Modern seismicity in mining areas in the Murmansk Region

The Murmansk Region in the northeastern Baltic Shield has been for long assumed as aseismic. Initiated in the 1950s, the regular instrumental seismological studies allow new data on the essential increment in seismicity, demonstrated in the maps of the general seismic zoning of the territory of Russia. Powerful mining industry in the Murmansk Region also induces many seismic events. This article analyzes natural and induced seismicity and their cross-effect.     

Laws of spreading and operational evaluation procedure for induced seismicity in mines and in mining areas

The scope of the article encompasses features of natural and induced seismicity and the change in frequency plots when natural seismicity turns into natural-and-induced seismicity in mining areas and when induced seismicity becomes natural-and-induced seismicity in mines. It is shown how induced seismicity is connected with the subsidence of overlying strata in mines—seismic process propagates together with the subsidence but seismic activity lowers in the time of maximum subsidence and intensifies when subsidence ceases or decelerates. The authors lay emphasis on estimates of seismic activity in mines and give details of an integrated index F procedure tested in mines and adjusted within the 10 year-long period of application.     

Review of the strongest rockbursts and mining-induced earthquakes in Russia

Based on the review of the strongest rockbursts and mining-induced earthquakes with the same seismic characteristics recorded in underground mines in Russia, the author compares the events based on their energy parameters. It is shown that the mining-induced seismic events on the Kola Peninsula are still the strongest events.     

Effect of Pendulum Waves from Earthquakes on Gas-Dynamic Behavior of Coal Seams in Kuzbass

In the framework of the theory of interaction between nonlinear geomechanical and physicochemical processes in coal seams under mining and based on the piston mechanism of gas dynamic processes, it has experimentally been proved that nonlinear quasi-metric elastic pendulum waves from natural and induced earthquakes have influence on gas-dynamics in mines in Kuzbass. The objects selected to identify the interrelationship were the large earthquakes occurred in Kuzbass on November 9, 2016 (magnitudes 2.7 and 3.7) and the records of the quake-induced gas dynamic activity in the Alarda and Osinniki mines.     

Mining-induced seismicity at open pit mines in Kuzbass (Bachatsky earthquake on June 18, 2013)

The data on the world-strongest earthquake induced by hard mineral mining—Bachatsky earthquake (local magnitude 6.1) in Kuzbass on June 18, 2013—are reported. Seismic activation of the territory at the Bachatsky Open Pit Mine in 2012–2013 awoke three large earthquakes, sensibly affecting the Kuzbass towns. The authors have analyzed the results of experiments on temporal seismology nets in 2012 and the records of the after-shocks of the Bachatsky earthquake in 2013. The low energy seismic activity is revealed in rocks under the Bachatsky and Shestaki OPMs. It is found that small earthquakes cluster under the center of the open pit mine bottoms, and the larger earthquakes crowd under the pitwalls, and the depth of the earthquake sources is 3–4 km.     

Regional geomechanical-geodynamic control geoinformation system with entropy analysis of seismic events (In Terms of Kuzbass)

The presented geoinformation system is based on cloud service classification of natural and mining-induced seismic events. The data entropy-based models treat seismic signals as functions of a “waveguide” led from a seismic source to a seismic station. The quality similarity or distinction of the models is related with the genesis of seismic events. The service includes Google App Engine cloud calculating technologies, IRIS Data Management Center web-services and local seismic monitoring databases. The application of the cloud service to classifying unknown-genesis seismic events is illustrated by the examples.     

9. Microseismic activity associated with hydraulic mining

Microseismic activity induced by the hydraulic mining of steeply inclined coal seams has been monitored in order to clarify the strata mechanics of hydraulic mining. A mine-wide seismometer network detected 652 microseismic events, with local magnitudes greater than −2.5, during mining of the panel which is situated at 1000 m below the surface. The largest microseismic event with a local magnitude of 0.1 was felt both on the surface and underground. The magnitude-frequency relation of seismic events followed Gutenberg-Richter's formula, in which the b-value was estimated as 0.92. The seismic energy release rate varied with face advance due to changes in the mining geometry and configuration. A majority of hypocentres concentrated on the coal pillar which had been left in the old workings and was bounded by the active mining panel. Another group of seismic foci clustered on a pre-existing fault which runs through the border of the panel. The other events were distributed around the coal face and moved with the face advance. The spatial distribution of the seismic energy suggests that microseismic activity associated with hydraulic mining is mainly induced by collapse of coal pillars and fracture of the front abutment of coal face, and also partly caused by the roof caving into the goaf and by floor heave.     

Triggered Seismicity in a Flooded Former Coal Mining Basin (Gardanne Area,France)

We studied the correlation between seismicity and the water table level in an abandoned coal mine (Bouches-du-Rhône, France), closed in 2003, where groundwater has been pumped out since 2010 to prevent underground flooding. Microseismicity was first felt by the population in 2010 and a strongly felt seismic swarm occurred in November 2012. The origin of the seismicity was therefore questioned, in relation to both the potential instability of old, shallow galleries that might generate damage at the surface and a local seismic hazard assessment. A temporary dense seismic network in the area allowed us to analyse the spatial distribution of the seismicity in detail. Most of the seismicity was clearly located under the mine workings, highlighting that an existing fault system crossing the mining operation was being hydraulically activated, in accordance with the known tectonic extension regime. Our analysis clearly shows a spatiotemporal relationship between seismic migration and the level of the mine aquifer between 2013 and 2017. Thus, seismicity will persist with oscillations of the mining aquifer, depending on the pumping capacities and effective rainfall. Continuous hydraulic and seismic monitoring is necessary to better understand these phenomena and assess the associated risks.

     

Shallow geophysical exploration of the Upper Kama Potash Salt Deposit

The mining safety circuit based on geophysical research is described in the article in terms of the Upper Kama Potash Deposit, with exemplification of different stages of the geophysical survey design. The authors discuss options of integrated interpretation of seismic and electric exploration data aiming to locate and monitor hazardous natural and mining-induced processes in potassium-enclosing strata.     

强矿震临界破裂阶段的岩体弹性波场

为探索井田范围较大尺度岩体破裂失稳的危险性预测,以抚顺老虎台井田为工程背景,反演连续12个月矿震弹性波的传播速度比（v_P/v_S）和质点振动振幅比（A _S/A _P）,分析强矿震临界发生阶段的弹性波场变异特征。结果显示,M_L≥1.5矿震的波场信息较敏感,在M L≥3.0（E≥1.8×10⁸J弹性能）矿震前,波速比和振幅比绝大多数存在显著的低值异常,预测M _L≥3.0矿震的信度分别为0.79和0.93,虚假异常和缺失异常较少,具有良好的应用前景。波速比和振幅比在强矿震临界破裂前存在的降低和恢复过程,可能指示能量核心区岩体的张性破裂扩容和裂隙闭合过程。     

Blasting and the man-made seismicity in the tashtagol mining area

Based on the analysis into the influence of blasting on the seismic activity in the area of the Tashtagol ore deposit, the paper shows that quantity, energy and concentration of the mining-induced seismic events grows in the blasting site region. The background-values of seismic activity come back in a period between 11 hours to 3 days after the blasting, and the seismic activity intensification depends on the blast energy.     

隔水层采动破坏裂隙的闭合机理研究及工程应用

煤层顶底板的采动裂隙是煤矿一系列灾害事故发生的根源,对其发育及演化规律的研究对各类灾害事故的防治具有重要意义。论文借助现场超声波成像技术、室内岩石矿物成分分析以及岩石膨胀性实验等手段,分析了影响煤层顶板采动裂隙闭合的相关因素,揭示了顶板隔水层采动裂隙的闭合规律。结果表明:顶板隔水层中的蒙脱石(包括伊/蒙混层)含量越高,其膨胀程度越大;隔水层距煤层顶板的距离越大,膨胀程度亦越大;在不发生顶板结构严重破坏的情况下,当隔水层的体积膨胀率大于采动裂隙的发育率,采动裂隙将实现有效闭合。最后,通过在新安煤田水体下采煤岩体渗透性评价以及神东矿区水资源保护性开采中的工程应用,对顶板采动裂隙的闭合机理进行了验证,并取得了良好的应用效果。     

顶板岩层动力事件发生机理与防治方法

在长壁开采过程中不可避免地会对顶板岩层产生强烈扰动,这种扰动可能扩展到开采区域以外的地方,并且岩石变形破坏的形式也不相同。当岩层坚硬时,储存的能量可能频繁地以高能量微震形式释放出来。当岩层本身所储存的能量无法缓慢释放时,矿震现象常常会发生。研究表明,岩层本身所储存的能量与岩层本身的尺寸有密切的关系。因此,可以采用一些方法或措施来减少采矿诱发的矿震。该措施基于人为的方法破坏储存弹性能的岩层结构,其中最有效的方法之一就是采用定向水压致裂技术。     

矿山微震震源机制的初步研究

矿山微震震源机制是揭示和认识矿震发生机理,从事矿山微震监测预报、矿震灾害防治的基础和前提,也是从事矿震研究的理论基础之一。根据完整岩石破裂机理,从刚度理论的角度论证了岩石动力破坏的理论条件;在总结矿山常见的岩体破坏类型的基础上,对几种基本的矿震机制进行了全面的论述。     

沟谷地形下开采覆岩裂隙发育特征研究

为了研究沟谷地形条件下薄基岩浅埋煤层覆岩采动裂缝发育规律,以神府矿区为研究基地,对安山煤矿5-2煤开采工作面的覆岩采动裂缝发育特征进行分析,建立弱强度覆盖层作用下的基本顶受力模型,即“非均布载荷梁”结构模型。通过对非均布载荷梁结构的力学分析,推导基岩承载结构稳定性的判别条件,确定了基本顶两端压力、剪力及垮距等参数的计算公式,揭示了弱强度覆盖层厚度及坡度变化对覆岩采动裂缝间距的影响规律。实践表明,依据非均布载荷梁模型确定的覆岩采动裂缝间距与周期来压步距近似相等|覆岩采动裂缝随基岩破断失稳而呈周期性动态发育演化特征,工作面上方地表附近塌陷型和台阶型采动裂缝较为发育,采空区上方地表裂缝逐渐演化成错动量及张开量较小的闭合型地表裂缝。     

采动影响下逆断层冲击地压矿震时空分布规律分析

为了分析开采扰动下逆断层冲击地压矿震活动时空分布规律,根据G-R地震活动幂次分布规律,结合现场微震监测数据与数值模拟方法,通过矿震活跃度b值以及地震矩值M 0对井下矿震活动分布规律以及高震级事件能量释放水平进行了分析。研究结果表明:在时间跨度上,井下矿震事件频次分布规律符合G-R分布规律,b值越小,高震级矿震事件在整个矿震事件中频次越高,对工作面冲击危险性影响越严重。b值受原岩应力、开采扰动、断层性质的影响:最大与最小主应力差值越大、开采速率越快、断层倾角越小、落差越大,b 值越小;逆断层地震矩M 0在空间分布上有着明显的差异性。靠近高位岩层附近断层面区域的地震矩值为整个断层面上的峰值区域,随着工作面不断逼近断层面,断层面上的高峰值区域会不断增大且向下部区域蔓延,使得整个断层面上的地震矩不断增大。断层面地震矩值的增大意味着可释放能量水平不断提高,对工作面造成的扰动也会更加剧烈,进一步增大冲击地压事故的危险性。     

Procedure and results of seismic investigations into causes of landslides in permafrost rocks

The article focuses on seismic monitoring of causes of landslides. Such studies are of great importance in open pit mining in permafrost rocks. Extensive mining-induced impact in combination with natural thawing of permafrost as a consequence of the planet warming may end in catastrophe. The authors describe a procedure for plotting velocity profiles of seismic waves along slopes in the presence of extremely contrast discontinuities conditioned by permafrost rocks. The presented approach enables studying slip surfaces of landslides and detecting potential failure zones where wave velocities are lower due to extensive jointing. The processed field data obtained in the area near Chagan-Uzun settlement in Kosh-Agach district of the Republic of Altai are reported.     

Influence of undulating fault surface properties on its seismic waves during fault-slip

Seismic waves arising from fault-slips induced by mining activities in underground mines can inflict severe damage to mine openings. Laboratory experiments on the cataclastic rock-flour found on surfaces of mining-induced faults have revealed that intense shock pulses can arise due to the unloading of fault surface asperities during fault-slip. This paper focuses on investigating the effect of fault surface asperities on the intensity of the seismic waves. Dynamic modelling of fault-slip with a mine-wide model has revealed that particle velocity of the rockmass can increase substantially when unloading takes place. It is concluded that considering the occurrence of locally intense seismic waves is indispensable for optimising secondary support systems.     

裂隙带顶板巷道围岩破坏机理及稳定性控制

针对上行开采过程中顶板巷道支护困难的问题,采用UDEC离散元数值模拟软件对上行开采过程中采场采动裂隙、塑性区以及巷道围岩裂隙、塑性区发育进行了系统的研究和分析,研究结果表明:采动作用下顶板巷道围岩破坏以巷道顶、底板破坏最为明显,靠工作面侧的巷帮破坏次之。采场采动裂隙、塑性区发育与巷道围岩裂隙、塑性区发育在工作面的推进过程中不断相互吸引和促进,最终贯通。同时,当采动作用达到一定程度时,采动裂隙会以顶板巷道顶板为起点向上发育,而巷道肩角处塑性区向上产生畸形发展,其发育方向与采场覆岩断裂角一致,其发育高度远远大于未受采动影响的巷道塑性区发育高度。基于分析结果,提出了上行开采裂隙带顶板巷道支护策略,并以山脚树矿上行开采为工程背景对其顶板巷道原有的支护形式进行了改进,改进后的支护能够有效保证巷道围岩稳定。以上研究成果可为上行开采工程中顶板巷道的支护提供设计参考,丰富采动巷道围岩稳定性控制理论成果。