DEPTH INFLUENCE FACTOR

[uetian19]

Hello
I had been developing a spreadsheet for the calculation of Elastic settlements in foundations on granular soils using theory of Elasticity . I had problem for calculating "Depth Influence Factor" . I can only find a chart in literature generated using Fox's (1948) equation from where every time i had to read values and insert in the cell.
Can any one guide me that how can I find this Fox's equation or any other alternate way to get this factor without reading chart for every time.

Thanking in anticipation.

[ynopum]

I haven't heard about Fox's theory, but in the East European school (incl. Russian) it is was used similar idea of so called "effective compressive depth". At least I think it is similar because of the name. I suspect that it is not available easily in English language. So, sorry about not giving theoretical help.

Nevertheless, I can help you in the automation of the chart reading. There are two options depending on the type of the chart and the way it looks like:
1. If the chart can be found in table form you can input the table(s) in MS-Excel, and there you can use the "match" function to search the cells where the values to be read are placed. Then you can use linear interpolation to find the "reading" for the exact argument.
2. If the function is given only in graphical way (a diagram), then you have two options:
2.1 Make several readings that describe the diagram properly, and represent these in table form, then use the first option above ( 1.)
2.2 Make several readings that describe the diagram properly, and if the diagram is smooth you can use approximation function that fits the read data with minimum error. Using Excel you have options to do so using polynomials, log- and exp- regression. Then you can use this function directly as formula in any cell.

If your case is only a chart, you can "shot" it and put here to see which is the easiest (and most accurate) way to be entered in MS-Excel.

[avscorreia]

Just another hint: you can use the free software Engauge Digitizer to digitize your graph.
Just goggle it and you'll find it at sourcefourge.net.

[uetian19]

Agreed
here are the few snaps of charts developed by using the Fox's Equation.
1- Taken from book "Shallow Foundation , Bearing capacity and Settlement" by Baraja M Das


2- Taken from book "Soil mechanics and Foundation Engg " by V.N.S Murthy..


These two images apparently seem to be different but they are the same as references are the same. Fox's (1948) equation.

Similar kind of prob is encountered with another graph..
Taken from book "Shallow Foundation , Bearing capacity and Settlement" by Baraja M Das for the calculation of influence factor

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