Selection of tamping parameters based on propagation model of dynamic compaction-induced stress wave

The selection of tamping parameters can be the vital procedure for economic efficiency and ground reinforcement effect of dynamic compaction treatment. At present, stop-tamping criterion and parameters adjustment mostly depended on in-situ test result of dynamic compaction. In this study, a one-dimensional stress wave propagation model with non-radial plane emission was developed; the distribution of wavefront stress along soil depth under single tamping was derived; the mechanism of three independent energy-consuming factors, including compression deformation of foundation soil, lateral diffusion of shear wave and soil damping, were revealed; and classification standard for ground reinforcement depth (GRD) was proposed based on the rule of stress attenuation, which was then used to characterize stress wave propagation and energy dissipation process. Research results indicate that GRD can be notably increased as static ground pressure increase from 40.8 kPa to 122.3 kPa, while excessive increase of drop height and tamper radius has limited influence on GRD under equivalent static ground pressure conditions. Parameters combination of dynamic compaction characterized by heavier-tamper and lower-drop height, can be more beneficial to stress wave propagation deeper. Time-history curves of stress wave show various characteristics at different depths, including shock reinforcement, vibration compaction and elastic vibration. The shock reinforcement depth can be estimated by using the result of ground area enveloped by 5% volumetric strain isogram. The theoretical solution under single tamping is modified by using arbitrary Lagrange-Euler method-based simulation results, then calculation procedure of GRD under continuous tamping can be derived. Therefore, dynamic compaction parameters can be optimized through comparison with in-situ test results so as to improve construction efficiency and economy.