Analytical formulas for the geometric and inertia quantities of the largest removable blocks around tunnels     

Fulvio Tonon 《国际地质力学数值与分析法杂志》2007,31(11):1301-1327

This paper presents algorithms for determining the vertices of the maximum removable block (MB) created by a joint pyramid (JP) around a tunnel when discontinuities are fully persistent. It is shown that an MB cannot be formed by more than 4 discontinuities and this drastically limits the proliferation of rock blocks that need to be analysed. The non‐convex block obtained after the MB is tunnelled through (real maximum block, RMB) is partitioned into a set of tetrahedra, and procedures are given for determining the vertices of these tetrahedra. Geometric and inertia quantities needed for stability analysis and support/reinforcement design are determined as functions of the calculated vertices' co‐ordinates. These quantities are: RMB's volume, face areas, perimeter of the excavated surface, centroid and inertia tensor. The algorithms for their calculation are at least two times faster than other algorithms previously proposed in other applications. It is shown that the formulations presented by Goodman and Shi for translational analysis and by Tonon for rotatability analysis can be used to analyse the RMBs using the geometric quantities presented. A numerical example is presented among those used to verify these analytical procedures and their implementation. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Outburst risk of barrier lakes in Sichuan,China   总被引：2，自引：1，他引：1  

Genwei Cheng  Xiaodan Wang  Xiubin He  Jihui Fan  Jianrong Fan 《山地科学学报》2008,5(3):189-193

34 barrier lakes induced by earthquake have been formed by wedged debris on the river channels after a massive earthquake happening on May 12 in Sichuan, China. Among them, the Tangjiashan Barrier Lake is the largest one. It faces very urgent risk of dam breaking when water level reaches the top and begins overflow in case of storm rainfalls and continually aftershocks, threatening already devastated cities and villages with about 1.5 million people downstream. The outburst of a similar barrier lake occurred in the Minjiang River in 1933, causing a catastrophic flood. Risk analysis indicates that not all barrier lakes are highly dangerous. Only those lakes with very high dams and water to be filled up in short period need to be dealt with immediately.  相似文献   

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郑水明  王岚  黄江  王平 《大地测量与地球动力学》2008,28(6):73-76

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尼泊尔Ms8.1地震构造背景及对周边地区地震活动趋势的影响     

雷东宁  蔡永建  李恒  吴建超  乔岳强  余松  廉超 《大地测量与地球动力学》2015,35(5):738-741

分析印度板块与欧亚板块俯冲带、尼泊尔Ms8.1地震震中区地震构造及地震发震构造,讨论主震对余震触发及余震的时空强特征和地震对周边地区地震活动趋势的影响。初步分析认为,主边界断裂为本次地震的发震构造,属于低角度逆冲断层地震;余震分布范围与震源破裂面积和方式基本一致,具有向东迁移的时空特征;西藏定日Ms5.9、聂拉木Ms5.3地震不属于尼泊尔地震余震,是应力扰动的结果;沿俯冲带向东至喜马拉雅东构造结是大震发生的危险地段。  相似文献   

High-precision relocation of the aftershock sequence of the January 8, 2022, MS6.9 Menyuan earthquake          下载免费PDF全文

Liping Fan  Boren Li  Shirong Liao  Ce Jiang  Lihua Fang 《地震科学（英文版）》2022,35(2):138-145

The 2022 Menyuan M_S6.9 earthquake, which occurred on January 8, is the most destructive earthquake to occur near the Lenglongling (LLL) fault since the 2016 Menyuan M_S6.4 earthquake. We relocated the mainshock and aftershocks with phase arrival time observations for three days after the mainshock from the Qinghai Seismic Network using the double-difference method. The total length and width of the aftershock sequence are approximately 32 km and 5 km, respectively, and the aftershocks are mainly concentrated at a depth of 7–12 km. The relocated sequence can be divided into 18 km west and 13 km east segments with a boundary approximately 5 km east of the mainshock, where aftershocks are sparse. The east and west fault structures revealed by aftershock locations differ significantly. The west fault strikes EW and inclines to the south at a 71º–90º angle, whereas the east fault strikes 133º and has a smaller dip angle. Elastic strain accumulates at conjunctions of faults with different slip rates where it is prone to large earthquakes. Based on surface traces of faults, the distribution of relocated earthquake sequence and surface ruptures, the mainshock was determined to have occurred at the conjunction of the Tuolaishan (TLS) fault and LLL fault, and the west and east segments of the aftershock sequence were on the TLS fault and LLL fault, respectively. Aftershocks migrate in the early and late stages of the earthquake sequence. In the first 1.5 h after the mainshock, aftershocks expand westward from the mainshock. In the late stage, seismicity on the northeast side of the east fault is higher than that in other regions. The migration rate of the west segment of the aftershock sequence is approximately 4.5 km/decade and the afterslip may exist in the source region.  相似文献   

针对应急救援的强余震特征统计          下载免费PDF全文

管丽倩    戴君武    杨永强    许德峰   《世界地震工程》2022,38(3):212-220

大地震后强余震活跃,震后快速判断最大余震震级和强余震发生可能性对提高应急救援效率有重大意义。针对震后应急救援,本文根据救援存活率将震后救援期分为8个时段:震后12 h、震后24 h、震后48 h、震后72 h、震后96 h、震后120 h、震后144 h和震后168 h。对我国大陆地区1966年以来6级及以上地震强余震资料进行分时段统计,分别拟合出8个时段的最大余震震级和主震震级的经验公式;并提出震后强余震发生可能性的经验判断方法,通过本文提出的可能性指数a,依据主震震级,震后可以快速判定强余震发生的可能性。  相似文献   

2011日本东北大地震前震余震重力效应分析     

龚正  许才军 《测绘科学》2015,(12):59-62

针对2011年日本东北大地震(Tohoku-Oki地震)发生前后较短时间内的多次较大前震和余震和主震混在一起,不利于提取出主震同震信号的问题,该文利用弹性位错理论模拟计算了Tohoku-Oki地震一次较大前震和两次较大余震的同震重力变化,讨论了这3次地震单独和综合的重力效应,并与主震重力变化对比分析,认为这3次前震和余震引起的重力变化数值较大,影响范围广,会直接影响到Tohoku-Oki地震主震的同震重力信号提取,所以需要作为重要误差考虑。  相似文献   

Aftershock seismic assessment taking into account postmainshock residual drifts          下载免费PDF全文

Jorge Ruiz‐García  Julio D. Aguilar 《地震工程与结构动力学》2015,44(9):1391-1407

This paper introduces and evaluates a methodology for the aftershock seismic assessment of buildings taking explicitly into account residual drift demands after the mainshock (i.e., postmainshock residual interstory drifts, RIDR_o). The methodology is applied to a testbed four‐story steel moment‐resisting building designed with modern seismic design provisions when subjected to a set of near‐fault mainshock–aftershock seismic sequences that induce five levels of RIDR_o. Once the postmainshock residual drift is induced to the building model, a postmainshock incremental dynamic analysis is performed under each aftershock to obtain its collapse capacity and its capacity associated to demolition (i.e., the capacity to reach or exceed a 2% residual drift). The effect of additional sources of stiffness and strength (i.e., interior gravity frames and slab contribution) and the polarity of the aftershocks are examined in this study. Results of this investigation show that the collapse potential under aftershocks strongly depends on the modeling approach (i.e., the aftershock collapse potential is modified when additional sources of lateral stiffness and strength are included in the analytical model). Furthermore, it is demonstrated that the aftershock capacity associated to demolition (i.e., the aftershock collapse capacity associated to a residual interstory drift that leads to an imminent demolition) is lower than that of the aftershock collapse capacity, which mean that this parameter should be a better measure of the building residual capacity against aftershocks. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

云南鲁甸M_S6.5地震余震重定位及其发震构造   总被引：11，自引：11，他引：0  

房立华  吴建平  王未来  吕作勇  王长在  杨婷  钟世军 《地震地质》2014,36(4)

整合了鲁甸震区周边的云南省地震台网、昭通市地震台网、巧家台阵,以及流动台站2个月的震相观测数据,对鲁甸地震序列进行了重新定位,得到了1 750个地震的震源参数。重定位结果显示,余震有2个优势分布方向,分别为SE向和SW向,具有不对称的共轭分布特征。2个余震条带的展布长度相当,约为16km,夹角约100°。余震分布显示鲁甸地震的发震断层为高倾角的走滑断层。主震位于2个余震条带中间略偏西南的位置,早期余震主要沿NW-SE向垂直于昭通-鲁甸断裂分布,主震西南侧的余震可能为后期触发的。根据余震分布与周边断层的关系、主震震源机制、烈度分布的长轴方位,以及滑坡分布等资料,认为鲁甸地震的发震断层为NW向的包谷垴-小河断裂。包谷垴-小河断裂南北两侧无论是在地震活动、深部速度结构,还是块体运动方向和速率方面都存在显著差异,断裂北侧的高速异常可能是阻止余震向北继续扩展的主要原因。  相似文献   

芦山M7．0地震余震分布特征     

蔡一川  魏娅玲  苏金蓉 《地震地磁观测与研究》2014,(3):83-88

使用双差定位方法,对2013年4月20日08时02分芦山 M 7．0地震后近10天的余震进行重新定位,获得精度较高的重定位结果;在此基础上,对余震空间分布特征进行研究,推测芦山主震的发震断层可能为大川-双石主断裂东侧的一条次级隐伏逆冲断层。  相似文献