How are subway infrastructure crossings managed?

A subway infrastructure crossing is the point where a new pipeline (water, sewage, gas, fiber, etc.) crosses - or runs very close to - another existing installation, a railway, a river or a road. Its design and execution combine civil engineering, precision topography and sectorial regulations to avoid damage, interference or service stoppages.

Key management steps

1. Data collection and location of services
   Municipal GIS, as-built plans and vendor mapping. Geo-radars (GPR), electromagnetic locators and potholing to verify actual elevations.
2. Modeling and collision detection
   Integration in BIM/3D environment to calculate minimum clearances and bending radii. Typical criteria: > 300 mm between water and gas; > 1 D in front of high voltage lines.
3. Selection of the construction method

   Environment	Common techniques	Main advantages
   Short crosses and soft soil	Pipe jackingmicrotunneling	Control of slope and low surface disturbance
   Lengths > 150 m or curved routes	Horizontal Directional Drilling (HDD)	Longer range and progressive curvature
   Rocks or little overburden	Machined tunnel or pneumatic hammer	Rock speed and minimum deviation
   Parks, waterways or sensitive areas	Hint with shirt, auger boring	Reduced sludge volume and environmental footprint

4. Structural design and protection
   Steel or concrete jacket as shield pipe; filled with grout for load distribution. Anti-corrosion coatings and cathodic protection in parallel pipelines.
5. Permits and crossing agreements
   Agreements with road/railway administrations and service holders. Vibration and settlement studies required by ADIF, Roads or Port Authorities.
6. Construction and execution control
   Laser and gyroscope topographic stakeout (typical tolerance ± 10 mm/100 m). Real-time monitoring of thrust, torque, mud pressure and surface settlements.
7. Testing and commissioning
   CCTV or laser probe for alignment and ovality verification. Tightness test according to EN 1610 or API RP 1110 depending on the fluid.
8. Subsequent management
   As-built survey, GIS update and O&M manual. Scheduled inspections and telemetry to detect leaks or subsidence during the life cycle.

Good practice: define a "crossing window" in plan and elevation, with exclusion zone and future maintenance lane, so that new networks do not invade the critical space.