“I declare that the tunnel of Subway Line 9 by our Group will be joined up and the shield is coming!” with the order issued by Xu Jianyun, the chairman of board of BUCG, the cutter head of shield, Diamond, rushed out of the shaft of Subway Line 9 locating to the northeast of Naval Hospital. Subway Line 9 which is designed by Urban Engineering Design & Research Institute and constructed by BUCG achieves the cross between north and south. According to the statement of the experts in this field, the shield goes through special geological structure, boulder bed, rich water-bearing and large boulders and gravel bed⑦, which is 30 meters under the earth’s surface of Yuyuantan, marks that Beijing Subway construction skill makes the breakthrough in the field of lake bottom shield in special geological structure, the world-class difficult problem, and that many skills created by the construction technicians reach world-class level.
Cross-lake shield needs to go through boulder bed and gravel bed 30 meters underground. Most of these two layers consist of high strength, high quartz content large boulders, boulders with the diameter of more than 1.5 meters account for 20% of earth volume, gravels more than 50 centimeters account for 60% of excavated earth and the hardness of gravels reaches 187 megapascals, which is faced for the 1st time of the world in the construction of subway. In order to solve this problem, BUCG customized a high-power field on purpose for this section. This shield is different from the rest, for example, different kinds of cutters are on the plate. 159 cutters are installed on the plate with the power of 1200 kilowatt and the thrust of the field reaches 3780 ton per meter and the torque of it is 779 ton per meter so that this shield can not only walk in hard boulder bed but also dive in gravel bed in underground water like a driver.
It is understood that technicians of BUCG are innovative boldly in construction and create a lot of new technologies including the skill of setting cutters reasonably due to special geological layers, reforming muck of boulder and grave⑦ bed, shaking bondage, optimizing plate and cutters and so on. These more than 10 skills are initiated in China and provide technical support on going through Bayi Lake of Yuyuantan, from Jingmi water tunnel to Yongding River and shield construction of special section and contribute greatly to the cross of Subway Line 9 and the test run in the end of this year. (Translated by Qiao Nan)