360R-06 Design of Slabs-on-Ground
—Modulus of subgrade reaction
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- Table 3.1—Unified soil classification system (Winterkorn and Fang 1975)
| 3.4—Modulus of subgrade reaction
3.4.1 Introduction—Design methods listed in Chapter 2 , including Westergaard’s (Westergaard 1923, 1926) pioneering work on rigid pavement analysis, employ the modulus of subgrade reaction as a single property to represent the supporting capacity to be used in design. This modulus, also called the modulus of soil reaction or Winkler foundation, is a spring constant that assumes a linear response between load and deformation from the subgrade. Actually, there is no single k value for a subgrade because the relationship between load and deformation of a soil is nonlinear and is not a fundamental soil property. A typical nonlinear relationship between a normal compressive load and the resulting deformation for an area is depicted in Fig. 3.2 . The type of soil structure, density, moisture content, and Table 3.1—Unified soil classification system (Winterkorn and Fang 1975) Field identification procedures (excluding particles larger than 3 in. [75 mm], and basing fractions on estimated weights) Group symbol Typical names Coarse-grained soils (more than half of material is larger than No. 200 sieve* [75 μm]) Gravels (more than half of coarse fraction is larger than No. 4 sieve * [4.75 mm]) Clean gravels (little or no fines) Wide range in grain size and substantial amounts of all intermediate particle sizes GW Well-graded gravel, gravel-sand mixtures, little or no fines Predominantly one size or a range of sizes with some intermediate sizes missing GP Poorly graded gravels, gravel-sand mixtures, little or no fines Gravel with fines (appreciable amount of fines) Nonplastic fines (for identification procedures, refer to CL below) GM Silty gravels, poorly graded gravel-sand-silt mixtures Plastic fines (for identification procedures, refer to ML below) GC Clayey gravels, poorly graded gravel-sand-clay mixtures Sands (more than half of coarse fraction is smaller than No. 4 sieve * [4.75 mm]) Clean sands (little or no fines) Wide range in grain sizes and substantial amounts of all intermediate tải về 2.35 Mb. Chia sẻ với bạn bè của bạn:
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