👷‍♂️ Civil Engineering That’s Built on the Science — Not on a Hunch

Most people think groundwork is just about shifting dirt and smoothing it out.

But real civil engineering doesn’t start with a machine.
It starts with science, regulation, and a process that guarantees strength, safety, and compliance.

🔬 The Process: How We Engineer and Calculate Compaction

When you are working with excavated sub soils.  It's important to understand what it is your working with.  Once excavated and re used they become engineered fill so proper classification helps determine the correct engineer fill procedure.  This includes layer thickness number of passes by the roller 

Here’s exactly how we determine the correct compaction method on every job:

1. Material Sampling & Grading Analysis

We begin by collecting a representative sample from the site and sending it for grading analysis using BS EN ISO 17892-4:2016.

This lab test identifies:

• Grain size distribution

• Moisture content

• Plasticity index

• Any potential for collapse, expansion or instability

2. Material Classification – Table 6/2

Using the results from the lab, we classify the material based on the Specification for Highway Works, Series 600 — Table 6/2:
“Grading Requirements for Acceptable Earthworks Materials.”

This table provides clear limits on what percentage of the material must pass through each sieve size (from 125 mm to 63 microns) to qualify it as:

• Class 1 (Granular fill)

• Class 2 (Cohesive fill)

• Class 6 (Selected cohesive/low-grade fill)

Correct classification here is crucial — it determines how the material will behave under compaction, especially under load or during freeze-thaw cycles.

3. Compaction Method Determination – Table 6/4

Once we know the material class, we then refer to Table 6/4 of Series 600:
“Method Compaction for Earthworks Materials – Plant and Methods.”

This table outlines:

• The type of compaction plant (e.g., smooth-wheeled roller, grid roller, tamping roller, pneumatic-tyred roller)

• The mass per metre width of roll or wheel

• The method of compaction to be used (Method 1 through 6)

• The minimum number of passes required

For example:
If we're compacting a Class 2 cohesive material using a smooth-wheeled roller >5400kg, Method 2 will require 8 passes at 150 mm layer depth to achieve compliance.

These aren’t guesses — they’re specs. Backed by regs.

4. Site Execution with Verification

With the classification and method locked in, we then deliver compaction to spec:

• The machine used matches the required plant type and mass

• The number of passes is counted and verified

• Moisture conditioning is applied if needed

• Spot checks or nuclear density testing are used where applicable

It’s a system.
And it works because we follow Specification for Highway Works, Series 600 to the letter.

👊 Why This Matters to You

When you’re building a slurry lagoon, a new yard, a menage or drainage system — your groundworks are everything.

If the foundation fails, everything above it is already compromised.

That’s why our approach is always:

✅ Engineered
✅ Compliant
✅ Tested
✅ Proven

Because you don’t get a second chance to do the base layer again.

📞 Ready to Build It Right?

We offer free site evaluations across Wales. No fluff. No upsells. Just honest engineering advice — with or without a contract.

✅ Want to check your subsoil?
✅ Wondering if your old yard needs re-compaction?
✅ Need help calculating the compaction for a new extension or yard?

We’ve got you.
📅 Book your free site visit here - www.pw-construction.co.uk/contact