Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Vacuum Consolidation

Vacuum consolidation is a ground improvement technique that accelerates the consolidation of soft soils by applying a vacuum to the soil through vertical drains. The vacuum increases the effective stress in the soil, causing it to consolidate and gain strength. Vacuum consolidation near existing expansion joints requires careful planning to minimize the effects on the joints. Vacuum consolidation process involves installing vertical drains in the soft soil, covering the area with an airtight membrane, and applying a vacuum to the drains. The vacuum draws water out of the soil through the drains, causing the soil to consolidate. The process continues until the required degree of consolidation is achieved. Ground settlement from vacuum consolidation is the primary effect on adjacent expansion joints. The consolidation of the soft soil causes the ground surface to settle, which can affect the level and alignment of adjacent expansion joints. Settlement monitoring is recommended during vacuum consolidation near existing joints. Settlement prediction for vacuum consolidation requires knowledge of the soil compressibility and the drainage conditions. The settlement is calculated using the consolidation theory, which relates the settlement to the applied effective stress and the soil compressibility. The settlement prediction must be verified by monitoring during the consolidation process. Post-consolidation inspection of existing expansion joints must verify that the consolidation 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. Vacuum consolidation effectiveness is verified by comparing the soil properties before and after consolidation. Vane shear tests and piezocone tests are performed before and after consolidation to measure the improvement in soil strength and stiffness. The test results are compared with the design requirements to verify that the consolidation has achieved the required improvement.