Abstract: Effective control of the compaction quality of roller compacted concrete (RCC) is an important prerequisite for ensuring the safety and stable operation of dams. This paper formulates an improved stiffness index of RCC dam material, considering its lag phase angle, and presents a new method for measuring the lag phase angle. Then, we develop a comprehensive evaluation method of RCC compaction quality, using an XGBoost algorithm that couples this index, dam material properties, rolling parameters, and frequency domain compaction indexes. The results of case analysis show that the improved stiffness index can better characterize the compaction quality of dam materials. The comprehensive evaluation model has a relatively high accuracy, with a correlation coefficient of determination of 0.86 and an average relative error of 0.47% in compactness calculation against measurements, thus providing a new effective approach to the compaction quality control of RCC dam construction.

Key words: roller compacted concrete dam, compaction quality, stiffness index, lag phase angle, XGBoost algorithm