The first phase of Nanning Rail Transit Line 4 is an east-west backbone line in Nanning's rail transit network. The line starts from Hongyun Road Station in the west, passes through major areas such as Dashatian District, Wuxiang Headquarters Base, and Wuxiang Railway Station, and finally reaches Longgang Station. The construction of this line will strengthen the east-west connection on the south bank of the Yongjiang River in Nanning, drive the development of Wuxiang New District, reinforce Nanning's "multi-center" urban layout, and provide strong momentum for the formation of a new center. As one of the stations on Nanning Rail Transit Line 4, Dashatian Station is an 11 m island platform station with a total length of 158.3 m and a standard section width of 23.1 m. It adopts an underground four-story double-column three-span box frame structure and is constructed by the open-cut method. The main retaining structure uses a bored pile + internal bracing support system. The figure below shows Dashatian Station under construction on Nanning Rail Transit Line 4. Currently, the project is intensively working on the construction of retaining piles, with a pile diameter of 1200 mm, a depth of 36~40 m, and a total of 241 piles. There are also other types of foundation piles on site, including diameters of 1000 mm and 1500 mm, with a maximum depth of about 58 m. These foundation piles all require excavation, and the design verticality requirement is less than 0.3%. The main geological conditions at Dashatian Station are as follows: (1) 0~4 m, backfill layer, containing concrete, construction waste, etc.; (2) 4~12 m, silty clay; (3) 12~40 m, mainly strongly weathered sandstone, with a small amount of mudstone interlayers. In some areas, the retaining piles need to be embedded 0.5~3 m into very hard slightly weathered quartz sandstone or limestone. The figure below shows strongly weathered sandstone drilled by a Bauer BG 30 rig. Considering the complexity of the geological conditions and the rock penetration depth of 20 m or more, in order to meet the construction needs and schedule requirements, the foundation engineering contractor Guangxi Junyu Construction Engineering Co., Ltd. deployed four drilling rigs, all from Bauer, including one BG 26 rig, one BG 28 rig, and two BG 30 rigs. One of the BG 30 (BT 80) rigs is a new model officially launched by Bauer in the first half of 2016. The new BG 30 (BT 80) rig adopts a 280 kW CAT C9 engine and Bauer's BT 80 self-made chassis, making the equipment more suitable for the high-load construction environment of foundation engineering, more stable during operation, and more powerful in performance. The main winch of the new BG 30 (BT 80) rig adopts a single-layer wire rope design, which greatly improves the service life of the wire rope and saves construction costs for customers. Bauer's new rigs are all equipped with automatic drilling functions, which can help operators work more efficiently during long-term hard rock drilling and reduce workload; the modular design makes the equipment easier to disassemble, transport, and install.

The BG 30 (BT 80) rig on site was purchased by the customer Guangxi Junyu Construction Engineering Co., Ltd. in September 2017 and put into construction on this project. According to on-site measured data, the new Bauer BG 30 (BT 80) rig completed a pile with a diameter of 1200 mm, a depth of 37.5 m, and penetration into 25 m of strongly weathered sandstone in less than 3 hours of pure drilling time. Through on-site practice, the high efficiency of the BG 30 rig and the economy of average fuel consumption are demonstrated. The figure below shows the new Bauer BG 30 (BT 80) rotary drilling rig in operation on site. In some areas, the retaining piles need to be embedded into very hard slightly weathered sandstone or limestone. The four Bauer BG rotary drilling rigs on site also demonstrated strong working capability, able to break the rock until reaching the design depth or more directly and efficiently core until completing a pile. The figures below show hard slightly weathered quartz sandstone and limestone cores extracted by Bauer BG rotary drilling rigs.
Due to the complexity and uncertainty of geological conditions, the construction time of foundation engineering is often critical to the progress of a project. Thanks to the efficient and stable working capability of Bauer BG rotary drilling rigs, the on-site schedule has been guaranteed, and other processes can proceed in an orderly manner. Bauer's customer's good reputation and on-site management have also been recognized by the general contractor and the owner.