Series of model tests are performed in calcareous sand retrieved from the Nansha Islands to investigate the axial tension response of monopile. The effects of the relative density of the ground soil and the embedment length of the monopile on the tension response of monopile are studied in detail. The results show that

the pull-out capacity of the model monopile is improved

as expected

by increasing the relative density of the ground soil and the embedment length of the model monopile. Reducing the relative density or embedment length not only reduces its pull-out capacity

but also increases its displacement under a same tension load as on a pile with a larger embedded depth or in a denser ground. As the depth increases

the axial force developed in the model monopile decreases gradually from the maximum value at the top of monopile to zero at the monopile tip. The increase of relative density affects both the magnitude and the distribution of the ultimate frictional resistance between the model monopile and around soil. 0.1 times the diameter of the monopile can be regarded as the critical displacement for the failure of the tension monopile.