Pre-Excavation Grouting through water bearing zone under high pressure under extreme flow conditions

The Yung-Chung-Tunnel in Taiwan, constructed for the Taiwan-East Railway Bureau, collapsed during construction when a water bearing, fractured marble zone was intersected. The inflow was approximately 4,000 liters/second. In spite of 30 relief holes the total inflow into the tunnel remained constant.

The pre-excavation grouting through the re-aligned tunnel had to be conducted under extreme flow-conditions. A hot bitumen grouting program was selected for technical and economical reasons out of 13 international proposals.
The technical challenges were:

• grouting under severe flow conditions
• high formation water pressures to be injected with hot bitumen at high temperatures and pressures

The hot bitumen grouting program resulted in a dramatic reduction in the hydraulic conductivity and stabilization of the formation and facilitated a problem-free excavation.