The collapse was caused by excavation works close to the building. The excavation works created two problems that led to the collapse, the reduction of the load distribution of the soil pressure bulb and the vibrations to the soil caused by driving piles, which were constructed to support and protect a tunnel and a staircase adjacent to the excavation
Another factor that caused the collapse of the Minard Hall was the vibrations due to driving piles adjacent to the excavation works. The soil beneath Minard was already composed of weak clays. The vibrations caused by the driving machines weakened the clays and their already weak strength to support the superstructure. Moreover, the vibrations can lead clays to easily move laterally to the excavated hole.
It was the combined effect of the reduction of the load distribution and bearing pressure and the vibration of soil that caused the collapse.
- The construction and excavation was ceased, in order to prevent additional collapse.
- The already collapsed portion and its adjacent structures that were affected were demolished.
- A shoring system was designed and constructed.
- Additional testing, analysis, ground investigations of adequate bearing stratum, and stabilization of the structure and the foundation were put into effect for the next four to five months. Loose sand and fill were removed and replaced with compacted engineered fill.
- Simultaneous work at the west side of the building and other site improvements were also taking place with the remediation works at the north side.
- The north collapsed portion was redesigned.
- The mechanical equipment room, which was supposed to be located at the basement, was removed and relocated to upper floors.
- Before design, implement ground and geotechnical investigation, land survey, and soil testing and analysis.
- The load distribution of the proposed works should be taken into consideration in the design stage.
- The effects caused by the noise and vibration of driving equipment should be considered.
- Appropriate construction methods should be considered.
- Soil retaining methods near critical areas of excavation should be used.