Comparative modelling of pull-out process of four different anchorages by using transparent soil

A small-scale physical modelling system is developed to study the pull-out mechanism of embedded soil nails based on transparent soil and particle image velocimetry (PIV). Four types of soil anchorages, common cylindrical anchorage, hand grenade shape anchorage, round bead string shape anchorage and Christmas-tree shape anchorage, are set in the experiment to observe the soil displacement impact areas and load-displacement curve. Then the maximum uplift capacity and the failure mechanism of soil anchorages are discussed. From the results, it is shown that before failure happens, all horizontal displacements of soil anchorages are relatively small compared to vertical displacements, except for the hand grenade shape anchorage. The vertical displacements of the round bead string shape anchorage and Christmas-tree shape anchorage have the larger vertical displacement impact area, and both reach 6.0R. The profiled anchorage can effectively provide 66%~91% more force than the normal cylinder anchorage, and the Christmas-tree shape anchorage has the largest uplift load. The anchorage length and effective radius are directly related with the anchorage pull-out resistance. The maximum uplift capacity happens between the pull-out starting and full failure of the soil-soil anchorage interface. When the soil-anchorage interface begins to fail, failure first occurs at the top of soil anchorage, then develops to the bottom along the soil anchorage body. Take soil anchorage type A for an example, when the failure develops 1/3 of its own length to its bottom, the uplift capacity reaches the peak value.