CHENGDU Dec. 19 (NBD) -- Chengdu "Zhonghuan Road", a route encircling this city amid the Second Ring Road and the Third Ring Road, is undergoing the renovation work to have its sidewalk transformed into "sponge-like". 

The first renovated section of Zhonghuan Road was unveiled to public in June. Different to traditional pavements, no joint filling was made among ground tiles with cracks trumpet-shaped. The water sink immediately along the cracks and no ponding is found on the ground, in simulation to a downpour scene. 

Five layers of different materials in the underground structure have made this "sponge-like" sidewalk possible. Gravel, porous geotextile, permeable concrete and graded crushed stones and other materials are orderly placed underground so that the rainfall permeates down the surface instantly. 

"Compared with ordinary roads, water permeation of this structure has been increased by 20% to 30%. The gap deliberately designed between tiles and materials beneath them effectively help water to sink down," said a person in charge of the project from Chengdu Jiangong. 

Estimated to be completed by the end of 2017, the road renovation project for Chengdu Metro Line 7 covers the whole Zhonghuan Road of 42 Kilometers. "Construction of the 42-kilometer urban sidewalk is integrated with the philosophy of 'sponge city', and this is no common across China," introduced by an official of Chengdu Urban and Rural Construction Commission.