The successful completion of the Zhengzhou-Xi＇an high-speed railway project has greatly improved the construction level of China＇s large-section loess tunnels, and has resulted in significant progress being made in ...The successful completion of the Zhengzhou-Xi＇an high-speed railway project has greatly improved the construction level of China＇s large-section loess tunnels, and has resulted in significant progress being made in both design theory and construction technology. This paper systematically summarizes the tech- nical characteristics and main problems of the large-section loess tunnels on China＇s high-speed railway, including classification of the surrounding rock, design of the supporting structure, surface settlement and cracking control, and safe and rapid construction methods. On this basis, the key construction tech- niques of loess tunnels with large sections for high-speed railway are expounded from the aspects of design and construction. The research results show that the classification of loess strata surrounding large tunnels should be based on the geological age of the loess, and be determined by combining the plastic index and the water content. In addition, the influence of the buried depth should be considered. During tunnel excavation disturbance, if the tensile stress exceeds the soil tensile or shear strength, the surface part of the sliding trend plane can be damaged, and visible cracks can form. The pressure of the surrounding rock of a large-section loess tunnel should be calculated according to the buried depth, using the corresponding formula. A three-bench seven-step excavation method of construction was used as the core technology system to ensure the safe and rapid construction of a large-section loess tunnel, following a field test to optimize the construction parameters and determine the engineering measures to stabilize the tunnel face. The conclusions and methods presented here are of great significance in revealing the strata and supporting mechanics of large-section loess tunnels, and in optimizing the supporting structure design and the technical parameters for construction.展开更多
There are many karst areas within Wuhan-Guangzhou route. Karst grouting is one of the main construction procedures of the sub-grade construction. Through construction art tests,construction principles,water and cement...There are many karst areas within Wuhan-Guangzhou route. Karst grouting is one of the main construction procedures of the sub-grade construction. Through construction art tests,construction principles,water and cementation ratio,grouting construction key points and quality check requirements were determined. Grouting quantity and pressure can be determined according to different geology conditions. Recommendations for quality problems such as bad practicability of grouting,unexpected dissipation of slurry,slurry belching,and overfeeding of slurry going to non-grouting area were proposed.展开更多
Pavements require maintenance to prevent undue distress or to restore performance; however, pavement maintenance and its impacts do not receive enough attention in many cases, and are either ignored or treated as a lo...Pavements require maintenance to prevent undue distress or to restore performance; however, pavement maintenance and its impacts do not receive enough attention in many cases, and are either ignored or treated as a low priority, Most current maintenance activities have budget issues and only focus on removing deteriorated pavement sections, Deferred pavement maintenance has impacts on the environment and on society, and may thus affect the costs associated with maintenance, A sustain- ability rating tool is a good way to list, explain, and evaluate such impacts, Various sustainahility rating tools have been developed for pavement; however, pavement maintenance has its own features that are different from those of the new construction, expansion, or reconstruction of pavements, This research project reviews nine sustainahility rating tools for pavement, although none of these tools fully describe maintenance features or can he directly applied to evaluate maintenance projects, A new sustainahility rating tool is then developed for pavement maintenance; this new tool can he used to evaluate individual projects and raise public awareness about the importance of pavement mainte- nance, Its details are described, and its use is demonstrated through an example to show the evaluation process and results,展开更多
Alternative contracting techniques have been frequently used in highway construction in the United State and have played an important role in the effort to improve construction project performance. However, it is stil...Alternative contracting techniques have been frequently used in highway construction in the United State and have played an important role in the effort to improve construction project performance. However, it is still unknown whether which project factors have significant influence on project performance. It is essential to learn from the experiences and opinions of construction project managers who had executed innovative or alternative contracts in order to improve and refine the usage of alternative contracting methods. Innovative contracting methods have been used by state Departments of Transportation for many years, so there is now sufficient data to measure the effectiveness of these innovations. Working under a grant from the Florida Department of Transportation （FDOT）, the research team used the experiences and opinions of construction field engineers who had executed innovative contracts on FDOT projects to measure the effectiveness of these systems. To that end, interviews were conducted with FDOT and consultant personnel from across Florida. All interviewed were project managers who had overseen at least one project using an innovative contracting method. Discussions brought enthusiastic responses from those interviewed, both for and against certain innovations. This paper will focus on the experiences and opinions of those experienced construction field engineers dealing with well-known innovations, as well as newer innovations such as ＂Detour Rental＂ and ＂Damage Recovery＂.展开更多
文摘The successful completion of the Zhengzhou-Xi＇an high-speed railway project has greatly improved the construction level of China＇s large-section loess tunnels, and has resulted in significant progress being made in both design theory and construction technology. This paper systematically summarizes the tech- nical characteristics and main problems of the large-section loess tunnels on China＇s high-speed railway, including classification of the surrounding rock, design of the supporting structure, surface settlement and cracking control, and safe and rapid construction methods. On this basis, the key construction tech- niques of loess tunnels with large sections for high-speed railway are expounded from the aspects of design and construction. The research results show that the classification of loess strata surrounding large tunnels should be based on the geological age of the loess, and be determined by combining the plastic index and the water content. In addition, the influence of the buried depth should be considered. During tunnel excavation disturbance, if the tensile stress exceeds the soil tensile or shear strength, the surface part of the sliding trend plane can be damaged, and visible cracks can form. The pressure of the surrounding rock of a large-section loess tunnel should be calculated according to the buried depth, using the corresponding formula. A three-bench seven-step excavation method of construction was used as the core technology system to ensure the safe and rapid construction of a large-section loess tunnel, following a field test to optimize the construction parameters and determine the engineering measures to stabilize the tunnel face. The conclusions and methods presented here are of great significance in revealing the strata and supporting mechanics of large-section loess tunnels, and in optimizing the supporting structure design and the technical parameters for construction.
文摘There are many karst areas within Wuhan-Guangzhou route. Karst grouting is one of the main construction procedures of the sub-grade construction. Through construction art tests,construction principles,water and cementation ratio,grouting construction key points and quality check requirements were determined. Grouting quantity and pressure can be determined according to different geology conditions. Recommendations for quality problems such as bad practicability of grouting,unexpected dissipation of slurry,slurry belching,and overfeeding of slurry going to non-grouting area were proposed.
文摘Pavements require maintenance to prevent undue distress or to restore performance; however, pavement maintenance and its impacts do not receive enough attention in many cases, and are either ignored or treated as a low priority, Most current maintenance activities have budget issues and only focus on removing deteriorated pavement sections, Deferred pavement maintenance has impacts on the environment and on society, and may thus affect the costs associated with maintenance, A sustain- ability rating tool is a good way to list, explain, and evaluate such impacts, Various sustainahility rating tools have been developed for pavement; however, pavement maintenance has its own features that are different from those of the new construction, expansion, or reconstruction of pavements, This research project reviews nine sustainahility rating tools for pavement, although none of these tools fully describe maintenance features or can he directly applied to evaluate maintenance projects, A new sustainahility rating tool is then developed for pavement maintenance; this new tool can he used to evaluate individual projects and raise public awareness about the importance of pavement mainte- nance, Its details are described, and its use is demonstrated through an example to show the evaluation process and results,
文摘Alternative contracting techniques have been frequently used in highway construction in the United State and have played an important role in the effort to improve construction project performance. However, it is still unknown whether which project factors have significant influence on project performance. It is essential to learn from the experiences and opinions of construction project managers who had executed innovative or alternative contracts in order to improve and refine the usage of alternative contracting methods. Innovative contracting methods have been used by state Departments of Transportation for many years, so there is now sufficient data to measure the effectiveness of these innovations. Working under a grant from the Florida Department of Transportation （FDOT）, the research team used the experiences and opinions of construction field engineers who had executed innovative contracts on FDOT projects to measure the effectiveness of these systems. To that end, interviews were conducted with FDOT and consultant personnel from across Florida. All interviewed were project managers who had overseen at least one project using an innovative contracting method. Discussions brought enthusiastic responses from those interviewed, both for and against certain innovations. This paper will focus on the experiences and opinions of those experienced construction field engineers dealing with well-known innovations, as well as newer innovations such as ＂Detour Rental＂ and ＂Damage Recovery＂.
