THE SYSTEMIC ANALISYSIS OF THE INSTABILITY PHENOMENON OF THE MINING CONSTRUCTIONS IN THE COAL MINING EXPLOITATION JIU VALLEY- ROMANIA Susana ARAD &Victor ARAD 1 Dana COSMA 2 1 Petrosani University, 2675 Petrosani, Romania, s_arad@upet.ro, 2 The West University of Timisoara, Timisoara, Romania Abstract: The paper’s aim is to reduce the instability risk for the mining works, which could affect the underground mining constructions or the related surface areas. The subsystem of “rocks’ resistance” is analysed using the mechanical proprieties of rocks’mechanical resistance. These proprieties were observed and measured both “in situ” and in the laboratory. The effect of the rheological properties on the rupture phenomenon is also analysed using experimental data from few case studies. Keywords: instability, mining works, rocks, mechanical proprieties, rheological properties. 1. INTRODUCTION The Jiu Valley Basin is the largest coal basin in Romania, are carried out in 21 industrial units of CNH Petrosani. The Hard Coal National Company Petrosani, (CNH), carries out its activity in the hydrographic basin of the Jiu River along a length of 50 km and on an area of about 137 km 2 . The exploitation and the processing hard coal are carried out in 21 industrial units in this area. Mostly the mining of coal reserves in the Jiu Valley Basin is made in underground mines but there are some small open- pits in which are mined the outcropping reserves of some seams. Coal mining is carried out under ever-harder conditions due to the increased mining depth (1000m) and hazardous geo- mining conditions. One of the difficult problems, the specialists encounter is in this field is ensuring the mine workings stability. The paper’s aim is to reduce the instability risk for the mining works, which could affect the underground mining constructions or the related surface areas. 2. THE SYSTEMIC ANALISYSIS The study stages of the instability phenomena are rendered in figure 1 [3]. The assessment of the mining works' stability will be performed by taken into consideration the structural and physical characteristics of the rocks and the stress - strain state in the rock massif representing the input parameters. Assessing the action of disturbing factors connected to the mining activity, as well as the action of the natural, hydrological and mechanical factors, the system's response is analysed by means of the phenomenon of rock's burst and falling. The systemic approach of the problem concerning the stability of the mining works is leading to the assessment of the factors acting by means of the disturbing and causative parameters. This is achieved following the system response' analysis. The stability phenomenon is analysed by means of the stability criteria recommended by the specific literature. In the table no. 1 the stability factors determine the following situations: stability state, limit state or instability state. The instability of the mining works it is emphasized by means of: the tensile strength, the shearing strength and the state of tension- deformation of the mining work. 003_TA3.doc- 1 –