Industry: Tunnel subway

Gas Monitoring Solution for Tunnel and Subway Construction and Operation

A dual-stage plan encompassing both the construction and operational phases, integrated with the ventilation system, involves setting up monitoring points every 100 meters

Industry Pain Points

The tunnel and subway construction is divided into two stages: the construction period and the operation period, each presenting distinct gas risks. During the construction period, there are risks associated with traversing gas-bearing strata (CH4 outburst), explosions generating CO + NO2 + dust, accumulation of CO from fuel-powered machinery exhaust, and oxygen deficiency in deep foundation pits (O2 < 19.5%). In the operation period, there are risks related to the accumulation of vehicle exhaust (CO + NO2 + PM2.5), SF6 leakage from substations, invasion of nearby underground pipelines (gas/sewage), and emergency smoke from fires. The interior of shield machine cabins, TBM control rooms, tunnel shafts, subway station transfer corridors, equipment rooms, and emergency evacuation passages are all risk blind spots. A gas-related accident, such as the gas explosion during a subway construction project in 2018, can have severe consequences—casualties, project delays, and tens of millions in rectification costs.

Solution Overview

Youri'an provides a two-stage tunnel and subway monitoring solution for both the construction and operational phases: ① **Construction Phase**: Fixed CH4 + CO + O2 + H2S probes (must be explosion-proof Ex d IIB T4) are mounted on the front cabin of shield/TBM equipment. Mobile methane laser telemetry instruments are installed on the excavation surface (for real-time scanning of gas emissions up to 100 meters away). Portable 4-in-1 pre-operation confirmation devices are used before and after blasting. Gas monitoring sub-stations are deployed in shafts/cross passages and connected to PLCs for ventilation control. ② **Operational Phase**: Distributed CO + NO2 + LEL probes are installed at the entrances of the station's fresh air systems, on platform levels, in concourses, at substations, and in equipment areas. Special SF6 monitoring is conducted in substations, with linkage to the fire smoke exhaust system in case of a fire. ③ The entire line is integrated into the BAS/comprehensive monitoring platform, achieving a closed loop of "detection → ventilation linkage → triggering evacuation → emergency team notification via SMS". Points are strictly arranged in accordance with GB 50157 + GB 51298 standards.

## Key Locations for Monitoring During the Construction Period

– **Front cabin of shield machine / TBM**: CH4 + O2 dual-parameter (explosion-proof gas layer)
– **Excavation face**: laser methane telemetry (non-contact scanning, extending up to 100m)
– **Shaft bottom / Cross passage**: CO + LEL + O2 + CO2 + Wind speed
– **Concrete mixing plant / Shotcrete and rock bolting area**: dust + CO
– **Operator**: Manually portable 4-in-1 (CH4 + CO + O2 + H2S) + infrared thermal imaging

## Key Locations for Operation Period

– **Station fresh air shaft entrance**: CO (preventing exhaust gas backflow) + PM2.5
– **Platform / Station Concourse**: CO + NO2 + CO2 (CO2 accumulation when personnel density is high)
– **Vehicle depot/maintenance workshop**: CH4 (hydrogen gas evolution during early thermal runaway of on-board batteries, H2 accumulation in VRLA batteries) + CO
– **35kV substation / traction substation**: SF6 + O2
– **Evacuation route / Emergency exit**: Fire smoke + CO linkage

## Key Technical Parameters

– Explosion-proof: During the construction period, it meets the requirements of Ex d IIB T4 (GB 3836)
– Protection: IP66 – IP67 (underground high humidity)
– Communication: RS485 + Modbus / CAN, BAS integration
– Range: CH4 0-100% LEL / CO 0-1000 ppm / NO2 0-50 ppm / SF6 0-1000 ppm

## Implementation Essentials

1. **Combined ventilation during construction**: When CH4 concentration is ≥ 0.5%, increase the air volume of the local fan; when it exceeds 1.5%, immediately stop work and evacuate personnel
2. **CO linkage during operation**: When the CO concentration in the station hall exceeds 30 ppm, initiate emergency ventilation
3. **Fire linkage**: Smoke detection + CO triggered simultaneously → Initiate mechanical smoke extraction + Fire shutter + Broadcast evacuation
4. **Personnel location tracking during construction**: UWB positioning + automatic positioning alarm for gas overrun, facilitating evacuation and personnel search

## Regulatory Basis

– GB 50157-2013 “Code for Design of Metro”
– GB 51298-2018 “Fire Prevention Standard for Metro Design”
– JTG D70-2-2014 “Design Specifications for Highway Tunnels”
– TB 10003-2016 “Code for Design of Railway Tunnel”
– Technical Code for Gas Prevention and Control in Underground Engineering (TB 10120-2019)

## Applicable Customers

Subway construction entities (Beijing, Shanghai, Shenzhen, Guangzhou, Chengdu, Wuhan, Hangzhou, and other subway groups); general contractors for highway/railway tunnel construction (China Railway Group / China Communications Construction Company); operation companies (subway operation, highway groups); ultra-long highway tunnels, cross-sea tunnels, pumped storage water diversion tunnels.

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