A systematic method of soil descriptions

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McLean, J.D. 1976 A systematic method of soil descriptions. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 265 14 p.

Abstract: In order to reduce the subjective nature and widely varying content of most engineering soil descriptions it is proposed that a standard sequence of predefined terms be used. For this purpose a list of applicable terms in a recommended sequence has been produced. The list may appear to be a rather long and complex one but in fact relatively few of the terms are likely to be used in any one description since most are applicable only to a restricted range of soil types. For example, plasticity can only refer to fine-grained (silt/clay) soils and particle shape can only be applied to gravel, cobbles or boulders. Also, some of the terms can be used only in special conditions e.g. bedding and moisture content would normally be estimable only in the examination of in situ material. The Standard Sequence of Terms is presented on page 2. The terms have been derived largely from the USBR ''Earth Manual'' and other standard sources and are defined and explained on pages 3-10. The unified soil classification chart from the ''Earth Manual'' has been reprinted on page 13. Some examples of the soil description method are presented. The soil description is in two separate paragraphs. The first (Main Paragraph) defines the basic soil type and describes the more apparent visual properties of the soil mass. The second (Qualifying Paragraph) gives the in situ conditions of the soil and describes in detail each of the soil fractions present. Therms within the Main Paragraph are separated by commas and those within the Qualifying Paragraph by either semi colons or commas. The whole of the description is written in lower case letters except for the subordinate or dominant fraction terms of the soil name in the Main Paragraph e.g. '......SANDY fine GRAVEL with rare silt......'. A full version of the system is suitable for full formal descriptions as required in detailed borehole records. For the shorter, more specific descriptions employed in a report text, a selectively condensed version is generally preferable. The soil description method was original developed for use on the Waitaki Power Development Schemes. It is now recommended for general use by the Engineering Geology Section, New Zealand Geological Survey. This report is a revised version of an earlier one written in November 1975. (auth)