【作者】 袁明道；

【导师】 肖明；

【作者基本信息】 武汉大学 ， 水利水电工程， 2013， 博士

【摘要】 能源的发展和经济的发展紧密相联,水力发电不仅仅是世界各国积极发展的可再生能源,也是我国能源供给的重要组成部分,今后我国十二五规划中,我国西部地区在建和待建的大型水电站工程的坝工结构多为200米级的高坝大坝,采用混凝土结构将是长期的结构选型。温度应力和温度控制是混凝土大坝建设中的瓶颈问题,水工大体积混凝土外掺MgO不仅仅可以简化温控措施、加快施工工期,而且提高混凝土抗裂性能。主要的研究内容：(1)结合重烧、轻烧MgO的基本特性,讨论了外掺重烧MgO、内含重烧水泥净浆的线膨胀变形特性。研究表明,外掺重烧、内含重烧MgO水泥净浆均不适用于工程实践。典型的MgO混凝土不同恒温条件下的自生体积变形研究表明,不同恒温条件下,MgO混凝土在经过3a左右的时间内基本都达到了稳定状态。3a～5a时MgO混凝土的自生体积变形是稳定变化的,不会产生突变性的无限膨胀,也没有出现回缩现象,其长期自生体积变形是稳定的,都不再发生进一步明显的变形增量。(2)综述了现有研究成果,结合广东长沙拱坝(粤西地区)、坝美拱坝(粤北地区)的工程实践,研究了不同温度、不同掺量条件下自生体积变形的规律的研究。针对国内外首座应用外掺氧化镁混凝土不分横缝快速筑拱坝技术的长沙拱坝,实施了长达8a的自生体积原型监测,提出MgO混凝土观测3a后,仍可能有10个微应变的自生体积缓慢增加。同时提出原型观测时间应以自生体积变形年增量不超过3个微应变且不少于5a为宜。(3)系统研究了不同水泥基试体(净浆、砂浆、一级配和二级配混凝土)在不同掺量MgO条件下的压蒸膨胀值,提出应以一级配混凝土作为压蒸法试验基体,且提出拌和应以干筛为准。外掺MgO水泥净浆、砂浆和混凝土的压蒸安定性试验中,研究不同掺量条件下的膨胀变形、抗压强度、抗折强度的相互关系,确定安定性的评定方法标准和控制指标。提出压蒸安定性标准应以抗压、抗折强度不降低为准,确定相应的极限掺量。首次提出MgO基体压蒸掺量屈服比ξ,并求出不同MgO掺量下砂浆和一级配、二级配混凝土的压蒸掺量屈服比ξ介于(0.95～1.03)于之间。压蒸膨胀率0.5%对应的MgO掺量再乘以压蒸掺量屈服比(0.95)可作为极限掺量依据。(4)系统研究自生体积变形特征的基础上,选用工程界易于接受的双曲线模型,以28d龄期和最终膨胀量等两个特征值,推求相关参数,并通过当量龄期法修正和代替常规方法的不足；实时分析方程中引入自生体积变形的膨胀变形增量,基于Ansys平台编制软件实现APDL的二次开发。(5)系统研究了氧化镁混凝土自生体积的变形特性,国内外首次设计了缓慢温降条件下的自生体积变形方案,研究其变形特性。详细分析了长沙拱坝裂缝的现状,结合工程实际开展了寒潮影响的数值分析。采用外掺Mg0混凝土筑坝新技术并非是大坝下游坝面出现裂缝的必然因素。1-2mm的细小裂缝对于长沙拱坝大坝整体的安全性态没有造成严重危害性的安全隐患。应明确混凝土表面保护应以强制性要求作为永久工程,确因条件限制,对于寒潮出现频率较高(以10月份出现1.5～2.0次以上)的地区,混凝土表面保护应做为永久工程。更多还原

【Abstract】 The hydropower industry plays an important role in the energy industry of China. Development of energy is closely related with economic development. The hydroelectric power is not only the renewable energy actively developed by countries throughout the whole world, but the important part of China’s energy supply. Large-sized hydropower projects being constructed and under construction in the west area mostly applied the structure with the200m high dam and the concrete structure will be the choice for a long time. Temperature stress and temperature control are the bottlenecks during construction of concrete dam. Mixing of MgO into hydraulic mass concrete can not only simplify the temperature control measures and accelerate the construction period, but improve the concrete cracking resistance. The major results include:(1) According to the research, cement paste with mixed dead-burn MgO and cement paste with dead-burn MgO included are not applicable to engineering practice. According to the research on autogenous volume deformation of the typical MgO concrete under different constant temperatures, MgO concrete will basically become stable within about3a hours. Autogenous volume deformation of MgO concrete in3a-5a hours is stably changed and free from mutagenic infinite expansion and rebound phenomenon. The concrete is stable in autogenous volume deformation on a long term basis and free from obvious deformation increment.(2) To study the autogenous volume deformation discipline under different temperature and different dosage conditions, by summarizing the current research results and combining engineering practices of Guangdong Changsha dam (West region of Guangdong) and Bamei dam (North region of Guangdong). By applying autogenous volume prototype monitoring to Changsha dam which is the first in China to apply the quick dam construction technique of mixed MgO concrete irrespective of cross joint, the author makes the comment that10micro-strained autogenous volume of MgO concrete are still slowly increased after observation for3a. The proposal that the prototype observation time shall be preferably subject to annual increment of autogenous volume deformation which shall be not more than3micro strains and not less than5a.(3) This paper studies the autoclave-treated expansion values of cement base specimens(paste, mortar, one grading concrete and two grading concrete) under different MgO dosage conditions and raises the proposals that the one grading concrete shall be applied as the base for autoclave-treated test and mixing activity shall be subject to dry screening. In the autoclave-treated stability test of mixed MgO cement paste and mortar and cement, the paper studies relationship among expansion deformation, compressive strength and flexural strength under different dosage conditions to determine the evaluation method standard and control target of stability.It states that the autoclave-treated stability standard shall be subject to no reduction of compressive strength and flexural strength to determine relevant limit content. This paper gives the autoclave-treated content yield ratioζ; and concludes that autoclave-treated content yield ratio of mortar and one grading and two grading concretes with different MgO content shall fall between0.95～1.03. The MgO content under autoclave-treated expansibility0.5%multiplying autoclave-treated content yield ratio (0.95) can be used as a basis for evaluating limit content of MgO.(4) Upon systematic study on autogenous volume deformation characteristic, the paper adopts hyperbolic model acceptable to engineering industry and obtains the relevant parameters from28d age and final expansion value, as well as corrects and substitutes the weak points of conventional methods with equivalent age method. It also analyzes on a real-time basis the expansion deformation increment of autogenous volume deformation introduced in the equation and compiles software on the basis of Ansys platform to achieve the APDL secondary development.(5) The paper systematically studies the autogenous volume deformation characteristic of MgO concrete and first designs the autogenous volume deformation proposal under slow temperature reduction condition to study the deformation characteristic. This paper analyzes in detail the current status of Changsha dam cracks and conduct the data analysis of cold wave impact by combing engineering practice. Application of Mgo-mixed concrete dam construction technique is not a necessary cause for cracks appearing in the downstream dam face. Thin cracks of l～2mm have no serious harmful hazard on overall safety of Changsha dam. It should be defined that protection of concrete face shall be mandatorily treated as a permanent work. As for areas where cold wave occurs frequently (above1.5～2.0in October) due to condition limit, the surface of the concrete shall be protected on a permanent basis.更多还原