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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Rama Mohan Kurakalva Narasimha Murthy Nyasavajhala Phani Homeshwari Mamidi Venkata Anjaiah Kanukuntla 《中国地球化学学报》2006,25(B08):202-203
A simple and rapid procedure to extract organochlorine pesticides (OCPs) from sediments by means of microwave energy is proposed. Sediment samples were irradiated with microwaves in a closed vessel system while immersed in hexane-acetone (1 : 1, v/v). The sample extracts were cleaned up using solid phase extraction with Florisil as adsorbent. Pesticides were eluted with hexane-ethyl acetate (80 : 20, v/v) and determined by gas chromatographic separation with electron capture detection. Three oven programs were assayed with two different solvent mixtures in order to achieve adequate experimental conditions for the complete extraction of organochlorine pesticides from the matrix. Different variables such as the composition of extraction solvent, 相似文献
32.
Performance of Mortar and Chemical Grout Injection into Surrounding Soil When Slurry Pipe-jacking Method is Used 总被引:1,自引:0,他引:1
Hideki Shimada Takashi Sasaoka Saeid Khazaei Yasuhiro Yoshida Kikuo Matsui 《Geotechnical and Geological Engineering》2006,24(1):57-77
Small-diameter shallow tunnels are often being built by using the slurry pipe-jacking method. This system involves the pushing
or thrusting of a drivage machine and concrete pipes into the ground. Chemical grout injection into the surrounding soil around
the tunnel is carried out after the drivage and pushing processes are finished. The purpose of the chemical grout injection
is to maintain permanent stability of the surrounding soil. However, the behavior of the chemical grouting material in the
surrounding soil around the tunnel and the amount of optimum injection is not clearly understood. From these points of view,
this paper discusses the performance of the chemical grouting material, when it is injected into the surrounding soil around
the tunnel, by means of 2-D Eulerian–Lagrangian seepage analysis. Moreover, the effectiveness of the chemical grout injection
was evaluated by using the non-linear finite element method. This investigation show when the range of the grouted zone is
designed; it is necessary that the relationship between Young’s modulus of the soil/grouted zone and the confining stress
be taken into consideration in order to establish effective, economical and safe chemical grout injection system. Understanding
the performance of the seepage/dispersion behavior of the chemical grout and the characteristics of soil/ grouted zone is
also important. 相似文献
33.
Substantial damage to water supply systems, including water delivery pipelines, water treatment plants, reservoirs, and water
storage tanks, was reported after the 1999 Chi–Chi Taiwan Earthquake. This paper first summarizes the damage survey and then
presents the results of seismic fragility analysis for underground pipelines. Construction blueprints of the water delivery
pipelines and repair work orders of 11 townships and cities in the disastrous area were digitized into a Geographical Information
System (GIS) for analysis and assessment. With the aid of the GIS system, we found that PVC pipes made up 86% of water delivery
pipelines while steel, cast iron, ductile iron, PE and others took the rest. Therefore, this paper focuses on the fragility
analysis of PVC pipes. Three different methods were applied to derive the fragility relations between the PVC water pipes
having nominal diameters (approximately inner diameters) greater than or equal to 65 mm and earthquake intensity parameters
such as peak ground acceleration and peak ground velocity. The results were then examined with those of other countries. The
discrepancy between our results and the empirical equation used by HAZUS, an earthquake loss estimation software developed
by the Federal Emergency Management Agency was not significant. 相似文献
34.
35.
福建平潭虎潮山滑坡成因机理分析与评价 总被引:3,自引:0,他引:3
虎潮山滑坡位于平宏公路12k 704~12k 884段北侧山坡体上,是平潭海岛通往陆地的唯一公路通道。论文通过定性的工程地质分析和定量计算评价了虎潮山坡体稳定性的变化趋势,提出改建公路超挖深切坡脚和持续长时间强降雨导致的孔隙水压力作用是边坡发生滑动破坏的主要因素。 相似文献
36.
37.
基于GIS的商业网点选址研究与实现 总被引:2,自引:0,他引:2
利用平面/网络优化模型,综合权衡市区选址的基本费用及商业网点日常经营的成本,引入交通便利因子作为限制条件,并运用直接搜索的Dixon方法,加强了不确定性选址问题的约束条件,降低不确定性问题计算的复杂度,减少在选址问题实现中主观因素对选址结果的影响。最后以某区新建商业网点选址为例,详细分析了直接搜索算法应用的具体过程。 相似文献
38.
This paper describes an extension to the Combined Hydrology And Stability Model (CHASM) to fully include the effects of vegetation and slope plan topography on slope stability. The resultant physically based numerical model is designed to be applied to site‐specific slopes in which a detailed assessment of unsaturated and saturated hydrology is required in relation to vegetation, topography and slope stability. Applications are made to the Hawke's Bay region in New Zealand where shallow‐seated instability is strongly associated with spatial and temporal trends in vegetation cover types, and the Mid‐Levels region in Hong Kong, an area subject to a variety of landslide mechanisms, some of which may be subject to strong topographic control. An improved understanding of process mechanism, afforded by the model, is critical for reliable and appropriate design of slope stabilization and remedial measures. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
39.
40.
Horizontal and vertical components of earthquake ground motions at liquefiable sites 总被引:1,自引:0,他引:1
Field observations on ground motions from recent earthquakes imply that current knowledge is limited with regard to relating vertical and horizontal motions at liquefiable sites. This paper describes a study with the purpose of clarifying this emerging issue to some extent. A series of numerical analyses is carried out on a liquefiable soil deposit with a verified, fully coupled, nonlinear procedure. It is shown that the transformation of vertical motions in the deposit differs considerably from the transformation of horizontal motions. Both the amplitude and frequency content of the horizontal motions are strongly dependent on the shaking level or the associated nonlinear soil behavior. The transfer function for vertical motions is however likely to be independent of the intensity of input motions; no reduction in the amplitude occurs even in the case of strong shaking. The results are shown to be in consistence with the laboratory observations on shaking table tests and recent field observations that less nonlinearity exists for vertical motions. It is also shown that the possibility exists for using information on spectral ratios between the horizontal and vertical surface motions to quickly identify in situ soil behavior and liquefaction that are not readily covered by conventional field or laboratory experimentation procedures. 相似文献