Uplift Capacity Factor Research Articles

Vertical Uplift Capacity of Horizontal Anchors

The method of characteristics coupled with a log-spiral failure surface was used to develop a theory for vertical uplift capacity of shallow horizontal strip anchors in a general c-phi soil. Uplift-capacity factors F(c), F(q) and F(gamma), for the effects of cohesion, surcharge, and density, respectively, have been established as functions of embedment ratio lambda and angle of friction phi. The extent of the failure surface at the ground has also been determined. Comparisons made with existing test results support the predictive capability of the theory, and comparisons with the analysis proposed by Meyerhof and Adams show the proposed analysis provides slightly more conservative predictions of pullout capacity.

Experimental and theoretical studies on installation torque of screw anchors

Experimental and theoretical studies on the torque required to install screw anchors in sand are presented. Tests were conducted on five models of screw anchors with different geometry to study the effect of the shape of the screw element on the performance of the anchor during installation. Anchors were installed into prepared layers of dense, medium, and loose sand. An experimental setup was instrumented to allow the measurement of the total pullout load, the upward displacement, the sand surface deflection, installation torque value, and the stress development in the sand layer during all phases of the testing procedure. Special tests were conducted on coloured-layered sand to examine the effect of the installation procedure on the sand deposit and to define the sand wedge involved in resisting the installation of the screw anchor. Based on the results of the experimental investigation, the factors affecting the value of the installation torque were identified. A theoretical model was developed, from which the required installation torque value can be predicted. A torque factor was established in terms of the parameters affecting the torque value, and a correlation between this factor and the uplift capacity factor was proposed. From this correlation, the uplift capacity of a screw anchor can be determined from the measured installation torque value. A comparison between theoretical and experimental results showed good agreement. Also, reasonable agreement was observed when the present theoretical results were compared with the available field results from other investigations. Key words: anchorages, anchors, bearing capacity, helical anchors, models, sand, screw anchors, screw helical anchors, soil mechanics, torque, uplift capacity.