Important Question And Answer: Civil - Shallow Foundation

Shallow Foundation

1. What are components of total foundation settlement?

Elastic settlement, consolidation settlement, secondary consolidation settlement

2. What are the types of shear failure?

General shear failure, local shear failure, punching shear failure

3. What are assumptions in Terzaghi's bearing capacity theory?

- the base of the footing is rough

- the load on footing is vertical and uniformly distributed

- the load on footing is vertical and uniformly distributed

4. List out the methods of computing elastic settlements?

based on the theory of elasticity, Pressure meter method, Janhu -Bjerram method,

Schmentmann's method

5. What are the limitation of Terzaghi's analysis?

- As the soil compresses, pi changes slight down ward movement of footing may

not develop fully the plastic zones

- Error due to assumption that the resultant passive pressure consists of three

components is small

6. Define ultimate bearing capacity?

Gross pressure at the base of the foundation at which the soil fails in shear is called ultimate bearing capacity.

7. Define net ultimate bearing capacity ?

Net pressure increase in pressure at the base of the foundation that causes failure in shear, is called as net ultimate bearing capacity

8. Define allowable bearing capacity?

It is the net loading intensity at which neither the soil fails in shear nor there is excessive settlement detrimental to the structure

9. Write the expression for correction due to dilatancy submergence?

Ne = 15 + ( No-15 )

10.What are the requirements for a stable foundation?

-must be safe from failure

-must be properly located

-must not settle or deflect sufficiently to damage the structure or impair its usefulness.

11. What are the factors which depends depth?

Type of soil, size of structure, magnitude of loads, environmental conditions, etc

12 .Define net pressure intensity ?

It is the excess pressure, of the gross pressure after the construction of the structure  and the original overburden pressure.

13. What are the zones used in the Terzaghi's bearing capacity analysis for dividing the failure envelope of the soil.?

Elastic equilibrium zone, Radial Stress zone, plastic zone

14. Write the ultimate bearing capacity equation for the general shear failure of soil in

Terzaghi's analysis for a strip footing.

qu = c Nc + ?DNq + 0.5 ?B N?

15. Define Shallow foundation.

If the depth of the foundation is less than its breadth, such foundation is known as shallow foundation.

17. Write down the equation for estimating the elastic settlement based on the theory of elasticity.?

18. When will the total settlement be completed in the case of cohesion-less soil?

Once the construction is over, the total settlement is assumed to be completed.

19. Define differential settlement

If any two points of the foundation base experiences different settlements then

such settlement is known as differential settlement.

20. What type of shear failure of soil is more likely to happen in the case of very dense soil?

usually punching shear failure and local shear failure may also be possible.

21. Write the ultimate bearing capacity equation for the general shear failure of soil in

Terzaghi's analysis for a square footing.

qu = 1.3 cNc + ?D Nq + 0.4 ?B N?

22. When will the Consolidation settlement get completed?

In the case of cohesion-less soil, the consolidation settlement gets completed once   the construction is over. But In the case of cohesive soil, the consolidationsettlement takes place for several years.

24. Define Deep foundation

If the depth of the foundation is equal to or greater than the breadth of the foundation such foundation is called as deep foundation.

25. For which type of foundation, Terzaghi's bearing capacity equation is applicable. Why?

Shallow foundation only. Because the effect of the depth is not considered.