地铁车站侧墙混凝土早期温度场与应力变化规律研究

Study of Early Temperature Field and Stress Variation Law of Concrete on Sidewalls of Subway Stations

为实现对地铁车站侧墙混凝土裂缝的有效控制,通过预埋温度和应力传感器的方法,对侧墙施工过程进行监测,并将实测数据和Midas civil有限元模型的模拟结果进行比较分析,总结侧墙施工过程中温度场和应力场的规律。现场监测和数值分析表明:早期混凝土水化热反应较快,浇筑完成后仅用20 h即达到最大值,夏季温度较高,降温速率较缓慢,约为–0.40℃/h,且中间层降温速率相对较快;压应力达到最大值的时间与温度达到最大值的时间较接近;进入收缩变形阶段,拉应力在出现0应力的临界情况后随温度的继续下降逐渐增大,在浇筑后50h,各测点的拉应力基本趋于稳定;利用有限元模型计算得到的模拟结果与现场监测数据相差较小,验证了方法在预测裂缝产生方面的有效性。研究成果可以为实际工程中的裂缝控制提供参考。

To provide a theoretical basis and reference for crack control during construction,this study first monitored the construction of side walls by embedding temperature and stress sensors.The measured data were then compared with the Midas civil finite element model,the law for a temperature field,and the stress field during the construction of the side walls.The field monitoring and numerical analysis showed that the hydration heat reaction of the concrete in the early stage was relatively fast,reaching its maximum value only 20 h after pouring.The temperature was high in summer,and the cooling rate was relatively slow at approximately-0.40℃/h.However,the cooling rate of the middle layer was relatively fast.The time at which the compressive stress reached its maximum value was close to that at which the temperature reached its maximum value.Subsequently,it entered the shrinkage deformation stage.After the critical condition of zero stress occurred,the tensile stress gradually increased with a continuous decrease in temperature,and the tensile stress at each measuring point tended to be stable 50 h after pouring.The finite element model results were close to the field monitoring data.Thus,it could play a role in the prediction of and theoretical basis for fractures.It could also be used as a reference for actual fracture control in engineering.