新疆大石峡水利枢纽无压泄洪洞衬砌混凝土温控防裂研究

Study on Temperature Control and Crack Prevention of Concrete Lining for the Non-pressure Spillway Tunnel of Dashixia Water Control Project in Xinjiang

受高速水流长期冲刷作用的影响,泄洪洞衬砌混凝土一旦产生裂缝,必将引起过流面的空蚀破坏,进而影响工程的正常稳定运行。因此,对泄洪洞衬砌混凝土进行温控防裂研究具有重要意义。依托大石峡水利枢纽泄洪排沙洞工程,采用三维有限元法,计算分析了不同温控措施下泄洪洞衬砌混凝土温度及温度应力的变化规律,论证了不同温控措施的适宜性。结果表明:喷雾洒水措施对改善衬砌混凝土表面温度应力具有一定的效果,并对混凝土干缩裂缝有明显的抑制作用;通水冷却措施主要侧重于改善衬砌混凝土内部的温度和应力状况,但会促使降温过程提前产生,增加早期开裂的风险,因此在施工过程中应严格控制混凝土降温速率和早期降温幅度,建议控制混凝土降温速率不超过2.0~2.5℃/d;施工初期和冬季低温时期均是温度裂缝发生的较危险时段,以冬季保温措施配合施工期的降温措施可以获得更佳的效果。研究成果可为类似泄洪洞工程衬砌混凝土的温控防裂设计与施工提供参考。

Under the long-term scouring effect of high-speed water flow,once cracks occur in the concrete lining of the spillway tunnel,it will inevitably cause cavitation damage to the flow surface,thereby affecting the normal and stable operation of the project.Therefore,it is of great significance to conduct temperature control and crack prevention study on the lining concrete of the spillway tunnel.Based on the flood discharge and sediment discharge tunnel project of the Dashixia water control project,the three-dimensional finite element method is used to calculate and analyze the changes in temperature and temperature stress of the lining concrete of the flood discharge tunnel under different temperature control measures.The suitability of different temperature control measures is demonstrated.The results show that spray watering measures have a certain effect on improving the temperature stress on the surface of lining concrete,and have a significant inhibitory effect on concrete shrinkage cracks;water cooling measures mainly focus on improving the temperature and stress conditions inside the lining concrete,but will prompt untimely occurrence of the cooling process,which increases the risk of early cracking.Therefore,the concrete cooling rate and early cooling amplitude should be strictly controlled during the construction process.This study recommends that the concrete cooling rate be controlled to not exceed 2.0~2.5℃/d;both the early stages of construction and low temperature periods in winter are prone to occurrence of cracks.Combining winter insulation measures with cooling measures during construction can achieve better results.The study results of this paper can provide reference for the design and construction of temperature control and crack prevention measures for concrete lining of similar flood-discharge tunnel projects.