Stability Evaluation of Old and Unapproachable Underground Mine Workings below Surface Structures

There are many places in the different countries of the world where working in the underground mines have been done below surface structures such as railway lines, roads, buildings, villages/residential colonies, pipelines, etc. The workings are generally old, abandoned and presently unapproachable. In some places, important delicate surface structures are installed above a portion of old abandoned underground workings. Safety of these important surface structures above old underground mine workings is a serious concern in many countries all over the world. Many times, it is difficult to move or divert these surface structures due to a number of reasons including technical problems, the involvement of huge expenditures and socio-economic issues. There is a need to assess the stability of these places and the procedure to stabilise the places if found unstable to make the structures safe. Hence, there is a need of proper stability assessment of the ground below these surface structures. The railway line is one of such important structures, where stability should be ensured for the safety of the passengers. In India, many underground workings are present below railway lines. Most of the workings are old and unapproachable and their stability status is in doubt. Dismantling or diverting of the important railway lines is a high-level policy matter and involves huge time and money besides complicated socio-political issues like the rehabilitation of the affected people. But the safety of the commuters using railways passing over the coal-bearing areas having mining activities cannot be compromised. Therefore, it is highly preferable to take protective measures instead of dismantling and diversion of lines, wherever possible. It is necessary to establish the position and dimension of the inaccessible underground workings below these types of important surface structures and carry out its stability analysis to take appropriate protective measures for the safety of the structures and commuters. This paper highlights the delineation procedure of the unapproachable underground roadways below surface structures with special reference to railway lines and its stability evaluation with case studies. Appropriate protective measures have also been suggested which are proved to be effective and validated the results of the study.