Elucidating the Uplift Behavior of Underreamed Anchor Groups in Sand

Both numerical analyses and model tests were performed to study the interactive behavior of underreamed anchor groups in sand. A constitutive model named SHASOVOD which could simulate the strain hardening-softening and the volume dilatancy of cohesionless soils during shearing, in conjunction with FLAC^3D software to execute the numerical analysis. The results measured from model anchor tests were compared with those calculated by numerical analyses. The load-displacement behaviors calculated numerically consisted with those measured by the tests of the single anchor and the paired anchors. According to the numerical results, the interference induced by the paired anchors is smaller than that induced by the triple anchors. When the spacing between neighboring anchors is small (such as S_h=2D, D is the anchor diameter), yielding zones of soil around each anchor highly superpose, the average capacity of an anchor group is much smaller than the capacity of a single anchor. The superposition of yielding zones decrease with horizontal spacings; the behavior of each anchor in the anchor group tends to a single anchor as the horizontal spacings exceed a threshold value of 10D.