Continuous downpour damages Retaining wall

19 July 2019

Date of Occurrence:- 4th July 2018

Due to heavy continuous down pour for the past few weeks, the discharge volume of rain water increased at large and the continuous flow through the old outlet drain at u-turn near Dzongdag's resident was damaged. The deep scouring of the old drainage had attributed in further scourging the foundation of adjoining retaining wall which eventually pulled the lining walls along the road below. If the down pour continuous for the whole monsoon duration it might damage the remaining walls. So in order to prevent further damages immediate measures need to be put in place.

The damaged wall was not a part of initial contract. It was proposed later to provide an additional support to counteract the centrifugal force at U-turn since there was an indication of road failure at the location. Actually there was a requirement of constructing heavy retaining structure below the u-turn, however due to very limited budget the Administration could not construct the heavy retaining wall, in place of the heavy retaining wall it was reinforced by masonry with toe stepped wall.  There is also an indication of column failure below approach road to Dzongdag’s resident. It was also shared that the column was hit by one heavy trailor truck which made the column weak.

During the last FY 2017-2018, the town road from Rangjung junction to School junction was improved by widening the road along with the drainage system. With the proper drainages, the runoff discharge flows all through the old outlet at U-turn since the diversion of drain water at U-turn towards town is controlled. The rapid drop of water at outlet had spilled over the adjoining masonry wall base at left and the parking column footing at right which resulted in weakening the bearing capacity of both the foundations. The sliding of these foundations ultimately pulled off the adjoining walls and RCC footpath above.