Soil Survey Interpretation for Engineering Purposes [antikvár]

- 1 - INTRODUCTION In niOBt developing countries considerable "benefits can "be achieved through increased en^neering interpretations of soils* For too long engineering aspects of uses of soils defined as pedological units have been neglected, chiefly because soil data were lacking and because more inimediate pressures appeared to be evident to concentrate on uses of soils for increasing food production. At the present time, however, enough soil data are becoming available in most developing countries so that a start can be made for applying the soil profile descriptions, soil laboratory data and soil maps toward solution of soil engineering problems also. Programmes involving economic development, increasing productivity and improving environmental quality should be as much concerned with building better roads, improving waste disposal facilities and laying out pipeline routes and irrigation and drainage systems, as with the response of different soils to different fertilizer inputs. The purpose of this publication is to provide some guidelines that will assist workers in developing ooxmtries in improving use of their soil maps and data in helping to solve some of the engineering problems associated with economic development, Pedological soil maps and data are being increasingly recognized as being val\iable for engineering pxirposes and are being increasingly improved for engineering uses. Several authors (e.g., Olson, 1964; Orvedal, I963) have pointed out relationships between pedology and engineering. Revisions in the Soil Survey Manual (Soil Survey Staff, 1951) for particle size and other determinations will make soil survey data of even more value for engineers. Criteria for the comprehensive Soil Taxonomy (Soil Survey Staff, 1970) are based to a considerable extent upon characteristics of soils important for engineering as well as agricultural uses. Ajb Orvedal (1963) states: "Today, it is becoming increasingly recognized that many, perhaps most, properties which influence the behaviour of soils in construction also may be related to the prc^ duction of plants, and, conversely, many, perhaps most, properties which influence the production of plants also may be related to the behaviour of soil in construction; and both are commonly related to soils as natural bodies. Engineers and soil scientists have, therefore, a growing common interest in soils." In most developing countries procedures for making soil descriptions and maps approximate those outlined in the Soil Survey Manual (Soil Survey Staff, 1951; FAO, 1965). Soil laboratory determinations on pedological samples generally approximate those outlined in Soil Survey Investigations Report Number 1 (Soil Survey Staff, 1967)* Observations from soil maps and descriptions valuable for engineering interpretations include those relating to slope, drainage, geology, stoniness, depth to bedrock, texture, consistence, reaction and structure. Laboratory analyses commonly run on pedological soil samples which are especially valuable to engineers include percent sand, percent silt, percent clay, percent and size of coarse fragments, mineralogy, percent organic matter, percent Ca CO , bulk density, coefficient of linear extensibility, percent Hg 0 at I/3 bar tension, percent K^O at I5 bars tension, percent Na, etc. Soil analyses that engineers need are outlined in many publications including PCA Soil Primer (PCA, 1962) and the Soils Manual for Design of Asphalt Pavement Structures (Asphalt Institute, 1964). Fortunately, many of the analyses required on soil samples by engineers can be approximated, estimated, adapted or transferred from the pedological descriptions and analyses. Some pedological soil tests, like the coefficient of linear extensibility (Soil Survey Staff, 196?), have been created by soil scientists especially to make their soil analyses more valuable for engineers to use. Recently an excellent guide has been published (Soil Survey Staff, 1971) to make ratings of pedologicallyMiefined soils for various engineering uses.