Acknowledgments

It is recommended this chapter is read in conjunction with

• Chapter 7 Geotechnical risks and their context for the whole project

• Chapter 33 Expansive soils

• Chapter 40 The ground as a hazard

All chapters in this book rely on the guidance in Sections 1 Context and 2 Fundamental principles. A sound knowledge of ground investigation is required for all geotechnical works, as set out in Section 4 Site investigation.

The list below contains definitions for terms used in this chapter. Words presented in italics are themselves defined elsewhere in the list. Further definitions are given in Dictionary of Earth Sciences, edited by M. Allaby, Oxford University Press, 2008.

Air breakage Process of slaking controlled by air pressures produced by the capillary water in the pore spaces of fine-grained, partly saturated rocks.

Anisotropy Term describing the physical property which depends on the direction relative to a defined axis, such as bedding or foliation.

Argillaceous Sediments or sedimentary rocks that are composed predominantly of clay and silt-sized material, comprising significant quantities of clay minerals.

Argillite Compact, strong, fine-grained, clay-rich sedimentary rock which has been strongly lithified by deep burial or low-grade metamorphism, but lacking lamination, fissility or cleavage structures.

Authigenic Mineral that has formed in situ in deposits during progressive diagenesis, resulting from changes in burial and temperature.

Burial diagenesis Diagenesis that occurs due to burial of sediments beneath later sediments.

Cation An atom (or group of atoms) which is deficient in one or more electrons to produce a net positive charge e.g. Al³⁺.

Cation exchange capacity The maximum quantity of cations that may be sorbed onto the surfaces of mineral particles at a given pH value.

Cement Mineral material precipitated in the pore space and interparticle chemical bonds that hold grains together.

Cementation Process by which the grains of geomaterials become attached together by the precipitation of mineral matter between the grains and the formation of interparticle chemical bonds.

Clast A fragment of rock or mineral grain that has been derived by erosional processes from older rock.

Clastic Sediment or sedimentary rock that is composed of (broken) fragments of other rocks and minerals derived by weathering and erosional processes.

Clay grade An average grain size of less than 0.002 mm. Although clay grade material usually contains significant amounts of clay minerals, other material such as quartz, organic matter, sulfides and carbonates may also be present.