One of the longest highway tunnel projects in the world required long horizontal holes to be drilled in advance of the tunnel face to explore geology ahead of the tunnel face.
The ground conditions were severely fractured and local drilling contractors were unable to penetrate beyond 100 m ahead of the tunnel face.
One of the local drilling contractors engaged Peter White to travel to Taiwan and to direct cement grouting operations in support of his horizontal drilling operation. Since it was not intended to undertake widespread rock grouting in advance of tunnel operations, the contractor’s requirement was only to stabilize ground conditions near the borehole to facilitate drilling operations.
Peter formulated a rapid-curing, high-density cement grout that also included 2% calcium chloride as an accelerator. With ambient temperature conditions of approximately 300C, the cement grout mixture cured within approximately 30 minutes after grouting.
Inflatable packers were used to isolate the bottom ungrouted section of the horizontal drill hole, to minimize the length of re-drilling when the contractor resumed the next stage of drilling.
By implementing the cement grouting system designed by Peter, the contractor was successful in horizontal drilling to depths of 400 to 500 m in each drill hole.