钙质土中重力串锚水平承载力特性有限元研究

目前没有规范给出串锚的水平承载力计算公式,为了利用有限元法研究串锚水平承载力特性,采用相关理论计算以及室内试验的方法来验证有限元法模拟计算的可靠性。实践证明,有限元法具有较高的计算精度。利用有限元分析软件ABAQUS建立了串锚-土体模型,模拟串锚在水平荷载作用下破坏过程,研究了串锚在水平荷载作用下破坏机理,从而得到了串锚水平承载力特性。在相同的工况条件下,串锚的水平承载力与其锚链长度有关,在一定范围内,增加锚链的长度可以提高串锚的水平承载力;串锚的水平承载力不是相应的单个锚的水平承载力相加,其水平承载力小于相应的单个锚水平承载力之和,在进行串锚水平承载力设计计算时应给与相应的考虑。     

Fuzzy comprehensive evaluation model for water resources carrying capacity in Tarim River Basin, Xinjiang, China

This paper explores the method of comprehensive evaluation of water resources carrying capacity and sets up an evaluation model applying the fuzzy comprehensive evaluation method. Based on the data of nature, society, economics and water resources of the Tarim River Basin in 2002, we evaluated the water resources carrying capacity of the basin by means of the model. The results show that the comprehensive grades are 0.438 and 0.454 for Aksu and Kashi prefectures respectively, where the current water resources exploitation and utilization has reached a relative high degree and there is only a very limited water carrying capacity, 0.620 for Kizilsu Kirgiz Autonomous Prefecture, where water resources carrying capacity is much higher, and in between for Hotan Prefecture and Bayingolin Mongolian Autonomous Prefecture. As a whole, the comprehensive grade of the Tarim River Basin is 0.508 and the current water resources exploitation and utilization has reached a relative high degree. Thus, we suggest that the integrated management of the water resources in the basin should be strengthened in order to utilize water resources scientifically and sustainably.     

Spatial partitioning between species of the phytoplankton-feeding guild on an estuarine intertidal sand flat and its implication on habitat carrying capacity

The fishery yield of Manila clams, Ruditapes philippinarum, increased considerably in the 1970s but has decreased rapidly since the middle 1980s on extensive intertidal sand flats in Ariake Sound (Kyushu, Japan). A survey conducted in 2004 on a 3.4-km² sand flat located in the central part of the Sound (Shirakawa sand flat) revealed four dominant species: two thalassinidean shrimps (Upogebia major and Nihonotrypaea japonica), which are deep-reaching burrow dwellers with strong bioturbation activities, and two bivalves (Mactra veneriformis and R. philippinarum). All four species belong to a phytoplankton (diatom)-feeding guild. In the late 1970s, the Manila clam population prevailed in high densities over the entire sand flat, whereas its distribution was restricted to the lowest quarter of the shore in 2004. In contrast, the population sizes and zones of occurrence of the other phytoplankton feeders have expanded in the absence of R. philippinarum, perhaps an indication of competitive release. After establishment, effects of the thalassinidean shrimps on sediment stability appear to have further reduced clam abundances. Across the sand flat in 2004, wet weight population biomass estimates for N. japonica, U. major, M. veneriformis, and R. philippinarum (whole body for shrimps and soft tissue for bivalves) were 304, 111, 378, and 234 tonnes, respectively. Based on Manila clam fishery yield records from Shirakawa, the carrying capacity of the Shirakawa sand flat in the late 1970s was estimated to be two times greater than the sum value for the whole phytoplankton-feeding guild in 2004. It is hypothesized that (1) the amount of phytoplankton determines the carrying capacity for the benthic community on the Shirakawa sand flat, with both phytoplankton and benthic biomass at maxima in the late 1970s, and (2) the subsequent increases in competition for space have caused further declines in the Manila clam population biomass to approximately one-eighth of its past value.     

昆承湖水流水质计算分析

在模拟昆承湖水流流场的基础上,模拟化学需氧量(CODMn)在湖水中的扩散情况;同时,利用昆承湖实测资料和水质的浓度场计算结果,得到其枯季环境容量.可以看出,昆承湖的流速较小,且方向由西北流向东南,可能是受长江径流和湖底西北高东南低的地形特征影响;从昆承湖的CODMn浓度实测值和计算值中,可以看出小于其水环境质量标准限值.这将进一步为实现常熟市湖泊水环境质量的不断提高、生态状况的持续改善与科学管理提供依据.     

Response and capacity of monopod caisson foundation under eccentric lateral loads

Monopod caisson foundation is a viable alternative for supporting offshore wind turbines located at shallow water depths. This foundation system has to resist overturning moment generated due to resultant lateral load, arising from wind and water wave action, that can act at any loading height above the seabed. This paper presents results of a numerical investigation performed to determine the influence of loading height, caisson geometry and superstructure load on the ultimate lateral capacity, initial stiffness, and soil failure zone of the foundation, when installed in very dense sand. Both the ultimate and serviceable states of the caisson foundation obtained from the analyses are represented in terms of envelopes plotted between lateral load and overturning moment. Simplified expressions, which take into account the influence of caisson geometry, loading height, and soil properties, are also presented to serve as a preliminary base for design of the monopod caisson foundation.     

环渤海湾海洋资源环境承载力定量研究

环渤海湾地区经济发展迅速但开发利用过度,生态问题突出。本文以社会环境学理论、系统论、可持续发展理论等为基础,建立了环渤海湾海洋资源环境承载力评价指标体系,利用单项评价法,以地级市为基本单位对环渤海湾地区的海洋资源环境承载力进行评价。结果表明滨州市的海洋资源环境承载力较好,其次为唐山市和天津市,沧州市的海洋资源环境承载力较弱。     

无标度网络上队列资源分配研究

研究了节点队列资源有限的条件下,无标度网络上的信息流动力学过程,发现了网络由自由流通到拥塞的相变现象,提出了一种基于节点度的队列资源分配模型.模型的核心是使节点i的队列长度与k^β_i成正比(k_i为节点i的度,β为分配参数).仿真结果表明,在网络使用最短路径算法进行信息包传送的条件下,β近似等于1.25时队列资源分配最合理,网络容量最大,且该最佳值与队列总资源多少以及网络的规模无关.     

桩基承载力自平衡试验方法在昆明地区的应用研究

概述了自平衡法的基本原理,对云南某化工有限公司5×105t/a合成氨煤气化装置中的三根试桩采用自平衡新方法进行了桩基承载力测试,对测试数据进行了整理和分析。应用结果表明,测试取得较好的工程效果。     

763长周期地震仪水平摆的安装调试和性能的一致性比测

本文以泉州台 763长周期地震仪水平摆的安装调试为例 ,介绍用“一致性比测法”检测 763长周期地震仪水平摆的安装调试结果。     

后注浆桩单桩极限承载力与其影响因素的分析

随着城市开发的速度越来越快,土地也日益变得珍贵,高层建筑得到了快速发展,为了满足高层建筑物越来越大的结构荷载的需要,桩长和桩直径也变得越来越大。在不大幅增加成本的前提下,后注浆技术提高了钻孔灌注桩的单桩承载力,并降低了建筑物的沉降,因此得到了更广泛的应用。简要介绍了后注浆工艺的承载力提高机理及几个工程实例,分析了注浆前后单桩极限承载力变化情况及部分影响因素,为普及应用积累了一些素材。