关于高速滑坡的几个问题

高速滑坡问题是当前工程地质和环境地质学界极为关注的问题。本文对诸如滑体高速滑动所对应的时空界限、滑体滑动过程所产生的热效应以及空气浮托力等高速滑坡产生机制问题进行了初步探讨。     

构造因素与滑坡

本文首先简述了斜坡演化过程与构造运动的关系,然后阐明了滑坡的空间分布、活动周期及活动规模与构造因素的联系。在此基础上指出:构造因素是滑坡产生的基础,对滑坡分布具宏观控制作用,并与滑坡的活动周期和活动规模密切相关,是滑坡研究及其灾害预测、预防研究工作中值得重视的重要因素。     

Contribution of storms to groundwater recharge in the semi‐arid region of Karnataka,India

This paper describes the application of environmental isotopes and injected tracer techniques in estimating the contribution of storms as well as annual precipitation to groundwater recharge and its circulation, in the semi‐arid region of Bagepalli, Kolar district, Karnataka. Environmental isotopes ²H, ¹⁸O and ³H were used to study the effect of storms on the hydrological system, and an isotope balance was used to compute the contribution of a storm component to the groundwater. Some of the groundwater samples collected during the post‐storm periods were highly depleted in stable isotope content with higher deuterium excess relative to groundwater from the pre‐storm periods. Significant variation in deuterium excess in groundwater from the same area, collected in two different periods, indicates the different origin of air masses. The estimated recharge component of a storm event of 600 mm to the groundwater was found to be in the range of 117–165 mm. There was no significant variation in environmental tritium content of post‐storm and pre‐storm groundwater, indicating the fast circulation of groundwater in the system. After completion of the environmental isotope work, an injected radiotracer ³H technique was applied to estimate the direct recharge of total precipitation to the groundwater. The estimated recharge to the groundwater is 33 mm of the 550 mm annual precipitation during 1992. Copyright © 2003 John Wiley & Sons, Ltd.     

Numerical modeling of rainstorm-induced shallow landslides in saturated and unsaturated soils

For the assessment of shallow landslides triggered by rainfall, the physically based model coupling the infinite slope stability analysis with the hydrological modeling in nearly saturated soil has commonly been used due to its simplicity. However, in that model the rainfall infiltration in unsaturated soil could not be reliably simulated because a linear diffusion-type Richards’ equation rather than the complete Richards’ equation was used. In addition, the effect of matric suction on the shear strength of soil was not actually considered. Therefore, except the shallow landslide in saturated soil due to groundwater table rise, the shallow landslide induced by the loss in unsaturated shear strength due to the dissipation of matric suction could not be reliably assessed. In this study, a physically based model capable of assessing shallow landslides in variably saturated soils is developed by adopting the complete Richards’ equation with the effect of slope angle in the rainfall infiltration modeling and using the extended Mohr–Coulomb failure criterion to describe the unsaturated shear strength in the soil failure modeling. The influence of rainfall intensity and duration on shallow landslide is investigated using the developed model. The result shows that the rainfall intensity and duration seem to have similar influence on shallow landslides respectively triggered by the increase of positive pore water pressure in saturated soil and induced by the dissipation of matric suction in unsaturated soil. The rainfall duration threshold decreases with the increase in rainfall intensity, but remains constant for large rainfall intensity.     

三峡库区生基包滑坡监测及成果分析

生基包滑坡监测属于三峡库区奉节县三期地质灾害监测预警项目之一,该滑坡位于长江左岸,临近人口稠密的安坪乡集镇,地理位置重要。三峡水库175 m蓄水后,其变形破坏特征有何表现？对航道安全运营有无潜在威胁？是否会对滑坡体上的重要建筑及村民生产生活构成危害？针对这些问题,首先分析了滑坡的工程地质特征及主要的影响因素;其次,确立以4种监测手段为主、人工巡查为辅的监测方案;通过对大地变形GPS、深部位移、滑坡推力等几种监测方法的运用及对其成果进行分析研究,以实例说明其在滑坡监测中的应用;再次,结合宏观人工巡查进行对照分析,以充分说明大地变形、深部位移和滑坡推力监测在实际运用中的可行性;最后,根据监测结论提出对生基包滑坡防治的建议。     

滑坡体三维地质建模与可视化分析

针对滑坡地质研究的自身特点,提出了面向滑坡地质体三维建模的NURBS-BRep混合数据结构和地质结构单元实体构造技术.通过对滑坡基础地质数据的预处理、滑坡数字地形和滑动面的三维建模、地质结构面的系统构造、地质结构体的生成和显示,形成了一套完整的滑坡三维地质模型的构建方法.将该方法应用于某水库滑坡,建立了相应的三维滑坡地质模型,并基于此模型进行了三维剖切分析、数字钻孔、等值线生成、滑块自动剖分、滑坡失稳可视化动态模拟和滑坡体方量精确计算等一系列实用的可视化分析,为滑坡稳定性的准确计算和客观评价提供了有力的支持.     

采用钻孔倾斜仪监测滑坡深部水平位移方法和仪器的研究

介绍了目前滑坡深部水平位移钻孔倾斜仪人工监测方法存在的问题,钻孔深部位移自动化监测通信方法的选择。地质滑坡灾害监测中广泛使用钻孔倾斜仪,介绍了CZ-2型钻孔倾斜仪的构成及现场测试方法。     

基于贡献权重叠加法的滑坡风险区划

贡献权重叠加法是对滑坡本底因子和承灾体因子在滑坡发育中的贡献率进行统计后,通过贡献率均值化、规一化处理,利用权重转换模型计算出每一个因子内部的权重——自权重和因子相互之间的权重——互权重。将滑坡因子、承灾体因子和两者的自权重、互权重分别相乘叠加,得到滑坡危险度和易损度区划结果,再将2项结果相乘得出滑坡风险区划结果。     

中国开辟区不利开采地形类型及其分布

利用1998年"大洋一号"调查船近海底作业所获的深拖海底电视和照相系统资料,对中国开辟区不利开采地形类型及其分布特征进行了研究,并对海底地形的坡度进行了计算,结果表明:(1)中国开辟区东、西两区海底的东向坡和西向坡是均衡分布的。东、西两区海底地形坡度的分布特征明显不同,东区海底地形坡度以0～15°为主,而西区坡度大于3°的地形则很少。坡度大于5°的地形主要分布于坡脚处,特别是坡度超过15°的地形总是出现在水深变化的转折点处。(2)研究区不利开采地形可分为坡度为5～15°和大于15°两种类型,东区地形坡度大于5°的不利开采地形比西区多14%,东区坡度大于15°的地形为3.6%,比西区(仅为1.4%)多,东、西两区都有少量坡度近90°的地形出现,并且这种地形在东区所占比率比西区大,说明东区断崖、陡坎和断裂沟槽比西区多,地形也更为复杂多变。     

地形坡度对多金属结核分布的控制作用

选取我国东太平洋多金属结核开辟区内的一个区域作为研究区,利用人工神经网络中应用最为广泛的BP网络,建立控制多金属结核分布的地质因素与多金属结核分布之间的映射关系,探讨地形坡度对多金属结核分布的控制作用.结果表明,在经度、纬度、水深、坡度四个因素中,坡度对结核分布影响程度最大;多金属结核主要分布于坡度小于5°的地方;当坡度小于5°时,丰度与地形坡度呈正相关,品位与地形坡度呈负相关,丰度与品位呈负相关;品位与坡度似呈指数关系,坡度增大,品位降低.