Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Dynamic Compaction

Dynamic compaction is a ground improvement technique that densifies loose soils by dropping a heavy weight from a height. The impact of the weight creates a shockwave that compacts the surrounding soil. Dynamic compaction near existing expansion joints requires careful planning to minimize the effects on the joints. Dynamic compaction process involves dropping a heavy weight (10-20 tonnes) from a height of 10-20 meters using a crane. The impact of the weight creates a crater in the ground surface and compacts the surrounding soil. The process is repeated at multiple impact points to treat the full area of loose soil. Vibration from dynamic compaction can be significant and can affect adjacent expansion joints. The vibration level depends on the weight of the tamper, the drop height, and the distance from the impact point to the joint. Vibration monitoring is recommended during dynamic compaction near existing joints. Ground heave from dynamic compaction can occur near the impact points due to the lateral displacement of the soil. Ground heave can affect adjacent expansion joints by changing the joint gap width. Ground heave monitoring is recommended during dynamic compaction near existing joints. Post-compaction inspection of existing expansion joints must verify that the dynamic compaction has not caused any damage. The inspection should check the joint gap width, the concrete edge beam condition, and the anchor bolt torque. Any damage must be repaired before the bridge is returned to service. Dynamic compaction effectiveness is verified by comparing the soil properties before and after compaction. Standard penetration tests (SPT) or cone penetration tests (CPT) are performed before and after compaction to measure the improvement in soil density. The test results are compared with the design requirements to verify that the compaction has achieved the required improvement.