【摘要】：隨著碾壓混凝土筑壩技術(shù)的迅速發(fā)展，國(guó)內(nèi)外興起了各類(lèi)碾壓混凝土拱壩的建設(shè)，但隨之出現(xiàn)了大壩在運(yùn)行后的壩體開(kāi)裂問(wèn)題。碾壓混凝土拱壩的裂縫大多數(shù)是由于溫度應(yīng)力引起，因此，如何在施工過(guò)程中通過(guò)溫度控制措施防止裂縫成為了碾壓混凝土拱壩發(fā)展的重要課題。碾壓混凝土拱壩的溫度應(yīng)力和溫控措施都有自己的特點(diǎn)，與常態(tài)混凝土相比碾壓混凝土在材料參數(shù)和施工方法上有較大的區(qū)別，加之拱壩不同于重力壩，不能解除其在壩軸線方向壩體溫度變形所受到的約束，壩內(nèi)將產(chǎn)生較大的溫度應(yīng)力。本文以ANSYS有限元軟件為平臺(tái)，，綜合考慮拱壩施工過(guò)程及外界因素的影響，對(duì)碾壓混凝土拱壩的幾種溫控措施進(jìn)行仿真研究，主要成果如下： （1）以某碾壓混凝土雙曲拱壩為依托工程，計(jì)算過(guò)程中考慮外界氣溫、水溫、混凝土水化熱及夏季停工度汛等多種因素，運(yùn)用有限元數(shù)值分析法研究碾壓混凝土拱壩從開(kāi)始澆筑到蓄水運(yùn)行的整個(gè)過(guò)程中的溫度場(chǎng)；綜合考慮施工過(guò)程中壩體自重、混凝土彈模和蓄水過(guò)程中水壓力的變化，模擬大壩澆筑施工運(yùn)行全過(guò)程，得到溫度場(chǎng)主要影響下應(yīng)力場(chǎng)的發(fā)展過(guò)程。 （2）依據(jù)碾壓混凝土拱壩溫度及應(yīng)力控制標(biāo)準(zhǔn)，分析大壩在無(wú)溫控措施下出現(xiàn)的問(wèn)題，討論大壩可能出現(xiàn)裂縫的位置及原因。研究表明：未采取溫控措施時(shí)，壩體內(nèi)部溫度較高，在整個(gè)施工期最高溫度都超過(guò)28℃，而外表面受外界因素的影響溫度較低，內(nèi)外溫差超過(guò)控制標(biāo)準(zhǔn)；分期施工形成的新老混凝土結(jié)合面附近因間歇時(shí)間長(zhǎng)且過(guò)水而產(chǎn)生較大的上下層溫差；大壩出現(xiàn)較大拉應(yīng)力的位置在中上部拱端處，因自重作用和兩側(cè)基巖的約束使兩壩肩受拉，尤其在分期施工的結(jié)合面附近出現(xiàn)施工過(guò)程中最大的拉應(yīng)力1.7MPa；壩體出現(xiàn)較大壓應(yīng)力且長(zhǎng)期受壓的位置在靠近底層基巖的拱兩端，但最大壓應(yīng)力值小于容許壓應(yīng)力。 （3）針對(duì)上述問(wèn)題制定相應(yīng)的溫控措施，按不同影響因素?cái)M定方案進(jìn)行仿真分析，對(duì)比研究溫度隨時(shí)間的變化規(guī)律和溫控效果，總結(jié)各措施溫控特點(diǎn)，找到最佳溫控方案。結(jié)果表明：采取上下游面保溫措施可使壩體表面溫度升高13℃左右，可有效減小內(nèi)外溫差，降低表面裂縫發(fā)生的幾率；對(duì)分期施工形成的新老混凝土結(jié)合面上采用聚乙烯泡沫塑料板進(jìn)行保溫隔熱，可有效降低上下層溫差；采取壩內(nèi)水管冷卻措施后，壩體各部位最高溫度降低5~10℃，有效地控制了溫度，有利于減小內(nèi)外溫差及溫度應(yīng)力；最直接有效的溫控方法是降低混凝土澆筑溫度，每降低2℃，可使壩內(nèi)最高溫度降低0.2~0.9℃。 （4）綜合上述四種溫控措施的最佳方案進(jìn)行仿真計(jì)算，得到壩體溫度、應(yīng)力分布規(guī)律，結(jié)果顯示壩體最高溫度降低了11℃，最大拉應(yīng)力降低了0.47MPa，Mises等效應(yīng)力分布均勻，平均降低0.2MPa，組合溫控措施使各種溫差及應(yīng)力均控制在標(biāo)準(zhǔn)范圍之內(nèi)。對(duì)比各措施溫控效果，組合溫控措施最大拉應(yīng)力在各時(shí)段平均降低22.27%，水管冷卻措施在各時(shí)段效果都很顯著，表面保溫措施在停工度汛期間效果最佳。
[Abstract]:With the rapid development of RCC damming technology, the construction of all kinds of RCC arch dams has been developed at home and abroad, but the problem of the cracking of the dam after the operation has appeared. Most of the cracks in the RCC arch dam are caused by the temperature stress. So, how to prevent the crack through the temperature control measures during the construction process. For the development of roller compacted concrete arch dam, the temperature stress and temperature control measures of RCC arch dam have its own characteristics. Compared with normal concrete, the roller compacted concrete has a great difference in material parameters and construction methods. Besides, the arch dam is different from the gravity dam. It can not relieve the deformation of the dam body temperature in the axis direction of the dam. In this paper, the ANSYS finite element software is used as the platform. Considering the influence of the construction process and the external factors of the arch dam, several temperature control measures of the RCC arch dam are simulated and studied. The main achievements are as follows:
(1) taking a RCC Double Curved Arch Dam as the support project, the temperature field, water temperature, water temperature, concrete hydration heat and summer stop flood are considered in the calculation process, and the temperature field in the whole process of RCC arch dam from starting to water storage is studied by the finite element method. The water pressure changes in the body weight, the concrete elastic modulus and the water storage process. The whole process of dam construction operation is simulated, and the development process of the stress field under the main influence of the temperature field is obtained.
(2) according to the temperature and stress control standard of the roller compacted concrete arch dam, the problems of the dam under no temperature control measures are analyzed, and the location and reasons of the possible cracks are discussed. The study shows that the temperature of the dam is higher when the temperature control measures are not taken, and the highest temperature in the whole construction period is over 28 degrees, and the outer surface is affected by the external factors. The temperature difference is lower and the internal and external temperature difference exceeds the control standard. The temperature difference between the upper and lower layers of the new and old concrete composite surface formed by stage construction is due to the long interval of intermittent time and over water. The large tensile stress of the dam is located at the arch end of the middle and upper parts, and the two dam shoulder is pulled by the self gravity action and the constraints of the two sides of the bedrock, especially in stages. The maximum tensile stress 1.7MPa in the construction process is found near the joint surface, and the dam body has large compressive stress and the long compression position is located at both ends of the arch near the base rock, but the maximum pressure stress is less than the permissible pressure stress.
(3) according to the above problems, the corresponding temperature control measures are formulated, and the simulation analysis is made according to the different influence factors. The temperature control and temperature control are compared and studied. The temperature control characteristics of various measures are summarized and the best temperature control scheme is found. The results show that the temperature of the upper and lower surface heat preservation can increase the surface temperature of the dam body to about 13 degrees. It can effectively reduce the internal and external temperature difference and reduce the probability of surface cracks. Thermal insulation can effectively reduce the temperature difference between the upper and lower layers by adopting polyethylene foam board on the new and old concrete combination surface formed by installment, and the highest temperature of each part of the dam is reduced by 5~10 C after adopting the cooling measures of the inner water pipe of the dam, and the temperature is effectively controlled. It is beneficial to reduce the internal and external temperature difference and the temperature stress, and the most direct and effective temperature control method is to reduce the pouring temperature of concrete, and the maximum temperature in the dam can be reduced by about 0.2~0.9 C by each reduction of 2 degrees C.
(4) the optimum scheme of the above four temperature control measures is simulated, and the temperature and stress distribution of the dam body are obtained. The results show that the maximum temperature of the dam is reduced by 11, the maximum tensile stress is reduced by 0.47MPa, the equivalent stress distribution of the Mises is uniformly distributed, the average reduction of 0.2MPa is reduced, and the combined temperature control measures are controlled in the range of temperature and stress in the standard range. Within the temperature control effect of each measure, the maximum tensile stress of the combined temperature control measures is reduced by 22.27% on average in each period. The water pipe cooling measures are very significant in each period, and the effect of surface insulation is best during the shutdown period.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：TV642.4

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