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 and failure mechanism of Yanjiao rock slope influenced by rainfall and water level fluctuation of the Xiluodu hydropower station reservoir

With the construction of the Xiluodu hydropower station on the Jinsha River,the reservoir impoundment began in 2013 and the water level fluctuates annually between 540 m and 600 m above sea level.The Yanjiao rock slope which is located on the left bank of the Jinsha River 75 km upstream of the Xiluodu dam site,began to deform in 2014.The potential failure of the slope not only threatens Yanjiao town but also affects the safe operation of the Xiluodu reservoir.This paper is to find the factors influencing the Yanjiao slope deformation through field investigation,geotechnical reconnaissance,and monitoring.Results show that the Yanjiao slope can be divided into a bank collapse area(BCA)and a strong deformation area(SDA)based on the crack distribution characteristics of the slope.The rear area of the slope has been experiencing persistent deformation with a maximum cumulative displacement(GPS monitoring point G4)of 505 mm and 399 mm in the horizontal and vertical directions,respectively.The potential failure surface of the slope is formed 36 m below the surface based on the borehole inclinometer.The bank collapses of the Yanjiao slope are directly caused by the reservoir impoundment while the deformation area of the slope is affected by the combination of the rainfall and reservoir water level fluctuation.Based on mechanism of the Yanjiao slope,prestressed anchor combined with the surface drainage and slope unloading are recommended to prevent potential deformation.

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.

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.

断层斜交岩质高边坡开挖变形特征及其治理效果评价--以陕南地区某岩质高边坡为例

为厘清断层斜交岩质高边坡开挖变形特性以及边坡治理后的时变特性,以陕南地区某断层斜交岩质高边坡为例,综合采用现场调查、数值模拟以及多点位移监测等方法分析断层斜交岩质高边坡破坏机制,归纳了断层斜交岩质高边坡的主要致灾因子,分析了边坡开挖过程中的变形特性,并探讨了边坡治理的时效性。结果表明:研究区域地形陡峭,受断层和坡脚开挖影响呈现出典型临空地形地貌,且受地质构造影响,出露岩体破碎程度较高,节理裂隙发育;基于数值仿真论证了断层斜交岩质高边坡采用“上部锚索锁固+中部坡体刷方+下部锚索和抗滑桩加固”方案治理的可行性,现场调查和监测数据结果表明边坡治理效果明显;断层处流土溶蚀效应明显,强降雨诱发岩质高边坡后缘断层附近平台发生塌陷,在断层和坡脚部位增设排水措施后坡体病害得到有效缓解,整体变形速率得到有效控制。研究成果对断层斜交岩质高边坡的治理及破坏机制分析具有参考意义。

贵州沿空留巷支护技术的分析与改进

针对贵州某煤矿沿空留巷在原有支护条件下,靠上帮一侧顶板以及下帮底角的岩层变形破坏较严重的情况,对巷道支护方式进行改进。利用数值模拟软件,对改进支护后的巷道围岩变形破坏情况进行分析。研究发现:改进支护后的巷道围岩变形破坏情况得到明显改善,改进后的支护方式能够较好地阻滞巷道上帮一侧顶板和下帮底角的岩层严重变形破坏,从而保持巷道围岩的完整性和稳定性,研究可为类似条件矿井沿空留巷的支护方式提供参考。

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。

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。

乌兰木伦煤矿大断面硐室围岩变形破坏规律及控制

针对煤矿井下巷道大断面硐室的围岩变形破坏问题,以乌兰木伦煤矿井下分选及充填大断面硐室为研究对象,采用相似模拟实验方法,进行单调递增加载和恒定荷载加载单轴压缩实验,对大断面硐室围岩变形破坏规律进行了研究。结果表明:①2种加载方式在压密阶段、弹性变形阶段及微破裂稳定发展阶段破坏演化和变形位移趋势相似。②采用单调递增加载方式的试样裂纹较少但裂纹缝隙较大,试样沿着主裂纹突然发生破断,期间有大量碎屑飞出,试样变形位置主要集中在围岩边界,破坏时释放能量较多,但峰后释放能量持续时间较短。③采用恒定荷载加载方式的试样应力保持不变,应变缓慢增加,期间产生大量微小裂纹,试样变形位置主要围绕在硐室周围,破坏时释放能量较少,但峰后释放能量持续时间较长。依据大断面硐室围岩变形破坏规律,提出了锚杆索支护方案:硐室顶部打长锚索,将顶板和上方坚硬岩石连成整体;在硐室煤岩交界处打倾斜锚杆,将煤岩交界面与周围岩体紧密连接。数值模拟结果表明,支护后围岩应力、位移、塑性区均明显减小,围岩稳定性大幅提高,支护效果良好。

深部顶板夹煤层巷道变形破坏分析及其控制

为了探究深部顶板夹煤层软岩巷道大变形破坏问题,以平煤六矿三水平戊二胶带运输巷为工程背景,开展夹煤层巷道围岩破坏分析及控制对策的研究。首先,构建原支护体系组合拱力学模型,推导出直墙半圆拱形巷道稳定判别式;其次,提出“锚网索-梁-注浆-组合砂浆锚索”联合返修控制对策,即沿戊8煤层顶板进行巷道扩刷,采用锚网索、梯子梁完成基本支护,对围岩进行深浅孔注浆加固、顶板及两帮关键部位布置组合砂浆锚索等加强支护,并通过数值模拟分析返修前后应力、位移场分布特征;最后,开展工业性试验,并监测矿压。结果表明:两帮及顶底板最大收敛量分别为93、112 mm,后期变形速率均低于1 mm/d,围岩变形得到有效控制,返修效果良好。

倾斜煤系地层大断面客专隧道大变形原因分析及处置

针对沪昆铁路刘家庄隧道穿越煤系地层施工中发生的大变形现象,基于理论分析、数值模拟和现场监测方法,分析隧道发生大变形的原因,推导并验证了产生大变形的起始位置,得到了掌子面上方煤层单元体沿倾斜面方向的应力状态与隧道进入含倾斜煤系地层水平距离之间的变化规律,对倾斜煤层单元体与初期支护结构的应力与变形进行了分析。结果表明:掌子面上方煤体单元应力状态变化随掌子面进入倾斜煤层下方水平距离的增加,围岩经历挤压、压剪和剪切滑移3个变形阶段。围岩大变形与初期支护结构破坏均发生在剪切滑移阶段的初期,应在压剪变形阶段结合现场监测数据对掌子面进行喷射混凝土封闭、注浆加固掌子面上方松散煤层和加强初期支护结构刚度等措施以预防隧道产生大变形。

顶强帮弱半煤岩巷道围岩变形特性及控制对策

针对“顶强帮弱”半煤岩巷道巷帮围岩塑性破坏范围大、锚杆支护强度不足等围岩控制难题,以某矿8#煤层回采巷道为工程背景,在围岩力学性能测试、钻孔可视化观测及声波法实测巷帮不同高度松动圈的基础上,对该类巷道围岩的力学及宏观变形特征进行了研究,得出巷帮煤层既是影响巷道整体稳定的“短板”,又是支护的“关键”。建立数值模型分析了“顶强帮弱”半煤岩巷道围岩受采动影响的变形特征、应力分布规律及承载特性,提出了强化帮部薄弱部位的围岩控制对策,并进行了工业性试验。结果表明:对“顶强帮弱”半煤岩巷道帮部煤层采用“锚杆+斜拉穿层锚索+强护表构件”的支护对策可使其处于三向压缩受力状态,约束其向巷道内挤出变形,发挥封闭及主动促稳作用。

基于Apriori算法的盘江矿区煤与瓦斯突出特征研究

为揭示盘江矿区煤与瓦斯突出灾害发生规律,提高瓦斯防治工作的针对性,根据Apriori算法规则的原理和方法,对盘江矿区37起煤与瓦斯突出事故点的瓦斯地质参数进行了统计分析,以最小支持度为40%、最小置信度为75%的二项关联规则基准开展了数据挖掘试验。结果表明:煤层瓦斯压力1~2 MPa与埋深200~400 m、煤厚2~4 m与煤的瓦斯放散初速度≥15mmHg、煤厚2~4 m与煤厚变异系数≤0.2、泥岩厚度≤5 m与围岩强度系数≥2,是具有强关联特征的参数组合类型,盘江矿区发生煤与瓦斯突出地点都呈现浅埋深、高瓦斯压力、厚煤层和围岩强度大的典型特征;在特殊的山地浅埋深条件下(200~400 m),煤层原始地应力往往不大,高瓦斯压力是煤与瓦斯突出的主要影响因素,煤层瓦斯压力普遍达到1~2 MPa;煤厚增大、瓦斯放散初速度高反映出煤体结构受到过强烈破坏,局部发育具有煤与瓦斯突出倾向的构造煤,煤厚变异系数小预示煤层遭受的破坏形式不以煤层局部变异为特征,可能存在以分层构造煤特征的煤体结构破坏的形式;在煤层的顶底板砂岩等强岩层普遍较厚的情况下,煤层高强度砂岩顶板在开采扰动下产生的动载荷条件,叠加形成了煤与瓦斯突出发生强应力场条件;高瓦斯压力、构造煤与顶板围岩特性是影响盘江矿区煤与瓦斯突出的主要因素,在煤矿开采过程中,应以瓦斯压力作为主导参数指标,并重视结合构造煤、顶板岩性的特征来开展煤层突出预测与治理工作。

应力扰动路径对煤岩力学性能的影响试验研究

在利用废弃矿井抽水蓄能过程中,煤柱不仅受到单调荷载的影响,而且会遭受频繁的应力扰动。以陕西省河畔煤矿煤岩为研究对象,研究了单调荷载(路径1)、多级等幅循环荷载(路径2)、多级增幅循环荷载(路径3)影响下试样的强度、变形特征以及破坏模式。试验结果表明:循环荷载作用下,试样的应力-应变曲线形成了明显的滞回环,且随着应力水平增加,滞回环面积显著增加;与轴向应变相比,环向应变对应力路径的敏感性更强;单调荷载作用下煤样的峰值强度和峰值应变最大,多级循环荷载作用下试样的强度和峰值轴向应变分别降低了22.12%、18.35%(路径2)、5.30%、10.34%(路径3);应力路径2作用下的试样割线模量明显高于其他应力路径;应力路径对试样宏观破坏模式的影响甚微,但多级循环荷载使得试样表面裂纹数量和尺寸变大。

珠海市南水镇金龙边坡变形破坏特征及稳定性评价

边坡稳定性分析评价是边坡调查评价过程中一个不可或缺的环节。以珠海市金龙边坡为研究对象,分析了边坡的发育特征、影响因素、形成机制。在查明边坡岩土体出露及结构特征基础上,根据典型断面C、ϕ值反演分析及敏感性分析结果,确定金龙边坡岩土体物理力学参数,采用极限平衡法对金龙边坡进行稳定性分析评价。评价结果表明:金龙边坡在天然工况下处于欠稳定状态,在饱和及饱和+地震工况下处于不稳定状态。

地震荷载下唐家山滑坡动力响应特征及破坏机理研究

为分析北川唐家山滑坡地震动力响应特征和变形破坏机理,通过振动台模型试验和FLAC 3D数值模拟开展研究。研究表明:地震作用下,中缓倾角顺层岩质边坡加速度响应表现出“高程效应”和“趋表效应”。地震波加载频率达20~30 Hz时,坡面各测点加速度响应峰值和坡脚监测点加速度峰值的比值即PGA放大系数呈现显著递增趋势;加载不同振幅地震波,坡面各测点PGA放大系数均呈现递增趋势。坡体失稳表现出明显时间和空间上的差异性,具有多次滑动现象,出现层间错动的多个滑动面。地震作用下该类边坡的破坏模式主要为“拉裂-剪切-滑移”型,破坏过程主要分为层间结构面拉裂、松弛阶段,竖向拉裂缝形成阶段,结构面剪切阶段和整体滑移阶段。研究成果对进一步认识此类边坡动力稳定性影响规律具有一定参考意义,可为防灾减灾和抗震设计提供科学依据。

王庄煤矿构造应力扰动下大断面巷道围岩控制技术研究

针对王庄煤矿9105工作面受构造应力影响导致的大断面巷道变形严重问题,采用数值模拟与现场监测相结合的方法,研究了大断面巷道变形特征及其围岩控制技术。分析表明,巷道断面尺寸效应在4.5 m×4.5 m以上时表现更加突出,不利于巷道稳定;随着侧压系数的增加,巷道顶底板及两帮移近量均呈现增加趋势,侧压系数越大,巷道变形增加越剧烈;9105工作面巷道由于宽度较大,导致巷道顶板及两帮变形严重。据此设计了大断面巷道采用“高强度螺纹钢锚杆+预应力锚索+金属网+工字钢棚”联合支护技术。通过工程实践,顶底板移近量降低48.1%,两帮移近量降低55.4%,实现了构造巷道的有效控制。

煤柱-顶板结构能量演化特征及稳定性研究

煤矿事故的发生大多是由煤柱及其上覆顶板岩层失稳破坏引起的。为了研究不同煤-岩高度比对煤柱-顶板结构变形破坏及能量演化机制的影响,对煤-岩高度比分别为1∶3、1∶2、1∶1、2∶1及3∶1的煤-岩组合体进行了单轴加载及循环加卸载试验,研究了煤-岩结构体变形与能量演化之间的变化关系,利用加卸载响应比对煤-岩组合体的稳定性进行分析,对煤-岩组合体稳定性进行定量评价。结果表明:煤-岩组合体在单轴加载及循环加卸载作用下的峰值强度均随着煤-岩高度比的增加而逐渐降低,煤-岩组合体在循环加卸载作用下的峰值强度均低于单轴加载试验中的峰值强度,煤-岩高度比越大,循环载荷作用下组合体峰值强度降低率越小;组合体输入能、弹性能和耗散能随应力增加呈非线性增加,煤-岩高度比与组合体循环载荷过程中产生的平均弹性应变、平均弹性能、平均残余应变、平均耗散能、总残余应变和加卸载响应呈正比关系,与总弹性应变、总弹性能和总耗散能呈反比关系。

超千米深埋沿空巷道围岩破坏特征及控制技术研究

为解决超千米深埋沿空巷道围岩失稳难题,以平煤股份十一矿具体工程为背景,通过表面位移监测、钻孔窥视、围岩钻孔取芯及拉压剪常规力学试验,分析了典型超千米深埋沿空巷道的围岩损伤破坏规律,提出了以高性能中空钢绞线锚索为基础的厚层预应力全长锚固理论与技术,并通过现场试验对维控效果进行了验证。结果表明:该类巷道围岩属于高应力—节理化复合型软岩,长期维控具有较大挑战。采用厚层预应力全长锚固技术后,巷道顶板及两帮的变形量相比原支护方案降低58.64%、61.65%,巷道掘巷稳定期明显减短,围岩完整性、稳定性及巷道稳定性显著加强,能够满足巷道长期维控的要求。