Foundations and Geotechnical Inspection

In accordance with EN 1997-1 Section 3 and EN 1997-2, a geotechnical investigation must be carried out to determine ground conditions. The scope depends on the Geotechnical Category (GC1, GC2, GC3). For GC2 and GC3, boreholes, CPT or trial pits are required. Soil parameters must be derived per EN 1997-2. CTE DB SE-C establishes ground investigation requirements for building construction in Spain.

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

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

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

4. Verify that the water table has been established and monitored

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

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

- Water table higher than assumed in design

- Fill or contaminated soils not detected

- Soil parameters not representative — insufficient 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 the soil matches design assumptions. Blinding concrete must be placed promptly to protect exposed soil. Dimensions and levels must comply with design tolerances. CTE DB SE-C supplements these requirements.

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

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

3. Check formation level at correct depth below grade

4. Confirm blinding concrete is placed before reinforcement

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

- Soil at formation 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. Bored pile execution 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. Check pile installation records — depth, driving resistance or concrete volume

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

3. Review integrity test results (sonic echo, crosshole 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 load test results 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. CTE DB SE-C supplements these requirements.

1. Verify wall dimensions and reinforcement against design

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

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 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

- Surcharges not accounted for in design