Handling Failures in Civil Engineering Projects: A Brief Case Study
Learnings from a site visit to the under-construction flyover and underpass at the Atul Kataria Chowk, Gurugram, Haryana, India.
This week, I visited one of the sites where construction of a ROB(Road Over-Bridge) is currently underway. The purpose of the visit was to inspect damages that had incurred whilst transporting a girder(beam) to its position on the columns(pillars) meant to support the flyover.
The Structure in Question
The flyover and underpass at the Atul Kataria Chowk are being constructed in hopes of decongesting this area of Gurugram which connects the Huda City Centre Metro Station to multiple sectors in Gurugram, Gurugram Railway Station, Daulatabad and further sectors on the Dwarka Expressway. Naturally, this stretch witnesses a huge amount of traffic. Tenders for this project were hence released by the PWD(Public Works Department) back in 2018 after getting a nod from the state government.
Till date, the columns for the flyover have been erected, and girders are being lifted onto their positions gradually, to be followed by laying of the flyover deck(top flat surface supporting traffic) on them.
Each girder has an approximately I-shaped cross-section that has been pre-stressed with the help of cables to leave them in a compressed state, providing enhanced strength.
For the purpose of developing a bond between the prestressing cables and the surrounding structural concrete, and additionally provide protection to the steel cables from corrosion, a mix of cement slurry has been injected into channels in the girders, through a process known as Grouting.
As we were told by the on-site engineer, whilst lifting one of the girders using heavy machinery, the girder buckled and twisted leading to deformation and generation of cracks throughout its length, making it unfit and terribly unsafe to be used in the flyover. Since prestressed cables had been used to maintain a compressed state of the concrete, these cracks were not as evident as they might have been otherwise and could easily be overlooked by a layman. Thus, to get a better assessment of the damages, the cracks were marked with white chalk.
Additionally, it was noticed that the base of the girder, originally meant to be in compression, had been subjected to tensile stress during buckling. This had resulted in both cracks and a permanently deformed arch-like shape. The girder had now twisted in a way so that it was impossible to have a clear perception of its longitudinal extent when seen in perspective (front view).
Cause of Failure
During the lifting process, the girder tilted in a direction where it did not have sufficient inertia to bear its own weight, which resulted in the development of cracks. This tilting was due to the lack of a stable, even casting base on the bed where the girder had been laid.
Fortunately, no lives were lost in this mishap. However, it did result in the loss of precious labour and time of at least 2 months, along with an estimated monetary loss of Rs 5–7 lakhs, which certainly sets the project back by a few months of work. Apart from the additional cost of the project this delay brings with itself, it also invites inconvenience of the huge amount of traffic that flows throw this section daily, due to the space the project takes upon the ground.
Had these cracks gone unnoticed or this section been placed onto its position on the flyover regardless, it could have led to much more dangerous situations involving bursting/collapse of the concrete girder and invited a heavy penalty for the contractor owing to negligence. Hence, the girder will now be discarded and replaced by the contractor and his team.
Conclusion: My Two Cents
Clearly, the simplest of tasks on-site in civil engineering projects require a lot of precision, in the absence of which, heavy losses(whether in terms of resources or lives) can be incurred. That being said, it would be interesting to think of a future where conventional civil engineering equipment is replaced by intelligent machines that can manage such tasks seamlessly and adapt to situations on-site, maybe even serve as decision support systems.