为揭示近断层地震动作用下岩质边坡的动态响应规律与灾变机制,提出了一种间接边界元法(indirect boundary element method,简称IBEM)与离散元法(discrete element method,简称DEM)耦合的时域分析体系,建立了考虑岩土体非连续变形特征的...为揭示近断层地震动作用下岩质边坡的动态响应规律与灾变机制,提出了一种间接边界元法(indirect boundary element method,简称IBEM)与离散元法(discrete element method,简称DEM)耦合的时域分析体系,建立了考虑岩土体非连续变形特征的近断层-边坡系统非线性动力响应模拟方法。首先基于IBEM构建半无限域千米级近断层地震波场高精度数值模型;其次,结合格林函数理论与IBEM求解波场,推导DEM计算域边界等效地震荷载的显式表达,进而实现IBEM-DEM耦合系统的跨尺度能量传递;最终通过DEM求解米级岩质边坡的非线性动力响应,实现了从千米级断层到米级边坡的多尺度非线性地震动模拟方法体系。数值模拟与动态监测结果表明:IBEM-DEM耦合算法可精准表征近场地震波传播的频散特性与能量衰减规律;近断层地震荷载作用下,软弱夹层首先发生渐进式剪切破坏,其强度劣化导致贯通性破裂面的形成,并引致滑体沿剪切面加速失稳,产生显著位移与速度响应,最终在坡脚形成典型碎屑堆积体;滑体表层速度显著高于底层,表层平均速度达到底层平均速度的3.6倍,其中滑体表层X向和Z向的速度分量峰值分别达到4.98 m/s和5.92 m/s,呈现出明显的趋表效应;滑体监测点从初始坡面位置到最终堆积体位置的X向和Z向最大位移分别可达41 m和35 m,时程表现出典型阶跃式增长特征,反映出滑体在动能与势能交替转换中的突跃式滑移行为。IBEM-DEM耦合方法构建了从岩体破裂到滑坡成灾的全过程演化序列,为近断层地震动诱发滑坡的动力灾变分析提供了创新性分析方法体系,并为复杂地质条件下滑坡机制的识别及地震灾害的防控提供了理论依据与技术支持。展开更多
The accurate measurement of the fill level in the ball mill has not been resolved because of the interplay of many variable factors, which led the mill to be operated under the uneconomical condition and lost a lot of...The accurate measurement of the fill level in the ball mill has not been resolved because of the interplay of many variable factors, which led the mill to be operated under the uneconomical condition and lost a lot of energy. At present, some methods, such as vibration method and acoustic method, have been applied for measuring the fill level by the researchers. Aiming at the problem of the traditional methods for measuring the fill level, that is, the feature variables of the fill level suffer the influences of the ball load and the water content of the coal, a novel method to measure the fill level is proposed and a possible relation between the fill level and the angular position of the maximum vibration point on the mill shell is investigated. The angular positions of the maximum vibration point on the mill shell for different fill level cases are calculated theoretically under two assumptions, respectively. Meanwhile the charge motions of the mill for different fill level cases are simulated with the discrete element method （DEM）. And the simulation results are verified by comparing the motion trajectories of steel balls and power draft of the mill. The simulated movement trajectories of the outmost layer steel balls in the mill are monitored and analyzed to obtain the angular positions of the maximum vibration point on the mill shell. Both the results of the theoretical calculation and the 3D DEM simulation show that the position of the maximum vibration point on the mill shell moves to a lower angular positions as the fill level decreasing, which provides a new idea for measuring the filllevel accurately.展开更多
高位滑坡对建筑集群的冲击破坏时常导致严重的人员伤亡,基于光滑粒子流体动力学-离散元法-有限元法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM)耦合的数值模型,开展了高位滑坡对框...高位滑坡对建筑集群的冲击破坏时常导致严重的人员伤亡,基于光滑粒子流体动力学-离散元法-有限元法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM)耦合的数值模型,开展了高位滑坡对框架结构建筑群的冲击过程、建筑结构破坏机理、冲击力时程与框架柱关键点应力和弯矩等动力机制研究。研究结果表明:SPH-DEM-FEM耦合数值方法能够有效地模拟碎石土滑坡中土(SPH)石(DEM)混合物的抛射弹跳、爬高绕流冲击运动过程。考虑了常规建筑垂直、平行于滑坡流向的三排建筑组合布局,位于滑坡近端的纵向排列建筑表现为连续性倾倒破坏,横向排列的建筑则呈现整体倾倒破坏;因前排建筑群对滑坡冲击能量的耗散及滑坡自身摩擦耗能,位于滑坡后端建筑表现为引流面墙体和前排柱发生局部破坏,结构保持稳定,损毁程度依次为上游无建筑缓冲耗能的建筑>有横向排列的建筑>有纵向排列的建筑;纵向、横向排列的建筑冲击力衰减幅度分别31%、21%。横向框架建筑整体倾倒的损毁机制表现为框架柱的直接剪断或节点塑形铰链失效;纵向框架建筑连续性倾倒的损毁机制表现为前排框架柱的失效引起后排框架柱轴向压力和极限弯矩增加,持续冲击荷载超过其极限弯矩致使后排框架柱发生弯曲破坏,最终结构倾倒。系统能量在动能、内能和摩擦耗能间转化,其中摩擦耗能占65.5%,结构耗能占23.6%,动能快速下降与内能急剧增加是建筑破坏的关键特征。展开更多
随着山区高速公路建设的迅速推进,弃渣场的稳定性及潜在失稳灾害评估日益受到重视。具有巨大能量的滑坡体,可能会冲击破坏沿途的结构物进而威胁生命财产安全。充分发挥利用物质点法(material point method,MPM)可以对连续介质大变形过...随着山区高速公路建设的迅速推进,弃渣场的稳定性及潜在失稳灾害评估日益受到重视。具有巨大能量的滑坡体,可能会冲击破坏沿途的结构物进而威胁生命财产安全。充分发挥利用物质点法(material point method,MPM)可以对连续介质大变形过程模拟和离散元法(digital elevation model,DEM)能够精准的接触判断优势,MPM-DEM耦合算法可有效解决滑坡体与复杂地形、沿线结构物之间的相互作用问题。文章基于GPU并行高性能计算软件CoSim中的MPM-DEM耦合算法,实现了对弃渣场边坡稳定性、潜在失稳灾害的动力学分析。研究首先以散粒体冲击结构物的算例,验证了该算法的合理性与准确性;在此基础上,以云南某高速公路弃渣场为研究案例,进一步计算其稳定性系数,并预测潜在失稳灾害的影响范围与危害程度。结果表明,该弃渣场边坡目前处于稳定状态;若发生失稳,滑坡体将对下游高速公路桥桩产生巨大冲击力。该耦合算法在弃渣场边坡稳定性与失稳灾害动力学分析中具备显著优势,能够实现边坡“稳定性→大变形→流动→堆积”的全过程分析。展开更多
Wellbore breakout is one of the critical issues in drilling due to the fact that the related problems result in additional costs and impact the drilling scheme severely.However,the majority of such wellbore breakout a...Wellbore breakout is one of the critical issues in drilling due to the fact that the related problems result in additional costs and impact the drilling scheme severely.However,the majority of such wellbore breakout analyses were based on continuum mechanics.In addition to failure in intact rocks,wellbore breakouts can also be initiated along natural discontinuities,e.g.weak planes and fractures.Furthermore,the conventional models in wellbore breakouts with uniform distribution fractures could not reflect the real drilling situation.This paper presents a fully coupled hydro-mechanical model of the SB-X well in the Tarim Basin,China for evaluating wellbore breakouts in heavily fractured rocks under anisotropic stress states using the distinct element method(DEM)and the discrete fracture network(DFN).The developed model was validated against caliper log measurement,and its stability study was carried out by stress and displacement analyses.A parametric study was performed to investigate the effects of the characteristics of fracture distribution(orientation and length)on borehole stability by sensitivity studies.Simulation results demonstrate that the increase of the standard deviation of orientation when the fracture direction aligns parallel or perpendicular to the principal stress direction aggravates borehole instability.Moreover,an elevation in the average fracture length causes the borehole failure to change from the direction of the minimum in-situ horizontal principal stress(i.e.the direction of wellbore breakouts)towards alternative directions,ultimately leading to the whole wellbore failure.These findings provide theoretical insights for predicting wellbore breakouts in heavily fractured rocks.展开更多
文摘为揭示近断层地震动作用下岩质边坡的动态响应规律与灾变机制,提出了一种间接边界元法(indirect boundary element method,简称IBEM)与离散元法(discrete element method,简称DEM)耦合的时域分析体系,建立了考虑岩土体非连续变形特征的近断层-边坡系统非线性动力响应模拟方法。首先基于IBEM构建半无限域千米级近断层地震波场高精度数值模型;其次,结合格林函数理论与IBEM求解波场,推导DEM计算域边界等效地震荷载的显式表达,进而实现IBEM-DEM耦合系统的跨尺度能量传递;最终通过DEM求解米级岩质边坡的非线性动力响应,实现了从千米级断层到米级边坡的多尺度非线性地震动模拟方法体系。数值模拟与动态监测结果表明:IBEM-DEM耦合算法可精准表征近场地震波传播的频散特性与能量衰减规律;近断层地震荷载作用下,软弱夹层首先发生渐进式剪切破坏,其强度劣化导致贯通性破裂面的形成,并引致滑体沿剪切面加速失稳,产生显著位移与速度响应,最终在坡脚形成典型碎屑堆积体;滑体表层速度显著高于底层,表层平均速度达到底层平均速度的3.6倍,其中滑体表层X向和Z向的速度分量峰值分别达到4.98 m/s和5.92 m/s,呈现出明显的趋表效应;滑体监测点从初始坡面位置到最终堆积体位置的X向和Z向最大位移分别可达41 m和35 m,时程表现出典型阶跃式增长特征,反映出滑体在动能与势能交替转换中的突跃式滑移行为。IBEM-DEM耦合方法构建了从岩体破裂到滑坡成灾的全过程演化序列,为近断层地震动诱发滑坡的动力灾变分析提供了创新性分析方法体系,并为复杂地质条件下滑坡机制的识别及地震灾害的防控提供了理论依据与技术支持。
基金supported by National Natural Science Foundation of China (Grant No. 50775035)New Doctor Teacher Foundation of Southeast University of China (Grant No. 9202000024)
文摘The accurate measurement of the fill level in the ball mill has not been resolved because of the interplay of many variable factors, which led the mill to be operated under the uneconomical condition and lost a lot of energy. At present, some methods, such as vibration method and acoustic method, have been applied for measuring the fill level by the researchers. Aiming at the problem of the traditional methods for measuring the fill level, that is, the feature variables of the fill level suffer the influences of the ball load and the water content of the coal, a novel method to measure the fill level is proposed and a possible relation between the fill level and the angular position of the maximum vibration point on the mill shell is investigated. The angular positions of the maximum vibration point on the mill shell for different fill level cases are calculated theoretically under two assumptions, respectively. Meanwhile the charge motions of the mill for different fill level cases are simulated with the discrete element method （DEM）. And the simulation results are verified by comparing the motion trajectories of steel balls and power draft of the mill. The simulated movement trajectories of the outmost layer steel balls in the mill are monitored and analyzed to obtain the angular positions of the maximum vibration point on the mill shell. Both the results of the theoretical calculation and the 3D DEM simulation show that the position of the maximum vibration point on the mill shell moves to a lower angular positions as the fill level decreasing, which provides a new idea for measuring the filllevel accurately.
文摘高位滑坡对建筑集群的冲击破坏时常导致严重的人员伤亡,基于光滑粒子流体动力学-离散元法-有限元法(smoothed particle hydrodynamics-discrete element method-finite element method,SPH-DEM-FEM)耦合的数值模型,开展了高位滑坡对框架结构建筑群的冲击过程、建筑结构破坏机理、冲击力时程与框架柱关键点应力和弯矩等动力机制研究。研究结果表明:SPH-DEM-FEM耦合数值方法能够有效地模拟碎石土滑坡中土(SPH)石(DEM)混合物的抛射弹跳、爬高绕流冲击运动过程。考虑了常规建筑垂直、平行于滑坡流向的三排建筑组合布局,位于滑坡近端的纵向排列建筑表现为连续性倾倒破坏,横向排列的建筑则呈现整体倾倒破坏;因前排建筑群对滑坡冲击能量的耗散及滑坡自身摩擦耗能,位于滑坡后端建筑表现为引流面墙体和前排柱发生局部破坏,结构保持稳定,损毁程度依次为上游无建筑缓冲耗能的建筑>有横向排列的建筑>有纵向排列的建筑;纵向、横向排列的建筑冲击力衰减幅度分别31%、21%。横向框架建筑整体倾倒的损毁机制表现为框架柱的直接剪断或节点塑形铰链失效;纵向框架建筑连续性倾倒的损毁机制表现为前排框架柱的失效引起后排框架柱轴向压力和极限弯矩增加,持续冲击荷载超过其极限弯矩致使后排框架柱发生弯曲破坏,最终结构倾倒。系统能量在动能、内能和摩擦耗能间转化,其中摩擦耗能占65.5%,结构耗能占23.6%,动能快速下降与内能急剧增加是建筑破坏的关键特征。
文摘随着山区高速公路建设的迅速推进,弃渣场的稳定性及潜在失稳灾害评估日益受到重视。具有巨大能量的滑坡体,可能会冲击破坏沿途的结构物进而威胁生命财产安全。充分发挥利用物质点法(material point method,MPM)可以对连续介质大变形过程模拟和离散元法(digital elevation model,DEM)能够精准的接触判断优势,MPM-DEM耦合算法可有效解决滑坡体与复杂地形、沿线结构物之间的相互作用问题。文章基于GPU并行高性能计算软件CoSim中的MPM-DEM耦合算法,实现了对弃渣场边坡稳定性、潜在失稳灾害的动力学分析。研究首先以散粒体冲击结构物的算例,验证了该算法的合理性与准确性;在此基础上,以云南某高速公路弃渣场为研究案例,进一步计算其稳定性系数,并预测潜在失稳灾害的影响范围与危害程度。结果表明,该弃渣场边坡目前处于稳定状态;若发生失稳,滑坡体将对下游高速公路桥桩产生巨大冲击力。该耦合算法在弃渣场边坡稳定性与失稳灾害动力学分析中具备显著优势,能够实现边坡“稳定性→大变形→流动→堆积”的全过程分析。
基金supported by National Natural Science Foundation of China(Grant Nos.52074312 and 52211530097)CNPC Science and Technology Innovation Foundation(Grant No.2021DQ02-0505).
文摘Wellbore breakout is one of the critical issues in drilling due to the fact that the related problems result in additional costs and impact the drilling scheme severely.However,the majority of such wellbore breakout analyses were based on continuum mechanics.In addition to failure in intact rocks,wellbore breakouts can also be initiated along natural discontinuities,e.g.weak planes and fractures.Furthermore,the conventional models in wellbore breakouts with uniform distribution fractures could not reflect the real drilling situation.This paper presents a fully coupled hydro-mechanical model of the SB-X well in the Tarim Basin,China for evaluating wellbore breakouts in heavily fractured rocks under anisotropic stress states using the distinct element method(DEM)and the discrete fracture network(DFN).The developed model was validated against caliper log measurement,and its stability study was carried out by stress and displacement analyses.A parametric study was performed to investigate the effects of the characteristics of fracture distribution(orientation and length)on borehole stability by sensitivity studies.Simulation results demonstrate that the increase of the standard deviation of orientation when the fracture direction aligns parallel or perpendicular to the principal stress direction aggravates borehole instability.Moreover,an elevation in the average fracture length causes the borehole failure to change from the direction of the minimum in-situ horizontal principal stress(i.e.the direction of wellbore breakouts)towards alternative directions,ultimately leading to the whole wellbore failure.These findings provide theoretical insights for predicting wellbore breakouts in heavily fractured rocks.
