Kj. Northmore et al., THE ENGINEERING PROPERTIES AND BEHAVIOR OF THE BRICKEARTH OF SOUTH ESSEX, Quarterly Journal of Engineering Geology, 29, 1996, pp. 147-161
Brickearth occurs in south Essex where it overlies Quaternary terrace
gravels and London Clay of Eocene age. In places it is as much as 8 m
in thickness. Quartz is the most abundant mineral and feldspar occurre
d in most specimens examined. Of the clay-type minerals, mica is gener
ally more abundant than montmorillonite which, in turn, is more abunda
nt than kaolinite. Calcium carbonate occurs as grains, concretionary n
odules and thin tube fillings. The moisture content normally varies be
tween 12 and 25% and the soils are of low to high plasticity. Clayey,
silty and sandy brickearths are recognized, with most belonging to the
silty variety. They are uniform to well sorted with most samples havi
ng a positive skewness. The porosity of the brickearths is around 40%
with a mean dry density of 1.68 Mg/m(3). Brickearth can have a collaps
ible fabric. In the case of the brickearths from south Essex this was
assessed in terms of collapse indices and the oedometer test. About ha
lf the samples tested in the oedometer were metastable. As would be ex
pected, the degree of compressibility of these brickearths is high. Th
e undrained shear strength of these brickearths showed that they range
d from very soft to very stiff. There is a general tendency for shear
strength to decrease with depth as the soil near the ground surface ha
s a 'crust-like' nature.