--- title: "Engineering geological map and site investigation" subject: "Engineering Geology I" chapter: 1 key: "semester_3/engineering_geology_i:engineering-geological-map-and-site" source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/engineering-geological-map-and-site site: BCT Engineering --- # Engineering geological map and site investigation Engineering Geology I · Chapter 1: Geology and Civil Engineering - Asked in: 2065 Shrawan (old course), 3+5 marks; 2061 Baisakh (old course), 3+5 marks; 2066 Bhadra (old course), 2 marks (asked 3 times) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/engineering-geological-map-and-site - Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-1 ## Question Define topographic map, aerial photograph and engineering geological map. Write down the importance of the engineering geological map for site investigation. ## Short answer A topographic map shows surface relief with contours; an aerial photograph is an overhead image used for stereo interpretation. An engineering geological map depicts rock/soil types, structures, hazards and material sources on a topographic base. It guides borehole planning, identifies hazards, shows groundwater, and aids design of foundations and slopes. ## Answer #### Topographic map A **topographic map** shows the shape and relief of the ground surface using contour lines, and also natural and man-made features such as rivers, roads, settlements and vegetation, drawn to scale. It shows the surface only, not the rocks beneath. #### Aerial photograph An **aerial photograph** is a photograph of the ground taken from an aircraft (or drone) with the camera pointing vertically or obliquely downward. Overlapping pairs viewed under a stereoscope give a 3-D view. They are used to identify rock units, lineaments, faults, landslides, drainage patterns and land use, and to prepare base maps. #### Engineering geological map An **engineering geological map** is a map, made on a topographic base, that shows rock and soil types, their engineering properties, geological structures (dip, strike, folds, faults, joints), weathering, groundwater, slope stability, hazards and construction material sources, for use in civil engineering projects. #### Importance for site investigation 1. Shows the distribution and nature of foundation rocks and soils at one glance. 2. Helps to compare alternative sites or alignments quickly and cheaply. 3. Identifies hazards such as landslides, active faults, unstable slopes, swelling soil and flood zones. 4. Guides the planning of boreholes, trenches and geophysical lines, so that investigation is placed where it is needed. 5. Shows groundwater conditions, springs and seepage areas. 6. Locates sources of construction material. 7. Helps design slope cuts, foundations, tunnel support and drainage. 8. Serves as a permanent record for later stages and maintenance. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. A topographic map shows: A. Rock types and joints in detail B. Subsurface strata from boreholes C. Groundwater chemistry D. Relief of the ground surface by contours and surface features, not rocks beneath Answer: D. It shows the surface only. (Key point: Topographic map) 2. Overlapping pairs of aerial photographs viewed under a stereoscope give: A. A 3-D view B. A borehole log C. Rock strength D. Core recovery Answer: A. Stereo pairs produce a 3-D view useful for identifying features. (Key point: Aerial photograph) 3. An engineering geological map is made on: A. A borehole log base B. A topographic base C. A blank sheet with no scale D. A seismograph record Answer: B. It adds geological and engineering data over a topographic base. (Key point: Engineering geological map) 4. How does the engineering geological map help plan investigation? A. Replaces all drilling B. Gives exact bearing capacity C. Guides placement of boreholes, trenches and geophysical lines D. Is not needed after design Answer: C. It shows where investigation is needed so effort is placed efficiently. (Key point: Importance) ## Related in Engineering Geology I - [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× - [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× - [Site investigation for road construction](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Asite-investigation-for-road-construction) — Engineering Geology I, chapter 1 - [Engineering geological problems in tectonic divisions](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aengineering-geological-problems-in-tectonic) — Engineering Geology I, chapter 7, asked 2× - [Objectives of investigation for hill road](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aobjectives-of-investigation-for-hill) — Engineering Geology I, chapter 1 - [Geological agents and their geological work](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Ageological-agents-and-their-geological) — Engineering Geology I, chapter 6, asked 7× ## Related in other subjects - [Types of aerial photograph, scale relation](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aaerial-photo-types-scale-relation) — Surveying II, chapter 7 - [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