METHODS TO IMPROVE BEARING CAPACITY OF SOIL

USEFUL METHODS TO IMPROVE THE BEARING CAPACITY OF SOIL

 

BEARING CAPACITY OF SOIL:

The load of any structure is finally transmitted to the soil lying below the foundation of the structure. Hence it is essential to know the strength and behaviour of the underlying soil.

The maximum load per unit area which the soil can carry without any settlement or displacement is termed as bearing capacity of the soil.

ULTIMATE BEARING CAPACITY OF SOIL:

The minimum load on unit area causing failure is called the ultimate bearing capacity of the soil.

SAFE BEARING CAPACITY OF SOIL:

The maximum intensity of loading that the soil will safely carry without the risk of shear failure is called safe bearing capacity of the soil. It is obtained by dividing the ultimate bearing capacity by a certain factor of safety which is used in the design of foundation. The value of factor of safety varies from 2 to 3 depending upon the nature of the soil.

5 METHODS TO IMPROVE THE BEARING CAPACITY OF SOIL:

These are the following methods which can be used to improve the bearing capacity of soil.

1.  INCREASING THE FOUNDATION DEPTH:

Increasing the depth of the foundation is the simplest method for improving the bearing capacity of soil. Because soil has a high pressure at the deeper depth. Hence it will be more compacted.

2. DRAINING THE SUBSOIL:

Drainage is another well-known method which improves the bearing capacity of soil. In this process drains are placed near the footing base, then the subsoil water is collected and drained out by a pipe.

3.  BLENDING GRANULAR MATERIALS:

In this method certain amount of granular materials such as sand, gravel, crushed stone etc. is blended into the weak soil by ramming. Hence the poor soil becomes much stronger and bearing capacity is improved.

4.  CONFINING THE SOIL:

The soil is confined in a bounded area with the help of sheet piles. This method is suitable for sandy soils.

5. DRIVING SAND PILES:

This method is also helpful to improve the bearing capacity of soft soil by reducing the void volume. Here wooden piles are used to make holes in the weak soils and then sand is filled into the holes by ramming.

MAXIMUM SAFE BEARING CAPACITY OF DIFFERENT TYPES OF SOIL:

1. Soft, wet clay or muddy clay — 5,000 kg/m2

2. Soft clay — 10,000 kg/m2

3. Fine, loose and dry sand — 10,000 kg/m2

4. Black cotton soil — 15,000 kg/m2

5. Moist clay and sand clay Mixture — 15,000 kg/m2

6. Loose gravel — 25,000 kg/m2

7. Medium clay — 25,000 kg/m2

8. Medium, compact and dry sand — 25,000 kg/m2

9. Compact clay — 45,000 kg/m2

10. Compact sand — 45,000 kg/m2

11. Compact gravel — 45,000 kg/m2

12. Soft rocks — 45,000 kg/m2

13. Laminated rock such as sand stone & Lime stone — 165,000 kg/m2

14. Hard rocks such as granite, diorite, trap–  330,000 kg/m2