Analysis of support by hydraulic props in a longwall working

This paper presents a study of the support system in an anthracite working situated in Feixolin (Northern Spain). The working is mined by the longwall method, caving being controlled by means of hydraulic props and wooden cribs. As the coal seam has an average thickness of 3.5 m and 30° slope, the workings do not meet Spanish regulations for the mining of longwall coal seams. This means that the support system must be studied and tested before it is definitively implemented in the mine.A detailed study of the materials that make up the coal seam and the surrounding rock mass was carried out, determining the geomechanical properties of these by means of both laboratory and in situ tests. To this end, a full scale experimental working was conditioned to carry out the tests, with special emphasis on the load plate tests and penetration load tests carried out with the actual hydraulic support props of the working.With the data thus obtained, the behaviour of the working was modelled using FLAC in order to determine the maximum pressure that the coal hanging wall and footwall is capable of supporting, as well as the density of the props and the conditions of the supports they rest on so that penetration of the props is not produced. The overall aim was to validate the intended support system for the underground mine.