dumbpilebuck
Coastal
I was recently on a project and have some questions regarding the structural integrity of the work performed by the contractors personel (me).
The project was in the sierra nevada range building a six span flat span bridge. The Structure was designed to AASHTO 2007 LFRD standards. The Drilled Shaft Diameters were 36 " with 4000 psi concrete. Drilled shaft lengths as designed ranged from 45' to 63'.
1. The drilled shaft boring logs showed a 15 ' construction fill of cobbles and boulders.
2. The mid range of the shaft a peat material and extended approximately 20 feat lots of cave in using a polymer drilling fluid.
3. The pile were designed as end bearing and tip competent material was defined as 1900 psi weathered granite with a nine foot socket.
4. Three Pile per cap structure with at the cap 32 feet. H25 loading.
Problems encountered
1. Substantial Flowing water. Solution permanent casing 20 to 30 feet out of contractors pocket.
2. Inexperineced Inspection Staff- None Period end of story and this is who determined competent rock.
3. Inspectors would not determine that competent rock was hit and the socket started until a core barrel was required.
4. Pile Overran in lengths approximately 20 feet each and were socketed in granidiorite wist end bearing capacity of 16,600 psi.
5. The granidiorite is cross grained an when a core was drilled and tested it broke at 6600 psi.
6. Due to the extended lengths and substantial drilling time holes were open up to 7 days with polymer slurry not so successfull due to peat soils (high elevation 7000 psi.)
7. One shaft actually had a loss of concrete substantial enough that the hole was 10 yards short.
8. One drilled shaft showed a void in the crosshole sonic logging and three months later was non existant when cored.
Equipment Used
AF18 Drill Rig with crown pressure of 140 k per square foot.
Question:
What are the impacts to the foundations with the drilled shafts going so much deeper into the 16,600 psi rock.
1. Will there be issues with Pile Moment , shear and axial loading?
2. What about uplift due to the extended pile length into granite. The plugs pulled out are smooth like a babys bu.?
3. It is assumed that competent 2000 psi rock was hit at approximatly 30 feet which is consistant with the borings within ten feet or 40 foot deep we were in 4000 psi rock and advancing the drill with a rock auger 3 feet per hour, at fifty five feet we dropped down to two feet per hour an assumed 6500 psi, and approximately sixty two feet changed to core barrel and were in anywhere from 8k to 16 when tip was called. What concerns would you have regarding the structural integrity of the pile and structure?
Any help would be appreciated we are trying to determine whether we should hire a foresics engineer to evalute the shafts for our protection. What do you thing
Dumb Pile Buck
The project was in the sierra nevada range building a six span flat span bridge. The Structure was designed to AASHTO 2007 LFRD standards. The Drilled Shaft Diameters were 36 " with 4000 psi concrete. Drilled shaft lengths as designed ranged from 45' to 63'.
1. The drilled shaft boring logs showed a 15 ' construction fill of cobbles and boulders.
2. The mid range of the shaft a peat material and extended approximately 20 feat lots of cave in using a polymer drilling fluid.
3. The pile were designed as end bearing and tip competent material was defined as 1900 psi weathered granite with a nine foot socket.
4. Three Pile per cap structure with at the cap 32 feet. H25 loading.
Problems encountered
1. Substantial Flowing water. Solution permanent casing 20 to 30 feet out of contractors pocket.
2. Inexperineced Inspection Staff- None Period end of story and this is who determined competent rock.
3. Inspectors would not determine that competent rock was hit and the socket started until a core barrel was required.
4. Pile Overran in lengths approximately 20 feet each and were socketed in granidiorite wist end bearing capacity of 16,600 psi.
5. The granidiorite is cross grained an when a core was drilled and tested it broke at 6600 psi.
6. Due to the extended lengths and substantial drilling time holes were open up to 7 days with polymer slurry not so successfull due to peat soils (high elevation 7000 psi.)
7. One shaft actually had a loss of concrete substantial enough that the hole was 10 yards short.
8. One drilled shaft showed a void in the crosshole sonic logging and three months later was non existant when cored.
Equipment Used
AF18 Drill Rig with crown pressure of 140 k per square foot.
Question:
What are the impacts to the foundations with the drilled shafts going so much deeper into the 16,600 psi rock.
1. Will there be issues with Pile Moment , shear and axial loading?
2. What about uplift due to the extended pile length into granite. The plugs pulled out are smooth like a babys bu.?
3. It is assumed that competent 2000 psi rock was hit at approximatly 30 feet which is consistant with the borings within ten feet or 40 foot deep we were in 4000 psi rock and advancing the drill with a rock auger 3 feet per hour, at fifty five feet we dropped down to two feet per hour an assumed 6500 psi, and approximately sixty two feet changed to core barrel and were in anywhere from 8k to 16 when tip was called. What concerns would you have regarding the structural integrity of the pile and structure?
Any help would be appreciated we are trying to determine whether we should hire a foresics engineer to evalute the shafts for our protection. What do you thing
Dumb Pile Buck
