Improved subgrade preparation for main road based on AASTHTO
1. Site Investigation
2. Soil Testing and Classification
- Collect soil samples from various depths.
- Submit samples to a certified laboratory.
- Conduct sieve analysis and Atterberg limits tests.
- Classify soil according to AASHTO standards.
- Document findings and prepare a classification report.
- Gather soil samples representative of the site.
- Weigh samples before drying (wet weight).
- Dry samples in an oven at 105°C for 24 hours.
- Weigh samples after drying (dry weight).
- Calculate moisture content using the formula.
- Perform Atterberg limits tests on soil samples.
- Determine the liquid limit using the cup method.
- Determine the plastic limit by rolling the soil.
- Calculate the plasticity index (PI = LL - PL).
- Interpret PI values to assess soil behavior.
3. Subgrade Design
- Analyze traffic volume and load types.
- Evaluate existing soil properties and classifications.
- Use AASHTO guidelines to establish minimum subgrade depth.
- Consider environmental factors affecting soil stability.
- Select appropriate materials based on AASHTO criteria.
- Create design layers for drainage and compaction.
- Incorporate reinforcement if required for heavy loads.
- Ensure alignment with local building codes and regulations.
- Identify locations of weak subgrade through testing.
- Determine required modifications for stabilization.
- Consider options such as soil replacement or reinforcement.
- Document all changes and rationale in design plans.
4. Site Preparation
5. Moisture Control
- Regularly check moisture levels using moisture meters.
- Document moisture readings at different locations.
- Adjust moisture levels based on optimal range for compaction.
- Communicate findings to all team members involved.
- Add water if moisture content is below optimal levels.
- Use sprinklers or water trucks for even distribution.
- If excess moisture is present, employ drying techniques.
- Utilize aeration or tilling to enhance evaporation.
- Conduct thorough mixing of the soil to achieve uniformity.
- Check moisture levels at multiple points across the area.
- Adjust moisture as necessary to ensure consistency.
- Perform a final inspection prior to compaction.
6. Compaction
- Select equipment based on soil type and project requirements.
- Ensure equipment is maintained and calibrated for optimal performance.
- Use rollers for larger areas and vibratory plates for tight spots.
- Operate equipment according to manufacturer's guidelines.
- Perform pre-compaction moisture content tests.
- Adjust moisture levels as necessary before compaction.
- Compact in layers not exceeding specified thickness.
- Monitor compaction progress with density gauges.
- Select testing locations randomly across compacted area.
- Use nuclear density gauge or sand cone method for testing.
- Document test results and compare with required densities.
- Repeat compaction if density is below specified levels.
7. Quality Assurance
8. Final Inspection
- Check for uniformity and consistency throughout the area.
- Inspect for any visible cracks or irregularities.
- Verify that all drainage features are functioning correctly.
- Confirm that the subgrade is free from debris and loose materials.
- Use a level to check for flatness and proper elevation.
- Perform a compaction test to ensure stability.
- Compare measurements against design specifications.
- Identify any areas that require additional treatment or correction.
- Document each step of the preparation process.
- Include test results and compliance data.
- Provide photographs of the final subgrade condition.
- Outline any observed issues and recommended actions.
9. Preparation for Overlying Layers
- Assess existing drainage conditions.
- Design drainage layout according to AASHTO standards.
- Install drainage pipes and structures as needed.
- Conduct a flow test to ensure effectiveness.
- Maintain drainage systems during construction.
- Inspect the subgrade surface visually.
- Remove any visible debris such as rocks or vegetation.
- Conduct soil tests for contaminants.
- Ensure moisture content is within acceptable limits.
- Document the cleanliness of the subgrade.
- Define key performance indicators for monitoring.
- Assign personnel responsible for oversight.
- Schedule regular inspections during layer placement.
- Use measurement tools to assess subgrade integrity.
- Document findings and adjust placement methods as needed.
Use in Manifestly