Achieving a high degree of compaction in coarse-grained soils is a critical requirement for ensuring the stability, safety, and long-term performance of earth dams. This study presents the results of comprehensive laboratory and field investigations aimed at identifying the optimal technological parameters for compaction of coarse-grained soils used in hydraulic embankment construction. The influence of grain-size distribution, fine fraction content, and compacted layer thickness on the achieved dry density was systematically investigated. Laboratory experiments were performed using the standard Soyuzdornii compaction apparatus and a vibration compaction device with a cylindrical mold of 300 mm in diameter. Field investigations were conducted at an experimental test site using a 27-ton SANY vibratory roller with compacted layer thicknesses of 50, 70, and 80 cm. The experimental results demonstrated that the highest dry density was achieved for a compacted layer thickness of 50 cm, whereas increasing the layer thickness reduced compaction efficiency due to the limited transmission of vibratory energy throughout the embankment. Furthermore, the proposed grain-size modelling approach was validated by comparing laboratory and field test results, confirming its applicability for reproducing the mechanical behaviour of natural coarse-grained soils under controlled laboratory conditions. The findings provide practical recommendations for selecting rational compaction parameters and can be applied in the design and construction of earth-filled hydraulic structures to improve embankment quality, structural reliability, and long-term operational performance.