| Summary: | 碩士 === 逢甲大學 === 土木工程所 === 93 === The major superiority for a direct shear test device is to determine shear strength for a known planar failure surface. The feature for a traditional small direct shear test device is that samples obtained directly from drilling cores can be utilized. However, since the size of a sample is small enough, the effects for the structures on the failure plane formed during deposition can hardly be included in the test result. Also, during transferring horizontal shear force via the upper and the lower shear boxes, additional moment can be induced such that one end of the upper shear box will be lifted upward. A gap between the upper and the lower shear boxes is then clearly shown. Thereafter, lateral earth pressure near the gap is released thoroughly and some of the sample is forced to flow out through the gap. Such test conditions are seriously deviated from the theoretical ones. For improving the above-mentioned defects for the traditional small direct shear test, the authors of this paper develop a high speed large direct shear test device with double shear planes. The new device can not only take the effects of structure on the sliding plane, but also has the capability to determine the shear strength for a plane sliding quickly during the occurrence of a large earthquake.
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