This chapter follows on from the design, planning, performance and use of clay in the construction of fills and in the quarrying of clay as a mineral for use in construction presented in Chapter 10 by considering the practical aspects involved in the excavation, loading, transportation, modification, placement and compaction of clays in construction and mineral extraction projects.
The various operations involved in the excavation, loading, transportation, modification, placement and compaction of materials in or on the ground are termed ‘earthmoving’. The structures that are formed as the result of these operations are known as ‘earthworks’. Some earthworks are constructed to carry out a particular function, such as cuttings and embankments for roads or railways, whereas others, such as quarries and borrow pits, are formed as a consequence of the removal of materials for other uses. Some quarries may be re-used as landfill sites for the disposal of waste materials. In recent times, landfill sites have become engineered structures in their own right and quarries in clay are especially valued owing to the low permeability of the underlying clays, which serve to limit the movement of leachate or liquid wastes away from the site.
In earthmoving practice, clays may be considered as those materials containing predominantly clay- and silt-size materials (i.e. fine-grained soils); however they also include materials that contain sufficient fine material that cause them to behave as fined-grained soils and weak rocks, including clayey sands, glacial till and some highly to completely weathered rocks. They may vary considerably in strength from slurries to weak rocks, such as mudstone and weathered slate. In this chapter, all these materials are referred to as ‘clays’. In addition, many projects involving earthmoving in clays will also involve earthmoving in other materials that lie close to or that must be excavated in order to gain access to clays. Few items of earthmoving plant have been specifically developed for use in clays and most may be used in a variety of materials and circumstances.
Figures & Tables
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.