Basking Ridge, NJ
NJAW-NJ Transit Commuter Rail
BORTECH was called upon by Voller's Contracting to analyze the project details and present a solution for the installation of 138' of 20" steel tunnel in a Basalt-Igneous volcanic rock. The Basalt rock cores presented unconfined compressive strength values of over 40,000 psi.
Previous to Bortech's arrival. The small boring unit (SBU) was employed and failed to penetrate the strength of the rock formation. The bearing cutters in the SBU simply cannot handle the force needed to penetrate rock greater than 20,000 psi rock formations.
BORTECH founder Robert A. Titanic Jr. designed and built a Horizontal Concentric Hammer system that is contained inside a lead casing that delivers pneumatic percussions when crowded while simultaneously rotating the cutting head. Mr. Titanic realized that the stout one inch wall lead casing would provide for a true bore path in unconsolidated formations.
Bortech worked with New Jersey American Water, Voller's Contracting and Engineers Mott MacDonald to get the Bortech Horizontal Hammer method (BHHM) approved by New Jersey Transit-Mass Transportation System. To date the BHHM was not an approved method of the railroad. NJ Transit approved the Bortech Horizontal Hammer Method after presenting the following;
The hammer can be removed for repairs while the ring bit and casing remain in the bore hole.
The overcut of the bore hole is only 0.66" thus not needing and external grouting of the bore hole.
The system works in unconsolidated, boulders, cobbles and gravel formations as well.
There is very little ground vibration produced. The pneumatic force transferred to the head is directed in line with the bore casing and does not radiate out. Also the impact fractures the rock with little vibration.
The decibel level is governed by the air compressors. The working hammer adds very little to the decibel level.
Bortech had previous projects that verified the performance of their system.
After the equipment was set up. The lead casing and hammer bit was advanced into the concrete starter block. Bortech also offers a 4-point stabilization attachment to assist in the starting "collaring in" of the drill head. Once the location of the head reached the hardest rock formation. Penetration rates between 3-5 feet per hour were realized while the hammer was in the working mode.