3-D finite element investigation of discrete deadman anchor for earth retaining wall

In the past several years, considerable attention has been given to the ultimate horizontal pull-out resistance of vertical deadman anchors, which are usually used together with earth retaining wall. Unfortunately, no significant effort has been made to understand/study the behaviour of discrete deadman anchor in earth retaining wall (anchored wall) subjected to the deflection of earth retaining wall. Therefore, this research aims to fill up this gap. The study on the behaviour of single-plate discrete deadman anchor in anchored wall subjected to the deflection of earth retaining wall is carried out by three-dimensional (3-D) finite element analysis adopting finite element software named PLAXIS. The behaviour of discrete deadman anchor is studied by investigating the effects of several key factors. These include the effects of length of tie rod, embedment depth of anchor, spacing between deadman anchors, friction angle of soil, depth of anchored wall, and stiffness of anchored wall. Practicing geotechnical engineers are able to understand the interactions among soil-anchor-wall by studying the effects of several key factors on the behaviour of discrete deadman anchor. This allows practicing geotechnical engineers to determine the potential failure mechanisms and hence provide the most suitable design of anchored wall in geotechnical engineering. Furthermore, the effects of abovementioned key factors are summarised and design charts are proposed for the preliminary design of anchored wall. The design charts are developed based on limiting the wall deflection to 0.5% of excavation height. The major contribution of this research is the development of design charts for the preliminary design of anchored wall. These design charts may be implemented during early design stages, which serves the purpose for earthwork planning, cost estimation, bill of quantity and others. These design charts are set as a guideline for the preliminary design. Last by not least, the embedment depth of deadman anchor in this research is studied up to 3.0m deep. Deadman anchorage system embedded deeper than 3.0m from ground surface is considered to be impractical due to the difficulty in installation and increase of construction cost and time