State of technology for renewal of sewer force mains

This paper presents the results of a review of the state of technology for renewal of force mains. Force mains are critical components of many sewer collection systems with significant environmental and cost consequences for failure. The review identified several needs, including the need for rational and common design approaches for rehabilitation systems, quality assurance/quality control procedures, and better practices for operation and maintenance. The difficulty in assessing the condition of sewer force mains, leaving many owners with questions about the integrity of their systems, and the limited amount of technologies available for renewing a deteriorated main, has limited the amount of renewal work in the past. Most of the renewal activity has involved complete replacement of the force main. As the nation's force mains age further, greater emphasis must be placed on finding cost-effective ways to renew these critical assets. Fortunately, new products and technologies are now emerging for condition assessment, as well as rehabilitation. Some newer methods developed for gravity sewers and water distribution systems are being adapted for use in force main rehabilitation but design and performance data gaps remain to be filled.     

Multiobjective optimisation algorithm for sewer network rehabilitation

Understanding of deterioration mechanisms in sewers helps asset managers in developing prediction models for estimating whether or not sewer collapse is likely. Effective utilisation of deterioration prediction models along with the development and use of life cycle maintenance cost analysis contribute to reducing operation and maintenance costs in sewer systems. This article presents a model for life-cycle maintenance planning of deteriorating sewer network as a multi-objective optimisation problem that treats the sewer network condition and service life as well as life-cycle maintenance cost (LCMC) as separate objective functions. The developed model utilises Markov chain model for the prediction of the deterioration of the network. A multi-objective genetic algorithm is used to automatically locate an appropriate maintenance scenario that exhibits an optimised tradeoff among conflicting objectives. Monte Carlo simulation is used to account for LCMC uncertainties. The optimisation algorithm provides an improved opportunity for asset managers to actively select near-optimum maintenance scenario that balances life-cycle maintenance cost, condition and service life of deteriorating sewer network. A case study is used to demonstrate the practical features of developed methodology.     

Decision support model for selection of rehabilitation methods of water mains

The deteriorating condition of water mains in Canada and US calls for rehabilitation strategies that accounts mainly for budget and level of service constraints. These water mains have received ‘D’ grade in the two countries. Decision support models can assist decision makers regarding when to rehabilitate and whether to repair, renovate or replace section(s) of water mains. The literature indicates that decision models should account for life cycle cost, uncertainty, long-term planning, targeted levels of service and budget constraints. The objectives of this paper are to: identify and group rehabilitation methods, present decision support model to rank and select most suitable rehabilitation method(s), and study the impact of rehabilitation methods on the functional and structural performance of water mains. The developed decision support model accounts for life cycle cost of each competing scenario along with the associated uncertainty. The model, unlike available models, can effectively account for vagueness, qualitative assessments and human judgment associated with input data. A case study of a water main network was analysed in order to demonstrate the use of the developed model and to illustrate its essential features. The results obtained indicate that the model can support the generation of well-informed decisions in a timely manner.     

Calibration and validation of a dynamic model for water quality in combined sewer retention tanks

As the integrated management of urban wastewater systems becomes more and more popular, the development of wastewater management subsystem models appears essential to improve the understanding of the pollutant dynamics and their interactions. In such a context, a review of the literature reveals a lack of efficient models describing the dynamics of the water quality stored in off-line retention tanks. A model has thus been proposed based on the fractionation of suspended solids into three classes according to the particle settling velocity distribution measured in the field using the ViCAs settling test. In this paper, a calibration methodology is developed and full-scale field data sets from three different events are used for 1) calibrating this new dynamic retention tank model (two data sets); and 2) validating that model on the last data set. The results show a good agreement between observed and simulated data both for the total suspended solids and the total chemical oxygen demand.     

滨海地区污水干管顶管沉井倾覆事故分析

对滨海软土地区顶管施工过程中发生的顶管工作沉井倾覆原因进行了分析,对比了各参数对提高沉井后背墙土体稳定性的影响强弱,提出增加沉井高度是有效的措施,并分析了内在的原因,对减少此类事故的发生有一定意义。     

Simulation-based life cycle cost modeling and maintenance plan for water mains

Life cycle cost (LCC) is an essential approach to decide on alternative rehabilitation strategies for infrastructure systems, such as water mains. The research presented in this article identifies several rehabilitation methods for water mains, which are classified into three main categories: repair, renovation and replacement. A simulation-based LCC (SLCC) model is developed to compare different rehabilitation scenarios/alternatives for various types of water mains (i.e. cast iron, ductile iron, concrete, polyvinyl chloride and asbestos cement). Results show that ‘open trench’ and ‘slip lining’ are the most appropriate methods for the ‘repair’ and ‘renovation’ categories, respectively. However, the most suitable method for the ‘replacement’ category is ‘pipe bursting’ for pipe diameters less than 750 mm (<30″) and ‘open cut’ for pipe diameters greater than 750 mm (>30″). A rehabilitation plan is developed based on the SLCC results. This plan recommends repairing pipes using ‘open trench’ until the breakage rate reaches 0.5 breaks/km/year, then, replace the pipe beyond this threshold. Based on the designed SLCC model, web-based software is developed to determine the optimal rehabilitation scenarios. The developed model and software help academics and practitioners (e.g. municipal engineers) to predict the suitable new installation and/or rehabilitation programs as well as their corresponding costs.     

Data acquisition and analysis for water main rehabilitation techniques

The ability to regularly deliver safe drinking water is a constant challenge to municipalities worldwide. In Canada, the replacement/rehabilitation cost of water mains is estimated to be $28 billion (1997–2012). Therefore, selecting cost-effective repair and/or rehabilitation scenario(s) is essential to optimise the quality of existing water mains and minimise unnecessary rehabilitation costs. The research presented in this paper identifies several rehabilitation methods for water mains, which are classified into three main categories: (1) repair (i.e. open trench, sleeves); (2) renovation (i.e. slip lining, cement mortar lining, epoxy lining, cured in place pipe (CIPP)); and (3) replacement (i.e. pipe bursting, micro-tunnelling, horizontal directional drilling, auger boring, open cut). Due to complexity, scarcity, and enormity of data required to perform life cycle cost (LCC) and select the cost-effective scenario(s), the research presented focuses on LCC data acquisition and analysis. Data were collected from contractors and municipalities in Canada. Rehabilitation decision trees were developed as a preparation step for future LCC implementation. Breakage rate analysis was successfully developed to predict the intervals of various rehabilitation alternatives. The research presented is relevant to researchers and practitioners (municipal engineers, consultants, and contractors) to prioritise pipe inspection and rehabilitation planning for existing water mains.     

建筑工程质量安全及环境质量管理控制初探

运用环境科学的基本观点 ,全面系统地分析了目前城市建筑环境与建筑工程质量安全管理和评价信息系统的关系以及存在的问题。提出应建立一个较为完整的“广义建筑工程质量安全”评价模型。     

历史街区保护改造与旧城更新的区别和联系

指出了在历史街区保护改造和旧城更新通常理解中的误区,介绍了历史街区和旧城的概念,从适用范围和具体措施两个方面阐述了它们的区别与联系,以制定完善的城市保护与更新规划,实现城市的可持续发展。     

清水混凝土质量标准和质量控制措施

介绍了清水混凝土的质量标准，从模板、钢筋工程、混凝土工程等方面探讨了清水混凝土的施工技术，提出了对清水混凝土的缺陷进行处理的措施，促进其在我国的健康发展。     

Hydrological assessment of flow dynamic changes by storm sewer overflows and combined sewer overflows on an event-scale in an urban river

In addition to assessing the impacts of water quality changes in urban rivers caused by storm water sewer overflows (SWO) and combined sewer overflows (CSO), the extent to which flow dynamics are changed by these structures must be understood in order to define hydrological assessment criteria to guide sustainable water management strategies as required by the European Community (EC) Water Framework Directive. In this study, the quantitative impacts of SWOs and CSOs on the flow dynamics of an urban river and their variability are investigated. For four single runoff events, hydrological measurements were accomplished in the River Dreisam, upstream and downstream of the city of Freiburg, in southwest Germany. As the catchment is widely free of urban areas upstream of the city, comparison with downstream locations allowed quantification of Freiburg's effects on the changes in the hydrograph on an event scale. The proposed hydrological parameter—flow acceleration, peak discharge, and discharge dosage—were shown to be appropriate to assess the impacts of SWOs and CSOs on flood hydrographs in urban rivers.     

Impact of an intense combined sewer overflow event on the microbiological water quality of the Seine River

For a better understanding of the short and mid-term impacts of a combined sewer overflow (CSO) on the microbiological quality of the receiving river, we studied the composition of a CSO discharge and monitored during several hours the changes in the concentration of fecal indicator bacteria (FIB) in the impacted river water mass. The CSO occurred at the Clichy outfall (Paris agglomeration, France) in summer 2008 as a result of the most intense rainfall of the year. In 6h, 578, 705 m³ of sewage and 124 t of suspended matter (SM) were discharged into the Seine River. The CSO contained 1.5 × 10⁶E. coli and 4.0 × 10⁵ intestinal enterococci per 100 mL on average, and 77% of the E. coli were attached to SM. It was estimated that 89% of the CSO discharge was contributed by surface water runoff, and that resuspension of sewer sediment contributed to ∼75% of the SM, 10-70% of the E. coli and 40-80% of the intestinal enterococci. Directly downstream from the CSO outfall, FIB concentrations in the impacted water mass of the Seine River (2.9 × 10⁵E. coli and 7.6 × 10⁴ intestinal enterococci per 100 mL) exceeded by two orders of magnitude the usual dry weather concentrations. After 13-14 h of transit, these concentrations had decreased by 66% for E. coli and 79% for intestinal enterococci. This decline was well accounted for by our estimations of dilution, decay resulting from mortality or loss of culturability and sedimentation of the attached fraction of FIB.     

灵石县某煤矿工程中的水土保持生态修复设计

根据煤矿建设及开采过程中水土流失、生态破坏的特征,对水土保持的目标及水土流失进行了预测分析,提出了相应的水土保持及生态修复方案,使煤矿矿区水土流失、生态环境得到有效改善,从而优化矿区整体生态环境。     

Modelling of organic matter degradation in constructed wetlands for treatment of combined sewer overflow

Subsurface vertical flow constructed wetlands (CWs) have been found to be a useful system to treat combined sewer overflow (CSO). The study presented uses numerical simulation to increase the understanding of the fundamental processes of COD degradation in CWs for CSO treatment. The multi-component reactive transport module CW2D was used for the simulation study. The simulation results showed that the measured behaviour of the system can only be modelled when COD adsorption is considered as additional process. A new parameter set for CW2D for modelling CSO treatment is presented. A range of values for COD adsorption parameters, COD fractionation and bacteria concentrations were estimated by an identifiability analysis. For the simulation a step wise approach was developed. On the one hand a lysimeter study was used for calibration and validation, and on the other hand field and lab-scale experiments were used for validation. Single-event simulations as well as long-term simulations were carried out. For the single-event simulations (lysimeter and field studies) a good match between measured and simulated data could be achieved. However, the long-term simulations showed that there is a need for further investigations mainly due to the uncertainties during long dry periods between the loadings.     

Computational fluid dynamics based assessment of discharge-water depth relationships for combined sewer overflows

This article describes a general method to assess discharge-water depth relationships for combined sewer overflow (CSO) chambers. This method is particularly suitable for: complex geometries, unavailable univoc relationship between upstream and downstream flow and complex downstream hydraulic conditions. The methodology presented in this article is based on computational fluid dynamics. Its aim is to propose a relationship between the water depths in the CSO chamber and the overflow discharge. This study focuses on the evaluation and integration of the uncertainties in the determination of the most suitable depth-overflow relationship. Uncertainties related to numerical model, boundary conditions and water depth have been taken into account in order to elaborate water depth-overflow rate relationship. This approach is illustrated through the example of the ‘Milan’ CSO of Mulhouse city, France.     

燃气管道非开挖修复更新技术特点

研究了国内外非开挖管道修复技术发展状况,对目前我国燃气管道主要应用的非开挖修复更新技术进行了介绍,分析了各工艺的特点与使用范围。     

清水混凝土质量控制施工技术

针对高层建筑清水混凝土施工中经常会出现表面平整度差、阴阳角不方正、垂直度差、上下墙错位等质量问题,提出了质量控制技术措施,施工实践中达到了清水混凝土要求。     

Constrained Ant Colony Optimisation Algorithm for the layout and size optimisation of sanitary sewer networks

The incremental solution building capability of Ant Colony Optimisation Algorithm (ACOA) is used in this paper for the efficient layout and pipe size optimisation of sanitary sewer network. Layout and pipe size optimisation of sanitary sewer networks requires optimal determination of pipe locations, pipe diameters and pipe slopes leading to a highly constrained mixed-integer nonlinear programming (MINLP) problem presenting a challenge even to the modern heuristic search methods. A constrained version of ACOA equipped with a Tree Growing Algorithm (TGA) is proposed in this paper for the simultaneous layout and pipe size determination of sewer networks. The method is based on the assumption that a base layout including all possible links of the network is available. The TGA algorithm is used in an incremental manner to construct feasible tree-like layouts out of the base layout, while the constrained ACOA is used to optimally determine the cover depths of the constructed layout. Proposed formulation is used to solve three hypothetical test examples of different scales and the results are presented and compared with those produced by a conventional application of ACOA in which an ad-hoc engineering concept is used for layout determination. The results indicate the effectiveness and efficiency of the proposed method to optimally solve the problem of layout and size determination of sewer networks.     

管道非开挖修复技术的分类和设计

非开挖修复技术在地下管道的维护管理工作以及城市的排堵保畅工作中得到了越来越多的应用。为此系统介绍了地下管道非开挖技术的分类、修复后管道的结构分类以及CIPP内衬制管的构造设计和性能指标。     

基于城市给排水管道非开挖施工技术的探讨

介绍了非开挖施工技术的含义及应用范围,归纳了非开挖施工方法的主要方法及设备,探讨了非开挖技术的特点,对杭州市非开挖施工技术的应用进行了分析,得出了非开挖技术应用前景极为广阔的结论。