Soil Mechanics - Exam 1 questions and answers with rated content

Soil Mechanics - Exam 1 questions and answers with rated content Soil Mechanics Application of static, mechanics of materials, and fluid mechanics to describe the behavior of soils Soil Weathering rocks and minerals What are the differences between sand and clay? (size, shape, strength comes from __?) Sand: larger/coarse grained, rounder, strength from frictional forces between particles Clay: small/fine grained, flat, strength from water interaction Effective stress stress felt by soil skeleton Consolidation water forced out of pore spaces settlement volume is changing differential settlement one side settles, not the other Geosynthetics man made plastic sheets (hydraulic barriers) Retaining Structures Hold soil at steeper slope than the soil can stand How old is the Earth? 4.6 billion years Lithosphere rocky upper mantle and crust, moves as solid plate Asthenosphere low mantle, hot, weak, ductile Rock naturally formed aggregate(collection) of minerals Igneous Rock solidified from molten rock Diff between magma and lava? magma is underground (intrusive), lava is above (extrusive) Mineral naturally formed, solid, forged inorganically, specified chemical composition Which are minerals? ice, water, coal ice=mineral water=not mineral coal=not mineral Regolith loose layer of debris from weathering What are the three main rock groups? igneous, sedimentary, metamorphic What rocks make up the crust, what rocks make up the surface? crust = 95% igneous and metamorphic surface = 75% sedimentary Cycle for rocks rocks formed -- uplift -- weathering Residual soil rate of soil formation is faster than transportation/erosion Eolian soil transported by wind saltation large sand picked up and moved a short distance loess wind blown salt (homogeneous size) Fluvial Soil deposited by streams and fresh water esker uniform What are the 4 phases of field investigation 1. collect info 2. familiarize with site 3. detailed site investigation 4. write report Boring and Drilling destructive method of sub surface exploration visual ID of soil type with sample collection Continuous flight boring destructive method of sub surface exploration -solid stem (have to keep removing it from hole, time consuming) -hollow stem (auger acts as casing to equalize pressure) -hand auger (cheap, limited depth) -water borings (pressurized water down drill shaft) What are three methods of retrieving a soil sample shelby tube split spoon block Sizes for coarse and fine grain? coarse .075mm fine .075mm size for coarse and fine gravel coarse = 19-75mm fine=4.75-19mm Non-clay physical characteristics particle size, particle distribution, particle shape, surface texture Is surface force more important for coarse grain or fine grain material? fine what is a typical specific gravity? 2.6-2.8 1m^3=?L 1000L Unit Weight= Unit Weight=W/V Dry Unit Weight= Dry Unit Weight=W(solids)/V(total) Water Unit Weight= Water Unit Weight=9.81=W(water)/V(water) Saturated Unit Weight= W(solids)+W(water)/V(total) where V(water)=V(voids) Gravemetric Water Content= Water Content=W(water)/W(solids) Volumetric Water Content= Volumetric Water Content=V(water)/V(total) Typical Gs 2.7 Void Ratio= Void Ratio=V(void)/V(solid) Porosity= Porosity=Vv/Vt=e/(1+e) Saturation= Saturation=Vw/Vv Stokes Law D=sqrt(18mz/(Gs-1)unitweightwatert)) D-particle size diameter Gs=specific gravity of soilds m=viscosity fluid z=depth from hydrometer ***stokes law doesn't apply to clay Plasticity Index PI=LL-PL liquid limit water content for liquid behavior plastic limit water content for plastic behavior liquidity index= LI(or IL)=(w-PL)/(LL-PL)