This set of Engineering Geology Multiple Choice Questions & Answers (MCQs) focuses on “Geological Investigations”.
1. Selection of excavation method depends on
a) Type of rocks
b) Nature of rocks and ground
c) Texture of rocks and ground
d) Weather conditions of the place
Explanation: Choice of the right method will, therefore, be possible only when the nature of the rocks and the ground all along the alignment is fully known. This is one of the most important aim and object of geological investigations.
2. Which outline is preferred for weak rocks with unequal lateral pressure?
b) Horse-shoe shaped
d) Rectangular shaped
Explanation: In self-supporting and strong rocks, either, D-shape or horse-shoe shape may be conveniently adopted but these shapes would be practically unsuitable in soft ground or even in weak rocks with unequal lateral pressure. In those cases circular outline may be the first choice.
3. Lithology does not affect which parameter?
a) Type of tunnel
b) Method of tunnelling
c) Strength and extent of lining
d) Cost of the project
Explanation: Information regarding mineralogical composition, textures and structures of the rocks through which the proposed tunnel is to pass is of great importance in deciding: the method of tunnelling, the strength and extent of lining and, thus the cost of the project.
4. What occurs due to falling of big rock blocks or sides due to release of stresses during tunnelling?
a) Rock fall
b) Rock bursts
d) Water rush
Explanation: Rock bursts which occur due to falling of big rock blocks from roofs or sides due to release of stresses or falling of rock block along fractures already existing in these rocks often cause many accidents.
5. Pick the rock considered as soft rocks for tunnelling.
Explanation: Rocks considered as hard and crystalline are granites, syenites, gabbros, basalts and all the related igneous rocks, sandstones, limestones, dolomites, quartzites etc. However the soft rocks include, shales, friable and poorly compacted sandstones, chalk and porous varieties of limestones and dolomites, slates and phyllites with high degree of cleavage.
6. Which type of rocks require double lining, i.e., temporary and permanent lining?
a) Hard rocks
b) Crystalline rocks
c) Soft rocks
d) Non-crystalline rocks
Explanation: In most cases, the soft rocks are not self-supporting. Hence, temporary and permanent lining becomes necessary that would involve extra cost and additional time.
7. Which type of strata is rare in occurrence?
a) Vertical strata
b) Horizontal strata
c) Inclined strata
d) Jointed strata
Explanation: Horizontal strata are rare in occurrence for longer tunnels. If they are countered for small tunnels or short lengths of long tunnels, horizontally layered rocks might be considered quite favourable.
8. Layers dipping at angles up to 45° may be called
a) Moderately inclined strata
b) Steeply inclined strata
c) Half inclined strata
d) Semi-inclined strata
Explanation: The layers that dipping at angles up to 45° may be said as moderately inclined strata. The tunnel axis may be running parallel to the dip direction, at right angles to the dip direction or inclined to both dip and strike direction.
9. When can the rocks act as natural arch?
a) Tunnel axis parallel to dip direction
b) Tunnel axis normal to dip direction
c) Tunnel axis inclined to dip direction
d) Tunnel axis parallel to strike direction
Explanation: When the tunnel axis may be running parallel to the dip direction, the layers offer uniformly distributed load on the excavation. The arch action is said to happen, where the rocks at roof act as natural arches transferring the load onto sides.
10. In synclinal condition, low pressure areas are found at
Explanation: In anticlinal folds, loads of rocks at the crust are transferred by arch action to a great extent to the limbs which may be highly strained. These conditions are reversed in synclinal folds. In such cases, rocks of core regions are greatly strained.
11. Which of the following is not included under preliminary survey?
a) Knowing the general topography of the area
b) Knowing the lithology of the area
c) Knowing the structural condition of the rocks
d) Driving the pilot tunnels
Explanation: The preliminary surveys include: Knowing the general topography, the lithology, hydrological conditions in the area and structural condition of the rocks. Driving pilot tunnels, bore-hole drilling are considered under detailed surveys.
12. Folded rocks are often best storehouses of which of water?
a) Juvenile water
b) Magmatic water
c) Artesian water
d) Connate water
Explanation: Folded rocks are often best storehouses for artesian water and also ideal as aquifers. When encountered during tunnelling unexpectedly, these could create uncontrollable situations.
13. Which type of geological structure can be rectified by grouting?
d) Inclined strata
Explanation: In many cases problems created by jointing in rocks due to jointing can be grouting. In other cases, lining of the tunnel in the fractured zones might have to be applied.
14. The pressure of tunnel axis below the water table is preferable. State true or false.
Explanation: The tunnel axis might be located below the water table. Such a situation should be avoided as far as possible.
Sanfoundry Global Education & Learning Series – Engineering Geology.
To practice all areas of Engineering Geology, here is complete set of 1000+ Multiple Choice Questions and Answers.