Davis, Birch & Chandler raise a number of points which I shall deal with in order of importance:
(1) They state that, “they see no reason to depart from the B.S. procedures for index [plasticity] tests on Keuper Marl”, and elsewhere they quote a sentence of my paper out of context which may leave the reader with the impression that I think that B.S. plasticity test results on Keuper Marl soils give anomalous results.
In fact, I fully agree that there is no reason to depart from B.S. procedure for the plasticity tests on Keuper Marl; I have never suggested otherwise, either in my paper or elsewhere.
My paper shows that the aggregations of particles in Keuper Marl are broken down by the mixing procedure specified in B.S. 1377 (i.e. 10 minutes' working with palette knives on a glass plate) and that consequently the results obtained are the ultimate values. Evidence for the B.S. results being the ultimate values is provided by:
(a) Table 3 of my paper which shows that the liquid limit reaches its ultimate value after ten minutes' mixing;
(b) the fact that the plasticity data obtained by B.S. procedure correlates well with the clay content obtained by mineralogical analysis (Fig. 2 of my paper);
(c) the correlations between liquid limit and other soil properties listed in the fifth paragraph of the comments of Davis et al.
(2) Figure 1 of the comments by Davis et al. shows that for the particular marl studied by