First extra-high voltage AC looped network in the world
Another super project will be borne beneath the Yangtze River bed with a successful start of the “Excellence” shield tunneling machine for a Sutong GIL overall pipe gallery project on June 28, 2017. This great tunneling machine was designed by CRCC China Railway SIYUAN Survey & Design Group and contracted to build by CRCC No. 14 Railway Bureau.
The Excellence, a four-storey Iron Dragon as weight as 2,400 tons, was made in Guangzhou on March 24 of this year, and there are the following five great highlights:
Highlight I: Going through the Yangtze River bed for the first time in the world
It is first in the world that a shield tunneling machine went through the Yangtze River bed to construct a GIL electrical pipe gallery which is an EHV transmission and transformation project through the Yangtze River.
Highlight II: World’s greatest in voltage classes and transmission capacity
This tunnel is an extra long-distance GIL (gas insulated transmission line) innovation project with a highest voltage class, a biggest transmission capacity and the most advanced technological level in the world. The GIL laid within the tunnel can transmit 1000kV AC extra-high voltage (EHV).
Highlight III: World’s greatest in innovation and creation of the TBM technology integration
The Excellence, 140 meter long and weighing 2404 tons, has a 200 ton cutter masterdrive and a 262-ton cutter with an installed power of 3000KW. The cutter masterdrive bearings are sealed by multiple external and internal seals, lip seal and automatic backpressure regulating system to handle the maximum pressure. The machine’s ventral brush can be changed within tunnel, and the maximum working pressure for human cabin and material tank can reach 10 barometric pressures so as to ensure the safety of operators and the machine.
Highlight IV: Most difficult in construction across the Yangtze River
The tunnel beneath riverbed is excavated at a diameter of 12.07 meters, with a largest cross section. Its deepest point is up to 78 meters, and the biggest water-earth pressure comes to 9.5 bars. This project is involved in complicated strata in the complex hydrogeological conditions. The tunnel goes through a long close sand layer with a high content of quartz and a long stratum with harmful gas. It is a deepest cross-river tunnel currently with a highest water and soil pressures. The builders face more severe challenges in construction.
Highlight V: Strongest in teamwork in the history of shield tunneling construction
More than 20 experts and senior engineers such as Academicians Qian Qihu and Chen Weijiang as well as Prof. He Chuan joined the proposal discussion and feasibility studies successively.
The Sutong GIL integrated pipe gallery is a strategic passage and control project for the loop-closing operation of Eastern China EHV AC looped network. After completion, the loop-closing operation can be available for the EHV AC dual-loop networks between Huainan, Nanjing and Shanghai in Eastern China. This will ensure Eastern China can receive a more electricity capacity of 3500KW from other regions, satisfying the need of electricity of economic and social development of the region. Moreover, it can save 200 million tons of coal for electricity generation every year, and reduce the emissions of sulfur dioxide of 960,000 tons, of nitric oxide of 530,000 tons and of dust of 110,000 tons. All this will be of significance for a harmonious development of economy and society with environment.
TBM cross-section 3D effect sketch
Sutong GIL gallery section effect sketch