Scale model investigation of the effect of vertical load on the lateral response of micropiles in sand

Research regarding the effect of simultaneous axial and lateral (combined) loading on micropile foundations is limited and somewhat conflicting. This paper presents the results of a scale model study completed to assess the impact of an axial (vertical) load on the lateral response of micropiles in sand. A laboratory test pit was filled with fine sand, and the density of the sand was varied from loose to dense. A total of 17 model micropiles were instrumented, installed and tested. This paper presents details regarding testing materials, test design, soil conditions, instrumentation, installation, experimental program, testing results and comparison of testing results to p-y analyses. The results of the study indicated that the lateral deflection was only significantly affected by the introduction of a constant axial load for large lateral loads. However, bending moments in the micropiles were significantly increased for combined load conditions at all magnitudes of lateral load.