Zonal disintegration mechanism of the microcrack-weakened surrounding rock mass in deep circular tunnels

Rock masses without pre-existing macrocracks are considered as granular materials with only microcracks. During excavation of tunnels, microcracks may nucleate, grow and propagate through rock matrix; secondary microcracks may appear, and discontinuous and incompatible deformation of rock masses may occur. The classical continuum elastoplastic theory is not suitable for analyzing discontinuous and incompatible deformation of rock masses any more. In this paper, a new non-Euclidean model is established to investigate zonal disintegration mechanism of the surrounding rock masses around a deep circular tunnel. Effect of damage variable on the zonal disintegration under non-hydrostatic stress condition is taken into account. Based on non-Euclidean model of the discontinuous and incompatible deformation of rock mass, the effect of the half length and density of microcracks on distribution of stresses in the surrounding rock masses around a deep circular tunnel is investigated. The stress concentration at the tips of microcracks located in vicinity of stress wave crest is comparatively large, which may lead to the unstable growth and coalescence of secondary microcracks, and consequently the occurrence of fractured zones. On the other hand, the stress concentration at the tips of microcracks located around stress wave trough is relatively small, which may lead to arrest of microcracks, and thus the non-fractured zones. The alternative appearance of stress wave crest and stress trough thus may induce the alternative occurrence of fractured and non-fractured zones in deep rock masses.     

深部巷道破坏分区破裂规律三维相似材料实验

为了探究不同应力状态下巷道围岩的分区破裂规律、影响因素,选择沙土材料为相似材料进行三维模拟实验。试验采用3种加载方式：双向加载、 “圆筒模型加载”和真三轴加载,分别模拟不同采深时围岩的应力状态,巷道的断面形状分别选取了圆形、方形。模型试验研究表明：分区破裂属于空间剪切带破坏,平行于硐室轴线方向应力较大(约是材料抗压强度的1.6倍以上)是形成分区破裂的重要条件。影响分区破裂的因素有围压的大小与分布,开挖巷道所在岩层的相邻岩层性质。围压大且均匀,分区破裂范围大,围压较小且不均匀,分区破裂不明显。层与层之间材料不同时,会影响到裂纹的扩展。而硐室形状对分区破裂的影响因素较小。圆形、方形硐室周围都出现了分区破裂现象。     

内摩擦角对逐步开挖拱形巷道围岩分区破裂化的影响

巷道围岩分区破裂化(或分区破碎化、分区碎裂化)是指在深部开挖巷道时围岩交替呈现破裂区和未破裂区的现象,该现象与对围岩破坏的传统认识不同。正确认识不同强度围岩分区破裂化的发育程度,可为其治理及应用奠定基础。巷道掘进会引起掘进工作面附近岩石涌向巷道,这将导致掘进工作面附近垂直于巷道轴线平面的应力状态并非平面应变,而是三维状态。采用以FLAC~(3D)应变软化模型为基础发展的非均质应变软化模型(通过引入Weibull分布函数实现),研究了内摩擦角对逐步开挖拱形巷道围岩分区破裂化的影响,考察了围岩中剪切应变增量、最小主应力及最大主应力在巷道即将贯穿模型时的分布规律。研究发现:①内摩擦角越小,围岩的破坏越严重,剪切带的发育越充分,分区破裂化越明显;②并非围岩的破坏就会导致分区破裂化,围岩破坏到一定程度后,才会出现分区破裂化;③分区破裂化的机理为:在载荷及开挖作用下,在过巷道轴线的平面上,随机分布的缺陷发展成(共轭)剪切带,从而在垂直于巷道轴线的平面上,形成多个相间隔的圆环形的破坏区。本文过巷道轴线平面上的结果与室内实验结果在定性上一致。根据本文的研究,在垂直于巷道轴线的不同平面上,分区破裂化不同,这意味着不必选择统一的巷道支护参数,例如,在分区破裂化显著的部位,延长锚杆的长度,反之则不然。     

The non-Euclidean model of failure of the deep rock masses under the deformation incompatibilty condition

The deep rock masses are considered as granular materials containing uniform distribution of defects. Defects in the deep rock masses are characterized by the damage variable. The damage variable of the deep rock masses is determined using Mori-Tanaka’s method and Sidoroff’s method, which consider the interaction among microcracks. Effect of the pre-existing microcracks and secondary microcracks on scalar curvature and the free energy density is investigated. A new non-Euclidean mode is established, considering effect of the pre-existing microcracks and secondary microcracks. Contributions of pre-existing microcracks and secondary microcracks to the self-equilibrated stresses are derived from the free energy and the deformation incompatibilty condition. The stress fields of the surrounding rock masses around a deep circular tunnel are determined from a new non-Euclidean model.     

Strain Gradient Model of Zonal Disintegration of Rock Mass near Deep-Level Tunnels

This paper presents one strain gradient model of zonal disintegration of rock mass near deep level tunnel. The governing equations and boundary conditions of the model are established. Numerical methods (quasi-Newton method and shooting method) are adopted to solve the obtained fourth-order equilibrium equations with higher order boundary conditions in terms of displacement. The stress field in elastic and plastic zones is obtained. The effects of model parameters on stresses distribution in surrounding the tunnel rock mass are examined. The necessary conditions for the formation of zonal disintegration are elucidated.     

深部隧硐锚杆支护结构系统中锚杆受力研究

依据柏格斯（Burgers）模型，对深部围岩隧硐进行了应力与位移场的解析分析研究，建立了柏格斯模型下隧硐围岩的位移方程、应力方程；基于载荷传递机理，建立了锚杆受力的微分方程，通过求解锚杆受力的微分方程得到了锚杆与围岩相互作用下的轴向载荷分布函数。然后对锚杆的轴向受力与摩阻力进行了计算分析，通过结果分析得出：粘弹性围岩中的应力分布与时间无关；隧硐围岩中任一点的位移随时间而增长，同时，随着时间将趋向于一定值；锚杆的受力符合中性点理论。同时，通过分析深部围岩隧硐发生破坏的原因，建立支护结构与围岩共同作用的特性曲线，提出了一种符合NATM核心思想的，能够科学确定支护结构最佳架设或安装施工时间的新思路。     

深部围岩分区破裂化模型试验研究

为研究深部巷道围岩破裂机理,在"深部巷道围岩破裂机理与支护技术模拟试验装置"进行了模型试验,系统研究了深部巷道围岩在最大初始开洞荷载与洞室轴线平行作用下直墙拱顶试验的破坏形态和机理。模型试验表明:当最大主应力与洞室轴线平行,在较大轴向压力作用下产生较大的朝洞内的膨胀变形,使得在围岩内产生较大的径向拉应变,其产生的拉伸断裂是出现分层破坏现象的关键,分布特点是随着轴向应力的增加其拉应变值增加,随距洞壁距离的增大其拉应变值减小。拉伸断裂面形成后,相当于在原来的介质内又形成了一个新的半径增大的洞室,洞室在较大的轴向压应力持续作用下,拉伸破坏过程不断重复出现,就会形成交替的破裂区域和未破裂区域,即分层破裂现象。     

深部巷道围岩分区破裂化弹塑脆性分析

考虑围岩在空间轴对称受力状态下弹性、塑性、脆性状态的转化,提出了深部围岩分区破裂化现象是围岩在特定条件下拉伸破坏与脆性张裂破坏不断重复的结果。分析了巷道围岩的弹塑性应力场,说明了支撑压力线处的环状连续拉伸破坏是分区碎裂化产生的必要条件,并给出了拉伸破坏处的半径公式。结合Griffith强度准则,推导了围岩由弹性状态转化为脆性张裂破坏的半径关系式,以此来确定破裂区范围。实例计算结果表明,破裂带的宽度和位置都与现场实际观测结果吻合较好。     

深部洞室围岩分区破裂化的研究现状与分析

深部岩体工程在开挖洞室或巷道时,围岩的变形和破坏出现了一系列新的科学特征现象,如岩爆和围岩分区破裂化。其中,深部巷道围岩的分区破裂化现象与浅埋地下巷道开挖时在其洞周出现破裂区、塑性区和未扰动弹性区依次排列的现象有很大不同,这引起了国际上岩石力学工程领域专家学者的极大关注。本文根据国内外对分区破裂化研究现状,分析总结了分区破裂化现象的研究成果,并对该领域的研究方向进行了探讨。     

节理岩巷应力分布规律与失稳机制研究

为研究具有层状特征的节理岩巷应力分布规律与变形机制及控制对策,通过将巷道直墙拱形断面等效为圆形断面,分析层状节理岩巷应力分布和应力集中影响,并以云南某矿埋深为750 m的阶段运输巷道为研究对象,通过现场调查和Phase 2数值模拟等方法,分析了巷道变形机制并给出了相应的支护对策.结果表明:通过粒子群算法得出的巷道应力集...     

Model of the effects of an explosion in a well

Conclusions A new model of explosions in wells was proposed on the basis of the "inverse" (in terms of the factor of rock pressure) zonal disintegration of rocks around underground workings (Discovery No. 400) and the anomalously low friction in block media detected experimentally by the authors in an investigation of pendulum-type waves. Considerable weight was given to the empirical finding that for certain energies of shock loading of models of block media, friction "vanishes" between interacting blocks of geologic materials in directions orthogonal to the line of action of the external impulse. The geometric parameters of the quasi-cylindrical system of blocks formed around an exploded well are determined by the scale factor of the zonal disintegration process, this factor being linked to the radius of the well; the dynamic—kinematic characteristics of geologic blocks capable of moving along the annular "inverse" disintegration zones are determined by the type of stress state of the surrounding rock masses. Institute of Mining, Siberian Branch of the Russian Academy of Sciences, Novosibirsk. Translated from Fiziko—Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 37–46, March–April, 1997.     

A continuum grain-interface-matrix model for slabbing and zonal disintegration of the circular tunnel surrounding rock

It is difficult to numerically reproduce the common failure modes of the circular tunnel surrounding rocks, such as the slabbing or delamination in hard rock, and the zonal disintegration at great depth, based on continuum and homogeneous elastoplastic models. In the present paper, a grain-interfacematrix model is proposed based on continuum elastoplastic theories, and implemented in FLAC. Rock is simplified as a compound of the circular grains, rectangular interfaces, and remaining matrix. These components are modeled by squared elements with the same size. Results show that shear strains exhibit intersecting and multiple shear bands or slip lines extending intergranularly. High principal stresses in compression are found to form rings around the tunnel surface. For fine grains, the intensive rings are found, similar to the slabbing; while for coarse grains, the spacing between rings becomes large, analogous to the zonal disintegration. Thus, a unified mechanism of two kinds of phenomena is explained as the self-organization process of dominant microstructures subjected to forces. Nevertheless, the scale of dominant microstructures regarding or governing the process is different. For hard rock without joints, the scale corresponds to actual grains; while for jointed rock mass under high compressive stresses at great depth, the scale of rock blocks is dominant.     

深部煤巷围岩变形与控制机理的数值模拟分析

 摘要：为解决深部煤巷支护难题,应用FLAC数值模拟程序研究了深部煤巷围岩变形全过程、地应力对巷道变形的影响和巷道变形控制机制。得出了围岩开挖变形应力场、位移场和塑性区变化规律,地应力对巷道变形的影响规律以及深部煤巷围岩变形控制的内在机制。结果表明：随着开采深度的加大,巷道变形对地应力的敏感度增强;底板是巷道整体稳定的关键,底板变形加剧两帮及其它部位的变形;巷道底板控制应当从围岩整体相互作用的角度实现变形控制。     

深井煤巷钻孔卸压技术的数值模拟与工业试验

结合工程实例，利用数值模拟方法研究了钻孔卸压的作用机理、巷道围岩动态损伤破坏发展和应力场重新分布的过程.模拟发现：合理布置的卸压孔可以导致巷帮围岩的结构性预裂破坏，从而使围岩高应力向深部转移；在卸压孔和锚网联合支护后改善了围岩附近的应力环境，改变了围岩破坏的时空次序，对控制围岩变形和破坏具有突出的优越性.     

高水平应力巷道连续“双壳”治理底臌实验研究

基于深井工程软岩巷道严重底臌这一状况,以河北陶二煤矿扩大区北大巷条件为工程背景,对连续"双壳"如何有效控制深井软岩巷道底臌进行了实验研究。通过现场地应力测量、解算,确定了巷道围岩应力状态,采用自行设计的双向加载试验台,进行深井软岩巷道不同侧压系数时底板围岩变形失稳特征的相似模拟实验,得到底板位移场变化规律及围岩应力分布状态。模拟实验结果表明:底板连续"双壳"加固巷道底臌量较原支护巷道平均减小53%;底板浅孔注浆(浅部壳体)提高岩体承载能力,深孔锚索束注浆(深部壳体)扩大岩体承载范围,浅深壳体共同承载、协同变形有效控制了底板围岩稳定。最后揭示了连续"双壳"治理底臌机理。     

青海能源鱼卡一井流变应力恢复法地应力测试研究

青海能源鱼卡一井是目前世界上海拔最高的大型煤矿,受多期区域构造运动的影响,围岩软弱破碎,导致巷道支护问题愈发突出.为了对鱼卡一井巷道开挖支护进行科学合理设计,需要掌握巷道围岩赋存的地应力特征.基于深部破碎软弱围岩的流变应力恢复法地应力测试技术,在鱼卡一井+2750 m西翼机轨合一大巷开展了现场地应力测试.测试结果表明:...     

水平应力对巷道围岩稳定性的影响

采用理论分析方法研究了巷道布置与地应力场的关系,利用数值模拟方法分析了不同巷道轴线与最大水平主应力夹角的情况下,巷道围岩应力分布与变形特征。指出随着夹角增大,水平应力分布从对称变为非对称,应力降低区与升高区也发生变化;当夹角增大到一定值,非对称性逐渐降低,到90°时又出现了对称分布;巷道变形在夹角20～70°变化明显。在山西潞安常村煤矿井下进行了地应力测量,分析了地应力对巷道变形与破坏状况的影响,验证了理论分析与数值模拟结果。     

煤矿TBM掘进巷道围岩时效变形分析及支护参数优化研究

针对煤矿TBM掘进巷道围岩长期稳定性问题,以淮南矿区张集矿TBM掘进某瓦斯抽采巷为工程背景,开展了巷道围岩时效变形分析及支护参数优化研究。通过在TBM掘进巷道施工现场钻取砂质泥岩岩样,开展蠕变试验,获得CVISC蠕变参数|在数值模拟软件中引入CVISC蠕变模型,对不同支护工况下TBM掘进巷道围岩进行为期100d的蠕变变形模拟,获得各支护工况下巷道围岩时效变形特征和应力场及塑性分布区的演化规律|基于数值模拟结果,将优化后的锚杆+钢筋网联合支护体系应用于TBM施工巷道,并对TBM施工巷道进行围岩变形监测和锚杆轴力监测,现场实测结果表明采用的优化支护方案可有效控制围岩变形,且巷道稳定性较好。     

白音呼布矿区三维地应力测量及巷道布置优化研究

白音呼布矿区进入深部开采后,巷道岩爆、变形等地压灾害变得愈发严重。为保障生产安全,现场采用空心包体应力解除法测量了对矿区7个测点三维地应力,基于测量结果及地应力场构建对矿区深部巷道布置优化进行了研究。首先根据等应力轴比理论优化了巷道布置方向,给出了100m中段巷道轴向与最大水平主应力方向最优夹角为26°;然后采用数值模拟方法研究不同夹角时巷道围岩的应力、位移变化特征,并指导了新中段的巷道布置。结果表明:实测最大水平主应力是自重应力的1.57～1.89倍,矿区深部以水平构造应力为主导;夹角为26°时,巷道围岩变形最小,数值模拟与理论计算结果相符;新中段巷道优化布置后,围岩变形、位移明显变小,地压灾害得到有效控制。