提高水利工程PERT进度计划精度方法探讨

分析了水利建设工程PERT进度计划存在的一些局限性和问题,讨论了PERT公式的选用和项目工序时间的估算方法,假设各项工作的持续时间服从β分布,提出PERT项目进度管理技术的改进措施,把完工概率作为工程进度动态控制指标。经实例验证,采用改进型的PRET可以将工期估算精度提高约40%,降低了人为主观估算工序时间偏差,提升了工程计划精度,使之更具有指导性。     

基于关键链理论的梯级泵站更新改造进度控制模型

针对传统的以关键路径法建立的项目进度控制模型在实际的施工过程中可能存在工期延误、资源冲突等问题,以盐环定扬黄工程梯级泵站系统更新改造项目为研究对象,在传统关键路径法的基础上,将约束理论的核心引入关键链理论中,在项目进度计划制定时将工序之间的资源约束、逻辑关系和工序持续时间提升到同等高度,通过工序之间的逻辑关系调整资源利用的优先级,避免不同工序在施工过程中的资源冲突;在缓冲区计算中以传统三点估计法为基础引入位置权数和弹性模量,合理消除工序持续时间中的多余安全时间,进而在不同位置设置汇入缓冲量和项目缓冲量,最后构建基于关键链技术的项目进度控制模型。结果表明,相比传统的由关键路径法建立的进度管理模型,以关键链技术为基础建立的项目进度管理模型在具体的施工过程中,工序之间资源调配更合理有序,工序持续时间更短,项目总工期由原来的460 d缩短到315 d,表明所建模型在梯级泵站更新改造进度控制中是有效且可行的。     

综合考虑多目标、多资源约束及接力势的关键链缓冲区计算方法研究

综合考虑工序的质量、成本、安全目标对工序持续时间的影响,项目资源受限程度及工序资源需求程度对缓冲区大小的影响,节点紧前平行工序之间接力势的影响,提出了一种综合考虑多目标、多资源约束及接力势影响因素的关键链缓冲区大小计算方法。结合案例及对比分析结果,采用该关键链缓冲区大小计算方法,有效地缩短了项目计划工期,降低了项目风险。     

模糊数学在施工网络计划中的应用

传统关键路线法(CPM)假定网络计划中每项活动具有确定的持续时间，而实际工程中工序持续时间具有不确定性，很难给出它的持续时间。计划评审技术(PERT)假定工期服从某种概率分布，这在数学上很难得到精确证明而且计算也相当复杂。工序工期的不确定性具有模糊特征，有必要借助模糊数学来处理。为此，提出了模糊网络计划方法，把各工序的持续时间定义为离散型变量，综合专家经验法和定额法估计来描述工序持续时间。模糊网络计划中λ-截集时间参数不同，其关键线路也不同。利用λ-截集时间参数的计算公式，可求得模糊网络各工序λ-截集时间参数及关键线路的模糊完成期。在实际工程中，关键线路及其相应工期受许多因素的影响而改变。模糊网络计划方法能对这种改变以及发生的可能性进行量化，为项目管理者提供决策分析依据。实例证明，模糊网络计划技术可行、实用，更接近工程实际，优于传统的PERT法。     

改进PERT模型在严寒地区抽水蓄能电站建设工期中的应用

中国抽水蓄能工程遍及南北,气候差异对于工程建设工期影响显著。针对一般计划评审技术(PERT)方法以随机分布来表达工序历时,而未考虑季节气候影响的问题。通过分析与时间背景相关的影响因素,引入时间背景修正系数,用经验估计和数据统计的方法,建立修正系数与影响因素关系的函数,得到考虑时间背景的工序工期修正系数,对工序历时分布参数进行修正,建立改进PERT模型分析工程关键线路和工期分布。案例分析表明,该方法对严寒地区抽蓄工程工期偏差具有良好的适应性。     

特大城门型水工隧洞快速衬砌施工技术

巴塘水电站导流洞建造断面为12m×14m(宽×高),属特大型水工隧洞。为实现2020年底导流目标,突破常规边顶拱混凝土施工方法,从混凝土施工全工序分析采取措施控制各工序持续时间。采取了底板"半幅与全幅相结合"工艺,边顶拱"施工工艺再造"和边顶拱结构受力复核与脱模试验等措施,施工中精细化管理,抓工序衔接,实现快速导流洞衬砌,单套穿行台车月衬砌边顶拱混凝土创下15仓记录。值得类似工程借鉴。     

岩溶隧道充填型隐伏溶洞涌突水持续时间特征试验研究

为研究岩溶隧道充填型隐伏溶洞涌突水持续时间特征,通过自主设计试验装置开展了不同介质上覆水头高度、介质沉积高度、介质类型和介质颗粒级配特征等条件的涌突水模拟试验,研究结果表明:(1)隐伏溶洞涌突水演化过程可分为四种模式,即渗-涌-突水(砂)模式、涌-突水(砂)模式、突水(砂)模式、渗-突水(砂)模式;(2)颗粒级配和介质种类对渗水(砂)阶段持续时间影响明显,细砂、中砂颗粒含量与持续时间的关系可用多项式函数表示,泥沙型介质持续时间大于砂砾型;(3)介质沉积高度和介质类型对涌水(砂)阶段持续时间影响明显,砂砾型和泥沙型介质沉积高度与涌水(砂)持续时间呈正相关,泥沙型介质持续时间小于砂砾型;(4)介质颗粒级配和沉积高度对突水(砂)阶段持续时间影响明显,细砂颗粒含量与持续时间的关系可用多项式函数表示,砂砾型介质沉积高度与持续时间呈先增大后减小的关系。研究结果对于隐伏溶洞涌突水灾害预警与防治措施具有一定的理论指导价值。     

广义优先关系下工序共用时差的计算与应用

工序共用时差和干扰时差能够体现项目中工序间相互影响的规律,是决定实际项目调度难易程度的重要因素。针对在带有广义优先关系(简称GPRs)的项目中尚缺乏对这两类时差的分析计算,从多视角研究GPRs下工序共用时差的量化及特性。首先,分析GPRs下工序共用时差的分布和效用特征,将其细分为工序前、后共用时差和总体共用时差,提出相应计算方法。其次,根据上述各子类型时差的特征、功能和规律,提出"半岛工序"和"孤岛工序"新概念。最后,将工序共用时差应用于GPRs下的资源均衡问题,实现了问题简化,提出提高求解效率的新思路。     

工程网络计划蒙特卡洛仿真研究

运用网络计划蒙特卡洛仿真(Monte Carlo Simulation，MCS)，获取工程工期的统计分布，从而计算特定计划工期的项目完工概率或完工风险，或是在指定完工概率或风险水平下制定合理的计划工期；计算工序关键概率(Activity Criticality Probability，ACP)及工序关键指标(Activity Cruciality Index，ACI)，掌握关键线路、关键工序分布情况，甄别高风险工序。此外，用VisualC 开发了一个网络计划仿真软件，并将其应用于一个工程实例分析。     

利用模糊集合论的工程网络分析

估计建筑项目的持续时间要求专家的经验。但专家的观点通常包含某种模糊性前人已研究了模糊集合论在持续时间模糊性量化上的应用。然而，这些研究却没有谈判编制一个完整计划的过程。本文基于模糊集合论提出了一个新的网络计划方法，该方法包括：１）模糊项目持续时间的表示；（２）计划参数的计算；（３）模糊的结果的分析，作者举了两个例了来说明该方法的工和蒙特匀模型进行了比较，结果表明用该方法得出的计划不仅适合解释在建筑     

极限水文干旱历时概率分析

本文用枚举法导出了独立同分布的随机变量序列的最大负游程长的概率分布函数，并将其用于相应序列的极限干旱历时（最大干旱持续时间）的概率分析，应用结果显示，本文介绍的独立同分布的随机变量序列的最大负游程长的概率分布函数，将其最大负游程长作为极限干旱历时，与相应结构的年径流序列在各种频率对应的流量截取后得到的水文干旱最大持续时间序列的经验频率拟合良好，因此可将这一概率分布函数称为极限干旱概率分布函数，将其     

Applying Bivariate Normal Distribution to Flood Frequency Analysis

Abstract

This article provides a procedure for using the bivariate normal distribution to describe the joint distributions of correlated flood peaks and volumes as well as correlated flood volumes and durations. The Box-Cox transformation (power-transformation) method is used to normalize original marginal distributions of flood peaks, volumes, and durations regardless of the original forms of these distributions. The power-transformation parameter is estimated using the maximum likelihood method. The joint cumulative distribution function, the conditional cumulative distribution function, and the associated return periods can be readily obtained based on the bivariate normal distribution. The method is tested and validated using observed flood data from the Batiscan River basin in the province of Quebec, Canada. The resulting theoretical distributions show a good fit to observed ones.     

Construction of a gamma-distribution probability paper for straightening discharge probability curves

Conclusion The Hazen probability paper presently being used for plotting discharge probability curves makes it possible to represent the probability curve as a straight line only in the case of a normal distribution of the series. In the case of a skew distribution of the series the probability curve has a bend. In such cases a special gamma-distribution probability paper should be used for skew distributions. The use of such a graph paper permits representing the probability curve as a straight line for any values of the coefficients of variation and skewness. Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 5, pp. 23–25, May, 1980.     

Derivation of Probabilistic Thresholds of Spatially Distributed Rainfall for Flood Forecasting

“Rainfall threshold” is considered as one of the evolving flood forecasting approaches. When the cumulative rainfall depth for a given initial soil moisture condition intersects the corresponding moisture curve, the peak discharge is expected to be equal or greater than the threshold discharge for flooding at the target site. Besides the total rainfall depth, spatial and temporal distribution of rainfall can influence the peak discharge and the time to peak. In the few past studies on the extraction of rainfall threshold curves for flood forecasting, the rainfall assumed to be uniform in space whereas the temporal distribution was subjected to certain assumptions. In the present study, the spatial distribution of rainfall was simulated with the Monte Carlo (MC) method and the mean Huff pattern for all rainfall durations was imposed for the temporal distribution. For each of the MC run, the random weight assigned to every sub-watershed follows the pdf of weights in historical rainfall events. The HEC–HMS model with two different infiltration methods namely SCS–CN and Green–Ampt and Muskingum river routing were adopted as the hydrologic model. After the calibration and validation of the model for Madarsoo watershed in Golestan province in Northeastern Iran, the MC simulations were performed for 1, 2, 6 and 12 h durations. The outputs from the SCS–CN method exhibit only a slight increase in threshold values with respect to duration and was not in the range of our expectations from watershed response, i.e. the rainfalls with greater durations should be greater in depth to produce a specific peak discharge. For the Green–Ampt infiltration method, the rainfall thresholds with 50% probability associated with the critical discharge under dry soil moisture condition were 44.5, 49.0, 64.2 and 94.6 mm for 1, 2, 6 and 12 h durations, respectively. Results for July 2001 flooding revealed that the cumulative rainfall intersected all 10%, 50% and 90% rainfall threshold curves but for July 2005 flooding the 10% curve was only intersected by the cumulative rainfall curve. The advantage of MC-derived rainfall threshold curves in real-time operations is that decision-makers have the flexibility to adopt a curve more consistent with flood observations in the region.     

多目标约束下给水管网水质传感器选址优化算法的研究

利用EPANET2模拟扩展周期非稳态水力水质条件下管网节点污染物浓度变化,根据各个节点被注入污染物后,在管网模拟结束时得到的选址目标值的大小来确定节点有可能作为污染物注入的节点,目标值越大,该节点被选择的可能性越大.另外,本文提出了基本粒子群算法与遗传算法交叉、变异算子相结合的整数编码的优化算法来求解水质传感器选址问题,并编制了相应的计算程序.文中结合算例,以经过归一化后的节点平均坐标作为衡量选址结果的指标,得到了不同污染物注入开始时刻、注入持续时问和质量注入速率条件下传感器选址节点平均坐标的累计分布函数图,为传感器的选址提供参考.     

南宁市不同历时降水结构的多时间尺度研究

为研究不同历时降水事件的结构及变化趋势,借助小波分析的时频多分辨功能,从降水历时角度出发,将1971—2012年南宁市国家级地面气象站逐小时降水观测数据分为1~3 h,4~6 h,7~10 h,10 h以上4个历时,分析其多尺度周期变化。结果表明:①1~3 h, 4~6 h, 7~10 h, 10 h以上降水次数时间尺度的主周期分别在28,27,29和11年左右,7 h以下降水次数周期变化明显大于7 h及以上。②4个历时降水量的主周期分别在28,26,29和12年左右,除7~10 h外,其他历时降水量周期变化都很明显,正负相位交替变化十分明显。③根据分析结果预测,在未来2年内,除4~6 h降水量外,其他历时的降水次数及量都将呈负相位趋势。分析不同历时降水结构的周期变化规律可为深入探索区域降水循环变异规律提供依据。     

A New Method for Joint Frequency Analysis of Modified Precipitation Anomaly Percentage and Streamflow Drought Index Based on the Conditional Density of Copula Functions

In this study, a new method was proposed to model the occurrence of related variables based on the conditional density of copula functions. The proposed method was adopted to investigate the dynamics of meteorological and hydrological droughts in the Zarinehroud basin, southeast of Lake Urmia, during the period 1994–2015. For this purpose, the modified precipitation anomaly percentage and streamflow drought indices were extracted. Finally, the joint frequency analysis of duration-duration and severity-severity characteristics of meteorological and hydrological droughts was analyzed. Analysis of 7 different copulas used to create the joint distribution in the Zarinehroud basin indicated that the Frank copula had the best performance in describing the relationship between the meteorological and hydrological drought severities and durations. By examining the results of the bivariate analysis of duration-duration of meteorological and hydrological droughts at different stations, the expected meteorological and hydrological drought durations were estimated in the years ahead. For example, at Chalkhmaz station, 4- to 7-month duration for the hydrological drought and 9- to 12-month duration for the meteorological drought is expected in the years ahead. The joint frequency analysis of drought characteristics allows to determine the meteorological and hydrological drought characteristics at a single station at the same time using joint probabilities. Also, the results indicated that by knowing the conditional density, the hydrological drought characteristics can be easily estimated for the given meteorological drought characteristics. This could provide users and researchers useful information about the probabilistic behavior of drought characteristics for optimal operation of surface water.

     

螺旋型埋管能源桩桩内温度场分布特征及其影响因素分析

针对能源桩桩内温度场分布特征开展了现场原位试验,实测获得了能源桩换热过程中的桩壁和桩心温度,以此为基础结合数值模拟分析了能源桩的桩内温度场分布特征及其影响因素。分析结果表明:能源桩桩内温度温升规律与地埋管进出口温度变化规律一致,桩内温度场主要受地埋管进出口温度控制;能源桩制热(冷)时,以地埋管为起点,桩内温度远离地埋管呈抛物线下降(上升);影响能源桩桩内温度场分布特征的主要因素为回填材料导热系数和桩径,导热系数越大,相同制热时间时的桩内温度越高,且桩心温度随导热系数的增加近似呈线性上升;桩径越大,相同制热时间时的桩内温度越低,桩内温度随桩径的增加近似呈等比例下降。该研究成果可为能源桩的推广应用提供参考。     

Uncertainties and trends in extreme rainfall series in Tuscany,Italy: Effects on urban drainage networks design

Sound basin management at urban or greater scale needs reliable design storm definition. A statistical analysis is carried out on extreme annual rainfall series for durations of 1, 3, 6 and 12 hours occurring at two gauges in Tuscany, Italy. Kendall's test is applied to the extremal series to detect a definite increasing (or decreasing) trend. A special form of an ARIMA model is also fitted to the series to quantify possible linear trends and their respective significance. Results show a clearly increasing trend at shortest duration at both gauges, no trend at longer ones. Time evolution of design storms for all durations and return periods up to 25 years is derived and analysed based on Gumbel distribution. Applications are presented concerning impacts of uncertainties for the design of urban drainage networks.     

On application of the Weibull distribution in hydrology

The Weibull distribution, commonly used in hydrology, was derived using the principle of maximum entropy. The derivation required two constraints to be determined from data and yielded, in turn, a unique procedure for estimation of the distribution parameters. This method of parameter estimation was either superior or at least comparable to the methods of moments (MOM) and maximum likelihood estimation (MLE) for the precipitation data used. This distribution was less than accurate in representing probability distributions of rainfall depths and durations.