Experimental Study on the Pull-Out Performance of Strip Plate Anchors in Sand

In this study, the uplift behavior of strip plate anchor embedded in loose, medium-dense and dense sand is investigated by experimental model tests in 1-G condition. The width of the model plate anchor varies from 50 mm to 400 mm and the embedded depth varies from one time of plate width to 12 times. The densities of the dry sands are 1.65g/cm³, 1.73g/cm³, 1.85g/cm³ (relative density, D_r, as 30%, 55%, 80%) with the angle of friction, φ, of 34°, 38° and 43°, respectively. In medium dense and dense sand, the load-displacement curves are different from that in loose sand, which shows a rapid increase to reach to peak pullout capacity and starts decreasing gradually until the pullout capacity reach its steady state. At the steady state some specimens showed some fluctuations in the pullout capacity values at large displacements. The Particle Image Velocimetry (PIV) technology is employed to capture the failure mechanism of the sand. The failure mechanism in medium dense and dense sand at the peak resistance clearly shows an inverted trapezoidal shape with a projecting angle of around 2ψ (dilatancy angle). During the softening stage, gradually shrinking of the mobilized sand was observed. Finally, the shear band in the soil developed nearly vertically when the resistance reached the residual value. However, a vertical slip failure is observed for shallow anchors in loose sand during the whole process of anchor uplifting, in which the slip surfaces extend from the edges of the anchor to the soil surface. No obvious shear band was observed around the anchor when the anchor embedment ratio is large than 7. The effect of relative depth (depth/width) and width of anchor are discussed. In the range of this study, the model scale has minor effect on the normalized breakout factor. The breakout factors given by the experimental tests agree well with the predictions by the equation of Meyerhof and Adams (1968).