To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numeric...To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numerical simulation was carried out.The tempo-spatial damage characteristics of rock mass were analyzed.The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated.Additionally,a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass.The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently.The large-stake crown of the main powerhouse was the main damage area.Prior to the rock collapse,the MS event count and accumulated energy release increased rapidly,while the apparent stress sharply increased and then decreased.The amount and proportion of shear and mixed MS events remarkably increased.The maximum displacement was generally located near the spandrel areas.The MS monitoring data and numerical simulation were in good agreement,which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.展开更多
为解决传统初始地应力场反演方法存在边界条件筛选能力弱、易受数据过拟合干扰以及难以解析多重边界相互作用的问题,提出一种基于LASSO-OLS(least absolute shrinkage and selection operator-ordinary least squares)的两阶段初始地应...为解决传统初始地应力场反演方法存在边界条件筛选能力弱、易受数据过拟合干扰以及难以解析多重边界相互作用的问题,提出一种基于LASSO-OLS(least absolute shrinkage and selection operator-ordinary least squares)的两阶段初始地应力场反演方法。该方法首先通过对候选边界条件应力矩阵和实测应力矩阵进行Frobenius范数标准化处理,消除不同边界条件数据量级差异的影响;然后,利用LASSO回归的L1正则化约束,从候选边界条件的回归系数路径图中筛选关键影响因素,剔除冗余与弱相关项;最后,针对筛选出的核心变量,采用普通最小二乘回归进行无偏估计,构建兼具稀疏性与准确性的地应力场反演模型。研究结果表明:1)在工程应用实例中,借助LASSO回归从11个候选边界条件中筛选出5个关键因素,显著降低模型复杂度;2)模型正则化参数在标准误差内取值,拟合结果能够保持较高的复相关系数(R=0.995 2),表明筛选后的边界条件有效捕捉了初始地应力场特征;3)初始地应力场反演模型通过LASSO回归筛选,在解析多重边界相互作用时表现出较高的稳定性和物理合理性;4)与传统方法相比,该方法能有效避免初始地应力场反演出现过拟合问题,提高反演结果的鲁棒性。展开更多
压缩空气储能(compressed air energy storage,CAES,简称“压气储能”)电站地下储气洞室的压力与直径之积极大,因此密封钢衬的受力状态对于电站长期安全运行至关重要。基于ABAQUS平台,综合考虑材料的非线性特征及密封钢衬与混凝土衬砌...压缩空气储能(compressed air energy storage,CAES,简称“压气储能”)电站地下储气洞室的压力与直径之积极大,因此密封钢衬的受力状态对于电站长期安全运行至关重要。基于ABAQUS平台,综合考虑材料的非线性特征及密封钢衬与混凝土衬砌之间的接触非线性,分析了围岩初始地应力对密封钢衬应力分布和混凝土衬砌损伤演化的影响机制。结果表明:在侧压力系数k由0.25增大至2.50的过程中,密封钢衬的应力峰值呈现先减小、后逐渐增大的趋势,密封钢衬高应力区、混凝土衬砌损伤严重区及围岩塑性区均从顶部和底部逐渐转移至腰部,且当侧压力系数k=1.00时,结构与围岩沿圆周受力最为均匀;在卸压检修期,密封钢衬顶部与混凝土衬砌之间会形成缝隙,且缝隙值随侧压力系数k的增大先减小后缓慢增大,但k>1.00后其敏感性降低;围岩地应力对衬砌结构力学响应的影响机制主要是通过调整运行期围岩环向应力状态,从而改变围岩塑性区分布,最终影响混凝土衬砌与密封钢衬的外部约束刚度。该研究对于通过数值模拟方法开展压气储能地下洞室技术论证时考虑初始地应力的影响具有参考价值。展开更多
基金Project(2017YFC1501100)supported by the National Key R&D Program of ChinaProjects(51809221,51679158)supported by the National Natural Science Foundation of China。
文摘To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numerical simulation was carried out.The tempo-spatial damage characteristics of rock mass were analyzed.The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated.Additionally,a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass.The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently.The large-stake crown of the main powerhouse was the main damage area.Prior to the rock collapse,the MS event count and accumulated energy release increased rapidly,while the apparent stress sharply increased and then decreased.The amount and proportion of shear and mixed MS events remarkably increased.The maximum displacement was generally located near the spandrel areas.The MS monitoring data and numerical simulation were in good agreement,which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.
文摘为解决传统初始地应力场反演方法存在边界条件筛选能力弱、易受数据过拟合干扰以及难以解析多重边界相互作用的问题,提出一种基于LASSO-OLS(least absolute shrinkage and selection operator-ordinary least squares)的两阶段初始地应力场反演方法。该方法首先通过对候选边界条件应力矩阵和实测应力矩阵进行Frobenius范数标准化处理,消除不同边界条件数据量级差异的影响;然后,利用LASSO回归的L1正则化约束,从候选边界条件的回归系数路径图中筛选关键影响因素,剔除冗余与弱相关项;最后,针对筛选出的核心变量,采用普通最小二乘回归进行无偏估计,构建兼具稀疏性与准确性的地应力场反演模型。研究结果表明:1)在工程应用实例中,借助LASSO回归从11个候选边界条件中筛选出5个关键因素,显著降低模型复杂度;2)模型正则化参数在标准误差内取值,拟合结果能够保持较高的复相关系数(R=0.995 2),表明筛选后的边界条件有效捕捉了初始地应力场特征;3)初始地应力场反演模型通过LASSO回归筛选,在解析多重边界相互作用时表现出较高的稳定性和物理合理性;4)与传统方法相比,该方法能有效避免初始地应力场反演出现过拟合问题,提高反演结果的鲁棒性。
文摘压缩空气储能(compressed air energy storage,CAES,简称“压气储能”)电站地下储气洞室的压力与直径之积极大,因此密封钢衬的受力状态对于电站长期安全运行至关重要。基于ABAQUS平台,综合考虑材料的非线性特征及密封钢衬与混凝土衬砌之间的接触非线性,分析了围岩初始地应力对密封钢衬应力分布和混凝土衬砌损伤演化的影响机制。结果表明:在侧压力系数k由0.25增大至2.50的过程中,密封钢衬的应力峰值呈现先减小、后逐渐增大的趋势,密封钢衬高应力区、混凝土衬砌损伤严重区及围岩塑性区均从顶部和底部逐渐转移至腰部,且当侧压力系数k=1.00时,结构与围岩沿圆周受力最为均匀;在卸压检修期,密封钢衬顶部与混凝土衬砌之间会形成缝隙,且缝隙值随侧压力系数k的增大先减小后缓慢增大,但k>1.00后其敏感性降低;围岩地应力对衬砌结构力学响应的影响机制主要是通过调整运行期围岩环向应力状态,从而改变围岩塑性区分布,最终影响混凝土衬砌与密封钢衬的外部约束刚度。该研究对于通过数值模拟方法开展压气储能地下洞室技术论证时考虑初始地应力的影响具有参考价值。
