Interpretation of uplift load tests on belled piers in Gobi gravel

Belled piers are widely applied in Gobi gravel to withstand axial tensile loads for transmission towers in Northwest China. This study evaluates the pullout performance of belled piers in Gobi gravel. Forty-one full-scale belled piers were installed at seven sites, and pullout load testing was conducted for each foundation. In general, the uplift load - shaft-head displacement curves of the belled piers in Gobi gravel approximately exhibited an initial linear, a curvilinear transition, and a final linear region, and their capacities should be interpreted from the load test results. Four representative uplift interpretation criteria (Chin, slope tangent, tangent intersection, and L-1-L-2) were used to evaluate the capacity of each belled pier. The results were interrelated to establish a generalized correlation among these interpreted capacities using a mean normalized uplift load-displacement curve. Based on these analyses, the relative interrelationships of these criteria were established, and the use of these methods was suggested.