Shoring

With mine roof or expansion is referred to in the mining Securing and keeping open spaces underground. The term refers collectively to all processes, to support or solidification of the rock (also called mountain ) which lead surrounding the cavity to be backed up (tunnels, tunnels, caverns ).

• 4.1 support expansion
• 4.2 Roofbolting

Basics

Only in a few areas of the mine to get completely without expansion. Often, the mines are heavily burdened by convergences due to degradation effects and must be protected by appropriate measures. Basically, the expansion is introduced so that the required clearance space of the Grubenbaues is maintained. Accordingly, when tunneling a larger outbreak profile must be ascended. This is necessary as to the mining cavity around secondary stress states are, the mechanical strain on the rock or the mountains. Due to the mountain the mountain pressure trying to fill the void created again. In the mining industry, a distinction between shaft lining, tunnel support and longwall.

Tasks of developing

The purpose of the expansion is to protect miners from falling rocks. In addition, the expansion will receive a minimum cross-section at the removed mine workings. The cross-section must be so great that the weather channel, driving experiences and the promotion are not hindered. In addition the development is intended to prevent the entering penetration of water into the mine workings as well as the complete collapsing of the mine. Furthermore should not only be completely compensated for by the expansion by way of the rock pressure, but also be re- directed back into the mountains.

Useful materials

When finishing materials wood, stone, metal and concrete.

Wood

The mine roof made ​​of wood is called Grubenzimmerung. All types of wood are suitable for Grubenzimmerung; some wood species have been found particularly useful. The best options are hard or resinous woods. The wood must have a certain thickness and strength. For the Grubenzimmerung well suitable woods are hard hardwoods such as oak, beech and alder or softwoods such as pine and spruce. Grubenzimmerung oak is particularly resistant to moisture, high temperature and so-called stagnant weather. Thus the Grubenzimmerung is resistant to moisture and rot, the wood above ground are impregnated with salt solutions. The salt solution penetrates into the wood and replaced the wood juices. Wood as a material expansion has the advantage that it is inexpensive to purchase and easy to work with, also wood over other finishing materials lighter weight. A disadvantage of the wood is that it usually can not be reused after use. Also can not use all wood; it is flammable, not weather resistant and can tolerate very low pressure. The cost of storage and transport costs are relatively high.

Stones

The mine roof by means of brick stones is called Grubenmauerung. Previously, only the Radstuben art wheels were first provided with a Grubenmauerung. To this end, the incoming gained in the mining rocks were worked appropriately and used. But also from surface obtained rubble or bricks the Grubenmauerung was created. One distinguishes the dry and the wet walling in Grubenmauerung. In dry walling is bricked without a binder in the wet walling working with binders such as lime and mortar. In dry walling breaking stones are used in the wet masonry is given to natural stone, brick, hut stones, sand-lime bricks or concrete blocks one.

Metal

The expansion of metal has been increasingly used in mining, as the iron is more cost effective ( cheaper ) was to acquire. Iron was first inserted into the workings where pit wood rotted quickly and easily. In the 19th century, cast iron and wrought iron were used as extension material. Stamps were made ​​of cast iron and used. In the first half of the 20th century, stamp made ​​of light metal were used. Today only steel is used for the mine roof made ​​of metal. These specially shaped profile parts or segments of steel are used. The steels that may be used must be standardized. The advantages of expanding steel are high compressive strength of the steel and its recyclability. Steel expansion is non-flammable and can be incorporated in part mechanically. Disadvantages are both the high cost and the potential total failure of removal.

Concrete

When removing concrete distinction is expanding with precast concrete parts, so-called tubbing, and the shotcrete lining. The shotcrete is applied to the ridges or bumps in the wet or dry process and hardens there. This causes the upgrading of the mountain by a weathering is largely prevented. Further, the shotcrete lining also has a supporting effect. This Ausbauart is combined site with the anchor expansion, with the braids is anchored serve as reinforcement for the concrete.

Method

Support expansion

When supporting expansion is further distinguished in rigid, articulated, flexible and agile - compliant expansion. The rigid extension are mainly in areas of application where there is no change in cross section or a supply of Grubenbaues to be, or where there is little ground pressure is expected. This usually refers to the main routes, Füllorte and caverns as similar workshops. Wooden components are used ( door frame ), arc-shaped steel components ( arch supports ) or masonry. The articulated expansion responds to rock movements by dodging and deformation of the cross section, without decreasing the loading gauge. The compliant expansion differs from loads from the mountains by telescoping the expansion elements, thereby avoiding high voltages on the expansion material. The disadvantage lies in the cross-sectional narrowing, which can lead to loss of navigability of the route.

Roofbolting

The principle is based on the expansion of the anchor strata of connection, such that a package is formed around the rock cavity to be secured, the greater resistance than the individual layers. Inasmuch, the roof bolting an upgrading of the mountain dar. Used different types of anchors, depending on the location, load and purpose. These can be combined with lagging mats or other braids. Roofbolting has the advantage that it can be produced quickly and incorporated fully mechanical. It is non-flammable and there are only low transport costs. However, the workload on introduction is high and it is not recyclable. In addition, the striking of materials and lifting equipment is not always possible and the armature expansion can not be used for all ground conditions.

Planning and selection

In the selection of the development of planning engineer, several considerations should be taken into account. Especially expected rock pressure must be taken into account. The costs associated with the rock pressure rock movements have an impact on the selection of removal. The area to be supported and the required service life of the expansion are other factors that the engineer must consider expansion. In the plans, the period must be taken into account, the time between the excavation of Grubenbaues and the contribution of removal. Whether a rigid or yielding lining is installed depends on the local conditions. In particular, have the nature of the hanging wall, the incidence as well as in the mining sector with the removal procedure an influence on the selection of removal. All these factors decide which expansion material which Ausbauart and what development density are used.