At the construction site of Dahongmen Station on Phase III of Beijing Subway Line 8, two large cranes raised their 60-meter-plus booms to lower a 40-ton "steel reinforcement cage" into the ground. It is reported that Dahongmen Station, a key interchange station on Phase III of Line 8, has entered full-scale construction, and the station will offer transfers to Line 10 in 2017.

A dozen or so meters to the north of Dahongmen Station on Line 8 lies the Liangshui River, and seepage from the river would adversely affect the station's deep foundation pit. In addition, during Beijing's rainy season the river rises rapidly, creating a risk of river water backflowing into the foundation pit. To block the seepage of river water and groundwater, the project adopted the diaphragm wall construction method, using trenching machinery to dig several seepage-proof trenches around the site, lowering giant "steel reinforcement cages" 6 meters wide and 43 meters high into the trenches, and then pouring concrete, which is equivalent to forming a continuous reinforced concrete wall underground around the station to keep groundwater and river water out of the station area. According to estimates, this construction method costs twice as much as traditional dewatering construction, but it saves the extraction and discharge of more than 100,000 cubic meters of groundwater. It is reported that Dahongmen Station requires 77 concrete walls; 32 diaphragm walls have been completed so far, and the remaining 45 are expected to be finished before the end of the year.

Dahongmen Station on Line 8 is a three-level underground station, one level more than a conventional station. The first basement level is the equipment level, the second is the concourse, and the third is the platform. The three-level design is mainly due to insufficient construction space, which reduced the station length from over 200 meters to 185 meters. Dahongmen Station will enable single-passage, two-way transfers with the existing Line 10, and the transfer passage is only 60 meters long, meaning citizens need to walk only about two minutes to transfer.

Phase III of Line 8 is the southern extension of Phase II, running from south of the National Art Museum of China in the north to Yinghai in Daxing in the south, with a total length of about 20.7 kilometers and 16 stations, all of which are underground except Demaozhuang and Yinghai stations on the southern extension. Because it passes through busy commercial areas such as Wangfujing, Qianmen and Zhushikou, construction difficulty is increased, and Phase III of Line 8 will adopt a phased opening and operation model. The section from Zhushikou Station to Yinghai Station is expected to open and operate in 2017. There is no clear timetable yet for the connection between the northern section from Qianmen Station to Wangfujing North Station and the National Art Museum of China station on Phase II of Line 8; it is expected to open as early as 2017. Once completed, Phase III of Line 8 will form, together with Phases I and II, an underground central axis nearly 50 kilometers long running north-south through the city, alleviating traffic congestion in the central urban area.