高温地区碾压混凝土重力坝的施工期温度裂缝控制

Thermal Cracking Control of RCC Gravity Dam Constructed in High Air Temperature and Dry Area

针对高温气候地区碾压混凝土重力坝坝体混凝土出现温度裂缝这一问题,阐述了裂缝成因和开裂机理,提出了相应的防止措施.早期的内外温差、后期基础温差是这类裂缝产生的主要原因.从优化水泥水化放热曲线角度出发,配置了一种能有效削减水化热峰值、实现双峰型水化放热的新缓凝高效减水剂,而优化水泥的水化放热过程并加以合适的表面保温与内部水管降温是防止这类裂缝的有效温控措施.基于混凝土温度场、应力场的基本原理和水管冷却的计算,对某一实际工程进行了仿真计算分析,计算结果表明在上述综合温控措施下,防裂效果良好.该措施对类似工程具有一定的参考价值.

With regard to the problem of concrete crack in the period of construction,the crack mechanism of a roller compacted concrete（RCC） gravity dam at high temperature area was presented and the corresponding prevention measures and methods were provided in this paper.The temperature difference between the internal and air at the early stage and the foundation temperature difference at the later stage were considered as the main factors to lead to crack.A new retarding high efficiency water-reducing agent which can effectively reduce the peak value of hydration heat and make double-humped hydration heat was produced to optimize the hydration heat curve of cement.Optimization of the process of cement hydration,the external heat preservation and internal pipe cooling are effective measures to prevent crack.Finally,based on theories of temperature field and stress field,the 3-D finite element method（FEM） with pipe cooling was adopted to simulate the thermal field and stress field of concrete project during construction.The results show that satisfactory temperature control and crack prevention are achieved.This provides be valuable reference for similar concrete projects in the future.