@ BigHarvey, This wasn't a CFA rig. It was the conventional hydraulic straight rotary; IMT 180 and SoilMec SR60. the drilling was done with the help of bentonite slurry to stabilise the borehole.
@Oldestguy, I wouldn't say the placement of the rig. Actually the kelly guide of both rig were removed for some reason. In my opinion, the issues in alignment were due to this. The architect was surely worried with the results, because he lost some space of the basement.
@Hokie66, I agree with you. But I want to know how can we have better results and what precautions are to be taken when pouring concrete in slurry?
@MadMike @BigHarvey, The communication between the piles is also an issue. When we install the temporary casing, it has to have a diameter more than the pile diameter. So, we actually cannot get a tangent pile if we install a guide casing, and if we do, as in our case, the casing cuts the adjacent piles and damages the reinforcement as well if we lose the verticality. We proposed a secant pile system, but the structural engineer didn't agree.
If the soil do not have a minimum 15KPa cohesion, even if we case the piles, when we remove the casing, will the soil be able to provide the lateral support?
@LRJ, I haven't seen anyone use driven piles as earth retaining structures.