What is Bearing Capacity of Soil ? 14 Maximum Safe Bearing Capacity of Various Soils

Bearing Capacity of Soil

 

The load of the structure is ultimately coming on the soil and hence it is of utmost importance to know the strength and behavior of the soil. The term bearing power or Bearing Capacity of Soil is used to indicate the maximum load per unit area which the soil will resist safely without displacement. Dividing the ultimate Bearing Capacity of Soil of soil by a factor of safety, the safe bearing capacity of soil is obtained. 

 

Bearing Capacity of Soil
Bearing Capacity of Soil

 

Table 1.1 gives the maximum safe Various Bearing Capacity of Soil 

 

Table 1.1

 

MAXIMUM SAFE BEARING CAPACITY OF  SOILS

 

No.

Description Of Soil

Maximum Bearing Capacity of Soil

t/m2

kN/m2

1.

Very Soft, Wet, Pasty or muddy clay

5

50

2.

Black cotton soil in dry condition ( 50% saturation)

15

150

3.

Soft clay

10

100

4.

Moist clay and sand clay mixture

15

150

5.

Medium clay

25

250

6.

Compact clay, nearly dry

45

450

7.

Fine sand, loose and dry

10

100

8.

Medium sand, compact and dry

25

250

9.

Compact sand prevented from spreading

45

 450

10.

Loose gravel

25

250

11.

Compact gravel and moorum

45

450

12.

Soft rocks

45

450

13.

Laminated rocks such as sandstone and limestone

165

1650

14.

Hard rocks without defects and lamination such as granite , diorite and trap

330

3300

 

The topic of bearing capacity of soil is perhaps one of the most important of all the topics in the science of soil engineering. The soil have a tendency to behave in a complex manner when loaded and it gets deformed when stressed due to the loading. The resistance of soil to such deformation will depend on various factors like bulk density , angle of internal friction, water content, manner of application of load on soil, etc.

 

Following points should be noted in connection with the Bearing Capacity of Soil :-

 

Bearing Capacity of Soil
Bearing Capacity of Soil

 

(i). The difference between the two terms, namely, the maximum safe Bearing Capacity of Soil and the allowable bearing pressure on soil should be noted.

 

The term maximum safe Bearing Capacity of Soil is used to indicate the maximum pressure that a soil can bear without any risk of shear failure only, irrespective of any settlement that may occur.

 

The term allowable bearing pressure on soil is used to indicate the maximum pressure which can be exerted on a soil while taking into account shear failure, settlement and the ability of structure to resist settlement. Thus its value will depend on the nature of ground and the type of building.

 

Bearing Capacity of Soil
Bearing Capacity of Soil

 

(ii). The term “net pressure intensity” is used to indicate the excess pressure or the difference in the intensities of the gross pressure after the construction of the structure and the original overburden pressure. Let us consider one meter length of continuous footing of walls as shown in fig 1.2

 

Bearing Capacity of Soil
Bearing Capacity of Soil

 

Bearing Capacity of Soil
Bearing Capacity of Soil

 

Let        b = width of footing

             W 1 = Weight of soil that is removed

              W = Total load on the base transferred by the footing of wall

                       Including dead weight of footing and weight of back filling,

                       live load of floors, etc.

 

Then, Net Pressure intensity  =  Net load on base of foundation /Area of footing

                                                  

                                                      =        ( W – W 1 ) / b x 1                         

         

                                                      =         ( W – W 1 ) / b

                                                                 

(iii). For ordinary framed structure of concrete, the permissible angular distortion is 1/500 i.e. 1 horizontal  to 500 vertical and the desirable value is 1/1000 i.e. 1 horizontal to 1000 vertical. The maximum differential settlement should not exceed 25 mm in case of foundation of sandy soil and 40 mm in case of foundation on clayey soil. The total amount of settlement should generally be limited between 40 mm and 100 mm. The term angular distortion is used to indicate the deformation of the structure in a vertical plane and the term differential settlement indicates the relative settlement of the adjacent portions of the structure.

 

(iv). In case of non – cohesive soils such as sand and gravel, 50 per cent reduction in allowable Bearing Capacity of Soil should be applied, If water table is above or near the bearing surface of the soil. However, if water table is situated below the bearing surface of the soil at a depth equal to the width of the foundation trench, no such reduction should be applied. For intermediate depths of the water table, the proportionate percentage reduction should be applied.

 

(v). The bearing capacity of the reclaimed soil or ground, shrinkable soils, etc. is likely differ from site to site and it is therefore absolutely necessary to have detailed site exploration before deciding the safe bearing capacity for such soil. In the absence of such data, it will be reasonable to assume the safe bearing capacity of such soils as 50 k N/m 2.

 

This is the full explanation of Bearing Capacity of Soil

 

Also Check this video:-

 

 

 

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Happy Learning 😆

 

Also Read :-

 

EASY METHODS OF DAMPNESS TREATMENT BY DR. FIXIT SUPER LATEX

 

DAMPNESS IN BUILDING,REASONS/CAUSES AND PREVENTION METHODS OF DAMPNESS

 

10 IMPORTANT TIPS TO REDUCE CONSTRUCTION COST OF YOUR HOUSE

 

                                                      

 

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