General Principles of Underpinning, Lifting, and Leveling Concrete Structures
Underpinning, lifting, and leveling are structural techniques used to stabilize, realign, or reinforce existing concrete structures. These methods are essential when foundations settle, fail, or require strengthening due to changes in load, soil conditions, or usage.
Underpinning involves extending or strengthening the existing foundation. The basic idea is to transfer the building load to deeper, more stable soil or to increase the load-bearing area. Common underpinning methods include mass concrete underpinning, where sections are excavated and filled with concrete in a sequence; beam and base underpinning, where reinforced beams distribute loads to a series of new bases; mini-pile underpinning, which uses piles driven deep into the soil; and screw piles with brackets, where helical steel piles are drilled into stable soil and brackets connect them to the existing foundation.
Lifting and leveling refer to correcting uneven or sunken concrete surfaces. This is done using techniques like mudjacking, where a slurry is pumped under the slab to raise it; polyurethane foam injection, where expanding foam is used for a lighter lift; and hydraulic lifting, where jacks physically push the structure back into place. These methods help restore original alignment and prevent further damage.
Hand Jack Equipment vs. Automated Hydraulic Equipment
Hand jacks, such as manual screw jacks or mechanical bottle jacks, are operated manually and typically used for smaller loads. They are simple to use, inexpensive, and don't require power, making them good for limited or temporary repairs. However, they require significant labor, are harder to synchronize when using multiple jacks, and may not provide the precision needed for delicate or large-scale work.
Automated hydraulic equipment uses pressurized fluid systems powered by electric or gas pumps. These tools are capable of lifting much heavier loads with precision and can be synchronized across multiple points for uniform lifting. Hydraulic systems are preferred for large buildings or critical structures because they offer greater control, better safety, and more consistent results. They also support remote operation and are often paired with monitoring instruments to track pressure and displacement in real time. Their main downsides are cost, complexity, and the need for skilled operators.
