大跨度软弱围岩公路隧道施工过程仿真

横龙山隧道喇叭口段地质条件差，隧道跨度大，给施工带来很大的难度，本文应用有限元方法对大跨度隧道的完整的开挖过程进行了动态模拟研究，模拟开挖采用的双侧壁导坑法的施工全过程，对隧道施工引起的围岩和地表沉降进行了分析，根据仿真计算的结果提出了大跨度隧道施工中应该注意的问题及相应的解决措施。     

山区高速公路隧道群和长大隧道沥青路面施工技术

近几年随着高速公路由平原微丘区向山岭重丘区发展,高速公路上的桥梁和隧道里程占得比例越来越大,如何在桥梁群、隧道群、长大隧道中施工好沥青路面,对施工组织管理技术提出了很高要求,下面作者结合在诸永高速路面施工中探索和总结的经验做一介绍.     

浅谈大跨度超浅埋隧道下穿高速公路施工技术

为适应社会发展的要求,交通体系日益复杂化,隧道下穿问题日益增多,隧道下穿高速公路的问题非常常见,对基坑方案设计和施工技术要求越来越高,本文就大跨度超浅埋隧道下穿高速公路施工技术进行研究.     

隧道浅埋暗挖法开挖方案的优化分析

采用岩土工程通用软件FLAC3D对隧道全断面法、两台阶法、三台阶法和CRD法等典型的浅埋暗挖施工方法进行二维数值模拟,分析了在不同开挖方法下施工对隧道围岩稳定的影响。文中选取了某一实际隧道工程为研究对象,通过对不同开挖方法的施工模拟计算,对比分析了各种方法的隧道围岩位移、应力分布以及塑性区大小的规律与特点。     

浅谈黄土隧道道防排水施工

地下水渗漏对黄土隧道的围岩压力和物理力学性能变化、隧道正常安全运营及施工安全带来很大的影响。尤其是竣工后渗漏水,对工程的安全运营带来巨大的隐患。针对吴子高速公路黄土隧道的实际施工情况,对黄土隧道防排水施工的技术作了总结,并提出相应的质量管理措施,同时提高了防排水施工在黄土地区隧道建设重要性认识。     

某隧道掘进控制爆破

控制爆破广泛应用于隧道的开挖和掘进,是确保隧道掘进质量和速度的重要方法。介绍了某取水隧道掘进爆破开挖过程,通过合理的爆破参数和严密的施工组织,光面爆破效果理想,提高了隧道掘进的爆破效率,最终提高了掘进速度。     

隧道施工对邻近桩体轴向变形和受力的影响

运用Midas-GTS有限元软件进行三维数值分析,研究地表在隧道开挖作用下位移的变化规律,分析隧道施工对桩体位移及受力的影响.     

隧道下穿既有结构物引起的地表沉降控制标准研究

解决好隧道下穿既有结构物引起的地表沉降问题,对城市地下交通和高速铁路的建设具有重要的意义.在调研国内大量隧道下穿开挖引起的地表沉降控制标准和方法的基础上,根据隧道下穿公路、铁路、隧道和建筑物时引起的地表沉降的不同特点,结合隧道的施工、开挖面积、埋深和工程地质条件等因素,对隧道下穿不同的结构物提出不同的控制沉降措施和建议沉降标准.作者认为,目前的隧道下穿引起的地表最大沉降控制标准是不合理的,沉降控制标准应综合考虑既有结构物的特点、地质条件和施工特点等因素.     

热力隧道在非降水施工中的力学特性监测

城市热力供水工程逐渐由近地层明挖向深地层暗挖转移,通过对北京市两个典型地质热力隧道的现场原位的监测,分析浅埋暗挖热力隧道在非降水施工过程中对于砂卵石地质和粉质黏土地质条件下的初支结构内力、围岩性状、水文特征的变化及对地层的影响.试验监测结果表明,隧道围岩的土压力分布不同,水压力分布相同,初衬钢筋内力分布不同,砂卵石地质务件下的隧道初衬受力情况较好,隧道开挖对地表沉降影响较小,研究结果可在开挖城市供热、供水及供气等小断面隧道时参考.     

温拌沥青在隧道路面工程中的应用

以京包高速公路德胜口隧道摊铺温拌沥青混合料路面施工为基础,根据隧道中热量散失少温度上升快的特点,按施工时达到的温度高低不同,划分为2种区域施工.对温拌沥青混合料在这2种区域内的施工工艺及如何改善隧道施工环境做了研究.     

Estimating Future Highway Construction Costs

The objective of this research was to develop a model that estimates future highway construction costs in Louisiana. The model describes overall highway construction cost in terms of a highway construction cost index. The index is a composite measure of the cost of construction labor, materials, and equipment; the characteristics of contracts; and the environment in which contracts are let. Future construction costs are described in terms of predicted index values based on forecasts of the price of construction labor, materials, and equipment and the expected contract characteristics and contract environments. The contract characteristics and contract environments that are under the control of highway agency officials, can be manipulated to reflect future cost-cutting policies. Application of the model in forecasting to highway construction costs in Louisiana shows that the model closely replicates past construction costs for the period 1984–1997. When applied to forecasting future highway construction costs, the model predicts that highway construction costs in Louisiana will double between 1998 and 2015. Applying cost-cutting policies and assuming input costs are 20% less than anticipated, the model estimates highway construction costs will increase by 75% between 1998 and 2015.     

Research on Cable Anchorage Systems for Self-Anchored Suspension Bridges with Steel Box Girders

A new type of steel-concrete composite cable anchorage system is conceived and investigated preliminarily for self-anchored suspension bridges with steel box girders to optimize the mechanical behavior of the conventional cable anchorage systems. Model tests and 3D elaborate finite-element analysis (FEA) of the pure steel and steel-concrete composite cable anchorage systems are carried out for the Qingdao Bay Bridge Project, which is under construction in China. For the pure steel anchorage system, a complex stress distribution with obvious stress concentration is observed in the test. The FEA results of the stress distribution correlate well with the experimental measurements. The pure steel anchorage system adopted in the final design of the Qingdao Bay Bridge Project is reliable with a sufficient safety margin. In the contrast test of the composite anchorage system, owing to the composite effect between the steel and concrete, the stress level is reduced significantly and the stress distribution becomes more uniform in comparison with the pure steel anchorage system. The measured stress reduction rate of the composite anchorage averages approximately 40%, which is slightly smaller than the FEA results, and indicates the partial composite effect between the steel and concrete. The proposed composite anchorage system can effectively reduce the thickness and consumption of the steel plates, improve the mechanical behavior of the anchorage system, and simplify the fabrication and construction procedures.     

Neural Network Modeling of Highway Construction Costs

The objective of this research was to develop a procedure that estimates the escalation of highway construction costs over time. An artificial neural network model was developed which relates overall highway construction costs, described in terms of a highway construction cost index, to the cost of construction material, labor, and equipment, the characteristics of the contract and the contracting environment prevailing at the time the contract was let. Results demonstrate that the model is able to replicate past highway construction cost trends in Louisiana with reasonable accuracy. Future construction input costs are estimated from commercially available forecasts of indicator variables closely associated with the price of construction labor, construction equipment, and a representative set of highway construction materials. Future contract characteristics and the contracting environment that is likely to exist in the future are estimated from past trends or stipulated to be consistent with policy decisions in the future. The predictions produced by the model estimate that highway construction costs in Louisiana will double between 1998 and 2015.     

Impact of Rainfall on the Productivity of Highway Construction

Heavy rainfall often leads to complete suspension of highway construction due to saturated and unworkable soil conditions. Therefore, quantifying the impact of rainfall on the productivity of highway construction is essential in preparing realistic schedules and cost estimates for the preconstruction stage and in analyzing weather-related claims for the postconstruction stage. This paper presents a decision support system for quantifying the impact of rainfall on productivity and duration of common highway construction operations, namely: earthmoving, construction of base courses, construction of drainage layers, and paving operations. The system incorporates a knowledgebase and a database. The knowledgebase includes if∕then type rules, acquired from experts in highway construction operations, and the database contains hourly records of weather parameters from the closest weather station to the construction site. The system, named WEATHER, is a software system that provides user-friendly interface, including menus, dialog boxes, and graphical capabilities to facilitate data input and output.     

Highway Construction Data Collection and Treatment in Preparation for Statistical Regression Analysis

Currently, there is not an understanding of the project factors having a statistically significant relationship with highway construction duration. Other industry sectors have successfully used statistical regression analysis to identify and model the project parameters related to construction duration. While the need is seen for such work in highway construction, there are very few studies which attempt to identify duration-influential parameters and their relationship with the highway construction duration. The purpose of this work is to describe the highway construction data needed for such a study, identify a data source, collect early-design project data, and prepare the data for statistical regression analysis. The Virginia Department of Transportation is identified as the optimal data source. The data collected include historical contract and project level parameters. To prepare for statistical regression analysis, the contract duration collected is converted to construction duration by a seasonal adjustment process which removes historically typical nonworking days.     

高密度电法在勘察了解公路路段近地表层断层、裂隙工作中的应用

修建公路时,有必要了解勘查路段近地表层断层、裂隙的赋存状态,为下一步公路施工设计提供地球物理依据。否则在施工中因地表层断层、裂隙等原因引发地面塌陷等地质灾害,轻则影响施工进度,给施工方造成经济损失,重则危及人员的生命安全。通过实例介绍高密度电法勘探在公路路基断层、裂隙勘探中的有效应用。     

Guidelines for Warranty Contracting for Highway Construction

This paper presents guidelines for implementing the construction warranty contracting method in the highway construction industry. A logical, step-by-step method for effectively applying the warranty contracting program for use in the highway construction industry is developed. Relevant issues that may present obstacles to the implementation are addressed, while the best practices, compiled from an evaluation of the current industry’s state-of-the-art practices, will assist an interested state highway agency in creating a warranty specification. In performing this research, the current use of warranty specifications among state highway agencies was examined, and an in-depth case study of the Wisconsin Department of Transportation’s warranty program was conducted.     

Long‐Range Forecasting Highway Construction Costs

In the process of decision making for design and execution of highway construction projects, long‐range cost forecasting is one of the most significant and complicated problems. This paper describes the development of a model that enables the user to make long‐range cost projections, taking into consideration general characteristics of the highway construction industry, as well as pertinent local conditions. The model presented uses conventional statistical methods to represent the main categories of typical jobs in the highway construction industry. From these categories, a composite model is created by assigning different weights to the input elements costs and then choosing a series of indicators to predict price trends for each separate element of the composite model. Use of this model reveals that bid volume in a certain area is a factor that has significant influence upon cost forecasts. This paper is accompanied by a case study based on actual data from highway construction projects performed for the Florida Department of Transportation in the years 1968–1981.     

新纪元大厦基坑边坡支护技术

文章介绍了深基坑采用喷锚对边坡土体进行支护的设计与施工技术,保证边坡的稳定.为今后施工高层建筑的基坑支护提供了一个简单易行的方法.     

Louisiana Highway Construction Cost Trend after Hurricanes Katrina and Rita

The objective of this study was to reveal the trend in highway construction costs following Hurricanes Katrina and Rita in Louisiana. The means of measuring highway construction cost was the Louisiana Highway Construction Index, an index made up of the cost of labor, equipment, and six major materials used in highway construction. Data from projects let by the Louisiana Department of Transportation and Development from the second quarter of 2003 to the second quarter of 2007 were used to track the change in construction costs. Index values from hurricane-impacted areas (GO Zones) were compared with those in Non-GO Zones. The indices revealed that two quarters after Hurricanes Katrina and Rita, the highway construction cost jumped about 20% statewide and 51% in GO Zone. Two years after the hurricanes, the cost has stabilized to around 30% increase over the pre-Katrina and Rita period. This study provides valuable information for the state agency to estimate cost escalation in ongoing projects and to estimate future disaster response to highway construction costs.