Impact of oasis establishment on underground environment in salinized sandy lands

The salinized sandy lands are the important reclaimable reserve wastelands in thesouth area of the Xinjiang Uygur Autonomous Region of China. But it is necessary that the eco-logical environment of the area is not destroyed by action of oasis development. The main factor tohinder oasis development is land salinization. Rational oasis establishment rebuilds wastelandswith lower productivity and utilization efficiency for the growth of agriculture, forestry, and stock raising. The results of surveying sub-soil environment of Aimugaike. Awati oasis in Hotian County ofthe Xinjiang Uygur Autonomous Region show that the underground water and soil environment arenot deteriorated under the rational management and administration, which could be coordinatedfor obtaining economic and environmental benefit. During the oasis establishment period from1997 to 1999, the plowland area has reached 166.7 hm2, and the seed cotton yield per unit areahas reached 2250 kg @ hm-2, the area of timber forest and active sand break forest has reached 20hm2, the area of fruit trees is 71.5 hm2; and the soil moisture has decreased from 22.07% to18.12%. In the first year of oasis establishment, the soil type has changed salt soil into light saltsoil, in the second year the soil has been out of salt harm; and the content of soil organic matter intopsoil has increased obviously.     

新疆策勒县绿洲沙害的治理

新疆策勒县绿洲处于塔克拉玛干沙漠南缘,沙害极其严重。经过6年的治理,现已从绿洲向外依次初步建成了窄林带多带式防沙林网、人工灌木林、固沙草带及拦沙河,构成长10公里、宽4.55公里的绿色屏障,为绿洲内的农牧业生产提供了较为适宜的生态条件。     

桩基础非线性工作性状的室内模型试验分析

通过对单桩、带承台单桩和不同桩距群桩的模型试验结果分析 ,并与群桩试验的数值计算结果对比 ,总结了群桩中桩体的荷载传递规律 ;描述了板底土体反力和板下土体附加应力分布特性 ;比较了不同桩距群桩的荷载分担状况。通过试验结果的分析 ,得出桩的遮拦作用提高了承台下土体极限承载力的结论 ,为理论研究提供了试验依据 ;同时对桩的非线性工作状况进行分析 ,得出大桩距群桩受荷时桩先进入非线性然后承台下土体再进入非线性的结论。试验结果即验证了复合桩基非线性理论的若干假定 ,又为进一步研究提供了试验依据。     

考虑上部结构的桩筏基础非线性共同作用分析

当前虽然已有考虑桩筏非线性的设计,但仍无人在此基础上,考虑上部结构。因此考虑上部结构,进一步认识其与桩筏基础非线性共同作用机理,优化桩筏基础设计,具有重要的现实意义。本文以子结构法凝聚上部结构的荷载及刚度,以平面壳体单元模拟筏板,按有限层法模拟桩土之间的弹性相互作用,用广义剪切位移法模拟桩的非线性工作性状,建立了一种考虑上部结构共同作用的桩筏基础非线性分析方法,并编制了分析程序。通过实例分析,探讨了上部结构与桩筏基础非线性共同作用的机理,研究了合理布桩方式,探讨了以差异沉降为目标的优化设计的可能途径。     

城轨交通高架线环境振动的仿真与预测

基于轮轨相互作用原理,建立了城轨交通高架线路列车振动荷载激励函数。将该激励力作用在有限元软件建立的三维轨道支承结构和土体传播路径计算模型上,对地铁运行引起的周边环境振动响应进行了仿真模拟,并利用现场实测数据进行了比较和验证。进一步,分析了列车运行速度和场地土特性对环境振动的参数影响。在对各参数的影响特征进行了定量分析的基础上,通过统计分析,建立了城市轨道交通高架线路环境振动的振级预测公式,并利用现场实测数据进行了验证。研究表明,仿真模拟和预测结果能够较为真实的反映城轨交通高架线路运行引起的环境振动的实际情况。