Large-Scale Plane Strain Compression Tests on Compacted Gravel

Abstract

This paper describes the results from a series of monotonic plane strain compression tests on large-scale prismatic specimens of compacted gravel under drained condition. The purpose of this study was to investigate the effect of compaction on strength and deformation properties. Specimens were rectangular prismatic with dimensions of 50 cm high and 22 cm times 25 cm in cross-section. To obtain highly dense specimens, compaction was made by impact loading operated either manually or by employing a motor driven system. Because of having large-size particles (Dmax = 38 mm) in gravel material, a special compaction mould was prepared to compact gravel up to a maximum compaction energy of 8685 kJ/m3 . All compacted soil specimens, after finishing at the top surface, were used for plane strain tests. In these tests, the vertical stress was measured by a load cell located just above the top cap inside the triaxial cell. Deformations were measured not only by using external measurement but also with the help of local deformation transducers (LDTs) set on the sides of the specimen. This was done to avoid the effects of membrane penetration at the side surface of the specimen and of bedding error at the top and bottom ends of the specimen on the measured strains. The study revealed that the intermediate principle strain ε2, measured locally with the help of horizontal local deformation transducers (HLDTs) was not zero even though the confining plates were fixed. Secondly, a relationship was developed between dry density and peak strength on the one hand and compaction energy and peak strength on the other hand under plane strain condition. Fin