Page 7 - Handbook GEOTEKNIK_Final_Neat

Common Parameter used in Geotechnical Design Common Parameter used in Geotechnical Design

Parameters Symbols Remarks Parameters Symbols Remarks

Undrained Shear Strength S or C (kPa) Can be obtained from test: UU, CIU, CID, CPT, Vane Shear Coefficient of Lateral Pressure K , K , K o Applied to lateral pressure analysis
u
p
a
u
Effective Shear Strength ’ (kPa) Can be obtained from test: CIU, Shear Box Bearing Capacity Coefficient N , N , N q Associate with  (after Vesic, 1973)

c
2
Angle of Friction (soil)  (deg) Can be obtained from test: UU, CIU, CID (deg), for soft clay,  = 0° Concrete Grade f cu (N/mm ) Compression test
Effective Angle of Friction ’ (deg) Can be obtained from test: CIU Poisson Ratio  E1 / E : where E1 = lateral strain, E = is axial strain
Stress, Effective Stress , ’ (kPa) ’ =  - u Soil Modulus E Cohesionless Soil = 500 ( N+15 )
Friction Ratio Fr Can be obtained from test: CPT (cohesive soil only) Angle at slope & friction between ,  Consider while analysing the lateral force
soil
N-value N Can be obtained from test: Standard Penetration Test
Pore Water Pressure u (kPa) The difference between the total and effective stresses
Force F (kN) Applied load
Permeability k Darcy Law
Pre–Consolidation Pressure P (kPa) Can be determined using Casagrand Method
c
Working Load (Design Load) WL (N) Live Load + Dead Load
Compression Index C c Typical range: 0.1 – 10 2
Coeff. of Compressibility Mv (m /kN) For high organic alluvial clays & peat ≥ 1.5 x 10 m /kN Applied Stress Pressure on subsoil q (kN/m ) Traffic load
3
2
2
Allowable Capacity Q (kN)
Compression Ratio C r C / (1+e ) a Factor of Safety = Q / Q
o
c
Ultimate Bearing Capacity Q (kN) u a
u
Swell Index C (%) Increase in soil volume, without external constraints, on submergence in
s
2
2
2
water Allowable Ultimate End Bearing q (N/mm ) Weak Rock = 1.5 N/mm , Medium Rock = 2 - 7 N/mm , Fresh Rock = 10 N/
a
mm 2
Coeff. of Horizontal Consolidation C (m /yr) C = 2C (C = Coeff. of Vertical Consolidation)
2
h
v
v
h
Unconfined Compressive Strength q u Unconfined Compression Test (For hard material & rock)
Time Factor Tv (year) exp: from consolidation analysis, the time factor at 90% consolidation is
0.848. Base Resistance f (kPa) Limit both f & f to about 100 kPa & 10000 kPa respectively for the design of
b
b
s
Specific Gravity Gs For soils composed of “particles smaller than 4.75mm in size”. Shaft Resistance f (kPa) driven & bored piles
s
2
2
Degree of Consolidation U (%) (e – e ) / (e – e ) : degree of consolidation at a particular time t at depth z Adhesion Factor   = 1.0 for C < 25kN/m ,  = 0.5 for C > 75kN/m (for clay)
u
u
o
t
1
o
Cross-section Area of Pile Tip A (m ) r of base (spun pile) or width x width (square pile)
2
2
b
Void Ratio e o Volume of Void / Volume of Solid; e =Gs x moisture content
o
Shaft Area A (m ) 2r x shaft length (spun pile) or 4 x width x shaft length (square pile)
2
Atterberg Limits LL, PL, PI Lab test for Liquid Limit & Plastic Limit, Plastic Index = LL – PL s
Soil Density, Bulk Unit Weight , ’,  (kN/m ) exp: for well compacted granular soil
3
b
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