BEND AND BREAK-THROUGH

摘要

In the city of bend, Oregan, a machine that is set to revolutionize precision boring has made it's debut. The 300ft drive beneath a railroad has demonstrated the abilities of a remote controlled small boring unit (SBU) to stay on target. The SBU was driven through abrasive rock for some 100m and never wandered more than 17mm of course. If taken up by the industry, this machine, which cuts 36" (0.9m) bores in solid rock, would slash equipment costs by two thirds for projects where maintaining the line is critical, such as busy urban environments. In the past, the way you avoided microtunnelling on a critical line is to bore a bigger hole and make up deviation inside the casing when you lay your pipe. However, this has a number of setbacks. First, and perhaps my crucially, if you only have space for a 36" (0.9m) pipe, you can't bore a 48" (1.2m). Second, is price, a 48" (1.2m) casing is considerably more expensive than a 36" (0.9m) casing, the contractor is excavating less material and using less grout material in the annulus. But the machine has to be able to guarantee the grade.