Foundations and Geotechnical Inspection

In accordance with EN 1997-1 (Section 3), EN 1997-2 and NTC 2018 (Chapter 6.2.2), geotechnical investigations must be planned and executed to adequately characterise the subsoil. NTC 2018 requires the preparation of the Geological Report and the Geotechnical Report. In-situ tests (SPT, CPT, pressuremeter tests) and laboratory tests must comply with EN ISO 22476 and UNI CEN ISO/TS 17892.

1. Verify availability of the Geological Report and Geotechnical Report as required by NTC 2018

2. Check that the number and depth of boreholes are adequate for the geotechnical category of the work (EN 1997-1 Section 2.1)

3. Verify that subsoil conditions encountered during excavation match those predicted in the geotechnical report

4. Check groundwater level and its correspondence with investigation data

5. In case of unexpected conditions, verify that the designer has been informed and the design reassessed

6. Verify seismic subsoil classification (categories A-E per NTC 2018 Chapter 3.2.2)

- Geotechnical investigations insufficient in extent or depth

- Subsoil conditions different from those predicted in the geotechnical report

- Groundwater at a level different from the design assumption

- Missing seismic subsoil classification per NTC 2018

- Missing mandatory Geological or Geotechnical Report

In accordance with EN 1997-1 (Section 6) and NTC 2018 (Chapter 6.4), shallow foundations (isolated footings, strip footings, rafts) must be designed and verified for ultimate limit states (bearing capacity) and serviceability limit states (settlement). Execution must comply with EN 13670 for concrete and design specifications.

1. Verify the formation level against the design and the suitability of the foundation soil (no topsoil, no uncontrolled fill)

2. Check excavation dimensions (width, length, depth) against execution drawings

3. Verify the blinding layer (thickness, concrete class) and its correct execution

4. Check foundation reinforcement (diameter, spacing, cover) before casting

5. Verify protection of excavation from water infiltration and frost during construction

6. Monitor foundation settlement during and after construction, if required by design (topographic monitoring)

- Formation on disturbed, uncompacted soil or organic material present

- Excavation beyond design depth with uncontrolled backfill

- Water infiltration in excavation not adequately managed

- Insufficient cover on the underside of the foundation

- Failure to verify bearing capacity of soil at formation level

In accordance with EN 1997-1 (Section 7), NTC 2018 (Chapter 6.4.3), EN 1536 (bored piles), EN 12699 (driven piles) and EN 14199 (micropiles), pile foundations must be designed, executed and verified per applicable standards. Pile load tests (static per EN ISO 22477 or dynamic) must be included in the quality control plan.

1. Verify the plan and elevation position of each pile against the design (tolerances per EN 1536 or EN 12699)

2. Check execution parameters for each pile: depth reached, concrete volumes, driving or boring records

3. For bored piles (EN 1536), verify toe cleaning, reinforcement placement and concrete casting (tremie method if water present)

4. For driven piles (EN 12699), check driving records (blows/cm, energy) and verify pile integrity

5. Verify execution of load tests (static or dynamic) per quality control plan and compliance with acceptance criteria

6. Check integrity tests (PIT, CSL) on the required percentage of piles

- Piles not reaching design depth or bearing stratum

- Plan deviation or inclination of piles beyond permitted tolerances

- Integrity defects (necking, soil inclusions) in bored piles

- Concrete volume significantly different from theoretical volume

- Load test results not meeting acceptance criteria

In accordance with EN 1997-1 (Section 9) and NTC 2018 (Chapter 6.5), retaining walls must be verified for overturning, sliding, bearing capacity and overall stability limit states. Earth pressures must be calculated per EN 1997-1 Annex C. Execution must comply with design specifications and applicable execution standards.

1. Verify geometric dimensions of the wall (height, thickness, foundation) against execution drawings

2. Check reinforcement of foundation, stem and toe (if present) before casting

3. Verify installation of drainage system behind the wall: drainage material, drainage pipe, separator geotextile

4. Check presence and functioning of weep holes through the wall

5. Verify waterproofing of the wall face in contact with soil, if required by design

6. Check backfill behind the wall: layer compaction, material type, absence of expansive clay

- Drainage system missing or non-functional, with hydrostatic pressure build-up

- Backfill with unsuitable material or insufficient compaction

- Missing waterproofing of the earth-retaining face

- Weep holes blocked or missing

- Wall cracking due to differential settlement or pressures exceeding design values