Ground investigation items are included in the BOQ to cover the exploration, sampling, testing, and reporting of subsurface conditions before or during construction.
This class ensures that the contractor accounts for all activities related to site geotechnical study so that the Employer and Engineer have reliable soil/rock data.
1. Purpose of Ground Investigation Items
- To determine soil and rock properties for design and construction.
- To evaluate bearing capacity, groundwater conditions, and soil stratification.
- To provide standardized measurement rules so all tenders are comparable.
- To separate site investigation costs from construction works.
2. Subdivision of Ground Investigation (as per CESMM4)
Ground Investigation is generally divided into:
B1. Trial Pits
- Hand-dug or machine-dug pits to inspect soil layers.
- Depth usually up to 3–5 m.
- Used for visual inspection, sampling, groundwater observation.
- Measurement unit: m³ of excavation or Each (No.) pit.
B2. Boreholes
- Vertical drilling for soil/rock sampling.
- Methods: auger, rotary, percussion, wash boring.
- Cased/un-cased boreholes measured separately.
- Measurement unit: Linear metre (m) depth drilled.
B3. In-situ Tests
Performed inside boreholes or trial pits. Examples:
- SPT (Standard Penetration Test) – blow counts for soil resistance.
- DCPT (Dynamic Cone Penetration Test).
- Vane Shear Test – for soft clays.
- Pressuremeter Test.
- Permeability Test (falling head, pumping).
- Measurement unit: Each (No.) test.
B4. Sampling
- Disturbed Samples – collected by auger/spade, not intact.
- Undisturbed Samples – thin-walled tubes (Shelby tube, piston sampler).
- Rock Cores – extracted using core barrels.
- Measurement unit: Each (No.) sample or m length of core.
B5. Laboratory Testing
- Soil: grain size analysis, Atterberg limits, compaction, triaxial, CBR, consolidation.
- Rock: UCS (Unconfined Compressive Strength), water absorption, point load test.
- Chemical: sulphates, chlorides, organic content.
- Measurement unit: Each (No.) test.
B6. Groundwater Observations
- Standpipes, piezometers, water table recording.
- Pumping tests for aquifer properties.
- Measurement unit: Each (No.) installation or per test.
B7. Reporting
- Preparation of factual/geotechnical reports.
- Logs, charts, lab results, interpretations.
- Usually measured as Lump Sum (LS).
3. Measurement Rules (CESMM4 Principles)
- Borehole depth is measured from ground level to final depth.
- Casing is measured separately.
- Sampling is recorded separately from drilling.
- Tests are measured by type and frequency.
- Reporting is always lump sum unless specified.
4. Example BOQ for Class B
| Item No. | Description | Unit | Quantity | Rate | Amount |
|---|---|---|---|---|---|
| B1.1 | Excavation of trial pits up to 3.0 m depth including backfilling | No. | 6 | … | … |
| B2.1 | Rotary drilling of boreholes up to 20 m depth, uncased | m | 120 | … | … |
| B2.2 | Supply and installation of casing for boreholes | m | 50 | … | … |
| B3.1 | Standard Penetration Tests (SPT) at 1.5 m intervals | No. | 40 | … | … |
| B4.1 | Collection of undisturbed soil samples (100 mm diameter) | No. | 20 | … | … |
| B4.2 | Rock core recovery (NX size) | m | 30 | … | … |
| B5.1 | Laboratory grain size distribution tests | No. | 15 | … | … |
| B5.2 | Laboratory triaxial tests on soil samples | No. | 6 | … | … |
| B6.1 | Installation of standpipe piezometers | No. | 5 | … | … |
| B7.1 | Preparation of factual geotechnical investigation report | LS | 1 | … | … |
5. Site Example
👉 Suppose you are constructing a highway bridge foundation:
- Trial pits help to inspect near-surface soils.
- Boreholes give deep strata details (say 20 m depth).
- SPT tests confirm bearing strata.
- Undisturbed samples taken for lab CBR tests.
- Piezometers measure seasonal groundwater fluctuations.
- A final report is issued for foundation design.
✅ In short:
Class B (Ground Investigation) in CESMM4 provides a structured way to measure all geotechnical investigation works including pits, boreholes, sampling, in-situ & lab testing, groundwater monitoring, and reporting.
