沙河渡槽侧墙内侧表面裂缝成因分析及温控防裂措施研究

A Cause Analysis of Cracks on the Inner Surface of Side Wall of Shahe Aqueduct and Research on Temperature Control and Crack Prevention Measures

渡槽的槽身属于薄壁结构,其温度场和温度应力变化规律与大体积混凝土结构对应的变化规律差异较大。大型渡槽采用高强度等级混凝土,早期发热速度快,发热量高,在浇筑初期容易出现较大的内外温差,如果此时外界温度很低,极易导致表面出现的拉应力超过混凝土的抗拉强度,产生表面温度裂缝。采用ANSYS有限元软件对沙河渡槽进行温度场和温度应力仿真计算,分析了沙河渡槽侧墙内侧裂缝产生的原因。研究结果表明,渡槽侧墙混凝土由于施工期过大的内外温差和过快的降温速率,以及间歇面处的强约束作用在其内侧表面产生水平向过大的温度拉应力是导致侧墙内侧开裂的主要原因。针对裂缝成因提出了温控防裂措施并验证其合理性,避免了后续渡槽侧墙温度裂缝的产生,为工程的顺利进行创造了条件。

The aqueduct body is a thin-walled structure,and its temperature field and temperature stress variation are quite different from those of mass concrete structure.Large aqueduct is made of high strength concrete,which has fast heating speed and high heating value in the early stage.It is easy to have large temperature difference between inside and outside in the early stage of pouring.If the outside temperature is very low at this time,it is very easy to cause the tensile stress on the surface to exceed the tensile strength of concrete,resulting in surface temperature cracks.The temperature field and thermal stress of Shahe aqueduct are simulated by ANSYS,and the causes of cracks in the inner side wall of Shahe aqueduct are analyzed.The results show that the main reasons for the cracks in the inner side of aqueduct side walls are the excessive temperature difference between the inside and outside of aqueduct side wall concrete,the rapid cooling rate and the strong restraint at the intermittent surface.According to the causes of cracks,the temperature control measures are put forward and verified to be reasonable,so as to avoid the generation of temperature cracks in the subsequent tank body and create conditions for the smooth progress of the project.