Researches On Strength Weakening Mechanism And Control Of Water-enriched Roofs Of Roadway

When the surrounding rocks of roadway roof contain water in coal mine, the strength and integrality of roof rocks would be weaken significantly in process of wa-ter absorption and loss, large deformations of surrounding rocks even roof-fall acci-dent which have a strong impact on safety production of the mine will happen in se-vere case. Therefore, researches on strength weakening mechanism and control of water-enriched roofs in mine roadway will have an important science and engineering significance.Based on field investigation of engineering geological characteristics, deforma-tion destruction factors and roof strength weakening characteristics in water-enriched roadway, the concept of water-enriched roadway is put forward by this paper. In the meanwhile,this paper explains the meanings and features of water-enriched roadway.Aiming at the condition of roof in representative water-enriched roadway, the systematic researches about rock mineral components, microstructure characteristics, physical property and weakening rules of weak strata, the strength damage features of water-bearing sandstone under different water-bearing states and classification of wa-ter-bearing sandstone have been done in the laboratory. It is found that the roof strata in water-enriched roadway is rich in clay mineral with developmental intergranule pores and good connectivity, its lower strength after encountering water is the internal influence factor for strength weakening of roof. According to AE features of wa-ter-bearing sandstone under different water-bearing states, this paper presents a tech-nical principle of roof stability forecast in water-enriched roadway.Basic knowledge of elasto-plasticity theory is applied to research plastic zone ra-dius and displacement of surrounding rocks in water-enriched circular roadway under the condition of no support or anchor bolt support. It is found that plastic zone radius and displacement under the effect of water is bigger than the case without water. The change rules between plastic zone radius, displacement and in-situ stress, support strength, original seepage water pressure, effective water pressure coefficient, cohe-sion are analysed in water-enriched roadway. Roof strength weakening rules have been researched in detail by field hole detection combined with COMSOL3.5a mul-ti-field coupling numerical simulation software. Results indicate that roof fractures are still expanding and developing at stability period of excavating under the effect of water in water-enriched roadway and roof convergence increases gradually along with the augment of rock water ratio. Thus the basic principles and rules of roof strength weakening in water-enriched roadway are given by this paper.According to the roof physical mechanical properties of pre and post encounter-ing water, lithology of immediate roof and occurrence horizon of roof water, control technique system by roofs and by stages in different regions of water-enriched road-way is established by this paper. Results of field measurement and numerical simula-tion show that the rock fractures in occurrence position of water which has controlla-bility develop a lot, hereby the thinking of controlled drain and reasonable wa-ter-preserved technology is put forward to decrease the erosion weakening effect of rocks with water and increase own strength of surrounding rocks. FLAC simulation software is used to determine the main technological parameters of roof bolt support in water-enriched roadway. Field application shows that this coal mine gains fairly good technical and economic effect by the research achievements from this paper.