Numerical analysis of deformation and failure characteristics of deep roadway surrounding rock under static-dynamic coupling stress

In actual production,deep coal mine roadways are often under typical static-dynamic coupling stress(SDCS)conditions with high ground stress and strong dynamic disturbances.With the increasing number of disasters and accidents induced by SDCS conditions,the safe and efficient production of coal mines is seriously threatened.Therefore,it is of great practical significance to study the deformation and failure characteristics of the roadway surrounding rock under SDCS.In this paper,the effects of different in-situ stress fields and dynamic load conditions on the surrounding rock are studied by numerical simulations,and the deformation and failure characteristics are obtained.According to the simulation results,the horizontal stress,vertical stress and dynamic disturbance have a positive correlation with the plastic failure of the surrounding rock.Among these factors,the influence of the dynamic disturbance is the most substantial.Under the same stress conditions,the extents of deformation and plastic failure of the roof and ribs are always greater than those of the floor.The effect of horizontal stresses on the roadway deformation is more notable than that of vertical stresses.The results indicate that for the roadway under high-stress conditions,the in-situ stress test must be strengthened first.After determining the magnitude of the in-situ stress,the location of the roadway should be reasonably arranged in the design to optimize the mining sequence.For roadways that are strongly disturbed by dynamic loads,rock supports(rebar/cable bolts,steel set etc.)that are capable of maintaining their effectiveness without failure after certain dynamic loads are required.The results of this study contribute to understanding the characteristics of the roadway deformation and failure under SDCS,and can be used to provide a basis for the support design and optimization under similar geological and geotechnical circumstances.

Deformation characteristics of surrounding rock of broken and soft rock roadway

A similar material model and a numerical simulation were constructed and are described herein. The deformation and failure of surrounding rock of broken and soft roadway are studied by using these models. The deformation of the roof and floor, the relative deformation of the two sides and the deformation of the deep surrounding rock are predicted using the model. Measurements in a working mine are compared to the results of the models. The results show that the surrounding rock shows clear theological features under high stress conditions. Deformation is unequally distributed across the whole section. The surrounding rock exhibited three deformation stages： displacement caused by stress concentration, theological displacement after the digging effects had stabilized and displacement caused by supporting pressure of the roadway. Floor heave was serious, accounting for 65% of the total deformation of the roof and floor. Floor heave is the main reason for failure of the surrounding rock. The reasons for deformation of the surrounding rock are discussed based on the similar material and numerical simulations.

Surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms at the end of mining stage

Two case studies were conducted in the Shennan mining area of Shaanxi Province,China to evaluate the surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms· These studies mainly monitored the surrounding rock deformation and coal pillar stress in the recovery rooms of the N1206 panel of 2-2 coal seam at Ningtiaota Coal Mine and the 15205 panel of 5-2 coal seam at Hongliulin Coal Mine.The monitoring results showed that the surrounding rock deformation of the main recovery room and the coal pillar stress in the N1206 and 15205 panels began to increase significantly when the face was 36 m and 42 m away from the terminal line,respectively.After the face entered the main recovery room,the maximum roof-to-floor convergence in the N1206 and 15205 panels was 348.03 mm and 771.24 mm,respectively,and the coal pillar stresses increased more than 5 MPa and 7 MPa,respectively.In addition,analysis of the periodic weighting data showed that the main roof break position of the N1206 and 15205 panels after the longwall face entered the main recovery room was-3.8 m and-8.2 m,respectively.This research shows that when the main roof breaks above the coal pillar,the surrounding rock deformation of the main recovery room and the coal pillar stress increase sharply.The last weighting is the key factor affecting the stability of the main recovery room and the coal pillar;main roof breaks at disadvantageous positions are the main cause of the support crushing accidents.

Deformation mechanism of high-stress and broken-expansion surrounding rock and supporting optimization based on the gray correlation theory

Aiming at the large deformation and support problems of high-stress and broken-expansion surrounding rock, and taking 1 000 m level roadway of Mine II in Jinchuan as the research object, an investigation on the deformation and damage of roadway surrounding rock and an analysis of its mechanism were carried out. The gray correlation theory was used in support scheme optimization design. First, causes and mechanism of deformation of the 1 000 m horizontal transport channel were analyzed through field investigation, laboratory test and data processing methods. We arguued that poor engineering geological conditions and deep pressure increases were the main factors, and the deformation mechanism was mainly the ground deformation pressure. Second, the gray correlation theory was used to construct supporting optimization decision method in the deep roadway. This method more comprehensively considers various factors, including construction, costs, and supporting material functions. The combined support with pre-stressed anchor cables, shotcrete layer, bolt and metal net was put forward according to the actual roadway engineering characteristics. Finally, 4 support schemes were put forward for new roadways. The gray relational theory was applied to optimizing the supporting method, undertaking technical and economic comparison to obtain the correlation degree, and accordingly the schemes were evaluated. It was concluded as follows： the best was the flexible retaining scheme using the steel strand anchor; the second best was the one using plate anchors on the top and rigid common screw steel bolt on the two sides; the ttiird was; the rigid common screw steel bolt in full section of roadway; and the worst is the planished steel rigid support. The optimized scheme was applied to the 1000 m level of new excavation roadway. The results show that the roadway surrounding rock can reach a stable state after 5 to 6 months monitoring, with a convergence rate less than 1 mm/d.

Tunnel Surrounding Rock Deformation Characteristics and Control in Deep Coal Mining

In order to study the failure characteristics and control method of deep tunnel surrounding rock, based on the stress test, the structure and stress state of the main transportation tunnel surrounding rock in Mine Zhaogezhuang level 14 was analyzed, and it shows that the surrounding rock is exposed to an interphase hard and soft disadvantageous structure state and complex high stress repeated addition area;Through the theoretical analysis and the statistical data, the relation between the tunnel stress transformation and the surrounding rock deformation was proposed;Through the numerical simulation of the tunnel surrounding rock failure process with the help of RFPA procedure, the results show that the damage of the transportation tunnel level 14 mainly occurs in the bottom and the two coal ribs, and the failure process is spreading from the bottom to the two coal ribs, and the effect of the surrounding rock deformation control is obvious by using the way of 2.5 m anchor with 1.0 m grouting strengthening.

Influence of underground water seepage flow on surrounding rock deformation of multi-arch tunnel

Based on a typical multi-arch tunnel in a freeway, the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) was used to calculate the surrounding rock deformation of the tunnel under which the effect of underground water seepage flow was taken into account or not. The distribution of displacement field around the multi-arch tunnel, which is influenced by the seepage field, was gained. The result indicates that the settlement values of the vault derived from coupling analysis are bigger when considering the seepage flow effect than that not considering. Through the contrast of arch subsidence quantities calculated by two kinds of computation situations, and the comparison between the calculated and measured value of tunnel vault settlement, it is found that the calculated value(5.7-6.0 mm) derived from considering the seepage effect is more close to the measured value(5.8-6.8 mm). Therefore, it is quite necessary to consider the seepage flow effect of the underground water in aquiferous stratum for multi-arch tunnel design.

Assessing the range of blasting-induced cracks in the surrounding rock of deeply buried tunnels based on the unified strength theory

Blasting-induced cracks in the rock surrounding deeply buried tunnels can result in water gushing and rock mass collapse,posing significant safety risks.However,previous theoretical studies on the range of blasting-induced cracks often ignore the impact of the in-situ stress,especially that of the intermediate principal stress.The particle displacement−crack radius relationship was established in this paper by utilizing the blasthole cavity expansion equation,and theoretical analytical formulas of the stress−displacement relationship and the crack radius were derived with unified strength theory to accurately assess the range of cracks in deep surrounding rock under a blasting load.Parameter analysis showed that the crushing zone size was positively correlated with in-situ stress,intermediate principal stress,and detonation pressure,whereas negatively correlated with Poisson ratio and decoupling coefficient.The dilatancy angle-crushing zone size relationship exhibited nonmonotonic behavior.The relationships in the crushing zone and the fracture zone exhibited opposite trends under the influence of only in-situ stress or intermediate principal stress.As the in-situ stress increased from 0 to 70 MPa,the rate of change in the crack range and the attenuation rate of the peak vibration velocity gradually slowed.

堆积体隧道超前加固方式研究

为探究堆积体隧道超前加固方式,建立了软弱堆积体隧道三维计算模型,通过数值模拟对比了不同超前加固方式下围岩隧道变形与结构受力情况,确定了堆积体隧道最佳超前加固方式为帷幕注浆+大管棚。主要研究结论如下:双层小导管方案相比大管棚方案可控制拱顶部位的塑性区与沉降变形,减小结构拉应力,但有增大结构受压破坏的风险;双层小导管与大管棚方案相比帷幕注浆方案无法有效控制围岩变形,对堆积体隧道适用性较差;帷幕注浆方案可大幅减小围岩变形以及左右拱肩塑性区,抑制隧道与支护结构变形,控制围岩压应力与衬砌受力;帷幕注浆+大管棚方案相比帷幕注浆+单层小导管方案可进一步提升整体围岩变形与支护结构受力。

山区偏压连拱隧道开挖方法适应性数值分析研究

山区常存在偏压或围岩破碎情况,隧道穿越该地层施工时,围岩变形控制困难,施工扰动容易致使隧道拱顶坍塌及支护结构破坏。依托银花隧道工程,开展了偏压地层隧道施工开挖方法的适应性数值仿真研究,对比分析了“三导洞法”和“中导洞法”两种开挖方式中不同开挖步对软弱围岩偏压隧道围岩变形、拱顶沉降、最大主应力分布的影响规律。结果表明:三导洞法随着偏压处侧导洞开挖,左洞拱顶沉降区与中导洞开挖扰动变形区会形成沉降叠加,最大工地沉降出现在正洞开挖后,为-12.35 mm,所占沉降比η达到55.23%。中导洞施工时,最大沉降值分布在偏压拱腰处且呈扇形分布,左右洞上台阶施工产生的沉降比最大达到73.57%,中、下台阶开挖对拱顶沉降影响较小,最大拱顶沉降值为-17.81 mm。两种方法的最大主应力并非严格对称,尽管中导洞法施工产生较大沉降,但考虑施工成本和效率,“中导洞法”更为合理。

Stress distribution rule of roadway affected by overhead mining in gently inclined coal seams group

In light of the severe deformation and destruction of the district raise tunnel in the mining area at the northern part of the Lubanshan colliery, by the theoretic analysis and numerical simulation, both the mining stress distribution in seams group and the deformation and destruction mechanism of floor district raise were investigated. The results show that, at the maximum vertical distance of 40 m, the abutment stress has an influence on the recovery of 2# and 3# coal seam and 8# coal seam at distance of 30 m. As a result, the recovery of 8# is rather than those of 2# or 3# coal seam, which contributes to the deformation and destruction of the district raise surrounding rock. The major factors affecting the abutment stress include the mining depth, mining height, residual gob space, adjacent working faces and short spacing coal seam recovery.

黄土盾构隧道开挖围岩扰动特性模型试验研究

为了探究不同含水率和埋深等工况下的黄土盾构隧道开挖对围岩的扰动作用特征,采用相似模型试验,首先通过三轴试验测定了不同含水率下原状黄土物理参数及强度指标,通过大量试配得到了不同含水率下与原状黄土强度指标参数相似的试验用土。其后,考虑盾构隧道盾尾间隙特征,开展不同含水率及埋深等组合工况下盾构开挖模拟试验,通过微型土压力传感器、百分表等监测元件以及数字图像技术等手段,分析了不同工况下地层变形、地表沉降和围岩应力的变化规律。研究发现:含水率较低时,围岩的自稳能力强;含水率越高,埋深越大,开挖对地层的扰动作用也越大;地表最大沉降值与含水率呈正相关,与埋深呈负相关;围岩剩余应力随含水率和埋深的增大而增大,但当含水率增大至一定值(26.6%)时,围岩剩余应力骤减;基于不同含水率下的围岩应力及变形发展规律,可将黄土含水率分为自稳、形变以及松动含水率,基于含水率和埋深引起的围岩松动情况,可将不同工况下的黄土盾构隧道围岩压力作用模式按照形变压力和松动压力计算,以更加适应黄土地层的特性。

收敛约束法在挤压性围岩隧道中的应用

由于挤压性围岩隧道围岩性质与应力环境的特殊性,其围岩特征曲线与常规隧道有明显差异。为研究挤压性围岩隧道围岩-支护相互作用关系,考虑支护效应修正围岩特征曲线,研究不同变形等级对修正围岩特征曲线的影响规律,优化挤压性围岩双线铁路隧道初期支护。研究结果表明,毛洞状态下,受双线隧道断面应力集中影响,拱脚和墙脚为安全控制位置;随着变形等级和侧压力系数增加,支护特征曲线与修正围岩特征曲线不再相交;Ⅰ、Ⅱ级变形采用单层支护可满足安全要求,锚杆只需布置在拱部和边墙位置,Ⅱ级及以上变形锚杆需要全环布置;Ⅳ级变形在采用双层支护的同时,需考虑改善洞室形状、超前加固等措施。

高应力破碎围岩巷道控制机理及支护技术

为解决高应力破碎围岩巷道围岩支护效果差、变形破坏严重等问题,以东峡煤矿37221-2回风巷为背景,通过现场勘察、理论分析和现场试验相结合的方法,研究了高应力破碎围岩巷道的变形破坏特征和控制原理。基于原支护方案及分析成果,提出了“注浆管浅部注浆+锚杆+注浆锚索+钢筋网”的联合支护方案。现场工业试验结果表明,采用优化支护后顶底板最大移近量和两帮最大收敛量同原支护方案相比,分别减少了约77%、82%,围岩的整体性和稳定性良好。该研究可为高应力破碎围岩巷道、围岩控制提供参考和技术支持。

循环梯度加载下煤岩损伤破坏特性及能量演化规律研究

煤矿开采中岩体受开挖卸荷因素的影响常处于反复的循环加载过程,为研究循环梯度加载作用下煤岩的损伤破坏特性和能量演化规律,对煤样进行单轴循环梯度加载实验,对比分析煤岩在不同循环梯度加载下的变形破坏特性、输入能量密度、耗散能密度和损伤变量的规律。结果表明:随着循环梯度应力的递增,煤岩试样所承受的循环次数递减、峰值强度降低,分别为17.97、14.86、11.23、10.53 MPa;在循环梯度加载中,输入能量密度绝大部分以弹性应变能的形式储存于岩样内部,耗散能在单次循环输入总能量的0.2%~40%之间递增。选用累积耗散作为煤岩损伤破坏全过程的量化指标,并通过Logistic方程对煤岩损伤进行了拟合,得到了煤岩损伤的演化模型。

深埋切顶自成巷道二次复用围岩稳定性研究

为研究深埋切顶自成巷道二次复用期间的围岩稳定性,通过数值模拟和现场实测对张北矿超前1615A工作面区段轨道顺槽围岩变形规律和应力分布特征进行了分析,结果表明:受切顶卸压及恒阻锚索补强支护的双重作用,留巷复用期间顶板较为稳定,主要表现为底臌和实体煤侧帮臌,围岩呈非对称性变形,变形速率沿工作面推进方向呈三段式规律,巷内单体支承压力呈4个分区特征;工作面靠近留巷侧15 m内及超前煤壁40 m内的区域受采动应力影响较为显著,呈“L”形分布特征,超前压力峰值位于“L”形角点处;留巷复用期间应重点加强控底、控帮和离层监测;研究成果可为类似工程条件下巷道围岩控制提供科学依据。

岩体变形及二次应力下矿体开采效应研究

为了解围岩在变形及二次应力下矿体开采效应的影响,本文选取-410 m中段采用现场试验与数值模拟相结合的方法对崩落法采矿进行矿体效应研究。结果表明:围岩应力发生震荡变化,在矿体上下盘围岩附近存在应力明显降低区域,下盘大于上盘,顶板最大主应力达0.44 MPa,局部呈现应力集中,且应力集中部位呈现类似水平零散分布的现象。同时开采边界呈现裂隙发育的状态。水平矿体有轻微下沉趋势,且在该中段的水平巷道边界和顶板裂隙附近易出现断层破碎带。竖直方向变形明显,且倾斜部位呈椭圆分布,最大下沉位移值达8.00 mm,最大上升方向变形值为3.03 mm,交界线附近易受到应力挤压现象。该研究对及时准确地掌握岩体变形规律和矿山安全信息使矿山安全有效合理地进行开采具有一定的指导意义。

双掘两采留巷围岩应力演化特征及控制技术研究

为解决厚煤层双掘两采留巷围岩稳定性差、长期维护困难等技术难题,以园子沟煤矿1012007综放工作面为工程背景,采用理论分析、数值模拟以及现场实践分析了双巷掘进、一次采动、二次采动期间留巷围岩应力演化特征与塑性区发育规律,得到了留巷在一次采动期间表现出非对称应力演化特征与围岩塑性区非对称发育规律相一致,并提出了“长短锚杆索梯次支护+帮顶M型钢带整体支护+弱结构卸压”组合支护技术,最后成功应用于现场实践。

复杂破碎巷道支护难度分级方法研究与应用

为解决复杂破碎巷道支护方式选取缺乏定量化方法和标准、支护效果不稳定等难题,以金川三矿区为例,基于灾变耦合原理得到巷道变形破坏耦合路径,选取岩石强度应力比、矿岩破碎系数及岩体结构等级作为巷道支护难度评价指标,利用改进的LEC分级评价方法提出了巷道支护难度分级方法,将支护难度划分为Ⅰ~Ⅳ级。根据所提支护难度分级方法对该矿1 438 m分段进行了快速分级,并依据不同分级结果采取了对应的支护策略,支护效果良好。研究表明:所提巷道支护难度分级方法能够快速实现复杂破碎巷道支护级别分类,具有较高可靠性,为实现巷道安全、经济支护目标提供了技术支撑。

深埋引水隧洞安全监测数据分析

安全监测在地下引水隧洞工程施工过程中发挥着重要作用,监测数据可真实反映开挖施工过程中围岩变形过程和应力变化情况。东疆调水工程KSVII标地下隧洞埋深超深,开挖过程中施工支洞与上游主平洞、下游主平洞相互交叉,且交叉段洞室跨度较大,地质条件差,围岩应力结构复杂。为了分析调水工程深埋引水隧洞围岩变形、应力分布规律和发展特征,通过安装埋设监测仪器及时获取安全监测数据资料,在监测数据资料分析的基础上,分析围岩变形和应力变化情况,结果表明:围岩位移变形与围岩内部应力变化趋势基本吻合,监测仪器数值受开挖施工影响,围岩应力释放,围岩结构发生蠕变影响仪器测值变化速率持续增加;随着洞室全断面开挖完成,围岩应力重新调整,逐步向临空面释放,导致后续监测过程中监测值出现不同程度的增加或波动,待围岩应力调整完成后,监测值逐渐趋于稳定;开挖施工过程中应减少对围岩的扰动,同时及时支护,以便保障工程施工安全。研究成果可有效的指导现场开挖施工,保障工程施工安全。

厚硬石灰岩顶板工作面顺槽支护优化研究

为解决厚硬石灰岩顶板回采巷道原支护方案存在支护不当、成本过高且受采动影响时两帮围岩变形量大的问题,以山西灵石华苑煤业9103轨道顺槽为研究对象,通过现场监测并结合回采巷道煤与岩石的物理力学参数,采用工程类比法对原支护方案进行优化。运用FLAC3D数值模拟软件对优化前后巷道在掘巷期间及在受相邻工作面和本工作面采动影响后的支护效果进行对比分析,证明其优化方案的可行性。研究结果表明:优化方案在巷道掘巷完成后的顶板变形量较原方案增大2.6%,两帮变形量减小13.1%;优化支护方案在相邻工作面和本工作面采动应力作用下,顶板变形量较原方案均无明显增大,两帮移近量较原支护方案分别减小26.2%和32.8%。