Shenzhen-Huizhou Intercity Railway

A large tunnel boring machine with a white body, blue cutting head with multiple tools, and orange support structures inside an industrial facility.

Φ 9.13m CREG EPB TBM

Depth: 41m

Project year: 2025

Cross-section diagram of a geological formation showing different layers of rock and soil with labels and annotations in Chinese. The diagram includes blue markers indicating tunnels or pathways, red and orange areas representing different rock types or zones, and red arrows pointing left and right with percentages of 28% and 11.4% respectively.
An aerial map of a city area highlighting different locations, with a red and yellow transit route passing through various stations. Several photographs of buildings and landmarks are displayed along the top and bottom edges, with labels in Chinese describing each site.
A cow standing under a railway bridge or structure, possibly washed or covered in mud.

Project Summary

Route Overview:

  • Location:

    • Overburden ranges from 12.5 to 171.1m, with longitudinal slopes of 28‰, 11.4‰, and 2‰

    • Developed fissures running along both sides of the fault zone. It worsened water ingress, with rock instability

  • Tunnelling Work

    • Tunnel passes through slightly weathered sandstone, slate and fault fracture zones

    • Groundwater table elevates between 38.73 and 48.38m. The tunnel is at 41m.

Construction Difficulties

  • High groundwater content, fissures, and low clay content caused severe dilution of conditioning agents (e.g., bentonite and chemical slurry) by groundwater. This prevented the formation of "plug" at the screw conveyor gate, leading to serious water and soil spewing:

    • Fissures prevented air pressure buildup at the face

    • Rich groundwater and low clay content reduced effectiveness of conventional conditioning slurries;

    • Intermittent muck flow causes poor belt transport and slurry spills into the tunnel, increasing cleanup time.

    • Project halted for 12 months after finding 0 solutions

Workers repairing or inspecting a damaged train track and underside of a train car in an underground tunnel.

Before Jello-Mud was implemented at this jobsite. Photos taken by the contractor at the screw conveyor

Jello-Mud Results

  • Jello-Mud is injected into excavation chamber (positions 3 and 9), the cutterhead rotates for 20 minutes (0.5–1rpm, adjusted based on mucking conditions), no discharge from the screw conveyor at this stage; after mixing, the screw is slowly activated to observe discharge. Initial adjustment took 2–3 rings, with a 50% replacement of muck in the excavation chamber (60m³ Jello-Mud). During subsequent tunnelling, injection continues with a dosage of 15–20% (18–24m³).

  • To stabilize face pressure, Jello-Mud is injected through two upper-side holes in the middle shield. The initial injection volume is about 9m³; for each ring thereafter, inject 5–6m³, adjusted based on chamber pressure fluctuations.

  • Stable excavation chamber pressure - The air pressure system is set to 4.1bar during advancing.

  • After injecting Jello-Mud into the shield surrounding and excavation chamber, air loss is 1m³ every 3 minutes.

  • Stable screw conveyor discharge

  • Spewout solved within 1 day with Jello-Mud

Close-up images of parts within a machinery or engine, showing injection points and shield injection points with measurements.

Jello-Mud injection points (reserved grouting holes on TBM, no need to retrofit new injection holes)

Construction site with concrete and metal framework, possibly for a foundation or wall.
Multiple surveillance camera screens showing a train or subway station with damaged infrastructure, debris, and twisted metal.

Photos taken after Jello-Mud implementation by Balsam Laboratory technician. Screw conveyor discharge stabilized.