Faulty design behind damage to Solan highway: Experts

Tribune News Service

Ambika Sharma

Solan, August 12

Faulty engineering has allegedly reduced the 39-km stretch of the Parwanoo-Solan section of the National Highway-5 to a risk zone with debris and boulders continually flowing down on to the road after every spell of rain.

Its four-laning was completed in June 2021 at a cost of Rs 748 crore, although some additional work, including the construction of viaduct bridges, was still underway.

The excavated slopes have been continuously eroding in the monsoon with several stretches of the road having been washed away at Chakki Mod, Datiyar, Sanwara, Jabli and Patta Mod, etc.

Dinesh Kumar, Assistant Geologist, Solan, said, “The cut and filling method was adopted to construct the highway, but the saturation of water led to a colossal damage.”

The absence of effective drainage led to the seepage of water into the excavated slopes. The weep holes in the retaining walls, constructed to drain out surface water, also added to the damage.

“Weep holes reduce the pressure of water on the retaining wall and add to the strength of the structure. These should be activated to allow proper seepage of surface water from the retaining walls,” he said.

Key factors like angle of repose, the maximum slope (measured in degrees from the horizontal) at which loose solid material will remain in place without sliding, failed to be considered. “Angle of repose should be taken into consideration while excavating a hill slope which continues to erode until it attains its original angle,” said Arun Sharma, former state geologist.

“At some places, deep cutting of hills should be undertaken by acquiring more land to ensure stability. Otherwise, the hill slopes comprising sedimentary and shale stones will continue to erode for the next several years,” he said.

These key aspects appear to have been overlooked. Even the concrete structures erected along the slopes at some places have failed to remain intact. Cases of reinforced cement concrete walls crumbling at places like Saproon in Solan have put a question mark on the quality of engineering.

“The Geological Survey of India is the nodal agency for landslide studies. It should be roped in for rectifying engineering blunders committed along this highway,” Sharma said.

Though National Highways Authority of India officials have attributed the colossal damage to torrential rain and flashfloods, glaring structural defects can’t be overlooked.

Parwanoo-Solan section of NH-5

• Four-laning of the 39-km stretch of the Parwanoo-Solan section of the NH-5 completed in June 2021 at a cost of Rs 748 crore
• The excavated slopes have been continuously eroding in the monsoon season with several stretches of the road having been washed away
• Experts point out several engineering faults that allegedly led to this situation

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