IN-SITU STRESS MEASUREMENT BY HYDRAULIC FRACTURING METHOD AROUND PANJI COAL MINE EXPLORATION AREA IN HUAINAN COALFIELD

Abstract

To obtain the distribution of in-situ stress in the peripheral exploration area of the Panji coal mine in Huainan coalfield, we used the hydraulic fracturing method and its device to test the in-situ stress in the deep exploration area of the study area.In this study, we completed the field measurement of three boreholes and 28 measuring points.The depths of the three boreholes were all over 1400 m.The maximum measuring point depth was 1460 m.Through actual measurement and analysis, we obtained the in-situ stress state and its distribution laws in the exploration area.The results show that: (1) The depth of the exploration area is within the range of 466~1460 m, the maximum horizontal principal stress is 13.62~54.58 MPa, the minimum horizontal principal stress is 11.79~37.93 MPa.The direction of the maximum horizontal principal stress is the NEE direction.The measured in-situ stress increases approximately linearly with the increase of depth.(2) The ratio of the maximum horizontal principal stress to the vertical stress in the exploration area ranges from 1.03 to 1.44, and the average ratio is 1.28, indicating that the in-situ stress state in the exploration area is dominated by horizontal stress.(3) In the area with a depth of more than 450 m, the in-situ stress field belongs to the type of tectonic stress field.With the increase of depth, the appearance of tectonic stress also increases.The measurement results can provide scientific basis for mine planning and coal mining design in the exploration area.