Tangent Modulus Method, Applicability to Three Types of Rock and Influence of Confining Pressure

Fujii, Yoshiyuki; Ohtaka, Norimichi; Nakagawa, Yoshifumi; Kodama, Junichi

doi:10.2473/journalofmmij.124.120

Cited by 1 publication

(2 citation statements)

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“…The results confirmed that the bending point appeared at the preloading stress level in porous rocks, such as Shirahama sandstone (Fig. 2a) and Kimachi sandstone that both date to the Miocene age, and in a Pleistocene Shikotsu welded tuff under dry conditions (Fujii et al, 2003;Fujii et al, 2008). The bending point was discernible although not quite distinctive in a hard and crystalline Inada granite (Fig.…”

Section: Tangent Modulus Methodssupporting

confidence: 73%

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Tangent modulus method – An original method to measure in-situ rock stress

Fujii

Makasi

Kodama

et al. 2018

Tunnelling and Underground Space Technology

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This paper proposed Tangent Modulus Method (TMM) which is an improved oriented core method to determine in-situ rock stresses. In this approach, the cylindrical specimens prepared along different directions from thick core samples were uniaxially compressed twice to a given stress level. The stress value of the bending point in the first loading cycle of the stress-tangent modulus curve is considered as the normal component of the in-situ rock stress along the drilled direction of the specimen. Four types of rocks from soft porous tuff and sandstone to hard crystalline granite was investigated to evaluate the potential of this method. The effects of changes in strain rate, temperature, water content, confining and pore pressure, and stresses larger than the preload on the stress value of the bending point were experimentally investigated on preload specimens to investigate their influence on TMM.Comparison of the stress measurement results by TMM and an overcoring method at AK tunnel in Hokkaido,Japan was also performed to validate the TMM.

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Section: Tangent Modulus Methodssupporting

confidence: 73%

“…The bending point was discernible although not quite distinctive in a hard and crystalline Inada granite (Fig. 2b; Fujii et al, 2008). The strengths of these rocks are shown in Table 1.…”

Section: Tangent Modulus Methodsmentioning

confidence: 90%