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[sspawar]

Dear Sefians,

During conventional DMC and chisel bailer type boring of 450 diameter in sandy strata, some portion 3 to 4 meter in depth below 3m from ground encountered with river sand stone (boulders) of size 6" to 24" , which were actually filled for bank protection in past days 20-25 years back.
I am sending a pdf picture to understand.
now situation is that 30 % piling of total 30 m depth with 10 meter liner has been completed in the area of 80 by 25 meter . From bank side of the river 16 meter wide area remained to pile.
It cant be drilled by chisel bailer. chisel is being bent. welding of pipes etc. are being weaken.
Strata is submerged type loose sandy. water level of river is 3m down from GL.
Have anybody faced such practical issue.
kindly share your experience and the way to get the piling completed.
contractor is showing disinterest in diamond cutting tools and arguing that stone will shift and whole strata will sink down. no chance of stability. Proposing to excavate the whole area for 5m depth (till the boulder found), and back fill by sand after removing.  Is this idea technically a right decision.
Regards