重力坝加高工程全年施工可行性研究

On the possibility of pouring concrete in the whole year in the heightening of concrete gravity dams

某重力坝加高工程中，为了减少温度应力，每年5～9月份停工，损失了近一半施工时间，为此研究了大坝加高中全年施工的可行性。首先，从理论上阐明，大坝加高中新混凝土温度应力不同于基础约束问题，而接近于上下层约束问题，其温度应力小于基础约束块，而且温差计算起点较高，因此温度应力较小，夏季施工是可能的。然后，严格模拟实际施工条件进行三维有限元仿真应力分析，计算结果表明，大坝加高工程中在采取必要措施后，热天不必停工，可以全年浇筑新混凝土，使施工进度有较大提高，但汛期应满足上游库水位限制的要求，文中给出了大坝加高中热天施工的技术措施。

In order to reduce thermal stresses in the construction process of the heightening of a gravity dam, the construction is ceased from May to September, losing 5 months a year in the construction period. The possibility of pouring concrete in the whole year in the heightening of gravity dam is discussed in this paper. First, in the heightening of a gravity dam, the thermal stress in the new concrete is different from that in the concrete block on the rock foundation, and is somewhat similar to the thermal stresses in the upper and lower layers in a high concrete block. Secondly, the starting point of temperature difference is the mean temperature of the downstream face of the dam which is higher than the steady temperature in the lower part of the upstream face of the dam. Thus, the thermal stress in the new concrete will be low and it is possible to pour concrete in the whole year. Strictly simulating the practical construction conditions, 3D finite element simulating computation are carried out for more than 20 schemes. The results of computation show that it is possible to pour concrete in the whole year with some technical measures being taken, but the limit height of water level in the upstream face must be obeyed.