Numerical simulation and analysis of drill rods vibration during roof bolt hole drilling in underground mines

Structural deterioration in the roof in an underground mine can easily cause roof fall, and deterioration is difficult to detect. When drilling holes for roof bolts, there is a relationship between the vibration of the drill rod and the properties of the rock being drilled. This paper analyzes transverse, longitudinal, and torsional vibrations in the drill rod by using vibration theory. Characteristic indexes for three kinds of vibration are determined. Using the finite element analysis software ABAQUS, a model for drill rod vibration during the drilling of roof bolt holes was established based on the geological and mining conditions in the Guyuan Coal Mine, northern China. Results from the model determined that the transverse and the longitudinal vibration decrease as the rock hardness decreases. In descending order, sandstone,sandy mudstone, mudstone, and weak interbeds cause progressively less vibration when being drilled.The ranking for strata that cause decreasing torsional vibration is slightly different, being, in descending order, mudstone, sandstone, sandy mudstone, and weak interbeds. These results provide a theoretical basis for predicting dangerous roof conditions and the presence of weak interbeds to allow for adjusting bolt support schemes.

Effects of proper drilling control to reduce respirable dust during roof bolting operations

Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fine rock partic- ulates from drilling could escape from the dust collection system and become airborne under some circumstances causing the roof bolter operators expose to quartz-rich respirable dust. A previous research shows that drilling can be controlled through properly selected penetration and rotational rates to reduce the specific energy of drilling. Less specific energy means less energy is wasted on generating noise, heat and over-breakage of rock. It implies that proper control of drilling has a great potential to generate significantly less fine rock dust during drilling. The drilling experiments have been conducted to study the effect of controlling drilling on reducing respirable dust. The preliminary results show that the size distributions of respirable dust were different when controlling drilling in different bite depths. This paper presents the findings from laboratory experimental studies.

Development of a roof bolter drilling control process to reduce the generation of respirable dust

The drilling operation in the roof bolting process,especially in hard rock,generates excessive respirable coal and quartz dusts,which could expose the roof bolting operator to continued health risks.Previous research has shown that the amount of respirable dust produced is dependent on the main drilling parameters,specifically the drilling rotational and penetration rate.In this paper,a roof bolter drilling control process was proposed to reduce the generation of respirable dust.Based on the analysis of laboratory drilling test results,a rational drilling control process(adjusting rotational and penetration rates)to achieve the optimal drilling parameter for different rock types was proposed.In this process,the ratio between specific energy and rock uniaxial compressive strength was used as the index to determine the optimal operation point.The recommended drilling operation range for the rock type used in the experiment was provided,and the reduction in respirable dust generation was demonstrated.By following this control process,the drilling efficiency can be monitored in real time,so the system can stay in a relatively high-energy efficiency with less respirable dust production from the drilling source.This algorithm is targeted to be incorporated into the current roof bolter drilling control system for drilling automation so that a safe and productive drilling operation can be conducted in a healthy working environment.

Three-dimensional numerical simulation of methane drainage by high-level drill holes in a lower protective coal seam with a “U” type face

Different drill-hole positions may produce different drainage results in low protective coal seams.To investigate this possibility,a 3D stope model is established,which covers three kinds of drill holes.The FLUENT computational fluid mechanics software is used to solve the mass,momentum and species conservation equations of the model.The spatial distributions of oxygen and methane was obtained by calculations and the drainage results of different drill-hole positions were compared.The results show that,from top to bottom,methane dilution by oxygen weakens gradually from the intake to the return side,and methane tends to float;methane and oxygen distribute horizontally.The high-level crossing holes contribute to better methane drainage and a greater level of control.Around these holes,the methane density decreases dramatically and a "half circle"distribution is formed.The methane density decreases on the whole,but a proportion of the methane moves back to deep into the goaf.The research findings provide theoretical grounds for methane drainage.

高强放瓦斯工作面顶板抽采巷道适宜位置分析

综采工作面在开采吸附强、解吸弱的高阶煤时,由于采动应力解除,将会遇到破煤、围岩以及相邻煤层瞬时释放大量瓦斯进入回采工作面的情况,极易造成工作面瓦斯超限事故。为此,以采空区上覆岩层不同区域裂缝特征为基础,阐述了顶板抽采巷道的抽采机理,并采用不同位置顶板抽采巷道、不同水平和垂直位置顶板定向长钻孔和数值模拟上覆岩层应力释放效应3种方法,对矿区瓦斯抽采效果进行研究,提出了基于上覆岩石应力释放比确定采空区最佳抽采位置的方法。结果表明:顶板抽采巷道和顶板定向长钻孔在矿区进行定向抽采,最佳位置水平距回采工作面回采巷道25 m,垂直距煤层顶板50~55m。

高瓦斯煤层工作面顶板定向长钻孔瓦斯抽采技术研究

为实现高瓦斯矿井采煤工作面采空区及卸压瓦斯的有效治理,以2301采煤工作面为研究对象,将顶板定向长钻孔应用到采空区顶板裂隙瓦斯抽采中,并对现场应用效果进行了分析。结合2301采煤工作面现场地质条件、理论计算结果及以往钻孔瓦斯抽采经验,合理确定了顶板定向长钻孔的位置,并给出了施工技术方案。工程应用后,顶板定向长钻孔瓦斯抽采效果显著,可有效拦截采空区瓦斯,2301采煤工作面回采期间回风隅角瓦斯体积分数控制在了0.55%以内。现场实践表明,顶板定向长钻孔可实现采空区顶板裂隙瓦斯的高效抽采,改变了采空区瓦斯的流动方向,是一种较为经济有效的瓦斯治理措施。

特厚煤层顶板关键层地面压裂技术应用与优化

厚硬顶板在回采工作面推进期间自行垮落困难,开采过程中易引发工作面强矿压显现、引起安全事故,为避免胡家河煤矿401106工作面开采期间出现此类问题,综合运用理论分析、工程类比等手段进行地面水力压裂技术进行设计及优化研究,选用电缆泵送桥塞射孔联作压裂工艺技术,确定合理的水平井压裂分段段长、选择合适的工具、支撑剂类型,在401106工作面实施地面压裂工艺后,对比分析401105工作面、401106工作面支架载荷变化规律,压裂后工作面支架压力普遍在35 MPa以下,采动压力减弱特征明显,说明地表水力压裂技术可以有效降低工作面因厚硬顶板岩层垮塌而产生的强矿压,保障了工作面安全高效生产。

Controlling mine pressure by subjecting high-level hard rock strata to ground fracturing

When mining extra-thick coal seams,the main cause of strong ground pressure are the high-level thick and hard strata,but as yet there is no active and effective control technology.This paper proposes the method of subjecting hard roofs to ground fracturing,and physical simulation is used to study the control effect of ground fracturing on the strata structure and energy release.The results show that ground fracturing changes the structural characteristics of the strata and reduces the energy release intensity and the spatial extent of overburden movement,thereby exerting significant control on the ground pressure.The Datong mining area in China is selected as the engineering background.An engineering test was conducted on site by ground horizontal well fracturing,and a 20-m-thick hard rock layer located 110 m vertically above the coal seam was targeted as the fracturing layer.On-site microseismic monitoring shows that the crack propagation length is up to 216 m and the height is up to 50 m.On-site mine pressure monitoring shows that(1)the roadway deformation is reduced to 100 mm,(2)the periodic weighting characteristics of the hydraulic supports are not obvious,and(3)the ground pressure in the working face is controlled significantly,thereby showing that the ground fracturing is successful.Ground fracturing changed the breaking characteristics of the high-level hard strata,thereby helping to ameliorate the stress concentration in the stope and providing an effective control approach for hard rock.

沿空留巷密集钻孔切顶机理及关键参数确定方法

为实现密集钻孔切顶条件下沿空留巷顶板结构安全稳定,研究正常情况与密集钻孔条件下顶板岩层结构受力状况,基于岩石断裂理论和弹性理论分析回采前后顶板密集钻孔孔间围岩受力分布及其破断过程,明确密集钻孔切顶机理及相邻钻孔的孔间集中应力相互作用机制,推导工作面端头弧形三角板结构巷道侧边界密集钻孔孔间围岩的拉剪应力计算公式。在此基础上,分析不同参数对孔间围岩所受拉剪应力的影响作用,提出沿空留巷密集钻孔切顶关键参数确定方法。研究表明:密集钻孔主要通过回采前后钻孔周围应力条件改变来增加钻孔围岩拉剪应力集中程度,引起孔间裂隙扩张联通,形成切缝线破断关键岩层。回采前钻孔主要受水平挤压应力影响,回采后钻孔受力逐渐转变为采空区顶板回转下沉产生的拉剪应力为主,钻孔孔间围岩状态随之由孔间围岩弱化阶段过渡到孔壁裂纹成形阶段,再转变为孔间围岩破断阶段。密集钻孔孔间围岩所受拉剪应力大小主要取决于关键岩层厚度及钻孔孔径与孔间距之比,与钻孔高度及间距成负相关,与角度及直径正相关。据此提出了密集钻孔关键参数确定方法,并根据龙滩矿3124 N工作面坚硬顶板条件设计了密集钻孔切顶留巷方案,确定钻孔长度为8.3 m,角度为15°,钻孔直径为48 mm,间距为500 mm。留巷后巷道顶帮变形可控且整体稳定性较好,由此可证明密集钻孔布置参数较为合理,密集钻孔关键参数确定方法有效可行。

厚煤层沿空留巷变形漏风机制及多元协同防治技术

为解决厚煤层沿空留巷墙体变形机理及采空区漏风流场不清、瓦斯防治效果不佳的问题,以山西沁城煤矿20107工作面为工程背景,采用力学建模、理论分析研究了沿空留巷顶板断裂位置对应力集中及传播路径的控制作用,并指出断裂线位于留巷外侧时,可有效转移支撑应力并卸压,并提出了分段压裂切顶关键位置的计算方法。采用单元法实测,从采空区漏风量分布及留巷漏风通道两方面,揭示了沿空留巷采空区漏风流场及瓦斯浓度分布规律,进而提出了沿空留巷采空区瓦斯多元防治技术,即采用定向钻孔分段压裂切顶卸压-强化瓦斯抽采超前协同共治为主,弱化转移顶板来压避免墙体变形产生裂隙漏风的同时提高采空区瓦斯抽采效率;采用硅酸盐复合材料对已有墙体裂隙发育区(顶板交界处、插管外壁周围)进行喷涂堵漏,封堵留巷漏风通道;辅以留巷插管参数优化及控风降压,进一步减小采空区漏风及瓦斯涌出,并通过现场考察验证。研究结果表明:①20107采空区漏风以运输巷进风流正压漏入为主、回风侧以高浓瓦斯漏入沿空留巷为主,工作面倾向0~36 m区段正压漏风量332.84 m^(3)/min,占工作面总体漏入采空区风量(572.15 m^(3)/min)58.17%;留巷走向54~108 m区段留巷漏入风量408.45 m^(3)/min,占采空区总体漏入沿空留巷风量(469.01 m^(3)/min)87.09%;②优化后,裂隙带定向钻孔(压裂孔+抽采孔)平均瓦斯抽采纯量为7.46 m^(3)/min,压裂切顶后留巷墙体变形、裂隙控制大幅改善,沿空留巷平均瓦斯体积分数由原0.59%逐渐降至0.34%,实现工作面高效达产。

润宏煤业1305工作面静态膨胀剂致裂顶板卸压技术研究

以润宏煤业1305工作面地质条件为工程背景,采用静态膨胀技术对运输巷顶板切顶卸压,避免煤柱侧应力集中。通过理论分析、实验室测试、现场工程试验等方法,分析和测试了静态膨胀剂的膨胀力性能,计算分析了静态膨胀剂作用下切顶卸压的钻孔参数,设计了详细的施工工艺。研究结果表明,静态膨胀剂的最大膨胀力可达到70 MPa,且持续时间长,完全可以用于煤岩致裂工程。钻孔间距、钻孔直径以及钻孔角度是影响静态膨胀剂致裂效果的主要参数。钻孔内产生的静态膨胀压力作用到孔壁,且能一直保持到顶板进入采空区后,在矿压、自重及静态膨胀力的作用下,顶板会出现裂缝、裂缝扩展、顶板致裂垮落3个过程。根据现场具体工程条件,在多组成排钻孔共同膨胀作用下,可形成膨胀应力的叠加,能够起到更好的致裂效果。研究为探索和推广煤矿非爆破式顶板致裂技术提供了借鉴。

李村煤矿顶板定向长钻孔瓦斯抽采参数优化研究

针对高抽巷工程量大、成本高、影响采掘接替等问题,分析了顶板定向长钻孔的合理布置范围、抽采机理及关键影响因素,并根据正交实验和方差分析确定了抽采效果敏感性指标。在李村煤矿1305工作面进行了顶板定向长钻孔代替高抽巷的试验,试验结果表明:顶板定向长钻孔达到了高抽巷瓦斯抽采的效果,将上隅角瓦斯浓度控制在安全范围内,且其施工进度快,成本低,有效解决了李村矿采掘接替紧张的局面。

基于1DCNN-BiLSTM-CBAM的煤巷顶板岩层地质特征随钻智能识别方法

【目的】煤巷顶板事故多发生于原生裂隙发育带和岩层破碎带等潜在垮落区,准确、及时掌握顶板岩层地质特征并优化其支护方案及参数是预防顶板事故的重要途径。目前关于巷道顶板岩层地质特征识别方法的相关研究存在识别速度慢、效率低、成本高等问题,难以满足煤矿安全、高效和智能化开采的需求。【方法】提出了一种基于1DCNN(一维卷积神经网络)、BiLSTM(双向长短期记忆网络)和CBAM(卷积块注意力模块)相结合的神经网络模型,建立了随钻振动加速度信号与顶板岩层地质特征的对应关系,通过钻进试验,采集完整岩石、破碎岩石和含裂隙岩石样本的随钻振动加速度信号数据,并将此信号作为训练样本,在此基础上建立了不同岩石样本与其随钻振动信号之间的对应关系,并采用准确率、精确率、召回率和F1值4项分类指标评估各模型的性能。【结果和结论】研究表明:(1)建立的1DCNN-BiLSTM-CBAM模型实现了端到端的岩层地质特征智能识别,简化识别流程,提高识别效率。(2) SVM(支持向量机)、1DCNN、BiLSTM以及1DCNN-BiLSTM-CBAM模型训练结果表明,1DCNN-BiLSTM-CBAM模型的平均准确率、精确率、召回率和F1值分别达到99.22%、99.26%、99.21%和99.23%,均优于其他对比模型。(3)实验验证该模型在煤巷顶板岩层地质特征的分类识别中是有效的,且具有良好的分类识别性能,能够满足巷道顶板岩层地质特征实时智能的识别要求。研究为识别煤巷潜在垮落区以及制定顶板支护方案提供了有力的技术支持,提供了一种煤矿巷道顶板随钻探测的高效识别方法,对提升煤矿巷道安全保障技术具有重要的借鉴意义。

基于“两带”探查技术的顶板水害危险性分析——以伯方煤矿为例

应用钻液漏失量观测、岩芯采取统计、钻孔电视观测和钻孔电阻率动态监测等多种“两带”探查技术方法,对伯方煤矿3煤开采的覆岩导水裂隙带发育特征进行研究,分析3煤采动影响下的顶板水害危险性。研究结果表明:3213工作面导水裂隙带发育高度为87.66 m,发育至K9砂岩含水层;垮落带发育高度为22.61 m,发育至2煤下部K8砂岩含水层。3313工作面垮落带最大高度为煤层顶板20~21 m,至2煤顶板砂岩含水层;导水裂隙带最大高度为煤层顶板83~87 m,至K9砂岩含水层。由此计算得出的垮落/采厚比为3.58~3.76,裂缝/采厚比为14.85~15.56。3煤回采产生的导水裂隙可造成二叠系下石盒子组和山西组砂岩含水层与3煤采空区的连通,含水层地下水岩导水裂隙向下渗流,增加了顶板水害的风险。建议矿井严格落实顶板水害防治的相关要求,降低采动裂隙对矿井正常生产的影响。

坚硬顶板水力压裂弱化技术应用

为有效改善坚硬顶板工作面来压强度,本文以寺河二号井煤矿1309工作面地质条件为基础,采用现场试验与监测等方法,对坚硬顶板水力压裂技术进行了应用,设计了切眼及顺槽巷道水力压裂钻孔参数,并在现场进行了实践。根据水力压裂后巷道顶板窥视结果与矿压显现结果,采用水力压裂技术后顶板压裂效果较好,初次来压步距减小21%,周期来压步距减小17%,水力压裂技术能实现弱化顶板的效果。

掘进工作面顶板富水区超前疏放治理技术

为解决吕梁山煤电有限公司3-3032综掘巷道顶板富水区对掘进安全及巷道支护的影响,保证安全掘进,采取物探手段明确低阻异常区域划分范围,利用定向钻机向异常区施工顶板疏放水钻孔,待孔口放水量稳定在5 m^(3)/h及以下时,对钻孔实施全段注浆封孔,充填导水裂隙,掘进期间通过注浆锚杆与螺纹钢锚杆对顶帮围岩补强加固,加固后的巷道顶板最大移近量为164 mm,未出现明显离层空顶现象。

煤层顶板高位大直径定向钻孔瓦斯抽采技术研究

在煤层瓦斯抽采工程中,在钻场这些关键区域,布置了6个高位钻孔,这些钻孔布局合理位置精准,能最大限度地抽取邻近层和采空区中的瓦斯。充分考虑瓦斯运移规律,将钻孔层位选定在砂质泥岩与细砂岩的交界面,距离煤层顶板约30~65 m,以确保钻孔能够最大限度地抽取瓦斯。通过这一高位大直径定向钻孔技术,成功实现了对煤层顶板瓦斯的长期、稳定抽采,使采空区瓦斯涌出量得到了有效控制。在测试结果中,钻场内1#~6#孔平均抽采混量为9.76 m3/min,单孔的最大抽采混量为33.992 m3/min,得出高位大直径定向钻孔在瓦斯抽采过程中具有显著效果,对于提升煤矿瓦斯治理水平具有重要意义。随着煤化工行业的快速发展,提升其技术水平具有重要作用,因此需加强这方面研究,才可以更好地实际应用。

近距离薄煤层群首采层卸压瓦斯协同抽采技术研究

为有效解决近距离薄煤层群开采首采层上、下邻近层大量卸压瓦斯涌入的治理问题,以某煤矿为研究对象,采用理论分析和数值模拟的方法,研究近距离薄煤层群开采条件下卸压瓦斯运移规律,并根据富集特征确定卸压瓦斯抽采钻孔的空间位置。研究结果表明:首采层开采覆岩导气裂隙带最大发育高为10.3~23.2 m。设计超大直径顺层预抽钻孔高0.8 m,宽2.08 m;顶板定向长钻孔终孔最优抽采位置为垂直距离开采层顶板15.0~23.0 m,水平距离回风侧20.5~27.5 m;2条埋管抽采最佳错距为距底板高1.1,1.7 m,深入采空区11.3,20.8 m。优化后的布置参数应用于现场实践,试验工作面回采期间上隅角瓦斯体积分数保持在0.7%以下。研究结果能够实现近距离薄煤层群开采条件下卸压瓦斯高效抽采,保证矿井安全高效生产。

采场“两带”发育高度经验计算与实测验证

针对海湾煤矿42211综采工作面上覆顶板和遗留的其他矿井3-1煤采空区可能对该工作面正常生产活动产生影响,需要准确探查该区域采场上覆顶板“两带”发育高度的范围,从而对顶板隐蔽致灾因素进行探查和有效防治。以42211工作面为例,通过将经验公式推导得到的“两带”发育高度和井下仰斜钻孔观测装置得到的实测数据进行对比和相互印证,最终取得了较为接近的结果,说明利用井下仰斜钻孔观测的方法,能够得到工作面“两带”发育高度的准确数据,为类似的工作面实测“两带”发育高度提供了可行性研究方法。