Tangent Modulus Method, Applicability to Three Types of Rock and Influence of Confining Pressure
Tangent Modulus Method, Applicability to Three Types of Rock and Influence of Confining Pressure
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切线模量法、三类岩石的适用性及围压的影响
DOI：
10.2473/journalofmmij.124.120
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
J. Kodama
中科院分区：
文献类型：
--
作者：
Y. Fujii;Norimichi Ohtaka;Yoshifumi Nakagawa;J. Kodama
将切线模量法应用于七国堆焊凝灰岩、稻田花岗岩和木町砂岩的预压圆柱形试件。阐明了切线模量法可以应用于岩石。对于Shikotsu焊接凝灰岩和稻田花岗岩，预加载持续时间与预加载应力的最大延迟时间呈正相关，误差小于20%；而对于木内砂岩，由于试件数量较少，这种相关性不被证实。根据卡尺确定的最大延迟时间分别为：四方焊接凝灰岩42天，稻田花岗岩21天，木町砂岩28天。三轴预加载木町砂岩单轴循环加载时弯曲点的应力随预压围压的增加而减小。在降低或增加围压的情况下，对木马池砂岩和白滨砂岩进行了三轴预加载和三轴循环加载。白哈马砂岩的弯曲点应力随围压的降低而减小。木池砂岩未见明显变化。在增加围压的情况下，白滨砂岩没有观察到弯曲点。另一方面，木町砂土的弯曲点应力随着围压的增加而减小，基于一个由两个弹簧和一个滑块组成的模型解释了切线模量法中用于检测应力记忆的物理现象。一根弹簧代表岩石的弹性。另一个弹簧和滑块是平行连接的，表示由于不可逆的空隙闭合而没有弹性。该模型较好地模拟了预加载应力作用下切线弹性模量的减小。
The tangent modulus method was applied to pre-loaded cylindrical specimens of Shikotsu welded tuff, Inada granite and Kimachi sandstone. It was clarified that the tangent modulus method could be applied to the rocks. A positive correlation was observed between the preloading duration and the maximum delay time at which the preloaded stress was determined with the error less than 20% for Shikotsu welded tuff and Inada granite although the correlation was not confirmed for Kimachi sandstone due to small number of specimens. The confirmed maximum delay time for each rock was 42 days for Shikotsu welded tuff, 21 days for Inada granite and 28 days for Kimachi sandstone based on clip gage.The stress at bending point in uniaxial cyclic loading for triaxially pre-loaded Kimachi sandstone decreased as confining pressure in the preloading increased. Kimachi sandstone and Shirahama sandstone were triaxially preloaded and triaxially cyclic loaded under decreased or increased confining pressure. The stress at bending point decreased with decrease of confining pressure for Shirahama sandstone. No apparent change was observed for Kimachi sandstone. Bending points were not observed for Shirahama sandstone under increased confining pressure. On the other hand, the stress at bending point decreased with increase of confining pressure for Kimachi sandtsone.The physical phenomena utilized to detect stress memory in tangent modulus method was explained based on a model which consisted of two springs and a slider. One spring represents the elasticity of rock. Another spring and the slider are connected in parallel and represent inelasticity due to irreversible closure of voids. Decrease of tangent modulus at the preloaded stress was well simulated by the model.