TRANSACTIONS

Paper No. 1174

Pressure, resistance, and stability of earth.[A]

By J.C.  Meem, M. Am.  Soc.  C. E.

With discussion by Messrs.  T. Kennard Thomson, Charles E. Gregory, Francis W. Perry, E.P.  Goodrich, Francis L. Pruyn, Frank H. Carter, and J.C.  Meem.

In the final discussion of the writer’s paper, “The Bracing of Trenches and Tunnels, With Practical Formulas for Earth Pressures,"[B] certain minor experiments were noted in connection with the arching properties of sand.  In the present paper it is proposed to take up again the question of earth pressures, but in more detail, and to note some further experiments and deductions therefrom, and also to consider the resistance and stability of earth as applied to piling and foundations, and the pressure on and buoyancy of subaqueous structures in soft ground.

In order to make this paper complete in itself, it will be necessary, in some instances, to include in substance some of the matter of the former paper, and indulgence is asked from those readers who may note this fact.

[Illustration:  Fig. 1.  Sections of box-Frame for sand-arch experiment]

Experiment No. 1.—­As the sand-box experiments described in the former paper were on a small scale, exception might be taken to them, and therefore the writer has made this experiment on a scale sufficiently large to be much more conclusive.  As shown in Fig. 1, wooden abutments, 3 ft. wide, 3 ft. apart, and about 1 ft. high, were built and filled solidly with sand.  Wooden walls, 3 ft. apart and 4 ft. high, were then built crossing the abutments, and solidly cleated and braced frames were placed across their ends about 2 ft. back of each abutment.  A false bottom, made to slide freely up and down between the abutments, and projecting slightly beyond the walls on each side, was then blocked up snugly to the bottom edges of the sides, thus obtaining a box 3 by 4 by 7 ft., the last dimension not being important.  Bolts, 44 in. long, with long threads, were run up through the false bottom and through 6 by 15 by 2-in. pine washers to nuts on the top.  The box was filled with ordinary coarse sand from the trench, the sand being compacted as thoroughly as possible.  The ends were tightened down on the washers, which in turn bore on the compacted sand.  The blocking was then knocked out from under the false bottom, and the following was noted: