Evaluation of the group efficiency factor for laterally loaded pile groups

The load transfer mechanism of laterally loaded pile groups is very complicated, and the analysis method is affected by many factors. This paper presents a field test study on lateral responses of large diameter cast-in-place isolated single piles with free head and pile groups with fixed head to investigate the pile group effect. Boreholes are drilled, and relevant field and laboratory tests are carried out to obtain main physical mechanical parameters and the soil profile of the site. Results of lateral loads, lateral displacements and bending moments measured in the field are reported and discussed. A group efficiency factor-based calculation method applicable to laterally loaded pile groups is derived according to a series of full scale and centrifuge tests. An existing group efficiency factor-based calculation method is compared with the proposed method. And three other measured test results are used to verify the calculated results. The comparison results show that the proposed method provides good predictions of load–displacement responses of pile groups.