DETERMINATION OF THE STRUCTURAL STABILITY CLASS OF ENGLISH AND WELSH SOILS, USING A WATER COHERENCE TEST

Abstract

Summary The structural stability of samples of 180 soils of known composition was examined by the Emerson test. This test is based on the swelling, slaking, and dispersion behaviour of soil aggregates when immersed in water and under mechanical stress. In the surface soils investigated there appeared to be a critical level of organic matter, corresponding to 2 per cent organic carbon, below which soils were very liable to structural deterioration especially in the absence of calcium carbonate. Exceptions occurred and are discussed in relation to soil composition. A very few soils gave variable or indeterminate results and on these the tests were repeated on larger numbers of aggregates. Most soils were readily classified into one or other of the eight classes recognized by Emerson, and the test is a simple and convenient way of distinguishing soils likely to have structural problems in the field.