MODEL TESTS OF PULL-OUT RESISTANCE FOR HELICAL ANCHORS AND BEARING CHARACTERISTIC ANALYSIS IN REMOLDED GRAVEL FOUNDATION

In order to explore the applicability of helical anchor foundation and promote its application in gravel strata, the axial pull-out tests for complete-model and half-model helical anchors in remolded gravel ground were conducted in the laboratory. Based on the test results, the distribution and shape of longitudinal cracks in the gravel, the bearing characteristics of pull-out resistance for helical anchors in gravel and the effects of anchor plates on bearing capacity were analyzed. The bearing mechanisms of pull-out resistance for helical anchors were studied. The results showed that the general shear failure and bearing capacity weakening often occured to anchor plates shallowly emkedded in gravel strata, local shear failure usually occured in the upper soil stratum above anchor plates deeply embeded in gravel strata, which resulted in the deformation to increase continuously. Gravel strata above anchor plates at the initial stage of loading, and the relations between loads and displacement were approximately linear; with the increase of loading, soils above the anchor plates were compressed and sheared, which led to excessive deformation and bearing failure. The more the anchor plates, the deeper the embedment, the larger the bearing capacity of pull-out resistance and the smaller the deformation of the helical anchor. Increasing embedment could play a full role in bearing capacity of pull-out resistance at the stage of small displacement. Therefore, the helical anchors in gravel were a kind of deep foundations, and the interaction between anchor plates and soil was the main factor influcencing bearing capacity.