AASHTO R 75-2016 Standard Practice for Developing a Family of Curves.pdf

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1、Standard Practice for Developing a Family of Curves AASHTO Designation: R 75-161Release: Group 3 (August 2016) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1b R 75-1 AASHTO Standard Practice for Developing a Fam

2、ily of Curves AASHTO Designation: R 75-161Release: Group 3 (August 2016) 1. SCOPE 1.1. This standard practice provides a process for developing a family of curves using multiple individual moisture/density relationships (curves) developed according to T 99 or T 180. 1.2. The values stated in SI unit

3、s are to be regarded as the standard. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: T 99, Moisture-Density Relations of Soils Using a 2.5-kg (5.5-lb) Rammer and a 305-mm (12-in.) Drop T 180, Moisture-Density Relations of Soils Using a 4.54-kg (10-lb) Rammer and a 457-mm (18-in.) Drop 3. TERMINOLOGY

4、 3.1. Definitions: 3.1.1. family of curvesa group of soil moisture-density relationships (curves) determined using T 99 or T 180, which reveal certain similarities and trends characteristic of the soil type and source. 3.1.2. spinesmooth line extending through the point of maximum density/optimum mo

5、isture content of a family of moisture-density curves. 4. SIGNIFICANCE AND USE 4.1. All curves used in a family must be developed using a single Method: A, B, C, or D of T 99 or T 180. 4.2. Curves are plotted on a graph; the family is developed by drawing a smooth line through the maximum density/op

6、timum moisture points. At least three curves are required to form a single family. 4.3. Generally, it will be found that higher unit mass soils assume steeper slopes with maximum dry densities at lower optimum moisture contents, while the lower unit mass soils assume flatter, more gently sloped curv

7、es with higher optimum moisture contents (Figure 1). 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-1b R 75-2 AASHTO Figure 1Example of Curves 5. DEVELOPING A MOISTURE-DENSITY FAMILY OF CURVES 5.1.

8、Sort the curves by Method (A, B, C, or D of T 99 or T 180). At least three curves are required per family. 5.2. Select the highest and lowest maximum dry densities from those selected to assist in determining the desired scale of the subsequent graph. 5.3. Plot the maximum density and optimum moistu

9、re points of the selected curves on the graph. 5.4. Draw a smooth, “best fit,” curved line through the points creating the spine of the family of curves (Figure 1). 5.5. Remove maximum density and optimum moisture points that were not used to establish the spine. 5.6. Add the moisture/density curves

10、 associated with the points that were used to establish the spine. It is not necessary to include the portion of the curves over optimum moisture. Family of Curves DevelopmentSpineIncrementalCurves80% LineMoisture Content (%)8% 10% 12% 14% 16% 18% 20% 22%DryDensityPCF108.0 lb/ft3106.0 lb/ft3104.0 lb

11、/ft3102.0 lb/ft3100.0 lb/ft398.0 lb/ft396.0 lb/ft394.0 lb/ft3 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-1b R 75-3 AASHTO Note 1Intermediate template curves using slopes similar to those of the

12、original moisture-density curves may be included when maximum density points are more than 2.0 lb/ft3apart. Template curves are indicated by a dashed line. 5.7. Plot the 80 percent of optimum moisture range when desired: 5.7.1. Using the optimum moisture of an existing curve, calculate 80 percent of

13、 optimum moisture and plot this value on the curve. Repeat for each curve in the family. 5.7.2. Draw a smooth, “best fit,” curved line connecting the 80 percent of optimum moisture points plotted on the curves that parallel the spine. 6. KEYWORDS 6.1. Family of curves; moisture/density relationships. 1This full standard was first published in 2016. 2016 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.