BEHAVIOUR OF OBLIQUELY LOADED FOOTING RESTING ON PLY SOIL

Abstract

Three dimensional tests were performed on a square (150mm x 150mm) surface footing resting on ply soil (RDFS), and subjected to central oblique load Tests were performed on poorly graded sand (SP, Dio=0.176mm, CD=1.545, Cc=1.105) placed in a tank of size 1000mm X1000mm X450mm deep at relative density of 60%. The sand was reinforced by polypropylene fibres of 20 denier and 60mm length. The fibres were randomly mixed in dry sand. The mix is designated as 'Randomly Distributed Fibre Reinforced Sand' or `RDFS' or 'Ply Soil' In all ninety tests were conducted The depth below the base of footing up to which the RDFS was placed is termed as relative depth of reinforcement (RD), and it was varied up to significant depth (SD). For square footings the significant depth is taken as 2.0B, B being width of footing. The fibre contents were taken (0.5%, 1.0%, 1.5% and 2.0%) by weight of dry soil. Tests were performed for load inclinations of 0°, 5°, 10°, 15°, 20°. In each test, for every increment of load, settlement and horizontal displacement were measured, and plots were made for pressure versus settlement and pressure versus horizontal displacement. During the tests, it was observed that placement of RDFS at 60% relative density requires more effort than the placement of unreinforced sand at the same relative density. Keeping this in view, two series of tests were performed, namely, (i) placement of RDFS with same compactive energy as required placing the unreinforced sand at 60% relative density, and (ii) placement of RDFS at 60% relative density. The test data has been interpreted to study the effect of (i) relative depth RD, (ii) fibre content, Fe and (iii) amount of compactive energy on bearing capacity, settlement and horizontal displacement of footing subjected to central inclined load.