This set of Engineering Geology Multiple Choice Questions & Answers (MCQs) focuses on “Origin of Joints and Engineering Considerations”.
1. The nature of sedimentary rock that can undergo some irregular jointing is
a) Plastic in nature
b) Non-plastic in nature
c) Rich in moisture
d) Plastic in nature and rich in moisture
Explanation: Sedimentary rocks especially those of plastic nature and rich in moisture in the initial stage (clays, shales, limestones, dolomites etc.) undergo some contraction on drying up which might have resulted into irregular jointing.
2. Contraction or shrinkage is the cause of which joints?
a) Radial joints
b) Vertical joints
c) Sheet joints
d) Mural joints
Explanation: During the formation of igneous rocks, tensile forces are developed in them due to cooling and the force is strong enough to cause joints. Such contraction or shrinkage is generally, accepted to be the cause of the vertical type of joints in granites and the so well -known columnar joints of basalts and other effusive rocks.
3. A single theory is enough to explain origin of all types of joints. State true or false.
Explanation: Joints are caused in different rocks due to different reasons. No single theory can explain origin of all types of joints.
4. The wide range of temperature which vary in arid climate is
a) -10° to 100° C
b) 10° to 80° C
c) -50° to 60°C
d) 50° to 60° C
Explanation: Repeated expansion and contraction is characteristic of regions with dry hot (arid) climates where day and night temperatures on the one hand and summer and winter temperatures on the other hand vary within a very wide range of -50° to 60° C.
5. Removal of overburden causes
Explanation: Removal of overburden due to weathering or other processes of rock wasting may also cause expansion of the underlying rocks due to unloading. The previously loaded rocks get relaxed with the release of the forces.
6. Sheet joints in sedimentary rocks are attributed to
a) Erosional loading
b) Erosional unloading
c) Weathering loading
d) Weathering unloading
Explanation: The sheet joints of sedimentary rocks and other rocks are attributed by many to the process of erosional unloading through geological ages.
7. What kind of impact do the joints have on activities of engineering?
c) No impact
d) Positive and negative
Explanation: Joints affect the properties of rocks both in a negative as well as positive manner with respect to the activities of a professional civil and mining engineer.
8. What is/are related to jointed rocks?
c) Slope failures
d) Landslides and slope failures
Explanation: Many landslides and slope failures are directly related to the jointed nature of the rocks. This is due to instability of rocks in hilly regions and the jointed rocks get easily lubricated in presence of moisture and start sliding or falling from their places.
9. First step of treatment of joints is
b) Filling with chemicals
c) Detailed investigation
d) Installing devices
Explanation: Treating the negative qualities of rocks due to joints will differ in different projects. The first requirement in all cases is, however, detailed investigations to establish full characteristics of the joints.
10. What has to be located during investigation with great care?
a) Macro joints
c) Micro joints
d) Macro joints and micro joints
Explanation: Great care has to be exercised in locating the presence, distribution patterns and magnitude of micro joints that are typical of many rocks. Such joints, if left unnoticed and untreated, may widen after the construction of the project and endanger its stability.
11. What is a positive effect of joints?
a) Instability in slopes
c) Oil reserves
d) Groundwater and oil reserves
Explanation: As regards the positive effects of joints in rocks, these are greatly sought after in the exploration for groundwater and oil reserves in a given area. Only a well-jointed and porous rock can form a good aquifer or a good oil and gas reservoir.
12. Mineralisation takes place in jointed rocks. State true or false.
Explanation: Mineralisation with economically valuable minerals from hydrothermal solutions takes place in jointed rocks and fissures, which are formed due to widening of joints.
Sanfoundry Global Education & Learning Series – Engineering Geology.
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