Need some advise regarding sheet pile design

[fargofarmer]

Hi friends,

I am working on a sheet pile design project. The height of the sheet pile is 2 to 3 feet. Approximately 11 feet high, 1.5 to 1 reinforced slope is planned for construction behind the sheet pile. The contractor wanted to drive sheet piles in order to minimize the encroachment of buffer zone. my question is, do I need to consider the weight of entire 11 feet high fill material as surcharge for pile design? Or, becuase the sheet pile is only 2 to 3 feet, is it OK if I consider the surcharge load upto 4 t 6 feet behind the sheet pile? If hard/rock encounters shallow depth (say 4 or 5 feet below dredge line), is it ok to terminate the driving sheet pile at that elavation? I will really appreciate if somebody can adivse me on this.

 

[DRC1]

You need to consider the effect of the slope. Although you can compute the effect of the surcharge above the top of the sheet, a simpler way is to use modifed active and or passive coefficents for the ground slope. These can be found in a table, or if the geometry is not simple, can be computed by a Cullman's Diagram.You need to establish a certian toe elevation for a cantilevered sheet. If you can not get that you will need to brace or tie back the sheet.

As a VERY rough apoproximation, if you say half the height of the slope would be equivelent to level backfill, your sheeting ht is 2.5=5.5=8 ft. A 4-5 foot toe would require very dense or stiff materials. For medium dense or medium stiff clays, You may need more toe. However, you should run your own numbers.

 

[fargofarmer]

Thank you DRC1. I considered the loading in the way you explained. I got 12 to 14 feet of pile penetration. the reason for that is the N values varies from 2 to 5 at many locations. The hard or dense material was enountered at approximately 6 to 18 feet below the dredge line. If they cannot penetrate through the hard materail, can they stop driving the anchor further. I heard about socketing the pile into the hard material once. I do not have details how it works. Could you please let me know if you have any information on this.

Thanks again for your response.