【作者】 崔诗慧；

【导师】 亢景付；

【作者基本信息】 天津大学 ， 建筑材料， 2012， 硕士

【摘要】 黄河小浪底排沙洞是我国首条采用无粘结双圈环绕预应力混凝土衬砌这种结构形式的水工隧洞,这种新型结构比传统有粘结预应力混凝土衬砌具有施工简单,且同样抗渗防裂效果好的特点。在施工阶段,小浪底排沙洞埋设了混凝土应变计、钢筋计、无应力计、锚索测力计、测缝计、多点位移计、渗压计等160只观测仪器。小浪底排沙洞从1998年3月施工,1999年6月达到全部运行条件,使用至今已十余年。在这期间,埋设的观测仪器采集了大量的观测数据。本文结合小浪底排沙洞工程,对锚索张拉阶段的预应力效果和混凝土的徐变以及运行阶段的温度和内水压力变化对混凝土衬砌的影响进行了研究。锚索张拉阶段通过合理的建立锚索张拉程序和数据采集制度,将混凝土的弹性应变、混凝土的徐变、预应力损失造成的应变从实测总应变分离出来,从而分析混凝土中建立的预压应力。运行阶段通过对观测数据进行数理统计得到温度和内水压变化对混凝土衬砌的影响。研究结果表明:(1)锚索张拉阶段,混凝土应变计测得的总应变中,混凝土的徐变占弹性应变的20%~30%,所以在分析预应力效果时,不能直接使用混凝土应变计的测量数据。(2)混凝土的徐变变化近似的与应力和持荷时间成正比,即ε=ασt。但分析结果显示其中系数α不是一个常数,而是与应力状态和约束条件有关的一个变量。(3)锚索张拉完毕后,除锚具槽处以外,混凝土衬砌中建立了较为均匀的预压应力。浇筑块端部的预应力平均值为-8MPa,中部的平均值为-6.7MPa。相比较而言,浇筑块中部建立的预压应力比浇筑块端部建立的预压应力更为均匀。(4)在排沙洞运行期间,混凝土中的压应变和温度压应力随着温度的升高而增加,随着温度的降低而减小。此规律在浇筑块的端部和衬砌的内侧更为明显。在分析时间段内,混凝土衬砌产生了最大-2.57MPa的温度应力,所以应对温度变化对结构的影响有足够的重视。(5)在排沙洞运行期间,混凝土中的压应变随着水头的增高而减小,随着水头的减小而增高。水头变化对混凝土衬砌不同部位的影响程度也不同,对浇筑块端部的影响大于浇筑块中部,平均水头每升高1m,混凝土衬砌减少0.38×10-6的压应变。更多还原

【Abstract】 Xiao Langdi sediment tunnel liner is the first case using double-looped unbonded prestressedly concrete lining around the hydraulic structure. This new type of structure is more simple construction and also good at anti-permeability cracking compared with traditional bonded prestressed concrete lining. During the construction period, the sediment tunnel liner instrumented with concrete strain meters, reinforcement meters, zero stress meters, anchorage load cells, joint meter, convergence meters and piezometer, totally 160. The tunnel were built from March 1998 to June 1999, at then reached to the full operating conditions. During the past twelve years, the instruments collected a lot of monitoring data. In this paper, the development of concrete stress and concrete creep over prestressing process for Xiao Langdi sediment tunnel liner were investigated based on the monitoring data of instruments. In the operational period, also research in the influence of various temperature and water pressure to the tunnel.By establishing a reasonable tensioning program and data collecting program, the total strain obtained from monitoring data were separated into elastic strains, concrete creep and the strain due to the prestress loss during the prestressing process. During the operation of the tunnel, the thesis reaches the stress and strain distribution in concrete with the methods of mathematical statistic analysis under different temperature and different water pressure conditions. Depending on the research, we may draw the following conclusions:(1) During the prestressing process ,the concrete creep account for 20% to 30% of the elastic strains . So the effects in the analysis of pre-stressed, it can’t directly use the strain obtained from monitoring date when analysis the prestressing effect of the tunnel.(2) Concrete creep is linearly related to the existing stress and the loading time t, which can be expressed asε=ασt , the coefficientαis not a constant but a variable relating to the stress and constraint conditions.(3) The distribution of stress on average is uniform in the tunnel except the part around the boxouts after the prestressing process. The average stress in the end of the construction block is -8MPa, in the middle of the construction block is -6.7MPa. The middle part’s stress is more uniform than the end part’s. (4) Concrete compressive strain and temperature stress increase with increasing temperature, decrease with decreasing temperature during the operating. This rule is more obvious in the end of the construction block and the inside lining. In the analysis period, it has a maximum stress due to the temperature changes is-2.57MPa in the concrete, so must pay enough attention to the impact of temperature changes.(5) Concrete compressive strain decreases with the increase of head, with the decrease of head higher. Different parts of the concrete lining has different impact with the head changes, it have more influence on the end of the construction block than in the middle , on average the head is increased by 1m, reducing 0.32×10-6 pressure strain in the concrete.更多还原