1. Objective and Scope
The purpose of this investigation is to determine the physical and mechanical properties of subsurface materials — including soil, rock, and groundwater — to provide safe, cost-effective, and technically sound design parameters for civil and infrastructure projects.
Scope Includes:
• Borehole drilling and soil sampling
• In-situ testing (SPT, CPT, Vane Shear, Plate Load)
• Laboratory testing (Index and Strength tests)
• Geophysical survey (Seismic and Electrical)
• Correlation, data analysis, and engineering reporting

2. Preparation and Planning Phase
• Review existing geological and geotechnical data.
• Define investigation objectives (foundation, slope, embankment, etc.).
• Determine borehole and test pit locations based on site layout.
• Establish survey control points and benchmarks.
• Prepare safety plan and environmental risk assessment (HSE compliance).
• Mobilize drilling, geophysical, and laboratory teams with required equipment.

3. Geotechnical Field Investigation
3.1 Borehole Drilling
• Perform boreholes using rotary or percussion rigs.
• Standard borehole diameter: 100–150 mm.
• Record lithology, strata changes, and groundwater levels.
• Use casing to prevent borehole collapse.
• Maintain detailed borehole logs every 0.5 m depth interval.
3.2 Soil Sampling
• Undisturbed samples: taken using Shelby tubes and piston samplers.
• Disturbed samples: obtained using split-spoon samplers.
• Label, seal, and transport samples properly to the laboratory.
3.3 In-Situ Testing
Test Purpose Frequency
Standard Penetration Test (SPT) Soil resistance Every 1.5 m or at strata change
Cone Penetration Test (CPT) Continuous soil profile As required
Vane Shear Test Cohesive soil strength Selected boreholes
Plate Load Test Bearing capacity Foundation locations
Field Permeability Hydraulic conductivity Where groundwater exists

4. Test Pit Excavation
• Excavate 2–3 m deep pits for visual soil classification.
• Record color, consistency, and stratification.
• Take disturbed and undisturbed samples.
• Backfill and compact the pit after completion.

5. Laboratory Testing
All laboratory tests are performed under ASTM/BS standards in an accredited lab.
Tests Include:
• Index Tests: Moisture content, Atterberg limits, grain size analysis.
• Mechanical Tests: Direct shear, triaxial, UCS.
• Consolidation: Settlement characteristics by oedometer.
• Chemical: Sulfate, chloride, pH, organic content.
• Rock Tests: UCS, point load, porosity, and density.

6. Geophysical Investigation
6.1 Objective
To provide continuous subsurface profiling between boreholes and identify anomalies such as cavities, rock interface, and groundwater zones.
6.2 Techniques
Method Purpose Typical Depth
Seismic Refraction Bedrock depth and seismic velocity 0–50 m
MASW (Surface Waves) Shear wave velocity (Vs30) 0–30 m
Electrical Resistivity Tomography (ERT) Layer thickness and groundwater 0–100 m
Ground Penetrating Radar (GPR) Shallow utilities and voids 0–5 m
6.3 Field Procedure
• Establish survey lines and sensor spacing (2–5 m).
• Calibrate instruments and verify baseline noise.
• Inject seismic/electrical signals and record responses.
• Repeat with multiple arrays for data consistency.
6.4 Data Processing
• Process data using SeisImager, RES2DINV, or equivalent.
• Apply filtering and inversion to model subsurface layers.
• Generate 2D/3D profiles and correlate with borehole logs.

7. Data Integration and Interpretation
• Integrate borehole and geophysical datasets.
• Develop engineering parameters:
o Bearing capacity (qₐ)
o Elastic modulus (Eₛ)
o Shear strength (c, φ)
o Groundwater level (GWT)
• Identify weak layers, cavities, and fill zones.
• Create 2D/3D geotechnical models for design applications.

8. Reporting and Deliverables
Deliverables Include:
• Borehole logs and cross-sections (PDF/DWG).
• Laboratory test results and certificates.
• Geophysical interpretation maps and profiles.
• Foundation and design recommendations.
• Final Geotechnical & Geophysical Investigation Report (GGIR).

9. Equipment and Software
Field Equipment: Rotary drilling rig, CPT unit, SPT hammer, vane tester, geophones, resistivity meter.
Laboratory: Oedometer, triaxial cell, direct shear, sieves, pH meters.
Software: GEO5, PLAXIS, RocScience, Surfer, RES2DINV, ArcGIS.

10. Health, Safety, and Environment (HSE)
• Conduct HIRA and toolbox meetings daily.
• Provide PPE and secure borehole perimeters.
• Manage drilling fluids and waste safely.
• Ensure proper sample handling, transport, and disposal.