JCS Scale Effect on the Self-affine Joints
| Autor: | YuSheng Fan, 范又升 |
|---|---|
| Rok vydání: | 2001 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 89 The mechanical behavior of the rock joints is controlled by three factors: (1) JRC, (2) the quality of the joint materials (such as and JCS), (3) stress environment(such as normal stress). Especially, JCS seriously affects the shear strength under the high level normal stress. JCS is usually estimated byσc, but it will be reduced toσc/4 when the joints are weathering. However, because the shear mechanism of joints are different from that of the unconfined compression failure, whether or not we can replace JCS withσc is the most important part of this thesis, and this is why thesis had a great interest in this topic. Besides, we understand that Bandis’ research tells us both JRC and JCS have scale effect. However, we can not separate these two effects, because we fail to maintain the identical JRC value at different joint size. Hence it is definitely true that separating the JRC and JCS effect about the shear strength. This thesis aims to use the self-affinity concept of the fractal theory to produce the samples of JRC with different sizes. By the result of the experiments on direct shear test, to probe into JCS scale effect. The result has presented in following:(1)At the lower normal stress levels, the shear strength mainly effect by JRC, however, the shear strength effect by JCS at higher stress levels, (2) It is found that the JCS reduces by the joint length increases, (3) In this thesis, JRC (JRC= 8~13) has only limited influence on the scale effect of JCS, (4)JCS can not be directly replaced by unconfined compression strength,σc; the result should be obtained from the direct shear test. (5)When the joint sample length increases, the JCS decreasing will stabilize. Therefore, it is recommended that the size of joint sample should be as long as 10cm, such as 40cm. The field of JCS is to be evaluated through direct shear test. (6) Thesis is based mainly on Barton’s strength model, focusing on the similar to of JCS by means of graph in order to find out the JCS of joints. In this thesis, it could find a formula (This formula apply to 5~40cm joints.)： JCSn=JCS0*(Ln/L0)^-0.5 Ln、JCSn：the length of the longer sample、JCS of the longer sample. L0、JCS0：the length of the shorter sample、JCS of the shorter sample. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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