| Summary: | 碩士 === 朝陽科技大學 === 營建工程系碩士班 === 89 === A series of triaxial tests have been performed to obtain the parameters need for a sand model, SHSE (A model for strain hardening/softening of dilated sand). The numerical model and FLAC software were carried out to study the uplift behavior of shaft anchors in silty sand of the Taipei Basin. To emphasize the applicability of the numerical model, the results obtained from the field tests are used to verify the results of numerical analyses.
It is found that the friction stress along the fixed anchor end of single anchorage type anchor shows progressive yielding not only tension type but also compression type anchor. Due to progressive yielding, a less than linear behavior is found between anchorage capacity and total anchor length when the latter is longer than 125D, where D is the diameter of fixed anchor end. The progressive yielding could be overcome due to load transfer upward and downward if anchorage body is chosen in midpoint of fixed anchor end for compound type anchor. Therefore, compound type anchor is the best choose among all single anchorage type anchors.
In order to overcome the behavior of progressive yielding, this research develops a multiple anchorage method to dissipate the phenomenon of stress concentration. The optimum anchorage position is evaluated from numerical study herein. A linear relationship is found between anchorage capacity and anchor fixed length when the latter is less than 50m.
It can been seen from parameters study that the relative density of sand could not affect the pullout force of single anchorage type anchor due progressive yielding, but the anchorage capacity of multiple anchorage type anchor could increase linearly with relative density of sand. In addition, the load-displacement behavior computed by numerical programs can give a good prediction not only single anchorage type but also multiple anchorage type of field anchors.
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