Tunnel and Underground Engineering Field
Engineering Background
During tunnel excavation, it is often necessary to pass through fault fracture zones, water-rich and weak rock formations, or areas of high stress. The fissure widths in such surrounding rocks typically range from 0.01 mm to 0.1 mm, and coupled with high groundwater pressure, these conditions pose significant risks, including sudden water and mud bursts at the face and instability of the surrounding rock.
Technical Challenges
Traditional ordinary cement (D50 ≥ 20 μm) particles are too coarse to penetrate microcracks;
Although chemical slurries can penetrate, they suffer from significant shrinkage, poor durability, and potential environmental hazards.
During construction, the materials are required to have high permeability, early strength characteristics, and high bond strength with the surrounding rock.
Product Corresponding Features
Particle size distribution: Type K1340 ultrafine cement has a D50 particle size of ≤3.85 μm and can penetrate cracks measuring 10–20 μm in width.
The K700 type has a D50 ≤ 5.3 μm and can penetrate cracks ranging from 20 to 50 μm in width.
Strength performance: 3-day strength ≥ 42 MPa – 52 MPa; 28-day strength ≥ 78 MPa.
Construction performance: Low viscosity, high fluidity, and adjustable setting time (initial set: 108–181 minutes).
Professional Processes and Parameters
Advanced curtain grouting/radial supplementary grouting: Form a dense, reinforced curtain before tunneling to effectively reduce the water pressure at the face.
Recommended parameters: Grouting pressure: 0.5–1.0 MPa (for small-diameter grouting pipes); water-cement ratio: 1.0–1.2.
Expected effect: The water inflow has decreased by more than 90%, the compressive strength of the surrounding rock has increased to between 5 MPa and 15 MPa, and the stability of the working face has been significantly enhanced.
Engineering benefits
Improve the propulsion efficiency of tunnel boring machines and reduce downtime caused by sudden water inflows.
Extend the service life of initial support and reduce the cost of secondary reinforcement.
Corresponding target department
Construction Unit Engineering Department, Owner’s Materials and Equipment Department, Tunnel Division of the Design Institute, Underground Engineering Team, Materials Supply Section.
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