Underpinning is typically required when an
existing structure is experiencing or may potentially experience excessive
settlement. Excessive foundation settlement occurs for many of the same
reasons, despite the size or type of structure. A structure might be underlain
by weak or compressible soils that compress excessively under the building’s
weight. Competent soils may be weakened as they ravel into compromised underground
utilities underlying a foundation. In addition, a foundation might be underlain
by debris, which decomposes or consolidates over time. In karstic regions,
sinkholes can cause a building to settle as the soils ravel into a void in the underlying
bedrock. In other regions, buildings shift when soils expand and contract with
changing moisture content.
A variety of solutions is available to remediate or
avoid settlement problems, including foundation underpinning. Foundation
underpinning may be selected when grouting techniques alone cannot improve poor
soils. Foundation underpinning techniques bypass the problem soils by using structural
elements to transfer the building’s load to underlying competent soils or
Micropiles, also known as minipiles, are deep foundation elements constructed using high-strength, small-diameter steel casing and/or threaded bar. Micropile drill rigs allow construction in restricted access, low headroom interiors, permitting facility upgrades with minimal disruption to normal operations. The finished foundation elements can be designed to resist compressive, uplift, and lateral loads.
Residential underpinning offers an economical solution that is fast, non-invasive, clean, and virtually free of vibration and noise. Jacked piers can be used to raise foundations for a home or building which has settled, closing wall and foundations cracks. Helical piles (helical piers) are deep foundation underpinning elements constructed using steel shafts with helical flights. Residential foundation repair can be performed in tight spaces with minimal disturbance to the surrounding area. Underpinning foundations can be designed such that the aesthetics of the structure are not compromised.
When excavating adjacent to an existing structure, shoring and underpinning may be required. A solution could include underpinning elements combined with a retaining wall. Jet grouting can be constructed as secant soilcrete columns to resist overturning and sliding while maintaining the integrity of supported structures and nearby utilities. Jet grouting’s ability to construct soilcrete in confined spaces and around subsurface obstructions provides a unique degree of design flexibility. In situations requiring control of groundwater or excavation of unstable soil (water-bearing or otherwise), jet grouting should be considered.
Hayward Baker has experience with the full range of shoring and underpinning techniques to provide foundation stabilization for your structure.