initiation and propagation of excavation damaged zones around openings in argillaceous rock

The study of the creation and evolution of the excavation disturbed zone (EDZ) in argillaceous rocks is a major issue for the safety of nuclear wastes underground repositories. In this context, the argillaceous Tournemire site has provided a unique opportunity to study the evolution of the EDZ with time thanks to the existence of three openings of different ages. A thorough characterization of the EDZ has been conducted by different means such as visual observation, analysis of samples extracted from drilled boreholes, EDZ permeability measurements, etc. On the basis of these measurements, a conceptual model of the EDZ initiation and propagation at the Tournemire site has been proposed. In order to validate this model, numerical simulations of increasing complexity have been carried out. In a first attempt, the response of the rock mass to the excavation phase, followed by seasonal cyclic variations of temperature and relative humidity inside the opening, has been simulated by means of a purely mechanical analysis, using a simple elastic material model. The EDZ has been estimated by post-processing the calculated stress states, using a Mohr–Coulomb failure criterion. The results obtained show that no EDZ could be predicted unless adopting a low cohesion value for the rock mass. Moreover, the deferred nature of the EDZ formation in Tournemire could not be reproduced. These limitations have then been suppressed by using a coupled viscoplastic-damaging mechanical model, the parameters of which have been identified from different laboratory experiments. With this model, a time evolution of the EDZ could be predicted, but the EDZ pattern could not match the one observed in situ. Finally, in view of the importance of the hydraulic couplings, unsaturated hydro-mechanical calculations have been carried out to investigate the effect of the numerous seasonal variations cycles and the resulting shrinkage.     

深埋隧洞开挖损伤区的检测及特征分析

隧洞开挖以后围岩会出现损伤,并在洞周形成开挖损伤区,在损伤区范围内声波波速会出现衰减。针对锦屏二级水电站3#引水隧洞在隧道掘进机（TBM）开挖过程中可能形成的损伤区,首先利用数值方法探讨了损伤区的分布特征,通过监测特征点在开挖过程中的应力路径,确定了特征点的应力状态和可能出现声波波速衰减的部位。在此基础上确定了对声波钻孔的布置方案,并利用单孔声波检测方法确定了损伤区深度。为了实现颗粒流程序PFC对损伤区的模拟,通过三轴压缩试验确定了PFC的细观参数。最后利用PFC描述了损伤区的分布,分析了损伤局部化特征和损伤程度的变化。结果表明PFC的模拟结果和检测结果具有较好的一致性,能够实现对损伤区特征的准确描述。研究成果对损伤区的检测和支护优化设计具有指导意义。     

黏性土包气带中流体迁移规律

以黏土模拟低渗透包气带环境,探究了混溶流体在包气带中的迁移规律。实验结果表明:混溶流体在横向和垂向的最大迁移距离与流体泄漏量均符合幂函数变化规律y=axb。随着流体注入体积的增加,横向和垂向迁移距离不断增大,迁移速率逐渐减小。文章提出以横纵比作为反映流体在包气带中迁移变化规律的重要指标。横纵比总体呈下降趋势,具体分为两个阶段:流体注入体积为0~3 046 m L时,横纵比呈先上升后稳定的趋势,横纵比大于1。此阶段流体以横向发育为主,污染羽剖面呈扁平状椭圆;当流体注入体积大于3 046 m L,横纵比逐渐减小到1以下并持续减小。此阶段流体以垂向发育为主,污染羽剖面逐渐转变为竖直长条状椭圆。     

边坡开挖卸荷松弛区的力学性质研究

开挖卸荷松弛区对边坡稳定性分析与防护加固工程设计具有重要的作用和影响,重点体现在松弛区的分布特征及松弛岩土的强度衰减效应。基于典型边坡的开挖模拟,研究其最大主应力增量及塑性区力学特征与分布规律,结果表明:边坡开挖应力调整引起的最大主应力增量的负值区与坡面塑性区的分布形态与发展规律吻合;基于边坡开挖卸荷松弛的基本力学原理,以开挖边坡应力张量增量的最大主应力分量增减变化作为开挖卸荷松弛区的划分标准,提出了接近开挖坡面的应力衰减塑性松驰区、远离开挖坡面的原岩应力区及介于两者之间的应力集聚弹性挤压区的三场确定方法。     

初始地应力对隧洞开挖爆生裂隙区的影响研究

隧洞开挖过程中控制爆炸对岩体的损伤,减小爆破裂隙范围,对保证工程安全具有重要意义。基于爆炸应力波作用下爆生裂隙形成机制的研究,采用摩尔-库仑准则及最大拉应力准则,研究了初始地应力对爆炸应力波作用下爆生裂隙区比例半径的影响。研究结果表明,初始地应力对爆生裂隙范围有显著影响。在压剪破坏模式下,爆生裂隙区比例半径随地应力的增大而减小,地应力侧压系数影响爆生裂隙区比例半径在洞壁圆周的分布。考虑围岩应力卸荷影响后,沿隧洞径向的爆生裂隙区比例半径比不考虑卸荷的小。拉伸破坏导致的岩体爆生裂隙区比例半径一般比压剪破坏模式下爆生裂隙比例小,爆炸应力波作用下隧洞围岩更容易沿结构弱面发生压剪破坏。     

柱状节理开挖模拟洞数值原位试验

在西南水电大开发中,柱状节理岩体的工程力学性质逐渐受到水利工程的重视。白鹤滩水电站坝基揭露的柱状节理玄武岩体,RQD值普遍较低,完整性较差,其变形模量等力学指标相对较低,表现出显著的各向异性特征,对拱坝变形、坝肩稳定、边坡稳定、地下洞室群围岩稳定有重要影响,已成为该水电工程的关键技术问题之一。针对国内外对柱状节理岩体的研究及相关工程的经验甚少,白鹤滩水电站拟开展的大尺度柱状节理玄武岩试验洞,目的是获得反映柱状节理玄武岩力学特性的第一手观测资料。介绍了白鹤滩柱状节理的地质成因和工程特性及柱状节理试验洞的设计布置,探讨了原位试验和数值试验结合的分析方法,并采用各向异性本构模拟了试验洞开挖和原位试验,对不同位置试验点的代表性进行了评价。     

Lateral bearing performance and mechanism of piles in the transition zone due to pit-in-pit excavation

Acta Geotechnica - Excavation types of foundation pits for large-scale or special-purpose urban construction have been more and more complex, and the environmental safety issues caused by pit...     

高应变法在人工挖孔嵌岩桩检测中的应用

通过高应变法在人工挖孔嵌岩桩检测中的应用,说明在充分考虑嵌岩桩工作机理的前提下,进行嵌岩桩承载力分析、动静对比以及与《规范》计算结果的比较,应用高应变法检测人工挖孔嵌岩桩的承载力是可行的、也是可靠的,并且所测得的桩身上部桩土阻力和嵌岩段侧阻力是准确的,完全可以满足工程设计和施工要求。     

Contact zone permeability at intrusion boundaries: new results from hydraulic testing and geophysical logging in the Newark Rift Basin, New York, USA

Hydraulic tests and geophysical logging performed in the Palisades sill and the underlying sedimentary rocks in the NE part of the Newark Rift Basin, New York, USA, confirm that the particular transmissive zones are localized within the dolerite-sedimentary rock contact zone and within a narrow interval below this contact zone that is characterized by the occurrence of small layers of chilled dolerite. Transmissivity values determined from fluid injection, aquifer testing, and flowmeter measurements generally fall in the range of 8.1E-08 to 9.95E-06 m²/s and correspond to various scales of investigation. The analysis of acoustic and optical BHTV images reveals two primary fracture sets within the dolerite and the sedimentary rocks—subhorizontal fractures, intersected by subvertical ones. Despite being highly fractured either with subhorizontal, subvertical or both fracture populations, the dolerite above and the sedimentary rocks below the contact zone and the zone with the layers of chilled dolerite are significantly less conductive. The distribution of the particular conductive intervals is not a function of the two dominant fracture populations or their density but rather of the intrusion path of the sill. The intrusion caused thermal fracturing and cracking of both formations, resulting in higher permeability along the contact zone.     

A rock mass permeability model within the subsidence zone in workings of coal fields

Based on mining works near water objects, a model of water permeability in an underworked site of a coalfield under the conditions of failure roof control is given. The secondary water permeability index varies in the section as a sawtooth function and depends on the strain intensity and lithology of rock beds. The coefficient of permeability reaches maximum values in intervals of split crack propagation, sandstones, limestones increasing towards the subfaces of beds, as well as towards the mined-out area in the lower part of the zone of water-conducting subsidence cracks. The coefficient of permeability in siltstone and mudstone beds normal to beds inside the upper and central parts of zones of water-conducting subsidence cracks is at a level of 0.003 m/day.     

Temporal change in permeability of the Nojima fault zone by repeated water injection experiments

Three boreholes were drilled near the Nojima fault, which the 1995 Hyogoken–Nanbu earthquake occurred on. In order to research the properties and the healing process of the fault, water injection experiments were conducted every 3 years. In this report, we researched the permeability of the fault as a measurement of crack density or porosity of the fault zone. Pore water pressure changes in rock due to the water injections at one borehole were observed as discharge changes or groundwater level changes at the other borehole. Using numerical calculations, the permeability of the fault fracture zone was estimated for each experiment. The permeability has been decreasing as time passed, which is thought to show the fault healing process of the Nojima fault after the 1995 Hyogoken–Nanbu earthquake.     

开挖扰动下地下交叉洞室错动带岩体微震演化规律

错动带具有“历史上多次剪切错动、延伸范围广、遇水易软化、力学强度低”的软弱特性,致使其在开挖卸荷作用下极易诱发不同程度的变形和破坏,进而严重影响地下洞室的稳定性。针对白鹤滩水电站右岸9#母线洞（地下交叉洞室）发生的错动带岩体塌方破坏,借助高精度、实时微震监测系统,系统地研究了塌方孕育过程中的微震活动性,包括微震事件时空演化规律、震级和视应力分布特征。采用矩张量理论,反演塌方孕育过程中的微震事件破裂机制（张拉、剪切或混合）,归纳、总结其演化过程为：表层围岩卸荷张拉破裂→裂纹渐进向围岩深部扩展→破裂沿错动带方向萌生、扩展（张拉破裂为主,伴随剪切或混合破裂）→裂缝与错动带交汇,切割出不稳定楔形体→爆破振动或重力作用下,错动带岩体塌方。该研究结果可为高应力地下交叉洞室错动带岩体的开挖、支护提供参考,同时对类似工程的施工具有重要借鉴意义。     

北山坑探设施开挖损伤区现场声发射监测试验研究

为研究爆破开挖对围岩的损伤,在高放废物地质处置地下设施(北山坑探设施)开展了开挖损伤区(EDZ)的研究。对多个爆破回次开挖全过程进行了声发射监测试验,根据声发射撞击数演化特征,将爆破开挖围岩的损伤过程分为爆破损伤段和渐进损伤段,分析了声发射信号频率演化规律。根据两阶段信号参数特征分析了对应阶段微破裂机制,通过高频探地雷达圈定了开挖损伤区范围,发现各回次开挖损伤区的厚度与声发射撞击数具有较好的相关关系,并分析了室内及现场试验岩石(体)的"蠕变"特征与声发射演化规律。分析认为,爆破后声发射演化特征是围岩渐进损伤过程的直接体现,渐进损伤在位移上表现为"蠕变"特征,声发射能有效地表征围岩的变形过程及其所处的损伤状态。研究成果对声发射现场应用表征围岩的损伤状态具有一定参考价值。