2 to 1 TO 3 to 1.
Lias clays of doubtful character,
3 to 1 TO 4 to 1.
Superficial beds of London clay,
3 to 1,
and not less for any weak clay.
In embankments, much depends upon the height, mode of tipping, state of the soil when deposited, the protection afforded and uniform character of the mass, the larger it is the more difficult it will be to drain.
Although firm clay may for a short time stand at nearly a vertical slope for any height of face not exceeding about 10 to 12 feet, few clays will permanently stand at a less slope than,
1½ to 1, for moderate heights,
although they may for a time do so at 1 to 1 in unsubmerged work, but if the slope is covered with water, as in a canal, and subject to wash or wave action, however shallow the depth, it is seldom they repose at a less inclination than 1½ to 1.