How to prepare concrete bedding under a tank

In order to ensure the necessary bearing capacity of the base to support embedded tanks, the tanks themselves need to be addressed.

Whenever tanks are embedded, it is necessary to determine the structure’s current base ratios. Based on them, statics are engineered to address the tanks in each design individually.

The starting points are:

- An engineering and geological survey of the site
- Layout and dimensions of the underground tanks
- Type of load on the tank
- Standard bases used by the tank manufacturer

Simple structure base ratios

Where the structure’s foundation ratios fall under the category of simple, the generally recommended composition below can be used:

- 120-millimeter thick compacted gravel (crushed suitable material is crushed gravel sand appropriate for mechanical compaction is suitable)

- 150-mm thick supporting reinforced concrete slab (minimum Grade C 16/20 strength, KARI 6-diameter 150x150 reinforcing mesh)

- 30-mm thick sand bedding (fine-grained sand fraction max. 0-4 mm against the plane

In some cases, and not only recommended from the structural analysis, individual tanks can only be embanked in evenly compacted sand-gravel. In this case, however, the subgrade should be compacted so the deformed Edef modulus reaches a minimum 50 Mpa.