Difficult Microtunneling Conquered in Milwaukee

Super Excavators Inc. (SEI) of Menomonee Falls, Wisconsin, recently holed out on target after battling challenging conditions along a 1,670-ft alignment. After launching the Akkerman SL74C MTBM setup to install 72-in. RCP, obstructions and mixed-face conditions caused significant horizontal and vertical deviations at the face. The skilled operators at SEI quickly took notice of these inconsistencies through MTBM data as well as telemetry information provided by the Akkerman AZ100 Total Guidance System (TGS). Site personnel quickly reacted and halted their advancement to assess the situation.

In many cases, encountering obstacles in mixed-face conditions is detrimental to the project and will result in a rescue plan. Due to the quick actions of the operator, SEI was able to work with Akkerman engineers to develop an approved DTA update that incorporated a slight horizontal and vertical curve to purposefully control an alignment correction.

The new DTA was critical for the successful completion of the alignment. Not only did the alignment have to stay within a grade tolerance, the MTBM needed to intersect a manhole at the mid-point of the drive. Since the AZ100 can be dynamically programmed, the new DTA allowed SEI to successfully navigate the obstacles with an approved and controlled alignment correction that minimized pipe stresses and jacking forces.

This article appeared on the Akkerman Inc. website.

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