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Calculating Block Requirements for Container Support

This article explains the process for calculating how many blocks are required in order to place a container on top of them.

Introduction

Properly supporting a container on blocks is crucial for safety. This article provides a step-by-step guide to determine the necessary number of blocks and their minimum required strength (MPA) when using Interbloc products for container support.

Formula and Calculations

  1. Weight per Block:

    • Divide the total weight of the container (in kilograms) by the number of blocks used for support.

  2. Kilonewton Meters:

    • Multiply the weight per block (in kilograms) by 9.80665 to convert it to kilonewton meters (kNm).

  3. Bearing Area:

    • Calculate the bearing area of the block in square millimeters (mm²) by multiplying its length and width (in millimeters). For standard Interbloc blocks, the dimensions are 180mm x 160mm, resulting in a bearing area of 28,800 mm².

  4. Applied Pressure:

    • Divide the weight per block (in kNm) by the bearing area (in mm²) to determine the applied pressure in Newtons per square millimeter (N/mm²). Note that 1 N/mm² is equivalent to 1 MPa (Megapascal).

Real-World Example

Let's consider a 5-tonne container supported by four concrete blocks:

  • Weight per block: 5000 kg / 4 = 1250 kg
  • Kilonewton meters: 1250 kg * 9.80665 = 12.258 kNm
  • Applied pressure: 12.258 kNm / 28,800 mm² = 0.0004256 kNm/mm² = 0.4256 N/mm² = 0.4256 MPa

Interbloc Premium Block Strength

Interbloc premium blocks have a minimum MPa of 20. For calculating bearing stress, a safety factor of 0.15 is applied, resulting in a minimum working MPa of 3. In our example, the calculated applied pressure of 0.4256 MPa is well below this limit, providing a safety factor of approximately 7.

Important Considerations

  • Bearing Area: The bearing area is determined by the size of the locking knobs on the container's corners, which typically measure 180mm x 160mm.
  • Additional Safety Measures: Secure the container against lateral movement due to wind or earthquakes. Consider using shear keys to prevent accidental block slippage (especially when stacking blocks) and assess the ground's bearing capacity.
  • Even Distribution: Ensure the container's weight is evenly distributed across all supporting blocks.