Trench construction and engineering geology on the Western Front, 1914–18

Trench warfare became associated with the First World War from late 1914. Where possible, British and German trenches were laid out by military engineers in line with the most recent military manuals. The effectiveness of individual trenches was to a large extent controlled by the nature of the ground conditions. Engineering geology had a major part to play in slope stability (because the ideal for trenches was to maintain slopes in an over-steepened condition relative to normal angle of repose) and drainage (because excess surface and ground waters not only weakened trench slopes, but also created untenable conditions for the troops occupying their positions). Recent archaeological investigations in Belgium and northern France provided opportunities to examine slope engineering and drainage solutions for trenches in Paleogene clay–silt sediments and Cretaceous chalk. In Flanders, the failure of slope engineering early in the war led to the creation of A-frames to support slopes at the required batter, with the provision of drainage channels beneath duckboard walkways. In northern France, where frost-shattered chalk was close to the surface, drainage and slope support was less of a problem, although trenches cut through thick Quaternary deposits similarly required imaginative solutions.