ADVANCED GEOTECHNICAL ENGINEERING
Report 2
Running Head: Report
[Name]
[Institute]
[Date]
Table of Contents Part 1: 4 PART 2 7 PART 3 12 Geometry Model 13 Mesh Generation 13 Groundwater Table Allocation 14 Deformed Mesh 14 Total Displacements 15 PART 4 16 Piled Raft Analysis Methods: 16 Randolph method: 16 Settlement ratio method: 18 Poulos-Davis-Randolph Method: 19 PART 5 21 PLAXIS SIMULATION 21 Geometry Model 21 Groundwater Table 22 Deformed Mesh with Total Displacement 23
Part 1:
PART 2
Performance of your monopile under the working loads, Relevant Elastic Solutions
Performance of your monopile under the working loads, Relevant Elastic Solutions for variable soil properties
PART 3
The problem has been modeled in PLAXIS 2D. The monopile has been defined as the plate element while the properties of pile have been extracted from the literature.
The soil properties from the literature are extracted as given below;
E = 2.35 x 107 kN/m2 (Plate element)
Diameter of pile = 5m
Length of pile as 15 m
Sandy Silt Properties
Cohesion = 5 kN/m2
Angle of friction = 300
Soft Clay
Cohesion = 5 kPa
angle of friction = 25o
Elastic modulus = 4000 kPa
The stepwise Plaxis 2D simulation and results are given below
Geometry Model
Mesh Generation
Groundwater Table Allocation
Deformed Mesh
Total Displacements
PART 4
Piled Raft Analysis Methods:
Randolph method:
The Randolph method has been adopted for piled raft analysis. A 3 x 3 pile group wirth a raft has been designed and analysied for the given problem. The soil profile is same as given in the problem.
The properties from the literature has been extracted for the design and analysis of piled raft.
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Settlement |
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Stiffness of piled raft |
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Load sharing ration between pile group and piled raft |
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Loading sharing ration between raft and pile group |
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Kr(poulos and davis 1974) |
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Kp |
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Kpg |
Kp x (n)^0.5 Here n = number of piles |
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Terms used |
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Terms used |
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Settlement ratio method:
The method is same as Randolph and uses ranolph’s Kp formula. But for calculation of Kpg the below formula is used.
Here
e= e1 x c1 x c2 x c3 x c4
and K1 = stiffness of single pile calculated using Randolph’s equation.
Poulos-Davis-Randolph Method:
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Settlement |
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Stiffness of piled raft |
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Load sharing ration between pile group and piled raft |
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Loading sharing ration between raft and pile group |
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Interaction factor |
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Terms used |
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Using above equations in an excel sheet to predict the bearing capacity and settlement for the problem.
As it can be seen that total settlement computed from two methods is 173 mm approximately.
PART 5
The problem is modelled in PLAXIS 2D and the results have been displayed below. 3 x 3 group of piles is simulated with raft. The rafy and piles have been modelled as plate element in the PLAXIS 2D. The Elastic modulus of raft and piles for simulation are taken as 2.35 x 107 kN/m2. The plate element is modelled as linear elastic material model.The load pof turbine is simulated as uniformly distributed load. The cohesion and angle of internal friction with young’s modulus properties are same as described in PART 3 above.
PLAXIS SIMULATION
Geometry Model
Groundwater Table
The groundwater table location is set as the ground surface.
RESULTS
Deformed Mesh with Total Displacement
Figure 1 Load- Settlement Curve
Figure 2 Load Settlement Curve at Different points
From the results it is obvious that the settlement computed from manual procedures as explained in PART 4 is in good agreement with the numerical simulation of PLAXIS 2D. the settlement computed from manual procedures is 173 mm while the settlement computed from the PLAXIS 2D is 156 mm. The difference in values is acceptable as FE analysis differs in some manners from the manual computations.
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