Lateral Resistance of Piles near Vertical MSE Abutment Walls

Pile foundations for bridges must often resist lateral loads produced by earthquakes and thermal expansion or contraction. In addition, space constraints are also leading to vertical mechanically stabilized earth (MSE) walls at abutment faces. Available test results indicate that lateral pile resistance can decrease significantly as piles are placed closer to MSE walls. However, no design procedure is available for assessing the decrease in resistance or the effect of the reinforcement on lateral resistance. In this study, full-scale tests were conducted on two piles spaced at 3.8 and 7.3 pile diameters behind a 5.9-m high MSE wall with unusually long reinforcement lengths (approx.1.6H). The measured lateral resistance was almost identical for both piles suggesting that extra pull-out resistance can compensate for potential strength losses produced by proximity to the wall. Measured tensile forces were higher in the reinforcements adjacent to the pile closest to the wall indicating that the reinforcing grid was supplying additional resistance to pile movement. Back-analyses using a p-y curve approach in LPILE found the friction angle and k value to be 39° and 217 MN/m³, respectively. This k value is 3.6 times higher than that for piles in sand but comparable to values for gravel from other lateral load tests in gravel.