Ass. 1 Solutions - Engr 3150 — Principles of Soil...

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Unformatted text preview: Engr 3150 — Principles of Soil Mechanics Assignment #1 - Solutions 1) a) List processes of mechanical weathering. Thermal expansion and contraction of rocks, freeze/thaw cycles, particularly water freezing in cracks in rock, movement of glacier ice, wind action, running water including wave action. b) Briefly describe how Clay minerals are formed. Clay minerals are formed by chemical weathering of rock minerals. Water and carbon dioxide form carbonic acid which reacts with the rock minerals, resulting in the formation of clay minerals. 0) Briefly describe the modes of formation of residual, alluvial, lacustrine, aeolian and colluvial soils. > Residual soils — weathering products are not transported but remain in their place of origin )e Alluvial soils — soil particles transported by running water and deposited along streams and rivers ‘i Lacustrine soils - formed by deposition of soil particles in a lake environment in which water velocities are typically quite low > Aeolian soils — soil particles transported and deposited by wind > Colluvial soils — soil particles are transported by gravity, such as down a slope to the base of the slope d) What are the processes that attract water molecules to a clay mineral particle surface? The negative charge of the clay mineral particle surface attracts dipolar water molecules, cations that are hydrated are attracted to the negatively charged clay mineral particle surface and bring the water molecules with them and hydrogen bonding between the water molecule and oxygen atoms on the clay mineral particle surface. e) What gives clay soils their plastic properties? Double layer water within the diffuse double layer surrounding the clay mineral particles gives clay soils their plastic properties f) Describe a dispersed and a flocculated clay structure. What interactions between the clay mineral particles lead to each structure? Dispersed structure - clay mineral particles form a parallel, face—to—face orientation — this structure is formed when there is net repulsion between the particles. Fiocculated structure — clay mineral particles form an edge-to-face "cardhouse type” orientation - this structure is fanned when there is net attraction between the particles. The presence of cations from salts (such as Ca+2) in the solution tends to depress the thickness of the diffuse double layers and reduce the interparticie repulsion forces. . I...+ ..... . I . I . I . I . l I I I .. ILII w 755. ‘m I . II .' r ’3 O 2i «- .— . I l <_ ; . I I , i . h - I ': V ' I - m j W— ' ..: - ud— ! I' ; I I - I I _. _ ._1._.__ .l . I I I _ . I Ir - a . J 'l I I a I I l i I 1 I I E __ _ I -. = .E I I I I r a I '- r | - E I | 1 . I 1 _ I I l I . I , I I _ . t I -..._+...._....I,......._........ .- .._:... .. _.n... _ _. .. rd..- t , I I I 1. l I A) I ‘ 1. I 1 I I L I I I l ibfl M I 5 I _ --— -—.~- -----—- r— _ I ‘ . m _ E I . I I ' | | ‘ I I i | I _f T; I.__I_._H m... 5 . . = I I I. I I. ‘ ‘ . I I . I _ ‘— ' | -. =; l : . "" - i . ' a ‘- E i '. "- L— “!_.__ .-_..,.H.HEI... m I | . | l | . —n | .n ‘é‘M i IOLflEQIW‘W .l E 0:332? \ 50 - E: 1* .I. m 5; $9 0.:— mf (8?; 0.20 if“; _________ ,4" WWqu H, wq%m9_§4li,®€wW _ .l \o. 9 Egan}, L. 9 .3 _ :22 abeqé 5. W013 EMQPALW _.._...._._H##_“a...”wwwww...-_n..wC._..._.;_.--....Dga%mi_.©:qqu _.--.-.*_ ._-_:,_-__n_g _._._-w-..__.--._.I..._Mf-a.__.mum.-.”.__ " " DESK:‘§?3”951§Tf""2:1:§;Qijiiifimif: _ ' wL: _ __ ~ y {a $1 | j E we, —« £1!as.im\.._3g9.§\._--__.W_m_ 0.1a ._ .19 :— fiE; 31.0 . _ ‘ _, L 5 w b miiflghfii17:31::"7:: I“ li-“Q' 73“; ** afiéfl) = 2630 § 1‘26. > 25.19-.. 9.5% mm. 0.05 Grain diameter {mm} Grain-size distribution curve Sampie No. Q N t c .W D r D. Date Plotted by ...
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Ass. 1 Solutions - Engr 3150 — Principles of Soil...

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