共查询到18条相似文献,搜索用时 955 毫秒
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落石灾害空间预测方法研究 总被引:3,自引:1,他引:2
对落石灾害进行准确空间预测,关键是求出落石最后一次与斜坡碰撞后的速度。基于落石的初始运动状态和成因,将落石类型概化为三种运动形式和六种基本破坏类型;结合运动过程可进一步划分,考虑斜坡形态,认为落石运动为坠落、滑落、斜抛、滚落和碰撞等状态复杂组合,对碰撞阶段进行详细分析,进而求出落石发生一种或多种运动后的速度,推求崩落距离;最后通过实例计算,验证了该法的合理性,为落石灾害的防治设计提供了依据。 相似文献
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丰沙铁路K49段边坡柔性防护选型与布置 总被引:1,自引:1,他引:0
针对丰沙铁路K49+160~+890段边坡特征,进行边坡防护方案的比选;根据现场的地形特征,划分不同防护区域开展落石分析,得到了落石的最大速度、弹跳高度、冲击能量等主要参数和落石运动的轨迹。根据分析结果,对不同的防护区域,进行柔性防护的选型及布置,既保证了防护效果,也节约了防护造价,且对铁路的安全运行影响很小。 相似文献
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我国山区公路沿线落石灾害问题突出。对于该灾害问题,目前我国尚缺乏有效的防护措施。对某公路沿线典型坡面,运用落石分析软件RocFall,分析落石的运动特征,包括落石的冲击动能、运动轨迹、落点位置、弹跳高度及它们的统计结果,探讨了有关设置拦石墙、铺设植被等被动防护措施的优化设计。 相似文献
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根据成昆铁路小平地隧道洞口岩体结构发育分布情况,结合三维激光扫描技术解释,确定落石的最大直径及方量;通过落石模拟计算,分析危岩体的运动特征,包括落石落下的最大可能位置、弹跳高度和能量等;分析采用被动防护网和钢棚洞相应的安全性,在保证铁路运营安全的前提下合理确定整治措施的规模,进而提出了洞口防治的综合处理措施。该设计思路、落石防护结构型式具有代表性,对今后类似工程的处理具有很好的参考价值。 相似文献
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为了进一步推广引导式柔性缓冲系统的工程应用,验证其防护性能和可靠性,依托渝黔线高速公路区间内某山区桥梁的高陡边坡落石防护工程,开展了工程设计计算,并对引导式柔性缓冲系统的防护性能进行分析。首先利用无人机航测建立防护区域的三维模型,明确了桥梁结构与边坡的空间位置关系和防护需求;基于危岩体实际特征对5个边坡纵断面开展了落石运动轨迹分析,根据弹跳高度和冲击动能包络值确定防护高度和防护能级指标;初步设计了引导式柔性缓冲系统的部件规格参数,建立了系统的有限元模型,并通过与关键部件试验数据对比验证了数值模型的有效性;基于离散元-有限元耦合算法,分别验算了相同初始动能的单体落石和多体落石2种工况下引导式柔性缓冲系统的内力,对比分析了有无防护时落石灾害对桥梁结构的侵害情况,从而验证了防护效果。计算结果表明:满足设计要求的引导式柔性缓冲系统能够有效抑制落石弹跳高度,从而避免落石侵限和撞击桥梁结构;引导式柔性缓冲系统关键部件内力响应均未超过设计限值,但不同工况下相同部件的内力峰值差异较大,因此,应采用各工况内力包络值进行设计,且关键构件的承载力安全储备系数不应小于1.2;防护全过程的耗能机制主要由系统塑性变形、系统阻尼以及落石与边坡和系统的摩擦碰撞3部分构成,其中塑性变形和摩擦碰撞耗能占主导地位,可分别按40%和60%的比例进行设计;拦截区段和引导区段的设计耗能比例系数可分别按0.7和0.3考虑,各区段中的主要耗能部件均为耗能器和环形网片。在此基础上,提出了基于能量匹配原理的引导式柔性缓冲系统的工程设计方法及流程,并建议了针对不同性能目标的多水准设计策略,以期发挥系统更大的防护潜能。 相似文献
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《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(6):675-703
Friction dampers of mechanical systems are frequently exposed to medium-frequency (M-F) dither generated in the surrounding environment. A dithered system of technical importance is the railway freight wagon with friction dampers in the primary suspension developing two-dimensional friction, where dither is generated by the rolling contact of wheel and rail. This paper presents some results of the investigation of the influence of dither on dry friction damping. This influence has been studied experimentally and theoretically, and the parameters of dither influencing dry friction damping have been indicated. An experimental set-up has been designed that allows investigating friction damping in the presence of dither. The experiments have shown that friction damping in the presence of the M-F dither behaves like viscous damping. This means that dither smoothes dry friction as far as damping is concerned. To investigate this phenomenon theoretically, a rheological model of dry friction has been proposed that is applicable to one- and two-dimensional friction. In the latter case, the model takes into account friction anisotropy. According to performed numerical simulations of freight wagon motion, with dither supplied to the model through measured vertical accelerations of axle boxes, smoothing dry friction by dither strongly influences ride dynamics of the wagon with friction dampers in the primary suspension. Smoothing dry friction by dither should be accounted for in numerical simulations of motion of vehicles with friction dampers in the primary suspension by employing a proper model of the two-dimensional friction and application of realistic dither generated by rolling contact. 相似文献
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针对现有运动规划算法大多只考虑障碍车当前状态,本文中提出一种基于前车运动轨迹预测的高速车辆运动规划算法。首先,融合考虑驾驶意图与基于车辆运动模型的方法对前车轨迹进行预测;然后,采用贝塞尔曲线(Bezier)规划主车运动轨迹,结合避撞过程中与前车碰撞风险概率,高速避撞车辆速度变化特点以及车辆运动稳定性等因素建立目标函数,并考虑车辆动力学与运动学约束,使用序列二次规划(SQP)方法对Bezier曲线的控制点和主车运动目标点位置进行优化求解,得到最优避撞运动轨迹;最后,以前车直行和换道两种工况为例,对主车的避撞运动轨迹进行规划,分析不同工况下主车避撞过程中的运动状态变化以及与前车碰撞风险概率变化。结果表明,所提出的运动规划算法能够保证车辆的避撞安全性与运动稳定性。 相似文献
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《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(1):441-466
SUMMARY On the basis of the brush-type tyre model the paper considers the interaction between steady-state rolling deformable wheel and flat road surface as well as corresponding force and moment characteristics of the wheel. At least two zones of sliding, anisotropic dry friction, sliding friction coefficient speed-dependent and instantaneous leap of the friction coefficient when transition from sliding to adhesion zone occurs, have been taken into account, as well as distributed peripheral mass of tyre, elasticity, pseudo-dry friction and damping properties in radial, tangential and lateral directions of the elements at the wheel periphery, including a visco-elastic belt. Vertical force distribution in the contact area is not supposed to be known in advance and follows from the calculation. As a result, sliding zone lengths, distributed forces in contact area, six components of generalized road reaction reduced to the wheel center, and rolling resistance moment are found as functions of vertical load, movement velocity, longitudinal and side slip, friction in contact area with road, stiffnesses, dry friction and damping in the tyre model elements and of distributed peripheral mass. A computer program developed in Fortran and results of calculations are of particular interest for qualitative analysis including steady rolling of studded tyre and also racing car and aircraft tyres which peripheral mass shows itself in a special way because of great movement velocities. 相似文献