Published: Jan 1962
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In the development of modern techniques for evaluating the engineering properties of soils, field test procedures have received only a fraction of the attention accorded to laboratory methods. The profession has put forth much effort to refine laboratory methods and apply the results to conditions assumed to exist in the field. Yet, the inherently variable nature of soils and soil-water systems frequently makes representative sampling and laboratory testing impossible. The structural or hydraulic action of a mass of soil may be influenced greatly by undetected and untested strata or discontinuities. Field tests, on the other hand, if properly conducted and interpreted, can reflect this variable nature and indicate the true action of the soil mass. Field tests and measurements can also be used profitably to monitor changes in soil or soil-water systems during and after construction. Examples of such applications include the use of piezometers to measure the dissipation of pore pressure in weak foundations underlying fills and to monitor water levels during excavation dewatering. Also, mass movements in slopes and in soils adjacent to excavations can be detected by inclinometers placed in plastic casings. For stability problems of this sort, nature has provided us with an effective warning system: before rupture, small but accelerated deformations will appear. A few field measurements at selected locations in a construction area can be positive indicators of impending trouble. This symposium focuses attention on the value of field procedures in soils and foundation engineering. It is hoped that it will encourage wider use of those tests currently available to engineers and stimulate the development of new methods and devices. Many tests are in use today, but without ASTM guidance in the form of standards, tentatives, or even suggested methods. The need for refinement of test procedures is evident. Some field tests are rather elementary in performance, but their interpretation is not simple. Examples of such are the plate-loading test, the pile-loading test, and the percolation test. Papers on these three have been included, and it is hoped that the symposium will provide some necessary guidance to their interpretation.
Brown, P. P.
Consultant, Soil Mechanics and Paving, Bureau of Yards and Docks, Washington, D. C.