Upload
phungdat
View
216
Download
0
Embed Size (px)
Citation preview
1/12/2012
1
Design and Construction of Deep basements
Eng. Shiromal Fernando Chartered Engineer
Presentation Overview
• Design Considerations • Retaining system Design • Design of Dewatering system • Decide on waterproofing system • Decide on concrete properties/ Issues • Construction Issues
1/12/2012
2
Design Considerations
Design Consideration
• Depth of excavation • Nature of soil ( type of soil and its permeability)
• Chemical content of the soil • Water table ( Permanent and Temporary) • Adjacent structures • Excavation Methodology • Basement Details
1/12/2012
3
Subsurface Information
• WATER TABLE
• FINE CLAYEY SAND WITH VERY HIGH SPT VALUES
• SOIL PERMEABILITY
• SULPHATE ( % mass/mass as SO3‐2 )
• CHLORIDES (mg/kg as Cl ‐1)
1/12/2012
4
BOREHOLE DETAIL
ROCK LEVEL
N > 50
N =15 N =18
N =11
N = 5
N > 50 N = 22
N = 28 N > 50
N > 50
N > 50
N > 50
N > 50
N > 50
N > 50
N > 50
0 m
2
4
14
6
8
10
12
16
18
20
24 22
26
28
30
32
34
W.T BASEMENT -3 MSL
Depth of Excavation
1/12/2012
5
3 m
1 m
30°
4.875 m
EXISTINGBUILDING
EARTH RETAININGSYSTEM
BUILDINGPROPOSED
TEMPORARY EARTH RETAINING SYSTEM (DESIGN CRITERIA)
Adjacent Building Structures
1/12/2012
12
CHEMICAL GROUTING???
• STABILIZE THE SOIL BEYOND THE SHEET PILE LINE.
• MIXTURE OF CEMENT, WATER & SODIUM SILICATE.
• INJECTED TO SOIL IN 1‐1.5m INTERVALS.
1/12/2012
29
Temperature issues in thick elements
• Limit Peak Hydration Temperature to 70 C • Limit Cement content to 400 Kg/m^3 • Keep the initial placing temperature to 30 C • Note do not cure till 4days ( Protect concrete from rain)
• Use Mineral admixtures for to reduce the thermal gradiant
Measuring of temperature at CCR using Thermocouples
1/12/2012
30
Measuring of temperature at CCR using Thermocouples……..
Metal wires
Temperature variation -zone D
0
20
40
60
80
100
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184
Cumulative time(hours)
Tem
pera
ture
('C)
E1 E2 E3 C1 C2 C3
C1‐Bottom point at the centre, C2‐ middle point at the centre,C3‐ top point at the centre, E1‐ Bottom point at the Edge, E2‐Middle point at the edge, E3‐ top point at the Edge