Foundations and Geotechnical Inspection

Per EN 1997-1 Section 3 and EN 1997-2, a geotechnical investigation must be carried out to determine ground conditions. The investigation scope depends on Geotechnical Category (GC1, GC2, GC3). For GC2 and GC3, boreholes, CPTs, or trial pits are required. Soil parameters must be derived per EN 1997-2.

1. Verify geotechnical investigation report exists and covers the site

2. Check borehole/CPT locations and depths are adequate for the structure

3. Confirm soil parameters used in design match investigation results

4. Verify groundwater level has been established and monitored

5. Check for contamination or problematic soils (peat, expansive clay, fill)

- Insufficient investigation depth — missing weak layers below foundation level

- Groundwater level higher than assumed in design

- Undetected fill or contaminated ground

- Soil parameters not representative — too few test points

Per EN 1997-1 Sections 6, shallow foundations must be verified for bearing resistance (ULS) and settlement (SLS). Formation level must be inspected to confirm soil matches design assumptions. Blinding concrete must be placed promptly to protect exposed soil. Dimensions and levels must comply with design tolerances.

1. Inspect formation level — soil must match geotechnical report (visual + hand tests)

2. Verify foundation dimensions (length, width, depth) match structural drawings

3. Check formation level is at correct depth below ground level

4. Confirm blinding concrete is placed before reinforcement

5. Verify no water ingress or softened soil at formation level

- Formation soil softer than expected — bearing capacity insufficient

- Excavation left open too long — soil softened by weather or groundwater

- Foundation dimensions or levels not matching design

- Over-excavation backfilled with unsuitable material

Per EN 1997-1 Section 7, pile design must be verified by static load tests, dynamic testing, or calculation from ground test results. Execution of bored piles per EN 1536, displacement piles per EN 12699. Pile integrity testing per EN ISO 22476 series. Pile position tolerance is typically ±75mm (EN 1536).

1. Verify pile installation records — depth, driving resistance or concrete volume

2. Check pile positions against layout — tolerance ±75mm per EN 1536

3. Review pile integrity test results (sonic echo, cross-hole, or equivalent)

4. Verify static or dynamic load test results against design capacity

5. Inspect pile heads after trimming — no damage, correct level for pile cap

- Piles not reaching design depth or bearing stratum

- Pile shaft defects (necking, inclusions) in bored piles

- Excessive pile positional deviation requiring redesign of pile caps

- Insufficient load test results to verify capacity

Per EN 1997-1 Section 9, retaining structures must be verified for overall stability, bearing, sliding, and overturning. Earth pressures must be calculated per EN 1997-1 Annex C. Drainage behind retaining walls is essential to prevent hydrostatic pressure buildup. Wall movements must be monitored during and after construction.

1. Verify wall dimensions and reinforcement match design

2. Check drainage system behind wall — filter fabric, drainage layer, weep holes or drain pipes

3. Confirm backfill material is suitable and compacted in layers (≤300mm)

4. Verify wall verticality and alignment within tolerance

5. Check for signs of excessive movement, cracking, or tilting

- Blocked or missing drainage — hydrostatic pressure causes wall failure

- Unsuitable backfill material (clay instead of granular)

- Backfill compaction too close to wall causing lateral overload

- Surcharge loads not accounted for in design