--- title: "EGS and its main parameters" subject: "Engineering Geology II" chapter: 1 key: "semester_4/engineering_geology_ii:egs-parameters" source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/egs-parameters site: BCT Engineering --- # EGS and its main parameters Engineering Geology II · Chapter 1: Introduction to Engineering Geology - Asked in: 2079 Asoj, 1 marks; 2079 Jestha, 1 marks; 2075 Bhadra, 1.5 marks; 2072 Magh, 3 marks; 2070 Magh, 2 marks; 2068 Bhadra, 1.5 marks (asked 6 times) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/egs-parameters - Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-1 ## Question What is the engineering geological system (EGS)? What are the main parameters for its evaluation? ## Short answer EGS is the interacting system of the geological environment (rock, soil, water, relief, processes) and the proposed structure. Main evaluation parameters include lithology, structure, weathering, physical/mechanical properties, rock mass quality, hydrogeology, geomorphology, geodynamic hazards, in-situ stress, and construction material availability. ## Answer The **engineering geological system (EGS)** is the combination of the geological environment (rock, soil, structure, water, relief and processes) and the proposed engineering structure, treated as one interacting system. The structure changes the ground, and the ground controls the safety and cost of the structure. #### Main parameters for evaluation 1. **Lithology:** rock/soil type, grain size, mineral composition, hardness. 2. **Geological structure:** bedding, joints, faults, folds, shear zones; their orientation, spacing, persistence, aperture and infilling. 3. **Weathering and alteration:** degree and depth of weathering. 4. **Physical and mechanical properties:** density, porosity, strength, deformability, slake durability, swelling. 5. **Rock mass quality:** RQD, RMR, Q and GSI classification. 6. **Hydrogeology:** water table, permeability, seepage, springs, pore pressure. 7. **Geomorphology and slope conditions:** slope angle, drainage, overburden thickness, landslide features. 8. **Geodynamic processes and hazards:** landslide, erosion, flood, seismicity, active faults. 9. **In-situ stress and temperature** (for deep tunnels). 10. **Construction materials availability.** ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does the engineering geological system (EGS) treat as one interacting system? A. Rock and soil only B. The geological environment and the proposed structure C. The structure and its cost D. Climate and vegetation only Answer: B. EGS combines the geological environment with the engineering structure: the structure changes the ground and the ground controls safety and cost. (Key point: EGS meaning) 2. Which are used to express rock mass quality in EGS evaluation? A. RQD, RMR, Q and GSI B. pH and turbidity C. Plasticity and liquid limit only D. Slump and flow Answer: A. Rock mass quality is classified using RQD, RMR, Q and GSI. (Key point: Rock mass quality) 3. Which discontinuity properties are evaluated under geological structure? A. Colour and taste B. Orientation, spacing, persistence, aperture and infilling C. Only the age D. Only the mineral names Answer: B. Joints, faults and folds are judged by orientation, spacing, persistence, aperture and infilling. (Key point: Structure parameters) 4. Which parameter is specifically relevant for deep tunnels? A. Grain size of river sand B. Landslide scars on slopes C. Construction material availability D. In-situ stress and temperature Answer: D. Deep tunnels face high in-situ stress and temperature, so these are evaluated. 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