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崩塌落石其性质结构复杂、作用因素多样,仍存在众多难题尚未解决,特别是铁路桥梁工程受崩塌落石冲击后的动力响应是当下尚未解决的关键难题之一。本文以拉林铁路某段桥梁工程典型工点为例,运用Rocfall仿真计算,着重就同一结构面不同坡面倾角岩体崩塌落石运动过程对桥梁结构破坏作用产生的平动速度、弹跳高度、总动能等进行动态变化分析,基于上述分析,结合模型试验加速度响应测试,利用SPECTR计算程序对其加速度、速度和位移动力反应谱特性进行分析评价。研究结果:(1)危岩落石运动方式主要与坡面倾角的大小有关,坡面倾角较大,落石从坡面以滚落运动为主;坡面倾角较小,落石从坡面以滑落运动为主。(2)危岩落石受到动摩擦力作用、恢复系数的影响,在每次撞击混凝土桥面的过程中速度都会呈非线性减小。(3)岩体崩塌落石对结构物撞击产生较大的短时加速度脉冲效应,当结构物基频相同时,落石从坡面运动的空间变化是引起振动特性响应差异显著的主要因素。(4)速度响应时程曲线近似呈"余弦"型,总体上表现出随着时间增加呈现非线性增减变化,且大角度坡面倾角其速度响应峰值略大于小角度坡面倾角,落石对结构物的撞击时间效应与坡面倾角相关,坡面倾... 相似文献
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崩塌落石其性质结构复杂、作用因素多样,仍存在众多难题尚未解决,特别是铁路桥梁工程受崩塌落石冲击后的动力响应是当下尚未解决的关键难题之一。本文以拉林铁路某段桥梁工程典型工点为例,运用Rocfall仿真计算,着重就同一结构面不同坡面倾角岩体崩塌落石运动过程对桥梁结构破坏作用产生的平动速度、弹跳高度、总动能等进行动态变化分析,基于上述分析,结合模型试验加速度响应测试,利用SPECTR计算程序对其加速度、速度和位移动力反应谱特性进行分析评价。研究结果:(1)危岩落石运动方式主要与坡面倾角的大小有关,坡面倾角较大,落石从坡面以滚落运动为主;坡面倾角较小,落石从坡面以滑落运动为主。(2)危岩落石受到动摩擦力作用、恢复系数的影响,在每次撞击混凝土桥面的过程中速度都会呈非线性减小。(3)岩体崩塌落石对结构物撞击产生较大的短时加速度脉冲效应,当结构物基频相同时,落石从坡面运动的空间变化是引起振动特性响应差异显著的主要因素。(4)速度响应时程曲线近似呈"余弦"型,总体上表现出随着时间增加呈现非线性增减变化,且大角度坡面倾角其速度响应峰值略大于小角度坡面倾角,落石对结构物的撞击时间效应与坡面倾角相关,坡面倾角越大,触发时间效应越明显,受振有效持续时间越久。(5)阻尼比取值介于10%~20%时,反应谱曲线衰减幅度最为显著,介于30%~40%时,加速度反应谱曲线表现明显分异,设计宜鼓励增大桥梁的柔性抗冲击性能。上述研究成果,对于新建川藏铁路山区桥梁基础施工具有工程指导意义。 相似文献
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针对高陡边坡落石防护,提出了一种引导式落石防护网系统技术。通过落石运动路径全历程的动能特征分析,建立了系统的主动耗能控制方程,明确了防护系统的耗能控制原理,提出了防护技术措施,构建了引导式落石防护网系统的结构模型。设计了防护能量为2500kJ的足尺引导式柔性防护网系统模型,开展了场地冲击试验,系统试验模型铺设于破碎岩体发育的高陡坡面,铺设宽130m,高82m,纵坡约60°。考虑有、无防护系统,开展了6个落石冲击试验工况,对落石轨迹特征、冲击动能进行了对比分析。研究发现,与落石自然滚落相比,设置引导防护系统后,落石沿坡面的运动时间延长超80%,落石的碰撞次数增加约5倍,弹跳高度降幅超80%,横向偏移量降幅超50%,触底动能和坡底逸出距离均减少约65%,综合耗能比例高达89%,新系统实现了对落石崩塌灾害的"拦截-压制-引导"综合控制。 相似文献
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主要介绍小尖山隧道出口正洞的贯通施工采取了先清除洞顶危岩落石,再施工洞顶被动防护网及X019县道上方拦石网,然后采用三台阶临时仰拱法先贯通上台阶,再贯通中台阶,再施作洞顶截水天沟及洞口防护工程,最后开挖贯通下台阶的综合施工方法和合理的施工顺序,为今后解决类似工程问题提供了一定的借鉴。 相似文献
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我国西南地区多喀斯特地貌,其中广西贺州地区较为典型,易形成孤峰陡崖,在地质营力及风化的作用下易形成危岩落石。孤峰地区进行工程建设时,危岩落石是危及人民生命财产、运营安全的最主要风险源之一。以广西贺州地区某铁路高边坡危石整治为背景,分析了危岩体的基本特征及失稳模式、危岩体稳定计算方法、零星落石弹跳轨迹,讨论了支顶、拦石墙、主被动网的防护方案,分析了计算结果。根据计算结果,对该高边坡危石提出建议了整治方案的建议。 相似文献
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介绍了危岩边坡落石的形成条件,阐述了落石规模、几何以及落石轨迹和频率,并提出了SNS主动防护系统,同时对该系统作了简单论述,指出SNS主动防护系统具有良好的经济和社会效益,必将得到广泛应用。 相似文献
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地下工程的口部易受到崩塌、落石灾害威胁,一般可通过落石防护网进行防护。防落石拖挂网是一种新型的落石防护网,其“因势利导,以柔克刚”的结构形式可以有效降低结构内力峰值,减少建设和维护成本。为了探索防落石拖挂网在落石冲击下的变形模式和结构内的荷载传递规律,通过模型试验对防落石拖挂网的防护性能进行研究。研究发现,未布置拖挂网时落石直接飞跃到试验边坡底部,布置拖挂网后落石飞行高度明显降低,达到了控制落石运动轨迹的目的。根据模型试验构建了防落石拖挂网的数值计算模型,并从防护网形态、落石运动轨迹和落石出射速率等方面与试验进行了对比验证,为下一步防落石拖挂网的耗能机理和传载规律研究奠定了基础。 相似文献
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滚石灾害在工程施工过程中对施工人员、设备和构筑物具有较大的威胁,因此研究滚石的运动特性及其冲击力显得非常重要。基于刚体运动学原理建立滚石运动特性的计算方法,通过与数值仿真结果对比来验证其合理性,同时滚石的运动参数作为计算其对构筑物冲击力的基础参数。在考虑滚石自转的基础上,基于冲量定理提出滚石冲击力的计算方法,并结合弹性力学理论解决计算中的撞击时间难以确定的问题。利用提出的方法对长河坝环境边坡的滚石运动特性及冲击力进行分析,计算结果表明:滚石运动过程最大弹跳高度可达25 m、最大平动速度和转动速度分别可达到57 m/s及350 rad/s,滚石运动受地形影响较大。结合运动参数分析结果和冲击力计算模型确定滚石对不同部位构筑物的冲击力数值,冲击力计算结果为构筑物位置的选择及灾害防治提供了一定的参考。 相似文献
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The modern day practice does not give due respect to passive and natural environment control measures in buildings. With modern materials and technology, the buildings of present architectural style results in high energy consumption, in an attempt to provide thermal comfort indoors. The vernacular architecture at any place on the other hand has evolved through ages by consistent and continuous effort for more efficient and perfect solutions. The authors have conducted a qualitative analysis of the passive environment control system of vernacular residential architecture of Kerala that is known for ages for its use of natural and passive methods for a comfortable indoor environment. The orientation of building, internal arrangement of spaces, the presence of internal courtyard, use of locally available materials and special methods of construction, etc. have together created the indoor environment. A quantitative analysis was also carried out based on field experiments by recording thermal comfort parameters in a selected building. The study has provided positive results confirming that the passive environment control system employed in Kerala vernacular architecture is highly effective in providing thermal comfort indoors in all seasons. 相似文献
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Chris P. Pantelides Shyh-Rong Tzan Paul A. Nelson 《The Structural Design of Tall and Special Buildings》1995,4(2):127-136
In recent years, passive as well as active control methods have been implemented for structural motion reduction of tall buildings in earthquakes. An active control method for the inelastic response of tall buildings is presented. The proposed method of continuous pulse control uses closed-loop feedback control as a combination of two algorithms. The first is a linear control algorithm-instantaneous optimal control-and the second is a pulse control algorithm-the pulse control algorithm-which applies a corrective pulse when a prespecified structural velocity threshold is exceeded. The control forces required by active control systems to reduce the seismic response of tall buildings can be quite large. On the other hand, passive control systems such as the viscoelastic dampers do not require external energy for their operation. The possibility of combining viscoelastic dampers and the active bracing system for reducing the required control forces is examined. The combination of passive and active devices improves safety, serviceability and the comfort of the building's occupants. 相似文献
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落石运动模式与运动特征现场试验研究 总被引:1,自引:0,他引:1
落石试验是寻找落石运动敏感因素、探求运动规律和获取运动参数的较好方法.为厘清落石形状、块度大小和运动模式对其运动特征的影响规律,进行了112块落石现场试验;以落石形状、质量和运动弹跳次数为变量,统计分析了水平运动距离、运动速度的变动规律.试验结果表明:不管何种形状落石,运动模式均为滚动和弹跳,无明显滑动段;切坡平台和公... 相似文献
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介绍了边坡滚石地质灾害的产生条件,对滚石的能量及运动轨迹进行了分析,然后介绍了滚石常用的防护方式,并针对具体工程实例对柔性防护系统做了介绍。 相似文献
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A.K. Verma Sahil Sardana Pushpendra Sharma Lal Dinpuia T.N. Singh 《岩石力学与岩土工程学报(英文版)》2019,11(1):146-158
Rockfall is one of severe natural hazards that are frequently reported in northeast region of India. It carries rock block falling from the cliff with high velocities and energies which can result in damages to vehicles, disruption to transportation, injuries and fatalities. The massive rockfall event which occurred in April 2017 on the highway NH-44A, near Lengpui Airport, blocked the traffic for 1 d, and fortunately, no casualties were reported as the event occurred in the night. This is the only highway connecting the Aizawl city to the airport and the region is highly prone to rockfall events. Hence assessment of rockfall along this highway is necessary. In the current study, rockfall hazard assessment has been carried out on three locations by rockfall hazard rating system (RHRS). During pre-failure analysis, the result shows that most hazardous slopes have RHRS score of 639. The slopes were found to be vulnerable and later on the rockfall activity occurred. Three-dimensional (3D) stability analysis has been carried out using 3DEC software package to analyze the failure behavior and to decide the rockfall-prone zone (unstable blocks) for slope. The total displacement of 2.24 cm and velocity of 2.25 mm/s of the failed block have been observed in the numerical analysis. Further, the rockfall vulnerable zone (unstable blocks) is considered to determine the parameters such as run-out distance, bounce height and energies of the falling rock blocks. The maximum total kinetic energy of 5047 kJ has been observed in the numerical analysis with the maximum run-out distance up to 18 m. 相似文献