Foundation Settlement & Foundation Stabilization
Commercial/Industrial
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1. Noticeable slopes in concrete floor slabs or floor framing. Typically
sloped down towards the exterior walls.
2. Diagonal cracks in foundation walls, wider than 1/8".
3. Cracks in foundation walls which are not uniform in width.
4. Diagonal cracks in the exterior masonry.
5. Outward bowing of shallow foundation walls.
There are four common causes of foundation settlement in the Chicago area.
1. Buildings constructed on fill materials which were not properly compacted.
2. Organic material, such as a layer of peat, present under the foundations.
3. Drying and compaction of the soil, also known as soil desiccation,
under the foundations.
4. Slope instability. Less common in Chicago area as the land is relatively
flat.
Not every settlement problem requires a repair. Determining if stabilization and lifting is required depends on the magnitude of movement, the distress being caused to the building, and the age of the building.
Every potential foundation stabilization project begins with an investigation by a Structural Engineer to determine if stabilizing the foundations is required. In some cases a soil boring may be required to determine if the foundation movement can be expected to continue and at what rate. If it is our opinion that foundation stabilization is not required we can provide a report, signed and sealed by a Illinois Licensed Structural Engineer, stating that stabilization is not required. If foundation stabilization is required, we can determine what method of stabilization to use and calculate the required loading and position of the piers.
Foundation stabilization and lifting is typically done by one of two methods. The first is to hydraulically push a steel pile into the ground using the weight of the building as a reaction force. The second utilizes a steel shaft with one or more “threads” or helical shaped steel plates at the beginning of the anchor which allow the steel shaft to be turned or screwed into the ground. This anchor relies on the “threads” bearing on stable and adequate soils to support the building loads. Both methods of foundation stabilization and lifting are commonly referred to as piering.
It has been our experience that helical or screw type piers are effective only when the pier can be driven straight into the ground. For example to support a new floor slab constructed as a steel reinforced concrete slab designed to be supported on the piers. Because of the equipment required to install a helical or screw type pier it is very difficult to drive the pier straight into the ground next to a foundation wall and the pier ends up going into the ground at an angle. This condition leads to a bending stress being induced into the pier shaft which can lead to failure of the pier and bracket.
Push, or hydraulically driven piers, can be driven straight into the ground very close to the foundation wall and are therefore more effective at supporting the foundation wall and the building loads on them. Also the capacities of push type piers can far exceed that of helical or screw type piers.
Typically the exterior walls of industrial and commercial buildings have relatively high dead loads from the wall and roof system. To prevent excessive rotation and bending of the piers these walls are typically pierred from the interior and exterior to balance the loading on the piers.
We designed and developed a push pier system which was covered by 3 US patents. The technology used in our design can be varied to increase pier capacities to fit almost any application, including heavy multi story commercial buildings. We also have access to several vendors who manufacture and supply the helical or screw type piers for supporting new reinforced concrete slabs.