1 2 1 4 Grain Size mm Silt
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1. 4 흙 입자의 크기와 입도분석 Grain Size (mm) Silt and Clay F M Gravel C Size (mm) 0. 075 4. 75 Sieve No. 200 4 Fine-grained soils 세립질 비중병 시험 광물종류 수분(연경도) 0. 075 mm 75 m 1000 75 uld e Sand 100 rs 10 Bo 1 s 0. 1 bb le 0. 01 Co 0. 001 300 Coarse-grained soils 조립질 체분석 시험 입자모양, 크기(분포)정도 Packing 14
Sieve Analysis (Mechanical) Coarse. Grained Sieves d > 75 m Sieve Number Sieve # = # openings per inch 16
Sieve Analysis (Mechanical) PROCEDURE Largest Openings Sieve Stack • Place known mass of soil in top sieve • Shake sieve stack • Weigh soil retained on each sieve Smallest Openings 17
Sieve Analysis (Mechanical) PROCEDURE Largest Openings Shaking table • Place known mass of soil in top sieve • Shake sieve stack • Weigh soil retained on each sieve Smallest Openings 18
Sieve Analysis (Mechanical) Potential Problems: Square openings measure only one characteristic length Applied mechanical forces may break particles 19
Sieve Analysis (Mechanical) We compute: % retained on n-th sieve = wn wtotal X 100% % finer than nth sieve = To plot: Grain Size Distribution Curve 21
Sieve Analysis (Mechanical) ACEE 212 – 토질역학의 기본 22
Index Properties of Coarse-Grained Soils Factors affecting engineering behavior Index properties • Grain size distribution • D 50, D 10, Cu, Cc, etc. • Grain shape • Relative Density (2장) • Grain packing 23
Hydrometer Analysis Silts & clays too small for sieve analysis Hydrometer measures Gs of a suspension • • Mix small mass of soil into a suspension with dispersant (Na. PO 3)6 Lower hydrometer into suspension Hydrometer sinks until buoyancy force = hydrometer weight L = f( suspension, temp) 25
Hydrometer Analysis • • Particles settle according to size Density changes with time, so hydrometer sinks Hydrometer readings taken with time Readings corrected for temp 26
Hydrometer Analysis 27
Hydrometer Analysis 28
1. 4 흙 입자의 크기와 입도분석 • Qualitative descriptors: • Well graded • Poorly graded (uniform or gap graded) 31
1. 5 점토광물 세립질 – 입자크기 < 0. 075 mm (#200) – 광물특성, 수분(연경도) 기호 : 산소 Silica tetrahedron Silica (tetrahedral) sheet 기호 Alumina octahedron Alumina (octahedral) sheet gibbsite sheet (after Budhu, 2000) 32
1. 5 점토광물 Index Properties of Fine-Grained Soils Factors affecting engineering behavior • Clay mineralogy • Chemical and electrical bonds between clay particles Index properties • Atterberg limits (2장) • Interaction between clay particles and water 33
1. 5 점토광물 1. 5. 1 점토광물 1) 점토광물의 기본단위 (1) silica tetrahedron ⇒ silica (tetrahedral) sheet (2) alumina octahedron ⇒ alumina (octahedral) sheet (또는 gibbsite sheet) 34
1. 5 점토광물 Kaolinite (1: 1) “Strong” bonds “Large” particles 0. 72 x 10 -9 m (after Budhu, 2000) 36
1. 5 점토광물 Illite (2: 1) “Medium” bonds “Medium” particles 0. 96 x 10 -9 m (after Budhu, 2000) 37
1. 5 점토광물 Montmorillonte (2: 1) “Weak” bonds “Small” particles 0. 96 x 10 -9 m (after Budhu, 2000) 38
1. 5 점토광물 1 cm Volume Surface Area 1 cm 3 6 cm 2 1 cm 3 12 cm 2 1 cm 3 24 cm 2 1 cm 39
1. 5 점토광물 Clay Mineral Typical Thickness (mm) Typical Diameter (mm) Specific Surface (m 2/g) Sand 1 1 0. 01 Kaolinite 5 x 10 -5 to 2 x 10 -3 3 x 10 -4 to 4 x 10 -3 10 to 20, ~15 Illite 3 x 10 -5 1 x 10 -2 65 to 100, ~80 Montmorillonite 3 x 10 -6 1 x 10 -4 to 1 x 10 -3 Up to 1000, ~800 40
1. 5 점토광물 Montmorrilonite particle Kaolinite particle Adsorbed water (after Lambe, 1958) 45
Clay Image Kaolinite illite Montmorillonite http: //blass. com. au/ 46
Homework Assignment – Chapter 1 Assignment # 1 Due: Next week 연습문제 1 (모눈종이) 47
Hydrometer Analysis **Based on Stoke’s Law** At terminal velocity (zero acceleration): W – B – F = 0 Where weight W= s. V V=1/6 d 3 B = w. V F = 6 v (d/2) buoyancy drag v=velocity of sedimentation = viscosity 48
Hydrometer Analysis Particle diameter d at time t based on Stoke’s Law Where: = viscosity of water (1 c. P at 20°C) L = hydrometer reading Gs = specific gravity of solids w = unit weight of water 49
Hydrometer Analysis Assumptions of Stoke’s Law d • • Spherical particles Free-falling particles Particles all have similar Gs Particles are dispersed Effective size range: 200 m → laminar flow conditions 0. 2 m → Brownian motion 50
Grain-Size Distribution • • Soil classification Selection of fill materials Selection of aggregates Selection of road base materials Drainage filters Permeability estimates Viability of grouting and chemical injection 51
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