深部高应力巷道锚网喷U型钢联合支护技术

随着矿井开采深度的增加,巷道受高地应力及强烈开采扰动的影响愈加明显,深部高应力巷道的支护难度逐渐增大。以某矿深部巷道支护工程为例,采用了锚网喷U型钢联合支护方案,基于FLAC3D数值模拟软件,分析了巷道围岩变形规律,对支护方案进行可行性分析。工业性试验围岩变形监测结果表明,15 d～90 d的围岩变形位移增量小于总位移增量的10%,30 d后的围岩变形基本收敛,表明采用锚网喷U型钢联合支护技术,可有效控制深部巷道的大变形。     

地应力对深部回采巷道布置方向的影响分析

为分析地应力对深部回采巷道布置方向的影响,在参考相关文献和实测淮南矿区7个深部矿井20组地应力的基础上,获得高水平构造应力赋存特征。针对某深部矿井首采面两回采巷道布置方位与最大水平应力一致时,断面收缩仍然严重,对比Tresca理论与Gale理论,确定前者更适合分析此类巷道变形破坏状态。按点的应力状态计算不同侧压下巷道最优布置方位与最大水平主应力夹角β,得到首采面两巷的β为45°。根据巷道帮、顶应力差值越大围岩稳定性越差,进一步探究了β从0°偏转为12°,其围岩变形的应力差影响程度降至91%。接替面工程实践表明:初期支护方案相同时巷道围岩变形略有改善,后期支护方案改为帮、顶角增加两根锚索外加信号柱及时补强后支护效果良好,研究结果为类似条件下巷道布置与围岩控制提供了一定参考。     

葛泉矿软岩大巷底鼓机理及控制研究

-190南翼运输大巷底鼓一直是困扰葛泉煤矿的重大问题。以该巷道大范围内的岩体为研究对象,通过对围岩主要物理和力学性质的室内测试、底鼓影响因素的理论分析和支护效果的数值模拟,掌握了原支护条件下巷道围岩塑性区范围和巷道周边应力分布状况,得出围岩性质、水和支护形式是产生底鼓的主要因素,提出了底鼓控制途径和全断面注浆、帮角锚杆加固控制底鼓的方案,并通过数值模拟优化了支护参数。现场观测表明,该方案取得了良好的底鼓控制效果。     

深部巷道围岩承载结构的数值分析

围岩承载结构的稳定是深部巷道支护成功的关键。应用岩石峰后应变软化本构模型对深部巷道进行数值模拟研究,分析了深部巷道与浅部巷道围岩承载结构的差别,探讨了支护阻力对深部巷道围岩承载结构的影响。研究结果表明:深部巷道围岩中存在围岩强度强、弱软化区域交替出现的现象;而提高支护阻力可以缩小围岩强度软化区域范围,减小围岩强度软化程度,改善巷道围岩应力分布状况。得出了支护阻力通过控制围岩强度软化,提高围岩自承能力,实现深部巷道围岩承载结构稳定的目的的结论。     

基于地应力实测的深部软岩巷道稳定性研究

唐口煤矿埋深较大,地压显现剧烈,在回风石门大巷、西翼辅助运输石门等不同构造部位布置3 个地应力测点,采用YH3B-3型环氧树脂三轴空心包体应变计按应力解除法进行了现场地应力的测试,获得了矿井地应力的大小、方向及分布规律。采用FLAC 3D 研究巷道轴向与水平构造应力呈不同夹角时对深部软岩巷道围岩稳定性的影响,为巷道的合理布置与支护设计提供了可靠依据;当最大水平应力方向与巷道轴向近似平行时,巷道围岩的变形量和塑性区范围较小,巷道变形破坏相对较小;当最大水平应力方向与巷道轴向垂直时,巷道围岩的变形量和塑性区范围最大,巷道变形剧烈、变形破坏严重。     

高地应力深部巷道开挖锚固特性的三维地质力学模型试验研究

为研究锚固支护条件下深部巷道围岩是否产生分区破裂以及岩锚支护对分区破裂的影响,以淮南矿区丁集煤矿深部巷道为工程背景,进行了锚固支护条件下高地应力深部巷道开挖三维地质力学模型试验。通过模型试验发现围岩应变呈现波浪形变化规律以及洞周锚杆受力出现拉压交替变化现象。通过与未加锚支护模型试验结果的对比,揭示锚杆对抑制巷道围岩分区破裂具有重要的作用,这为深入分析深部巷道开挖锚固特性和优化深部巷道支护设计奠定了坚实的试验基础。     

深井大断面动压回采巷道锚网支护技术研究

随着开采强度的加大,平煤股份所属的主力矿井多数已进入800m以上的深部开采,巷道处于高应力环境中,中等强度锚网支护的回采巷道变形量大,稳定所需时间长,返修率高。结合平煤股份十一矿丁5-6-26071风巷的工程地质条件,采用数值模拟技术研究了高强锚杆锚索协调支护巷道在不同动压作用下的矿压显现特征:掘巷阶段,支护方式完全能够满足要求;在受到超前支承压力的初期阶段,仍然能够满足需要;但在超前支承压力的峰值阶段,锚杆锚索滑脱,底臌严重,两帮内挤,需要采取加强支护措施。工业性试验表明:掘巷阶段巷道表面位移、深部位移及支护受力均在合理的范围之内,巷道断面收缩率为最大为12.4%,满足使用要求。     

深部厚顶煤巷道让压型锚索箱梁支护系统现场试验对比研究

针对巨野矿区深部高地应力厚顶煤巷道支护特点,以“先抗后让再抗”支护理念为指导,研制高强让压型锚索箱梁(PRABB)支护系统。该系统具有预紧力损失小、定量让压、支护力传递效果好、护表面积大等特点。分别以箱型支护梁和矿用12#工字钢为托梁设计了横梁、纵向单梁和纵向双梁共6种支护系统。以赵楼煤矿深部厚顶煤巷道为工程背景,利用数值试验对其支护效果进行初步分析,并在3302工作面顺槽进行6种支护系统的现场试验对比研究。现场试验结果表明：(1) 相对于原支护方案,6种锚索梁支护系统均能有效控制巷道围岩变形;(2) PRABB支护系统试验段巷道支护效果整体优于工字钢锚索梁方案,前者围岩变形量比后者小15%～25%;(3) 纵向单梁支护系统对巷道围岩的控制效果最好,纵向双梁支护系统次之,横梁支护系统相对较差。根据试验结果对钢梁不同布置方式的围岩控制机制进行分析表明：纵向单梁支护系统可有效控制厚顶煤巷道顶板关键部位的变形,调动围岩自承能力,使巷道变形得到较好控制。在深部厚顶煤巷道支护时,采用PRABB支护系统纵向单梁方案,可达到经济有效控制巷道围岩变形的目的。     

深部软岩巷道支护设计优化与监测分析

针对深部软岩巷道复杂地质条件设计出曲墙拱断面锚喷支护的设计方案,利用锚杆测力计MJ-40对支护后的锚杆受力进行受力监测,利用全站仪对巷道围岩表面位移进行变形监测,监测结果证明巷道的设计有效减小了大断层复杂地质条件下构造应力的影响,巷道支护方案安全可靠。     

金川矿山深部采掘条件下岩石力学研究与实践

 金川矿山经过几十年开采,开采深度已达1 000 m,复杂的工程地质条件、高地应力以及高渗透压导致深部开采工程的稳定性问题愈加突出。对金川二矿区深部850～1 000 m水平进行大量的现场地质调查研究,测试深部典型岩石的物理力学参数、膨胀与软化特性,研究岩石力学性质和地应力随埋深的变化规律。采用岩体地质力学(RMR)分类法和岩体质量(Q值)分类法,绘制二矿区深部各分段水平的岩体质量分区图。在深入调查金川矿区深部巷道变形和破坏特征的基础上,对高地应力、高渗透压下深部巷道开挖支护稳定性进行研究,结果表明,U型钢和锚杆联合支护效果最佳。全面总结金川矿区深部巷道支护经验,对巷道掘进和支护技术提出几点新的想法。研究不同开采方式对金川矿区深部充填体和围岩稳定性的影响,优化矿体回采方式,建议采用“隔三采一”布置回采进路,有助于控制围岩的变形,减弱上部充填体的下沉。     

深埋巷道的选型分析

深部岩体的力学特性不同于浅部岩体的力学特性,深埋巷道的结构形式是否合理对结构的承载能力和经济效果有很大影响。运用有限元方法,对五心拱、三心拱、1/2圆拱、圆拱、1/3圆拱和1/4圆拱模型的深埋单轨和双轨巷道在不同应力情况下进行数值计算,分析巷道周围的应力场和塑性区。计算结果表明,单轨巷道宜采用1/4圆拱模型,双轨巷道宜采用1/4圆拱或三心拱模型。     

Rock mechanics contributions to recent hydroelectric developments in China

Rock mechanics plays a critical role in the design and construction of hydroelectric projects including large caverns under high in situ stress, deep tunnels with overburden more than 2500 m, and excavated rock slopes of 700 m in height. For this, this paper conducts a review on the rock mechanics contributions to recent hydroelectric developments in China. It includes the development of new testing facilities,mechanical models, recognition methods for mechanical parameters of rock masses, design flowchart and modeling approaches, cracking-restraint method, governing flowchart of rock engineering risk factors enabling the development of risk-reduced design and risk-reduced construction, and initial and dynamic design methods. As an example, the optimal design of underground powerhouses at the Baihetan hydroelectric plant, China, is given. This includes determination of in situ stresses, prediction of deformation and failure depth of surrounding rock masses, development of the optimal excavation scheme and support design. In situ monitoring results of the displacements and excavation damaged zones(EDZs) have verified the rationality of the design methodology.     

深埋特长公路隧道岩爆预测综合研究

岩爆预测一直是地下工程世界性难题之一。以台缙高速公路苍岭隧道的岩爆预测为例,从隧道区围岩的岩体特征和隧道区初始应力场两方面着手,通过工程地质调查研究和区域地质资料分析,对隧道区进行工程地质分类。划分隧道沿线各洞段隧道围岩类别,通过室内岩石力学试验,掌握隧道沿线围岩的物理力学特性;分析区域地震震源机制解、地应力实测资料,揭示区域构造地应力场环境。在研究过程中选取典型部位,采用水压致裂法实测工程区地应力的大小和方向。通过三维有限元反演工程区的初始应力场,在初始应力场和隧道围岩岩石力学性质研究的基础上,结合各洞段隧道断面开挖数值分析结果和现有国内外多种岩爆判别准则,对苍岭隧道岩爆发生的部位和等级进行预测,为制定合理的开挖支护方案提供依据。     

Study of multiple draw-zone interaction in block caving mines by means of a large 3D physical model

Current production level design guidelines in block caving mines are based on the concept of interaction of movement zones and the spacing of draw-points at which mass flow is achieved. The limit of the isolated movement zone (IMZ) interaction has been determined by observations of the flow of sand and finely fragmented caved rock. This paper presents a study of the mechanisms and limit of IMZ interaction in coarse fragmented caved rock using a large 3D physical model. Results showed that when drawing from multiple draw-points, the unmoved zone between IMZs is characterised by an increase in vertical load and a decrease in horizontal load. However, it was observed that the unmoved zones between the movement zones of adjacent draw-points did not enter the flow zone, despite draw-points being spaced at less than 1.2 times the width of the IMZ. This result is in marked contrast to previous findings obtained in sand models, where movement zones have been observed to interact at draw-point spacings up to 1.5 times the width of the IMZ. The major reasons for the differences between the two different model results was found to be that significant stress arching and less induced vertical stress during flow was observed in the gravel model, in contrast to limited stress arching and more induced vertical stress in the sand models. It is hypothesised that significant stress arching would occur in block caving mines, and therefore that the results obtained in the gravel model maybe more representative of full-scale conditions. Movement zones in block caving mines may therefore not interact at draw-point spacings greater than the width of the isolated movement zone.     

A strain-softening numerical model of core discing and damage

There has been a debate in the rock mechanics community regarding the mechanisms causing what is known as core discing. This phenomenon occurs when diamond drill cores are retrieved from rock masses in which high in situ stresses relative to rock strength are present. The interest in that phenomenon is to use it to estimate the in situ stresses from the shape and frequency of the failures along the core axis. In the present paper we argue that discing is only an indicator of high stresses, and that estimating in situ stresses from fracture observations is much too inaccurate.As most of the literature found on the subject has tackled the problem using elastic numerical models, it is shown that the stress distribution in the core being formed obtained from such models does not exist once failure has been reached. Numerical analyses using Flac^2D with an elasto-plastic cohesion softening friction hardening model show that for a given stress state, discing or core damage may involve tensile failure, a combination of shear and tensile failure, or only shear failure, depending on the stress state and ratio of tensile to shear strength of the rock. The numerical model used is validated by replicating core discing observed under controlled laboratory conditions. Parametric analyses involving changes in mesh density, deformability parameters, dilatancy, drill bit pressure, drilling fluid pressure and applied stress states are also performed. Finally, it is shown that drilling-induced core discing or damage store important residual stresses in the core which may explain why recovered core samples tend to show a deterioration of their mechanical properties with time.     

岩石边坡潜在失稳区域微震识别方法

 为深入研究锦屏一级水电站左岸边坡深部岩体微震活动规律并评价边坡稳定性,在已有微震监测资料基础上,结合常规监测数据,并借助RFPA有限元数值模拟手段,分析左岸边坡深部岩体微破裂萌生、发育和扩展的演化机制,解释高程1 829 m处2#固结灌浆平洞多点位移计变化与微震事件时空分布规律之间的内在联系,再现典型剖面边坡渐进破坏全过程,重点阐述高程1 885 m坝顶平台裂缝形成机制。综合施工工况和工程地质情况分析,表明微震监测系统可以有效地识别和圈定边坡深部岩体微破裂区域和潜在滑裂面,边坡外观变形及微震活动性与该部位地质构造及灌浆活动有密切关系,灌浆导致的应力重分布和边坡内部天然裂隙带错动变形是诱发高程1 885 m坝顶平台裂缝的主要原因。研究结果为更好地理解和分析复杂应力条件下岩石边坡变形及其微震活动性诱发失稳机制提供重要的参考。     

Anisotropy of strength and deformability of fractured rocks

Anisotropy of the strength and deformation behaviors of fractured rock masses is a crucial issue for design and stability assessments of rock engineering structures, due mainly to the non-uniform and non- regular geometries of the fracture systems. However, no adequate efforts have been made to study this issue due to the current practical impossibility of laboratory tests with samples of large volumes con- taining many fractures, and the difficulty for controlling reliable initial and boundary conditions for large-scale in situ tests. Therefore, a reliable numerical predicting approach for evaluating anisotropy of fractured rock masses is needed. The objective of this study is to systematically investigate anisotropy of strength and deformability of fractured rocks, which has not been conducted in the past, using a nu- merical modeling method. A series of realistic two-dimensional （2D） discrete fracture network （DFN） models were established based on site investigation data, which were then loaded in different directions, using the code UDEC of discrete element method （DEM）, with changing confining pressures. Numerical results show that strength envelopes and elastic deformability parameters of tested numerical models are significantly anisotropic, and vary with changing axial loading and confining pressures. The results indicate that for design and safety assessments of rock engineering projects, the directional variations of strength and deformability of the fractured rock mass concerned must be treated properly with respect to the directions of in situ stresses. Traditional practice for simply positioning axial orientation of tunnels in association with principal stress directions only may not be adequate for safety requirements. Outstanding issues of the present study and su~zestions for future study are also oresented.     

Bolt length requirement in underground openings

A parametric study has been carried out using the numerical analysis code FLAC^3D to obtain the influence of various shapes of underground openings on the maximum induced boundary stress. Five shapes—viz. circular, horseshoe, rectangular, elongated D-shape and elliptical—have been considered. For each shape, four tunnel depths and five horizontal in situ stress models have been taken for the study of induced boundary stresses.The values of maximum and minimum induced boundary stresses in the roof and wall have been obtained from the analyses. This data has subsequently been used to develop correlations to estimate the normalized maximum and minimum boundary stresses, which have been subsequently compared with the strength of the rock mass obtained from the Sheorey's non-linear failure criterion for three rock masses represented by three values of Bieniawski's RMR and three values of crushing strength of intact rock material. The values of minimum factor of safety at the roof and the wall have been collected from all the plots. Using these data sets, different correlations have been developed to estimate the minimum factor of safety (f_min) in the roof and wall.Since the bolt length should be normalized with the opening size, some more computer models have been run with varying tunnel width of 5 and 20 m besides the earlier 10 m size to obtain the correlations for estimating the bolt length. The depth of factor of safety contour of 1.5 from the opening periphery has been picked up from all these models and the correlations have been developed for estimating the roof and wall bolt length for the five shapes of underground openings. The correlations for bolt length show that in addition to the shape of underground openings and in situ stress, the bolt length also varies with the rock mass type. These correlations have been verified for field cases of elongated D-shape openings.     

某发电厂景观烟囱的风载体型系数研究

基于Fluent软件,采用标准k-ε模型、修正的k-ε模型和雷诺应力方程模型(RSM)对某发电厂景观烟囱的风载体型系数进行了数值模拟。研究了两种网格密度、三种湍流模型、五种风向角下烟囱各区域的整体体型系数和典型测点体型系数分布,比较了光滑模型和实际模型的体型系数差异。分析表明,RSM模型能获得与我国荷载规范最为接近的结果,验证了数值模拟的可行性;装饰条的设置推后了实际模型圆型截面的分离并改变了背风面的流场,从而极大地增大了其整体体型系数,降低了体型系数的负峰值。最后给出了各区域的顺风向整体体型系数取值和测点层体型系数的极值点,为该烟囱的设计提供了参考。     

非协调变形下深部岩体破坏的非欧模型

 将岩体看成不含原生宏观裂隙而仅含原生微裂纹的颗粒材料。在开挖卸荷过程中,原生微裂纹启裂、扩展并穿过岩石基质,产生次生裂纹。此时,岩体出现非连续和非协调变形,经典的弹塑性力学理论不再适用于研究岩体的非连续和非协调变形情况。基于自由能密度、平衡方程和变形非协调条件,提出一种新的非欧模型,确定微裂纹半长度和密度对标量曲率和自平衡应力的影响,获得深部圆形洞室围岩应力场,它包括弹性应力和自平衡应力。由于自平衡应力的影响,当微裂纹的密度和半长度较大时,深部圆形洞室围岩的应力场具有明显的振荡特性。但是,当微裂纹的密度和半长度较小时,深部圆形洞室围岩的应力场振荡特性不明显。对于位于波峰附近的微裂纹,其尖端的应力集中将导致次生裂纹的失稳扩展、连接、合并成宏观裂隙,形成破裂区;而对于位于波谷附近的微裂纹,其尖端应力集中不足以导致次生裂纹发生失稳扩展,因此出现非破裂区。深部圆形洞室围岩应力场交替出现波峰和波谷现象导致破裂区和非破裂区的交替出现,即分区破裂化现象。通过数值模拟,详细研究微裂纹半长度和密度对深部岩体分区破裂化现象的影响。