I was called to investigate a failure of a barrette foundation for the stiffenning core of a high-rise building. The soil is sandy, and the foundation is rectangular, 25 m deep with an internal dimension of 2.5x6.2 m . The wall thickness is 0.8 m and the trence filled with bentonite slurry. The drawing showed the job should be done in two stages, each being U shaped with internal dimensions of 2.5X3.1 m. Immediately after lowering the cage into the stage one hole, everything collapsed, with the cage impossible to pull out. From your experience, folks: Did this setup ever stand a chance?