土木工程類專業(yè)英文文獻及翻譯-展示頁
2025-07-08 10:30本頁面
【正文】 BY COLLAPSIBLE SUBGRADESBy Sandra L. Houston,1 Associate Member, ASCE(Reviewed by the Highway Division)ABSTRACT: Problem subgrade materials consisting of collapsible soils are mon in arid environments, which have climatic conditions and depositional andweathering processes favorable to their formation. Included herein is a discussionof predictive techniques that use monly available laboratory equipment andtesting methods for obtaining reliable estimates of the volume change for theseproblem soils. A method for predicting relevant stresses and corresponding collapsestrains for typical pavement subgrades is presented. Relatively simple methods ofevaluating potential volume change, based on results of familiar laboratory tests,are used.INTRODUCTIONWhen a soil is given free access to water, it may decrease in volume,increase in volume, or do nothing. A soil that increases in volume is calleda swelling or expansive soil, and a soil that decreases in volume is called acollapsible soil. The amount of volume change that occurs depends on thesoil type and structure, the initial soil density, the imposed stress state, andthe degree and extent of wetting. Subgrade materials prised of soils thatchange volume upon wetting have caused distress to highways since the beginning of the professional practice and have cost many millions of dollarsin roadway repairs. The prediction of the volume changes that may occur inthe field is the first step in making an economic decision for dealing withthese problem subgrade materials.Each project will have different design considerations, economic constraints, and risk factors that will have to be taken into account. However,with a reliable method for making volume change predictions, the best designrelative to the subgrade soils bees a matter of economic parison, anda much more rational design approach may be made. For example, typicaltechniques for dealing with expansive clays include: (1) In situ treatmentswith substances such as lime, cement, or flyash。 (2) seepage barriers and/or drainage systems。and (2) estimating the amount of volume change that is likely to occur in the39。Russman 1987). In addition to the excessive waviness of the roadway surface, bridge foundations failures, such as the Steins Pass Highway bridge,110, in Arizona, have frequently been identified with collapse of foundationsoils.Identification of Collapsible SoilsThere have been many techniques proposed for identifying a collap
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