Foundations and Geotechnical Inspection

In accordance with EN 1997-1 Section 3, EN 1997-2 and DIN 4020, a geotechnical investigation must be carried out to determine ground conditions. The scope of investigation depends on the Geotechnical Category (GC1, GC2, GC3). For GC2 and GC3, boreholes, cone penetration tests (CPT) or trial pits are required. Soil parameters must be derived in accordance with EN 1997-2.

1. Verify the existence and completeness of the geotechnical investigation report for the site

2. Check the location and depth of explorations (boreholes, CPT) for adequacy relative to the structure

3. Confirm that soil parameters used in the design match the investigation results

4. Verify that the groundwater level has been determined and monitored

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

- Insufficient investigation depth — soft layers below the foundation level not identified

- Groundwater level higher than assumed in the design

- Unidentified fill or contaminated ground

- Soil parameters not representative — too few investigation points

In accordance with EN 1997-1 Section 6 and DIN EN 1997-1/NA, shallow foundations must be verified for bearing resistance (ULS) and settlement (SLS). The formation level must be inspected to confirm that ground conditions match the 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 the geotechnical report (visual inspection + hand tests)

2. Check foundation dimensions (length, width, depth) against structural drawings

3. Verify formation level at correct depth below ground level

4. Confirm blinding concrete placed before reinforcement fixing

5. Ensure no water ingress or softened soil at the formation level

- Soil at formation level softer than expected — bearing capacity insufficient

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

- Foundation dimensions or levels deviate from design

- Over-excavation backfilled with unsuitable material

In accordance with EN 1997-1 Section 7 and DIN EN 1997-1/NA, pile design must be verified by static load tests, dynamic tests or calculation from ground investigation results. Execution of bored piles per EN 1536, displacement piles per EN 12699. Pile integrity testing per EN ISO 22476 series. Pile positional tolerance is typically +/-75 mm (EN 1536).

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

2. Check pile positions against pile layout — tolerance +/-75 mm per EN 1536

3. Evaluate pile integrity test results (low-strain impact, crosshole or equivalent)

4. Compare static or dynamic load test results with design capacity

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

- Piles do not reach design depth or bearing stratum

- Shaft defects (necking, inclusions) in bored piles

- Excessive positional deviation requires redesign of pile caps

- Insufficient load test results for capacity verification

In accordance with EN 1997-1 Section 9 and DIN EN 1997-1/NA, retaining structures must be verified for overall stability, bearing capacity, sliding and overturning. Earth pressure must be calculated in accordance with EN 1997-1 Annex C and DIN 4085. Drainage behind retaining walls is essential to prevent hydrostatic pressure build-up. Wall movements must be monitored during and after construction.

1. Check wall dimensions and reinforcement against design

2. Inspect drainage system behind wall — filter geotextile, drainage layer, weep holes or drainage pipes

3. Check backfill material for suitability and compaction in layers (<=300 mm)

4. Verify plumbness and alignment of wall within tolerances

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

- Blocked or missing drainage — hydrostatic pressure leads to wall failure

- Unsuitable backfill material (clay instead of granular material)

- Backfill compaction too close to wall causes excessive lateral pressure

- Surcharge loads not accounted for in design