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

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.

The characteristics of glacial tills from Northern England derived from a relational database

“…CP 2001:1957 requires the principal soil type to be classified as either cohesive or non-cohesive on the basis of engineering behaviour, whereas under BS 5930:1981 the distinction between the principal soil types is made on the basis of the grading (Norbury et al, 1986). Before 1990 laboratory tests were carried out in accordance to BS 1377:1975, with effective strength testing procedures following standard texts such as Bishop and Henkel (1976) and Head (1982), These tests were subsequently introduced into BS 1377:1990.…”

Seismic refraction surveys for predicting the intensity and depth of weathering and fracturing in granitic masses

“…In fact, the transitional weathering profile, as opposed to corestones, is more commonly observed in granitic masses elsewhere, irrespective of area or climate. Typical examples occur in tropical Ghana (Ruddock 1967), tropical Malaysia (Newbery 1971), sub-tropical Hong Kong (Gamon & Finn 1986, Hencher & Martin 1982, and temperate UK (Norbury et al 1986). …”

The use of the geotechnical database ‘Geoshare’ for site investigation data management

“…The primary objectives are to simplify the structure of the description, reduce the overall number of words and restrict the range of terminology used to the necessary minimum. These objectives are also clearly attractive to the engineering profession for reasons of efficient practice as indicated by Norbury et al (1984) who recommended various amendments to British Standard 5930 section 8 including 'a simplification and extension of terminology for description of secondary constituents in mixed soils'.…”

“…Note that with any necessary additional information added at the end of this scheme, this would provide the basis for a standard description format which is also easily searched for key failures by simple and efficient software routines. Thus the typical format would be [after British Standard 5930 (1981) and Norbury et al (1984), with additions]: strength, bedding, discontinuities, weathering, colour, particle shape, particle composition; sediment modifier(s); main sediment type (with repetition of this sequence for an additional sediment type); additional information. Currently, the potential advantages of such a terminological scheme for the scope of data retrieval from future standardized site investigation project log descriptions are under evaluation by inputting such data into Geoshare.…”