Techno Legal Aspects of Forensic Engineering
Interview: Mr. LV Sreerangaraju
As one of the leading techno-legal consultants, what in your opinion is forensic civil engineering? How far is it adopted in India?
Ans. There must be some evidence to understand the failure in a structure, its mechanism and the mode. If there is partial failure in a structure, it can be reconstructed, but if there is a total failure, it's not possible to make it survive. In case of a total failure, the only way out is to redo the entire structure after learning from mistakes committed.
'Failure Analysis' is a failure in India. Failures in India are rarely reported and subjected to failure analysis. For example, the Panshet Dam failure in Pune which happened somewhere in the early 1960s was an eye opener. The whole of Pune was submerged in water due to the failure of the dam. The Panshet Dam, near Pune in Maharashtra India, was under construction when the dam had failed. It was zoned at a height of 51 m and having an impervious central core outlet gates located in a trench of the left abutment and hoists were not fully installed when floods occurred at the site of construction.
The reservoir had a capacity of 2.70 million m3. Due to heavy rains there was a rapid rise of the reservoir water level and the new embankment could not adjust to the new loading condition. Water rose at the rate of 9 m per day initially, and due to incomplete rough outlet surface the flow through was unsteady which caused pressure surges. Cracks were formed along the edges of the right angles to the axis of the dam causing a subsidence of 9 m wide. Failure was neither due to insufficient spillway capacity nor due to foundation effect. It was attributed to inadequate provision of the outlet facility during emergency. This caused collapse of the structure above the outlets.
As a result of Panshet Dam failure, the Khadakwasala dam also failed. The Khadkawasla Dam, was constructed in 1879 as a masonry gravity dam, founded on hard rock. The failure of the dam occurred because of the breach that developed in Panshet Dam, upstream of the Khadkawasla reservoir. The upstream dam released a tremendous volume of water into the downstream reservoir at a time when the Khadkawasla reservoir was already full, with the gates discharging at near full capacity. This caused overtopping of the dam because inflow was much above the design flood. Vibration of the structure was reported, as the incoming flood was battering the dam. Failure occurred within four hours of the visiting flood waters. Incidents like these must be brought out on record. This is a forensic failure.
Also, another case in point is the Teton Dam in Idaho, USA, an earthen rock filled dam, which is a 93 metres high dam, designed by the US Bureau of Engineers USBR, one of the most well-known design agencies all over the world. The dam was designed as a zoned earth and gravel fill embankment, with a height above the bed rock of 126 m, and a 945 m long crest. The embankment material consisted of clayey silt, sand, and rock fragments taken from excavations and burrow areas of the river's canyon area. It had a compacted central core. Narrow trenches 21 m deep, excavated in rock and compacted with sandy silt and a deep grout curtain beneath a grout cap the central zone were the measures taken to control the foundation seepage.
The dam failed on June 5, 1976, releasing 308 million m3 of reservoir water. A flood at an estimated peak discharge in excess of 28,300 m3 per second had occurred. A breach 46 m wide at its bottom and 79 m deep had formed. The time of failure was recorded as four hours. The cause of failure was attributed to piping progressing at a rapid rate through the body of the embankment. The two panels that investigated into the causes of failures were unanimous in agreement that the violence and extent of failure completely removed all direct evidence of the details and sequence of failure. However, the main findings suggested that erosion on the underside of the core zone by excessive leakage through and over the grout curtain was the cause of destruction. Wet seams of very low density in the left abutment extended into the actual failure area and these caused local deficiencies in the compaction of the fill, and might have been the locus of the initial piping failure.
Unfortunately, no failure analysis has been made in our country in a real technical sense.
There is no licensing for engineering in our country so there is no one to prevent what is happening.
What happens in legal terms after the failure of a structure is noticed/ reported?
Ans. Failure can only be of two types. Firstly due to acts of God ie due to natural occurrences and secondly Engineering failures due to faulty design, construction and maintenance. In each one of these you have several components. It may be structural design, workmanship, construction, speed of construction, materials etc. This is followed by the maintenance of a structure. When a structure is built , its maintenance comes into being automatically. Whether we are going in for the predictive, preventive and or breakdown maintenance. Predictive maintenance is when you predict what's going to happen and it's when the forensic engineering comes into picture, the Residual Life Assessment Studies (RLA) are to be made and then we must go in for an appropriate maintenance. And once engineers predict a certain event, it may or may not be implemented. There is no legal binding on the decisions of an engineer; this is the crux of the issue.
Then the next thing is who is made the member of the committee to determine the analysis of a structure? Is he an independent, self-respected engineer, or is he a sycophant of the bureaucrat/politician. For example during the construction for the Commonwealth Games, there was a suspension footbridge while it was being concreted, it collapsed, but fortunately no one died. There was a design consultant, contractor and the project management consultant on board involved in the project. The failure occurred because one of the bar suspenders broke and it couldn't take the load. When one bar suspender is removed, the spans get doubled, and so it failed. Failure could be due to the design, quality issue or construction methodology. Then the government formed a committee of engineers which went into the whole issue. The committee came out saying that the design was not faulty, the quality control was also okay and there was nothing wrong with the contractor. But still the structure failed.
Forensic engineering plays an important part at that time and someone must be responsible for the failure of a structure. The reason they found out was the failure of the support in the CWG. The committee said that it was not because of any of the faults of the consultant, designer, project management or the contractor, but it was because of the bar suspenders which were supplied from a British firm which failed. But who designed it and accepted it? It is again a quality issue. So what is the use of this type of investigations/forensic engineering when we do not want to fix anyone responsible. We don't make a failure analysis at all in India.
One of the failures was the Hyatt Regency hotel in Kansas City, USA. The footbridge collapsed at two different levels killing 189 people. The failure analysis pinned down the designers and contractors and they were punished. The law prevailed.
It is unfortunate in India that we do not report failures and learn from our mistakes. There is a tremendous need for awareness among the fraternity and also there a need to enact accountability.