Foundations and Geotechnical Inspection

In accordance with EN 1997-1 Section 3, EN 1997-2 and NF P 94-500, 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, CPT tests or trial pits are required. Soil parameters must be determined per EN 1997-2. NF P 94-500 defines the geotechnical missions (G1 to G4) specific to the French framework.

1. Verify that the geotechnical investigation report exists and covers the project site

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

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

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

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

- Insufficient investigation depth — weak layers not detected below foundation level

- Groundwater level higher than assumed in the design

- Fill or contaminated soils not identified

- Soil parameters not representative — insufficient number of test points

In accordance with EN 1997-1 Section 6, shallow foundations must be verified for bearing resistance (ULS) and settlement (SLS). The formation level must be inspected to confirm that the soil matches the design assumptions. Blinding concrete must be cast promptly to protect exposed soil. Dimensions and levels must comply with design tolerances.

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

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

3. Check that the formation level is at the correct depth below natural ground level

4. Confirm that blinding concrete is cast before reinforcement placement

5. Verify the absence of 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 not matching design

- Over-excavation backfilled with unsuitable material

In accordance with EN 1997-1 Section 7, pile design must be verified by static load tests, dynamic tests or calculation from ground investigation results. Execution of bored piles per EN 1536, driven piles per EN 12699. Pile integrity testing per EN ISO 22476 series. Positional tolerance is typically +/-75 mm (EN 1536). NF P 94-262 (national application standard for Eurocode 7) specifies the design rules for deep foundations.

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

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

3. Review integrity test results (sonic testing, logging 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

- Shaft defects (necking, inclusions) in bored piles

- Excessive positional deviation requiring pile cap redesign

- Insufficient number of load tests to verify capacity

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

1. Verify wall dimensions and reinforcement against design

2. Check drainage system behind wall — filter geotextile, drainage layer, weep holes or drains

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

4. Verify wall plumbness and alignment within tolerances

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

- Blocked or missing drainage — hydrostatic pressure causes wall failure

- Unsuitable backfill material (clay instead of granular material)

- Backfill compaction too close to wall causing lateral overload

- Surcharges not accounted for in design