Zeche Prosper-Haniel, starting edge securing
The RAG intended to commence the hard coal mining at the working panel 123, seam Zollverein 1/2 in 2014. The aforementioned seam is characterised by a big thickness, by highly desorbable gas capacities in the building seam and a significant gas accumulation in the degassing. In addition to this, the building seam Zollverein 1/2 is imperilled by a considerable danger of self-inflammation. Therefore, an increased attentiveness was due with regards to fire and explosion prevention. During the process of coal mining, the caving method is utilised, meaning that alongisde the progress of the mining process, the roof layers above the seam behind the face support are breaking into the cavity that is no longer supported, subsequently compressing themselves over the course of time. This process is also called automatic backfilling, while the mineworker speaks of the Alter Mann (German, translates to old man).
Merely in the area of the former starting face gate, which is also called starting edge securing (rise drift), it is expected that a remaining cavity stays open during the further mining phase due to the chosen fitout form, where fire-damp can accumulate. Consequentially, in order to protect the two parallel mining headings, an explosion-proof dam has to be constructed at the starting edge securing toward each drift. With regards to its dimensioning, it has to apply to the guideline A 2.15 of the district council of Arnsberg, which means that it has to withstand a pressure of explosion of 5 bar, respectively 0,5 MPa.
In consequence of the current, big seam thickness of 4,00 to 4,20 m at the beginning of the mining, the design instructions usually applied in the field of mining lead, in this case, to a dam strength of 12 to 14 m (source: Handbuch für das Grubensrettungswesen im Steinkohlenbergbau, Hermülheim et al., VGE Verlag Essen 2007, page 154). These considerably big dam strengths do not seem appropriate for the actual task and are only viable at great expense in the operative downhole area. Therefore, RAG commissioned ZPP with the creation of a structural engineering calculation that adequately accounts for the given circumstances, while offering an optimisation for the usual procedure. Thereby, the to-be-realised starting edge securing are to be constructed in a way that ensures that they can reliably work as an explosion protection for the two parallel mining headings.
_Walkthrough and discussion of the recommended realisation plan with the client
_Development of the verification concept, based on the realisation plan
_Visual inspection of the rock mechanical parameters
_Definition of the effective loads (rock pressure, explosion pressure and dead load)
_Evidence for the permissible stresses in the dam structure
_Evidence for the sufficient load cut and fill into the in-situ rock mass
_Anchorage of auxiliary supports (for the load cut and fill) in the rock mass
_Presets for the execution of construction work
_Contemplation of variants
_Creation of the approval document