civil engineering department soil mechanics 803440-3 introduction lecture 2 week 2 2014/2015 umm...
TRANSCRIPT
Civil Engineering Department
Soil Mechanics803440-3
Introduction
Lecture 2Week 2
2014/2015
UMM AL-QURA UNIVERSITY
Content
• Purposes of Grain Size Analysis• Purposes of Grain Size Analysis
• Sieve Analysis
• Hydrometer Analysis
• Particle Distribution
• Shape of Soil Particles
Purposes of Grain Size Analysis
The size distribution is often of critical importance to the way the material performs in use.
• Concrete Structures Economical Filler
Examples
• Roads Construction Bearing Base
• Agriculture Infiltration Rate
• Environment Filters
Grain Size Analysis
S1 < d
M1%
S3 < d < S2
M3%
S2 < d < S1
M2%
d < S3
M4%
Sieve Analysis
Sieve Analysis
Standard Sieves
Sieve No.Sieve Opening
(mm)
4 4.75010 2.00020 0.85040 0.42560 0.250
100 0.150200 0.075
See text book (table 2.5)
Cohesiveness
• Soils can also be divided into:cohesive and non-cohesive
• Non-cohesive means the soil has no shear strength if no confinement.
• Cohesive soil contains clay minerals and posses plasticity
• Clay is cohesive and plastic.
• Sand is non-cohesive and non-plastic.
Hydrometer Analysis
Based on the principle of sedimentation of soil grains in water and bouncy principle.
Stock’s Law
V1 V2<
Bouncy Force
F = V ρ g
Hydrometer Analysis
Questions?!
30:00 min
Percent Finer
76.2 mm
4.75 mm
0.075 mm
Pan
100 %
Finer (Passing)
93 %
62 %
0 %
Gravel
Sand
Silt and Clay
100 – 93 = 7%
93 – 62 = 31%
62 – 0 = 62%
Gravel
Sand
Silt and Clay
Example: Sieve Analysis
Example: Sieve Analysis
Example: Sieve Analysis
0
10
20
30
40
50
60
70
80
90
100
012345Particle Size (mm)
Per
cent
Fin
er %
Example: Sieve Analysis
Log-Scale
Group Work
Particle-Size Distribution Curve
Particle-Size Distribution Curve
1. Effective Size (D10)
2. Uniformity Coefficient (Cu)
3. Coefficient of Gradation (Cz)
10
60u D
DC
1060
230
z DD
DC
10% Finer Hydraulic Conductivity
Particle-Size Distribution Curve
1. Effective Size (D10)
2. Uniformity Coefficient (Cu)
3. Coefficient of Gradation (Cz)
10
60u D
DC
1060
230
z DD
DC
10% Finer Hydraulic Conductivity
Particle-Size Distribution Curve
QuestionWhat is the Cu for a soil with only one grain size?
Particle-Size Distribution Curve
Uniformity Coefficient (Cu)
D
Fin
er
1D
DC
uniformityoftCoefficien
10
60u
Grain size distribution
Particle-Size Distribution Curve
Criteria for Well-Graded Soil
sands)(for
6Cand3C1
gravels)(for
4Cand3C1
uz
uz
Particle-Size Distribution Curve
Questions?!
90:00 min
Hydrometer Analysis
Stokes’ Law
2ws D η18
ρρv
ws ρρ
η18
t
LD
t
LKD
Hydrometer Analysis
Hydrometer Analysis
R
L
L = 16.29 – 0.164 R
1. Temperature (FT)
2. Meniscus Correction (Fm)
3. Zero Correction (Fz)
FT = - 4.85 + 0.25 T
Corrections: Hydrometer Analysis
Questions?!
105:00 min
Example: Sieve Analysis
Example: Sieve Analysis
Rounded
Angular
Questions?!
120:00 min