共查询到19条相似文献，搜索用时 171 毫秒
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地震作用下顺层岩质边坡稳定性的拟静力分析 总被引：2，自引：0，他引：2
通过对顺层岩质边坡的受力分析,应用极限平衡理论和Mohr-Column准则,按照Bishop关于边坡稳定性安全系数的定义,推导出在爆破震动载荷作用下,用于判别顺层岩质边坡稳定性的计算方法。研究结果表明垂直向下、水平指向坡外的爆破荷载以及两者的联合爆破荷载对边坡稳定性影响最大,尤其是后两者;水平指向坡外、垂直向下爆破荷载拟静力系数分别与边坡稳定性安全系数间呈负指数关系和S曲线关系;从动荷载拟静力系数0起,爆破震动水平指向坡外、垂直向下动荷载拟静力系数每增加0.05,有层裂长度的顺层边坡安全系数分别减少7.79%-10.67%、1.28%-1.98%,无层裂的顺层边坡安全系数分别减少7.61%-10.55%、1.47%-2.29%。同时,爆破震动产生的层裂长度、边坡长度以及联合爆破荷载的方向对顺层边坡稳定性也有影响。 相似文献
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城市屋面绿化对城市气候影响预评价 总被引：4，自引：0，他引：4
本文用移植法和数值模拟法分析了屋面绿化气候的影响过程，并用局地系统的热量平衡方程和水分平衡方程对城市屋面绿化后对温度、湿度及风、云、雾、降水等作了预评价。 相似文献
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昆明城市主要街道绿化状况分析 总被引：8，自引：1，他引：8
通过对昆明城市11条主要街道的绿化状况的实际观测和563名城市居民的问卷调查所得资料的分析，发现：在所调查的主要街道中已有72.7%兴建了绿化带，大多是改造后的街道，显示了城市道路加大绿化的理念已在城市道路改造中得到了体现，并且得到了广大市民的认可，但是城市街道绿化仍存在较多问题：绿化程度不尽人意，特别是城市中心的繁华街道绿化程度仍较低，绿化树种单一，缺乏具有特色的本地树种，树龄老化现象也较突出，绿化树木种植缺乏规范性、系统性等等，距市民的期望还有较大差距。在研究分析的基础上对昆明城市街道绿化提出了建议。 相似文献
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通过分析陕县段沿线矿山地质环境及地貌景观边坡修复工程设计实例,提出了在此类工程设计中应注意边坡稳定性、截排水系统合理性、生态绿化适宜性等方面的问题,认为修复工程设计需从长远和综合考虑,这更能体现环境、社会和经济效益。文章选取工程区的2个典型区块--大平地矿渣堆放场和石堆村东山废弃采石场进行分析,认为大平地矿渣堆放场在边坡工程稳定性的治理过程中,由于上部只采用削坡修整,未留置二级卸荷台阶和相应的截排水沟,易造成水土流失和破坏相连部分植被的可能,隐伏着牵引滑坡的可能性。通过采用概率分析法对边坡稳定性进行计算,以及对边坡极端汇水流量的计算,认为边坡应按2级放坡设置防护,对截排水沟应进行因地制宜的优化设计。石堆村东山废弃采石场上部边坡生态工程则缺少对覆土稳固性的考虑,容易造成水土流失,使生态护坡失去有效作用,按该采石场区的地貌条件,宜设置成梯田式绿化或坡面防护绿化。 相似文献
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绿化对冬季山谷城市边界层结构影响的数值模拟研究 总被引：3，自引：1，他引：2
利用RAMS模式模拟了兰州南北两山绿化对冬季兰州城市边界层结构的影响。结果表明:两山绿化改变了近地面的温度场和风场,从日平均温度来看,绿化在兰州冬季表现为明显的增温效应;从风场来看,白天14:00南山的谷风环流增强,北山变化不明显;晚上02:00北山的山风环流明显增强,南山则出现相反的情况;绿化改变了地表能量平衡,绿化后由于地表反照率的减小,使得到达地面净辐射增加,增加的净辐射其中一部分以感热的形式来加热大气;绿化后地气之间的湍流交换增强,增加了大气不稳定度,减弱了白天城市上空的悬浮逆温;本文还讨论了不同绿化布局对白天悬浮逆温的影响。 相似文献
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《山地学报》2015,(6)
关于开挖对阶梯型边坡稳定性及其潜在滑动面位置的影响,目前还缺乏系统研究。以二阶阶梯型均质挖方边坡为研究对象,利用基于有限元应力状态的边坡稳定性分析方法,分别对不考虑开挖效应和考虑开挖效应两种条件下阶梯型边坡的稳定性及其潜在滑动面特征进行了对比,同时对开挖强扰动区的分布特征进行分析。研究结果表明:1.与不考虑开挖效应时计算的边坡安全系数相比,考虑开挖效应后计算得到的边坡安全系数偏小;2.开挖对阶梯型边坡的整体安全系数及其潜在滑动面位置的影响较小;3.在阶梯型均质挖方边坡的设计中,其平台宽度宜大于其上下级坡高平均值的0.5倍,上下级边坡的坡高比宜控制在1~2范围,且下级边坡的坡率小于上级边坡坡率时更有利于边坡的整体稳定。 相似文献
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高地震烈度区堆积体边坡动力响应时程特征分析 总被引：10，自引：0，他引：10
考虑到在地震过程中,工程边坡的动安全系数最小值出现在某一瞬间,而用这个值评价边坡在地震荷载作用下的抗滑稳定性不合适宜。在简单分析地震荷载作用下边坡稳定性评价的主要方法及差异基础上,介绍了地震动力响应时程分析法的基本原理和计算过程,明确指出了边坡动力稳定分析时应注意的边界条件、材料参数等问题,建立了评价动力稳定性的有限元应力法表达式。基于地震动力时程反应,结合金安桥水电站库岸堆积体边坡工程,用动力有限元计算获得了边坡的动力响应在空间的变化规律(包括动应力和加速度等)和整体稳定性,计算成果合理地评价了其稳定性。 相似文献
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巷道或隧道开挖对洞口仰坡稳定性有重要影响,处理不慎极易酿成工程事故。以山东某地下水封洞库施工巷道洞口风化花岗岩仰坡为研究对象,基于离散元模拟和监测数据,选取仰坡最大位移、塑性区体积及稳定系数作为评价指标,研究了巷道开挖进尺、断面尺寸及W值(上覆地层厚度与巷道跨度之比)对仰坡稳定性的影响。结果表明:随着开挖进尺的增加,坡面最大位移增长速率呈匀速—加速—稳定的变化规律,塑性区体积不断增大,且开挖断面越大,位移、塑性区增长速率越大;仰坡稳定系数随进尺的增加先降低后趋于稳定,且断面尺寸越大其降低速率和幅度越大,最终降低幅度为6.9%~27.6%;随着W值增大,仰坡稳定系数先降低后趋于稳定,降低速率随断面尺寸增大而增大,根据特定断面下稳定系数降低速率不同,将关系曲线划分为骤降区、缓降区、陡降区和平稳区。研究结论可为类似工程洞口段划分、施工及稳定性评价提供参考。 相似文献
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Rainfall thresholds for landsliding in the Himalayas of Nepal 总被引：5，自引：0，他引：5
Emmanuel J. Gabet Douglas W. Burbank Jaakko K. Putkonen Beth A. Pratt-Sitaula Tank Ojha 《Geomorphology》2004,63(3-4):131-143
Landsliding of the hillslope regolith is an important source of sediment to the fluvial network in the unglaciated portions of the Himalayas of Nepal. These landslides can produce abrupt increases of up to three orders of magnitude in the fluvial sediment load in less than a day. An analysis of 3 years of daily sediment load and daily rainfall data defines a relationship between monsoonal rainfall and the triggering of landslides in the Annapurna region of Nepal. Two distinct rainfall thresholds, a seasonal accumulation and a daily total, must be overcome before landslides are initiated. To explore the geomorphological controls on these thresholds, we develop a slope stability model, driven by daily rainfall data, which accounts for changes in regolith moisture. The pattern of rainfall thresholds predicted by the model is similar to the field data, including the decrease in the daily rainfall threshold as the seasonal rainfall accumulation increases. Results from the model suggest that, for a given hillslope, regolith thickness determines the seasonal rainfall necessary for failure, whereas slope angle controls the daily rainfall required for failure. 相似文献
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Recent morphological evolution of the Lower Mississippi River 总被引：1，自引：0，他引：1
This study documents slope and stream power changes in the Lower Mississippi River during the pre-cutoff (1880s–1930s), and post-cutoff (1943–1992) periods. The study reach extends from New Madrid, MO, to Natchez, MS, a distance of about 900 km. Analyses for six major reaches and 13 sub-reaches for the pre- and post-cutoff periods indicate that the river presently has a much larger slope and stream power than prior to the cutoffs. The largest increases have occurred between Fulton, TN, and Lake Providence, LA, where slope and stream power increases range from about 27% to 36% and 20% to 38%, respectively. Increases in slope and stream power in reaches upstream and downstream have also occurred, but to a lesser degree. Previous investigations have shown that no coarsening of the bed material has occurred since 1932, and that the bed material may actually be somewhat finer overall. As the Lower Mississippi River is not a sediment-starved system, an increase in stream power with no change in D50 would be expected to be offset by an increase in the bed material load as the river adjusts towards equilibrium. Previous investigators have inferred a reduction in the sediment loads on the Mississippi River this century based on analyses of total measured suspended loads. However, these results should be viewed as primarily representing the changes in wash load and should not be taken to imply that bed material loads have also decreased. Therefore, the bed material loads in the study reach should be greater than in the pre-cutoff period. Excess stream power in the sub-reaches directly affected by cutoffs resulted in scour that increased downstream bed material load. These elevated sediment loads play a key role in driving morphological adjustments towards equilibrium in the post-cutoff channel. The stability status of the channel in the study reach currently ranges from dynamic equilibrium in the farthest upstream reaches through severe degradation to dynamic equilibrium in the middle reaches, and aggradation in the lowest reaches. These evolutionary trends cannot be explained by consideration of changes in slope and stream power alone. Changes in the incoming bed material load to each reach generated by upstream channel evolution must also be considered. 相似文献
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高切坡超前支护桩与坡体共同作用分析 总被引：5，自引：0，他引：5
针对高切坡施工常常导致边坡失稳破坏,诱发滑坡发生的现象,提出采用超前支护桩整治不稳定高切坡的设计理论。采用解藕方法研究了超前支护桩与开挖坡体之间的相互作用机制,其中高切坡开挖面采用弹性理论分析；超前支护桩采用可以考虑桩侧向土体屈服的弹塑性理论进行桩的内力理论解,根据两者之间荷载变形关系建立联系求解,为高切坡超前支护桩的设计提供依据。结果表明：桩土相互作用力大于常规主动土压力,与边坡开挖量、开挖高度、支护桩的刚度以及土体性质等因素密切相关。 相似文献
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岩质边坡防护的最有效措施就是锚固工程。然而锚固参数(包括锚杆或锚索长度、锚固间距、预应力大小等)的选取至今在理论上未能很好解决,在实际工程中也未体现出合理的优化设计。以云沱段狮子包边坡2-2′剖面(K0 85.7 m)为例,运用正交试验设计法分析锚固参数的组合方案,以边坡稳定性系数作为评价指标,分别改变锚固参数,以此分析对边坡稳定性的影响。研究结果表明,对边坡稳定性影响显著的因素由大至小的顺序是:预应力大小、锚固间距、锚杆长度。以此研究结果为该实例的锚固支护参数选取确定了设计方案,最后采用有限差分程序FLAC3D进行了锚固效果数值分析验证。 相似文献
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Florence Dapples André F. Lotter Jacqueline F.N. van Leeuwen Willem O. van der Knaap Sophia Dimitriadis Daniel Oswald 《Journal of Paleolimnology》2002,27(2):239-248
Schwarzsee is located in the western Swiss Alps, in a region that has been affected by numerous landslides during the Holocene, as evidenced by geological surveys. Lacustrine sediments were cored to a depth of 13 m. The vegetation history of the lake's catchment was reconstructed and investigated to identify possible impacts on slope stability. The pollen analyses record development of forest cover during the middle and late Holocene, and provide strong evidence for regional anthropogenic influence such as forest clearing and agricultural activity. Vegetation change is characterized by continuous landscape denudation that begins at ca. 4300 cal. yrs BP, with five distinct pulses of increased deforestation, at 3650, 2700, 1500, 900, and 450 cal. yrs BP. Each pulse can be attributed to increased human impact, recorded by the appearance or increase of specific anthropogenic indicator plant taxa. These periods of intensified deforestation also appear to be correlated with increased landslide activity in the lake's catchment and increased turbidite frequency in the sediment record. Therefore, this study gives new evidence for a strong influence of vegetation changes on slope stability during the middle and late Holocene in the western Swiss Alps, and may be used as a case study for anthropogenically induced landslide activity. 相似文献
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Alexander Isakov 《寒旱区科学》2013,5(4):0353-0362
The main reasons for a breach of trouble-free operation of the subgrade are the different kinds of deformation, such as train load impact on
subgrade surface, loss of stability to subgrade slope, weight of embankment on the base, and partial or complete failure of the railway track
due to frost heaving. This paper gives a summary of deformation analysis methods being developed in Russia to estimate the operating conditions
of the railway subgrade. 相似文献
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岩体结构面是影响岩质边坡位移及其稳定性的重要因素之一,但是由于数学和力学上的困难,岩体结构面对岩质边坡变形的影响通常难以用理论公式计算得出,目前只能采用数值分析手段。分别针对坚硬岩边坡和软岩边坡中存在软弱结构面的情况,用有限元差分程序FLAC和边坡稳定性系数公式,定量和定性地讨论了岩体结构面倾角对岩质边坡位移的影响。通过计算分析发现,(1)岩体中结构面的存在是影响岩石边坡位移及其稳定性的重要因素之一;(2)随着结构面倾角的增加,边坡的稳定性和边坡的位移可能增加,也可能减小,并不象我们想象的那样随着结构面倾角的增加而增加,必须用定性和定量方法针对具体问题进行具体分析。 相似文献