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991.
Dam-break risk analysis of the Attabad landslide dam in Pakistan and emergency countermeasures 总被引:1,自引:0,他引:1
Xiaoqing Chen Peng Cui Yong You Zunlan Cheng Asif Khan Chengyin Ye Shu Zhang 《Landslides》2017,14(2):675-683
The Attabad landslide dam caused significant property losses and many human casualties in Pakistan, and also greatly affected the operation of the China-Pakistan Karakoram Highway (KKH). This paper discusses the risk of dam breach and hazards to the KKH project construction site following a dam breach. The paper examines the following three topics. (1) The geomorphologic dimensionless blockage index (DBI) and the analogy method were used to analyze the stability of the Attabad landslide dam. The long-term behaviors of landslide dams downstream of the Attabad landslide dam indicate that the risk of a dam breach exists, but the probability of a total dam failure is low. (2) The peak discharge of a potential breach of the Attabad landslide dam was calculated for scenarios in which 1/4, 1/3, 1/2, and total failure of the dam was breached. The potential breach discharge decreases with the downstream distance. (3) The potential impacts of the landslide dam breach on the KKH project construction site were analyzed. Based on the composition of the landslide dam, the probability of a 1/3 dam breach is high. To ensure the safety of downstream areas, disaster preparedness plans that correspond to the 1/2 dam breach scenario should be developed. Based on experience in addressing the landslide dam that was caused by the Wenchuan Earthquake, artificial controlled drainage measures are suggested and provide a technical reference for addressing the Attabad landslide dam and achieving recovery and normal operation of KKH. 相似文献
992.
内蒙古北山地区盘陀山一带长城纪古硐井群碎屑锆石LA-ICP-MS U-Pb年龄及其地质意义 总被引:3,自引:3,他引:0
长城纪古硐井群作为内蒙古北山地区古老褶皱基底之上的第一个沉积盖层,尚未获得可靠的年龄资料,前人只是根据其产出的层位和岩石组合特征与燕山地区的长城系对比后,将其置于中元古代长城纪。对古硐井群变质长石石英砂岩中碎屑锆石进行了LA-ICP-MS U-Pb测年,结果显示,锆石~(207)Pb/~(206)Pb年龄数据90%介于1.3~2.2Ga之间,其余年龄介于2.4~3.2Ga之间,峰期在1.6~2.0Ga之间,最年轻的碎屑锆石~(207)Pb/~(206)Pb年龄为1393±50Ma。通过对比碎屑锆石的年龄频谱和周围古地块的形成时代,碎屑锆石的U-Pb年龄限制了古硐井群的沉积时代,应为中元古代蓟县纪,古硐井群的沉积物可能来自北山-阿拉善和塔里木-敦煌地块。 相似文献
993.
994.
阵列式观测是探地雷达系统研制和新型探测方法的一个重要发展趋势,而同形多源并发地下目标响应特征分析成为系统研制和数据处理研究的基础和前提。阵列式天线的多源并发信号及目标反射信号存在复杂的极化特性,但同时也包含更多目标特征的响应信息。本文针对基于似平面波探地雷达系统,分析了目标体在极化平面波照射下的响应特征,从多极化信号角度分析典型地下目标体形态特征;并采用时域有限差分正演分析方法,通过对阵列天线接收到的数据沿时间轴进行积分来获得目标在地表投影的分布情况,分析了一维及二维分布的收发天线阵列对目标的检测。研究成果表明,多极化综合特征分析能够有效改善目标检测的稳定性,提高目标响应信号的信噪比,减弱天线方向图和目标散射截面闪烁对数据剖面的影响,降低数据处理和解释的难度。 相似文献
995.
With the rapid development of the subway rail transit, the effect of the cyclic loading on the surrounding foundations and buildings has drawn wide attention. In addition to the in situ tests and the laboratory triaxial tests, microscopic tests also provide an effective way to clarify the physical and mechanical characteristics of soils. On the other hand, the characteristics of the soft silty clay before and after freezing–thawing has been less studied. In this paper, the scanning electron microscope (SEM) tests following the cyclic triaxial tests of silty clay layer were performed to investigate the variations of the microscopic pore structures of the layer before and after freezing–thawing. The corrected Otsu method was used to obtain the binary SEM images of silty clay. The porosity results demonstrate that the magnifications from 1000× up to 5000× were suitable for observation of the silty clay microstructures. The binary SEM images of soil pore structures were quantitatively analyzed, including the porosity, the size distribution, the pore shape coefficient, the pore orientation distribution and the fractal dimension. The pore orientation of samples without loading is arranged in the horizontal direction, while the pores of samples under cyclic loadings are arranged in the vertical. After freezing–thawing, the mean anisotropy value of the microscopic pore structures increased about 12% and the porosity of samples without loadings increases about 11.24%. The lower the freezing temperature is, the larger the porosity within the samples becomes. However, the freezing–thawing has little effect on the pore shape coefficient of the silty clay. The porosity of the silty clay increases with an increase in pore diameter, but it decreases with the increase in excess pore pressure. In addition, the microscopic pore structures of the silty clay exhibit fractal characteristics. The fractal dimension is reduced by the disturbance from the effect of freezing–thawing, coupled with the effect of cyclic loading. 相似文献
996.
Estimating the contribution of glacial meltwater to Ranwu Lake,a proglacial lake in SE Tibet,using observation data and stable isotopic analyses 总被引:1,自引:0,他引:1
Jianting Ju Liping Zhu Junbo Wang Yingying Cui Lei Huang Ruimin Yang Qingfeng Ma Lun Luo Yongjie Wang 《Environmental Earth Sciences》2017,76(5):229
It is important for both current monitoring and paleoenvironmental research conducted on proglacial lakes and their adjacent glaciers to clarify the hydrological processes operating on these lakes. However, in remote regions with limited accessibility it may be difficult to study hydrological processes by direct monitoring. In this study, we use measurements of stable isotopic compositions to trace the multiple water sources contributing to Ranwu Lake, a proglacial lake in south-eastern Tibet. Using stable isotopic data from precipitation, inflowing rivers and the lake water, a water and isotope mass balance modelling method was used to calculate the ratio of evaporation to input. Subsequently, using hydrological and climatic data for the outflow, the largest inflow and precipitation, other hydrological elements of the lake water balance were also calculated. The results demonstrate that the ratio of evaporation to inflow is as low as 0.009, the lowest value observed for the Tibetan Plateau, indicating that Ranwu Lake is a through-flow lake with a very short retention time. Glacial meltwater accounts for at least 55% of total runoff, the highest value observed for the Tibetan Plateau, indicating that the sediments of Ranwu Lake may have considerable potential for reconstructing variations in the activity of the local glaciers. Finally, we note that it may be inappropriate in this glacier-fed lake to use the intersection of the local meteoric water line with the lake water line for determining the isotopic composition of the input water, and this possibility must be carefully considered when stable isotope mass modelling is used in proglacial lakes. 相似文献
997.
Tingting Han Hongwei Ji Huixin Li He Cui Tian Song Xiaojuan Duan Qianlin Zhu Feng Cai Li Zhang 《中国海洋大学学报(英文版)》2017,16(3):455-460
Ion chromatography-ultra violet-hydride generation-Atomic Florescence Spectrometry was applied to detect 5 arsenic species in seafoods. The arsenic species studied include arsenobetaine(As B), arsenite(As(III)), dimethylarsinic acid(DMA), monomethylarsonic acid(MMA), and arsenate(As(V)), which were extracted from samples using 2% formic acid. Gradient elution using 33 mmol L~(-1) CH_3COONH_4 and 15 mmol L~(-1) Na_2CO_3 with 10 mL CH_3CH_2OH at pH 8.4 allowed the chromatographic separation of all the species on a Hamilton PRP-X100 anion-exchange column in less than 8 min. In this study, an ultrasound extraction method was used to extract arsenic species from seafood. The extraction efficiency was good and the recoveries from spiked samples were in the range of 72.6%–109%; the precision between sample replicates was higher than 3.6% for all determinations. The detection limits were 3.543 μg L~(-1) for As B, 0.4261 μg L~(-1) for As(III), 0.216 μg L~(-1) for DMA, 0.211 μg L~(-1) for MMA, and 0.709 μg L~(-1) for As(V), and the linear coefficients were greater than 0.999. We also developed an application of this method for the determination of arsenic species in bonito, Euphausia superba, and Enteromorpha with satisfactory results. Therefore, it was confirmed that this method was appropriate for the detection of arsenic species in seafood. 相似文献
998.
The initiation mechanism of debris flow is regarded as the key step in understanding the debris-flow processes of occurrence, development and damage. Moreover, migration, accumulation and blocking effects of fine particles in soil will lead to soil failure and then develop into debris flow. Based on this hypothesis and considering the three factors of slope gradient, rainfall duration and rainfall intensity, 16 flume experiments were designed using the method of orthogonal design and completed in a laboratory. Particle composition changes in slope toe, volumetric water content, fine particle movement characteristics and soil failure mechanism were analyzed and understood as follows: the soil has complex, random and unstable structures, which causes remarkable pore characteristics of poor connectivity, non-uniformity and easy variation. The major factors that influence fine particle migration are rainfall intensity and slope. Rainfall intensity dominates particle movement, whereby high intensity rainfall induces a large number of mass movement and sharp fluctuation, causing more fine particles to accumulate at the steep slope toe. The slope toe plays an important role in water collection and fine particle accumulation. Both fine particle migration and coarse particle movement appears similar fluctuation. Fine particle migration is interrupted in unconnected pores, causing pore blockage and fine particle accumulation, which then leads to the formation of a weak layer and further soil failure or collapses. Fine particle movement also causes debris flow formation in two ways: movement on the soil surface and migration inside the soil. The results verify the hypothesis that the function of fine particle migration in soil failure process is conducive for further understanding the formation mechanism of soil failure and debris flow initiation. 相似文献
999.
Estimation of ecological water requirements based on habitat response to water level in Huanghe River Delta, China 总被引:3,自引:0,他引:3
Baoshan Cui Yanyan Hua Chongfang Wang Xiaolin Liao Xuejie Tan Wendong Tao 《中国地理科学(英文版)》2010,20(4):318-329
In recent years,wetland ecological water requirements (EWRs) have been estimated by using hydrological and functional approaches,but those approaches have not yet been integrated for a whole ecosystem.This paper presents a new method for calculating wetland EWRs,which is based on the response of habitats to water level,and determines water level threshold through the functional integrity of habitats.Results show that in the Huanghe (Yellow) River Delta water levels between 5.0 m and 5.5 m are required to maintain the functional integrity of the wetland at a value higher than 0.7.One of the dominant plants in the delta,Phragmites australis,tolerates water level fluctuation of about ± 0.25 m without the change in wetland functional integrity.The minimum,optimum and maximum EWRs for the Huanghe River Delta are 9.42×106 m3,15.56×106 m3 and 24.12×106 m3 with water levels of 5.0 m,5.2 m and 5.5 m,corresponding to functional integrity indices of 0.70,0.84 and 0.72,respectively.A wetland restoration program has been performed,which aims to meet these EWRs in attempt to recover from losses of up to 98% in the delta's former wetland area. 相似文献
1000.
进一步研究了可压缩流边界层系统解的一些性质,给出了可压缩边界层系统等价的奇异积分方程解存在时参数所在的区间,并通过研究等价的奇异积分方程解的性质,得出可压缩层流边界层系统给出剪应力函数厂和温度函数g的一些结果. 相似文献