1. Aspek Geoteknik

2. Type of Foundation

3. Summary of types of shallow foundations

4. Factors of safety (modified after Vesic 1975)
Category
Typical Structure
Observations
Soil exploration
Through
Limited A
Railway bridges
Warehouses
Balst furnaces
Reaining walls
Silos
Maximum design load
likely to occur often
Ultimate limit states with
disastrous consequences 3 4 B
Highway bridges
Light industrial and public
buildings
Maximum desighn load
may occur occasionally
serious consequences
2.5
3.5 C
Apartement Buildings
Office Buildings
unlikely to occur 2

5. Safety Factor Method for Determine Bearing Capacity Load
Minimum Safety Factor
Compression
Tensile
Theory or empirical + loading test
1. Dead Load, live load and water pressure
2. Dead Load, Live Load Earthquake Load and Flood 50 years
2,50
1,50
Theory or empirical + PDA Test
3,00
2,00
Theory or empirical without Loading test and PDA Test
3,50
2,25

6. Acceptable Probability of Failure Design Factor of Safety, F
Classification of Structure
Acceptable Probability of Failure
Design Factor of Safety, F
Good Control
Normal Control
Poor Control
Very Poor Control
Monumental
10-5
2,3
3,0
3,5
4,0
Permanent
10-4
2,0
2,5
2,8
3,4
Temporary
10-3
1,4

7. Load
Maximum Lateral Defflection
Service Load without earthquake load
1,27 cm (0,5 “)
Service Load with earthquake load
1,905 cm (0,75”)
Ultimate Load
3,5 cm

8. Typical Allowable Total Settlement, a
Type of Structure
Typical Allowable Total Settlement, a
(in)
(mm)
Office buildings
0,5-2,0 (1,0 is the most common value)
12-50 (25 is the most common value)
Heavy industrial buildings
1,0-3,0
25-75
Bridges
2,0 50

9. Differential Settlement
Ratio of maximum total settlement Wmax to maximum angular distortion max ( modified after Skempton and MacDonald 1956)
Soil type
Isolated foundations
Mat foundations
Sand / sand fill
15 LR
20 LR
Clay
25 LR
30 LR
LR = reference length = 1 m  40 in.
Tolerable angular distorsion for special – purpose structures
Structure
 = w/L
Machines
Frames with diagonels
Overhead cranes
Tilt of tall buildings/ structures
Steel tanks
1/750
1/600
1/300
1/250
1/25

10. θa Type of Structure 1/25 Steel tanks 1/125
Bridges with simply-supported spans
1/125
Bridges with continous spans
1/250
Buildings that are very tolerant of differential settlements, such as industrial buildings with corrugated steel siding and no sensitive interior finishes
Typical commercial and residential buildings
1/500
Overhead traveling crane rails
Buildings that are especially intolerant of differential settlement, such as those with sensitive wall or floor finishes
1/1000
Machinery
1/1500
Buildings with unreinforced masonry load-bearing walls
Length/height ≤ 3
Length/height  5
1/2500
1/1250

11. Geotechnical Concerns
To determine the approximate minimum depth of boring, engineers may use the rules established by the American Society of Civil Engineers (1972):
Determine the net increase in the effective stress, ’, under a foundation with depth as shown in figure.
Estimate the variation of the vertical effective stress, ’0, with depth.
Determine the depth, D = D1, at which the effective stress increase ’ is equal to 0,1q (q = estimated net stress on the foundation).
Determine the depth, D = D2, at which ’/’0 = 0,05.
Choose the smaller of the two depths, D1 and D2, just determined as the approximate minimum depth of boring required, unless bedrock is encountered.

12. GEOTECHNICAL CONCERNS
Two types of soil samples can be obtained during subsurface exploration :
Disturbed
Undisturbed
Disturbed, but respresentative, samples can generally be used for the following types of laboratory test :
Grain-size analysis
Determination of liquid and plastic limits
Specific gravity of soil solids
Determination of organic content
Classification of soil
Undisturbed soil samples must be obtained for these types of laboratory tests such as :
Consolidation
Hydraulic conductivity
Shear strength tests

13. No. of stories
Boring depth 1
3,5 m (11 ft) 2
6 m (20 ft) 3
10 m (33 ft) 4
16 m (53 ft) 5
24 m (79 ft)
Type of project
Spacing
Multistory building
10-30 m ( ft)
One-story building
20-60 m ( ft)
Highways
m ( ft)
Residential subdivision
Dams and dikes
40-80 m ( ft)

14. Average Properties of Cohesionless Soils
Relative Density
Blow Count, N,
(blows / ft)
Voila Ratio, e
Simple Field Test with ½ -in. Diameter Rod
Usable Bearing Strength
( k / ft2 )
( kPa )
Loose
< 10
Easily pushed in by hand
0-1.0
0-50
Medium
10 – 30
Easily driven in by hammer
50-100
Dense
30 – 50
Driven in by repeated hammer blows
75-150
Very dense
> 50
Barely penetrated by repeated hammer blows

15. Average Properties of Cohesive Soils
Consistency
Unconfined Compressive
Strength (k/ft2)
Simple Field Test by Handling of an Undisturbed Sample
Usable Bearing Strength
( k / ft2 )
( kPa )
Very soft
< 0.5
Oozes between fingers when
squeezed
Soft
0.5 – 1.0
Easily molded by fingers
25 – 50
Medium
1.0 – 2.0
Molded by moderately hard
squeezing
1.0 – 1.5
50 – 75
Stiff
2.0 – 3.0
Barely molded by strong
50 – 100
Very stiff
3.0 – 4.0
Barely dented by very hard
1.5 – 3.0
75 – 150
Hard
4.0 or more
Dented only with a sharp
instrument
3.0 +
150 +