Input Parameters
Input parameters pane specifies the dimensions, properties of the pile, pile group and soil. These are entered in their respective tabs. If field pile load test data is available, it can be entered in the ‘field test data’ tab.
Pile Dimensions Tab
Pile Dimensions tab defines the pile type, cross-section of the pile and the dimensions of the pile for the foundation. It also displays a pictorial view of the pile along with the layers of soil.
Pile Type
Select the pile type (method of construction) used for the project in the pile dimensions tab. The choices for pile types are
a) Driven
b) Bored (Bored cast-insitu)
c) CFA (Continuous flight auger)
d) Driven Cast-insitu
The method of construction along with the pile cross-section and pile material is used to determine the default values for 'k earth pressure coefficient' for sand layers.
The table below describes the practical choices for pile method of construction, pile cross-section and material used. The application may give warnings (which may be ignored by the user) if the selections don’t adhere to the table below.
Table 1 Pile type, cross-section, material compatibility matrix
|
Pile Type |
Driven |
Bored |
CFA |
Driven Cast-insitu |
|
|
Pile Cross-section |
Hollow Circular H-Section |
Square Rectangular Hollow Circular |
Full Circular |
Full Circular |
Full Circular |
|
Construction material |
Steel |
Concrete |
Concrete |
Concrete |
Concrete |
Pile Cross-Section
Select the pile cross-section to be used for the project in the pile dimensions tab. The choices for pile cross-section are
a) Full circular pile
b) Square pile
c) Rectangular pile
d) Hollow circular pile
e) H Section pile
Based on the cross-section of the pile, define the parameters of the pile in the adjacent pile dimensions pane.
The application may give warnings (which may be ignored by user) if the selections don’t adhere to the Table 1Pile type, cross-section, material compatibility matrix described in 'Pile Type' section.
Table 2 Summary of parameters to be specified for the different pile cross sections.
|
|
Full Circular pile |
Square pile |
Rectangular pile |
Hollow Circular pile |
H Section pile |
|
Pile length |
✓ |
✓ |
✓ |
✓ |
✓ |
|
Pile length above ground |
Optional |
Optional |
Optional |
Optional |
Optional |
|
Number of elements |
✓ |
✓ |
✓ |
✓ |
✓ |
|
Pile diameter |
✓ |
|
|
✓ |
|
|
Diameter of base |
Optional |
|
|
|
|
|
Pile wall thickness |
|
|
|
✓ |
|
|
Sectional breadth |
|
✓ |
✓ |
|
✓ |
|
Sectional depth |
|
|
✓ |
|
✓ |
|
Sectional area |
|
|
|
|
✓ |
|
Moment of inertia about x-axis |
|
|
|
|
✓ |
|
Moment of inertia about y-axis |
|
|
|
|
✓ |
Pile length
Specify the pile length here in the units chosen. After selecting the pile cross-section, this should be the first item to be entered on this page. This field is mandatory for all pile cross-sections.
Note: For TRIAL version, Pile length is restricted to 6m (19.6ft)
Pile length above ground
Specify the length of the pile length above the ground here in the units chosen. This field is optional and applicable for all pile cross-sections.
Number of elements
This is the guidance of number of elements used in the finite element calculation. The program may adjust this number based on the other input data to carry out the analysis. A higher number of elements will improve granularity but may result in some loss of fidelity. The default value of 50 elements is recommended.
Use the slider to select the number of elements. A minimum of 20 elements and a maximum of 100 elements are permitted. This field is applicable for all pile cross-sections.
Pile diameter
Specify the external diameter of the pile here in the units specified. This field is mandatory for Full circular pile and Hollow Circular Pile.
Diameter of base
Specify the diameter of base of the pile here in the units specified if different from the pile diameter. This is usually required for piles with enlarged bases. This field is optional and can be specified only for full circular pile.
Pile thickness
Specify the pile wall thickness of the pile in the units specified. This field is mandatory and applicable for hollow circular pile.
Sectional breadth
Specify the sectional breadth the pile here in the units specified. This field is mandatory for Square pile, Rectangular pile and H Section pile.
Sectional depth
Specify the sectional depth the pile here in the units specified. This field is mandatory for Rectangular pile and H Section Pile.
|
Square Pile |
Rectangular Pile |
H Section Pile |
|
|
|
|
Sectional area
Specify the sectional area the pile here in the units specified. This field is mandatory for H Section pile. The default value displayed here is calculated for a H-section pile with a 1” thickness.
Moment of inertia about X-axis
Specify the moment of inertia of the pile about X-axis here in the units specified. This field is mandatory for H Section Pile.
Moment of inertia about Y-axis
Specify the moment of inertia of the pile in Y-axis here in the units specified. This field is mandatory for H Section Pile.
Pile Diagram
The pile diagram displays the pile along with all the layers of soil. Different scales are used for the depth axis and horizontal axis. The pile length in the diagram is 20 m. This diagram shows the perspective view of the pile along with the different layers of soil, scour and depth of water table.
Pile Properties Tab
Pile properties tab is used for specifying the properties of the pile material and self-weight inputs.
Pile Material Properties
Use the dropdown menu to select the material used for the pile. The elastic modulus of the pile along with the unit weight is updated based on the selection.
Table 3 Elastic modulus of pile
|
Pile Material |
Elastic Modulus |
|
|
(kN/m3) |
(kips/ft3) |
|
|
Steel |
|
|
|
ASTMA36 |
2.0*108 |
4.173 * 106 |
|
Concrete |
|
|
|
M20 |
3.0 * 107 |
6.26 * 105 |
|
M25 |
3.1 * 107 |
6.47 * 105 |
|
M30 |
3.3 * 107 |
6.68 * 105 |
|
M35 |
3.4 * 107 |
7.10 * 105 |
|
M40 |
3.5 * 107 |
7.31 * 105 |
|
M45 |
3.6 * 107 |
7.52 * 105 |
|
M50 |
3.7 * 107 |
7.73 * 105 |
Select the “User Defined” option to enter values for the elastic modulus and unit weight of the pile material.
Elastic modulus of pile
The elastic modulus of pile is shown here based on the material specified. If “User Defined” material is selected, the elastic modulus of the pile can be edited and entered here.
Unit weight of material
The unit weight of pile material of pile is shown here based on the material specified. If “User Defined” material is selected, the ‘unit weight of material’ can be edited and entered here.
Self-weight inputs
The self-weight properties could be taken into account for axial analysis of the pile. The values of self-weight are auto-calculated based on the pile dimensions and soil properties or they could be user-defined.
Effective pile weight
The automatically calculated ‘Effective pile weight’ is shown here as default value. Effective pile weight accounts for the reduction in pile weight due to buoyancy effect of water. This will be used for ‘self-weight’ analysis if required. To enter a user defined value of ‘effective pile weight’, select the checkbox adjacent to this and enter the user defined value in the ‘text field’ next to it.
Plug weight
The automatically calculated plug weight is shown here. The automatic calculation is based on the different soil layers and the inner diameter of the bottom segment of the pile. This is only relevant for driven hollow piles. A 0.9 reduction factor is used in calculating the plug weight. This will be used for ‘self-weight’ analysis if required. To enter a user defined value of plug-weight, select the checkbox adjacent to this and enter the user defined values in the ‘text field’ next to it.
Pile Group Data
The Pile Group Data tab is used to enter the data required for the 'Pile group settlement analysis'
Pile Group Cap
Select the 'Pile Group Cap'. Choices include
· Rigid cap
· Flexible cap
Pile Geometry
Select the arrangement of the piles in the group. The two choices currently are
· Grid
· User Defined
If the 'Grid' option is selected, a new pane will be visible and require the user to fill the Grid Details. The 'Pile Placement in Group' Table will then be updated with the placement of the piles in the group.
If the 'User defined' option is selected, the user will need to update the 'Pile Placement in Group' with the details of each pile.
Grid Details
Enter the number of rows, columns, spacing between the rows and spacing between the columns to define the grid. Click on 'Generate grid' to generate the grid and to update the 'Pile Placement in Group' with the location of each pile in the grid.
Each time the user changes any entry the 'Grid Details' pane, the 'Generate grid' button should be clicked to update the ''Pile Placement in Group' table.
Pile Placement in Group
The 'Pile Placement in Group' table is used to define the placement of individual piles in the group.
Use the (+) and (-) buttons at the top of the table to add / delete rows to the 'Pile Placement in Group' table. This option is only visible for 'User defined' pile geometry.
[Organize] button can be used to sort the values by Pile x-coordinate and to clean up empty entries in the table. This option is only visible for 'User defined' pile geometry.
Up to 500 Piles can be part of the group.
Table:
Double-click on the table cells to edit the content of the cells.
The table consists of four or five columns: No., Pile designation, Pile x-coord, Pile y-coord, Pile head load.
‘No.’ column cannot be edited and displays the entry index.
Pile designation Column – Description to identify the pile in the group.
Pile x-coord – x-coordinate location of the pile. Should be >=0. This column can be edited if 'User defined' Pile Geometry is selected in the adjacent pane. If 'Grid' is selected in the adjacent 'Pile Geometry', this field is generated and cannot be edited.
Pile y-coord – y-coordinate location of the pile. Should be >=0. This column can be edited if 'User defined' Pile Geometry is selected in the adjacent pane. If 'Grid' is selected in the adjacent 'Pile Geometry', this field is generated and cannot be edited.
Pile head load – Enter the vertical load on the pile head for each pile in this column. This column is visible and editable only in the case of piles with 'Flexible cap' and where 'Different load on piles' is selected in the 'Pile Group Loading' pane below.
Right click on the table to bring-up the context menu to insert / delete rows in the table, cut, copy, delete and paste contents into the table. It is also possible to copy the table from excel and paste the contents into this table. Ensure adequate number of empty rows are added to the table prior to pasting contents from an excel table.
Pile Group Loading for Pile Group with Rigid cap
Load on pile cap – Enter the load applied on the pile cap. By default, the load is applied at the centroid location of the piles.
To apply the load at a different point, indicate the shift in the loading point from the centroid by specifying the 'eccentricity in x direction' and the 'eccentricity in y direction'.
Pile Group Loading for Pile Group with Flexible cap
Same load on all piles – Enter the 'Pile head load' in the text field adjacent to this option. This load will be applied on the pile head of all the piles in the group.
Different load on all piles – Select this option to specify different loads on each pile. The loads for each of the piles need to be specified in the 'Pile head load' column of the 'Pile Placement in Group' table above.
Pile Group Cross-Section Diagram
The Pile group cross-section diagram displays the view of the pile group from the top.
Pile Group Diagram
The Pile Group Diagram displays the 3-D cabinet view of the pile group showing. For Rigid cap, load on the pile-cap is also displayed. For Flexible-cap, loads on each pile are displayed if the number of piles is less or equal to 5.
Soil Properties Tab
Data in the soil properties tab is used to compute the pile capacity, design load for the pile, design load pile head settlement and the base stiffness of the soil at the pile tip.
If limit state design approach is used (i.e., design load is set as 1), factored soil properties must be used in this tab.
If the load test results carried out on a single pile on site is available, the load test data can be used along with base soil properties. Refer the ‘Field test data’ section. The base soil properties are also entered in the field test data section.
Soil properties tab is used to enter the details of soil layers, and standard penetration test (SPT) data. The tab is further subdivided into 2 tabs (on right hand side)
· SPT
Soil Properties Tab > Soil Layers Tab
Soil Properties Tab is used to enter the data about the site condition, sub-soil layers and properties of each soil layer. It is divided into 3 panes
Soil Properties Tab > Soil Layers Tab > Site Condition
Scour depth
This field is not mandatory. Specify the local scour around the pile at the site. Enter the ‘scour’ value in the field.
Some restrictions on the scour depth:
· Scour depth can extend up to the first three layers of soil
· Scour depth should be less than 2.5 times of diameter of the pile
· Scour cannot extend into a rock layer.
Depth of water table
This field is not mandatory. Specify the depth of water table at the site in the field provided.
If no value is specified, it is assumed the water table lies below all the layers of soil specified. For water table at ground level, set it as 0.
Critical depth ratio (Zc)
Specify the value of ‘Critical depth ratio’ (zc/d) in the field provided.
Zc is the ratio of depth to diameter of pile beyond which the vertical and lateral effective stresses are considered to remain constant up to the pile base. The usual values are Zc = 15 for loose sand and 20 for dense sand.
Critical depth ratio’ is required for Pile capacity estimation in ‘Sand soil’ when the limiting side friction and base resistance are determined by the values computed at the critical depth. This method is followed in IS-2911. The software also adopts this method for limiting base resistance determined by ‘Nq - Berezantev – Zc’ method. The table below summarizes the scenarios under which Zc is required.
Table 4 Scenarios where ‘critical depth ratio’ is required
|
|
Method for maximum base resistance |
|||||
|
Nq - qlim method (API-2011, API-2000) |
Nq-Zc method (IS-2911) |
Nq -Berezantev - Zc method |
Meyerhoff SPT method (IS-2911) |
Meyerhoff SPT method for silty sand (IS-2911) |
||
|
Method for maximum side friction |
β method (API-2011) |
|
✓ |
✓ |
|
|
|
K - δ method (API-2000) |
|
✓ |
✓ |
|
|
|
|
K - δ - Zc method (IS-2911) |
✓ |
✓ |
✓ |
✓ |
✓ |
|
|
Meyerhoff SPT method (IS-2911) |
|
✓ |
✓ |
|
|
|
|
Meyerhoff SPT method for silty sand (IS-2911) |
|
✓ |
✓ |
|
|
|
Min value: 15
Max value: 20
Default value: 15
Unit weight of water
Specify the unit weight of water in the field provided. This parameter is a mandatory field.
Min value: 9.5 kN/m3 or 0.062 kips/ft3
Max value: 10.5 kN/m3 or 0.067 kips/ft3
Default value: 9.8 kN/m3 or 0.063 kips/ft3
Soil Properties Tab > Soil Layers Tab > Soil Layer Table
The ‘Soil Layer Table’ is used to define the type of soil and the thickness of each layer of soil. The properties of the soil layer selected is entered in the adjacent ‘Soil Layer Properties’ pane.
Number of soil layers
First select the number of soil layers using the up/down arrow. This will set the number of rows in the table to populate
Up 50 soil layers can be specified.
Note: For TRIAL version, number of soil layers is restricted to 3.
Table: Double-click on the table cells to edit the content of the cells.
The table consists of four columns – Layer, Soil type, Starting depth and Layer thickness. The ‘Layer’ column and the ‘Starting depth’ columns cannot be edited.
To enter the Soil type, click on the cell in this column and select the type of soil from the ‘drop down’ menu for each segment.
Permissible soil types currently are – Soft Clay, Stiff Clay, Sand, Weak Rock and Hard Rock.
You can use ‘Sand’ to represent silt, silty sand and gravel as well.
Layer thickness Column – This defines the thickness of each layer of soil.
Starting depth Column – This column is auto calculated based on the thickness of soil layers entered.
The pile diagram in the pile dimensions tab will graphically show the values entered in this table.
Note: Soil layers should extend up to pile depth below ground + n * effective diameter
n = 3 for pile terminating in soil
n = 1 for pile terminating in rock.
Soil Properties Tab > Soil Layers Tab > Soil Layer Properties
Select a layer in the ‘Soil layer table’ to display the soil properties associated with it in this pane.
Note: Mandatory
fields have a (
) adjacent to them.
Note: The soil layer properties need to be arrived at from the soil investigation report. The application populates median recommended values for each property. These values need to be updated with actual values from the soil investigation report or values chosen by the user.
Common properties for all soil types:
Soil type: Shows the type of soil in this layer. (Field cannot be edited)
Unit weight of soil (γ): The unit weight to be given as data is the total unit weight of soil in the layer that is the moist unit weight above the water table and saturated unit weight below the water table. If required one may choose to divide the layer in to two halves one above water table and the other below the water table having different unit weights.
Starting depth: Displays the starting depth of the layer. (Field cannot be edited)
Layer thickness: Displays the thickness of the selected layer. (Field cannot be edited)
Properties for Clay soil
Pile group settlement of clay soil
Method for maximum side friction: The table below details the options available for Soft Clay and Stiff Clay soil.
Table 5 Details of ‘Method for maximum side friction’ for clay soil
|
Method for maximum side friction |
Notes |
|
API-2011 |
(API 2011 Geotechnical and Foundation Design Considerations April 2011, Addendum 1, 2014) |
|
a method (IS-2911) |
(IS 2911 Design and construction of pile foundations - Code of Practice (Part 1. Sections - 1,2&3) 2010) |
|
Semple & Ridgen (1984) |
(Semple and Rigden 1984) |
|
Kolk & Van Der Velde (1996) |
(Kolk and van der Velde 1996) |
The maximum unit shaft friction 
of clay soil layers is based on the equation
Where α is a multiplier and 
is the undrained cohesion of the soil. Methods of
estimating the α multiplier by the following four methods are available in the software:
1) API RP GEO 2011
In this
2) α method (IS 2911)
Curve
relating the 
given in the Standard
is made use of.
3) Semple & Rigden (1984)
4) Kolk& van der Velde (1996)
Base resistance in cohesive soil layers
The unit base resistance is given by
Properties for Soft Clay soil
Pile group settlement of soft clay soil
Method for maximum side friction: Select the method for maximum side friction from the dropdown list. This parameter is mandatory for Pile group settlement analysis.
Table 6 Details of ‘Method for maximum side friction’ for soft clay soil
|
Method for maximum side friction |
Notes |
|
API-2011 |
(API 2011 Geotechnical and Foundation Design Considerations April 2011, Addendum 1, 2014) |
|
a method (IS-2911) |
(IS 2911 Design and construction of pile foundations - Code of Practice (Part 1. Sections - 1,2&3) 2010) |
|
Semple & Ridgen (1984) |
(Semple and Rigden 1984) |
|
Kolk & Van Der Velde (1996) |
(Kolk and van der Velde 1996) |
For more details on the methods, refer to the section on 'Method for maximum side friction' under 'Clay Soil'.
Table 7 Required properties for ‘Pile group settlement analysis’ for soft clay soil with respect to 'Method for maximum side friction'
|
Method for maximum side friction |
Cohesion at top |
Cohesion at bottom |
|
API-2011 |
✓ |
✓ |
|
α method (IS-2911) |
✓ |
✓ |
|
Semple Rigden |
✓ |
✓ |
|
Kolk & Van der Velde |
✓ |
✓ |
Axial analysis method: Select the ‘Axial analysis method’ using the ‘drop down menu’ for axial load analysis.
Table 8 Axial analysis method details for Soft Clay
|
Axial analysis method |
Method details |
|
API-2000 |
(API 2000 RP2A-WSD 2000) |
|
API-2011 |
(API 2011 Geotechnical and Foundation Design Considerations April 2011, Addendum 1, 2014) |
|
Elastic method |
Based on elastic properties of soil. |
Table 9 Required properties for ‘Pile group settlement analysis’ for soft clay soil with respect to 'Axial analysis method'
|
Axial analysis method |
Cohesion at top |
Cohesion at bottom |
R factor |
Elastic modulus |
Poisson ratio |
|
API-2011 |
✓ |
✓ |
✓ |
||
|
API-2000 |
✓ |
✓ |
✓ |
||
|
Elastic Code |
✓ |
✓ |
✓ |
✓ |
Table 10 Soil property details for soft clay soil
|
Soil property |
Units |
Min value |
Max value |
Notes |
|
Elastic modulus of soil |
kN/m2 |
1750 |
5000 |
|
|
kips/ft2 |
36.54 |
104.4 |
||
|
Poisson Ratio |
|
0.1 |
0.5 |
Default value: 0.5 |
|
Cohesion at top |
kN/m2 |
0 |
100 |
Value of 0 is only permissible for the first soil layer. |
|
kips/ft2 |
0 |
2.09 |
||
|
Cohesion at bottom |
kN/m2 |
> 0 |
100 |
|
|
kips/ft2 |
> 0 |
2.09 |
||
|
R factor |
|
0.5 |
1.0 |
Default value: 0.9 |
Properties for Stiff Clay soil
Pile group settlement of stiff clay
Method for maximum side friction: Select the method for maximum side friction from the dropdown list. This parameter is mandatory.
Table 11 Details of ‘Method for maximum side friction’ for stiff clay soil
|
Method for maximum side friction |
Notes |
|
API-2011 |
(API 2011 Geotechnical and Foundation Design Considerations April 2011, Addendum 1, 2014) |
|
a method (IS-2911) |
(IS 2911 Design and construction of pile foundations - Code of Practice (Part 1. Sections - 1,2&3) 2010) |
|
Semple & Ridgen (1984) |
(Semple and Rigden 1984) |
|
Kolk & Van Der Velde (1996) |
(Kolk and van der Velde 1996) |
For more details, refer to the section on 'Method for maximum side friction' under 'Clay Soil'.
Table 12 Required properties for ‘Pile group settlement analysis’ for stiff clay soil with respect to 'Method for maximum side friction'
|
Method for maximum side friction |
Cohesion at top |
Cohesion at bottom |
|
API-2011 |
✓ |
✓ |
|
α method (IS-2911) |
✓ |
✓ |
|
Semple Rigden |
✓ |
✓ |
|
Kolk & Van der Velde |
✓ |
✓ |
Axial analysis method: Select the ‘Axial analysis method’ using the ‘drop down menu’ for axial load analysis.
Table 13 Axial analysis method details for stiff clay
|
Axial analysis method |
Method details |
|
API-2000 |
(API 2000 RP2A-WSD 2000) |
|
API-2011 |
(API 2011 Geotechnical and Foundation Design Considerations April 2011, Addendum 1, 2014) |
|
Elastic method |
Based on elastic properties of soil. |
Table 14 Required properties for ‘Pile group settlement analysis’ for stiff clay soil with respect to 'Axial analysis method'
|
Axial analysis method |
Cohesion at top |
Cohesion at bottom |
R factor |
Elastic modulus |
Poisson ratio |
|
API-2011 |
✓ |
✓ |
✓ |
||
|
API-2000 |
✓ |
✓ |
✓ |
||
|
Elastic Code |
✓ |
✓ |
✓ |
✓ |
Table 15 Soil property details for stiff clay soil
|
Soil property |
Units |
Min value |
Max value |
Notes |
|
Elastic modulus of soil |
kN/m2 |
4000 |
10000 |
|
|
kips/ft2 |
83.5 |
208.8 |
||
|
Poisson Ratio |
|
0.1 |
0.5 |
Recommended value Below water table: 0.5 Above water table: 0.4 |
|
Cohesion at top |
kN/m2 |
100 |
|
For the top layer, a value from 0 can be used. |
|
kips/ft2 |
2.09 |
|
||
|
Cohesion at bottom |
kN/m2 |
100 |
|
|
|
kips/ft2 |
2.09 |
|
||
|
R factor |
|
0.5 |
1.0 |
Default value: 0.9 |
Properties for Sand soil
Pile group settlement of sand
Method for maximum side friction: Select the method for maximum side friction from the dropdown list. This parameter is mandatory for Pile group settlement. The table below details the options available for Sand soil.
Table 16 Details of ‘Method for maximum side friction’ for sand
|
Method for maximum side friction |
Notes |
|
β method (API-2011) |
(API 2011 Geotechnical and Foundation Design Considerations April 2011, Addendum 1, 2014) |
|
K - δ method (API-2000) |
(API 2000 RP2A-WSD 2000) |
|
K - δ - Zc method (IS-2911) |
(IS 2911 Design and construction of pile foundations - Code of Practice (Part 1. Sections - 1,2&3) 2010) |
|
Meyerhoff SPT method (IS-2911) |
(IS 2911 Design and construction of pile foundations - Code of Practice (Part 1. Sections - 1,2&3) 2010) |
|
Meyerhoff SPT method for silty sand (IS-2911) |
(IS 2911 Design and construction of pile foundations - Code of Practice (Part 1. Sections - 1,2&3) 2010) |
1) The β - fmax method (API-2011)
In
this method is given by the
equation
in which β depends on
the density of the sand layer and pv’ is the vertical effective
stress. β values recommended by API range from 0.29 for medium dense sand to
0.56 for very dense sand. User defined value β could also be specified. This
method requires also a value of flim which is the limiting value for
tmax. API proposes flim values ranging from 67 kPa for medium dense
sand to 115 kPa for very dense sand. User defined value of flim could also be
prescribed.
2) K - δ - flim method (API-2000)
In
this method is given by the
equation
in which K is lateral
earth pressure coefficient, 
is the angle of
friction between the pile surface and soil and 
is the vertical
effective stress. The values of K and δ need to be specified by the user after due consideration of
type of soil, pile and method of installation. Some guidance values in this
regard are given in the appendix. API recommends a K value of 0.8 for open
ended pipe piles and 1.0 for closed ended piles. The recommended δ values range
from 15 degrees for very loose sand to 35 degrees for very dense sand.
Standards and literature would be of help in choosing the appropriate values of
K and δ. K and δ displayed in
the software are those recommended by the code for driven tubular piles.
3) K - δ - Zc method (IS 2911)
In
this method is given by the
equation
.The maximum vertical
effective stress is limited to the
value at the critical depth Zc. Zc /D ratio is
specified ranging from 15 for φ’ 
to 20 for φ’
. There is provision
for user defined values of δ, K and Zc
4) Meyerhoff SPT method (IS 2911)
In
this method 
for sand and 
for silty sand where 
is the average N value
for the layer.
