Assessment Of Water Inrush Risk Of The Grouting Face Based On The Mining Effect

In this paper, Liuqiao No.2 Coal Mine was selected as the research object. The geological and hydrogeological conditions of mine field andⅡ615 working face were studied. The water inrush risk of mine andⅡ615 working face was evaluated by using five-figure and two-coefficient method. The physical and mechanical characteristics of the rock, water management features of the rock, rock mass structure ofⅡ615 working face floor were studied. Through wave velocity testing of borehole in situ and rock samples, the conversion relationship between rock and rock mass strength and the relationship between physical and mechanical parameters of rock mass before and after grouting were calculated, According to floor structure before and after grouting,Five geological models of the original floor, thickness increased floor, strength increased floor, strength and thickness increased floor, floor with casing were established. Numerical simulation was used to study the difference of mining effect of different floors was studied.Water inrush risk ofⅡ615 working face floor after grouting was evaluated by water inrush coefficient method. The main conclusions and understanding were as follows:1. Water inrush coefficient of No.6 Coal of southeast of mine field was small, at 0.02～0.06 MPa/m, the relatively safe area. Water inrush coefficient of northwest was larger, at 0.06～0.12 MPa/m, existing water inrush risk of Taiyuan limestone. Water inrush coefficient ofⅡ615 working face floor was at 0.05～0.07MPa/m, at the complete section of floor, Water inrush was less dangerous, at the areas of construction developed, danger of water inrush exist.2. Obtained from wave velocity test in situ:(1) Wave velocity of sandstone increased after grouting; Mudstone had not increased. (2) Whether grouting or not, the velocity of sandstonein construction zone was smaller than that of normal area. (3) Velocity of sandstone was greater than that of mudstone. Based on the velocity obtained before and after grouting, the the integrity of rock mass after grouting increased:the sandstone was 1.25 times, mudstone was 1.04 times, as the multiples of intensity increased after grouting.3. With the increase of thickness and strength of floor:the depth of floor failure, floor displacement and loose scope significantly reduced. The results reveal the effect of modification of floor rock mass structure in working face and the mining effect controlled by rock mass structure, the effect of grouting was quantitatively evaluated.4. On the basis of mining effect, water inrush risk of II 615 working face floor after grouting was evaluated by water inrush coefficient method, obtaining that water inrush coefficient ofⅡ615 working face floor after grouting was 0.042～0.056MPa/m, it significantly reduced 0.008-0.014MPa/m compared with it before grouting, indicating that effect of grouting was obvious.