Bearing Capacity Soil bearing earth pressure theory assumes that upon exceeding a certain stress condition,rupture surfaces are formed in the soil mass.Thus,the stress causing the formation of these rupture surfaces may be considered as the Ultimate Bearing Capacity of the soil. Based on the above assumption,the bearing capacity can be determined from 1-The relationships of the principal stresses.The pertinent theories are those by Pauker,Rankine,Bell,Cassagrande and Fadum,Terzaghi and others (most common). 2-The shape of rupture surfaces,such as broken planes,circular,and logarithmic spiral 3-The mode of expulsion of the ruptured soil mass from underneath the base of the footing,i.e.one-side and two sides. Pauker's Bearing Capacity Equation(1850)(Cohesionless Soil) *One the oldest methods for determining bearing capacity of soil. *Developed based on Coulomb earth pressure theory (1776). *It is used for sandy soils only. Where s.=Ultimate Bearing Capacity *The bearing pac arly with the depth Z *This formula is valid only when Z Because the weight of the soil wedges below the footing are not included. **When f=0...... *No consideration for the cohesion of the soil (c). *This equation does consider the width of the footing 林The ne of internal friction at the vertical plane,A-Al,is not Notice: If the plastic deformation in soil was considered underneath thehoe width of the footi th the soil bearing capacity would directly be proportional to the width of the footing.Bearing Capacity Soil bearing earth pressure theory assumes that upon exceeding a certain stress condition, rupture surfaces are formed in the soil mass. Thus, the stress causing the formation of these rupture surfaces may be considered as the Ultimate Bearing Capacity of the soil. Based on the above assumption, the bearing capacity can be determined from: 1- The relationships of the principal stresses. The pertinent theories are those by Pauker, Rankine, Bell, Cassagrande and Fadum, Terzaghi and others (most common). 2- The shape of rupture surfaces, such as broken planes, circular, and logarithmic spiral. 3- The mode of expulsion of the ruptured soil mass from underneath the base of the footing, i.e. one-side and two sides. Pauker's Bearing Capacity Equation (1850) {Cohesionless Soil} ** One the oldest methods for determining bearing capacity of soil. ** Developed based on Coulomb earth pressure theory (1776). ** It is used for sandy soils only. Where su= Ultimate Bearing Capacity ** The bearing capacity increases linearly with the depth Z ** This formula is valid only when Z > 0 why ??????? Because the weight of the soil wedges below the footing are not included. ** When f = 0 ...... ** No consideration for the cohesion of the soil (c). ** This equation does not consider the width of the footing ** The angle of internal friction at the vertical plane, A-A1, is not included. Notice: If the plastic deformation in soil was considered underneath the whole width of the footing, then the soil bearing capacity would directly be proportional to the width of the footing