Use least invasive techniques to build roads in state: Kapila

The Tribune series on what needs to be done to rebuild the state
Tribune News Service

Dehradun, August 5

KK Kapila, chairman of the International Road Federation (IRF), a Geneva-based safety organization, believes that it is a real challenging and daunting task to align and build roads on the fragile terrain of the young and still active Himalayas in Uttarakhand in the aftermath of the natural disaster. There is a need to use non-destructive and least invasive techniques to build roads in the state. He is also Co-Chairman of the infrastructure committee of FICCI.

“A quick stopgap approach in rebuilding the infrastructure cannot be a solution. Rather reengineering and building the road infrastructure in a step-by-step method using non-destructive and least invasive techniques is the need of the hour. We have to sieve out the best of our past experiences and adopt the state-of-the-art non-conventional techniques for sustainability and propose the appropriate solutions,” he said.

Kapila added as a first step a detailed subsurface investigation of the affected areas should be carried out. “Non-Destructive Testing (NDT) is an integral and important aspect of subsurface investigations. Although there is a significant school of thought that does not believe in the efficacy of such investigations in the Indian conditions. This is a myth. The NDT actually reduces the cost and time of subsurface characterisation through proper combination of validation with invasive techniques. The best tools in the NDT category for hill roads will be seismic, Electrical Resistivity (ER) and Ground Penetrating Radar (GPR). The GPR is very useful in subsoil investigations and offers concrete characterisation of different layers, besides pavement structure integrity,” he opined.

Kapila said it was imperative that the road agencies do not undermine the efficacy of good, extensive and thorough geotechnical investigations in the hill terrain before hitting the design board on any new alignment or widening of existing roads through newer techniques.
He added while planning and designing the rehabilitation of the affected roads, it needs to be remembered that the outer and lesser Himalayas comprised of unstable strata owing to the young folded mountains and these sections of the Himalayas comprised of very weak to weakly cemented sedimentary rocks that lacked inherent strength. 

“Consequently, cutting of slopes in such ranges and strata, regardless of extreme precautions and environment-friendly techniques that are least invasive, does not guarantee adequate protection to the road foundation or the slopes,” he added. Kapial said blasting, which is used as the fastest and an economical method of road construction, should be avoided.

“In the recent projects for four-laning and six-laning of roads undertaken by the National Highway Authority of India (NHAI), the hill cutting and widening works had been done using a combination of excavators, road headers and breakers. These minimise the extent of damage to the hill slopes and strata and in combination with remedial measures such as shotcreting with wire mesh and rock bolting, use of rock fall nets, concrete cladding, and most important proper diversion of surface runoff through catch drains, chutes and toe drains on berms have provided stability to the slopes,” he said.

He said tunnelling in hill terrain with geologically very weak strata had been successfully tackled through the use of rock cutters, road headers and a combination of drilling and mucking. “The cutting profile is near perfect. The strata are not significantly disturbed and the installation of tunnel support systems have been near perfect. Despite being a slow process and capital intensive, it brings in significant savings on the subsequent operation and maintenance costs once the roads are functional,” he said.

Kapila said ideally the best way to develop roads in hills was through the use of tunnels and connecting viaducts. This minimised disturbance to the existing hill slopes. The construction of linear structure foundations along hill slopes, especially alongside river valleys with perennial streams that become hyperactive during cloudbursts and very heavy precipitation in the catchment areas, which cause heavy damage to the toes of the breast walls and retaining walls of existing roads running along the slopes. “One of the best examples is the Kalka-Shimla Heritage Rail the alignment of which comprises 103 tunnels crossing such geologically weak strata. Despite being over 100 years’ old, this rail line had been closed on rare occasions indicating the robustness of the alignment in penetrating slopes in geologically competent formations and tunneling when such formations are unavailable. However, the economics somehow hinders the development of such costly but far more permanent solutions. Thus, it is time that we adopt alternative technologies for our structures,” he added.
Kapila said another area for adopting alternative technology was the use of emergency bridges like bailey bridges as were immediately required in Uttarakhand. He added modern emergency bridges were costlier but gave the advantage of two-lane traffic and allowing heavier loads that match permanent bridges for national highway requirements. “At about Rs 6 to Rs 7 lakh per metre, including transportation from overseas and construction, these bridges can carry heavier and wider single loads to allow for large construction machinery or equipment and take less space. It is a four-fold advantage at less than twice the cost of a bailey bridge and compares more favourably with a permanent bridge with the huge advantage of a quick launch. This cost will come down further with appropriate excise concessions considering its use in emergencies and lack of alternatives in the country. With local manufacturing in the long run, it will be even more cost effective. A farsighted policy in introducing such bridges is required. The time to take corrective measures post-Uttarakhand is now. It applies to most of our borders. Learning from experience and induction of new technology will pay rich dividends,” he said.

Emergency Bridges are more expensive than conventional bridges. A bailey bridge (single lane, Load Cl 30) for example costs about Rs 3.7 lakh per metre for a 50 metre span bridge. It is more expensive than a normal concrete bridge, which costs about Rs 5 lakh per metre for a two-way bridge built to the National Highway load specifications. The launching speed of a bailey bridge is the advantage i.e. 1-2 days, vis-a-vis 1-2 years for a permanent bridge depending on site conditions.

WHAT TO DO Blasting, which is used as the fastest and an economical method of road construction, should be avoided Re-engineering and building of roads step-by-step using non-destructive and least invasive techniques Use of tunnels and connecting viaducts to develop roads in hills A detailed subsurface investigation of affected areas