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Thursday, November 7, 2019

How avoidance of detailed ground study resulted in failure of road infrastructures

As usual, I always begin by thinking, whenever I see failure in road infrastructures; road construction in Bhutan has already past half a century after its inception in early 1960s.  Exactly, at this time, mule tracks and footways are mere history to track back. Roads replaced all those detour tracks for transportation that touches high mountains and deep valleys. Slope failures on those tracks were out of question since these don’t have one except than the natural slope. But, the road construction comes with designs that require cut and fill that develops another slope in addition to natural slope, which is called cut and fill slope. The failure mechanism of these slopes must be addressed and learned. Despite engaging into road construction and maintenance for decades, are we enough with the trend? We have many questions to ask and things to do. Let the custodian of road don’t bounce from one agency to another.

Department of Roads, in the 11th fifth year plan and in the beginning of current plan, Geog Connectivity roads were with the department. Planning and budgeting works were mandate for the department. Finally, those roads were handed over to Local Government. Inconsistency in the decision of springing the custodian has left those improved roads further deteriorated and damaged.

We are adequate with road coverage. Every nook and corner of the country is connected. We are enough with the length. Length of roads has out numbered the technology involves. Now, what we need is advancement of technologies with the change.
Bailey Bridge subsided under the catastrophic slope failure.
Construction techniques of the road, starting from formation cutting to pavement strengthening have improved with advancement and introduction of new machineries and methods. Environment friendly road construction technique was started in the late years of 9th fifth year plan and now the time has triggered and reminded to start preparation to integrate the construction of climate resilient road infrastructures.  

Indeed, monsoon has taught us good lessons. The change, we see through more destruction and damages in road infrastructures than before. We feel the change through roadblocks.

How it is possible to overcome the change, especially the climate change?  What are differences in failure we observe between then and now? Are those failures due to climate change or something else?

Pavement or the road fails because of failure of permanent structures – walls, drains, cross drainages and slope etc.  Bridges usually fails because of overloading and slope failure. Otherwise, bridge failure due to other reasons is least that we usually counteract immediately.

Let me explain one simple example- provision of both sides camber on pavement in any category of roads. Our Primary National Highways are wide enough to provide camber on both sides and so is likely with the Secondary National Highways. But, is it really possible on Dzongkhag and farm roads? And our standards say that the camber should be on both sides. The standard carriageway width is only 3.5 meters. From my personal experience, there is constructability issue. Even if there is no constructability issue like in aforementioned category of highways, providing camber on both sides is unnecessary considering the different nature of soil conditions on downhill slope. We must avoid infiltration of runoff from the pavement, prevent saturation of slope, and let fail the slope grossly.

And why our walls repeatedly fail on the same location?
Pavement failure due to excessive infiltration.
Likewise, are our standard design road drainages or cross drainages adequate? Or do we need to revise?

The evidence of aggravating damages year after year on road infrastructures and restoration works that cost us dearly, must be felt in every individual responsible and indeed must be felt on end user as well. Or else we wait for the catastrophe that is looming large before us.

Therefore, road infrastructures designed and constructed decades ago may not suffice the change now. We may need to revise the design criteria and focus more on slope stability study. Much more information and awareness on knowledge regarding slope engineering is indeed felt necessary on top of the training provided for construction quality in conjunction with more effective road asset management.

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