Crime
As a cave-in is referred to in the geology, the stepwise forming high work of a cavity volume in the direction of the earth's surface. Breaks are associated with a mass deficit underground. Fractures can occur over or in different cavities.
Basics
Underground cavities are seldom stable, in most cases the vault breaks down over a cavity until a relatively stable and load-bearing vault has formed. The overburden can collapse suddenly or gradually. But even when the vault is in a relatively stable condition, the rest of the overburden can break down due to vibration or moisture penetration. The free space is partially or completely filled by the subsequent masses. A partial backfill is referred to as a partial breach and a complete backfill as a full breach. This breaking process takes place in an almost vertical chimney. An essential prerequisite for a collapse is the degree of loosening of the mountains; this increases the closer the distance to the earth's surface is. Due to the higher degree of loosening of the mountains on the earth's surface, the movement of the cavity towards the earth's surface is also accelerated.
Influencing factors
Burst events are dependent on many, often non-measurable, factors. In addition to the geology of the overburden and the groundwater levels, the weather conditions also have an influence on a discharge event. All of these factors and their interaction make it difficult to make an accurate prediction of a consumption event. Crash processes are favored by larger underground cavities, such as those found in B. occur in underground mining at route crossings or during mining . The erosion processes are intensified in overburden with weakly cohesive loose rock. The existing rock has a significant influence on the high fracture rate; in the case of stratified rock, it changes with each layer. The cohesion of the rock layers is the most important influencing factor for the high breaking speed. The higher the cohesion of the rock layers, the lower the high fracture rate. In the case of homogeneous rock layers, subsequent eruptions can occur in bursts, the reason for this being the time-dependent relocations of stress in the rock.
End of process
How a breaking process ends depends mainly on the thickness and nature of the overburden. If the overburden is thin, a collapse will work its way up to the surface. If the volume of the broken material exceeds the capacity of the cavity, the breakdown is stopped. The reason for this is that the collapse mass has a much larger volume than the unspoiled rock. The high fracture process can also come to a standstill under layers with high cohesion. Above a certain thickness of the overburden, the border covering rock thickness H max , the breaking up of the fracture process to the surface is theoretically impossible. The collapse is thus dead in the overburden. The thickness of the boundary overburden is essentially determined by the angle of repose of the overburden and the size of the cavity height of the primary cavity. The angle of repose of the overburden is determined by the type of overburden, the water conditions and the water solubility of the overburden. However, the angles of the collapse slopes are in an unstable state, so that an exact calculation of the collapse process is difficult.
Various fractions
Fractures are divided into naturally occurring and through human intervention. The term " sinkhole " is used to describe a collapse that has fallen over natural cavities (e.g. karst ). Cracks caused by man-made cavities are broken down into day breaks and shaft breaks . The reason for this is the geomechanical differences in the fracture process. Manhole breaches are characterized by a more or less sudden loss of the manhole filling including any built-in components. As a rule, day breaks are not characterized by a broken chimney that is not marked in this way. All of these fractures are typically expensive and can even cause loss of life, depending on the area in which they occur.
Individual evidence
- ↑ a b c Jörg Meier: Statistical analysis of day breaks over mining fields of the brown coal civil engineering and an attempt of their numerical simulation with the program FLAC. Online (PDF; 288 kB) (accessed September 26, 2016).
- ↑ a b c Dieter D. Genske: Engineering geology basics and application. Springer Verlag, Berlin Heidelberg 2006, ISBN 978-3-540-25756-1 .
- ↑ a b Jörg Meier: For daybreak simulation with numerical models in lignite civil engineering. Freiberg 2003. Online (PDF; 447 kB) (accessed on September 26, 2016).
- ^ Günter Meier: Numerical assessment of daybreak hazards in old mining areas . Online (PDF; 117 kB) (accessed September 26, 2016).
- ^ Günter Meier: sinkholes and day breaks - possibilities of numerical modeling. Online (PDF; 1.4 MB) (accessed September 26, 2016).
- ↑ Dimitrios Kolymbas: Geotechnical tunnel construction and tunnel mechanics . Springer-Verlag, Berlin Heidelberg New York 1998, ISBN 3-540-62805-3 .