In some cases, stopping shifting entirely over time may not be possible. However, there are methods you can implement that prevent/significantly reduce the chance of the blocks from shifting.

These are the methods you can implement:

• Prepare the foundation properly. Ensure it is compacted and has adequate draining. Consulting a structural engineer can help to ensure everything is right before installation.
• Conduct a test of the foundation in advance if possible to determine its type and if it would be suitable to place interlocking concrete blocks on.
• Using professionals to install the blocks is one of the best ways to ensure that shifting doesn’t occur due to installation. Unprofessional installation can be careless and focus on speed rather than precision.

Are sinkholes causing my blocks to shift?

Possibly, as ground shifting can be a sign of sinkholes, However, it’s not the only cause. The way to understand is looking for sudden, localised shifting, especially with visible depressions, this strongly suggests sinkhole activity. 

However, gradual, widespread shifting usually indicates other soil issues.

How can I gauge the ground before placing interlocking concrete blocks?

There are clear signs and tests you can look out for and conduct to gauge whether the ground is suitable for interlocking concrete blocks to stack on top of. 

Drainage:

Look around the area you want to place the blocks, how does water drain from the area? If you see water run off, or areas where water pools, it can indicate potential instability for your blocks. 

Vegetation:

On the other hand, healthy, even vegetation can indicate stable soil. Sparse or uneven vegetation may suggest underlying problems. Areas where vegetation will not grow could be a sign of poor soil. It can be even worse if grass can’t grow in that area.

Tree roots can both stabilise and destabilise. Large roots can draw significant moisture from the soil, leading to shrinkage and settlement. Conversely, as roots grow, they can exert pressure on the blocks, causing them to shift. Although this can take years before noticing. 

Existing infrastructure:

If there are any nearby structures/infastructure, reviewing their condition can imply the suitability of placing your blocks in the area. Signs of settlement or cracking in those structures may indicate potential problems with the ground.

In addition, underground pipes or cables can create weak points in the soil. Leaks from these utilities can saturate the soil, leading to settlement and shifting. Being abreast of pipes, cables, and if they are often repaired in the area can provide an insight into the general soil quality. 

Human activity:

Human activities like fracking or reservoir impoundment can induce minor seismic events, which can trigger ground shifting in previously stable areas.

Further to this point, excavations near your interlocking block structure can destabilise the surrounding soil, causing shifting. This is a critical factor in urban areas or during construction projects.

Tests you can conduct:

Compaction tests

1. Dig a small hole, approximately 6-12 inches deep. The size of the hole doesn’t have to be exact.
2. Remove the excavated soil and set it aside.
3. Return the excavated soil to the hole in layers, compacting each layer with the hand tamper.
4. Apply consistent pressure with a hand tamper.
5. If the soil is dry and crumbly, you can lightly moisten it with water. Moist soil tends to compact better. However, avoid over-wetting.
6. Pay attention to how the soil responds to compaction.
7. If the soil becomes dense and firm with minimal effort, it indicates good compaction.
8. If the soil remains loose and doesn’t compact well, it suggests poor compaction.
9. If the soil after being tamped, is still well above the surrounding ground level, it means the soil has poor compaction.

Percolation test (for drainage):

Dig a hole and fill it with water. Observe how quickly the water drains away. Slow drainage indicates potential drainage problems.   

Professional assessment options:

Please note that this level assessment below may not be available for domestic projects, they may be more applicable to commerical/industrial construction. 

Soil bearing capacity test:

A soil bearing capacity test is another way to measure the amount of load that soils can handle. This is conducted by geotechnical engineers. 

Soil boring and analysis:

Geotechnical engineers can take soil samples and analyze them to determine the soil’s properties, including its bearing capacity, compaction, and drainage characteristics.   

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