Comparative Assessment of Dynamic Behavior of Vertical and Batter Pile Groups under Horizontal Excitation

This paper aims to compare the dynamic response of the vertical pile group (VPG) and batter pile group (BPG) subjected to machine-induced-type loading. For this purpose, an experimental investigation is carried out on a 2 x 2 VPG and a 2 x 2 BPG subjected to horizontal excitation for four different eccentric moments (W center dot e = 0.225, 0.885, 1.454, and 1.944 N center dot m) under the static loads (W-s) of 12 and 14 kN. The batter piles in the BPG are inclined at an angle of 20 degrees with the vertical in a unilateral direction. The piles used are 3.3-m-long driven steel pipes with an outer diameter of 0.114 m and thickness of 3 mm and 3d spacing (center to center) between the piles. The comparison in the dynamic behavior of VPG and BPG depends on the dynamic test results, which include the frequency-amplitude response, soil-pile separation length, and distribution of the dynamic bending moment. The test results show that the resonant frequencies of the BPG are higher, whereas the resonant amplitudes are lower when compared with the VPG. Moreover, the influence of the loading direction regarding the batter pile inclination is also evaluated, and the results show the difference in the dynamic behavior as a consequence of unilateral inclination of the batter piles. The soil-pile separation length estimated is less in BPG compared to that in VPG. The result also shows that the magnitude of the maximum dynamic bending moment of BPG is lower than that of VPG. The frequency-amplitude responses from the field tests were compared with the theoretical prediction based on the continuum approach and superposition method. It is found that the theoretical analysis with precise boundary zone parameters predicted the dynamic response of both the pile groups reasonably well in comparison to the dynamic field test results. Furthermore, the study highlights the normalized plots on the effect of pile batter angle and loading direction on the resonant frequency and resonant amplitude based on the theoretical and experimental study.