盾构隧道下穿立交桩基托换方案设计

随着城市轨道交通的快速发展,地铁隧道下穿地下空间所遇到的问题愈加频繁,需要根据城市实际情况确定设计与施工方案。以郑州市轨道交通盾构隧道穿越立交桥进行桩基托换为研究对象,结合广州、深圳和香港地区桩基托换工程经验和现有技术水平,详述了盾构隧道穿越桥梁进行桩基托换的设计难点和重点。本方案具有技术成熟、安全性高、对环境影响小、不影响交通等优点,对在复杂环境下进行桩基托换的施工和设计具有重要的参考价值和良好的社会与经济效益。     

大跨隧道穿越高层建筑物桩基托换设计及优化

目前,在国内地下工程建设中,桩基托换已经得到一定范围的推广应用,但大部分托换工程均因地铁施工引起,地铁隧道断面较小(多为盾构隧道,直径6m左右),托换梁跨度小(约10m左右),容易施工,托换工程理论上可行,但是对于市政道路交通隧道工程,由于其断面跨度大,施工工艺目前尚不成熟,大跨度梁式托换工程仍需要深入研究。本文以广州某市政公路隧道下穿9层的Z大厦为例,对桩基托换进行了初步设计、计算及优化,可供相关工程或研究参考。     

谈百布区间鸿名电器厂桩基托换顶升工程

以深圳地铁5号线百布区间鸿名电器厂桩基托换工程为例,归纳了工程特点、重点、难点以及关键点,详细阐述了桩基托换顶升施工顺序,并介绍了桩基托换过程中的顶升施工方案,以积累相关经验,顺利完成此类任务。     

Investigation into capital costs of HVAC systems

The initial capital outlay is one of the largest expenses of any HVAC system. Estimating these costs accurately is crucial to any HVAC economic analysis. In this article, initial cost models are investigated.A literature study reveals different methods for estimating initial costs. None of these are suitable for use during the conceptual design stage. They are either too simplified or require too detailed inputs. The use of “Pareto's Principle” to develop a suitable model is investigated in this paper.“Pareto's Principle” can be formulated to state that 20% of the equipment makes up 80% of the cost. This principle is tested by analysing some tender estimates. Although it appears to hold true, it is also evident that items like piping and ducting contribute significantly to installation costs. Accurate estimates can thus only be obtained by pricing each sub-system separately.Models are proposed for each subsystem of a typical HVAC system. All the proposed models are suitable for integration with QUICKcontrol and are applicable to a wide range of different HVAC systems.Estimating the costs of both the major capital equipment as well as the smaller sub-systems, is relatively simple. Air and water distribution systems are more problematic due to the number of variables. Without a fairly detailed design and costing model, no accurate cost predictions can be made.     

穿越沈阳站既有站房地下通道施工技术

沈阳站既有东站房下穿地下通道,工程采用MIDAS有限元分析软件建立托换体系三维实体模型,模拟分析既有桩基上部柱荷载传递至托换体系的变形,并对因通道开挖造成基坑底部土体应力卸载从而引起地铁结构整体产生向上位移进行了模拟分析。施工中通过设置托换体系,即设置托换桩及托换梁、板结构,分层盖挖土方和分段施工通道主体结构等施工措施,确保了下部地铁运营安全,为类似工程施工提供借鉴。     

Time–cost optimization: using GA and fuzzy sets theory for uncertainties in cost

Uncertainties should be considered in any time–cost trade‐off problems when minimizing project cost and duration, which leads to the so‐called stochastic time–cost trade‐off problem. A new approach to investigate stochastic time–cost trade‐off problems employing fuzzy logic theory is presented. The proposed approach fully embeds the fuzzy structure of the uncertainties in total direct cost into the model. An appropriate GA is used to develop a solution to the multi‐objective fuzzy time cost model. The accepted risk level of the project manager is defined through α cut approach for which a separate Pareto front with set of non‐dominated solutions has been developed. To compare the alternative set of options for any assumed project duration, associated fuzzy costs for different values of α cut are ranked employing two appropriate approaches for fuzzy costs comparison. The proposed models are applied to solve two benchmark test problems. It is shown that the models facilitate the decision‐making process by selecting specified risk levels and employing the associated Pareto front.     

福州地铁洗马桥桩基托换方案研究

结合福州地铁洗马桥工程实际情况,探讨了该桥桩基托换方案,通过对比分析不同方案的成本、技术难度,确定了适合本工程的托换及除桩技术方案,并提出相应的辅助施工技术,为顺利施工提供了指导,并达到减小社会影响、缩短施工周期和降低工程造价的目的。     

Planning level tunnel cost estimation based on statistical analysis of historical data

Estimating the construction cost of a tunnel with certain diameter and length during the planning stage of a project is essential and a “must do” to justify the project, but it is a very difficult task. Numerous variables influence the cost of tunnel construction and limited information is available at early stages of design when the possible use of tunnels is being studied. Therefore, there is limited number of models at engineers’ disposal for development of a proper cost estimate in tunneling projects. The focus of this study was to offer a model for estimation of the construction cost of tunnels for various applications in the preliminary stage of a project. The work is based on study of nearly 270 projects and statistical analysis of the recoded construction costs, tunnel size, ground conditions, and tunnel applications. Several cost estimation models are introduced for various tunnel types including waste water, water, and transportation tunnels in soft ground and rock. The model uses commonly available cost indices (CCI and BCI) to adjust the estimated costs for the time and location of the project. The proposed cost models presented in this study can included in a simple program to help users make more accurate and quick cost estimates for their future projects. The models do not deal with construction risk which is an essential part of the study of various methods and should be done through developing a risk registry with related cost of each case before final selection, design, and cost estimation of any tunneling project.     

桩式托换技术在砌体结构基础加固中的应用

当前广泛应用的各种砌体结构基础加固技术中,桩式托换技术具有直接将基底压力传至深层坚硬地基的优点,沉降控制效果好,但其技术要求也最高。详细讨论了桩式托换中的桩型选择、托换结构与原结构共同工作、总体设计思路、预应力夹墙梁设计、梁式承台设计施工等问题。工程实例表明:经过精心设计与合理施工,桩式托换是一项行之有效的砌体结构基础加固技术。     

桩基托换技术在广州地铁三号线工程中的应用

结合广州市轨道交通三号线沥-厦区间桩基托换工程实例,介绍了托换体系的设计、施工步骤和监测。     

多锚点锚拉桩在广东深圳地区多层滑床滑坡防治工程中的应用

滑坡是一种常见的地质灾害,其中锚拉桩是滑坡防护的有效措施之一。在锚拉桩治理滑坡的研究中,多将滑床当作均质体进行计算,对于多层滑床滑坡的锚拉桩加固研究较少。鉴于此,本文在传统计算方法的基础上,考虑非均质滑床这一特点,对锚拉桩加固滑坡的计算模型进行改进,以深圳市某滑坡治理工程为例,根据滑坡特点进行了多锚点锚拉桩加固方案设计,并布设了深部测斜、锚力和钢筋计等监测工程,监测桩身位移及锚索应力,对比分析监测值与理论值,验证改进模型的适用性。结果表明:改进模型相对于传统模型与监测结果更吻合,准确性更高,改进模型所得到的桩顶位移及滑面处剪力小于传统算法,分别减少了28.61%和5.7%,最大弯矩值减小了20.9%。经过3年多进一步验证了多锚点锚拉桩加固滑坡工程的有效性,本文的改进模型可为工程降低一定的成本,并对多层滑床滑坡的加固工程设计提供了一定的借鉴和参考。     

Estimate at Completion for construction projects using Evolutionary Support Vector Machine Inference Model

Construction projects are influenced by a range of factors that impact upon final project cost. Estimate at Completion (EAC) is an important approach used to estimate final project cost, which takes into consideration probable project performance and risks. EAC helps project managers identify potential but still unknown problems and adopt response strategies. This study constructed an evolutionary EAC model to generate project cost estimates that proved significantly more reliable than estimates achievable using currently prevailing formulae. The developed learning model fused two artificial intelligence approaches, namely the fast messy genetic algorithm (fmGA) and Support Vector Machine (SVM), to create an Evolutionary Support Vector Machine Inference Model (ESIM). The ESIM was then applied to estimate final project costs for historical cases. Finally, using the EAC estimate, project cost influence indices, and project cost diagrams, the discrepancy between estimate and practical values was examined to determine potential problems in order to help project managers better control project costs. The learning results were validated in real applications that showed good performance for training models. Providing project managers reliable EAC trend estimates is helpful for their effective control of project costs and taking appropriate peremptory measures to handle potential problems.     

明挖隧道下穿既有桥梁桩基托换施工技术

随着全国各大城市大规模的地铁建设,桥梁桩基托换技术将越来越多的应用于地铁工程建设。本文重点对某地铁线路某区间的桩基托换技术进行了分析介绍,希望能为今后类似工程提供参考。     

锚杆静压桩桩基托换机理探讨

通过对桩基托换技术和锚杆静压桩工作机理的分析,详细阐述了锚杆静压桩桩基托换的工作机理;提出了锚杆静压桩桩体回弹估算方法,剖析了上海地铁某区间隧道穿越高层建筑拟采用的锚杆静压桩托换方案。     

花城大道地铁车站施工设计优化

本文针对广州市珠江新城花城大道地铁车站的若干设计方案进行比选。通过采用理正软件对所有的钻孔资料进行基坑开挖计算对比分析 ,在考虑基坑周边管线安全的前提下 ,否定了桩锚支护方案 ,提出了疏桩与密桩结合的支护方案 ,确保基坑安全 ,降低了工程造价 ,创造了较好的经济效益与社会效益。     

基于造价控制的最优承发包模式选择

目前,国内外工程项目的承发包模式众多,在对国内外各种承发包模式综合研究的基础上,将其分成了包括传统的 DBB 模式、工程总承包模式和项目管理承发包模式三大类别,分析了各种承发包模式的特点和适用范围,为了更好地实现项目的既定目标,针对不同的项目承发包模式,提出了不同的造价控制方法。并具体分析了工程项目各种承发包模式的特点及与项目造价控制的关系,试图在项目质量、工期和造价目标相互平衡的条件下,寻求最有利于投资者进行造价控制的最优承发包模式。     

An Integral Approach to Design Strategies and Construction Systems R. M. Schindler's "Schindler Shelters"

R. M. Schindler's Schindler Shelters designs for low-cost, mass-producible housing are significant and innovative. This project illustrates Schindler's longtime interest in flexible design strategies and integrated construction systems underpinning his Space Architecture. In the Shelter project, systematic design strategies are used to achieve flexible layouts for mass-produced dwellings. The panel-post construction system is developed as a means of achieving this goal; the system uses unit components and allows for interchangeable assembly of its parts. This study reconstructs the archival material related to the project by analyzing housing layout variations to reveal the underlying logic of Schindler's scheme and by fabricating scaled models to simulate the construction process.     

Data modelling and the application of a neural network approach to the prediction of total construction costs

Neural network cost models have been developed using data collected from nearly 300 building projects. Data were collected from predominantly primary sources using real-life data contained in project files, with some data obtained from the Building Cost Information Service, supplemented with further information, and some from a questionnaire distributed nationwide. The data collected included final account sums and, so that the model could evaluate the total cost to the client, clients' external and internal costs, in addition to construction costs. Models based on linear regression techniques have been used as a benchmark for evaluation of the neural network models. The results showed that the major benefit of the neural network approach was the ability of neural networks to model the nonlinearity in the data. The ‘best’ model obtained so far gives a mean absolute percentage error (MAPE) of 16.6%, which includes a percentage (unknown) for client changes. This compares favourably with traditional estimating where values of MAPE between 20.8% and 27.9% have been reported. However, it is anticipated that further analyses will result in the development of even more reliable models.     

Effect of Performance Model Accuracy on Optimal Pavement Design

In the first part of this paper, an analysis of the data collected during the American Association of State Highway Officials (AASHO) road test, based on probabilistic duration modeling techniques, is presented. Duration techniques enable the stochastic nature of pavement failure time to be evaluated as well as censored data to be incorporated in the statistical estimation of the model parameters. The second part of this paper presents the use of economic optimization principles for determining the optimal design of flexible pavements. We study the effect of deterioration model accuracy on optimal design and lifecycle costs by comparing three models. The first is a simple regression model developed by the AASHO, which forms the basis of design standards in use today. The second is a regression model that was developed with the same AASHO data set, but that includes a correction for data censoring. The third model is the probabilistic model developed in the first part of this paper. The results show that the AASHO model, when used as an input to lifecycle cost minimization, produces a pavement structural number that is lower than that produced by using the other two deterioration models. This results in shorter pavement lives and higher costs due to more frequent resurfacing. The savings in lifecycle cost accrued by using optimal structural number are shown to be quite significant, offering a sound basis for revising current design practices.     

Deterministic models for assessing productivity and cost of bored piles

The assessment process of productivity and cost of bored pile construction is dictated by unseen subsurface obstacles, lack of contractor experience and site planning. These problems complicate the estimator's role in evaluating pile equipment productivity and cost. Current research discusses the assessment of piling process productivity and cost using the deterministic technique. Data are collected through questionnaires, site interviews and telephone calls to experts in various construction companies. Many variables have been considered in the piling construction process, such as pile size, depth, pouring method, soil type and construction method. Five deterministic models have been designated to assess productivity, cycle time and cost. The developed models are validated whereas 79% of the outputs have been predicted with more than 75% accuracy. Consequently, three sets of charts have been developed to provide the decision‐maker with a solid planning, scheduling and control tool for piling projects. If a pile has 60′ depth with φ‐18 (18″ diameter pile) in clay soil using a 5′ auger height, the cycle time is estimated as 56 and 65.5 minutes; however, productivity is 6 and 5 holes/day for dry and wet methods, respectively.