考虑岩体性质空间变异的岩爆倾向性概率评估

Probability evaluation of rockburst tendency considering the spatial variation in rock mass properties

  • 摘要: 为了探究更为符合工程实际的岩爆倾向性评判方法,对岩爆倾向性及其不确定性问题进行了研究. 首先,建立改进的黏结强度弱化−摩擦强度强化模型,结合能量指标实现岩爆倾向性分析;依托埋深超千米的大红山铜矿工程,将点估计−有限元分析应用于岩爆倾向性评判,构建分析模型;进一步求得岩爆倾向性的概率模型,并得到直观的概率分布情况. 结果表明:所用本构及指标可较好地进行岩爆倾向性分析,考虑参数变异性后,95%置信度的岩爆深度与现场记录深度吻合度较高,岩爆角度范围也基本吻合,比仅取定值更为准确,验证了所作不确定性分析的可行性与正确性. 不同统计指标符合不同的分布函数,岩爆深度、范围角及完全能量释放值的最优分布分别为Normal分布、Gamma分布及Lognormal分布. 基于深度及范围角指示,以80%、40%、20%为界限,可将倾向性概率划分为极大、大、中、小四个等级区间,岩爆区域的概率分布图可以更为直观合理地判断出岩爆破坏的区域和概率. 研究结果对岩爆支护及风险评估具有参考意义.

     

    Abstract: Rockburst disasters pose an increasing threat to the construction safety of deep-buried engineering; thus, rockburst prediction is crucial for ensuring construction safety. However, due to the spatial variation in mechanical properties of rock mass, the actual results of rockburst prediction remain uncertain to some extent. In this study, rockburst tendency and its probability were studied to explore a more suitable evaluation method for rockburst tendency in engineering practice. First, an improved cohesion weakening–friction strengthening model was developed considering the dynamic change of rock dilatancy strength, and the rockburst tendency analysis was combined with the energy index. The point estimation-finite element analysis method was used to analyze rockburst tendency based on the Dahongshan copper mine project buried at a depth greater than 1,000 m. A finite element model was constructed, in which initial cohesion, residual cohesion, residual friction angle, viscous plastic strain critical value, critical value of cohesion plastic strain, and critical value of friction angle plastic strain were used as input variables, and rockburst depth, range, and local energy release value were used as output variables. The specific methods and steps of problem analysis were also elucidated. Furthermore, the probability model of rockburst failure was obtained, and the probability density function and cumulative distribution function were obtained. The probability distribution of the rockburst area was obtained by meshing the failure elements and weight combinations of different scheme results. The research results revealed that the constitutive model and index can better represent the rockburst damage compared with other methods. After considering the variability of rock mass parameters, the depth of rockburst with 95% confidence is consistent with the depth recorded in the field, and the angle range also agrees, which is more accurate than only the fixed value, thus verifying the feasibility and correctness of the uncertainty analysis. The data predicts the unspecified range and local energy release value. Moreover, different statistical indicators conform to different distribution functions. Normal, gamma, and lognormal distributions are optimal for rockburst depth, angle, and local energy release value, respectively. Thus, based on the analysis indication of depth and range, with 80%, 40%, and 20% as the limits, the probability of tendency can be divided into maximum, large, medium, or small, respectively. The probability distribution map of the rockburst area can more intuitively determine the area and probability of rockburst damage. The research results are significant for rockburst support and risk assessment.

     

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