A Critical Review of Section 8 (BS 5930)—Soil and Rock Description

Abstract

Abstract BS 5930 proposes fundamental changes to current practice in the description of soils and rocks. The paper reviews these changes and suggests alternative proposals which provide a workable reconciliation between the aims of the new Code and current practical soil and rock description. The main changes made by the Code and the authors' recommendations are: The distinction between fine soil and coarse soil solely on grading is rejected in favour of description according to engineering behaviour. The distinction between silt and clay solely on the basis of the A-line is supplemented with additional terms for borderline cases. Simplification and extension of terminology for description of secondary constituents of mixed soils. Rejection of proposed weathering classification for rocks as inapplicable, in favour of current practice. Clarification of rock nomenclature to conform with geological conventions. The changes to current practice made by BS 5930 are considered to be a retrograde step and could lead to confusion and errors. The paper also considers the process of sample description and attempts to clarify the definition of terms employed in fracture logging of rock core. The paper calls for a revision and reissue of Section 8 of the new Code.