Relation between specimen thickness and side friction of inner wall in constant pressure direct shear box test: Comparison of normally consolidated Kaolin clay and loose Misumi sand specimen
2008
Furuya, T.(National Inst. for Rural Engineering, Tsukuba, Ibaraki (Japan)) | Kawamoto, O. | Yamada, Y. | Nakazato, H. | Inoue, K.
Constant pressure direct shear box tests were conducted on normally consolidated Kaolin clay specimens with various thickness, for three cases of oil smearing to the inner wall of the upper shear box, the upper and lower shear box, and no oil smearing to the inner wall of the shear box. Side friction characteristics between the inner wall of the upper shear box and specimen are discussed on normally consolidated Kaolin clay, comparing to the case of the loose Misumi sand specimen. In case of granular material specimen like dry sand, the normal load of shear plane is close to the load measured by the load-cell on the load receiving plate. However, in case of normally consolidated Kaolin clay specimen, the angle of shearing resistance by the normal load measured on the load receiving plate varies by oil smearing to the inner wall of the upper shear box. This suggests that side friction occurs between the inner wall of the upper shear box and the upper specimen in case of normally consolidated clay. The side friction characteristics at the direct shear box test on normally consolidated clay change delicately depending on the normal load at the test. The side friction of low density specimen at low normal load is apt to increase as the specimen thickness decreases, and the side friction of high density specimen at high normal load is apt to keep constant as the specimen thickness decreases. Therefore, it will be better to adopt the average normal load of the dead and the measured one on the load receiving plate by adjusting the initial lower specimen thickness about equal to the upper one at the peak shear strength.
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