--- title: "Geological problems in tunnel construction" subject: "Engineering Geology II" chapter: 4 key: "semester_4/engineering_geology_ii:tunnel-construction-problems" source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/tunnel-construction-problems site: BCT Engineering --- # Geological problems in tunnel construction Engineering Geology II · Chapter 4: Engineering geology in site selection, investigation & construction/excavation - Asked in: 2079 Asoj, 2 marks; 2078 Baisakh, 3 marks; 2072 Magh, 3 marks (asked 3 times) - Video: [Tunnel Geology: Geological Aspects in Underground Engineering](https://www.youtube.com/watch?v=7cfHGaocc1s) — earthscience classes official - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/tunnel-construction-problems - Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-4 ## Question Describe the various geological problems that occur during tunnel construction. ## Short answer Main problems: rock fall/overbreak in jointed rock, squeezing in weak rock under high overburden, swelling clays, rock bursts in hard brittle rock, heavy water inflow from faults and karst, running ground, gas, and portal instability. Solutions include pre-investigation, grouting, rock bolts, shotcrete, and controlled advance. ## Answer Tunnel construction in the Himalaya meets many geological problems, which depend on the rock mass, structure, water and stress. 1. **Rock fall and roof collapse (overbreak):** in highly jointed, blocky or weak rock, wedges fall from the crown; worst when joints dip steeply and the tunnel axis is parallel to strike. 2. **Squeezing ground:** weak rocks (phyllite, schist, shale, clay-rich shear zones) under high overburden deform slowly into the opening, closing it; needs yielding support. 3. **Swelling ground:** clay minerals (montmorillonite) and anhydrite swell with water and damage lining. 4. **Rock burst and spalling:** in brittle, hard rock (granite, gneiss, quartzite) under high stress, the rock breaks violently; common under high overburden in the Higher Himalaya. 5. **Water inflow and flooding:** fault zones, karst cavities and fractured rock give heavy inflow and high pressure; wash out infill, causing flow of sand and collapse. 6. **Faults, shear zones and thrusts:** crushed rock with low strength; collapses and big water flow (MBT, MCT). 7. **Running and flowing ground:** loose sand or saturated silt flows into the face. 8. **Karst cavities** in limestone and dolomite. 9. **Gas and high temperature:** methane, hydrogen sulphide, hot water. 10. **Portal instability:** landslides and rock fall at the entry. 11. **Abrasive rock** (quartzite) wears cutters in TBM. **Remedies:** pre-investigation, probe drilling, forepoling, pipe-roof, grouting, systematic rock bolts and shotcrete, steel ribs, drainage, yielding support and a controlled advance rate. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Squeezing ground occurs in A. Hard granite at low cover B. Dry sandstone C. Weak rocks such as phyllite, schist or shale under high overburden D. Quartzite only Answer: C. Weak rock deforms slowly into the opening. (Key point: Squeezing) 2. Rock burst is typical of A. Soft clay B. Loose sand C. Karst limestone only D. Brittle hard rock under high stress Answer: D. Hard rock stores strain and breaks violently. (Key point: Rock burst) 3. What causes swelling ground? A. Clay minerals such as montmorillonite and anhydrite taking water B. Quartz grains C. Granite D. Dry calcite Answer: A. Swelling damages the lining. (Key point: Swelling) 4. Which is a remedy? A. Ignoring water B. Probe drilling, grouting, rock bolts, shotcrete and yielding support C. Increasing advance rate D. Removing support Answer: B. These manage unstable ground. (Key point: Remedies) ## Related in Engineering Geology II - [Geological investigation of tunnel and road](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Atunnel-road-investigation) — Engineering Geology II, chapter 4 - [Overbreak and tunnel geological survey](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aoverbreak-tunnel-survey) — Engineering Geology II, chapter 4 - [Engineering geological problems of Siwalik zone](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asiwalik-problems) — Engineering Geology II, chapter 2, asked 4× - [Mitigation of geological problems in Himalaya](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Ahimalaya-problems-mitigation) — Engineering Geology II, chapter 2 - [Geological documentation in tunnelling](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Atunnel-geological-documentation) — Engineering Geology II, chapter 4, asked 6× - [Geology in tunnel site selection](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Atunnel-site-selection) — Engineering Geology II, chapter 4, asked 4× ## Related in other subjects - [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× - [Need for insurance during construction](https://www.bctengineer.com/question.md?key=semester_8%2Fconstruction_management%3Ainsurance-during-construction) — Construction Management, chapter 11 - [Design and construction problems of hill roads](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ahill-problems) — Transportation Engineering I, chapter 5, asked 11× - [Discontinuities and engineering problems in Nepal Himalaya](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Adiscontinuities-and-engineering-problems-in) — Engineering Geology I, chapter 7