Raise borer

Raise boring ( "Up Drilling" ) is a method of drilling a pilot hole along with the bottom-up drilling a circular shaft is drilled. The method is a fully mechanized Gestängebohrverfahren that is suitable for shaft-like structures with average depths. The raise boring was developed in the 1950s for the Metal Mining North America. It is praised as the most economical method of creating shafts.

Equipment

To make holes according to this method, a raise - boring machine is needed. The raise - boring machine is situated on the upper level. The machine is equipped with two different drill heads can be fitted, a smaller drill bit for the pilot hole and the raise boring head. The raise - boring head is also known as Reamer. The drill head for the pilot hole has a diameter of up to 311 millimeters. The drill head consists of several roller bits. Raise The drill has a diameter of up to six meters, it is equipped with multi-stage chisels. This extension drill head, depending on the rock type, equipped with differently shaped tapered rollers. In order to make a correction of the direction during the drilling of the pilot hole, modern drilling machines are equipped with an automatically controlled Zielbohrsystem. This consists of a Zielbohrsystem located directly behind the drill bit Zielbohreinheit, more measuring sensors for measuring the inclination, the control electronics and the control hydraulics. In order to correct the Zielbohrstangen during the drilling process in the horizontal plane, have the Zielbohrstangen control runners which are hydraulically extendible. For accurate determination of the direction of the bore Zielbohrstangen are equipped with a pulse generator, which sends the measured signals over the flushing water in the drill string to the control state of the machine. Also, all measured values ​​of the function monitoring wirelessly transmitted to the control state of the machine. Referred to as inclinometers measuring system of the drill string uses two electronic spirit levels. These Levels are arranged crosswise and serve targeted hole.

Drilling

Before the actual drilling can begin, first the shaft starting point has to be run with a mine workings. This is an access to the shaft bottom allows later. In addition, this a reservoir chamber for the cuttings, while an assembly chamber for the raise - boring head is created. The actual drilling process then proceeds in two steps, the preparation of the pilot hole and then the creation of the widened bore.

Pilot hole

An accurate pilot hole is a prerequisite for the success of the Raise Bore. Therefore, the pilot hole is always a significant risk for the preparation of bores by means of raise boring. For the accuracy of the pilot hole inhomogeneity and anisotropy of the mountains play an important role. Through steeply dipping layers with different hard rock can cause deviations of the pilot bore. Other factors influencing the accuracy of the bore are technical requirements, such as the rigidity of the drill string and the care of the drilling crew. The drill head is rotatably pressed into the mountains with a high contact pressure. The pilot hole must be large enough to accommodate the drill string for widening bore. Through the use of electronics in the drilling operation is continuously monitored for directional accuracy and if necessary corrected. When drilling rock small pieces are broken off from the rock. The cuttings are flushed by a water rinse to the starting point of the hole and dropped off there.

Reamer drilling

If the pilot hole has reached the deeper sole, the drill head is removed, a raise - drill the pilot hole and the desired size attached drawing, from bottom to top, widened accordingly. The extension drill head is in this case at a low speed, which in the case a drill bit diameter of 1.52 meters up to 15 revolutions per minute, rotated. With a boring head diameter of five meters, the number of revolutions is up to four revolutions per minute. This smooth running of the drill head is important. Which extension drill diameter can be eventually used up, depends on the depth of the shaft and the load of the drill string. The cuttings need not be flushed upwardly out of the wellbore, but falls downwards and can be carried away, if necessary. As the cuttings due to gravity fall down without addition of water, when pulling up the wear in the head is less than in the other direction. However, when pulling the drill head tensile forces act over a thousand kilo-newtons on the drill string. The drill bit and the drill string can be stabilized to the shaft wall by runners stabilizers. In the rock so it provides a smooth borehole wall. The shaft extension is introduced after completion of the bore. Often no attachment or a bore hole expansion is required.

Application

With the Raise boring slots are created with a diameter of up to six meters. Prerequisite for the application of this method is a stand solid mountains. The maximum depth in this process is at 1200 meters. Application examples are blind shafts that serve as underground connections between two line segments in a mine, or connections between a mining operations and the surface. In the rescue of the injured miners in Chile in 2010 the raise - boring method was applied as one of several variants.

Variants

Starting from the basic procedure - pilot hole, then expansion - there are different variants of the raise boring, which carry partially own names. Such holes can be tilted or pushed almost horizontally, or the pilot hole created by the bottom and then expanded from the top down.