While most of the general public might not be familiar with the process of piling, those of us in the trade know exactly how crucial it is to ensuring the fundamental stability and security of almost any structure. And for that reason alone, it’s always vital that every stage of the process is done right – including the all-important initial assessment of soil conditions.

Essentially, proper soil assessment ensures the stability and longevity of the structure being built. It’s a process we’re intimately familiar with here at Vxcel Piling, as experienced mini piling contractors with around 15 years of experience to our name. So, in this comprehensive guide, we’ll walk you through the step-by-step process of assessing soil conditions for piling, so that you can have peace of mind that your construction project is built on a solid foundation.

Step 1: Preliminary Site Investigation and Desk Study

Before going straight into detailed soil assessments, the very first step needs to be a preliminary site investigation. This involves gathering as much existing information about the site as possible, including geological maps, previous site investigations, and local soil reports. All this provides a basic understanding of the soil composition, and a couple of useful early warnings about any potential risks or challenges.

The next stage involves performing a ‘desk study’ – essentially, a review of all the information and data already collected so far, encompassing all available data and documents related to the site. This includes geological maps, soil surveys, and historical records of the area.

This information all needs to be carefully analysed to identify any potential hazards or constraints that may affect piling operations. Particularly close attention needs to be paid to factors such as soil type, groundwater levels, and presence of contaminants.

Step 2: Ground Investigation and Soil Testing

With all the preliminary information in hand, it’s now time to conduct a detailed ground investigation. This typically involves drilling boreholes at strategic locations across the site to collect soil samples, which can then be analysed to assess the include soil type, density, moisture content, shear strength, and compaction.

Once the soil samples have been collected, various tests are conducted to assess their suitability for piling. These tests may include:

• The Standard Penetration Test (SPT): This effectively measures the soil’s resistance to penetration by a standard sampling spoon. It’s a good way of getting an idea of the soil’s relative density and strength.
• Cone Penetration Test (CPT): The CPT involves pushing a cone-shaped probe into the ground at a constant rate, again to measure soil resistance. This test provides valuable data on soil consistency and bearing capacity.
• Plate Load Test: The plate load test applies a known load to a steel plate, which is then placed on the ground surface to measure the soil’s bearing capacity. This test is particularly useful for assessing “cohesive soils” – soil types that stick together and form lumps or clumps when moistened, such as clay or silt.
• Soil Permeability Test: This determines the rate at which water can flow through the soil, which is crucial for assessing groundwater conditions and potential drainage issues. Ideally, soils with lower permeability are better for construction, as they tend to be stronger, more stable, and more resistant to erosion, compared with high-permeability soils.

Once the testing is complete, we’re then ready to move on to interpretation and analysis of the results.

Step 3: Interpretation and Analysis

Once the soil test results are available, the next stage is to look for patterns and trends in the soil properties, which can help us to understand how they may impact piling operations. At this stage, it’s crucial to consider factors such as soil bearing capacity, settlement potential, and the presence of any weak or problematic layers. Additionally, suitability of different piling techniques all need to be evaluated based on the soil conditions.

Now, interpreting soil test results requires not just a skilled eye and expertise, but also careful consideration of various factors. For example, as we’ve touched on above, cohesive soils like clay may require different piling techniques compared to granular soils like sand. That means it’s vital to assess the soil’s strength, compressibility, and permeability to determine the most appropriate approach.

It’s at this point where we’ll also need to take into account the environmental implications of any piling operations. If there’s any risk of soil contamination (especially in the presence of any protected habitats), then the project may require special measures to minimise the environmental impact, such as establishing buffer zones around vulnerable areas, or taking steps to ensure water quality protection – potentially including silt fences and sediment traps – to reduce the risk of harmful runoffs to surrounding flora and fauna.

It may also be worth consulting with local authorities, to ensure peace of mind in terms of compliance with all regulatory requirements (such as planning permission laws).

Step 4: Design Considerations

Based on the findings of the soil assessment, we’re now ready to develop a suitable piling design that accounts for the specific soil conditions on-site.

The details of the data and findings so far will all help to influence the pivotal choices of the appropriate piling technique, length, and diameter to ensure adequate support for the structure. That also means considering factors such as pile loadings, settlement tolerances, and environmental constraints. The input of geotechnical engineers or soil specialists can be especially useful at this stage, helping to refine the design and address any challenges identified during the assessment.

Of course, there may be some minor variations in this process from project to project, depending on what the situation demands – but that’s the procedure in a nutshell! And if you’ve got any more specific questions that we’ve not covered above, or you need some general advice, you’re in exactly the right place.

We have around 15 years of experience behind us at Vxcel Piling, we have a long history of delivering exceptional results for customers across a range of sectors, including domestic projects, commercial properties, and industrial warehouses. To find out what we’ve achieved for previous customers, feel free to take a look through our case studies. Alternatively, if you’re ready to get started – if you’ve got any questions – don’t hesitate to give us a call on 01254 314010, and we’ll be happy to see how we can help!