The complexity of a rock masses structure can lead to high uncertainties and risk during underground engineering construction.Laboratory tests on fractured rock-like materials containing a tunnel were conducted,and tw...The complexity of a rock masses structure can lead to high uncertainties and risk during underground engineering construction.Laboratory tests on fractured rock-like materials containing a tunnel were conducted,and twodimensional particle flow models were established.The principal stress and principal strain distributions surrounding the four-arc-shaped and inverted U-shaped tunnels were investigated,respectively.Numerical results indicated that the dip angle combination of preexisting fractures directly affects the principal stress,principal strain distribution and the failure characteristics around the tunnel.The larger the absolute value of the preexisting fracture inclination angle,the higher the crushing degree of compression splitting near the hance and the larger the V-shaped failure zone.With a decrease in the absolute value of the preexisting fracture inclination angle,the compressive stress concentration of the sidewall with preexisting fractures gradually increases.The types of cracks initiated around the four-arc-shaped tunnel and the inverted U-shape tunnel are different.When the fractures are almost vertical,they have a significant influence on the stress of the sidewall force of the four-arc-shaped tunnel.When the fractures are almost horizontal,they have a significant influence on the stress of the sidewall of the inverted U-shaped tunnel.The findings provide a theoretical support for the local strengthening design of the tunnel supporting structure.展开更多
用材料破坏过程分析系统MFPA2D(material failure process analysis)数值模拟方法对钢筋混凝土桥墩在偏心加载条件下的受力、变形与内部裂缝萌生、扩展及最终破坏的全过程进行了数值模拟.数值模型中引入了统计分布函数,反映了混凝土的...用材料破坏过程分析系统MFPA2D(material failure process analysis)数值模拟方法对钢筋混凝土桥墩在偏心加载条件下的受力、变形与内部裂缝萌生、扩展及最终破坏的全过程进行了数值模拟.数值模型中引入了统计分布函数,反映了混凝土的非均匀性影响,并采用具有残余强度的弹脆性本构模型及破坏单元材料性质退化方法,利用偏心加载方式对钢筋混凝土构件实施加载.数值试验得出的荷载-位移曲线及破坏模式图与文献的试验结果较接近,数值试验还给出了试件破坏过程图及应力分布图,再现了整个破坏过程,而且通过对模型中受拉区2个多单元信息剖线的提取,对剖线中不同位置点应力随加载步的变化情况进行了研究和分析,揭示了结构破坏的机理.数值试验结果对于深入了解钢筋和混凝土的联合受力规律有参考价值.展开更多
为满足电能质量监测网存储与传输海量录波数据的需要,提出了提升格式的2维离散小波变换、多级树集合分裂(set partitioning in hierarchical tree,SPIHT)编码、算术编码相结合的数据压缩方法。为了有效降低数据的冗余度,该方法将采集的...为满足电能质量监测网存储与传输海量录波数据的需要,提出了提升格式的2维离散小波变换、多级树集合分裂(set partitioning in hierarchical tree,SPIHT)编码、算术编码相结合的数据压缩方法。为了有效降低数据的冗余度,该方法将采集的1维电能质量数据按整数倍周期排列为2维矩阵;采用提升格式的2维离散小波变换对数据进行压缩,然后对小波系数进行SPIHT编码,实现了对压缩性能的控制;最后采用算术编码进一步提高了压缩比。对几类常见的电能质量扰动数据进行了压缩实验,证明该方法具有较好的压缩性能。在不同压缩码率下对ATP-EMTP仿真模型得到的扰动数据进行了压缩实验,验证了该方法能通过控制压缩码率实现对压缩性能的控制。展开更多
基金Project(41807241) supported by the National Natural Science Foundation of ChinaProject(2021M693544) supported by China Postdoctoral Science FoundationProject(2022JM-160) supported by the Natural Science Basic Research Program of Shaanxi,China。
文摘The complexity of a rock masses structure can lead to high uncertainties and risk during underground engineering construction.Laboratory tests on fractured rock-like materials containing a tunnel were conducted,and twodimensional particle flow models were established.The principal stress and principal strain distributions surrounding the four-arc-shaped and inverted U-shaped tunnels were investigated,respectively.Numerical results indicated that the dip angle combination of preexisting fractures directly affects the principal stress,principal strain distribution and the failure characteristics around the tunnel.The larger the absolute value of the preexisting fracture inclination angle,the higher the crushing degree of compression splitting near the hance and the larger the V-shaped failure zone.With a decrease in the absolute value of the preexisting fracture inclination angle,the compressive stress concentration of the sidewall with preexisting fractures gradually increases.The types of cracks initiated around the four-arc-shaped tunnel and the inverted U-shape tunnel are different.When the fractures are almost vertical,they have a significant influence on the stress of the sidewall force of the four-arc-shaped tunnel.When the fractures are almost horizontal,they have a significant influence on the stress of the sidewall of the inverted U-shaped tunnel.The findings provide a theoretical support for the local strengthening design of the tunnel supporting structure.
文摘用材料破坏过程分析系统MFPA2D(material failure process analysis)数值模拟方法对钢筋混凝土桥墩在偏心加载条件下的受力、变形与内部裂缝萌生、扩展及最终破坏的全过程进行了数值模拟.数值模型中引入了统计分布函数,反映了混凝土的非均匀性影响,并采用具有残余强度的弹脆性本构模型及破坏单元材料性质退化方法,利用偏心加载方式对钢筋混凝土构件实施加载.数值试验得出的荷载-位移曲线及破坏模式图与文献的试验结果较接近,数值试验还给出了试件破坏过程图及应力分布图,再现了整个破坏过程,而且通过对模型中受拉区2个多单元信息剖线的提取,对剖线中不同位置点应力随加载步的变化情况进行了研究和分析,揭示了结构破坏的机理.数值试验结果对于深入了解钢筋和混凝土的联合受力规律有参考价值.
文摘为满足电能质量监测网存储与传输海量录波数据的需要,提出了提升格式的2维离散小波变换、多级树集合分裂(set partitioning in hierarchical tree,SPIHT)编码、算术编码相结合的数据压缩方法。为了有效降低数据的冗余度,该方法将采集的1维电能质量数据按整数倍周期排列为2维矩阵;采用提升格式的2维离散小波变换对数据进行压缩,然后对小波系数进行SPIHT编码,实现了对压缩性能的控制;最后采用算术编码进一步提高了压缩比。对几类常见的电能质量扰动数据进行了压缩实验,证明该方法具有较好的压缩性能。在不同压缩码率下对ATP-EMTP仿真模型得到的扰动数据进行了压缩实验,验证了该方法能通过控制压缩码率实现对压缩性能的控制。
