Dip slopes and anchors suspected in freeway landslide

Experts suspected the geological phenomenon of the dip slope was responsible for the unexpected landslides on the No.3 Freeway near Keelung.
Transportation Minister Mao Chi-kuo first brought up the topic during a visit to the disaster site Sunday evening. Initially, observers were unable to explain why landslides had occurred in the absence of an earthquake or heavy rain.
The hill next to the freeway had a dip slope leaning toward the road. The other side of such formations is steep and irregular, while the dip slope side tilts downward, making it easier for rocks to slide down, experts said.
National Taiwan University geology professor Liao Juei-tang also said the anchoring holding up the hill had rusted and loosened, becoming unable to stop the rocks from sliding down to cover the road.
The anchors or steel reinforcers were also identified as the possible source of the problem by government officials, including Lin Chao-chung, the director of the Central Geological Survey under the Ministry of Economic Affairs.
Faulty construction or wear on the anchors in the restraining walls might have contributed to the failure to prevent the rocks from covering the freeway, he told reporters.
Another theory looked for problems with the presence of the Hsinshan Dam just 1 kilometer away, but experts thought the water had no way of influencing the roadside hill.
The Ministry of Transportation said it was investigating the number of locations showing similar geological characteristics to the site of the landslide. Mao estimated the number of dip slopes next to major roads across Taiwan at about 20.