A developing inventory of tornadoes in France

The analysis of 304 French tornadoes shows that the most struck areas are the northwestern part of the country, the south and the east. Tornadoes occur mainly in spring and in summer; August is the month when the frequency is maximum. Tornadoes move mainly from southwest to northeast, except in the south where the direction is sometimes south to north. Thirty-six killer tornadoes were listed (12% of the cases); most of them with an intensity greater or equal to F3. The occurrence is approximately 15–20 tornadoes each year in France, and the annual risk probability of significant tornadoes in France is 0.66×10⁻⁵. This value is probably underestimated because all the tornadoes are not listed.     

川滇地震滑坡分布规律探讨

本文主要从宏观角度讨论了川滇地区地震滑坡的空间分布格局与环境条件的关系。地震滑坡灾害在空间上可分为四种不同程度的地区。地震滑坡不但受到地震强度、频度的控制,而且与各震区所处的环境条件密切相关。川滇地区的滑坡生成环境可分成三类。在这些环境因素的制约下,形成了自北而南地震滑坡灾害逐渐递降的发育趋势。从时间分布的讨论中可见,川滇地震滑坡自1870—1976年的百年内为高潮期。     

山地自然灾害（以泥石流为主）及其防治

我国是一个山地自然灾害严重的国家,尤其是泥石流、滑坡灾害。八十年代以来山地自然灾害频繁,泥石流、滑坡所造成经济损失超过30亿元。本文分析了灾害成因、分布特征以及山地自然灾害的预报和防治。     

花岗岩地区滑坡特征及防治对策——以湖南省平江县花岗岩滑坡为例

文章分析了湖南平江县花岗岩地区滑坡,在地形地貌、地层岩性、地质构造、水文地质条件、滑坡体、滑动面、滑动多期性等方面的典型特征。由于地表水和地下水是花岗岩地区滑坡中的主要影响要素,因此,提出对该类型滑坡应采用排水工程为主,并和其它防治措施相结合的方法进行防治。换言之,排水工程是滑坡防治中单独的一项措施,其效果应在同步进行的滑坡监测中予以验证。在滑坡治理的过程中,滑坡监测始终是滑坡防治的基础,防治的效果也需要监测工作来检验。     

渗透性与降雨强度对堆积层滑坡稳定性的影响

本文基于非饱和渗流理论及非饱和土的Fredlund双应力变量强度理论,对一沿岩土接触面滑动的堆积层滑坡模型,分别进行了8种条件下的降雨入渗数值模拟试验,研究了不同土体渗透性及降雨强度对滑坡稳定性的影响。结果表明:(1)堆积层滑坡的稳定性与土体的渗透性有密切关系,在降雨后的短期内,土体渗透性越好,滑面孔隙水压力升高越明显,滑坡的稳定性降低程度越大;(2)降雨期间,埋深较浅的滑面,入渗雨水能够较快到达,对滑坡稳定性的影响较大;(3)在相同的降雨时间内,降雨强度越大,滑坡稳定性降低速率越快;(4)降雨强度影响着滑坡发生的滞后性,在降雨总量一定的条件下,若降雨强度较大,雨停后,滑坡稳定性继续下降的程度较大;(5)降雨总量控制着滑坡的最终稳定性。     

Sedimentology,structure and age estimate of five continental slope submarine landslides,eastern Australia

Sedimentological and accelerator mass spectrometry (AMS) ¹⁴C data provide estimates of the structure and age of five submarine landslides (～0.4–3 km³) present on eastern Australia's continental slope between Noosa Heads and Yamba. Dating of the post-slide conformably deposited sediment indicates sediment accumulation rates between 0.017 m ka^–1 and 0.2 m ka^–1, which is consistent with previous estimates reported for this area. Boundary surfaces were identified in five continental slope cores at depths of 0.8 to 2.2 m below the present-day seafloor. Boundary surfaces present as a sharp colour-change across the surface, discernible but small increases in sediment stiffness, a slight increase in sediment bulk density of 0.1 g cm^–3, and distinct gaps in AMS ¹⁴C ages of at least 25 ka. Boundary surfaces are interpreted to represent a slide plane detachment surface but are not necessarily the only ones or even the major ones. Sub-bottom profiler records indicate that: (1) the youngest identifiable sediment reflectors upslope from three submarine landslides terminate on and are truncated by slide rupture surfaces; (2) there is no obvious evidence for a post-slide sediment layer draped over, or burying, slide ruptures or exposed slide detachment surfaces; and (3) the boundary surfaces identified within the cores are unlikely to be near-surface slide surfaces within an overall larger en masse dislocation. These findings suggest that these submarine landslides are geologically recent (<25 ka), and that the boundary surfaces are either: (a) an erosional features that developed after the landslide, in which case the boundary surface age provides a minimum age for the landslide; or (b) detachment surfaces from which slabs of near-surface sediment were removed during landsliding, in which case the age of the sediment above the boundary surface indicates the approximate age of landsliding. While an earthquake-triggering mechanism is favoured for the initiation of submarine landslides on the eastern Australian margin, further evidence is required to confirm this interpretation.     

青石梁近坝滑坡基本特征与稳定性分析

通过工程地质测绘、钻探、平硐及岩土测试等勘察工作,查明青石梁滑坡体积约81万m~3,为中型岩质顺层滑坡,现状整体处于基本稳定性状态。水库运行后或建坝前后叠加暴雨久雨滑体饱水等多种工况下,滑坡整体基本上处于欠稳定—不稳定状态,为此滑坡需要采取工程治理措施。经比较,建议结合大坝二期围堰建设对滑体中部、后缘予以削方减载(用作围堰填筑土料),使滑坡稳定达到安全标准。     

海底滑坡对置于海床表面管线作用力的CFD模拟

海底管线是海洋工程中用于传输原油和天然气等的重要通道,通常放置在海床表面或处于悬跨状态。本文采用计算流体动力学CFD法模拟了不同冲击角度下海底滑坡对置于海床表面的海底管线的作用,得到了管线所受的轴向荷载和法向荷载与滑坡冲击角度之间的关系。同时分析了沿冲击方向管线截面形状与管线所受阻力之间的关系。对已有研究进行拓展延伸,丰富了不同工况下轴向阻力系数和法向阻力系数的计算成果,得出了海底滑坡对置于海床表面管线冲击力的计算公式。     

青海大通西山滑坡稳定性分析及防治方案

通过对大通县桥头镇西山滑坡野外勘查,室内综合研究分析,查明大通县桥头镇西山滑坡的范围、规模、发育特征、形成机制、影响因素以及稳定性特征,评价和分析了其稳定性和破坏模式,并为滑坡灾害防治工程可行性研究和施工图设计提供地质资料。同时,对于西北类似滑坡勘查、治理具有一定的借鉴意义。     

露天煤矿边坡稳定性实例分析及优化设计

结合内蒙古某露天煤矿的边坡实例,综合运用现有的工程地质资料、理论分析以及计算等手段,对该露天矿边坡工程地质条件、稳定性进行了分析和评价,提出了优化设计方案和滑坡治理建议。最后,从技术和工程方面提出了露天矿边坡稳定性的防治措施。