Compacting Effect Study on the Treatment of Collapsible Loess Foundation by the SDDC Method: Numerical and Experimental Analysis

ABSTRACT An optimal design scheme is developed for treating collapsible loess foundation by the super down‐hole dynamic compaction method (SDDC) in terms of the loess foundation treatment project. This method involves the application of high‐energy impacts to the soil to achieve a compacting effect (CE), which is defined as the measurable improvement in soil density and reduction in its collapsibility. The compaction effect of loess particles and different SDDC parameters on collapsible loess foundation is simulated by the discrete element method (DEM) based on particle flow PFC software, and the optimization scheme is verified by field test data. The results indicates that the SDDC method is more effective for the foundation with uniform soil particle distribution with fine particle size, while the influence of initial porosity, shear modulus, and Poisson's ratio of soil on foundation CE is not significant. For a single pile, the CE of the foundation can be improved by increasing the compaction energy and the diameter of the hammer head, increasing the compaction energy, and reducing the diameter of the drill hole and the distance between piles. The CE performance of an olivary hammer is better than a pointed hammer. Finally, the design parameters of the SDDC construction method in this site are determined as follows: The down‐hole diameter D 0 = 1.2 m, pile spacing L = 2.8–3.2 m, and olivary hammer construction was adopted.