Abstract: The existing expansive rock identification index parameters can be classified into three types: rock material indices, rock powder material indices and comprehensive indices. The essential differences between the expansive soil and expansive rock are the history in the deposition of expansive rock. Therefore, the effect of cementation in the deposition of expansive rock should be considered as the index parameter of the expansive rock identification. Based on the thorough understanding of both advantages and disadvantages of the rock material indices and rock powder indices methods, this paper presents a new set of expansive rock identification index parameters, free expansion ratio and dry rock saturation moisture content, for the engineering application. For large engineer application, the conventional parameters such as, expansive force, and expansive ratio, should be references for the reliable expansive rock classification result. The paper also presents the identification results for the expansive rock samples in a high-speed rail project. The results indicate that the recommended expansive rock identification index parameters are reliable in the expansive rock classification.

Key words: expansive rock, determination methods, classification criteria