Presentation on theme: "Shallow Foundations Bearing Capacity The problems of soil mechanics can be divided into two principal groups - stability problems and elasticity problems."— Presentation transcript:
Shallow Foundations Bearing Capacity The problems of soil mechanics can be divided into two principal groups - stability problems and elasticity problems - Karl Terzaghi, 1943
Karl Terzaghi (1883-1963) Father of modern soil mechanics Born in Prague, Czechoslovakia Wrote Erdbaumechanick in 1925 Taught at MIT (1925-1929) Taught at Harvard (1938 and after)
General Guidelines Footings in clays - general shear Footings in Dense sands ( > 67%) -general shear Footings in Loose to Medium dense (30%< < 67%) - Local Shear Footings in Very Loose Sand ( < 30%)- punching shear
Selection of Soil Strength Parameters Use Saturated Strength Parameters Use Undrained Strength in clays ( S u ) Use Drained Strength in sands, Intermediate soils that where partially drained conditions exist, engineers have varying opinions; Undrained Strength can be used but it will be conservative!
Accuracy of Bearing Capacity Analysis In Clays …..Within 10% of true value (Bishop and Bjerrum, 1960) Smaller footings in Sands…. Bearing capacity calculated were too conservative – but conservatism did not affect construction cost much Large footings in Sands … Bearing capacity estimates were reasonable but design was controlled by settlement