GB540527A - Improvements in or relating to the measurement of resistance to lateral displacementof soils - Google Patents

Abstract

540,527. Testing soil resistance to displacement. PIMM, G. B. R. March 13, 1940, No. 4754. [Class 106 (ii)] In forming foundations for structures the resistance of the soil to lateral displacement is tested by measuring the resistance to driving of two test piles, one being parallel or of constant diameter and the other of taper form, having its lower diameter equal to that of the first. In a modification, two piles of different tapers are used in conjunction with the parallel pile. The parallel pile, Fig. 1, may comprise an outer tube and an inner mandrel with a shoulder at the lower end of the same diameter as the outside of the tube. The forces opposing driving comprise a direct resistance 3 acting on the lower end, and the frictional resistance 7, the earth pressure 4 having no vertical component. The resistance 3 is measured by first driving the mandrel, and the frictional resistance 7 by then driving the outer tube. In the case of the tapered pile, Fig. 2, the resistance to driving comprises the end resistance 3, the frictional resistance 8, which is greater than 7 on account of the tapered form of the pile, and the vertical component of the resistance 5 due to the displacement of the ground. The frictional resistance 8 may be calculated with sufficient accuracy from the measured resistance 7 of the parallel pile, and hence the resistance 5 found. Alternatively, the frictional resistances 7 and 8 may be found by measuring the torque necessary to rotate the piles after driving. When two tapered piles are used, blows of the same energy are used to drive all three piles, and the sets are measured. From the facts that the energy expended in each case on overcoming the 'friction is proportional to the set, the energy expended in displacement of the soil in the case of the two tapered piles is proportional to the volumetric displacements, whilst the common end resistance 3 of the piles is known, the displacement resistance may be calculated.