Recently, as the "Jianquan No. 2" shield machine broke through the ground at Laotun Station, the Laotun Station–Shangbu District West Station section of Jinan Rail Transit Line 6, constructed under the general contracting of China Railway Shangtou and built by China Railway Shanghai Bureau, achieved smooth twin-line breakthrough. This section has the most risk sources and the most complex hydrogeological conditions on the entire line, and its breakthrough marks a new important milestone in shield construction on Line 6.

The twin-line section from Laotun Station to Shangbu District West Station has a total length of 3418.907 m, a minimum curve radius of 380 m, a "V"-shaped slope with a maximum gradient of 29‰, and mainly passes through silty clay, completely, strongly and moderately weathered diorite, and moderately weathered gabbro. The section involves upper-soft lower-hard strata and hard-rock tunneling, with rock strength reaching as high as 152 MPa, and requires crossing 73 risk sources and an 18-track comprehensive operating railway line.

In response to the geological characteristics of the shield section, the Line 6 project department of Jinan Rail Transit Group Construction Investment Company led participating units such as China Railway Shangtou and China Railway Shanghai Bureau to follow the overall "six in place" requirements—sound systems in place, refined responsibilities in place, risk control in place, hidden danger treatment in place, material reserves in place, and emergency response in place—to conduct scientific analysis, optimize plans, strictly control shield attitude and tunneling speed, and strengthen synchronous grouting and secondary grouting to ensure that tunnel alignment, buildings, railways and other settlement deformation remain within controllable ranges. They adopted the "clay-improving agent" and steel sleeve receiving methods, refined receiving guarantee measures item by item, and effectively protected the forward movement of the shield body. They also sampled and washed the muck and compared it with existing stratum survey results to confirm the current tunneling status so as to adjust tunneling parameters in a timely manner.

During construction, the Line 6 project department, together with participating units, closely monitored bottleneck issues such as segment supply and muck transport and continuously optimized construction organization. On-site duty was arranged in 24-hour shifts to ensure controllable safety and quality. During tunneling, workers repeatedly entered the chamber under pressure, enduring working pressure equivalent to diving 21 meters beneath the sea, akin to "embroidering on the seabed," ensuring that the twin-line shield safely passed beneath the railway line in only 23 days. They actively invited experts for discussion and verification, adopted the steel sleeve receiving method, and overcame difficulties such as complex receiving conditions and water-bearing confined aquifers in the strata, ensuring smooth shield breakthrough. At present, all participating units on the entire Jinan Rail Transit Line 6 are fully implementing the city's "Project Deepening Year" work requirements, actively carrying out the labor competition activity of "Deepening Reform, Shouldering Missions, Making Contributions and Striving to Be First in Metro Construction," pooling their efforts, overcoming difficulties, and setting off a climax of all-out construction across the line to boost project quality and efficiency. As of now, 22 stations on the entire line have been topped out, 20 sections have achieved twin-line breakthrough, and 16 stations and 8 sections have entered construction for electromechanical installation and decoration. Project construction is advancing steadily, efficiently and rapidly.