木本植物人工湿地在湖泊富营养化修复中的应用展望

人工湿地是湖泊富营养化修复的先锋技术。在人工湿地的植物研究中,相对于草本植物,木本植物的研究进展极其缓慢。文章对国内外人工湿地中木本植物的研究工作进行综述,并展望木本植物在湖泊富营养化修复中的应用前景。     

降尘中氮磷含量的研究

通过对杭州西湖北山路春夏两季(3～8 月)降尘的采集和实验测定其中总氮(TN)和总磷(TP)的含量,分析出该地区降尘的粒径质量分布特点为较细颗粒的质量含量高于较粗颗粒的质量含量且较细颗粒的氮磷含量也高于较粗颗粒的氮磷含量,得出北山路降尘所携带的氮会对北里湖水体的水质造成潜在威胁,并给出建议对策.     

湖库型饮用水水源地保护区保护研究-以大溪水库为例

科学合理的保护饮用水水源地对于保障饮用水水质安全和人民身体健康极为重要.以大溪水库为例,分析大溪水库饮用水水源地存在的环境问题及造成环境问题的原因,从污染控制、自然保护、建设项目管理等方面着手,提出强化大溪水库饮用水水源地的保护措施和对策.     

膨润土防水毯在新乡医学院人工湖改造工程中的应用

膨润土防水毯既具有土工材料的特性,又具有优异的防水性能。本文介绍了膨润土防水毯在新乡医学院人工湖工程中的应用,分析了基面处理、材料裁剪、节点处理等关键环节,介绍了重点、难点以及不同部位的施工要点。     

连环湖水禽狩猎场水质环境的评价研究

利用理化监测和生物监测相结合的实验方法对连环湖狩猎场的水质进行评价研究.在主成分分析模型的基础上对连环湖狩猎场水质的理化指标的监测结果进行聚类分析,同时利用微核试验进行水质的生物监测研究.认为连环湖水域中的部分渔业用水水源的水质已受到轻度污染,并且对生物具有潜在的毒性效应.     

渤海浅层气防窜水泥浆体系的研究与应用

环空带压是渤海湾浅层气固井存在的一大技术难题,为此根据渤海湾浅层气特征,分析固井技术难点,设计了2种固井方案。方案A引入膨胀材料或增塑材料,方案B引入自修复材料。实验结果显示,当同时引入膨胀剂与纤维后,96 h胶结强度仅提高15%左右,因此可知水泥浆的防窜能力不会有明显改善。而引入自修复材料后,水泥石的裂缝封堵率达到95%以上。分析认为,方案B的自修复封堵性能和工程性能均满足设计要求,该水泥浆体系经现场应用,取得良好的施工效果。     

Confinement Effects in Shallow-Water Jets

This paper documents measurements of the mean velocity field and turbulence statistics of an isothermal, round jet entering a shallow layer of water. The lower boundary of the jet was a solid wall and the upper boundary a free surface. The jet axis was midway between the solid wall and the free surface in all cases. Experiments were performed at a Reynolds number of 22,500 for water layer depths 15, 10, and 5?times the jet exit diameter (9?mm). Particle image velocimetry measurements were made on vertical and horizontal planes—both containing the axis of the jet. The measurements were taken from 10 to 80 jet diameters downstream. Results showed that, for the highly confined cases at downstream locations, the axial velocity was quite uniform over the depth, with a mild peak below the jet axis. In the horizontal plane, the velocity profiles were slightly narrower than the free jet profile, but in the vertical plane, they were wider. The mean vertical velocity profiles showed that entrainment was suppressed in the vertical direction. At the same time, the lateral velocity profiles indicate that fluid flows from the sides toward the jet centerline. For the shallow cases, the mean vertical velocity becomes negative over most of the depth at downstream locations, indicating that this inflow from the sides is directed downward toward the solid wall. The relative turbulence intensity results were suppressed in the axial and vertical directions and mildly enhanced in the lateral direction. As well, the Reynolds shear stress in the vertical plane was significantly reduced by the vertical confinement, while in the horizontal plane it was only slightly affected by the confinement.     

Dynamic Stiffness and Damping of a Shallow Foundation from Forced Vibration of a Field Test Structure

Foundation impedance ordinates are identified from forced vibration tests conducted on a large-scale model test structure in Garner Valley, California. The structure is a steel moment frame with removable cross-bracing, a reinforced concrete roof, and a nonembedded square slab resting on Holocene silty sands. Low-amplitude vibration is applied across the frequency range of 5–15?Hz with a uniaxial shaker mounted on the roof slab. We describe procedures for calculating frequency-dependent foundation stiffness and damping for horizontal translational and rotational vibration modes. We apply the procedures to test data obtained with the structure in its braced and unbraced configurations. Experimental stiffness ordinates exhibit negligible frequency dependence in translation but significant reductions with frequency in rotation. Damping increases strongly with frequency, is stronger in translation than in rocking, and demonstrates contributions from both radiation and hysteretic sources. The impedance ordinates are generally consistent with numerical models for a surface foundation on a half-space, providing that soil moduli are modestly increased from free-field values to account for structural weight, and hysteretic soil damping is considered.     

太湖西山岛山坞村落空间特征分析

传统村落作为农耕文明生活、聚居、繁衍的空间单元,具有重要的研究价值。通过对太湖西山历史风貌、遗存保留较好的村落进行实地调查,发现它们多位于山坞地形之中,形成山坞村落。采用田野调查法,结合遥感卫星影像与文献查阅,详细阐述了西山山坞村落的空间构成要素、典型地形剖面及村落平面空间特征。西山山坞村落空间构成要素可分为外部非生产性空间、外部生产性空间与村落内部空间3个层次;按地形特征可分为深坞村和浅坞村两大类;按平面空间特征可分为鱼骨型、扇形型及团网型三大类。旨在更加科学地解读西山山坞村落营建过程中对于自然环境的适应能力,今后可在传统村落的保护、更新与活化中发挥价值。     

Bearing capacity of surface circular footings on granular material under low gravity fields

Low gravity fields have been simulated through magnetic acceleration to conduct experimental study on bearing capacity of circular footings on a type of crushable planetary regolith simulant,which has comparable density and particle size distribution of lunar soil.The load-settlement responses of surface spread footings are obtained by investigating the relative density,footing size and gravity effects.Applying the hyperbolic asymptote method,normalised foundation stiffness and ultimate bearing capacity are obtained by curve fitting and predicted by power functions using multivariate nonlinear regression.The results show that the nonlinear gravity effect is not negligible,related to stress condition,soil dilatancy and mobilised friction angle.A cone penetration test(CPT)-based method for prediction of bearing capacity is proposed with correlations between ultimate bearing capacity of footings and shallow penetration stiffness of CPTs,avoiding the uncertainties of soil property estimations.Analyses of allowable bearing capacity and footing influence zone in consideration of footing size and gravity effects could therefore improve the design of shallow foundations on the Moon and Mars,and provide new understandings and potential implications to the bearing capacity of shallow foundations on crushable granular material in both terrestrial and extraterrestrial geotechnical engineering.