Deformation of the central pier of the permanent shiplock, Three Gorges Project, China: an analysis case study

The central pier (CP) is one of the key structures of the permanent shiplock in the Three Gorges Project on the Yangtze River, China. This paper deals with the study of the rock mass deformation of the CP of the second shiplock under various operation conditions. Numerical simulations using the 2-D distinct-element method and 3-D finite-element method are applied to analyze the rock mass deformation. Also, time-series analysis and gray system theory are used to predict the trends of rock displacements based on in situ measured data. The results can be summarized as follows: (1) the main deformation of the rock mass in the CP occurs after excavation completion, while the shiplock is in operation, the dominant displacements mainly occurring on both sides of the northern chamber, developing generally towards the chamber; (2) the horizontal displacement varies with the process of excavation, and is in a steady state after excavation, and during operation of the shiplock the displacement is slightly decreased; (3) the horizontal displacement parallel to the axial line of the shiplock occurs downstream; and (4) the vertical displacement occurs during excavation, and then subsidence with various values takes place in different parts of the CP for different operation conditions.     

三峡永久船闸高边坡开挖及加固支护设计

永久船闸高边坡是三峡工程的重要建筑物，也是船闸结构的重要组成部分，规模巨大，技术复杂。确定合理的设计原则，选定合适的安全度标准，拟定合理的开挖形态和进行恰当的加固支护，制定合理的开挖与加固施工程序，确保边坡稳定和变形满足结构及运行要求是船闸高边坡设计中研究的主要问题。本结合围绕高边坡设计所进行的大量试验及分析研究成果，系统介绍了船闸高边坡的基本设计思想及开挖与加固支护基本设计方案。     

三峡船闸高边坡裂隙岩体渗流监测成果分析

三峡船闸是三峡工程的主要工程之一。闸室区边坡高度一般为70～120m,最高约160m,地下水是影响岩体高边坡稳定的重要因素之一。介绍了船闸高边坡施工期地下水渗流监测的布置和实施情况,根据将近3 a的实际监测成果,分析了施工期船闸高边坡地表降雨、排水、水质、排水硐渗流渗压的变化规律和影响因素;监测成果分析认为,施工期船闸南北边坡地下水位均低于设计水位,与长江科学院计算成果基本一致,随着二期工程的实施,地下水位将随之缓慢降低,说明设计最后选定的渗控方案是基本合理的。     

Assessment of rock mass characteristics and the excavation disturbed zone in the Lingxin Coal Mine beneath the Xitian river, China

Safe production and induced hazard prevention in coal mines mainly concern problems in the excavation disturbed zone (EDZ), but coal mining can also make a significant impact on the environment. Comprehensive techniques using a borehole TV viewer system, electrical logging, and monitoring of drilling fluid leakage offer the ability to identify changing geological conditions and the location of any nearby abandoned mining workings. The inner collapsed zone and the expanding height of the crack zone transmitting water plus their spatial distribution after excavating the superincumbent coal seam stratum are determined at no. L3414 workings, Lingxin Coal Mine beneath the Xitian river, China. An integrated system of GIS-based on a stochastic model, which has been developed for the prediction of dynamic subsidence coupling the time function and probabilistic integral method, is verified through practice at the Lingxin Coal Mine. This development has greatly expanded the ability of the mine operator to characterize previously inaccessible areas of the mine, providing a reliable basis for safe mining and prevention of induced-hazards to ensure high production mining underneath the river bed.     

三峡工程永久船闸高边坡岩体变形声发射监测

岩体声发射检测是当今国内外积极开发研究的岩体动态监测新技术之一,为了保证三峡船闸顺利建设,在建设过程中采用了声发射技术对船闸高边坡进行全天候在线监测。声发射作为动态监测技术在大型边坡岩体动态监测中具有明显优势。本文将小波变换和神经网络应用到声发射检测之中,能够准确地对岩体稳定性进行预测预报。现场监测表明,利用声发射技术对大型船闸高边坡岩体稳定性及其发展趋势和边坡支护效果,作出了符合实际的评价和有效的预测预报。     

Key issues in rock mechanics of the Three Gorges Project in China

The Three Gorges Project is one of the essential key projects for flood controlling and water resources regulation in the Yangtze River.The project includes a river-crossing dam,underground powerhouses,and navigation structures.Because of the huge size and complicated construction technologies,the project faced a series of challenging engineering issues.In terms of rock mechanics,there are many key technical issues,including the sliding resistance and stability of the dam section along the foundations of powerhouses No.1-5,the slope stability of the double-line five-stage shiplock,excavation of large-scale underground powerhouses,and curtain grouting under the dam.With decades of scientific research and 16 years of practical construction experiences and reservoir operations,these key technical issues in construction of the Three Gorges Project are successfully resolved,which will attribute to the development of hydropower technology.On the basis of the monitoring data during construction and normal operation periods of the Three Gorges Project,this paper presents a systematic analysis of these key rock mechanical issues in terms of behaviors,solutions,dynamic controlling,monitoring arrangement and integrated assessment.     

边坡工程地质信息的三维可视化及其在三峡船闸边坡工程中的应用

提出用各种线符及其组合概化岩体结构和物性两类信息，并建立起相应的拟合函数，实现工程地质结构及边坡工程开挖的三维模拟和再现。根据实测的离散点信息建立起三维可视化模型，显示任意位置的剖面和平切面图及其它方面的三维计算。最后成功地应用到长江三峡永久船闸边坡工程的三维地质结构模拟和信息的再现。     

三峡工程二期上游围堰的帷幕灌浆

三峡工程二期上游围堰防渗墙下帷幕灌浆是围堰基础防渗处理的主要形式。在防渗墙与基岩接触带以及基岩内的不同风化带岩体内,均进行了帷幕灌浆。根据帷幕灌浆的大量资料,综合分析研究接触带以及堰基基岩不同风化带内的帷幕灌浆的特征、透水性与岩体的可灌性关系、外冒漏浆控制因素以及帷幕形成后防渗的可靠性。     

Nutrient characteristics in the Yangtze River Estuary and the adjacent East China Sea before and after impoundment of the Three Gorges Dam

From November 2002 to 2006, five cruises were undertaken in the Yangtze River Estuary and the adjacent East China Sea to compare the nutrient concentrations, ratios and potential nutrient limitation of phytoplankton growth before and after impoundment (June 2003) of the Three Gorges Dam (TGD). Concentrations of dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and total nitrogen (TN) exhibited an increasing trend from 2002 to 2006. In contrast, total phosphorus (TP) concentration exhibited a decreasing trend. The mean concentrations of DIN, SRP, and TN in the total study area increased from 21.4 µM, 0.9 µM, and 41.8 µM in 2002 to 37.5 µM, 1.3 µM, and 82.2 µM in 2006, respectively, while TP decreased from 2.1 µM to 1.7 µM. The concentration of dissolved reactive silica (DRSi) had no major fluctuations and the differences were not significant. The mean concentration of DRSi in the total study area ranged from 52.5 to 92.3 µM. The Si:N ratio decreased significantly from 2.7 in 2002 to 1.3 in 2006, while TN:TP ratio increased from 22.1 to 80.3. The area of potential P limitation of phytoplankton growth expanded after 2003 and potential Si limitation appeared in 2005 and 2006. Potential P limitation mainly occurred in an area of salinity less than 30 after 2003, while potential Si limitation occurred where the salinity was greater than 30. By comparison with historical data, the concentrations of nitrate and SRP in this upper estuary during November 1980-2006 increased obviously after impoundment of TGD but DRSi decreased. Meanwhile, the ratios of N:P, Si:N and Si:P decreased obviously.     

长江三峡库区移民城市发展与道路交通建设的互动关系

长江三峡工程促进了库区移民城市的快速发展,区域与城市道路交通的建设发挥了重要作用。文章通过分析移民城市道路建设的主要影响因素,以及与城市协调发展中存在的问题,从山地城市特征、内外交通衔接及道路建设的技术措施等方面,总结移民城市建设与道路交通的互动关系。     

长江三峡库区支线航空运输发展对策研究

长江三峡库区丰富的自然与人文旅游资源,狭长的地形与复杂的山地环境特征,决定了支线航空有广阔的前景。支线航空运输具有建设投资省、方便快捷、服务半径大等优点,是三峡库区发展旅游的重要基础条件。分析了长江三峡库区航空运输的现状及存在问题,结合区域城镇体系建设及综合交通发展,提出了支线航空交通的前景与发展对策。     

三峡水库变动回水区河道推移质输移特性研究

根据三峡库区有关的野外实测资料、模型试验和计算资料,分析三峡水库变动回水区河道推移质淤积规律。同时还提出了在现有的研究成果没有注意到的几个推移质泥沙输移的问题。     

Opening the excavation chamber of the large-diameter size slurry shield: A case study in Nanjing Yangtze River Tunnel in China

Shield tunnel construction in a dense strata often encounters malfunction of shield-tunneling machine or abrasion of cutters. Accessing to an excavation chamber under compressed air is a main method to repair and replace worn cutters. And many safety issues such as stability of the excavation face were involved. However, the face stability due to opening an excavation chamber was not fully studied. To overcome this shortcoming, face support scheme and stability analysis were presented in a case history of opening the pressure chamber for a large-diameter (up to 14.93 m) slurry shield tunnel constructed underneath Nanjing Yangtze River. Since most of the damaged cutters were distributed along the edge of cutting wheel, only top 3 m of tunnel face within the chamber needed to be supported by compressed air, and remaining area would also to be supported by slurry pressure. A series of simple primary laboratory tests were carried out to design an optimum slurries mixing scheme to support the tunnel face as accessing to the pressure chamber in the project. The face stability was analyzed in terms of the pressure equilibrium (i.e., internal and external pressures) as well as three-dimensional numerical analysis by adopting properties of soils and filter cakes from laboratory tests. By injecting lower density slurry into the sand to form a stable infiltration zone, followed by using higher density slurry to create a filter cake at tunnel face, compressed air-support system could ensure face stability during maintenance of cutter wheel. The success of applying the mixed slurry and compressed air-support scheme in this project is valuable to shield tunnel constructions in similar ground conditions.     

Numerical simulation of the excavation damaged zone around an opening in brittle rock

The micromechanics-based damage model proposed by Golshani et al. [A micromechanical model for brittle failure of rock and its relation to crack growth observed in triaxial compression tests of granite. Mech Mater 2006;38:287–303] is extended so that time-dependent behavior of brittle material can be taken into account, with special attention to the numerical analysis of an excavation damaged zone (EDZ) around an opening, which is a major concern in assessing the safety of underground repositories. The present model is capable of reproducing the three characteristic stages of creep behavior (i.e., primary, secondary, and tertiary creep) commonly observed in the laboratory creep tests. The sub-critical microcrack growth parameters (i.e., n and A) can be determined for Inada granite by fitting the numerical results of elapse time to failure versus the creep stress ratio curve with the experimental data under both dry and wet conditions. It is found that moisture has a significant influence on the parameter A rather than the parameter n. Use of the extended model makes it possible to analyze not only the extension of microcrack length, but also the development of EDZ around an opening as a function of time. The damaged zones mainly develop in the sidewalls of the opening in the case that the vertical stress σ₂₂ is larger than the horizontal stress σ₁₁.     

三峡工程永久船闸高边坡岩体变形特征与机理分析

三峡工程船闸高边坡变形监测资料表明,岩体变形主要受开挖卸荷影响,边坡岩体卸荷松邓特征明显,具有分带性。微风化新鲜岩体变形主要是沿结构面张开实现的,从而引起岩面找平混凝土或喷护混凝土开裂。岩体变形大小与变化过程还与地质条件、施工爆破、锚固等因素有关。     

长江三峡库区野果植物资源区系特征分析

根据"长江三峡库区野果植物资源数据库",采用植物区系分析方法,对长江三峡库区野果植物资源区系特征进行了系统分析和研究,得出以下结论:库区野果植物资源在库区植被中占据相当的优势;长江三峡库区野果植物中主要成分为含10种以上的大科和大属;分布区类型分析表明库区野果植物与热带植物区系和北温带植物区系有一定的联系:拥有丰富的特有科属植物种类.     

三峡二期工程右纵上游坝面裂缝处理质量控制

介绍裂缝处理方案及项目实施过程中,监理工程师根据现场施工特点,及时规范现场验收签证程序,制定施工质量管理办法,并对裂缝处理各施工工序严格把关,有效地保证了裂缝处理施工质量。     

三峡工程的防排水措施与材料

介绍了三峡工程中大坝、永久船闸基础及一些建筑物的防排水措施和所用材料。