Deformation Control Technology for Surrounding Rock of Retaining Roadway Along Goaf under Close Distance Coal Seam Goaf

Aiming at the problems of high space occupation rate of traditional steel tube concrete pier column and easy sealing failure of jack up retractable pillar when the 4101 track crossheading as the retaining roadway along goaf under the close distance coal seam goaf (with an average distance of 3.0 m between No. 4 coal and No. 3 coal) of Gaojiazhuang Coal Mine of Shanxi Zhongyang Rongxin Coking Co., Ltd., a roof structure model is constructed through mechanical analysis, and a roadway side support technology scheme for thin-wall constrained concrete pier column is proposed, the wall thickness is reduced by over 30% compared to the traditional support scheme, and the "high resistance-large deformation" characteristic is achieved by utilizing the coordination of concrete and thin-wall. In addition, supporting measures such as high pre-stressed anchor cable reinforcement, advanced/lagged strengthening support and others are taken. The ground in-situ tests show that the compressive strength of pier columns with a diameter of 800 mm reaches over 10 000 kN, under the same bearing capacity, the net width occupied by a single pier column in the roadway is reduced from 0.8 m to 0.7 m, and the space utilization rate is improved by 12.5%. The on-site industrial test combined with ultrasonic geological radar detection results indicate that the development range of the roof fissure field in the stable section of the retaining roadway is 0-2.45 m, and the development range of the solid coal side fissure field is 0-2.85 m, both within the control range of anchor rod/cable. The maximum subsidence of the roof is about 203 mm, and the floor uplift amplitude is less than 50 mm, which is significantly improved compared to the traditional scheme. The surrounding rock deformation is controlled within a reasonable range, which further verifies the adaptability of this scheme.