把坚硬顶板视为弹性梁,把煤柱视为应变软化介质并采用W e ibu ll分布描述它的损伤本构模型,本文对坚硬顶板和煤柱组成的力学系统,用突变理论方法研究了它的演化失稳过程。通过对建立的尖点突变模型的分析发现,系统失稳主要取决于系统的...把坚硬顶板视为弹性梁,把煤柱视为应变软化介质并采用W e ibu ll分布描述它的损伤本构模型,本文对坚硬顶板和煤柱组成的力学系统,用突变理论方法研究了它的演化失稳过程。通过对建立的尖点突变模型的分析发现,系统失稳主要取决于系统的刚度比k与材料的均匀性或脆性指标m值,并给出了失稳的充要条件力学判据和失稳突跳量的表达式。考虑煤柱介质的粘性或蠕变性,建立了系统演化的非线性动力学模型———物理预报模型,并给出了根据顶板沉降观测数据反演非线性动力学模型的方法和稳定性判别准则。对木城涧矿根据观测序列进行了动力学模型的反演分析,一个重要发现是:D值在临近失稳时陡增出现峰值而后急剧下降。根据材料损伤与声发射累计计数的对应关系,建立了系统演化过程中声发射率的动力学模型,并进行了声发射模拟分析和分维分析,发现m值与系统的演化路径对系统演化的声发射活动规律及分维特征有重要影响,单纯根据声发射监测和降维现象预报冲击地压是不可靠的。展开更多
By analysing the instability process of various nonlinear systems, we conclude that their instability precursors are the continual heightening of the response rate or response ratio.Applying this theory to earthquake ...By analysing the instability process of various nonlinear systems, we conclude that their instability precursors are the continual heightening of the response rate or response ratio.Applying this theory to earthquake prediction, we adopt the periodical change of the stress in crust caused by the tide-generating force as the loading and unloading. If we can measure the ratio of the response (such as crust deformation, gravity and seismicity) during the loading period to that during the unloading period, this parameter must contain some characteristic information about the seismogenic process.With nine earthquakes (M≥7) data that occurred in Chinese mainland during 1970-1988, we take the sum of square root o?energy of small earthquakes, which is called the released strain by Benioff, as the response to the tidal loading and unloading. We find that the response ratios of seven earthquakes increase obviously before the main earthquakes.展开更多
Technical challenges have always been part of underground mining activities,however,some of these challenges grow in complexity as mining occurs in deeper and deeper settings.One such challenge is rock mass stability ...Technical challenges have always been part of underground mining activities,however,some of these challenges grow in complexity as mining occurs in deeper and deeper settings.One such challenge is rock mass stability and the risk of rockburst events.To overcome these challenges,and to limit the risks and impacts of events such as rockbursts,advanced solutions must be developed and best practices implemented.Rockbursts are common in underground mines and substantially threaten the safety of personnel and equipment,and can cause major disruptions in mine development and operations.Rockbursts consist of violent wall rock failures associated with high energy rock projections in response to the instantaneous stress release in rock mass under high strain conditions.Therefore,it is necessary to develop a good understanding of the conditions and mechanisms leading to a rockburst,and to improve risk assessment methods.The capacity to properly estimate the risks of rockburst occurrence is essential in underground operations.However,a limited number of studies have examined and compared yet different empirical methods of rockburst.The current understanding of this important hazard in the mining industry is summarized in this paper to provide the necessary perspective or tools to best assess the risks of rockburst occurrence in deep mines.The various classifications of rockbursts and their mechanisms are discussed.The paper also reviews the current empirical methods of rockburst prediction,which are mostly dependent on geomechanical parameters of the rock such as uniaxial compressive strength of the rock,as well as its tensile strength and elasticity modulus.At the end of this paper,some current achievements and limitations of empirical methods are discussed.展开更多
文摘把坚硬顶板视为弹性梁,把煤柱视为应变软化介质并采用W e ibu ll分布描述它的损伤本构模型,本文对坚硬顶板和煤柱组成的力学系统,用突变理论方法研究了它的演化失稳过程。通过对建立的尖点突变模型的分析发现,系统失稳主要取决于系统的刚度比k与材料的均匀性或脆性指标m值,并给出了失稳的充要条件力学判据和失稳突跳量的表达式。考虑煤柱介质的粘性或蠕变性,建立了系统演化的非线性动力学模型———物理预报模型,并给出了根据顶板沉降观测数据反演非线性动力学模型的方法和稳定性判别准则。对木城涧矿根据观测序列进行了动力学模型的反演分析,一个重要发现是:D值在临近失稳时陡增出现峰值而后急剧下降。根据材料损伤与声发射累计计数的对应关系,建立了系统演化过程中声发射率的动力学模型,并进行了声发射模拟分析和分维分析,发现m值与系统的演化路径对系统演化的声发射活动规律及分维特征有重要影响,单纯根据声发射监测和降维现象预报冲击地压是不可靠的。
基金This work is sponsored by the National Natural Science Foundation and the Joint Seismological Science Foundation of China.
文摘By analysing the instability process of various nonlinear systems, we conclude that their instability precursors are the continual heightening of the response rate or response ratio.Applying this theory to earthquake prediction, we adopt the periodical change of the stress in crust caused by the tide-generating force as the loading and unloading. If we can measure the ratio of the response (such as crust deformation, gravity and seismicity) during the loading period to that during the unloading period, this parameter must contain some characteristic information about the seismogenic process.With nine earthquakes (M≥7) data that occurred in Chinese mainland during 1970-1988, we take the sum of square root o?energy of small earthquakes, which is called the released strain by Benioff, as the response to the tidal loading and unloading. We find that the response ratios of seven earthquakes increase obviously before the main earthquakes.
基金the funding received by a grant from Natural Sciences and Engineering Research of Canada(NSERC)for this study.
文摘Technical challenges have always been part of underground mining activities,however,some of these challenges grow in complexity as mining occurs in deeper and deeper settings.One such challenge is rock mass stability and the risk of rockburst events.To overcome these challenges,and to limit the risks and impacts of events such as rockbursts,advanced solutions must be developed and best practices implemented.Rockbursts are common in underground mines and substantially threaten the safety of personnel and equipment,and can cause major disruptions in mine development and operations.Rockbursts consist of violent wall rock failures associated with high energy rock projections in response to the instantaneous stress release in rock mass under high strain conditions.Therefore,it is necessary to develop a good understanding of the conditions and mechanisms leading to a rockburst,and to improve risk assessment methods.The capacity to properly estimate the risks of rockburst occurrence is essential in underground operations.However,a limited number of studies have examined and compared yet different empirical methods of rockburst.The current understanding of this important hazard in the mining industry is summarized in this paper to provide the necessary perspective or tools to best assess the risks of rockburst occurrence in deep mines.The various classifications of rockbursts and their mechanisms are discussed.The paper also reviews the current empirical methods of rockburst prediction,which are mostly dependent on geomechanical parameters of the rock such as uniaxial compressive strength of the rock,as well as its tensile strength and elasticity modulus.At the end of this paper,some current achievements and limitations of empirical methods are discussed.
