50 th IGC 50 th INDIAN GEOTECHNICAL CONFERENCE 17 th – 19 th DECEMBER 2015, Pune, Maharashtra, India Venue: College of Engineering (Estd. 1854), Pune, India PULLOUT CAPACITY OF MODEL PILE GROUP ANCHORS EMBEDDED IN COHESSION LESS SOIL Amit Kotal 1 , Ashok Kumar Khan 2 ABSTRACT When the structures are constructed below the ground water table or if they are constructed under the water uplift forces are to be applied on the basement of the structures. In case of transmission towers, mooring systems for ocean surface or submerged platforms, tall chimneys, jetty structures transmit not only heavy compressive loads but also subjected to considerable amount of uplift forces. These structures need footings, which can anchor these with the strata. Under-reamed piles and anchor piles are being extensively used in such cases depending on the in situ conditions. In the present investigation therefore the uplift capacity of pile anchor and pile group anchors in homogeneous soil has been studied. The various parameters such as length of the pile, shaft width, base width of piles have been changed to bring out the effect of these parameters . A large scale of experimental investigations on model single pile anchor and pile group anchors of solid wooden pile having diameter of 40 mm diameter and 600 mm length have been carried out in a model tank of size (850mm x700mm x750mm) and subjected to pullout loads were conducted on poorly graded ‘kharkai’ river sand (specific gravity G = 2.63 and coefficient of uniformity = 1.75) obtained from Jamshedpur, India. Different widths (B = 80mm and 120 mm) and thickness 12 mm of anchor plate was provided. The pile anchors were kept at 3/4 th of total length of pile in medium dense condition of sand. Pile group anchors of 2x2 configuration of different embedment length to shaft width ratios L/d = 11, L/d = 08 and L/d = 06, and enlarged base width to shaft width ratios B/d = 1, 2, 3 and varying center to center spacing of pile anchors in the groups as3d, 4d, 5d were used. All types of piles and pile groups were tested under vertical uplift loading. The load displacement response, ultimate resistance and variation of group efficiency with L/d, B/d and spacing have been studied quantitatively. The analytical model of limit equilibrium method has been proposed to predict the net uplift capacity of pile group anchors. The predicted analytical results were compared with experimental results and other previous researchers work. It was found reasonably good agreement with the experimental and other results. 1 Kotal_Author1, Civil Engineering Department, NIT Jamshedpur, M.Tech Student, India, amit.kotal18@gmail.com 2 Khan_Author2, Civil Engineering Department, NIT Jamshedpur , Professor, India, akk.nitjsr@gmail.com