Article Source: http://www.bangkokpost.com/learning/easier-stuff/285493/sinkhole-probe-goes-hi-tech
Photos: Terry Fredrickson/Bangkokpost
City engineers have been attracting considerable attention in the Rama IV area as they use their high-tech gadgets to try to find what caused Sunday's large sinkhole.
Above ground they were seen yesterday wheeling a bulky ground penetrating radar (GPR) system down the middle of the road between Lumpini Tower and the Thai-Belgium Bridge.
Their underground work has been more productive, however. Using a robot equipped with a CCTV camera to inspect a four-decade-old tunnel which runs under the damaged area, engineers have found a small hole which might be related to the subsidence.
Adisak Khantee, deputy director of the Bangkok Metropolitan Authority’s Department of Drainage and Sewerage said the hole, which is about 5-8cm in diameter, allowed water to flow into the tunnel.
The hole was in the upper part of the tunnel and water flowing into it was fairly clean with no soil or sand mixed with it, said Mr Adisak.
It was unusual for a hole to appear in the upper part a drainage tunnel, he noted.
The BMA suspects the hole could have been caused accidentally during road work.
Department chief Sanya Cheenimit said he could not determine whether the hole was the cause of the sinkhole which appeared on Sunday. He added that he would report the leak to BMA executives.
Deputy Bangkok Governor Teerachon Manomaiphiboon, who supervises the BMA's public works, said the entire length of Rama IV Road, except where the sinkhole occurred, has been laid with reinforced concrete.
He has ordered the Public Works Department and the Pathumwan district office to check on contractors who have been hired recently to carry out work near the sinkhole's location. The two agencies would then check whether any repair work was up to standard or not.
If the work is found to be substandard, the firm would be put on a BMA blacklist, he said.