Foundation Failure

PRESSURE GROUTING

Pressure Grouting is the art of injecting grout ( either cementitious or chemical ) through an injection nozzle, into a void, cavity or crack.

Although cementitious grouting (sometimes referred to as "Mud Jacking") is more commonly used when a concrete slab has "sunk" due to weak soil conditions, voids in the soil or excessive moisture in the soil. To pressure grout a concrete slab, small holes (1"-2" in diameter) are cored or drilled, in a specific pattern, throughout the slab. Then the grout is injected, under some pressure ( as required by loads ) ranging from just a few pounds per square inch (PSI) to several hundred PSI. Once the voids have been filled, the pressure will start building and the concrete will began to rise. Once the grouting has been completed, the holes are topped off with a non-shrink grout and struck off smooth with the floor surface.

When grouting a concrete slab, in this manner, the contractor will not offer any warranty, as he is, only, lifting the slab and filling the voids as he lifts. The slab is still on the soil that allowed it to settle, to begin with. Should warranties be required, additional grouting would be required. This is called "compaction grouting" and is performed by injecting grout, under higher pressures, through pipe, into the sub-grade below the slab. This process will compact the soil, to some depth, below the slab and prevent future settlement.

Other methods of pressure grouting utilize epoxies and/or urethanes to repair structural cracks in concrete or seal cracks from leaking.

HELICAL PIERS

Helical Piers are much like a wood screw, in that they are "screwed" into the ground with a hydraulic motor. Picture a wood screw being screwed into a soft pine board and behind the pine board is an oak board. The screw is easy to turn, in the pine board, however, when it gets to the oak board, it gets very hard to turn. When installing a helical pier, you are looking for the "oak board". In other words, you are looking for very hard soil. This is determined by the hydraulic pressure required to turn the hydraulic motor. The harder the soil, the higher the required pressure to turn the motor. The installer is looking for a certain pressure, before he terminates his install. Utilizing conversion tables, pressures are converted to torque and then to bearing capacity of the helical pier. With this method, the installer can install a pier to a capacity greater then what is actually required, thus, providing a "safety factor". The industry standard for this safety factor is two (2) times the required loads; i.e., If the required load was 20,000 Lbs. (or 20 KIPS), then the helical pier should be installed to 40,000 Lbs. (or 40 KIPS) capacity.

Helical piers are made in various sizes and configurations, as there is no "one pier fits all". Shaft sizes can be 1-1/4", 1-1/2", 1-3/4" and 2" Round Corner Square Shaft, or 2-7/8", 3-1/2", 4-1/2" and 8-5/8" diameter pipe. The "Helix" (or helices) can vary from 6" diameter to 24" in diameter and will vary from 3/8" to ¾" in thickness. The proper configuration will depend on load requirements and soil conditions.

Helical piers can be used to "jack up" or "stabilize" a sinking foundation or can be used in the creation of the footings of a new foundation, consequently, the home or building would be built on top of the helical piers, preventing any future settlement.