The Weeping Tunnel at Pattipola

Continued from February 8 page 13

"Don’t be slovenly you fellow. It’s time we finished this work and called it a day. If you had drilled the hole on the crown, put half a charge and blast it."

Girigoris did exactly as he was ordered and they all ran for safety having ignited the charge. Two flagmen were stationed on either side of the tunnel with orders to stop any on coming traffic. Weerakoon was quick to realize that the noise of the blast a few minutes later was unusually loud. After the initial noise subsided and he felt that it was safe enough to get near to the scene of the blast, they rushed to the site. With the help of lamps they examined the top of the tunnel face which now seemed hollow. That was not a result they wished to see.

This was how Weerakoon had succeeded in acquiring his nickname ‘Half Charge Weerakoon’! It was a blast gone wrong. The charge apparently was too much. A portion of the crown of the tunnel beyond what was necessary had come off. Through the cavity that had been created, they saw lumps of soft sandstone falling continuously. Weerakoon was now getting panicky. There was much heavier seepage of water through the opening now than before the repair. This rush of water was causing more soil to erode. The cavity was expanding continuously ‘purging’ virgin soil!

Weerakoon had to do some damage control, quickly. His mental faculties however seemed to be getting cramped and he was staring hopelessly into the darkness of the expanding cavity while the seeping water was washing away more and more of the soil. He decided on the simplest of remedies that came to mind which was to remove the debris as it fell. He informed the District Engineer of the problem at hand and his solution. He also cautioned him of the long delay to restoration of track that would result from what had happened.

The remedy he tried out was on the premise that some part of the overburden right above the cavity would be hard enough not to yield. For a couple of days and nights they continued removing the debris. They improvised some long handle mamoties when it became necessary to work from a safe distance away from the cavity and avoid injury due to the falling debris. Realizing that they couldn’t keep pace with the rate of falling debris, as they also had to carry it out of the tunnel before disposing of it, they doubled and redoubled the gang strength. But they found that this stupendous task was beyond them; earth was falling at a rate faster than it could be removed. In desperation they gave up and informed the District Engineer accordingly.

Next morning orders were received that they should reverse the process. "What kind of logic is that?" thought Weerakoon. In effect that meant they had no work to do but allow the debris to fall. He didn’t mind that after days of agony and hard work. Earth that fell through the cavity from above was allowed to accumulate and as a means of expediting the work, he was also asked to bring, in addition, more earth from outside so as to cover up the entire tunnel profile if the need arose. By the 13th day the filling was completed and the tunnel passage blocked completely as desired. The purge of ‘porridge’ was apparently over.

The next stage of the operation was driving thick wooden planks through the filling, grazing the tunnel wall, with the front ends of the planks cut to a sharp V shape in order to facilitate driving them through the soil. The next step was to support the ends of the planks on each side of the filling on cribs bent to the profile of the inside face of the tunnel using old rails. The old rail cribs were secured at their lower ends in concrete pads. All these components were so arranged that they stood clear of the loading gauge so that vehicles could safely travel without infringing on them. It would then be possible to safely remove the fallen soil underneath the planks and clear the tunnel for traffic.

Weerakoon was now beginning to understand the logic of the entire operation. Two gangs commenced this work simultaneously from the two sides of the filling and when this work commenced the only way men from one side of the tunnel could communicate with those on the other side of the filling - a distance of just eleven feet - was by telephone. What was earlier expected to be a permanent repair for an existing defect turned out to be a salvage operation that resulted in a temporary repair as bad as or worse than what existed earlier.

Employing a total of three hundred men, eight officers two engineers and equipment to match, it took 17 more days to complete the work of driving the planks and supporting them on the rail cribs. Every employee worked relentlessly. It was one mass of men and materials working with all their might to see an end to this seemingly endless task. By February 11 they did see an end to it. The earth filling was completely cleared and the passage through the tunnel was restored. Why a routine repair of a mere one and a half weeks for Weerakoon’s tunnel gang should have taken this dramatic turn on the very first day work began only Girigoris would have known

Extremely unfavourable weather conditions, the immense magnitude of the task and the heavy leakage of water on to the track offered the staff many a hazard. During the initial stages of the repair, when the passage through the tunnel got blocked by the falling debris, water that usually flowed along the side drains on either side of the track through the tunnel began impounding. Men were working knee deep in this water despite the biting cold during that time of the year in Pattipola and this went on until the water was subsequently diverted elsewhere

It took over twenty years, to carry out permanent restoration work on the tunnel. Due to the dynamic conditions caused by rail traffic as well as ground conditions that prevailed in and around the tunnel causing disturbances to the tunnel structure, detailed investigations had to be carried out to determine such causes and arrest them. Accordingly, after consulting the department of Geological Survey, some bore holes intercepting the cavity were drilled through which grout was pumped. This arrangement ensured that seepage towards the affected area was minimized. It was nearly thirty years after the abortive repair that permanent restoration work could be done. Only then was it possible that the temporary arrangement such as temporary crib supports and timber planks put in place in 1951 could be removed.

The permanent repair consisted of a reinforced concrete lining covering the entire tunnel profile over the affected area. This was pre-cast in sections in the factory, transported to site and erected in position so as to provide a permanent support to the area affected earlier. By then, Girigoris has left the service and with him the mysterious happenings have disappeared as well.

This breach has no parallel in the history of tunnels in the Sri Lanka Railways. This report is incomplete without reference to the hazard that the two engineers themselves faced during the restoration work. On the third day or thereabout when the crisis was at its peak, they had walked up to the top of the tunnel hoping to cross over to the other side of the breach. They soon got lost in the wilderness. After many hours they had found themselves near the mouth of another tunnel, miles away and beyond the Ohiya railway station. On hearing of this later, Girigoirs had told them how the lady in his tale had during her heyday been riding a horse every morning along a bridle path on the top of the hill right above the tunnel and that they must surely have been taken for a ride by her spirit.

(The writer retired as General Manager of Railways)

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