Leads Institute of Technology & Engineering Subject Code : Name Of Subject :Building Construction Name of Unit : Soil Foundation Topic : Bearing Capacity of Soil

TOPIC :- B EARING CAPACITY OF SOIL

W HAT IS B EARING CAPACITY OF SOIL ? The maximum load per unit area which the soil or rock can carry without yielding or displacement is termed as bearing capacity of soil. There are four types of bearing capacity. They are as follows;- 1. Ultimate bearing capacity of soil. 2. Safe bearing capacity. 3. Net pressure intensity. 4. Allowable bearing pressure.

 U LTIMATE BEARING CAPACITY OF SOIL :-  It is defined as intensity of loading, at the base of foundation, at which soil supports fails in shear.

 S AFE BEARING CAPACITY :-  It is defined as maximum intensity of loading that the soil will safely carry without risk of shear failure.  It can be obtained by dividing the ultimate bearing capacity by a certain factor of safety.

 N ET PRESSURE INTENSITY :-  It is defined as loading acting on bottom of foundation trench in excess of weight of soil removed from the trench.

 A LLOWABLE BEARING PRESSURE :-  It is defined as maximum allowable net loading intensity which can be applied to soil taking into account the ultimate bearing capacity, the amount and kind of settlement expected and the ability of given structure to withdraw the settlement.

TOPIC :- M ETHODS OF DETERMINING BEARING CAPACITY OF SOILS

 T HE BEARING CAPACITY OF SOIL CAN BE DETERMINED BY THE FOLLOWING METHODS :- i. Plate load test ii. Penetration test iii. Safe bearing capacity values given in codes

P LATE LOAD TEST This is a field test for determining the ultimate bearing capacity soil and the likely settlement due to given loading. The test consist of loading a steel plate at foundation level and the settlement due to each load increment are recorded. Thus the ultimate bearing capacity of soil is obtained by dividing the total load on the plate.

P ENETRATION TEST The test consists of the measurement of resistance offered by the soil to the penetration. Thus, based on the values of resistance the bearing capacity of soil can be determined by using standard graphs. In this method, a hole of 55 to 150 mm in diameter is made in the ground with the help of suitable equipment for conducting the test.

The test are made and the sample are taken out at every change in stratum. In case of very fine or silty saturated sand, due to apparent in resistance, the N-values obtained by this test are more.

S AFE BEARING CAPACITY VALUES BASED ON I.S. CODES The safe bearing capacity of soil should be determined on the basis of soil tests data. Peat may occur in a very soft spongy condition.

I.S. C ODES Some I.S. codes are listed below. IS: 456 – code of practice for plain and reinforced concrete. IS: 383 – specifications for fine & coarse aggregate from natural sources for concrete. IS: 2386 – methods of tests for aggregate for concrete. IS: 2430 – methods of sampling. IS: 4082 – specifications for storage of materials. IS: 2116 – permissible clay, silt & fine dust contents in sand. IS: 3495 – methods of testing of bricks. IS: 3025 – tests on water samples.