Investigation Of Several Variables Involved In Laboratory Shear Testing Of Soils PDF Download

Investigations of shearing strengths of the soils from the site of a model flood-wall in the vicinity of Cincinnati, Ohio, were made in 1949 in the Soil Mechanics Laboratory of the Massachusetts Institute of Technology. This investigation was carried out under the supervision of the author, for the Ohio River Division of the Corps of Engineers, Department of the Army. Certain testing procedures that have not previously been published were used in this program, the most important being multiple-stage tests for determining the effect of applied pressure on partially saturated soil, and the aim of this paper is to outline the more important steps of the shear investigations of this project. The shear tests of this investigation were triaxial tests on samples 2.8 in. in diameter and about 6.5 in. in length, conducted at an essentially constant speed of axial compression, with no changes of water content permitted during shear and with pore-water pressures measured throughout all tests. This testing method has been accepted for several years as a standard procedure in the M. I. T. laboratory, and for testing details reference is made to other reports (1). The soil was a silty-clay of low plasticity. Undisturbed samples were taken from a test pit by the Ohio River Division laboratory staff at the seven depths shown in Fig. 1. The Atterberg limit and natural water content data at the left in this figure indicate that the nature of the soil does not vary with depth to any great degree, but the other curves show that the maximum past pressure (sometimes called the preconsolidation pressure) varies considerably with depth, and that the degree of saturation varies from about 90 per cent at the shallower depths to 100 per cent at the larger depths. Thus it is seen that the shearing strength must be recognized to be a function of depth.