EARTH PRESSURES 333 
EARTH PRESSURES, 
Tenth Interim Report of Committee on Earth Pressures (Mr. F. E. 
WENTWORTH-SHIELDS, O.B.E., Chairman; Dr. J. S. Owens, Secre- 
tary ; Prof. G. Coox, Mr. T. E. N. Farcuer, Prof. A. R. FuLTon, 
Prof. F. C. Lea, Prof. R. V. SoUTHWELL, F.R.S., Dr. R. E. STRADLING, 
C.B., Mr. E. G. Watxer, Mr. J. 5. Witson). 
Since their last report, the Committee have had a meeting at the Building 
Research Station, Garston, at which Dr. Stradling and his staff fully explained 
the work which has been carried out during the past year on soil classification 
and soil mechanics. 
The work is summarised in the attached ‘ Note on Soil Physics,’ which 
was circulated to members of the Committee before the meeting. Briefly, 
it may be said that the work of the Research Station has been to obtain 
samples of soil in an undisturbed condition at various depths and to examine 
their properties such as water content, mechanical analysis, plasticity, 
shrinkage, etc., with the view to classifying them, and also their mechanical 
properties, such as compression and shear strength. 
The Committee feel that investigation of this kind is an important step 
towards the estimation of such properties as the pressure and resistance of 
soils, which they have set out to try to ascertain, and consider it most 
important that this work should be carried on, and that either they or some 
Committee of Engineers should keep in touch with this work, so as to be fully 
acquainted with the results. 
The Committee would, therefore, ask to be reappointed. 
NoTE on Sort Puysics. 
In July 1934, the Committee of Earth Pressures considered two reports 
issued from the Building Research Station, the first by Professor Jenkin on 
©The Mechanics of Granular Materials,’ and the second, which was in 
the nature of an appendix to the first, on ‘ The Experimental Investigations 
of the Mechanics of Clay,’ which described in detail the experimental 
methods developed by Prof. Jenkin. 
Prof. Jenkin’s work was essentially a fundamental investigation into 
the mechanics of granular material and his later work was directed towards 
the investigation of the properties of Kaolin. Although the aspect of the 
investigation has now been changed, advantage is being taken of the experi- 
mental methods and technique which he developed and the valuable ideas 
which he formulated on the dilatancy and compactibility of clays are being 
kept in mind. 
In the present programme of work the method of approach to the problem 
is less of the nature of a fundamental investigation and is inclined more 
towards the practical application of the results of laboratory tests. In 
consequence experiments are not confined to one material, and all types of 
soil as they occur in nature are being examined. The term soil covers 
a wide range of materials which exhibit large variations in their mechanical 
properties. Because of this fact one of the first objects of the work is to 
develop a system of soil classification by means of which soils can be divided 
into broad groups according to their mechanical characteristics. Broadly 
speaking, the mechanical properties of a soil depend upon the following 
factors : 
