What caused big building crash?

What caused big building crash?

Tuesday night’s dramatic building collapse in the Majestic area again exposes rampant violation of building by-laws in Bengaluru.

An engineer involved in the project also believes a rising ground water table contributed to the weakening of the soil, and contributed to the crash.

BBMP Commissioner N Manjunatha Prasad, who visited the spot on Wednesday, issued a show-cause notice to Dharma Keshava Infra Pvt Ltd, the company building a shopping complex where Kapali theatre once stood. 

The BBMP put the plan sanction on hold, and told the company to pay compensation and also face legal action.

A senior officer of the town planning wing of the BBMP told Metrolife the company had dug deep to build four basements, a ground floor and five floors on a 50,000 sq foot plot.

“The plan was sanctioned in December 2018, but the company had not collected the commencement certificate. The engineer in charge had started the deep excavation and parallelly started building a retaining wall,” he says.

The wall was left incomplete for want of labourers.  Because of the rain, the soil came loose, and the neighbouring building collapsed, the official says.

The buildings that crashed housed, among other businesses, a guest house with 35 beds and a recreation club.

Cracks noticed

Owners of the two buildings that came crashing down, as onlookers filmed them on their phones, had informed the BBMP of cracks developing in their walls. “People living in the building were evacuated and an alert issued. This is why there was no casualty,” the top official says. Photos make it clear that even the buildings that collapsed were not constructed in accordance with BBMP by-laws. The offset rules, which specify how much space to leave between two buildings, were flouted, he says.

Water level rise

A senior engineer from the engineering firm involved in the design of the building coming up on the Kapali site blames a possible rise in the groundwater table for the collapse. “There was no history of the water table level in the area, but it appears that it has risen,” he says.

This suggests the area was at some point a lake, and the waters came back because of copious rains earlier this week.

Deflection monitor

A Gujarat firm is handling the design and construction of the retaining wall. “The wall didn’t have any major deflections but people had observed minor cracks as early as Sunday morning. Typically, in construction, cracks develop but failures are always related to deflections. We had been using sophisticated equipment to monitor the deflections and the movement in the wall since Monday,” he says.

Meanwhile, people in all surrounding buildings were evacuated. “We tried to arrest the widening gap by back-filling, on the retaining wall consultant’s advice, but that didn’t help. The building collapsed after the gap widened up to 300 mm,” he says.  He says deep excavation cannot be left open for long, especially in the monsoon. “Delay in construction of floor slabs that give additional support to the diaphragm wall could be one of the causes for the collapse,” he says.

He suspects shortage of labour, because of the pandemic, might have delayed wall construction.

Violations come in 
many forms  
Sridevi Changali, principal architect and co-founder of Masons Ink, says setback-rule violations put buildings at huge risk.
“Setback is the space meant to be left between the compound wall and the building. This is mostly not respected or is followed on the ground floor and not followed in subsequent floors,” says Sridevi.
Builders ignore curbs on basements to maximise rental square footage. “This in turn puts all surrounding buildings in danger, especially if they haven’t followed by-laws either, and creates a domino effect in terms of damage,” says Sridevi.
She also says the other violation is the building height. “What essentially happens if by-laws are not followed? Apart from the obvious threats to health and safety, the quality of light and ventilation is also affected,” she observes. Deep excavations, such as the one attempted on the Kapali site, can be extremely dangerous, especially for neighbouring properties. “The foundation of any building is resting on stable ground with a predetermined soil bearing capacity. What happens with an adjacent excavation is that the soil is weakened,” she says.
When exposed to the rains, portions of the soil slowly start to slip away, thus impacting the stability of the adjoining buildings. A retaining wall essentially arrests this erosion, she explains. She suspects the delay in building the retaining wall contributed to the collapse.  

Who is to blame?
Violations are rampant as municipal councillors and zonal assistant executive engineers dictate terms, and rental greed and corruption go together, a top BBMP official told Metrolife.

Not the first near Kapali
In 1983, a seven-storey building under construction, belonging to booksellers N Gangaram, collapsed near Kapali cinema. It resulted in the death of 123 people and left 120 injured. The government ordered a judicial enquiry and the owner and three contractors were arrested. An inquiry found they were found guilty of plan violations.

Area of water bodies
The Majestic was replete with ponds, lakes and stepped wells, according to Suresh Moona, city historian and columnist.
“There were at least 12 kalyanis in and around Majestic. There were small choultries around them and people used to bathe there. As the city grew, they were encroached, filled with mud and constructed upon,” says Moona.
Kalyanis are stepped wells attached to temples. Moona says people passing through the city would stay at the choultries, pray at the temples, and bathe in the kalyanis.
“People who build on water bodies must understand that the soil is not solid. This is not a sustainable option,” he cautions.