This chapter on the exploration for and of clay deposits for man’s benefit covers a range of topics. It is essential to comprehend the difference between a clay deposit and a reserve. In order for an exploration programme to provide the information required in an efficient manner, the data collection needs careful planning. This process is best carried out in stages, with the plans for later stages depending on the results of earlier stages. The critical importance of the exploration being led by a qualified geologist who has relevant experience in the type of deposit under study is emphasized. Methods of non-intrusive investigation, used before significant expenditure on field work, are summarized, followed by a review of intrusive methods of investigation. This coverage is brief, not repeating the coverage of exploration techniques covered in most textbooks and Standards on field investigations, for instance Clayton et al. (1988) and BS 5930:1999. The use of geophysical methods to enhance the drilling programme is discussed, again emphasizing the need for competent persons, and sampling programmes and sample types are reviewed. The importance of iterative reporting of the phases of the investigation is threaded through the presentation, as it would be in the development of the assessment of the clay deposit.
The purpose of geological exploration is progressively to build a three-dimensional model of the ground, including the relevant location and characteristics of the mineral strata and the groundwater appropriate to the extraction of the clay mineral. In the context of mineral exploration, the requirement of the investigation process is to establish whether minerals of suitable quantity and quality are economically accessible. Clay strata are widely present as resources but, bearing in mind the generally low value of bulk clay, few of the resources investigated will turn out to be reserves. The combination of overburden removal and storage, and infrastructure factors such as transport logistics can combine to render the economics of a deposit unfavourable. The low unit value of most heavy or structural clays mean that they usually need to be worked and processed close to their point of sale. However, fine ceramic clays for whiteware applications have an intrinsically greater value and the international sales demand can be extensive. Similarly montmorillonite clays such as bentonite (including Fuller’s Earth) are processed and exported to markets around the world.
Figures & Tables
Clay Materials Used in Construction
Concluding the trilogy on geological materials in construction by specially convened Geological Society working parties, this authoritative volume reviews many uses of clays, ranginf from simple fills to manufactured products. Comprehensive and international coverage is achieved by an expert team, including geologists, engineers and architects, who met over six years to produce the book. Packed with information prepared for a wide readership, this unique handbook is also copiously illustrated. The volume is dedicated to the memory of Professor Sir Alec Skempton.
Various definitions of ‘clay’ are explored. Clay mineralogy is described, plust the geological formation of clay deposits and their fundamental materials properties. World and British clay deposits are reviewed. New compositional data are provided for clay informations throughout the British stratigraphic column. Investigate techniques and interpretation are considered, ranging from site exploration to laboratory asessment of composition and engineering performance.
Major civil engineering applications are addressed, including earthworks, earthmoving and specialized roles utilizing clays. Traditional earthen building is included and shown to dominate construction in places. Clay-based construction materials are detailed, including bricks, ceramics and cements. The volume also includes a comprehensive glossary.