Engineering analysis of dynamic behavior of micropile systems

A series of centrifugal tests was conducted on micropile groups and network systems to investigate the system response to earthquake loading and the superstructure soil-micropile interaction behavior. Model tests on vertical and batter micropile systems embedded in loose to medium-dry sand under different levels of shaking are described. Group and network effects were investigated for different configurations and at different levels of loading. The experimental test results were analyzed parametrically to study the effect of the main controlling parameters. For the model testing conditions, the experimental and parametric results indicated a positive group effect increasing with the number of piles and the batter angle. Dynamic p-y curves were found to be nonlinear with low damping and to be much softer than the published data. For inclinations of 10° and 30°, a substantial improvement is observed in the superstructure response with acceleration reduction to 40 percent of the values obtained in the case of vertical piles. The computer programs LPILE and GROUP were used in a pseudostatic analysis approach to simulate the representative centrifugal model tests. Comparisons between the method predictions and the experimental results illustrate that these methods could be used as engineering tools to assess the seismic behavior of micropile groups and network systems.