Investigation of the system of pneumatic pre-stressed timber crib applied in TTK

Although the timber cribs are used to collapse the back of the longwall, they also play an important role in the support of various cavities because of their large load carrying capacities. Retreat longwall caving method has generally been applied in underground mines in Turkish Hard Coal Enterprise (TTK). In this system; timber cribs have been used to caving to the roof behind longwall exploitation face. Pre-Stressed Timber Crib Project developed as an alternative to classical timber crib was started to be applied in 2007 in TTK. This system, which has a new timber crib design and in-face supporting, was awarded in the "Mehmet Kemal Dedeman Research and Development Project Competition in 2007. This study includes information about support system used in underground and also longwall coal mining. On the other hand, a literature study has been carried out about parameters of face support design and given common information about timber cribs. In addition, the reasons for the transition to the "Pre-Stressed Timber Crib System" have been mentioned. In the light of on-site examinations and observations and the interviews with relevant workers in TTK for the purpose of the investigate of ÖGADD system in TTK; it was concluded that dismantling stages of timber cribs were performed in a shorter time compared to the classical system and also the system would provide the desired performance providing that the roof and floor rock were solid and the digging speed was not slow. When the airbags, an important part of the system, were deflated where located in the timber cribs, they became unable to function. The deflated airbags have been sent to the workshops located on the surface to diagnose defect on the airbag. In case of fault finding, it was observed that any holes and tears etc. on the airbag have caused the it out of use. Furthermore, in case of blasting for coal production in the face, deformations on the surface of the airbag were reduced when moving band curtains were placed in front of the airbags. The digging speed must be high in order to operate the ÖGADD system at desired performance. The loads on the timber cribs increase in case of low digging speed. The evaporation of ready-made timber crib materials which are another element of the ÖGADD system reduces the strength of the material and causes it to break easily.