Nutrient and sediment removal by stormwater biofilters: a large-scale design optimisation study

A large-scale column study was conducted in Melbourne, Australia, to test the performance of stormwater biofilters for the removal of sediment, nitrogen and phosphorus. The aim of the study was to provide guidance on the optimal design for reliable treatment performance. A variety of factors were tested, using 125 large columns: plant species, filter media, filter depth, filter area and pollutant inflow concentration. The results demonstrate that vegetation selection is critical to performance for nitrogen removal (e.g. Carex appressa and Melaleuca ericifolia performed significantly better than other tested species). Whilst phosphorus removal was consistently very high (typically around 85%), biofilter soil media with added organic matter reduced the phosphorus treatment effectiveness. Biofilters built according to observed 'optimal specifications' can reliably remove both nutrients (up to 70% for nitrogen and 85% for phosphorus) and suspended solids (consistently over 95%). The optimally designed biofilter is at least 2% of its catchment area and possesses a sandy loam filter media, planted with C. appressa or M. ericifolia. Further trials will be required to test a wider range of vegetation, and to examine performance over the longer term. Future work will also examine biofilter effectiveness for treatment of heavy metals and pathogens.     

Influence of intermittent wetting and drying conditions on heavy metal removal by stormwater biofilters

Biofiltration is a technology to treat urban stormwater runoff, which conveys pollutants, including heavy metals. However, the variability of metals removal performance in biofiltration systems is as yet unknown. A laboratory study has been conducted with vegetated biofilter mesocosms, partly fitted with a submerged zone at the bottom of the filter combined with a carbon source. The biofilters were dosed with stormwater according to three different dry/wet schemes, to investigate the effect of intermittent wetting and drying conditions on metal removal.Provided that the biofilters received regular stormwater input, metal removal exceeded 95%. The highest metal accumulation occurs in the top layer of the filter media. However, after antecedent drying before a storm event exceeding 3–4 weeks the filters performed significantly worse, although metal removal still remained relatively high. Introducing a submerged zone into the filter improved the performance significantly after extended dry periods. In particular, copper removal in filters equipped with a submerged zone was increased by around 12% (α = 0.05) both during wet and dry periods and for lead the negative effect of drying could completely be eliminated, with consistently low outflow concentrations even after long drying periods.     

楼板大开洞及穿层柱对结构抗震设计影响

建筑单体存在塔楼与裙房未设缝脱开,抗侧力构件收进宽度超限,楼板大开洞,穿层柱的抗震超限情况;通过楼板应力分析来查看楼板大开洞对结构影响;通过对穿层斜柱截面有限元分析对其进行抗震性能设计;通过Push-over静力弹塑性分析得出结构在大震下塑性铰发展顺序。     

Effect of clogging of stone column on drainage capacity during soil liquefaction

Stone columns act as vertical drains, and due to their high permeability, allow for the quick dissipation of earthquake induced excess pore water pressure. When water flows through a loose sandy soil, it washes away fine soil particles. The fine sand particles get detached when the hydrodynamic force applied on the soil particles breaks the inter particle bonds between soil grains. These detached soil particles are then migrated by the seepage water. Based on the concentration of the soil particles in the seepage water, these may be captured at the pore constriction of gravels during the flow of water through the stone column. Thus, the clogging of stone column initiates which reduces of the permeability of column. The rate of dissipation of pore water pressure during earthquake is affected due to the clogging of column. In this paper, a mathematical model is proposed to determine the rate of dissipation of pore water pressure of stone column-reinforced ground by considering the clogging effect of column. The result obtained from the proposed model is verified with the available in-situ experimental data. A parametric study is also performed to investigate the effect of different parameters of the proposed model on the clogging of stone column. It is observed that when the permeability ratio, compressibility ratio and area ratio decrease, the possibility of clogging increases. The peak value of the excess pore water pressure ratio can increase up to around 50% due to clogging.     

A study on biological clogging of nonwoven geotextiles under leachate flow

This paper presents results of long-term permittivity tests using leachate to evaluate biological clogging of nonwoven geotextiles. Three types of geotextiles with varying masses per unit area were used in the tests. The identification and quantification of microorganisms in the geotextile were carried out as well as microscopic investigations. The accuracies of semi-empirical models to evaluate the kinetics of bacteria growth and to correlate hydraulic properties and microbiological parameters were examined. Permittivity tests under increasing water heads were also performed on the geotextile samples already subjected to long-term leachate flow in order to evaluate the values of water heads required to wash the biofilms out of the geotextile pores. The results of the tests showed the marked reduction of geotextile permeability due to biological clogging and that the results of the predictions by semi-empirical methods were consistent with the biological mechanisms observed.     

大型换流站阀厅结构参数优化设计

针对阀厅结构在纵向地震作用下存在较明显的扭转效应,对阀厅结构进行结构优化设计,并对比分析在多遇地震作用下原结构模型与优化结构模型的地震响应。分析表明,采用轻质混凝土砌块砖减小结构自重,适当地加大剪力墙、构造柱和圈梁截面尺寸均可以改善阀厅结构纵向扭转效应,其中采用轻质混凝土砌块砖的方式控制结构纵向扭转效应最明显;适当增大构造柱和圈梁截面能有效地控制结构横向地震响应;结构抗侧力构件的参数变化对悬吊设备地震响应的影响不显著。     

金刚石钻头钻削石材参数对其表面温度影响研究

本文采用热压烧结金刚石钻头钻削花岗岩、大理石和砂岩.采用红外线测温仪在线测量金刚石钻头表面温度.实验结果表明金刚石钻头表面温度随主轴转速和进给速度增加而加大,同时表面温度随钻削时间增加而加大.钻削花岗岩时表面温度最高,钻削砂岩时表面温度最低.     

短柱的设计

介绍了短柱的概念,对短柱的破坏形态进行了分析,提出了易形成短柱的部位,深入地探讨了短柱的设计要点,以帮助设计人员搞好短柱设计,从而提高短柱的延性,改善短柱的变形能力,避免脆性破坏的发生。     

钢筋保护层设计对结构裂缝的影响研究

探讨了混凝土保护层的作用机理及保护层开裂的原因,并通过计算,分析了影响保护层最大裂缝宽度的因素,指出采用相对合理的保护层厚度能够在一定程度上控制和减小混凝土裂缝宽度。     

原路面当量模量对沥青路面大修设计的影响

应用GAMES程序分析了原路面当量模量取值不同时对沥青路面大修路面结构的影响,并研究了铣刨前路面弯沉值与铣刨后原路面当量模量之间的相关关系,以提高铣刨后原路面当量模量取值的合理性。     

Case study: the performance and design outline of a buffering stormwater drainage system for a low-lying area

Performance evaluation and safety assessment of a buffering stormwater drainage system (BSDS) for a low-lying area are discussed in this paper. Unlike a conventional pump drainage system, the BSDS, which drains stormwater runoff of a low-lying area to a nearby channel system through underground conduits with gravity, and then buffering peak flows with the storage capacity of a channel system, will discharge stormwater to rivers outside the low-lying area with pumps or flood gates if necessary. This kind of drainage system is considered to be environment friendly and economic both in terms of capital cost and operating & maintenance expenses. To investigate the design parameters and evaluate the performance and safety of BSDS, a hydraulic model coupling the conduit systems and a channel system was developed in this paper, and a case-study approach based on field investigation and simulation test was used. Moreover, the design requirements for safety of BSDS were drawn through a simulation test.     

溶洞因素对上部结构柱应力的影响

在岩溶地质条件下,考虑上部结构与地基基础的相互作用,通过三维整体建模考虑变形协调。利用ANSYS有限元软件计算分析某一算例,通过改变溶洞半径、埋深、形状及改变溶洞围岩的弹性模量、泊松比及厚度,得出溶洞因素对上部结构应力的影响变化规律。     

国外绿色屋顶对雨水径流水量水质影响的研究

介绍了绿色屋顶的起源及发展现状,分析了绿色屋顶对雨水径流中水量与水质的影响,指出在水量方面,绿色屋顶可有效减少雨水径流,但在水质方面,需加强对污染物的控制。     

基于粗糙集的大型公用建筑设计项目技术风险评价

根据建筑业设计规范和标准,构造大型公用建筑设计项目的技术风险指标体系,运用基于粗糙集和模糊数学理论,建立了大型公用建筑设计项目的技术风险模糊综合评价模型,通过算例说明,该模型是可行的,且评价结果符合实际情况。     

轴心受压柱的截面优化设计

引入双轴等强度的概念,并在规定腹板和翼缘宽厚比限值的时候,将构件的实际工作应力σ代替极限应力φfy,从而对GB50017-2003的翼缘与腹板的宽厚比限值公式进行修正,以使轴心受压柱的截面设计更为经济合理。     

大开间异形柱框架结构设计

针对国内外学者对异形柱框架结构的研究较多,对于大开间异形柱框架结构的研究却较少的现状,对大开间异形柱结构的主要受力缺陷进行了分析,并针对工程设计中存在的一些问题进行了探讨,提出了相应的设计建议以指导工程实践。     

斯里兰卡铁路柱桩设计

介绍了斯里兰卡和英国标准中,关于柱桩基础设计的相关内容,对其进行了总结和归纳,并分析了国内外柱桩设计的异同,以提高铁路柱桩设计效率和准确率。     

Uncertainty in urban stormwater quality modelling: The influence of likelihood measure formulation in the GLUE methodology

In the last years, the attention on integrated analysis of sewer networks, wastewater treatment plants and receiving waters has been growing. However, the common lack of data in the urban water-quality field and the incomplete knowledge regarding the interpretation of the main phenomena taking part in integrated urban water systems draw attention to the necessity of evaluating the reliability of model results. Uncertainty analysis can provide useful hints and information regarding the best model approach to be used by assessing its degrees of significance and reliability. Few studies deal with uncertainty assessment in the integrated urban-drainage field. In order to fill this gap, there has been a general trend towards transferring the knowledge and the methodologies from other fields. In this respect, the Generalised Likelihood Uncertainty Evaluation (GLUE) methodology, which is widely applied in the field of hydrology, can be a possible candidate for providing a solution to the above problem. However, the methodology relies on several user-defined hypotheses in the selection of a specific formulation of the likelihood measure. This paper presents a survey aimed at evaluating the influence of the likelihood measure formulation in the assessment of uncertainty in integrated urban-drainage modelling. To accomplish this objective, a home-made integrated urban-drainage model was applied to the Savena case study (Bologna, IT). In particular, the integrated urban-drainage model uncertainty was evaluated employing different likelihood measures. The results demonstrate that the subjective selection of the likelihood measure greatly affects the GLUE uncertainty analysis.     

析中国传统文化对家居设计的影响

中国传统文化对家居设计的影响表现在两个方面，一是视觉表现，如色彩表现，家具的选购和装饰画的选择上；二是心理影响上。