Cheat Sheet.docx - 1 Week 2 Soil Types Phase Relationships...

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1. Week 2: Soil Types & Phase Relationships 1. Soil: Soil is the accumulation of sediments and mineral particles, typically non-homogenous but not always, influenced by change in moisture content. Differentiated mainly by grain size. Shape/size increase hydraulic and mechanic soil parameters. 2. General Definitions: Residual Soil: weathered soil, remaining at original place Alluvial: transported by water Glacial: Transported by glaciers Loess: transported by wind … LOOSE! Marine: deposited in salt/brackish water Expansive: large volume changes with addition of moisture Dispersive: loss of cohesion in water Granular: No cohesion REV: Representative Elementary Volume. The sample size which has a size big enough to represent the sample accurately, can’t be too small, the bigger the sample size the better without getting ridiculous. 3.Fine Grained SoilsOccurs due to weathering of parent rock(mineral), resulting in formation of groups of crystalline particles at colloidal size(what does that even mean?) 4. Equations Void Ratio [-] Effective Unit Weight [kn/m^3] Porosity [-] Dry Unit Weight [kn/m^3] Moisture Content [%] Unit Weight of Solids [kn/m^3] Degree of Saturation [%] Specific Gravity [kn/m^3] Total Unit Weight [kn/m^3] = 9.81(10)kn/m^3 Saturated Unit Weight [kn/m^3] 2. Week 3: Soil Characterisation & Soil States 1. Soil Tests: Moisture Tests: Oven Drying: soil sample taken & measured, then oven dried, measure again. M D = M CDS – M C M w = M CMS – M CDS w = (M w /M D )x100% Sieving: chuck soil in sieves, shake for a while, measure each different sized soil, graph on a PSD Analysis→ Uniformity Coefficient: C u = D60/D10Curvature Coefficient: (D30) 2 /(D10 *D60) Hydrometer Method: wet dirt, put in tube of water, wait for it to settle, observe the layers of different soils, and take continual readings at different time intervals. 2. Atterberg Limits Liquid Limit: LL→ the minimum moisture content at which soil flows Plastic Limit: PL→ the minimum moisture content at which soil deforms plastically Shrinkage Limit: SL → the moisture content at which soil reduces volume Activity gives the reactiveness of soils to chemicals. 1. Limit Indices <1 = low activity 1-2 = intermediate activity >4 = high activity 2. Atterberg Limit Tests Determine LL Cone Penetration: drop a machine pin into sample, measure penetration, analyse on log log graph. LL at 20mm penetration Determine SL – Shrinkage: fill sample and measure, then dry sample and measure again Determine LL – Casagrande Method: mix soil & water in dish, use a U shaped knife and spread/split the soil. Measure gap and see if it reforms, count blows till reforms.

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