The completion of the first phase of shenzhen metro line 8 will lay the foundation for its completion in 2020

On August 9, the left tunnel of shenzhen metro line 8 from shenwai station to yantian station was completed, marking the completion of the first phase of subway line 8.

According to the report, the completion of the left tunnel from shenwai station to yantian station marks the completion of the first phase of subway line 8, which creates a good condition for the next phase of track laying and lays a solid foundation for the completion of the first phase of subway line 8 in 2020 as planned.

Shi chun, who is in charge of the shield construction project between shenwai station and yantian station, told the reporter that the geological structure between shenwai station and yantian station is too complicated, including soil layer, rock, weathered rock, granite and so on. This kind of "soft upper and hard lower" stratum structure makes it very difficult to advance the shield machine. In particular, a section of granite layer with a length of more than 670 meters has a very high hardness and a compressive strength of 160 mpa. "Such a big stone, hardness for this good at excavating sand structure type of shield machine, it is very tough, shield, such as geology, blasting expert discussion and borehole blasting experiment many times, finally ground deep hole pre-splitting blasting scheme for implementation, drilling from the ground first, and then into the explosives, blowing the hard rock loose some, and then for shield tunneling. One ring of the shield is 1.5 meters. Under normal soil conditions, the shield machine can push the ring in three to five hours, but on this hard granite area, the most difficult ring took 29 hours!"

According to the introduction, because the stone ballastless is too hard, shield machine screw machine can not bring out, will often be blocked, which requires workers to open the cover plate, dredge. In addition, the hard granite wears away the blades of the shield tunneling machine very much. When digging into this interval of nearly 1000 meters, the cutting tools of the shield tunneling machine are changed for 40 times, while the general soil layer structure can be changed for two or three times. Shield machine tool change, open to prevent blade and strata caused by the contact area of rock and groundwater seepage risk, but also to a certain pressure, shield machine in the blade of the workers have to in the pressurized environment, will have been worn blades in down, and changing the new blade, shield machine 46, the blade and each set of blades is a few hundred catties, all in one time, difficulty cans be imagined.

Subway tunnel construction is underground, but also take into account the safety of the ground. From shenwai station to yantian station, you pass under yantian sancun, a village of farmers built around the 1980s. In order to ensure the security of people's personal and home, the project department for many times and area, streets, communities, the villagers to coordinate, to shield tunnel construction influence scope of villagers building empty building placement, personnel arrangement to the hotel to live, will live at the same time, the villagers houses may be affected by the construction scope, consolidation grouting reinforcement, set up automatic dynamic monitoring network, prevent houses subsidence and other safety accidents. "In yantian SAN village, the project department strengthened a total of 135 houses. In order to ensure the safety of villagers, the shield tunneling machine stopped underground for two months. Only after all the safety measures were in place, did the tunneling begin. During the shield tunneling, surveyors are on site all day long, and even meals are delivered to the site."