Horizontal Pullout Capacity of a Group of Two Vertical Square Anchors Embedded in Medium Dense Sand

Abstract

In the present study an attempt is made to evaluate the ultimate horizontal pullout capacity of group of two square anchors embedded in medium dense sand by conducting laboratory model tests. The size of the model box used in the present study is 1.2m lengthx0.75m width and 1.5m height. A series of experiments were conducted on single and group of anchors subjected to horizontal pullout load on mild steel square plates of size 10 cm and 15 cm were used .Clean dry local river sand was used in the present study. All the tests were carried out on dry clean sand with a relative density of 55% corresponding to medium dense state. The raining technique was adopted to prepare the sample in the model box to achieve the desired density. In the present study the ratio of H/B is equal to 5 and 6; where H = depth of embedment from top of tank to bottom of lower anchor, B=width of anchor. The parameter S/B is equal to 0,1,2; where S = clear spacing between the anchor, and B= width of anchor. It was found from the present study as H/B ratio increases the pull out capacity increases and also for each H/B ratio as the S/B ratio increases pull out capacity decreases due to decrease in passive resistance. In the present study the group efficiency factor was found which is defined as the ratio pull out capacity of group of anchors to the pull out capacity of single anchor. It was found that the group efficiency factor was found to be greater than 1 and further as S/B ratio increases the group efficiency factor decreases for same H/B ratio. Also as H/B increases the efficiency factor also increases. The anchor breakout factor (Nγ) was also found which tends to increase with increase in depth of embedment and decreases with clear spacing between the anchors. The present data was compared with that of published literature on single anchors and it was found to compare well.