Download Free Shear Strength Of Partially Saturated Soils Book in PDF and EPUB Free Download. You can read online Shear Strength Of Partially Saturated Soils and write the review.

The shear strength and volume change behavior of a partially saturated cohesive soil is assessed as a function of the degree of saturation. All samples consisted of an 80 percent ground quartz - 20 per cent kaolinite mixture compacted dry of optimum water content. Special shear and compression equipment were developed to enable measurements of total volume, water content, total stress, pore air pressure and pore water pressure simultaneous ly. The test data showed that the effective stress equation s s - ua x(ua - uw) wherein x should vary between 0 and 1.0 for degrees of saturation between 0 and 100 percent was inconsis tent on two counts: (1) The shear tests at maxi mum stress difference yielded x values greater than unity (1.01 to 1.36) for degrees of satura tion between 65 and 73 percent; (2) Compression samples under a constant applied pressure of 6 kg/square cm reduced in volume, i.e. 'col lapsed', when the capillary pressure and hence effective stress was decreased, thus yielding negative values of x. (Author).
A laboratory investigation was conducted to assess the influence of density on the shear strength of unsaturated soil. To vary density, compacted specimens of an expansive clay soil were subjected to different stress histories prior to shear. Tests were performed at a constant water content. The Hvorslev "true friction-true cohesion" concept was used to normalize the effects of density differences on the shear strengths of both saturated and unsaturated specimens. It was determined that shear strengths of unsaturated soils were dependent on the stress state, density, and water content of specimens at failure. A modified Mohr-Coulomb failure model to predict the shear strength of unsaturated soils is proposed. The effect of suction is to increase the value of the cohesion intercept in this model. The actual measurement of soil suction is not required to apply the model.
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.
The principles and concepts for unsaturated soils are developed as extensions of saturated soils. Addresses problems where soils have a matric suction or where pore-water pressure is negative. Covers theory, measurement and use of the fundamental properties of unsaturated soils--permeability, shear strength and volume change. Includes a significant amount of case studies.
In recent decades the development of unsaturated soil mechanics has been remarkable, resulting in momentous advances in fundamental knowledge, testing techniques, computational procedures, prediction methodologies and geotechnical practice. The advances have spanned the full spectrum of theory and practice. In addition, unsaturated materials exhibiting complex behaviour such as residual soils, swelling soils, compacted soils, collapsing soils, tropical soils and solid wastes have been integrated in a common understanding of shared behaviour features. It is also noteworthy that unsaturated soil mechanics has proved surprisingly fruitful in expanding to other neighbouring areas such as swelling rocks, rockfill mechanics, and freezing soils. As a consequence, geotechnical engineering involving unsaturated soils can be now approached from a more rational and systematic perspective leading towards an improved and more effective practice. Unsaturated Soils contains the papers presented at the 5th International Conference on Unsaturated Soil (Barcelona, Spain, 6-8 September 2010). They report significant advances in the areas of unsaturated soil behaviour, testing techniques, constitutive and numerical modelling and applications. The areas of application include soil-atmosphere interaction, foundations, slopes, embankments, pavements, geoenviromental problems and emerging topics. They are complemented by three keynote lectures and three general reports covering general issues of modelling, testing and applications. Unsaturated Soils is a comprehensive record of the state-of-the art in unsaturated soil mechanics and a sound basis for further progress in the future. The two volumes will serve as an essential reference for academics, researchers and practitioners interested in unsaturated soils.
Unsaturated soil mechanics is now increasingly recognized as an integral part of mainstream soil mechanics, and the importance and relevance of unsaturated soil mechanics for the broad field of geotechnical engineering no longer needs to be emphasized. The two volumes making up Unsaturated soils include papers from the 4th Asia Pacific Confere