Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Surcharge Preloading

Surcharge preloading is a ground improvement technique that accelerates the consolidation of soft soils by applying a temporary surcharge load to the ground surface. The surcharge load increases the effective stress in the soil, causing it to consolidate and gain strength. Surcharge preloading near existing expansion joints requires careful planning to minimize the effects on the joints. Surcharge preloading process involves placing a temporary fill on the ground surface to apply the surcharge load. The fill is typically 2-5 meters thick, depending on the required degree of consolidation. The fill is left in place until the required degree of consolidation is achieved, then removed before the bridge is constructed. Ground settlement from surcharge preloading 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 surcharge preloading near existing joints. Settlement prediction for surcharge preloading 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 preloading process. Post-preloading inspection of existing expansion joints must verify that the preloading 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. Surcharge preloading effectiveness is verified by comparing the soil properties before and after preloading. Vane shear tests and piezocone tests are performed before and after preloading to measure the improvement in soil strength and stiffness. The test results are compared with the design requirements to verify that the preloading has achieved the required improvement.