Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Jet Grouted Columns

Jet grouting is a ground improvement technique that creates columns of soil-cement by injecting high-pressure cement grout into the ground. Jet grouting near existing expansion joints requires careful planning to minimize the effects on the joints. Jet grouting process involves drilling a hole into the ground, inserting a monitor (injection nozzle), and injecting high-pressure cement grout while rotating and withdrawing the monitor. The high-pressure grout jet cuts and mixes with the surrounding soil, creating a column of soil-cement. Ground heave from jet grouting can occur when the grout pressure is too high or when the grout volume exceeds the volume of the soil that is cut away. Ground heave can affect adjacent expansion joints by changing the joint gap width. Ground heave monitoring is recommended during jet grouting near existing joints. Grout pressure control during jet grouting is critical for preventing ground heave. The grout pressure must be monitored and controlled to prevent it from exceeding the design value. The grout volume must also be monitored to prevent over-injection. Post-grouting inspection of existing expansion joints must verify that the jet 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. Jet grouted column testing after installation verifies that the columns have achieved the required strength and diameter. Core samples are taken from the columns and tested for compressive strength. The column diameter is verified by excavating around the column head. The test results are compared with the design requirements to verify that the columns are performing as intended.