Push Piers
Solve Settling Foundation Problems
Hydraulic push piers
Hydraulic push piers are essentially a helical pier without the helix. These are steel rods driven down into the ground by a hydraulic jack which is pushing up against the foundation.
To work, there needs to be something to push against, so these are not suitable for new construction where the foundation has not yet been poured. However they are suitable
for remedial work and foundation lifting where the typical weight of the structure is in the neighborhood of one ton per lineal foot. However, one must be careful that the foundation
that it is attached to is strong and can take a concentrated load.
Hydraulic push piers are essentially a helical pier without the helix. These are steel rods driven down into the ground by a hydraulic jack which is pushing up against the foundation.To work, there needs to be something to push against, so these are not suitable for new construction where the foundation has not yet been poured. However they are suitable
for remedial work and foundation lifting where the typical weight of the structure is in the neighborhood of one ton per lineal foot. However, one must be careful that the foundation
that it is attached to is strong and can take a concentrated load.
The piers are typically driven one at a time so the full building weight is available to drive the pier. As each pier is driven, the friction between the soil and the pier accumulates until it exceeds the load being placed on the pier. This is called “driving to refusal” where the foundation just starts to lift and the pier refuses to go any deeper with the available foundation weight.
An advantage over helicals is that they can be installed without any torque equipment, generally closer to a wall, and can register the load capacity directly. The disadvantage is that since they are friction supported, expansive clay in the intermediate layers can lift them up unless they are deep enough into bedrock or other layers unaffected by moisture. This means that they must have enough force on them to drive them to bedrock, something that is not always done if the contractor is in a hurry or careless. Refusal should happen at bedrock but won’t if there is not enough reaction force from a lightly loaded foundation. In contrast, helical piers are end loaded, are not affected by a light foundation, and are generally unaffected by intermediate expansive soil. The pier itself is cheaper than a helical pier because there is no helical blade. Gary Collins, P.E.
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