1. Compaction Testing
On-site Density Meter: Use an on-site density meter (such as the ring knife method or sand injection method) to measure the density of the compacted soil to ensure it meets design requirements. For highway subgrade construction, the compaction level should be no less than 96%.
Dynamic Cone Penetrometer: Used to measure the bearing capacity of subgrade soil. Dynamic penetration tests are used to assess the strength and density of the compacted soil.
2. Settlement Monitoring
Settlement Observation Markers: During the compaction process, settlement observation markers are placed evenly around the circumference, and settlement is recorded every 10 strikes. For example, in the Jinan Century Kaiyuan Creative Industrial Park project, the impact load reached a depth of 1.5m on the 10th strike, resulting in an average settlement of 5mm per 10 strikes.
Final Settlement: After a certain number of strikes are reached, the settlement changes are observed. For example, after 50 strikes, the cumulative settlement of the settlement marker at a depth of 1.5m begins to decrease, indicating that the soil layer at that location has begun to rise.
3. Compaction Frequency
Compaction Frequency: Generally speaking, the compaction frequency at maximum lifting height should be greater than 30 strikes/minute to achieve the specified effective reinforcement depth. During construction, the compaction frequency is typically greater than 40 strikes/minute.
4. Visual Inspection
High-definition Camera: A high-definition camera is used to capture the operation and results of the tamping rammer, and image processing technology is used to analyze the uniformity and depth of compaction.
5. Force Sensor Inspection
Real-time Monitoring: A force sensor is installed on the tamping rammer to monitor the pressure applied during compaction in real time to ensure that design requirements are met.
6. Vibration Monitoring
Vibration Sensor: A vibration sensor monitors the vibration frequency and amplitude of the tamping rammer during operation to assess the machine's operating condition and stability. 7. Testing and Adjustment
Trial Ramming Tests: Test ramming tests are conducted at the actual construction site, using different ramming intensities (e.g., level 1, 2, and 3) to measure the ground compaction. The number of hammer strokes required to achieve the desired compaction level is then selected for construction.
Gradual Adjustment: Based on the test results, the ramming intensity and frequency are gradually adjusted to ensure optimal compaction.
8. Construction Parameters
Single Ramming Energy: Select the appropriate single ramming energy based on the soil type and reinforcement depth. For example, the single ramming energy for roadbed reinforcement is typically 36 kJ.
Number of Ramming Counts: Determine the appropriate number of ramming strikes based on test results. For example, in the Jinan Century Kaiyuan Creative Industrial Park project, the average settlement per 10 strikes was 5 mm.
