MECHANICAL PROPERTIES OF ROCKS COMPOSING STEEP SLOPES IN HOKKAIDO, JAPAN

Yoshiaki FUJII, Naoshi MIYASHITA, Yoji ISHIJIMA and Minoru KAWAKITA

ABSTRACT: Fracture toughness as well as uniaxial compressive strength and indirect tensile strength of rocks consisting of steep rock slopes in Hokkaido, Japan were evaluated. The fracture toughness was in the range between 0.02 MPa m^0.5 to 0.4 MPa m^0.5 for hyaloclastites and about 2.6 MPa m^0.5 for a granite. The fracture toughness for Toyohama hyaloclastite decreased by 44% by water presence and decreased by 4.5% and 12.6% with decrease of loading rate by an order under dry and wet condition, respectively. Decrease of strength by weathering was not confirmed for Kinaushi hyaloclastite although more smectite was found in the colored specimen sampled near the ground surface. One of the three samples of Takinosawa hyaloclastite broke in the way of 100 freeze-thaw cycles. One of the two samples of Raikishi hyaloclastite broke during the course of the both 10 and 100 freeze-thaw cycles. No samples of Rubeshibetsu granodiorite broke in the way of the freeze-thaw cycles. Weakening of indirect tensile strength due to freeze-thaw cycle was confirmed for the three rocks although that of fracture toughness was not confirmed.

Key words: unconfined compressive strength, tensile strength, failure brittle value, water content, strain rate, freezing and thawing test  (IGC: F6)