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1.
SV波入射下河谷地形地震动分布特征分析 总被引：1，自引：1，他引：0
基于显式有限元方法和人工透射边界,对二维河谷地形在3条地震动波以SV波形式垂直入射和30°斜入射下进行了地震反应分析,比较了河谷地表各观测点地震动的差别,探讨了河谷地形地震动空间分布特征。结果表明,河谷地形对地震动分布具有重要影响,沿河谷斜坡顶到谷底的各观测点地震动峰值加速度（PGA）存在显著差异,地震动位移存在差动现象,地震动加速度反应谱在大于1 Hz的高频段差别明显。入射角度是影响场地地震反应的重要因素,斜入射时各观测点PGA和相对位移的离散程度明显大于垂直入射情形。 相似文献
2.
岩性及岩体结构对斜坡地震加速度响应的影响 总被引：1，自引：0，他引：1
斜坡岩体的岩性及岩体结构是斜坡在地震作用下产生变形破坏的主要控制因素。基于振动台模型试验,对4个斜坡模型探讨了这2个因素对斜坡地震动力响应的影响。岩性包括强度相对较高的硬岩和强度相对较低的软岩,对这两种岩性的斜坡又分别考虑了不含结构面的均质斜坡和含水平层状结构面的斜坡。基于传感器采集到的大量数据,以主频相近的天然地震波和10 Hz正弦波加载为分析工况,获得了以下几点认识：（1）4个模型斜坡坡面和坡内的水平向加速度均具有高程放大效应,尤其是软岩斜坡坡顶放大效应最显著;（2）软岩斜坡对水平向加速度的高程放大效应强于硬岩斜坡,尤其是在均质斜坡中表现最显著,均质软岩斜坡的高程放大效应呈现出明显的非线性特征;（3）当加载方向与水平层面平行时,含水平层状结构面的斜坡比均质斜坡产生了更强的高程放大效应,且在软岩斜坡中体现最显著;（4）岩性差异对斜坡水平向加速度高程效应的影响比结构差异的影响更为显著。研究结果为岩质斜坡的抗震设计提供了一定参考。 相似文献
3.
5.12汶川8级大地震沿龙门山断裂带形成长350多km,宽约50 km的地表破裂带,触发了1万多处崩塌、滑坡、泥石流(碎屑流)地质灾害,其中巨型灾害体87处、大型灾害体606处,形成了136个较大规模的堰塞湖。地震地质灾害的链生特征显著,形成地震-崩塌、地震-滑坡-碎屑流-堰塞湖-堰塞坝溃决-泥石流等典型地质灾害链。地震次生地质灾害具有分布范围广、数量多、种类全、密度大、强度高、致灾重的特点。在部分地区,崩塌、滑坡和碎屑流的分布面积占地震极重灾区面积的30%~58％,甚至高达80％。据初步统计,崩塌、滑坡和碎屑流共导致大约2万人死亡,其中北川县老县城滑坡导致1 600多人死亡。地震次生地质灾害主要沿断裂带、河谷和交通线分布。崩塌、滑坡的破裂源主要位于河流拐弯处靠近侵蚀岸一侧、山脊两侧及坡肩部位,这与上述部位对地震动峰值加速度的放大作用直接相关。地震次生地质灾害主要受地震动峰值加速度和地形控制,其次为岩性、斜坡结构、活动断裂、人类工程活动。许多大型崩塌、滑坡还具有高速远程的特征,部分崩塌、滑坡 碎屑流位移达数km,速度高达100~300 m/s,其运动轨迹复杂多变,常常导致多处人员伤亡,是高山峡谷地区地质灾害风险评估和减灾防灾必须面临的新课题。根据上述情况,文中对汶川地震次生地质灾害的基本特征、分布规律和主要影响因素进行了初步总结,并对地震滑坡的形成机制和运动模式进行了初步探讨。首次提出高山峡谷地区单一斜坡上呈阶梯状多级滑动的群发性地震滑坡的形成模式:强烈地震往往引起剧烈的地面震动,而高陡的山脊及其坡肩部位对地震波具有明显的放大作用,因此,上述部位往往是地震滑坡的高易发地段,当地震动峰值加速度超过不稳定性斜坡的临界峰值加速度时,斜坡失稳破坏形成一系列的群发性滑坡,从上到下往往形成阶梯状多级滑动的滑坡群,此种模式适用于残坡积层、风化层地震滑坡和主滑面较缓的地震基岩滑坡。最后,指出了今后应重点研究的科学问题,并对防灾减灾措施提出了一些建议。 相似文献
4.
Analysis on mechanism of landslides under ground shaking: a typical landslide in the Wenchuan earthquake 总被引：1，自引：1，他引：0
Yang Changwei Liu Xinmin Zhang Jianjing Chen Zhiwei Shi Cong Gao Hongbo 《Environmental Earth Sciences》2014,72(9):3457-3466
A high steep rock hill with two-side slopes near National Road 213 is used as a prototype in this paper. The full process from initial deformation to sliding of the slope during ground shaking is simulated by a new discrete element method—continuum-based discrete element method. Then, the seismic responses of a high steep rock hill with two-side slopes are researched from the base of time, frequency and joint time–frequency domain using Hilbert–Huang transform and Fourier Transform. The findings are: first, the stress concentration phenomenon occurs at the top of the sliding mass, and then some tension and shear failure points appear, which expand from the top toward the toe of the sliding mass along the structural plane. At the same time, the number of tension failure points gradually increases. Then the toe of the sliding mass fails, and shears out from its toe which results in the landslide. If the material parameters are under the same conditions, the landslide in the middle of the slope occurs before that at the foot of slope, and the starting time of landslide and the arrival time of the peak ground acceleration are synchronous or the former slightly lags behind the latter. The difference of distribution and dissipation of earthquake energy in the sliding body and sliding bed is the major influence factor to induce the landslide. When the accelerations are small, the instantaneous frequency of accelerations between sliding bed and sliding body is generally consistent, the energy transmittance coefficients of the sliding structural plane and the controlled frequency band of the energy all range in a limitation; with the increase of the seismic intensity, the instantaneous frequency and the energy transmittance coefficients gradually decrease, and then they are steady within the lower limitation. At the same time, the controlled frequency band also shifts gradually from high frequency band to the lower one. Based on the input seismic wave, the peak acceleration amplifies as the increase of elevation, regardless of the monitoring points on the steep slope, gentle slope side or inside of the slope. Generally speaking, amplification of the vertical peak acceleration is stronger than that of the horizontal peak acceleration, and amplification of the peak acceleration on a steep slope is stronger than that on a gentle slope, and that of inside of the slope is the weakest amplification. 相似文献
5.
Fatih Mosque and its Kulliye (complex) are one of the most important historical monuments in Istanbul. Since it has been built between 1463 and 1470, Fatih Mosque had been subjected to nine strong earthquakes and suffered various degrees of structural damage at every case, including the latest August 17, 1999 Kocaeli Earthquake (Mw = 7.4, epicentral distance approximately 100 km). Recently, a project has been initiated first to study the possible causes of earthquake damage and then develop retrofitting and strengthening techniques to protect this invaluable monument from further damages in the future earthquakes. As part of this investigation, local site soil conditions had been determined and site behavior during earthquakes had been studied in detail. In this paper, the results of 1-D site response analysis, which included convolution and deconvolution analyses utilizing the strong ground motions recorded during the August 17, 1999 Kocaeli Earthquake are presented. The results of the analyses had demonstrated the considerable degree of site amplification, compatible with the recorded motions and the damage suffered. The expected site behavior during a probable future earthquake is also studied using a site specific simulated bedrock motion, and earthquake parameters to be used in dynamic structural analysis are estimated. 相似文献
6.
重庆小南海滑坡形成机制离散元模拟分析 总被引：1，自引：0，他引：1
重庆小南海滑坡是烈度相对较低地区发生的地震高位滑坡,其成因一直令人费解。基于重庆黔江小南海相关研究资料,通过对复原的小南海坡体进行失稳分析,计算得出使岩体产生崩滑破坏的地震力临界条件,即只有当地震波地形放大后滑坡才能启动。为了进一步验证计算所得的结论,运用UDEC软件建立小南海典型二维场地模型,施加相应的地震力对坡体失稳崩滑的全过程进行模拟,以研究地震作用下地形放大效应触发具平行坡面陡倾控制性结构面的高位岩质斜坡地震机理。研究结果表明,在地震波传播过程中,具平行坡面陡倾控制性结构面的高陡突出地形对地震波有明显的放大作用。该坡体运动模式为：峰值加速度放大-增加的振幅迫使岩体顺平行坡面陡倾控制性结构面迅速拉裂-沿缓倾层面滑移-高速脱离滑源区-巨大的势能和动能驱动坡体做长距离运动,其间伴随解体、颗粒间相互碰撞、铲刮作用,具有二相甚至三相流体性质。分析揭示地震力作用下斜坡体中质点加速度具有地形放大效应。对比结构面监测点和基岩监测点加速度放大系数,表明,滑坡启动时具有较大的加速度,当遇到平行坡面的不连续结构面时,斜坡动力响应强烈,最终导致坡体失稳。 相似文献
7.
On May 21, 2021, at 21:48, the Ms6.4 Yangbi earthquake struck Dali prefecture, Yunnan province, China; the maximum PGA reached 714.78 gal, causing 37 casualties and infrastructures damage. A field investigation demonstrated that seismic landslides were concentrated along the G56 Hangrui and Dayangyun highways, classified as local rock falls and shear slides. The shear slides were more severe than the local rock falls and were located along the Dayangyun highway, which was still under construction when the earthquake occurred, severely impacting following engineering activities. Typical shear slides caused by the earthquake were selected for detailed investigations; electrical resistivity topography (ERT) was conducted to study the failure mechanism. The ERT results indicated that the sliding surface was located at the interface between the overburden layer and the underlying rock stratum. The slope failures along the Dayangyun highway were characterized by several tensile cracks on the rear edge, a relatively short displacement, and an accumulation at the toe of the excavated slope where reinforcement measures had not yet been completed. The combined effect of engineering activities and a geological structure provided favorable conditions for slope failure. In addition, seismic motion triggered the landslides; however, engineering activity was a specific and significant factor contributing to the shear slides during the Yangbi earthquake. Excavation and incomplete construction reduced the stability of the overburden soil layer. Although the scale of the seismic landslides in the Yangbi earthquake was generally small, the coming rainy season after the earthquake may contribute for sliding again.
相似文献8.
Sergio A. Sepúlveda Alejandra Serey Marisol Lara Andrés Pavez Sofía Rebolledo 《Landslides》2010,7(4):483-492
On the 21st of April 2007, the Aysén Fjord earthquake (Mw 6.2) in southern Chile (45.3° S, 73.0° W) triggered hundreds of landslides in the epicentral area along the fjord coast and surroundings. Some of these landslides induced large tsunami waves within the fjord causing fatalities and damaging several salmon farms, the most important economic activity of the area. The landslides included rock slides and avalanches, rock falls, shallow soil and soil–rock slides, and debris flows. The earthquake was the climax of a seismic swarm that began 3 months earlier. The seismicity is associated with tectonic activity along the Liquiñe–Ofqui fault zone (LOFZ), a major structural feature of the region. The earthquake-induced landslides were mapped and classified from field observations and remote sensing analysis. The landslide areas and epicentral distances are within the expected range for the earthquake magnitude according to worldwide data, while the position of landslides on the slopes strongly suggests topographic amplification effects in triggering the failures. The location of the landslides is also clearly related to some of the main fault branches of the LOFZ. The seismic event has configured a new situation of seismic and landslide hazard in the Aysén region and along the LOFZ, where the presence of towns and economic infrastructure along the coasts of several fjords constitutes a potential risk that was not considered before this seismic event. 相似文献
9.
10.
Eliana Esposito Sabina Porfido Armando L. Simonelli Giuseppe Mastrolorenzo Gianmaria Iaccarino 《Engineering Geology》2000,58(3-4):353-376
This paper both describes and discusses landslides and other ground effects induced by the September–October 1997 seismic sequence, which struck the Umbria and Marche regions (Central Italy). Three main events occurred on 26 September at 00:33 and 09:40 GMT, and 14 October with magnitude Mw equal to 5.8, 6.0 and 5.4, respectively; furthermore hundreds of minor but significant events were also recorded. The authors examined an area of some 700 km2 around the epicentre (Colfiorito). Primary and secondary effects were observed, including surface faulting phenomena, landslides, ground fractures, compaction and various hydrological phenomena. Surface evidence of faulting reactivation was found along the well-known capable faults, to a total length of ca. 30 km. Landslides, which were the most recurrent among the phenomena induced, consisted mainly of rock falls and subordinately of rotational and translational slides, which were generally mobilised by the inertia forces during the seismic motion. The percentage of reactivated old landslides decreased as the distance from the epicentral zone increased; a similar decrease had been observed for the 1980 Irpinia earthquake (Southern Italy). The ground fracture distribution was consistent with the regional structural setting and the general pattern of macroseismic field. Numerous episodes of hydrological changes were observed within the most severely damaged area. All this evidence confirms the relevance of the study of ground surface effects for achieving a more complete evaluation of seismic hazard. 相似文献
11.
在山区,地震诱发滑坡造成的人员伤亡往往占到地震总伤亡人数的一半以上,尤其是在黄土地区,由于地震造成的黄土滑坡具有运动距离远等特征,其灾难性更严重。针对地震诱发黄土斜坡的失稳峰值加速度、临界位移和运动距离等问题,本文利用离散元（PFC）方法,通过对室内三轴实验的应力-应变曲线进行标定和高精度航拍三维地形数据进行转化,以宁夏海口村黄土斜坡为研究对象,开展三维地震作用下斜坡失稳破坏和运动过程的数值模拟研究。通过监测不同位置在地震作用下的应力分量,计算监测点的p、q值并与室内三轴实验所得到p-q破坏线进行比较,获得斜坡破坏过程中的应力路径。结合颗粒的监测位移,获得斜坡失稳破坏的临界位移,得出该黄土斜坡失稳峰值加速度为0.135 g,临界位移为50 cm。同时根据不同地面环境条件,预测了在不同摩擦系数下斜坡失稳后的危害范围,为黄土地区边坡工程的抗震设计及防震减灾工作提供一种新的可视化方法。 相似文献
12.
以玉树7.1级地震诱发的玉树机场路堆积层滑坡为对象,该滑坡坡度约为10o,长×宽×厚为317 m×482 m×19.8 m,由以碎石土为主的上覆层、卵石土为主的滑动带及基岩3层组成,开展大型振动台模型试验,探究震后边坡再次承受振动荷载的能力以及地震垂直分量对坡体稳定性的贡献,分析其动力响应特征和失稳破坏机制。结果表明,强震作用下堆积层滑坡的永久变形是造成地震地质灾害的重要因素;随着输入地震荷载增大,坡脚率先破碎沉降,坡体中部产生弧形裂隙并产生沉降,坡顶出现贯穿张裂隙和剪切裂隙并向坡腰推进,表现出典型的牵引性滑坡特征;峰值加速度(PGA)、动土压力以及加速度频谱与输入地震波的强度、滑坡高程呈正相关;PGA放大系数呈现出明显的非线性特征,其变化趋势随地震荷载强度增大而减小,地震波垂直分量对滑坡PGA放大系数影响略大于水平分量。 相似文献
13.
顺层岩质边坡地震动力响应研究 总被引：1，自引：0，他引：1
地震作用下边坡的动力响应研究是边坡动力稳定分析的基础,利用FLAC3D有限差分软件建立一个顺层岩质边坡动力数值模拟模型,对其在竖向和水平向地震耦合作用下的动力响应全过程进行研究。研究表明,地震竖向和水平向耦合作用模拟比简单的模拟水平向振动更加接近实际情况,对岩土体的破坏更大;顺层岩质边坡在耦合地震作用下存在垂直放大和临空面放大作用;坡面水平向和竖向加速度均随高程增加呈增大趋势,在结构面处增大特别明显;竖向地震波产生的水平与竖向拉裂是触发斜坡体产生初期崩滑破坏的主控因素;边坡动力响应特征值的放大效应表明,其放大系数值从大到小依次是：竖向加速度＞水平加速度＞竖向速度＞水平速度;耦合地震波作用下,随着av /aH的增大,坡面监测各点横向位移基本呈增大趋势,说明竖向地震作用起了重要的破坏作用。 相似文献
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The characteristics and failure mechanism of the largest landslide triggered by the Wenchuan earthquake, May 12, 2008, China 总被引：9，自引：7，他引：2
Runqiu Huang Xiangjun Pei Xuanmei Fan Weifeng Zhang Shigui Li Biliang Li 《Landslides》2012,9(1):131-142
Strong earthquakes are among the prime triggering factors of landslides. The 2008 Wenchuan earthquake (M
w = 7.9) triggered tens of thousands of landslides. Among them, the Daguangbao landslide is the largest one, which covered
an area of 7.8 km2 with a maximum width of 2.2 km and an estimated volume of 7.5 × 108 m3. The landslide is located on the hanging wall of the seismogenic fault, the Yingxiu–Beichuan fault in Anxian town, Sichuan
Province. The sliding mass travelled about 4.5 km and blocked the Huangdongzi valley, forming a landslide dam nearly 600 m
high. Compared to other coseismic landslides in the study area, the Daguangbao landslide attained phenomenal kinetic energy,
intense cracking, and deformation, exposing a 1-km long head scarp in the rear of the landslide. Based on the field investigation,
we conclude that the occurrence of the landslide is controlled mainly by the seismic, terrain, and geological factors. The
special location of the landslide and the possible topographic amplification of ground motions due to the terrain features
governed the landslide failure. The effects of earthquakes on the stability of slopes were considered in two aspects: First,
the ground shaking may reduce the frictional strength of the substrate by shattering of rock mass. Second, the seismic acceleration
may result in short-lived and episodic changes of the normal (tensile) and shear stresses in the hillshopes during earthquakes.
According to the failure mechanism, the dynamic process of the landslide might contain four stages: (a) the cracking of rock
mass in the rear of the slope mainly due to the tensile stress generated by the ground shaking; (b) the shattering of the
substrate due to the ground shaking, which reduced the frictional strength of the substrate; (c) the shearing failure of the
toe of the landslide due to the large shear stress caused by the landslide gravity; and (d) the deposition stage. 相似文献
16.
基于国内外研究现状和岩质滑坡案例,总结出岩质滑坡的水力致灾机制,归纳考虑水力作用下的岩质斜坡主要失稳破坏模式,评述了岩质斜坡稳定性分析方法。岩质滑坡的水力致灾机制主要由于水对滑体产生的静水压力（岩体侧面的推力、滑面的扬压力和岩体的浮力）和动水压力（向坡外的渗透力）作用。从渗流—应力耦合的角度可较全面评价水渗流对坡体稳定性的影响。斜坡的岩体结构决定了水力作用方式和坡体的失稳破坏形式,考虑水力作用下的岩质斜坡失稳破坏形式主要有:顺层滑动、平推式滑动、楔形体滑移和危岩的崩塌。对于水力作用下岩质斜坡的稳定性分析方法主要有极限平衡法、有限元强度折减法、基于断裂力学的危岩稳定性分析法和渗流—应力耦合模型分析法,其中前两种方法应用较为广泛。 相似文献
17.
It has been known that ground motion amplitude will be amplified at mountaintops; however, such topographic effects are not
included in conventional landslide hazard models. In this study, a modified procedure that considers the topographic effects
is proposed to analyze the seismic landslide hazard. The topographic effect is estimated by back analysis. First, a 3D dynamic
numerical model with irregular topography is constructed. The theoretical topographic amplification factors are derived from
the dynamic numerical model. The ground motion record is regarded as the reference motion in the plane area. By combining
the topographic amplification factors with the reference motions, the amplified acceleration time history and amplified seismic
intensity parameters are obtained. Newmark’s displacement model is chosen to perform the seismic landslide hazard analysis.
By combining the regression equation and the seismic parameter of peak ground acceleration and Arias intensity, the Newmark’s
displacement distribution is generated. Subsequently, the calculated Newmark’s displacement maps are transformed to the hazard
maps. The landslide hazard maps of the 99 Peaks region, Central Taiwan are evaluated. The actual landslide inventory maps
triggered by the 21 September 1999, Chi-Chi earthquake are compared with the calculated hazard maps. Relative to the conventional
procedure, the results show that the proposed procedures, which include the topographic effect can obtain a better result
for seismic landslide hazard analysis.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
应用概率地震危险性评价模型进行地震滑坡危险性区划,是解决潜在地震诱发滑坡危险性评价中震源不确定性与诱发滑坡时空不确定性的有效方法.通过理论分析,结合鲁甸地震区的实际情况,对基于力学原理的Newmark滑块位移模型与概率地震滑坡危险性分析方法中的参数的不确定性问题进行了分析,将斜坡岩土体地震作用下的强度衰减效应、地震加速度地形放大效应、断层破碎带效应融合到了斜坡累积位移计算模型中,进行了模型计算参数的优化.改进后的分析模型,更好地反映了高陡斜坡地形与断层破碎带对地震滑坡灾害发育的控制作用,在鲁甸地震区域滑坡应用中,优化模型中的滑坡失稳极高风险区与实际地震滑坡分布表现出了较好的一致性,在超越概率2%的滑坡失稳概率分布中,鲁甸地区包谷垴—小河断裂、鲁甸—昭通断裂带及牛栏江河谷地带地震滑坡高—极高风险区分布面积增幅十分显著.因此,在Newmark滑块位移模型中考虑地震动参数与岩土参数动态响应规律与变量间的定量关系,对于提高区域斜坡稳定性分析的可靠性具有重要意义. 相似文献
19.
地震易发地区的锚固岩石边坡,需要研究其地震稳定性。对于锚固典型岩石边坡,在考虑水平与竖向地震力、张裂缝积水深度、坡顶超载、锚索倾角、锚索位置、锚索拉力及静水与动水压力等的条件下,运用拟静力和拟动力方法分别推导了不同工况条件下其抗滑和抗倾覆地震安全系数。分析表明,竖向向上地震力有利于锚固岩石边坡的抗滑稳定,而竖向下的地震力有利于锚固岩石边坡的抗倾覆稳定;在相同工况条件下,当岩体放大系数等于1.0时,拟动力与拟静力方法所得锚固岩石边坡地震安全系数相差无几,但是,当岩体放大系数逐渐增大时,拟动力方法所得地震安全系数越来越明显地小于拟静力方法所得地震安全系数。因此,在抗震设计当中适当的考虑岩体放大系数,将会有利于锚固岩石边坡的安全设计。 相似文献
20.
多点、多向地震作用下非圆弧滑面边坡稳定分析通用条分法 总被引：2，自引：1，他引：1
在地震边坡稳定性分析当中,往往采用单点地震动输入,但实际地震动是随着时间和空间变化的。为了研究边坡在多点、多向地震作用下的稳定性,地震动输入采用考虑地震动的空间时间变化特性的人工合成多点、多向地震动,并将之转化为作用于边坡上的多点、多向地震荷载,在陈祖煜院士所提出的通用条分法的基础之上,推导了适用于任意形状滑面、即满足力的平衡又满足力矩平衡的多点、多向地震作用下边坡稳定通用条分法的极限平衡微分方程,并给出了求解动力安全系数的方法,通过两个算例验证了方法的可行性。 相似文献