Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D4429-09 – Standard Test Method Technical Guide
📐 Test Method Overview and Scope
This test method, with designation D4429-09a, is designed for determining the California Bearing Ratio (CBR) of soils in place. It specifically evaluates the relative quality of subgrade soils but is also applicable to subbase and some base-course materials. The test is performed in situ and corresponds to the laboratory method outlined in Test Method D1883.
The standard allows for the expression of results in either SI units or inch-pound units, which must be used independently. Combining values from these two systems is not permissible as it can lead to non-conformance. Additionally, all observed and calculated values must follow the significant digits and rounding guidelines of Practice D6026.
⚙️ Test Procedure and Equipment
The procedure involves the penetration of a piston into the soil in place, measuring the load required for penetration. This in-situ method is analogous to the laboratory CBR test but adapted for field conditions. Equipment includes a loading device, a penetration piston, and systems for measuring deformation. For supplementary determinations of density and moisture content, the standard references several ASTM methods.
These referenced methods include Test Method D1556 (Sand-Cone), Test Method D2167 (Rubber Balloon), Test Method D2937 (Drive-Cylinder), and Test Method D2216 for moisture content. The use of these methods ensures comprehensive evaluation of the soil’s physical properties.
📊 Key Measured Properties and Reporting
The key measured property is the California Bearing Ratio, derived from the penetration load data. The reporting of results must adhere to the significant digits specified in Practice D6026 to maintain consistency in geotechnical data. The standard also references Practice D3740 for minimum requirements of testing agencies.
| 🟦 System | 📏 Unit for Force | 📐 Unit for Mass |
|---|---|---|
| SI | Newton (N) | Kilogram (kg) |
| Inch-Pound | Pound (lbf) | Pound-mass (lbm) |
| 🎯 Standard Number | 📏 Title |
|---|---|
| D653 | Terminology Relating to Soil, Rock, and Contained Fluids |
| D1556 | Density and Unit Weight of Soil in Place by Sand-Cone Method |
| D1883 | CBR (California Bearing Ratio) of Laboratory-Compacted Soils |
| D2167 | Density and Unit Weight of Soil in Place by Rubber Balloon Method |
| D2216 | Laboratory Determination of Water (Moisture) Content of Soil and Rock |
| D2937 | Density of Soil in Place by Drive-Cylinder Method |
| D3740 | Minimum Requirements for Agencies Engaged in Testing of Soil and Rock |
| D6026 | Using Significant Digits in Geotechnical Data |
| D6780 | Water Content and Density of Soil in Place by Time Domain Reflectometry |
⚠️ Important: Values stated in SI or inch-pound units must be used independently to avoid non-conformance with the standard.
💡 Note: All observed and calculated