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DRAINABILITY OF GRANULAR BASES FOR HIGHWAY PAVEMENTS.
| 题名： | DRAINABILITY OF GRANULAR BASES FOR HIGHWAY PAVEMENTS. |
| 作者： | McEnroe-BM |
| 关键词： | GRANULAR-BASE; DRAINAGE-; DEGREE-OF-SATURATION; POROSITY-; SUBDRAINS-; FINE-GRAINED-BASES; COARSE-GRAINED-BASES; DRAINAGE-TIME; COMPUTER-PROGRAMS |
| 摘要： | The best measure of the drainability of a granular base is the minimum degree of saturation that can be achieved through gravity drainage in the field. The amount of water that can drain from a base course depends not only on the physical properties of the material, but also on the cross-sectional geometry of the pavement system. A fine-grained base may remain fully saturated under the largest suction that can be developed through gravity drainage. A formula for the minimum degree of saturation in the granular base is developed from Brooks and Corey's formula for water retention in unsaturated porous media. The relationship for drainable porosity in the FHWA subdrainage design manual tends to overestimate the amount of drainage from fine-grained bases and greatly underestimate the amount of drainage from coarse-grained bases. If the minimum degree of saturation for a granular base is sufficiently low, it will drain fairly quickly. The recommended method for the estimation of drainage times is a one-dimensional analysis of the saturated flow below the phreatic surface. This analysis accounts for the nonuniform spatial distribution of drainable porosity. Casagrande and Shannon's procedure, which is recommended by FHWA, tends to underestimate drainage times, particularly for base courses that are relatively thin. The recommended procedures for subdrainage analysis have been implemented in the SUBDRAIN computer program of the Kansas Department of Transportation. |
| 总页数： | Transportation Research Record. 1994. (1434) pp23-28 (5 Fig., 8 Ref.) |
| 报告类型： | 科技报告 |
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