Dynamic stress propagation characteristics and calculation methods for soft soil foundation reinforced by high-speed hydraulic compaction in Yellow River alluvial plain

To investigate the dynamic stress propagation characteristics of soft soil foundation reinforced by high-speed hydraulic compaction in the Yellow River alluvial plain, field compaction tests at three energy levels (70, 110, and 150 kJ) were conducted based on actual projects. The propagation laws of dynamic stress generated by high-speed hydraulic compaction in the vertical and radial directions were clarified by monitoring indicators such as excess pore water pressure in the soil and ground vibration velocity during the compaction process. On this basis, a theoretical calculation method for dynamic stress propagation characteristics was established, and the effective reinforcement range and the vibration influence range of high-speed hydraulic compaction were evaluated. The research results indicate that the vertical propagation of dynamic stress generated by high-speed hydraulic compaction follows an exponential decay pattern, which exhibits a distinct secondary decay trend. However, the transmission exponent is smaller than the theoretical value in elastic statics. The radial propagation of dynamic stress conforms to a negative power function decay pattern, and the dynamic stress value is positively correlated with the rammer area. The effective reinforcement depth of high-speed hydraulic compaction is positively correlated with the rammer weight and drop height, and negatively correlated with the rammer area and soil unit weight. The effective reinforcement depths for 70, 110, and 150 kJ energy levels are 5.8, 6.0, and 6.6 m, respectively. The effective reinforcement radius of high-speed hydraulic compaction is related to the rammer diameter, approximately 1.1 times the rammer diameter. The dominant frequency of ground vibrations induced by high-speed hydraulic compaction ranges from 5 to 30 Hz, which belong to medium-to-low-frequency vibrations. The vibration velocity decays according to the law of a negative power function with the distance from the tamping point to the observation point (tamping detection distance). For general industrial and public buildings, the safe construction distances for 70, 110, and 150 kJ energy levels are 7.2, 7.8, and 8.4 m, respectively. The safety construction distances for residential buildings, vibration-sensitive buildings, etc. should be increased successively with reference to this standard. The research findings can provide theoretical and practical references for the design and construction of high-speed hydraulic compaction.