Here are the top 50 commonly asked questions in Geotechnical Engineering interviews. Whether you’re just starting your preparation or need a quick refresher, these questions and answers will help you tackle your interview with confidence.
Basic Geotechnical Engineering Interview Questions with Answers
1. What is Geotechnical Engineering?
Geotechnical Engineering is a branch of engineering which is mainly studied to analyze the stability of a structure over the soil mass.
2. What is the difference between Geotechnical Engineering and Soil Mechanics?
Soil Mechanics is studied to understand the behavior of soil whereas Geotechnical Engineering is studied to understand the stability of structures over the soil e.g., stability of slopes, footings stability etc.
3. What is foundation in Geotechnical Engineering?
Foundation is a part of the structure that transfers the load of the superstructure to the soil.
4. What are the applications of Geotechnical Engineering?
Applications of Geotechnical Engineering are: i) Determines bearing capacity of soil; ii) Determines ultimate load carrying capacity of the pile; iii) Calculates earth pressure on the retaining structures; iv) Settlement of soil mass etc.
5. When deep foundations are needed in Geotechnical Engineering?
Deep foundations are needed: a) When lateral forces are relatively prominent; b) In presence of expansive and collapsible soils at the site; c) For offshore structures; d) For structures near flowing water to avoid the problems due to erosion.
6. What are the types of foundations in Geotechnical Engineering?
There are two types of foundations: i) Shallow foundation: Depth of the foundation is less than or equal to width of the foundation; ii) Deep foundation: Depth of the foundation is greater than width of the foundation.
7. What is punching shear failure in Geotechnical Engineering?
Punching shear failure occurs in deep foundation surrounded by loose soil or soft clay. In this failure, soil mass below the footing gets cut off from the adjacent soil due to which very large settlement of footing occurs.
8. What is the application of Terzaghi’s Theory in Geotechnical Engineering?
In Geotechnical Engineering, Terzaghi’s theory is used to determine ultimate bearing capacity of soil by considering general shear failure.
9. What are under-reamed piles in Geotechnical Engineering?
Under-reamed piles are essentially cast in-situ piles which are generally used in those soils which shows high expansive nature e.g., black cotton soil.
10. What are sheet pile walls in Geotechnical Engineering?
Sheet pile walls are earth retaining structures. Sheet piles are generally made of steel or timber. The use of timber piles is generally limited to temporary structures, for permanent structures and for depth of driving greater than 3.0 m steel piles are most suitable.
11. What is negative skin friction in Geotechnical Engineering?
When the soil mass in contact with the pile settles more than the pile due to application of external load on the pile, then friction force develops in the direction of external load. This developed friction force is known as negative skin friction.
12. What is gross pressure in Geotechnical Engineering?
Gross pressure is summation of external load on footing, self-weight of the footing, and overburden pressure due to soil mass.
13. What is the term “liquefaction” in Geotechnical Engineering?
When pore water pressure in a soil mass increases and become equal to effective vertical stress, then soil loses its strength and behaves like thick liquid. This phenomenon is called liquefaction.
14. Who is the father of Geotechnical Engineering?
Karl Von Terzaghi is considered as father of Soil Mechanics as well as Geotechnical engineering.
15. What are the advantages of rock fill dam in Geotechnical Engineering?
Advantages of rock fill dam are: i) Easy construction; ii) No skilled labor needed; iii) Cheaper than other types of dams; iv) Height can be raised without difficulty.
16. What is ultimate bearing capacity of soil in Geotechnical Engineering?
The maximum gross pressure which can be subjected to the soil so that the soil mass doesn’t fail in shear is called as ultimate bearing capacity of soil.
17. What is the effect of ground water table (GWT) on bearing capacity in Geotechnical engineering?
Effect of ground water table are: i) Due to changes GWT, the unit weight of soil changes; however, coefficient of cohesion and frictional resistance do not change; ii) GWT has no effect if the GWT is present below the depth B beneath the footing.
18. Which field tests are used for determination of bearing capacity of soil in Geotechnical Engineering?
Field tests used for determination of bearing capacity are: i) Plate load test; ii) Standard penetration test; iii) Cone penetration test.
19. What are the applications of standard penetration test in Geotechnical Engineering?
Standard penetration test is used to determine: i) Angle of internal friction; ii) Density index; iii) Bearing capacity based on shear and settlement criteria; iv) Ultimate load bearing capacity for driven and bored piles.
20. Which parameters effect the bearing capacity of soil in Geotechnical Engineering?
Parameters that effects the bearing capacity of soil: a) Shape of footing; b) Depth of footing; c) Inclination of load; d) Ground slope; e) Tilted base; f) Eccentric load or moment.
Intermediate Geotechnical Engineering Interview Questions with Answers
21. What is earth pressure and its types?
The pressure applied by the soil or backfill on the retaining wall is known as earth pressure. Depending upon the movement of retaining wall, earth pressure is classified into 3 types: i) Earth pressure at rest; ii) Active earth pressure; iii) Passive earth pressure.
22. What is active earth pressure?
The earth pressure on the retaining wall is decreased up to an extent when shear resistance offered reaches its maximum value and at that stage earth pressure on the retaining wall is referred as active earth pressure.
23. What is passive earth pressure?
The pressure on the retaining wall is increased up to an extent when entire resistance offered reaches its maximum value and at that stage earth pressure acting on the retaining wall is referred as passive earth pressure.
24. What are the assumptions of Rankine’s earth pressure theory?
Assumptions of Rankine’s earth pressure theory are: i) Soil is homogenous, isotropic, semi-infinite, dry and cohesionless; ii) Backfill surface is planar which may be horizontal or inclined; iii) The retaining wall is vertical and smooth.
25. What is spread footing?
Spread footing is circular, square or rectangular slab of uniform thickness. Sometimes, it is stepped to spread the load over a larger area. When spread footing is provided to support an individual column, it is called “Isolated footing”.
26. When combined footing is used?
Combined footing is used when the two columns are so close that their individual footings overlap. It is also provided when the property line is so close to one column that a spread footing would be eccentrically loaded.
27. What is earth retaining structure?
The retaining structures are designed to withstand the forces exerted by the retained ground or ‘backfill’ and other externally applied loads, and to transmit these forces safely to a foundation.
28. What are the causes of foundation failure?
There are two causes of foundation failure: i) Due to excessive settlement, settlement failure occurs; ii) Due to slipping or sliding of foundation.
29. What are the guidelines for minimum depth of foundation?
Guidelines for minimum depth of foundation: i) The depth of foundation should be more than depth of organic fill; ii) The depth of foundation should be more than depth of frost action; iii) Depth of foundation must be greater than 30cm for single storey.
30. What are the guidelines for selection of foundation?
Guidelines: i) If loading is not heavy and soil is medium to dense, then choose shallow foundation; ii) If loading not heavy and soil Is loose, then choose deep foundation or mat/raft; iii) If soil is very expansive, then choose floating/balanced foundation.
31. What is ultimate bearing capacity of soil?
The maximum gross pressure which can be subjected to the soil so that it does not fail in shear is called as ultimate bearing capacity of soil.
32. What is net safe bearing capacity of soil?
The maximum net pressure which can be applied safely to the soil so that it does not fail in shear is known as net safe bearing capacity. It is calculated by the formula, qns = qnu/FOS where FOS is factor of safety and qnu is net ultimate bearing capacity.
33. Which factors affect the bearing capacity of soil?
Factors affecting the bearing capacity are: i) Presence of water table; ii) Type of foundation; iii) Dimensions of footing; iv) Nature of ground surface i.e., horizontal or inclined; v) Nature of load.
34. What is general shear failure?
General shear failure occurs in shallow foundation, in medium to dense soil. In this failure, stress zone is extended up to the ground surface. At the time of general failure, tilting of the foundation and heaving occurs at the site.
35. Where does local shear failure occur?
Local shear failure occurs in shallow foundation, in loose soil and soft clay. In local failure, stress zone is not extended to the ground level. At the time of local failure, slight tilting can be observed but there is no heaving.
36. What are the analytical methods to determine bearing capacity?
Methods to determine bearing capacity: i) Terzaghi method: Strip footing; ii) Rankine’s method: Only for strip footing and cohesionless soil; iii) Skempton’s method: Only for purely cohesive soil; iv) Meyerhof’s method: Both for cohesionless and cohesive soil.
37. What are the assumptions of Terzaghi’s theory for determination of bearing capacity?
Assumptions of Terzaghi’s theory are: i) Foundation is shallow; ii) The base of the footing is rough; iii) The failure is general shear failure; iv) The footing is continuous; v) At the time of failure, soil reaches plastic equilibrium.
38. What is Skempton’s method?
Skempton’s method is used to determine net ultimate bearing capacity for purely cohesive soil. In this method, both side and base resistance are considered, so it can be used for any type of foundation.
39. What is Meyerhof’s theory?
Meyerhof’s theory is most generalized theory and it is used both for cohesionless and cohesive soil to determine bearing capacity. It considers both base and side resistance offered by the soil.
40. What is ultimate load carrying capacity of pile?
The maximum load which can be applied on the pile, so that it doesn’t fail in shear is known as load carrying capacity of pile.
41. What is end bearing pile?
In end bearing pile, resistance is offered only from bottom because the pile rests upon hard strata. The length of the end bearing pile depends on the depth at which hard strata is found.
42. What is friction file?
Friction pile is a pile that is used for construction of deep foundation. It is generally used in case of loose soil and resistance is offered only from the sides.
43. What are the types of pile on the basis of installation?
Classification on the basis of installation: i) Driven/Displacement pile: It is a precast pile with high load carrying capacity; ii) Bored/Non-displacement pile: It is a cast in-situ pie with low load carrying capacity.
44. What is safe load carrying capacity?
The maximum load which can be applied on the pile safely so that pile doesn’t fail in shear. It is calculated by formula, Qs = Qu/FOS where Qu is ultimate load carrying capacity and FOS is factor of safety.
45. How to determine ultimate load carrying capacity from Engineer’s New Record (ENR) method?
Engineer New Record formula, Qu = W*H/ (S + C) where Qu is ultimate load carrying capacity, W is weight of hammer in KN, H is height of fall in cm, S is penetration of pile per blow of the hammer in cm, and C is elastic constant in cm.
46. What are the assumptions made in dynamic method to determine load carrying capacity?
Assumptions: i) Load carrying capacity dynamic loading should be equal to load carrying calculated from static/analytical method; ii) Kinetic potential energy of the hammer will be equal to sum of losses and work done by the pile.
47. How to determine allowable load on pile using static pile load method?
Static pile load method is a field method. It calculates permissible load on the basis of settlement of pile. If the pile settlement is 12mm and Qu is load corresponding to 12mm, then the allowable load on the pile become 2/3rd of
u.
48. What is group action of pile?
If number of piles are used and the piles are close enough, then the stress field of each pile overlap due to which soil between the piles get compacted and entire wedge consisting of soil and pile resists the external load. This action is known as group action of piles.
49. What are the methods to determine load carrying capacity?
Methods to determine load carrying capacity are: i) Static/Analytic method; ii) Dynamic method: Engineer’s formula and Hiley’s formula; iii) Field method: a) Pile load test; b) Standard penetration test; c) Cone penetration test; d) Cyclic pile load test.
50. What are the types of slopes?
Slopes of earth are of two types: i) Natural slopes: Those exists in nature and are formed by natural causes; ii) Man made slopes: The slopes of embankments constructed for roads, railway lines, canals etc. are examples of man made slopes.
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