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Geomechanics and Engineering
  Volume 11, Number 1, July 2016, pages 141-160

Comparative field tests on uplift behavior of straight-sided and belled shafts in loess under an arid environment
Zeng-zhen Qian, Xian-long Lu, Wen-zhi Yang and Qiang Cui

    This study elucidates the uplift behaviors of the straight-sided and belled shafts. The field uplift load tests were carried out on 18 straight-sided and 15 belled shafts at the three collapsible loess sites under an arid environment on the Loess Plateau in Northwest China. Both the site conditions and the load tests were documented comprehensively. In general, the uplift load.displacement curves of the straight-sided and belled shafts approximately exhibited an initial linear, a curvilinear transition, and a final linear region, but did not provide a well defined peak or asymptotic value of the load, and therefore their uplift resistances should be interpreted from the load test results using an appropriate criterion. Nine representative uplift resistance interpretation criteria were used to define the "interpreted failure load" for each of the load tests, and all of these interpreted uplift resistances were normalized by the failure threshold, TL2, obtained using the L1-L2 method. These load test data were compared statistically and graphically. For the straight-sided and belled shafts, the normalized uplift load.displacement curves were respectively established by the plots that related the mean interpreted uplift resistance ratio against the mean displacement at the corresponding interpreted criteria, and the comparisons of the normalized load.displacement curves were made. Specific recommendations for the designs of uplift belled and straight-sided shafts in the loess were given, in terms of both capacity and displacement.
Key Words
    loess; pullout testing; straight-sided shafts; belled shafts; transmission tower; load test; ultimate load
(1) Zeng-zhen Qian:
School of Engineering and Technology, China University of Geosciences, No. 29 Xueyuan Road, Haidian District, Beijing, 100083, China;
(2) Xian-long Lu, Wen-zhi Yang, Qiang Cui:
China Electric Power Research Institute, No. 15, Xiaoying East Road, Haidian District, Beijing, 100192, China.

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