共查询到19条相似文献，搜索用时 234 毫秒
1.
采用当前方法分析地震后泥石流灾害柔性防治冲击的动力响应时,不能准确的分析柔性防护体系随时间变化产生的位移变化以及落石在冲击过程中对柔性防护体系的冲击时间与能量关系,得到的分析结果与实际不符,存在分析准确率低的问题。提出地震后泥石流灾害柔性防治冲击动力响应分析方法 ,构建防护体系有限元模型,利用Lagrange描述方法在连续介质力学的基础上构建撞击系统对应的控制方程以及弹塑性材料接触力学模型,在以上两个模型的基础上通过ANSYS/LS-DYNA软件模拟甘肃省陇南市某泥石流治理工程环境,通过分析柔性防护体系随时间变化产生的位移变化以及落石在冲击过程中对柔性防护体系的冲击时间与能量关系,实现地震后泥石流灾害柔性防治冲击动力的响应分析。实验结果表明,所提方法的的分析准确率较高。 相似文献
2.
《地震工程与工程振动》2021,41(2)
沙尘暴本质为风携沙的气固两相流,对建构(筑)物产生的作用力由风荷载和沙粒的冲击荷载组成。遗憾的是,目前的结构抗风设计仅考虑风荷载作用,忽略了沙粒对结构的冲击效应,且因为研究手段有限,目前的研究成果不足以全面地反映风沙对结构物冲击行为的机理。文中将沙粒的冲击行为研究现状分为3部分:冲击前沙粒的运动、冲击时的接触碰撞以及冲击后的冲蚀磨损,以此概述了风沙对结构物冲击行为的研究现状,并总结了目前研究中出现的主要问题,最后提出将数学模型推导、风沙风洞试验、现场实测、数值模拟4个方面系统结合,综合开展风沙流及沙粒对结构的冲击机理及冲击作用研究的展望。 相似文献
3.
多孔金属材料是一种新型功能和结构材料,具有良好的吸能、减震和阻尼特性。根据多孔金属材料的吸能特性,研究了多孔金属材料耗散能量准则,分析了多孔金属材料应用于冲击地压巷道支护的可行性。基于多孔金属材料的耗散能量准则,首次建立了刚柔吸能支护结构模型,将多孔金属材料应用于冲击地压巷道支护结构中,并利用FLAC 3D计算软件,对刚柔吸能支护巷道冲击破坏进行数值模拟。研究结果表明,刚柔吸能支护可高效吸收冲击能量、缓冲作用荷载及大幅度提高巷道围岩的可靠程度,是防治冲击地压发生和降低动力灾害的一种有效方法。 相似文献
4.
随着中国汽车工业的发展,大量废旧轮胎带来的"黑色污染"问题日益显著。提出一种采用废旧轮胎柱(Scrap tire columns,STC)的加筋土结构,并初步探究其作为基础减隔振材料的可行性。通过室内水平循环剪切试验和竖向激振试验研究STC加筋砂(STCRS)的水平循环剪切和竖向激振特性。结果表明,最大剪应变为1%时STCRS的等效阻尼比未加筋前增加约10%,等效动剪切模量减小20%~25%,水平向减振性能得以提高;STCRS的竖向加速度衰减呈现出速度快、幅值大的特点,竖向减振效果较未加筋砂显著提高。STC加筋砂作为基础减振材料是可行的,且为原形废旧轮胎的资源化利用提供新思路。 相似文献
5.
泥石流冲击荷载的时频分析方法及应用 总被引：1，自引：0，他引：1
泥石流的能量转化主要集中于运动过程中,泥石流冲击压力随时间变化的过程是其能量不断变化的综合表现。本文分析了泥石流能量转化过程及冲击荷载的紊流形态,并根据其脉动特性,将泥石流冲击荷载作为信号进行研究。以大型泥石流模型试验为基础,利用小波时频分析方法将试验测取的泥石流冲击荷载映射为时间与频率的联合信号,得到同一时间9个频段内的能量强度。从冲击荷载的能量分布可以看出,稀性泥石流95%以上的波动能集中在低频段内（0～6.25Hz）,从而为深入研究泥石流冲击机制及防治结构动态荷载设计提供了一些理论依据。 相似文献
6.
泥石流防撞墩冲击力理论计算方法 总被引：4，自引：0，他引：4
在西部泥石流多发区,交通线路经常需要穿越泥石流沟,设置在泥石流沟床中的桥墩容易遭受泥石流大块石的冲击,为此,常常在其前端设置泥石流防撞墩,以达到保护桥墩的目的。防撞墩设计的关键参数是泥石流大块石的冲击力。目前,有关泥石流冲击力的计算方法都比较粗糙,计算结果与实际情况不符。本文以Thornton理想弹塑性接触模型为基础,并考虑防撞墩的弯矩变形特性,根据能量守恒定律,推导了泥石流大块石冲击力的计算公式。结果表明,考虑结构弹塑性特性后,泥石流大块石冲击力大大降低,远小于按弹性冲击理论所确定的冲击力,计算结果更符合实际情况。 相似文献
7.
构造简单、成本低廉的简易隔震方法是提高经济欠发达农村地区的低矮房屋抗震性能的有效措施.文中提出一种新的简易隔震方法:橡胶砂芯组合砌块隔震垫层(RSMCBL).其主要原理为:上部结构通过离散的刚性盖板支承在一系列离散的由废旧轮胎颗粒-砂混合物构成的土柱上,橡胶砂柱被刚性砌块所侧向约束,以保证隔震层的强度和稳定性.针对此种... 相似文献
8.
利用小波变换时-频局部化性能,提出了基于小波能量分布向量的结构损伤识别方法。首先建立无损结构响应信号小波能量分布的总体向量;其次,将实测动力响应信号分解为小波包组分,计算其小波能量分布向量(样本向量);通过样本向量和总体向量之间的马氏距离识别损伤。该方法仅利用单测点结构响应数据进行损伤识别,实验方便,计算简单,并通过钢梁试验对损伤识别方法进行了试验验证,识别结果表明小波能量分布向量是一个比较好的结构损伤指标。 相似文献
9.
将结构前两阶振型各自等效为单自由度,采用模态pushover分析确定各等效单自由度的屈服强度系数和延性系数,然后由反应谱计算各阶振型耗散能量需求,利用各振型能量分布曲线,求得各层耗散能量需求,叠加得到各层地震总能量需求,据此确定耗能装置的类型及设计参数.运用该方法对9层钢框架进行了设计,并通过非线性动力分析进行了验证,结果表明该方法精确度符合实际工程需求. 相似文献
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11.
Karel Šilhán Rudolf Brázdil Tomáš Pánek Petr Dobrovolný Lucie Kašičková Radim Tolasz Ondřej Turský Marek Václavek 《地球表面变化过程与地形》2011,36(14):1898-1909
Rockfall is an important process in the final sculpturing of escarpments and scree slopes that originate in bedrock landslides in the Flysch Carpathians. The spatio‐temporal characteristics of rockfall activity were studied at four localities representative of old landslides in the highest part of the Czech Flysch Carpathians (Moravskoslezské Beskydy Mountains). Historical activity, chronology, and spatial context of rockfall activity were reconstructed using dendrogeomorphic techniques and rockfall rate index (RR). A total of 1132 increment cores from 283 trees growing in the rockfall transport and accumulation zones enabled the dating of 989 rockfall events. Reconstruction of a 78‐year‐long RR chronology suggests similar rockfall histories and trends at all study sites, indicating the existence of major common factors driving rockfall dynamics in the region. Temporal analysis and correlation of the RR series obtained with monthly mean temperatures, numbers of days with temperature transitions through 0 °C and monthly precipitation totals show that meteorological characteristics have evident but variable influence on rockfall activity. The most important factor is the effect of freeze–thaw cycles throughout the year, supplemented by low temperatures, especially during autumn. The influence of precipitation totals is of lesser importance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
12.
A series of chlorinated mesoporous activated carbons were derived from waste tires by pyrolysis, activation, and chlorination at different temperatures. The physical and chemical properties of the samples were studied by Brunauer–Emmett–Teller (BET) analysis, Fourier Transform IR Spectroscopy (FT‐IR), point of zero charge measurement, thermogravimetric analysis, and by testing their behavior as adsorbents for toluene removal. Our results showed that the tire‐derived activated carbon samples have highly mesoporous volumes and surface areas, and chlorination treatment has a slight effect on the pore structure. Lewis acidity of the sample increases after chlorination and the chlorine content increases from 0.24 to 2.32% with chlorination temperature increasing from 50 to 400°C. The higher the chlorine content, the more is the toluene adsorption. In comparison with the commercial carbon (F‐400), all the samples have significantly higher adsorption capacity for toluene due to the presence of mesopores, inductive effect of the partial positive chemisorbed chlorine and resonance effects of C? Cl structures. The mesopores probably render easier diffusion of toluene molecule to inner carbon matrix and the strong π–π interaction between toluene and C? Cl resonance structure in the carbon significantly affects the interplay bonding process thus enhances the toluene removal. 相似文献
13.
Broadleaf coppice forests have the capacity to mitigate the threat posed by rockfall in many mountainous regions. Other forest types alike the rockfall protective effect is determined by the mechanical resistance of the coppice tree stems. In addition, the rockfall protective function of coppice forests is enhanced by specific stem aggregations (clumps) that have a rock interception and retention effect difficult to evaluate. The main objectives of this study are to quantify the mechanical resistance of small diameter coppice stems and to gain qualitative insight on breakage behavior. The aim is to supply data for more reliable assessments of the rockfall protective function of coppice forests with rockfall simulation models and to provide a basis for better estimating the rockfall protective effect of coppice clumps. To achieve these objectives we assessed the mechanical resistance of 73 beech (Fagus sylvatica L.) coppice stems using an impact pendulum device. We found an exponential relationship between the stem diameter at breast height (DBH) and mechanical resistance (loss of momentum or kinetic energy of the impactor during impact). Moreover, the results show that the high flexibility of the stems leads to relatively long lasting impacts and only negligible damage at the point of impact on the stem. As a result, the mechanical resistance of the stems is partly determined by impactor velocity and mass. These findings question the practicality of defining mechanical resistance by means of the change of momentum or energy of the impactor. Moreover, the results highlight the limits of upscaling or downscaling the data of this study to conclude for the mechanical resistance of beech trees of other than the tested dimensions. For the target DBH range the obtained dataset is nevertheless more reliable than data of previous studies, because the DBH specific impact process could be considered. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
14.
为了应对中国在新时期提出的“经济,适用,绿色,美观”的建筑政策,装配式结构逐渐成为近年来关注的焦点.对比传统现浇结构,装配式结构更符合节能、节材、环保等要求.因此,进一步研究装配式结构的抗震性能是非常重要的.考虑现有装配式剪力墙结构节点连接部位存在湿作业、施工难度大,常常出现强构件弱节点,抗震性能有待进一步深入研究等情况.为此我们提出一种新的结构形式———预应力约束下装配式剪力墙结构,该结构通过预应力筋连接结构的墙、板,使结构形成一个整体,减少施工现场湿作业,施工质量得以提高.当地震发生时结构通过改变自身的刚度,使其自震周期增大,达到减小地震应力的目的,同时很多提高延性因素的条件也无需考虑,避免钢材的浪费.通过对现浇剪力墙结构模型和预应力约束下装配式剪力墙结构模型进行时程分析,计算结果表明:与现浇剪力墙结构相比,预应力约束下装配式剪力墙结构可减小90%的地震作用,减震效果显著. 相似文献
15.
High-resolution rockfall inventories captured at a regional scale are scarce. This is partly owing to difficulties in measuring the range of possible rockfall volumes with sufficient accuracy and completeness, and at a scale exceeding the influence of localized controls. This paucity of data restricts our ability to abstract patterns of erosion, identify long-term changes in behaviour and assess how rockfalls respond to changes in rock mass structural and environmental conditions. We have addressed this by developing a workflow that is tailored to monitoring rockfalls and the resulting cliff retreat continuously (in space), in three-dimensional (3D) and over large spatial scales (>104 m). We tested our approach by analysing rockfall activity along 20.5 km of coastal cliffs in North Yorkshire (UK), in what we understand to be the first multi-temporal detection of rockfalls at a regional scale. We show that rockfall magnitude–frequency relationships, which often underpin predictive models of erosion, are highly sensitive to the spatial extent of monitoring. Variations in rockfall shape with volume also imply a systemic shift in the underlying mechanisms of detachment with scale, leading us to question the validity of applying a single probabilistic model to the full range of rockfalls observed here. Finally, our data emphasize the importance of cliff retreat as an episodic process. Going forwards, there will a pressing need to understand and model the erosional response of such coastlines to rising global sea levels as well as projected changes to winds, tides, wave climates, precipitation and storm events. The methodologies and data presented here are fundamental to achieving this, marking a step-change in our ability to understand the competing effects of different processes in determining the magnitude and frequency of rockfall activity and ultimately meaning that we are better placed to investigate relationships between process and form/erosion at critical, regional scales. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd 相似文献
16.
This article considers the effectiveness of a seismic isolation system composed of a shallow layer of soil mixed with sand and rubber from shredded tires. A thorough review of past work is first provided, which is then followed by an evaluation of the constitutive properties of sand-rubber soil mixtures when these undergo large states of deformation and slip. Finally, a comprehensive set of simulations that involve a structure underlain by a strongly non-linear, seismic isolating layer when subjected to a variety of actual earthquakes scaled to various peak accelerations, are considered in detail. It is shown that the concept of using soil-rubber mixtures for the purposes of seismic isolation appears promising. A thickness for the rubber–soil mixture of just 2–3 m is likely to be enough to achieve good levels of reductions in the seismic response of the structure. This suggests the desirability of following these analyses with large-scale experimental verifications, not only to fully validate the concept, but also to quantify and assess the numerical predictions with our simple even if non-linear mechanical models, and verify the large-strain constitutive properties of the soil mixtures inferred from laboratory analyses. 相似文献
17.
级配砂石处理核安全级廊道结构的软弱地基有良好的发展前景,发展级配砂石地基条件下的廊道地震响应分析模型是评价其抗震安全性的关键问题。以某核电厂废液输送机排放廊道为研究对象,通过引入等价线性法描述近场级配砂石地基的非线性特征,在分析模型底部施加黏性边界模拟半无限空间,在截断边界的两侧施加黏性边界考虑波动的逸散效果,通过无厚度Goodman单元模拟廊道结构与周围地基的摩擦效应,并利用基于有限元法的自由场响应分析实现地震动输入,从而建立了级配砂石地基条件核安全级廊道结构地震响应分析计算模型。最后,通过开展级配砂石与回填素混凝土两种地基处理条件的廊道地震响应对比分析,该模型表现出良好的规律性及工程应用效果。研究成果可为在建项目、后续核电项目此类问题的地基处理提供借鉴与参考。 相似文献
18.
A.J. Hale E.S. Calder S.C. Loughlin G. Wadge G.A. Ryan 《Journal of Volcanology and Geothermal Research》2009,187(1-2):69-84
During many lava dome-forming eruptions, persistent rockfalls and the concurrent development of a substantial talus apron around the foot of the dome are important aspects of the observed activity. An improved understanding of internal dome structure, including the shape and internal boundaries of the talus apron, is critical for determining when a lava dome is poised for a major collapse and how this collapse might ensue. We consider a period of lava dome growth at the Soufrière Hills Volcano, Montserrat, from August 2005 to May 2006, during which a 100 × 106 m3 lava dome developed that culminated in a major dome-collapse event on 20 May 2006. We use an axi-symmetrical Finite Element Method model to simulate the growth and evolution of the lava dome, including the development of the talus apron. We first test the generic behaviour of this continuum model, which has core lava and carapace/talus components. Our model describes the generation rate of talus, including its spatial and temporal variation, as well as its post-generation deformation, which is important for an improved understanding of the internal configuration and structure of the dome. We then use our model to simulate the 2005 to 2006 Soufrière Hills dome growth using measured dome volumes and extrusion rates to drive the model and generate the evolving configuration of the dome core and carapace/talus domains. The evolution of the model is compared with the observed rockfall seismicity using event counts and seismic energy parameters, which are used here as a measure of rockfall intensity and hence a first-order proxy for volumes. The range of model-derived volume increments of talus aggraded to the talus slope per recorded rockfall event, approximately 3 × 103–13 × 103 m3 per rockfall, is high with respect to estimates based on observed events. From this, it is inferred that some of the volumetric growth of the talus apron (perhaps up to 60–70%) might have occurred in the form of aseismic deformation of the talus, forced by an internal, laterally spreading core. Talus apron growth by this mechanism has not previously been identified, and this suggests that the core, hosting hot gas-rich lava, could have a greater lateral extent than previously considered. 相似文献
19.
Ian Statham 《地球表面变化过程与地形》1976,1(1):43-62
Certain observed characteristics of scree slopes; namely concavity of profile, straight slope angle less than the angle of repose, and good size sorting of particles, are not consistent with an angle of repose model for accumulation. An alternative model is proposed based upon rockfall and surface stone movement and is tested against experimental data of particle movement in the field. It is found that the mechanical model of stone movement generated adequately explains the motion of particles on scree slopes and that it is in keeping with the characteristics of many screes. The static features of some Isle of Skye screes were also measured and the straight-concave slope form with good downslope sorting of material, characteristic of the rockfall process, was found to be present. 相似文献