EireChch
Geotechnical
- Jul 25, 2012
- 1,309
Gentlemen,
Interested to hear peoples opinion on the following project.
We are putting together a proposal for the project below. The development is to comprise a block of 14 apartments. We are going to be doing 2 cable percussion boreholes to 20m depth, with SPTs and lab testing. The geology maps indicate the surficial soils are clay, sand and gravel underlain by chalk bedrock. The site photos below look like chalk at the surface. I havent been to site yet to confirm.
As you can see an existing contig piled wall is in place, the developer wants to reuse the existing wall however we are a bit skeptical. We understand that it is approx 10 years old. We have no design information about the wall. Before we were approached someone had some integrity testing done on the wall. A copy of testing on some of the piles is below. I know a little but about PIT, more just the basics. I would appreciate if someone could shed some light on how to interpret the results and determine where the pile depth is. From the graphs below my take is that where the 'curved' line crosses the x axis is where the pile toe is. This would put the pile toe at approx 6m for the majority of piles, however, some graphs show a curved line crosses the x axis at 2-3m depth, which wouldnt make much sense for a contig pile wall to be that shallow? Or pile 12 for example, the curved line doesnt cross the x axis within the 12m long graph? How are we meant to determine the pile length from that graph.
The developer was also proposing the idea of a static load test or dynamic load test (CAPWAP) on the wall. I dont think that it will be possible to (or at least it will be very expensive) to do a static load test. You woudl have to construct some sort of footing over the full length of the wall etc. I dont think its practical. The pile tops are all over the place, access isnt great etc. Also, with the CAPWAP, the piles are so close that the signal must interfere with each other? As you can see i have a lot of questions. We have a pilling expert in one of our other offices but he wasnt in the last few weeks so i havent got a chance to speak to him. I am also going to call the PIT tester for a discussion but i wanted to open some discussions here to see what people think.
In the end, if we can prove the piles are deep enough and have sufficient capacity i think they can be reused. I would envisage cutting the piles down and exposing the rebar and constructing a strip footing above.
Interested to hear peoples opinion on the following project.
We are putting together a proposal for the project below. The development is to comprise a block of 14 apartments. We are going to be doing 2 cable percussion boreholes to 20m depth, with SPTs and lab testing. The geology maps indicate the surficial soils are clay, sand and gravel underlain by chalk bedrock. The site photos below look like chalk at the surface. I havent been to site yet to confirm.
As you can see an existing contig piled wall is in place, the developer wants to reuse the existing wall however we are a bit skeptical. We understand that it is approx 10 years old. We have no design information about the wall. Before we were approached someone had some integrity testing done on the wall. A copy of testing on some of the piles is below. I know a little but about PIT, more just the basics. I would appreciate if someone could shed some light on how to interpret the results and determine where the pile depth is. From the graphs below my take is that where the 'curved' line crosses the x axis is where the pile toe is. This would put the pile toe at approx 6m for the majority of piles, however, some graphs show a curved line crosses the x axis at 2-3m depth, which wouldnt make much sense for a contig pile wall to be that shallow? Or pile 12 for example, the curved line doesnt cross the x axis within the 12m long graph? How are we meant to determine the pile length from that graph.
The developer was also proposing the idea of a static load test or dynamic load test (CAPWAP) on the wall. I dont think that it will be possible to (or at least it will be very expensive) to do a static load test. You woudl have to construct some sort of footing over the full length of the wall etc. I dont think its practical. The pile tops are all over the place, access isnt great etc. Also, with the CAPWAP, the piles are so close that the signal must interfere with each other? As you can see i have a lot of questions. We have a pilling expert in one of our other offices but he wasnt in the last few weeks so i havent got a chance to speak to him. I am also going to call the PIT tester for a discussion but i wanted to open some discussions here to see what people think.
In the end, if we can prove the piles are deep enough and have sufficient capacity i think they can be reused. I would envisage cutting the piles down and exposing the rebar and constructing a strip footing above.
