Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed...Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed with a cushion layer using PFC-FLAC.The granular cushion is modeled as an aggregate of discrete non-cohesion particles,while the concrete plate and the beam are modeled as zones.The falling rock with different sphericities and impact angles is modeled as a rigid assembly.The numerical model is validated by comparing the simulation results with experimental and numerical results from previous literature.This model is applied to analyze the effects of rock shape and impact angle on the dynamic interaction effects between falling rock and cushioned rock shed,including the impact force,transmitted bottom force,penetration depth,and plate deflection.The numerical results show that the variation in the falling rock’s shape has different effects on the falling rock with different impact angles.These findings could support rock shed design by revealing the limitations of the assumptions in the past research,which may result in unsafe rock sheds for some rockfall cases.展开更多
With recent advances in numerical modeling, design of underground structures increasingly relies on numerical modeling-based analysis approaches. While modeling tools like the discrete element method(DEM) and the comb...With recent advances in numerical modeling, design of underground structures increasingly relies on numerical modeling-based analysis approaches. While modeling tools like the discrete element method(DEM) and the combined finite-discrete element method(FDEM) are useful for investigating small-scale damage processes, continuum models remain the primary practical tool for most field-scale problems.The results obtained from such models are significantly dependent on the selection of an appropriate yield criterion and dilation angle. Towards improving its capabilities in handling mining-related problems, the authors have previously developed a new yield criterion(called progressive S-shaped criterion). The focus of the current study is to demonstrate its use in modeling rock pillars through a comparative analysis against four other yield criteria. In addition to the progressive S-shaped criterion,only one out of the four other criteria predicted a trend in strength consistent with an empirical pillar strength database compiled from the literature. Given the closely-knit relationship between yield criteria and dilation angle in controlling the overall damage process, a separate comparison was conducted using a mobilized dilation model, a zero degree dilation angle and a constant non-zero dilation angle. This study also investigates the impact of meso-scale heterogeneity in mechanical properties on the overall model response by assigning probability distributions to the input parameters. The comparisons revealed that an isotropic model using a combination of progressive S-shaped criterion and mobilized dilation angle model is sufficient in capturing the behaviors of rock pillars. Subsequently, the pillar model was used to assess the effect of L/W(length/width) ratio on the peak strength.展开更多
为进一步了解结构受力情况,为明洞结构设计提供依据,采用动力有限元方法,对客运专线双线单压式拱形明洞落石冲击下结构力学响应进行了研究.首先,以竖直下落冲击为基本工况,从落石与洞顶回填土的相互作用及运动轨迹入手,分析了结构的应...为进一步了解结构受力情况,为明洞结构设计提供依据,采用动力有限元方法,对客运专线双线单压式拱形明洞落石冲击下结构力学响应进行了研究.首先,以竖直下落冲击为基本工况,从落石与洞顶回填土的相互作用及运动轨迹入手,分析了结构的应力、应变、应变率、位移、速度、加速度等作用效应响应;其次,根据落石、回填土及结构间能量的转化与传递规律,结合结构及基底应力响应,阐述了回填土和混凝土填充材料对落石冲击的缓冲和对结构的保护作用机理,以及边墙形式对基底及仰拱受力的影响;最后进行了45°斜向冲击响应分析并与基本工况进行了对比.研究结果表明:所设计的明洞结构可以承受竖向700 k J的落石冲击能量,拱顶、拱肩及墙身内侧和耳墙墙址等部位是相对受力不利位置,回填方式和直墙式拱墙形式有待进一步研究优化;冲击引起的结构应变率响应介于1×10^(-3)~1×10^(-2)s^(-1),与地震引起的响应范围相同;在本研究工况下,45°斜向冲击作用效应总体上小于竖直冲击.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.41941017 and U1702241).
文摘Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed with a cushion layer using PFC-FLAC.The granular cushion is modeled as an aggregate of discrete non-cohesion particles,while the concrete plate and the beam are modeled as zones.The falling rock with different sphericities and impact angles is modeled as a rigid assembly.The numerical model is validated by comparing the simulation results with experimental and numerical results from previous literature.This model is applied to analyze the effects of rock shape and impact angle on the dynamic interaction effects between falling rock and cushioned rock shed,including the impact force,transmitted bottom force,penetration depth,and plate deflection.The numerical results show that the variation in the falling rock’s shape has different effects on the falling rock with different impact angles.These findings could support rock shed design by revealing the limitations of the assumptions in the past research,which may result in unsafe rock sheds for some rockfall cases.
基金funded by The National Institute for Occupational Safety and Health,USA(NIOSH)(Grant No.200-2016-90154)
文摘With recent advances in numerical modeling, design of underground structures increasingly relies on numerical modeling-based analysis approaches. While modeling tools like the discrete element method(DEM) and the combined finite-discrete element method(FDEM) are useful for investigating small-scale damage processes, continuum models remain the primary practical tool for most field-scale problems.The results obtained from such models are significantly dependent on the selection of an appropriate yield criterion and dilation angle. Towards improving its capabilities in handling mining-related problems, the authors have previously developed a new yield criterion(called progressive S-shaped criterion). The focus of the current study is to demonstrate its use in modeling rock pillars through a comparative analysis against four other yield criteria. In addition to the progressive S-shaped criterion,only one out of the four other criteria predicted a trend in strength consistent with an empirical pillar strength database compiled from the literature. Given the closely-knit relationship between yield criteria and dilation angle in controlling the overall damage process, a separate comparison was conducted using a mobilized dilation model, a zero degree dilation angle and a constant non-zero dilation angle. This study also investigates the impact of meso-scale heterogeneity in mechanical properties on the overall model response by assigning probability distributions to the input parameters. The comparisons revealed that an isotropic model using a combination of progressive S-shaped criterion and mobilized dilation angle model is sufficient in capturing the behaviors of rock pillars. Subsequently, the pillar model was used to assess the effect of L/W(length/width) ratio on the peak strength.
文摘为进一步了解结构受力情况,为明洞结构设计提供依据,采用动力有限元方法,对客运专线双线单压式拱形明洞落石冲击下结构力学响应进行了研究.首先,以竖直下落冲击为基本工况,从落石与洞顶回填土的相互作用及运动轨迹入手,分析了结构的应力、应变、应变率、位移、速度、加速度等作用效应响应;其次,根据落石、回填土及结构间能量的转化与传递规律,结合结构及基底应力响应,阐述了回填土和混凝土填充材料对落石冲击的缓冲和对结构的保护作用机理,以及边墙形式对基底及仰拱受力的影响;最后进行了45°斜向冲击响应分析并与基本工况进行了对比.研究结果表明:所设计的明洞结构可以承受竖向700 k J的落石冲击能量,拱顶、拱肩及墙身内侧和耳墙墙址等部位是相对受力不利位置,回填方式和直墙式拱墙形式有待进一步研究优化;冲击引起的结构应变率响应介于1×10^(-3)~1×10^(-2)s^(-1),与地震引起的响应范围相同;在本研究工况下,45°斜向冲击作用效应总体上小于竖直冲击.
