Skin friction for rock socket in Manhattan Schist
Skin friction for rock socket in Manhattan Schist
(OP)
We are designing a retaining wall for support of excavations in Manhattan. the wall will consist of soldier piles with rakers and wood lagging. The bedrock is very shallow, so the soldier piles are being socketed a few feet into the rock. Due to the steep angle of the rakers, there is a large uplift force on the soldier piles. We are discussing the use of the skin friction on the surface of the rock socket in order to resist the uplift forces on the soldier piles.
Do any of you have experience with this? Are there any publications which discuss the allowable skin friction for drilled piles in bedrock?
I found one reference online which referenced an "allowable skin friction on rock socket" value of 12.5tsf (~170psi). Unfortunately, it was only a scanned page from a book with no information on the book, authors, references, etc., so I am hesitant to rely on that value.
Do any of you have experience with this? Are there any publications which discuss the allowable skin friction for drilled piles in bedrock?
I found one reference online which referenced an "allowable skin friction on rock socket" value of 12.5tsf (~170psi). Unfortunately, it was only a scanned page from a book with no information on the book, authors, references, etc., so I am hesitant to rely on that value.





RE: Skin friction for rock socket in Manhattan Schist
www.PeirceEngineering.com
RE: Skin friction for rock socket in Manhattan Schist
RE: Skin friction for rock socket in Manhattan Schist
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Skin friction for rock socket in Manhattan Schist
www.PeirceEngineering.com
RE: Skin friction for rock socket in Manhattan Schist
www.PeirceEngineering.com
RE: Skin friction for rock socket in Manhattan Schist
This is an overturning issue. Globally, the system is not stable unless there is a vertical (downward) force at the soldier pile. Sum the moments at the bottom of the raker and you will see.
Also, the vertical component of the soldier pile force must be equal and opposite to the vertical component of the raker reaction. The raker is in compression, therefore the soldier pile is in tension.
RE: Skin friction for rock socket in Manhattan Schist
For hard Manhattan schist, you could have an ultimate bond of concrete to rock of several hundred psi. With a value that high and with a rock socket big enough to accomodate a soldier beam, I would have next to no concern about any upward force on the soldier beams.
www.PeirceEngineering.com
RE: Skin friction for rock socket in Manhattan Schist
You concern about uplift I agree with. Make sure your raker connection to the soldier beam is welded plate. Your condition is similar to a one sided concrete pour for a wall with no ties. With inclined braces the brace will move upwards. What is your height and soldier spacing? Is the rock solid?