What is a dual-mode tunnel boring machine (TBM)? A dual-mode tunnel boring machine (DTM) is a full-face tunnel construction machine developed in the tunnel engineering field to address complex and variable strata. Its core advantage is the ability to flexibly switch between two tunneling modes based on geological conditions (such as hard rock/soft rock, intact/fragmented strata, clay soil/sand strata, etc.), without replacing the entire machine. This significantly improves construction efficiency, safety, and stratum adaptability, resolving the pain point of traditional single-mode equipment being unable to adapt to local conditions.

   I. Main Types

   1. Earth Pressure Balance-TBM Dual-Mode TBM

   ① Innovative Integration: Combining the technologies of an EPB shield (for soft soil/fragmented strata) and a hard rock TBM, the mode switch is achieved by switching the mucking system (belt conveyor or screw conveyor).

   ② Typical Projects:

   · "Tie Bing Guang Hua No. 6" (China Railway Construction Heavy Industry): The world's first large-diameter dual-shield earth pressure combined tunnel boring machine (TBM), successfully conquering interbedded soft soil and extremely hard rock in Guangzhou.

   · "Yong'an": my country's largest dual-mode shield machine (over 14 meters in diameter), capable of preventing landslides in earth pressure mode and efficiently breaking rock in TBM mode, equipped with an intelligent geological perception system.

   2. Earth Pressure Balance/Slurry Balance Dual-Mode TBM

   ① Key Technologies: Earth pressure mode stabilizes the excavation face, while slurry mode balances high water pressure with slurry. Both the pipe and screw systems support rapid switching (GB/T41053-2021 requires a mode switching time of ≤1.5 hours).

   ② Application Scenario: Complex formations with high water content sand and clay, such as the Guangzhou Metro Line 9 project, where settlement control accuracy is ≤3mm, effectively protecting buildings along the line.

   3. Open-Type/Slurry Dual-Mode TBM

   Design Highlights: Open mode efficiently excavates hard rock, while slurry mode addresses water-rich sand inrush. One-touch switching reduces the risk of water inrush, and a retractable baffle and soil transfer device ensure safety.

   II. Core Technology Breakthroughs

   1. Intelligent Mode Switching System

   ① Hydraulic control response time ≤ 0.5 seconds (GB/T41053 standard), with interchangeable cutters (scraper/roller cutter adaptive switching).

   ② Double-shield high-pressure sealing technology ensures safe excavation in water-rich formations (e.g., the "Qiangji" main drive seal features an independent water cooling system).

  2. Enhanced Geological Adaptability

   ① Advanced geological prediction system (3D laser scanning + roller cutter monitoring) optimizes excavation parameters in real time.

   ② Slurry mode graded decompression technology dynamically controls pressure fluctuations and suppresses surface subsidence.

   3. Structural Reliability Improvement

   ① Large-diameter cutterhead design (such as the "Yong'an" combined sealing technology) solves uneven load issues.

   ② The screw-type liner filtration structure improves maintenance efficiency by 80%.

  III. Typical Engineering Applications and Advantages

   ① Cross-river tunnels: In high-pressure sand layers (such as the Pearl River Delta project), the slurry mode stabilizes water pressure, while the earth pressure mode prevents gushing, ensuring safe passage.

   ② Urban deep tunnel projects: The "Qiangji" (diameter 12.68 meters), the world's largest earth pressure double-shield tunnel boring machine, uses a modular parallel drive system to overcome the limitations of alternating soft and hard strata.

   ③ Underground pipeline corridor construction: Dual-mode equipment utilization has increased by 40%, reducing the cost of purchasing multiple equipment and becoming a key development direction in the future (GB/T41053 prediction).

   Dual-mode tunnel boring machines break through geological barriers through technological integration. Their flexibility, intelligence, and high reliability are reshaping the paradigm of tunnel engineering.