An experimental investigation was carried out in the laboratory to study the effect of disturbance on the pullout capacity of ground anchor. To simulate the effect of disturbance due to installation procedure cylindrical volume of loose sand was formed within a homogeneous dense bed of various relative densities. The ratio of depth of anchor to its diameter was varied so as to cover the range for shallow and deep anchors while the width of disturbed zone was varied in proportion to the anchor diameter. Load tests on anchor in homogeneous bed were also carried out to offer a comparison with the disturbed sand beds. Investigation showed that the test results in homogeneous sands beds were consistent with previous theories. For an anchor embedded in a disturbed zone its breakout factor was also dependent on the ratio of depth/diameter of the anchor. The ultimate resistance of this anchor was significantly reduced when the ratio of depth/diameter exceeded 3. However the effect was not apparent when the width of the disturbed zone was equal to or more than three times the anchor diameter.
A review on the available literature on anchor pullout showed that although tests have been carried out on models and atfull scales and various theories have been proposed for design, the role of the zone of disturbance set up installation procedure has not received much attention. From a practical point of view this zone must exist to a greater or lesser extent. To date only Kulhawy (1985) who had laid down tentative guidelines for the evaluation of horizontal stress for backfilled spread anchors. For neat excavation where the diameter of anchor was equal to the width of excavation the strength of either the backfill or the host soil governed the anchor capacity. Table 1 shows the various coefficient of horizontal stress K as proposed by Kulhawy (1985).
