| Abstrakt: |
Cyclic simple shear testing is considered to be one of the most appropriate ways of reproducing in the laboratory the stresses that would be experienced by an element of soil in level ground subjected to earthquake loading. In the last few years cyclic simple shear testing has been analyzed experimentally and theoretically, and the advantages and limitations of the test presented. The main drawback concerns the lack of complementary shear stresses on the specimen vertical boundary and thereby a selection of the proper specimen size, that is, proper diameter versus height ratio must be carefully considered. The nonuniformity of the strain and stresses in the specimen most likely increases as the specimen diameter versus height ratio decreases. To investigate the specimen size effect on the primary dynamic (cyclic) soil properties, namely, the shear modulus and damping, a large-scale simple shear apparatus was constructed. In it, specimens having diameters from 7.6 to 30.5 cm (3 to 12 in.) and heights from 0.64 to 10.2 cm (¼ to 4 in.) could be tested. Thus a wide range of diameter to height ratios could be obtained. The new testing device, its control system, and the method of preparation and installation of the soil specimens for such a large-scale device are presented and discussed. In addition, a cyclic testing program was conducted on sand and some examples of the data obtained are presented as well. |
