Abstract: Gravel-clay mixed with phase change material (GC-PCM) can prevent a core wall from freeze-thaw damage during winter construction. Consequently, it’s necessary to investigate how to efficiently improve the anti-freezing performance of this novel damming material at a low cost. This study develops an optimization method of multiple heating measures for temperature control of the core wall made of GC-PCM during winter construction. First, we formulate respectively two procedures for heating GC-PCM: air circulation for large-scale construction stage, and infrared irradiation for the stage after completion of GC-PCM filled into the core wall; then we establish a multi-objective optimization model for GC-PCM temperature control using these two procedures to minimize the total time and energy consumption. Moreover, detailed steps are given to solve the model using the Non-dominated Sorting Genetic Algorithm-Ⅱ (NSGA-Ⅱ), based on the improved Best/Middle/Worst Ideal Solution-Technique for Order Preference by Similarity to Ideal Solution (BMW-TOPSIS). Case study shows that for GC-PCM at an initial temperature of 4 ℃ under a multi-year average wind speed of 1.8 m/s, the optimal procedures can be adopted: Heating GC-PCM with a hot air blower temperature of 16.5 ℃ and a bottom heat source temperature of 15.6 ℃, and then implementing infrared heating at a moving speed of 0.70 m/s for 2 passes. The optimization method developed in this study lays a theoretical basis for fast selection of GC-PCM heating procedures under multiple condition combinations in practical dam construction.

Key words: gravel-clay, anti-freezing and temperature control, phase change material, air circulation heating, infrared irradiation, multi-objective optimization