digilib@itb.ac.id +62 812 2508 8800

One of Indonesian longwall underground coal mining company located in East Kalimantan has alreadydeveloping a trial panel whose width is smaller than the planned width of the production panels. There are somesign of instability appear in the development tunnel. Geotechnical analysis was carried out to determine the causeof the instability and to provide supporting recommendations. The analysis was carried out on the cross-sectionalline passing through the development tunnel that was indicated experiencing instability, namely Tailgate 1.5(TGI1.5). Simulations carried out on Tail-Gate 1.5 show that excavation of the longwall trial panel will have animpact on the stability of the Tail-Gate 1.5 tunnel. This condition also has the potential to cause instability in theTail-Gate 1.5 development tunnel. It is recommended to sirengthan the support at the Tail-Gate 1.5 location whichis near the trial panel coliapsing zone by closing the space between the sieel set. Maximum load of 2.1 tons have10 be maintained so ihat he steel set does not failure. For steel set spacing can be set hy 0.75 meters or 0.5 meters.