Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Permeation Grouting

Permeation grouting is a ground improvement technique that fills the voids in granular soils with a low-viscosity grout without displacing the soil particles. The grout permeates through the soil voids, binding the particles together and increasing the strength and stiffness of the soil. Permeation grouting near existing expansion joints requires careful planning to minimize the effects on the joints. Permeation grouting process involves injecting low-viscosity grout (cement, silicate, or acrylic) into the ground through injection pipes. The grout flows through the soil voids under gravity or low pressure, filling the voids and binding the soil particles. The process is repeated at multiple injection points to treat the full volume of soil. Grout selection for permeation grouting depends on the soil grain size and the required improvement. Cement grout is suitable for coarse-grained soils with large voids. Silicate grout is suitable for medium-grained soils. Acrylic grout is suitable for fine-grained soils with small voids. The grout must have a viscosity low enough to permeate the soil voids without displacing the soil particles. Ground heave from permeation grouting is minimal because the grout fills the existing voids without displacing the soil. However, if the injection pressure is too high, the grout can fracture the soil and cause ground heave. The injection pressure must be monitored and controlled to prevent fracturing. Post-grouting inspection of existing expansion joints must verify that the permeation grouting 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. Permeation grouting effectiveness is verified by comparing the soil properties before and after grouting. Permeability tests and strength tests are performed before and after grouting to measure the improvement. The test results are compared with the design requirements to verify that the grouting has achieved the required improvement.