geotechnical engineering 1

[BimalSujeewa]

Pls. advise how to decide on the depth of rock socketing. Is there any guidlines or data at site where we can decied the socketing depth.

 

[TDAA]

Are you looking to socket piers? are they providing lateral resist, or is the concrn for axial? Do you need to resist uplift?

 

[BimalSujeewa]

I am refering to cast in-situ bored piles. The soil report says that the rock condition below is fractured and wanted rock socketing at least up to one pile diameter depth. HOwever, due to the nature of the rock, enven at that depth rock seemed to be fractured. We are totoally relying on end bearing capacity of the pile.
So I need to know, is there any guide lines that are related to the penetration of the rock to the time. We are using chisels to socketing peurpose.
Bimal

 

[GeoPaveTraffic]

You need to talk to the geotechnical engineer that prepared the report. Only they can give you guidance as to how to proceed.

 

[SlideRuleEra]

Years ago I was involved in a electric power station project that relied solely on drilled-pier skin friction for support (no end bearing). This is how the required contact area was determined:

A few (about 6, as I recall) of small (18" diameter, or so) test drilled piers were installed with styrofoam placed at the bottom of drilled hole. The depth of the rock socket was carefully determined. A pair of reaction drilled piers were also installed adjacent to each test unit. Reinforced concrete was placed with small tubing embedded in the concrete all the way down to the styrofoam. After the conrete cured, chemicals were injected into the tubing to "dissolve" the styrofoam (groundwater pollution laws may not allow that these days). Oversized steel casing prevent contact with the overburden - all support came from rock socket skin friction.

Each test drill pier was loaded until it failed (slipped down). With the contact area known and the failure load known, the coefficent of friction was determined. We used this value, with an added safety factor, for the design of 2000 or so, 4 ft. diameter drilled piers for the project.

http://www.SlideRuleEra.net

 

[PEinc]

You could do an O-Cell test on a pre-production pile and check the side shear and end bearing capacities.

http://www.loadtest.com