At the end of 2023, the diaphragm wall works at Huacheng Street Station of the Guangzhou East to Huadu Tiangui Intercity Railway Project (referred to as the "Guanghua Intercity Railway"), with China Railway 21st Bureau Group Co., Ltd. as the general contractor and Fujian Ruiyuan Tieke Construction Engineering Co., Ltd. as the specialized subcontractor, were successfully completed.

       Huacheng Street Station is the terminus of the Guangzhou East to Huadu Tiangui Intercity Railway, with a stabling line behind the station, and is an underground three-level island-platform station. The station is located north of the intersection of Huadu Avenue and Fenghuang North Road, and is laid out in a north-south direction along Fenghuang North Road. The total length of the station is 734.9 meters, of which the open-cut main body is about 469.38 meters long, with a standard section width of 24.5 meters. It is an underground three-level structure, with a main body building area of about 37,777.26 square meters (including the southern section and the large-chainage-end open-cut three-level portion, excluding the shield-driven section).

      The foundation pit support scheme for this project adopts the form of "1000 mm thick diaphragm wall + five vertical levels of bracing". The foundation pit depth of the standard section is 29.0 meters, and the end shaft foundation pit is about 33.1 meters deep. The principles for the embedment depth of the diaphragm wall are: 2 meters into slightly weathered rock, 3 meters into moderately weathered rock; for fully and strongly weathered strata, determined by calculation; in karst cave areas, the diaphragm wall is deepened, or at least plain concrete diaphragm wall penetrates through the karst soil caves and enters below the karst soil caves, entering intact rock stratum by no less than 1 meter or a stable aquiclude by no less than 1.5 meters. The concrete grade of the diaphragm wall is underwater C35 (P8).

      The station main body has a total of 205 diaphragm wall panels, with a diaphragm wall volume of more than 38,000 cubic meters and depths ranging from 32 meters to 49 meters. The geology within the station area, from top to bottom, is: backfill soil, plain fill, medium-coarse sand, gravelly sand, weathered rock (mainly limestone, as well as sandstone, tuff, and carbonaceous limestone), among which the natural compressive strength of limestone is up to 116 MPa. The diaphragm wall mainly adopts the I-beam joint type; the small-chainage end adopts the double-wheel trench cutter overlapping joint; within the large-diameter shield tunnel range at the end section, locked-pipe joints are used. The diaphragm wall structure construction is carried out by combining various processes such as pure milling and grab-milling according to site and different geological conditions.

The figure above is the geological profile of the left line

The figure above is the geological profile of the right line

       The project began construction on November 25, 2022. However, due to complex geological conditions and the fact that the station area is located in a karst-developed region with karst caves of varying sizes, with a karst cave rate of 49%, overall construction progress was slow. To ensure smooth project progress, Fujian Ruiyuan Tieke Company quickly mobilized a Bauer BCS 125 trench cutter, which arrived at the site in early March 2023.

       After the Bauer BCS 125 trench cutter arrived at the site, it immediately began high-intensity construction, operating 24 hours a day most of the time, and its construction efficiency was significantly higher than expected. Taking the first "full cut" of panel No. 37 as an example: the BCS 125 milled to 19.1 meters in 5.1 hours; from 19.1 meters to 27.0 meters in 4.8 hours, with an average efficiency of 1.65 meters/hour; from 27.0 meters to 32.1 meters in 2.4 hours, with an average efficiency of 2.17 meters/hour; the cumulative time to complete one "full cut" was 12.3 hours.

The figure above shows the limestone cut by the Bauer BCS 125 trench cutter

      The diaphragm wall project was completed on December 5, 2023. During the 9-month construction period, the BCS 125 completed an average of 10 panels per month. During this period, the equipment operated efficiently and stably throughout, with equipment operating time exceeding 4,000 hours.

      The BCS 125 is composed of the trench cutter, the synchronized hose reel system, and the carrier. The perfect combination of the three gives the Bauer double-wheel trench cutter the characteristics of fast trenching speed, simple and safe operation, and long service life. The Bauer BCS 125 double-wheel trench cutter has a total height of 32.39 meters, a working radius of only 4.84 meters, and a total working weight of about 156 tons. It can operate flexibly in compact urban environments and has obvious advantages in terms of noise and fuel consumption. Under continuous load on this project, the BCS 125 fuel consumption was only 43-54 liters/hour (averaging about 48.5 liters/hour).

       The BCS 125 inherits the excellent quality of Bauer double-wheel trench cutters. The application of advanced deviation-correction technology makes the verticality of the trench more precise; the excellent gearbox quality and powerful cutting capability ensure both construction stability and construction efficiency. The equipment is easy to disassemble and assemble, highly reliable, low in energy consumption, and low in overall operating cost, creating higher value for users.

      The BCS 125 can achieve a maximum trenching depth of up to 50 meters. The core components of the double-wheel cutter frame are precisely manufactured and can overcome the challenges posed by various complex strata to equipment failure rates and service life.

       Efficient construction cannot be achieved without sufficient power and excellent power conversion capability. The Bauer BCS 125 equipped with a China Stage IV engine has a power of 405 kW. The Bauer double-wheel trench cutter carrier applies the latest technology, with optimized design of structure, hydraulics, and electrical systems, providing ample power while minimizing fuel consumption to the greatest extent.

      The Bauer BCS 125 offers excellent safety and reliability. Its series of operation assistance systems and ergonomic design bring a comfortable experience to operators.