特殊土基对渠道防渗工程的危害及其防治措施

我国 (尤其是西部地区 )广泛分布着特殊土 (盐渍土、膨胀土及湿陷性黄土 ) ,对渠道防渗工程建设带来严重的危害。因此 ,笔者为了与同行们就解决此问题进行讨论 ,特就特殊土的分布概况、主要性能特点及对渠道防渗工程的危害作了简介后 ,着重对防治措施提出了一些看法 ,供交流与讨论。     

自升式钻井平台插桩深度计算及几个问题的探讨

在海上油气的勘探和开发中，自升式钻井平台发挥了很大的作用。自升式钻井平台就其基础类型不同分为桩基式和沉垫式2种。本文就桩基式钻井平台的桩靴在均一黏性土、砂土及粉土上的插桩深度计算方法及其强度参数的选取等问题进行探讨。     

水泥土力学性能和耐久性能简介与分析

在介绍水泥土的基础上，着重讨论了影响水泥土力学性能和耐久性能的主要因素，以及水泥土增强改性的措施，最后提出了水泥土的可能应用前景。     

油罐外部腐蚀及防护技术

介绍了石油化工企业原油储罐和成品油储罐的外腐蚀情况和影响因素。外腐蚀主要包括罐顶、罐底板和外壁的腐蚀。根据有保温层和无保温层的具体情况,提出了适宜的防腐蚀措施。指出：在两种情况下,罐顶和罐壁的防护均应以涂料防护为主,但选择的涂层体系有所不同；罐底板的防护则应以电化学保护为主,并应根据具体情况分别选择牺牲阳极法和外加电流法。     

黄土高原水土保持世界银行贷款项目的经验与启示

黄土高原水土保持世界银行贷款项目以其扎实细致的前期准备,科学严密的组织与管理,高起点、高质量地在黄土高原地区建成了一大批综合治理典型,取得了多方面的成功经验,特别是该项目在实施过程中引进的先进管理理念、高效的组织管理体系以及资金"报账制"、政府采购、监测评价、年度检查、中期调整等"细、严、实"的创新管理机制,对于黄土高原地区乃至全国水土保持管理工作的创新与发展,产生了重要影响.     

Nitrate leaching during establishment of willow (Salix viminalis) on two soil types and at two fertilization levels

The production of willow in short rotation is expected to result in low nitrate leaching losses as is the case with other permanent crops. However, there is a risk of leaching of nitrate during establishment when the plant cover is limited. Nitrate leaching was followed for three years from the establishment in 1993 of willow (Salix viminalis) at two sites, a coarse sand at Jyndevad and a loamy sand at Foulum. Two levels of nitrogen, 0 or 75 kg N/ha in NPK, were applied annually, though only 38 N/ha was applied in the first year.

Leaching was calculated from usually weekly measurements of the nitrate concentration in soil solution and relating with the amount of percolation based on measured precipitation and changes in the soil water content over the sampling periods. Mean leaching for the three periods 1993–94, 1994–95 and 1995–96 amounted to respectively 142, 61 and 0 kg N/ha at Foulum and to 130, 9 and 4 kg N/ha at Jyndevad. The high leaching in the first year was caused by an unusually high content of mineral N in the soil at the start of the experiment. The absence of any leaching 1995–96 at Foulum was due to very low precipitation and a consequent lack of percolation. For the first period (1993–94) the fertilized treatment increased leaching by 32 kg N/ha compared to no fertilizer as a mean of the two sites, while the difference for the following two periods was reduced to 1–2 kg N/ha. It is concluded that application of nitrogen should be avoided in the year of planting of willows, while in the following years75 kg N/ha can be given without risk of increased leaching.     

支护结构侧压力计算方法研究

针对选用水土合算方法与水土分算方法及采用不同指标对水土侧压力计算结果的影响．在理论分析基础上结合工程原型观测数据对其进行了讨论．     

New Methodology for Optimal Operation of Soil Aquifer Treatment Systems

A new methodology is presented in thisarticle for computing the optimal operation of soilaquifer treatment systems. The mathematical problemis stated as a discrete-time optimal control problemto maximize infiltration subject to various physicaland operation constraints. The methodology is basedupon solving the discrete-time optimal control problemusing a successive approximation linear quadraticregulator interfaced with a simulator. Theunsaturated flow model HYDRUS is modified to simulatethe water content distribution, the infiltrationprocess, and the draining process. A penalty functionmethod is used to treat the bound constraints on thewater content and the cycle time. Sample problems aregiven to illustrate the capability of the model tosolve the optimal operation of soil aquifer treatment systems.     

RELATIONSHIP AMONG EVAPORATION FLUX OF GROUNDWATER, DEPTH OF WATER TABLE AND NEGATIVE PRESSURE HEAD IN BARE SOIL

1.　 INTRODUCTIONThe crisis of water resources is a global problem.Compared with other countries,Chi-na relatively falls shortof water resources.The amount of water resources per capita is justone fourth as the world average value. The distribution of water resources is outof balance.81 % ofthe water resources is concentrated in the reach of the Yangtse River and the south-ern areas of China,while only1 9% is in the areas of the north to the Yangtse River,inwhich the population is4 5.3%…