大规模开采矿山地震视应力和变形与区域性危险地震预测

 大规模开采的矿山存在复杂的诱导地震活动,在高应力硬岩条件下具有产生区域性危险地震和岩爆灾害的可能性,震源的地震视应力和变形参数是地震机制和地震活动性预测研究的重要参数,对此开展研究具有重要意义。针对冬瓜山铜矿深井开采诱导地震活动,对地震视应力和位移在矿区开采过程中的时空特征开展研究,发现地震活动具有区域性分布特征,其时空分布与开采活动及矿区矿柱分布具有较强的对应关系。以此为依据,结合矿区地质构造和地应力状态,研究该矿区区域性地震机制,指出可以利用天然地震复杂震源的凹凸体理论来解释该矿区区域性地震成核机制,从而提出该矿区区域性危险性地震成核概念模型,并针对该矿地震活动的特征讨论识别成核区的方法。针对该矿区域性岩体破坏实例,分析地震视应力和变形参数时间序列特征,讨论潜在区域性地震成核区的地震活动危险性和岩体破坏性态的评价与预测。研究结果在工程实践中得到实际应用。     

岩爆的分形特征和机理

本文应用分形几何和损伤力学研究了岩爆诱发的微地震。使用分形的数目—半径关系考察了已报导的微地震事件的位置分布,发现它具有集聚(cluster)分形结构。当接近一个主岩爆时,微地震事件的集聚程度明显增加,并相应地出现分形维数值的减小。最低的分形维数值通常出现在一个主岩爆临近产生之时。这样,分形维数的变化就有可能用来进行岩爆的预测预报。这种变化与地震学中强震发生前的降维现象(b值减小)是完全一致的,我们使用损伤力学和分形概念从理论上分析了岩爆的分形和物理机理。研究表明:一个强的破坏(岩爆或地震)实际上等效于岩体内破裂的一个分形集聚。这个破裂的分形集聚所需能量耗散E随分形维数D的减小而按指数律增加:D=C_1exp[—C_2E]这样,岩爆和地震的分形自然在理论上得到很好的解释,并由此人们能更好地去理解岩爆和地震的发生和发展。     

基于矿山钻孔应变观测数据时程分形特征的冲击地压前兆分析

开采诱发的冲击地压活动与区域应力场之间存在着密切相关关系,为探究冲击地压孕育过程中相关区域岩体内部应力场的演化机制及灾害发生前兆信息,研究将钻孔应变观测技术首次应用到矿山动力灾害监测中,并采用分形盒维数定量分析钻孔应变数据时程变化特征及其与冲击地压的相关关系。结果表明,钻孔应变观测技术应用到矿山动力灾害监测中,可直接、准确地记录冲击地压发生前后区域内岩体的应变微动态变化过程;运用分形方法处理具有固体潮趋势背景的钻孔应变数据简单而有效,分形盒维数可量化评价应变数据的复杂变化和固体潮畸变异常程度;钻孔应变数据的分形盒维数时程变化,定量表征了冲击地压的非线性时空演化过程,可将盒维数的"升高→降低"变化作为冲击地压发生的前兆判据。     

基于定量地震学的矿山微震活动对开采速率的响应特性研究

 矿山地震活动是矿山开采的岩体动力响应,反映矿山岩体应力、变形和破坏状态。利用冬瓜山铜矿微震监测数据,基于定量地震学原理,采用累积视体积?VA、能量指数EI和累积开挖量?Vm时程曲线分析方法,研究矿山开采速率与微震变形之间的关系;并从能量的储存与释放的角度,结合视体积VA和弹性收敛体积VE,提出将累积地震视体积?VA与累积开采量?Vm之比作为微震活动对开采速率的响应系数(CSR),以表征岩体中能量的储存与释放关系。研究结果表明,矿山开采量对?VA和EI时程曲线特性有明显的影响,矿山开采速率与微震应变率存在对应关系,CSR的变化反映了系统的稳定变化趋势,可以方便地应用于矿山活动的监测分析和作为矿山生产速率控制的指导参数。     

西安地裂成因与地震

西安地裂是地质和人为作用共同造成的一种重大的城市环境地质灾害。目前发育的 11条活动地裂已给西安的城市规划带来了不少麻烦 ,同时也给城市建设带来了许多隐患。地裂的破坏活动日益加剧 ,从而引起社会各方面的极大关注。本文在对西安地区地裂的主要分布与力学特征调查研究的基础上 ,着重对地裂的构造成因以及地裂与地震活动的关系进行了探讨。分析表明 :过量地开采地下水以及地表水的大量渗漏 ,地震大区域的构造活动等都能加大地裂的活动速率或引起地裂的突发性活动 ,从而显著地放大地裂形成的灾害。同时 ,由于地裂的存在及形成又使得在地震时耗散更多的能量 ,从而使得地面地震动强度减小     

不同地震记录选择方法下某超高层巨型框架结构能量反应分析

通过三种地震记录选择方法,对某超高层巨型框架结构进行了大震作用下的弹塑性时程分析,研究了不同地震记录选择方法对巨型框架结构能量反应的影响。依据结构地震能量反应结果,分析了拟合设计加速度谱和拟合能量谱这两种地震记录选择方法对结构能量反应的影响及区别。可知谱匹配法生成地震记录在保持天然记录诸多特性的同时,可很好地反映结构设计加速度谱的特点。建议分别采用拟合能量谱法和谱匹配法选择天然记录和人工记录。算例分析表明,由于设计加速度谱在长周期段有所放大,因而长周期段基于拟合设计加速度谱选择记录会带来过大的结构能量反应,为按能量谱拟合结果的10倍左右,超高层结构设计与大震作用下分析时需予以重视。     

大跨度空间结构地震响应组成分量研究

应用振型叠加法进行大跨度空间结构地震响应分析时,常存在计算效率低、难以考虑地震作用随机特性等问题。为此,对大跨度空间结构的地震响应组成分量,包括准静力响应和共振响应进行研究和定义;根据响应分量的组成研究,提出适用于大跨度空间结构地震响应振型叠加分析法的修正策略;以两类典型的大跨度结构形式为算例,对各响应分量的特性及分量间相关性的影响进行研究,总结大跨度空间结构地震各响应分量的分布特征。     

泡沫混凝土人工引入孔结构分形特征研究

泡沫混凝土具有良好的热工性能和隔音轻质等特性,人工引入大量气泡,并令其均匀分布。根据分形理论,泡沫混凝土近似为具有分形结构的空间载体,分析其人工引入孔结构的分形特征,研究孔隙分布的复杂程度,并引入孔隙分布分形维数D,得出分形孔隙率的公式。     

长周期隔震结构基于反应谱理论的地震响应预测研究

在长周期基础隔震结构的地震响应计算或设计的某些阶段(如初步设计阶段或设计完成后的评估阶段),有必要建立一种地震响应实用计算方法,通过简单计算即能体现地震动长周期分量作用,提高隔震结构的地震安全性。通过选用合适的强震记录建立适合一定阻尼比和周期范围的、相应于规范设防烈度的相对位移、相对速度和绝对加速度反应谱,给出实用算式及地震动位移峰值和速度峰值;基于周期等效等准则,建立基础隔震结构的双质点系简化计算模型,推导简化计算模型参数、动力特性及地震响应的简化算式。建立基础隔震结构地震响应预测方法。利用建立的反应谱实用算式及两质点系计算模型的参数和动力特性的简化算式,可快速预测大阻尼比、长周期隔震结构地震响应。     

考虑土体非线性的核岛结构桩基础三维地震反应特性

以某沿海拟建的AP1000核岛结构为背景，用3D集中质量-梁杆模型模拟核岛结构，考虑土体的非线性滞回特性，建立非均匀地基-群桩-厚筏-核岛结构体系的3D有限元模型，选用近场中强震、中-远场强震和远场大地震的三分量记录作为基岩输入地震动，分析群桩基础的地震反应特性。非线性场地效应和土-桩-结构动力相互作用效应的耦合作用会显著增大核岛结构的基础输入运动，不论基准运行地震或安全停堆地震，基础输入运动的水平向和竖向上包络加速度反应谱(5%阻尼比)的谱值显著大于对应的AP1000标准设计反应谱谱值；桩顶累积绝对速度和地震峰值内力的大小受基岩输入地震动特性的影响显著，与场地反应的非线性程度正相关，其复杂的空间分布特征也受土-桩-结构动力相互作用效应和桩的几何布置的综合影响，桩-筏交界处的桩身地震内力反应最大，中-远场和远场强震作用对核岛桩基础的潜在破坏风险可能远大于近场中强地震作用。     

Classification of clustered microseismic events in a coal mine using machine learning

Discrimination of seismicity distributed in different areas is essential for reliable seismic risk assessment in mines. Although machine learning has been widely applied in seismic data processing, feasibility and reliability of applying this technique to classify spatially clustered seismic events in underground mines are yet to be investigated. In this research, two groups of seismic events with a minimum local magnitude (M_L) of −3 were observed in an underground coal mine. They were respectively located around a dyke and the longwall face. Additionally, two types of undesired signals were also recorded. Four machine learning methods, i.e. random forest (RF), support vector machine (SVM), deep convolutional neural network (DCNN), and residual neural network (ResNN), were used for classifying these signals. The results obtained based on a primary dataset showed that these seismic events could be classified with at least 91% accuracy. The DCNN using seismogram images as the inputs reached the best performance with more than 94% accuracy. As mining is a dynamic progress which could change the characteristics of seismic signals, the temporal variance in the prediction performance of DCNN was also investigated to assess the reliability of this classifier during mining. A cascaded workflow consisting of database update, model training, signal prediction, and results review was established. By progressively calibrating the DCNN model, it achieved up to 99% prediction accuracy. The results demonstrated that machine learning is a reliable tool for the automatic discrimination of spatially clustered seismicity in underground mining.     

采矿诱发地震分类的探讨

为有利于矿震灾害的预测、预防和治理,针对目前矿震各种分类间尚未建立起相互联系体系的现状,应用该灾害机制的最新研究成果,按照有利于对症治理灾害的原则,照顾到已被普通接受的习惯,提出矿震层级分类的概念、原则和优越性。按照矿震发生受原生构造应力场作用方式、岩石介质物理力学性质及岩层力学结构对矿震的控制作用、矿震与采矿活动的相关性、次生应力场动力来源和矿震发生及破坏的部位分出5个层级16种矿震类型,强调区域构造应力场和开挖造成的岩体应力状态改变在矿震分类、研究和治理中作用的重要。     

A review of mining-induced seismicity in China

Active seismicity and rockbursting have been an emerging problem in Chinese mines. The distribution and characteristics of mining-induced seismicity in China, and its monitoring, mitigation, and research, are reviewed in this paper. Mining at depth and the activity of current tectonic stress field are the two major factors leading to rockburst hazards. Three critical depths, i.e., critical initiation depth, roof upper-bound depth, and floor lower-bound depth, have been identified based on hypocenter data of seismic events in coalmines. A strong correlation between rockbursts and gas outbursts in coalmines has also been established, and it is recommended to use this correlation for rockburst and gas outburst hazard assessment and warning interchangeably. We find that the key problems of rockburst hazard mitigation in China are the lack of mine seismicity-monitoring networks in most mines, and the need for improvement of the accuracy of the monitoring systems for mines that have been equipped with such systems. Because the demand for minerals resources is extremely high and the mining activities are progressing deeper and deeper, an increasing trend of mining-induced seismicity hazards in China may be anticipated for the near future. Mining-induced seismicities are hazards, but at the same time they have been found useful for studying geophysical problems in deep ground, particularly in the field of earthquake prediction. With the enforcement of relevant laws for the mining industry and the continuous effort to study rockburst problems using rock mechanics and geophysics principles and methods, it is believed that new approaches for rockburst hazard control and mitigation can be developed.     

Evaluation and application of controlling parameters for seismic events in hard-rock mines

A method is proposed for quantitative assessment and interpretation of the seismic hazard of planned excavation in a hard-rock mine. The quantitative assessment is derived from three-dimensional, elastic, boundary element modelling of the host rock mass. Parameters obtained from the modelling are associated with historical observations of seismicity in the mine to generate probabilistic relations between seismic event occurrence and event strength. The parameters used in the event spatial occurrence relations and the event strength estimates are the Factor of Safety against seismic failure for different types of seismic events, which are inferred from back analysis of field observations, and the Modelled Ground Work. The estimates of these parameters are related to the controlling quantities for a seismic event, which are a local state of stress sufficient to cause rock mass failure, and an unstable local concentration of strain energy, i.e. energy in excess of that which can be dissipated non-violently in rock mass failure. Application of the method is illustrated by reference to several case studies of mine seismicity.     

兖州矿区某矿矿震活动规律研究

 根据兖州矿区某矿2004年11月～2009年3月监测矿震台网记录资料,研究了矿震震源定位精度的方法、震源空间分布与构造、较大矿震与原地应力、矿震与开采的关系。认为利用3分向矿震记录,并采用偏振分析和波形相关分析的方法可以提高震源定位精度;矿震发生与开采速度成正相关,在高发期与顶板周期来压呈相应同步关系,并且与开采进程不稳定程度密切相关的矿震导致顶板垮塌,形成强烈风暴摧毁了封堵墙。研究结果表明,3分向地震记录和波形分析在灾害性质诊断方面具有重要作用,为科学布置工作面,处置构造和高应力区,控制合理开采进度和防治矿震灾害提供了重要依据,是探索矿震预测的一条重要途径。     

Ground support design for dynamic loading conditions:A quantitative data-driven approach based on rockburst case studies

There are considerable challenges associated with the design of ground support for seismically-active underground mines.It is extremely difficult to establish the demand on ground support as well as the capacity of a ground support system.The resulting dynamic or impact loads caused by mining-induced seismicity are difficult to anticipate and quantify.The performance of a ground support system is defined by the load distribution and interaction between several reinforcement and surface support elements.Consequently,the design of ground support in seismically-active mines tends to evolve,or be modified based on qualitative assessments of perceived performance or response to significant seismic events or rockbursts.This research is motivated by a need to provide quantitative and data-driven design guidelines for ground support systems subjected to dynamic-loading conditions.Rockburst data were collected from three deep and seismically-active underground mines in the Sudbury basin in Canada.The constructed database comprises 209 seismic events that resulted in damage to mine excavations and ground support.These events were associated with damage at 324 locations within the three mines.The developed ground support design strategy,based on these documented case studies,identifies areas where the use of dynamic or enhanced support should be employed.The developed design methodology provides guidelines for the zoning of mine locations in which installation of enhanced support is recommended.the specifications for an optimal ground support system,and the timing or sequence of installation.     

Some examples of the impact of metalliferous mining on the environment: a South African perspective

Metalliferous deposits have played and continue to play a vital role in the economy of South Africa, gold being the most important. The shallow early mines, now abandoned, give rise to subsidence. As a result, the erection of buildings on the undermined land in the old reef area, which runs east to west through the city of Johannesburg, has been controlled by the Government Mining Engineer, including the permissible heights of buildings in relation to the depth of the mining. More recently, the controls have been relaxed when development proposals have been accompanied by sound methods of mine stabilization. Various types of subsidence are discussed, including both the development of sinkholes, which can take place rapidly and have catastrophic results and loss of life, and dolines, associated with dewatering activity. Induced seismicity has also been associated with gold mining. Investigations showed that the seismic events originated near working faces and occurred around the time of blasting. With magnitudes rarely exceeding 3, rarely is there significant surface damage. The conditions in which acid mine drainage related to the oxidation of sulphide minerals develops and the associated problems are also discussed. Case histories are presented to illustrate the environmental problems related directly and indirectly to the mining. Electronic Publication     

Quantitative assessment of the spatio-temporal correlations of seismic events induced by longwall coal mining

Rock failure process as a natural response to mining activities is associated with seismic events, which can pose a potential hazard to mine operators, equipment and infrastructures. Mining-induced seismicity has been found to be internally correlated in both time and space domains as a result of rock fracturing during progressive mining activities. Understanding the spatio-temporal(ST) correlation of mininginduced seismic events is an essential step to use seismic data for further analysis, suc...