typical examples for soil structure interaction …
TRANSCRIPT
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APPLICATION OF SOIL - STRUCTURE
INTERACTION ANALYSIS IN
FOUNDATION DESIGN
BY
DR.S.R.GANDHI
Director
Sardar Vallabhbhai National Institute Of Technology, Surat
Email: [email protected]
TYPICAL EXAMPLES FOR
SOIL – STRUCTURE INTERACTION
ANALYSIS
1. SHALLOW FOUNDATION
2. EARTH PRESSURE BEHIND RETAINING WALL.
3. PILE SUPPORTED STRUCTURE SUBJECTED
TO LATERAL LOADS.
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Top-Down and Bottom-up Construction- a case study
• Large sized basements
• Difficulties in Strutting
• Basement floors of limited width used for suproting the wall
• Use of Sacrificial Steel Piles to support basement
floors temporarily
• Monitoring of deflections during excavations
• Construction of Permanent Columns
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CONCLUSIONS This case study helped to understand the behaviour of
Diaphragm wall and the temporary piles. The shear resistance of the inner pile is higher than the
outer pile due to more free length of the outer pile. There is a reduction in wall displacement due to the
presence of the basement slab which behaved like a strut and it provided fixity to the steel pile head
The soil-structure-interaction analysis using 3D PLAXIS was very useful to check the adequacy of the temporary piles which provided vertical support to the basement slab and the lateral support to the diaphragm wall during the excavation.
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FEM ANALYSIS (..3)
FIXITY BELOW ACTIVE ZONE
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SPRING SUPPORT BELOW
PROBABLE FAILURE (..2)
Failure of piles in the approach
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Corrosion of outer row of piles in Haddo Wharf
METHODS TO FIND SPRING STIFFNESS:
1. OBTAIN ES VALUES FOR EACH LAYER BASED ON SPT (N).
2. USE VESIC’S EQUATION TO GET MODULUS OF SUBGRADE FOR EACH LAYER.
3. USE NEWMARK’S EQUATION TO ARRIVE AT SPRING STIFFNESS
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VESIC’S EQUATION:
Where Es = modulus of soil
Ef = Modulus of footing
B = Footing width
If = moment of inertia based on cross section
212
4
165.0
s
ff
ss
E
IE
BEk
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TABLE 1. CALCULATION OF SPRING CONSTANTS
Level SPT
Value Es(t/m
2) 1300 & 1000 Piles
(t/m)
Diaphragm Wall
( 4 m panel )
(t/m)
+ 1.0 10 2850 2704 1352 3545 1773
0.0 10 2850 2704 2704 3545 3545
- 1.0 10 2850 2704 2892 3545 3793
- 2.0 20 5000 4972 4783 6517 6269
- 3.0 20 5000 4972 4972 6517 6517
- 4.0 20 5000 4972 4567 6517 5986
- 5.0 3 150 111 921 146 1208
- 6.0 20 5000 4972 4567 6517 5986
- 7.0 20 5000 4972 4972 6517 6517
- 8.0 20 5000 4972 4883 6547 6400
- 9.0 15 4000 3904 3993 5118 5235
- 10.0 15 4000 3904 3904 5118 5118
- 11.0 15 4000 3904 3904 5118 5118
- 12.0 15 4000 3904 3613 5118 4736
- 13.0 10 500 410 701 538 920
- 14.0 10 500 410 912 538 1197
- 15.0 30 6350 6441 5938 8444 7785
- 16.0 30 6350 6441 6346 8444 8319
- 17.0 23 5300 5296 5391 6942 7067
- 18.0 23 5300 5296 5296 6942 6942
- 19.0 23 5300 5296 5296 6942 6942
- 20.0 23 5300 5296 5484 6942 7180
- 21.0 40 7350 7547 7476 9893 9800
- 22.0 60 8600 8947 8830 11728 11575
- 23.0 60 8600 8947 4532 11728 5940
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