Hydration Heat Effect and Temperature Control Measures of Long-Span U-Shaped Aqueducts

This study presents a comprehensive analysis of hydration heat-induced temperature and stress fields in a U-shaped aqueduct during the casting phase, integrating field measurements and numerical simulations. The key findings are as follows: (1) Thermal Evolution Characteristics: Both experimental and numerical results demonstrated consistent thermal behavior, characterized by a rapid temperature rise, subsequent rapid cooling, and eventual stabilization near ambient conditions. The peak temperature is observed at the centroid of the bearing section’s base slab, reaching 83.8 °C in field tests and 87.0 °C in simulations. (2) Stress Field Analysis: Numerical modeling reveals critical stress conditions in the outer concrete layers within high-temperature zones. The maximum tensile stress reaches 6.37 MPa, exceeding the allowable value of the tensile strength of the current concrete (1.85 MPa) by 244%, indicating a significant risk of thermal cracking. (3) Temperature Gradient and Cooling Rate Anomalies: Both methodologies identify non-compliance with critical control criteria. Internal-to-surface temperature differentials exceed the 25 °C threshold. Daily cooling rates at monitored locations surpass 2.0 °C/d during the initial 5–6 days of the cooling phase, elevating cracking risks associated with excessive thermal gradients. (4) Mitigation Strategy Proposal: Implementation of a hydration heat control system is recommended; compared to single-layer systems, the proposed mid-depth double-layer steel pipe cooling system (1.2 m/s flow) reduced peak temperature by 23.8 °C and improved cooling efficiency by 28.7%. The optimized water circulation maintained thermal balance between concrete and cooling water, achieving water savings and cost reduction while ensuring structural quality. (5) The cooling system proposed in this paper has certain limitations in terms of applicable environment and construction difficulty. Future research can combine with a BIM system to dynamically control the tube cooling system in real time.