--- title: "Types and methods of site investigation" subject: "Engineering Geology II" chapter: 4 key: "semester_4/engineering_geology_ii:site-investigation-methods" source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/site-investigation-methods site: BCT Engineering --- # Types and methods of site investigation Engineering Geology II · Chapter 4: Engineering geology in site selection, investigation & construction/excavation - Asked in: 2081 Chaitra, 1.5 marks; 2078 Poush, 3 marks; 2072 Magh, 3 marks; 2070 Magh, 3 marks; 2070 Bhadra, 4 marks; 2069 Poush, 4 marks; 2068 Magh, 1 marks (asked 7 times) - Video: [Field Investigation of Soil and Rock | Boreholes, Geological Maps, SPT, DCP and Piezometers](https://www.youtube.com/watch?v=ein1o9qePK4) — Soil Mechanics and Engineering Geology - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/site-investigation-methods - Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-4 ## Question Describe the types and methods of site investigation. ## Short answer Site investigation uses surface methods (geological mapping, remote sensing) and sub-surface methods (test pits, boreholes, geophysical surveys like seismic refraction and electrical resistivity). In situ and lab tests provide engineering properties, and results are compiled in logs and reports. ## Answer Site investigation is carried out in stages (reconnaissance, preliminary, detailed) using surface and sub-surface methods. #### A. Surface investigation 1. **Direct methods:** field geological mapping, traversing, measurement of strike/dip and joints, outcrop study, geomorphological mapping, study of existing cuts and landslides. 2. **Indirect methods:** study of topographic maps, aerial photographs and satellite images (remote sensing), GIS, and review of earlier reports. #### B. Sub-surface investigation 1. **Direct methods:** - *Test pits and trenches:* to 3-5 m depth; for soil and shallow rock. - *Shafts, adits and drifts:* to inspect rock in tunnels and dam abutments. - *Boring (auger, wash, percussion) and core drilling:* to get samples and rock quality (RQD); depth as required. - *Sampling:* disturbed and undisturbed samples. 2. **Indirect methods:** geophysical exploration: - Seismic refraction (depth of bed rock, velocity), - Electrical resistivity (soil/rock layers, groundwater), - Gravity, magnetic and ground penetrating radar. #### C. In-situ and laboratory tests Standard penetration test, plate load test, permeability (Lugeon/packer) test, shear test, rock mechanics tests and soil tests. #### D. Reporting Logs, geological sections, maps and recommendations. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which is an indirect surface method? A. Study of aerial photographs and satellite images B. Field geological mapping C. Measurement of strike and dip D. Outcrop study Answer: A. Maps, photos, remote sensing and GIS are indirect; mapping and outcrop study are direct. (Key point: Direct vs indirect surface) 2. What depth are test pits and trenches normally used to? A. About 100 m B. About 3-5 m C. Over 500 m D. Only 0.1 m Answer: B. They suit soil and shallow rock. (Key point: Test pits) 3. What does core drilling give? A. Only surface maps B. Gravity anomalies C. Rock samples and rock quality (RQD) D. Wave velocity only Answer: C. Cores are logged for RQD and tested in the lab. (Key point: Core drilling) 4. Which method detects depth to bed rock and velocity? A. Plate load test B. Test pit C. Vane shear D. Seismic refraction Answer: D. Seismic refraction gives velocities and layer depths; it is an indirect sub-surface method. (Key point: Geophysical methods) ## Related in Engineering Geology II - [Purposes of site investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asite-investigation-purposes) — Engineering Geology II, chapter 4, asked 7× - [Detail stage of EG site investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Adetail-stage-investigation) — Engineering Geology II, chapter 4 - [Tunneling and site investigation process](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Atunneling-site-investigation-process) — Engineering Geology II, chapter 4 - [Direct methods of sub-surface investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Adirect-subsurface-methods) — Engineering Geology II, chapter 4, asked 3× - [Surface versus sub-surface investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asurface-vs-subsurface-investigation) — Engineering Geology II, chapter 4, asked 3× - [Indirect methods of surface investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aindirect-surface-methods) — Engineering Geology II, chapter 4 ## Related in other subjects - [Contents of site investigation report](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Asite-investigation-report) — Foundation Engineering, chapter 2, asked 5× - [Methods of surface and subsurface site investigation](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Amethods-of-surface-and-subsurface) — Engineering Geology I, chapter 1, asked 4× - [Engineering geological map and site investigation](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aengineering-geological-map-and-site) — Engineering Geology I, chapter 1, asked 3× - [Site investigation for dam and reservoir](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Asite-investigation-for-dam-and) — Engineering Geology I, chapter 1, asked 2×