What material is used to maintain the shape of drilled shafts in granular soil conditions until concrete is placed?

In the context of drilled shafts, especially in granular soil conditions, maintaining the integrity of the shaft during the construction process is crucial. Steel casing is the preferred material for this purpose because it provides structural support to the sides of the shaft, preventing collapse or deformation while the concrete is being placed.

Granular soils, such as sand and gravel, lack cohesion and are prone to shifting, particularly in wet conditions or when disturbed. As a consequence, using a steel casing can effectively resist these forces, keeping the drilled shaft open and in the correct shape until the concrete can be poured. This is essential to ensure proper load-bearing capacity and stability of the finished structure.

Other materials, like polymer solutions and corrugated metal pipes, are not typically used in such applications due to their varying degrees of effectiveness in providing temporary support. Polymer solutions may offer some level of stabilization through fluid properties but do not provide the robust physical structure needed in this context. Similarly, while corrugated metal pipes can serve certain purposes in construction, they may not have the strength or rigidity required to handle the loads and pressures typically found in drilled shaft construction in granular soils. Reinforced concrete pipes, although strong, are generally not suited for use as temporary casings during the drilling process, as they