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Okada, S., Izumiya, Y., Iizuka, Y. and Horiuchi, S. (1985) The Estimation of Soft Rock Strength around a Tunnel by Needle Penetration Test. Journal of the Japanese Society of Soil Mechanics and Foundation Engineering, 33, 35-38. (In Japanese)

has been cited by the following article:

• TITLE: Estimate of Uniaxial Compressive Strength of Hydrothermally Altered Soft Rocks Based on Strength Index Tests

  AUTHORS: Masanori Kohno, Hiroyuki Maeda

  KEYWORDS: Uniaxial Compressive Strength (UCS), Irregular Lump Point Load Strength (IPLS) Index, Needle Penetration (NP) Index, Empirical Equation, Hydrothermally Altered Rocks

  JOURNAL NAME: Geomaterials, Vol.8 No.2, April 30, 2018

  ABSTRACT: The purpose of this study was to clarify the relationships between results of index tests and uniaxial compressive strength (UCS) in hydrothermally altered soft rocks of the Upper Miocene, which are typical of the soft rock found in northeastern Hokkaido, Japan. Index tests were performed using point load testing machine and needle penetrometer with irregular lump specimens under forced-dry, forced-wet, and natural-moist states. The relationships between irregular lump point load strength (IPLS) index and UCS, and needle penetration (NP) index and UCS were “UCS = approximately 19 IPLS index” and “UCS = 0.848 (NP index)0.619”, respectively, in soft rocks with a UCS below 25 MPa. These relationships could be applied to on-site tests of rocks with natural moisture content. The UCS could be calculated from IPLS and NP tests on soft rocks only when UCS was below 25 MPa, using the equations obtained as a result of this study.