On July 22, 2024, the Shanghai Civil Engineering Society organized a project achievement evaluation meeting in the Third Business Division of Shanghai Chengtou Highway Investment (Group) Co., Ltd. for the project "Key Technologies for the Ultra-Long and Ultra-Large North Cross Passage Project in Shanghai's Central Urban Area," led by Shanghai Chengtou Highway Investment (Group) Co., Ltd. Representatives from Shanghai Chengtou Highway Investment (Group) Co., Ltd., Tongji University, and Shanghai Tunnel Engineering Co., Ltd. attended the meeting. Professor Zhou Biao of Tongji University, as the rapporteur, presented the project achievements.

Rapporteur Zhou Biao, Tongji UniversityProfessor introduces the project research results

The evaluation expert committee was chaired by Academicians Liang Wenhao and Zhu Hehua, with Professor Yang Jian, Professor Yuan Yong, Professor-level Senior Engineer Shi Beiling, Professor Liu Feiyu, and Professor-level Senior Engineer Ye Guoqiang as members. The committee discussed and approved the expert evaluation opinions.

Academicians Liang Wenhao and Zhu Hehua evaluate the project research results

With the continuous advancement of China's regional integration and urban renewal, as well as the growing urgency of people's demand for better travel, the contradiction among urban space, resources, and human demands will become increasingly prominent. The construction of underground roads, especially ultra-long underground roads, plays a major role in alleviating traffic congestion in central urban areas, improving the urban living environment, and promoting sustainable urban development. However, it also faces challenges such as intensive functional design in limited space, environmental protection during long-distance shield tunneling through central urban areas, and safe and rapid construction of complex entrance and exit nodes. Shanghai Chengtou Highway Investment (Group) Co., Ltd., together with Tongji University and other units, relying on the Shanghai North Cross Passage Project and driven by intelligent means, has spent more than ten years building the North Cross Passage Project, currently the longest underground road of over 15 meters in the world, and has formed a key technology system for the ultra-long and ultra-large North Cross Passage Project in Shanghai's central urban area. The main innovations achieved are as follows:

01  An intensive design technology for ultra-large and ultra-long underground roads with multiple entry and exit points was developed, achieving an intensive spatial layout in which the upper and lower levels of a 15-meter-class shield tunnel each have 6 lanes to meet two-way traffic operation.

Alignment optimization of the North Cross Passage

Aiming at improving the traffic capacity of underground roads and meeting the service capacity of entrances and exits along the route, the traffic operation characteristics of underground roads with left-in and right-out access were revealed, a safety evaluation method for ultra-long and ultra-large underground roads with multiple entry and exit points was established, a high-precision virtual simulation system for underground roads based on real light rendering technology was developed, and a complete set of technologies for active identification, early warning, and active control of underground road operation risks was constructed. An innovative intensive layout model was formed for multiple entry and exit of passenger cars in underground roads and for two-way entrance and exit ramps at a single shield shaft.

Vehicle operation characteristics in the merging and diverging areas of underground roads and the method for determining car-following and lane-changing modes

(a) Intensive layout of 4-lane ramps on the upper and lower levels of a single working shaft

(b) Intensive layout of 6 lanes on the upper and lower levels of the main line

Aiming at the disaster prevention and evacuation challenges under the spatial layout of multiple entry and exit points on the upper and lower levels of underground roads, an innovative upper-lower level connected smoke exhaust duct was adopted, the laws of network ventilation and smoke exhaust control under multiple entry and exit conditions were revealed, and a new smoke exhaust system for double-deck lanes was constructed. Intelligent ventilation and smoke exhaust control, fire early warning, and evacuation and rescue technologies for underground roads based on digital technology were proposed, a deep-learning-based intelligent fire service algorithm was developed, an intelligent disaster prevention system for underground roads was constructed, and an intelligent disaster prevention system for ultra-long and ultra-large underground roads with multiple entry and exit points was formed.

Upper-lower level connected smoke exhaust and scaled model test of an underground road with multiple entry and exit points

Schematic diagram of segmented evacuation and rescue disposal in fire accidents

02  Micro-disturbance control technology and equipment for long-distance and dense crossing of urban facility clusters by underground roads were developed, achieving deformation of less than 10 mm for continuous crossing of 64 roads and 13 rail transit lines.

Aiming at the challenges of pre-analysis of crossing risks and sharp curve design for ultra-long and ultra-large underground roads in central urban areas, a whole-process risk assessment method for underground road tunnels crossing urban facility clusters was proposed, and the Technical Standard for Shield-Tunnel Road Tunnels Crossing Urban Facilities was formulated, achieving pre-quantitative risk analysis and whole-process dynamic control. An innovative lining composite structure with the same ring width and multiple wedge amounts was proposed, and a construction control technology for sharp curves with super-large cross-section, no hinges, and large taper shield was formed, breaking through the limitation that the ratio of turning radius to shield diameter is less than 40, and realizing for the first time continuous "S"-shaped sharp curve turning with a minimum turning radius of 500 m for a slurry balance shield with a super-large cross-section of 15 m diameter.

15 m diameter large-taper shield machine

Aiming at the environmental protection challenges of long-distance shield tunneling in the complex environment of central urban areas, a super-large cross-section, hinge-free, large-taper shield machine was developed, a dry-mixed mortar synchronous grouting material satisfying workability and shear resistance was developed, a grouting control process flow and standards adapted to it were proposed, and a step-frequency ground-penetrating radar and a synchronous detection system for backfill grouting behind the wall were developed. Through coordinated adjustment of grouting parameters and secondary supplementary grouting, timely filling of the tail void was achieved, and active control of stratum loss and disturbance was realized at the source. A technology for skip-trench excavation and micro-disturbance control of underground roads crossing above rail transit lines was developed, solving the micro-disturbance control problem of long-distance and large-unloading-ratio excavation of small-angle foundation pits, with tunnel uplift controlled to less than 10 mm.

Schematic diagram of skip-trench excavation for an underground road crossing above rail transit

03  Low-impact construction technology and equipment for prefabricated assembly of three-dimensional interchanges of underground roads were developed, achieving safe and rapid bridge construction at complex interchange nodes without closing traffic.

Aiming at the challenges of rapid prefabricated assembly of bridges at interchange nodes of underground roads and low-environmental-impact construction, new rapid prefabricated assembly technologies and equipment such as prefabricated double-section bridge columns and integrated box girder anti-collision walls were pioneered, and new processes such as rapid grouting of component joints were innovated. Construction technology and equipment for resonance-free steel pipe piles were developed, using soil liquefaction to achieve rapid, low-noise, and low-slurry construction of steel pipe piles.

Aiming at the rapid assembly challenges of bridges at complex nodes such as large traffic intersections, railway crossings, and navigation channels without closing traffic, technologies and equipment for unsupported installation of long-span steel box girders, high-altitude scattered assembly of large-span steel box girders under multi-source strong constraints at interchange bridges, and multi-point incremental launching of long-span single-tie-arch bridges were developed. Construction technologies such as "segmental assembly, integral transport, and whole-span positioning" for long-span steel box girders, "large tower crane, high-altitude scattered assembly, and one-time crossing" and "cantilever version of long-span single-tie arch: launching first and cutting later" were innovatively proposed, solving the challenges of safe prefabricated assembly of elevated bridges under strong constraints at complex interchange nodes and rapid and safe construction of complex bridges without closing roads. For the first time, one-time positioning of a 65 m long-span steel box girder without supports at a key intersection in the central urban area, aerial scattered assembly and integral hoisting installation of a 70 m mid-span steel box girder were achieved, reducing interference with traffic and impact on the environment.

Schematic diagram of the construction technology for a long-span steel box girder crossing a traffic intersection in one span without closing traffic

Schematic diagram of bracket method construction (lower left)

Schematic diagram of one-span crossing construction (lower right)

The project results have obtained 39 authorized invention patents (including 2 PCT patents), 24 software copyrights, 1 provincial and ministerial-level construction method, participation in the compilation of 6 standards as lead or participating unit, publication of 2 monographs, and 38 academic papers. Expert appraisal considers that the overall project results have reached the international advanced level, and the technologies for long-distance smoke exhaust and segmented evacuation and rescue through upper-lower level connection of long and large underground roads and for micro-disturbance control of a 15 m diameter shield tunnel crossing facility clusters have reached the international leading level.

The project results have been successfully applied in the North Cross Passage Project, currently the world's longest underground road project, and have been promoted to more than 10 super-large diameter tunnel projects and more than 20 underground road projects in Shanghai, Guangzhou, Hangzhou, Nanjing, and other cities, with significant social, economic, and environmental benefits.