基于灰色关联度理论的河北省太行山区下瓦岔泥石流灾害危险性评估研究

1999年8月14日发生在河北省太行山区的下瓦岔泥石流,冲毁了位于沟口的下瓦岔村的几十户人家,造成26人死亡,下瓦岔泥石流是河北省太行山区泥石流暴发的重灾区之一,其危险度研究对该区经济建设及防灾减灾意义重大。本文以灰色系统理论为基础,选取一次泥石流(可能)最大冲出量等2个主要危险因子及流域面积等9个次要危险因子进行多因素关联度分析,再对各危险因子赋予相应的权重,并结合下瓦岔泥石流灾害主要特征,确定各危险因子等级并赋值,最终求出下瓦岔泥石流危险度值,其结果与现场实际勘察的结果相吻合。研究表明,运用灰色关联法进行河北省太行山区下瓦岔泥石流危险度评价是实用的和有效的。     

基于物元可拓的熵值泥石流危险性评价

通过选取能够反映和体现泥石流危险性的8项重要参数指标作为泥石流危险性评价指标,运用物元可拓理论和熵值确定权重法,建立泥石流危险性评价的物元可拓模型。应用建立的物元可拓模型,对舟曲县15条典型泥石流沟的危险性进行评价,得到的评价结果与实际情况相符合,同时也说明基于物元可拓的熵值法能较真实地反映实际泥石流沟的危险性等级,证明该方法应用于泥石流危险性评价的有效性和可行性。     

基于CFX-ANSYS流固耦合的新型带支撑泥石流拦挡坝抗冲击性能分析

在常规的重力式泥石流拦挡坝基础上,提出了一种带钢支撑的钢-砼组合式拦挡结构.采用流固耦合分析方法,将CFX与ANSYS相结合,在Workbench运行环境下,对常规的重力坝与新型的带支撑拦挡坝进行了数值模拟计算及对比分析,探究了支撑布置范围、支撑高度、支撑间距等对结构极限抗冲击承载力的影响及其规律,验证了新型结构的优越性.计算分析过程中,特别引入了水利水电工程拱坝设计中的柔度系数C作为关键参数.结果表明:随着柔度系数C的增大,支撑对坝体极限抗冲击承载力的提高作用愈加显著,而常规坝体的极限抗冲击承载力随之降低,坝体设计中应充分考虑结构柔度的影响;应采用满布且高度接近坝高的支撑,同时,支撑间距不应过大,以2.0m为宜;坝体柔度系数C以14.0～21.0为宜,此时带支撑坝体的极限抗冲击承载力增幅可达10％ ～ 25％,支撑的加强效果较为可观,但柔度系数过大(C≥24.0)或过小(C≤12.0)均会显著降低支撑对坝体的加强作用,在工程应用中应根据实际情况判断是否设置支撑.     

西部山区泥石流对河滩地演变的地质环境效应--以云南省小江为例

河滩地是西部山区的重要土地资源,绝大部分山区河滩地因泥石流而生,又因泥石流的后期作用而可能消亡.以云南省小江为例,指出泥石流对西部山区河滩地形成的正面效应,同时也分析了泥石流对河滩地的淤埋、淹没和冲毁等负面作用,为西部山区河滩地的开发利用和保护提供了依据.     

Effects of Postfire Salvage Logging on Deadwood‐Associated Beetles

Abstract: In Canada and the United States pressure to recoup financial costs of wildfire by harvesting burned timber is increasing, despite insufficient understanding of the ecological consequences of postfire salvage logging. We compared the species richness and composition of deadwood‐associated beetle assemblages among undisturbed, recently burned, logged, and salvage‐logged, boreal, mixed‐wood stands. Species richness was lowest in salvage‐logged stands, largely due to a negative effect of harvesting on the occurrence of wood‐ and bark‐boring species. In comparison with undisturbed stands, the combination of wildfire and logging in salvage‐logged stands had a greater effect on species composition than either disturbance alone. Strong differences in species composition among stand treatments were linked to differences in quantity and quality (e.g., decay stage) of coarse woody debris. We found that the effects of wildfire and logging on deadwood‐associated beetles were synergistic, such that the effects of postfire salvage logging could not be predicted reliably on the basis of data on either disturbance alone. Thus, increases in salvage logging of burned forests may have serious negative consequences for deadwood‐associated beetles and their ecological functions in early postfire successional forests.     

新型带弹簧支撑抗冲击研究及其在泥石流拦挡坝中的应用

为了使结构或构件能够更好地承受住泥石流、爆炸等冲击荷载,设计出一种新型带弹簧的支撑(件)。运用显式动力分析方法,对冲击载荷作用下的这种支撑进行数值模拟,计算得到新型支撑的动力响应,并与普通支撑进行对比分析。结果表明,新型支撑能更好地防止冲击荷载作用下的结构过早发生塑性变形。另外,在泥石流防治结构中,引入这种新型支撑,设计出新型泥石流拦挡坝。运用有限元软件ls-dyna对新型泥石流拦挡坝进行大块石冲击模拟,并与普通重力式拦挡坝进行对比分析,得出新型拦挡坝坝底应力远小于普通泥石流拦挡坝的应力。研究结果表明,新型带弹簧支撑及新型泥石流拦挡坝的抗冲击效果非常明显。     

Woody debris in north Iberian streams: influence of geomorphology, vegetation, and management

The effect of stream geomorphology, maturity, and management of riparian forests on abundance, role, and mobility of wood was evaluated in 20 contrasting reaches in the Agüera stream catchment (northern Iberian Peninsula). During 1 year the volume of woody debris exceeding 1 cm in diameter was measured in all reaches. All large woody debris (φ > 5 cm) pieces were tagged, their positions mapped, and their subsequent changes noted. Volume of woody debris was in general low and ranged from 40 to 22,000 cm³ m⁻²; the abundance of debris dams ranged from 0 to 5.5 per 100 m of channel. Wood was especially rare and unstable in downstream reaches, or under harvested forests (both natural or plantations). Results stress that woody debris in north Iberian streams has been severely reduced by forestry and log removal. Because of the important influence of woody debris on structure and function of stream systems, this reduction has likely impacted stream communities. Therefore, efforts to restore north Iberian streams should include in-channel and riparian management practices that promote greater abundance and stability of large woody debris whenever possible.     

Marine Debris &; Plastics: Environmental Concerns,Sources, Impacts and Solutions

Marine debris (marine litter) is one of the most pervasive and solvable pollution problems plaguing the world’s oceans and waterways. Nets, food wrappers, cigarette filters, bottles, resin pellets, and other debris items can have serious impacts on wildlife, habitat, and human safety. Successful management of the problem requires a comprehensive understanding of both marine debris and human behavior. Knowledge is key for consumers to make appropriate choices when it comes to using and disposing of waste items. Education and outreach programs, strong laws and policies, and governmental and private enforcement are the building blocks for a successful marine pollution prevention initiative. The plastic industry also has a role to play in educating its employees and customers, and searching for technological mitigation strategies.     

四川色达县切都柯沟"7·8"泥石流灾害风险评价

2004年7月8日,四川甘孜州色达县歌乐沱乡切都柯沟暴发泥石流.由于前期断断续续一个多月的降雨,使得切都柯沟多处发生崩塌,大量松散固体物质含水量趋于饱和,致使在7月8日一场不大降雨的情况下触发了泥石流.这次泥石流灾害造成的损失虽不十分严重,但泥石流过程比较典型.我们将考察结果整理成文,并用已有的泥石流风险评价模型对其危险度、易损度和风险度作了分类评价,以期为今后的深入研究和防灾减灾实践提供基础.     

岷江上游泥石流灾害特征分析

岷江上游地区地质条件复杂,新构造运动强烈,地震活跃,地形起伏巨大,降水季节分配不均,对泥石流发育极为有利;而长期不合理的人类经济活动如过度采伐森林、毁林开荒、陡坡耕作、不合理弃渣等则对生态环境造成强烈破坏,加剧了泥石流灾害的发生,使岷江上游成为我国泥石流活动比较强烈及灾害比较严重的地区之一.研究该地区泥石流灾害,掌握其特征是防灾减灾所必需,对促进岷江上游地区社会经济发展和西部大开发具有重要意义.