Differential Settlement. - Its Causes and How to Prevent it

Total settlement of a foundation consists of: 1. Immediate settlement 2. Consolidation settlement 3. Secondary consolidation settlement The immediate settlement is also known as elastic settlement. It can be found by elastic theory as, Se = qn B where qn = Net foundation pressure B = Width of foundation m = Poisson’s ratio Es = Modulus of elasticity qn = Influence factor which depends upon ratio of the foundation and the thickness of compressible layer Consolidation settlement may be found by Sc = where H = Thickness of compressible layer Cc = Compression index eo = Initial void ratio Po = Initial overburden pressure Dp = Increase in the pressure due to load Secondary consolidation settlement is small and takes place over a long period. Plate Load Test By loading a rigid square plate in a pit with reaction frame this test is conducted to measure the settlement. The following points may be noted: 1. The minimum size of plate 300 mm. Commonly used plate sizes are 300 mm, 450 mm and 600 m...