Assessment of Load Transfer Mechanism of Compression Anchor Using Finite Element Analysis

Abstract

Ground anchors are mainly used for excavation works of earth retaining wall. According to the load transfer methods, ground anchors are divided into pressure type anchor, friction type anchor and hybrid anchor. Friction type anchor resists the pull-out load by skin friction between grout and soil, and friction type anchors are separated the tension anchor and compression anchor. Compression anchor has benefits comparing to the tension anchor. For the tension anchor, tensile failure can occur on the grout material and tensile failure leads to progressive failure of ground anchor, but it is not for the compression anchor. And steel tendons at the tension anchor cannot be removed after excavation works, while steel tendons at the compression anchor are removable. Therefore, removable compression anchor is used widely in the urban excavation works. However, researches on the compression anchor are insufficient compared to tension anchor and even when designing compression anchor, design methods for tension anchor are used recently. Furthermore, compression anchors are divided into load concentrative compression anchor which has single anchorbody and load distributive compression anchor which has multi anchorbodies. Depending on the number and spacing of anchorbodies, load distributive compression anchor has complex load transfer mechanism and it is hard to predict load transfer mechanism of load distributive compression anchor. In this study, general purpose finite element analysis program 'Midas GTS NX' is used to evaluate the load transfer mechanism of compression anchor. Reliability of the FEM techniques which are applied to this study is secured through a comparative analysis of the existing studies carried out for the tension anchor, compression anchor and load distributive compression anchor. Load distributive compression anchors which are anchored on weathered soil, weathered rock and soft rock are simulated and spacing of anchorbodies varies 1 m to 2 m for evaluating load transfer mechanism of the compression anchor.