A set of test devices were developed

and a series of full-scale uplift tests were carried out on a pipe segment buried in lumpy soft clay backfill. Focusing on the influence of shear strength of soil

depth-diameter ratio and loading mode

the pile-soil interaction

the failure mode and the uplift resistance were studied. The test results show that the deformation properties of lumpy soft clay backfill are different from uniform soft clay during uplifting. For the former

deformation is due to the position shift of soft clay blocks and the outflow of water in gaps between the blocks. For the latter

it is due to consolidation. When the depth-diameter ratio is equal to 1

the failure mode of lumpy soft clay backfill is more closed to ‘local’ flow-round. It is much less than DNV’s suggestion which is 3. It was suitable to use Palmer’s approach to calculate the uplift resistance of lumpy soft clay under long-term load if 1. The uplift resistance of pipeline in lumpy soft clay increases as the increase of and it is mainly linear increase with the increase of the shear strength. The consolidation rate of lumpy soft clay is much larger than uniform soft clay

so it may be taken into account of the effect of strength restoration of clay to the uplift resistance during design.