Geological Hazards in Tunneling MCQ with answer and solution

Concept

Geological Hazards in Tunneling

Formula

N/A

Step-by-step solution

1. Analyze the impact of various geological conditions on tunnel excavation. 2. Recognize that fractured rock combined with a high groundwater table causes major instability and severe flooding. 3. Select Option B as the correct choice.

Explanation

Crossing a zone of highly fractured rock with a high groundwater table causes major trouble because broken rock easily collapses during digging, and high water pressure causes heavy flooding, making excavation extremely dangerous and difficult.

Shortcut

To remember the worst geological condition for tunneling, use the mnemonic "Water + Cracks = Collapse & Floods": - Fractured Rock: Weakens structural stability, leading to cave-ins and collapses. - High Water Table: Adds heavy hydrostatic pressure, causing severe flooding and soil washing out. - Combination (Worst Hazard): Creates extreme instability and water inflow, posing a much higher danger than hard rock or dry conditions.

Common mistake

A common mistake is selecting Option C by assuming that extremely hard rock like quartzite causes the most trouble due to slow drilling progress and tool wear. In reality, hard rock mainly affects excavation speed, whereas highly fractured rock combined with high groundwater pressure (Option B) creates severe safety hazards like structural collapse and flooding. Another frequent mistake is selecting Option D by confusing bedding plane orientations and assuming perpendicular vertical bedding is unstable, when it is actually one of the most stable conditions for tunneling.