On Uniaxial Compression Test of Rock-Like Materials Using a New Type of High Stiff Testing Machine

Abstract

In planning construction of underground structures, it is important to carry out stability analysis of rock masses which requires precise properties of fractured rocks.
In this paper, an experimental study of rock-like materials by uniaxial compression tests using a new type of high stiff loading machine is presented. Four kinds of rocks were selected, namely, Oya-stone (green tuff), Kobe-tuff, cement mortar and marble stone. Three different loading procedures were employed, i. e., static loading, incrementally cyclic loading and cyclic loading in the post-failure region (see Fig. 3).
The machine used in the experiments has high stiffness of about 310ton/mm, and is capable of controlling either deformation or load of the specimen by mechanical action of the wedges under steel blocks installed in parallel with a specimen. This loading machine is very practical and efficient to obtain a complete stress-strain curve of geologic materials.
The main results obtained are summarized as follows:
(1) The stress-strain curves obtained could be divided into four characteristic regions in the progress of fracturing, namely, the intact, crack, fracture, and flow regions. The strains corresponding to each region were related to the strength, or the fablic of materials.
(2) Tests of incrementally cyclic loading showed that the envelop of unloading and reloading curve was coincident with the statical loading curve.
(3) The relationship between the plastic strain and the total strain on incrementally cyclic loading was representable by Weibull's probability.
(4) Fatigue life under cyclic loading in post-failure region was influenced significantly by crypto-damage due to the initial loading and the applied stress level.