Evaluation of the stability of a shallow goaf in an open-pit iron mine is important for successful mining. Based on the idea of “rock disaster analysis and prediction combining field monitoring and numerical simulation,” a modification of Mathews stability graph is proposed, and a monitoring scheme combing stress, displacement, and surface subsidence is selected per the field geological condition. The displacement monitoring data and numerical model are combined, and the numerical model is corrected per the monitoring data; the time-dependent deformation and damage to the goaf is obtained; and its stability is comprehensively evaluated. Results show that the northern area is in a relatively stable stage, whilst the southern area has a certain risk of collapse. At last, the proposed framework was successfully used in the open-pit iron mine to evaluate the stability of the shallow goaf and can be used for reference to similar geological conditions.

Strengthening the base-angle of a roadway can have a beneficial impact on its overall stability, but the specific optimal parameter selection range is still unclear. Fast Lagrangian Analysis of Continua 3D (FLAC3D) software is used to carry out the stability analysis of 5 kinds of roadway models with different section shapes under the conditions of no support and different base-angle bolt support angles, and the simulation verification is carried out under the actual working conditions of the Sanshandao Gold Mine. The conclusion is as follows: without support, the self-stability of a tri-centric arch roadway is the best, and that of a rectangular roadway is the worst. When the base-angle bolt dip angle is between 15° and 45°, a better supporting effect can be obtained under the established 5 kinds of roadway sections. In the straight wall circular arch roadway of the Sanshandao Gold Mine, the roadway stability is the best when the angle of the base-angle bolt is 15°. However, changing the length of the base-angle bolt, even if the length of the base-angle bolt is increased to a certain extent, will decrease the overall supporting effect of the supporting structure. This paper can provide a reference for the selection of tunnel bottom corner bolt support parameters.

With the increase in mining depth, the risk of ground pressure disasters in yellow gold mines is becoming more and more serious. This paper carries out a borehole test for the pressure behavior in a non-coal mining area with a mining depth of more than 800 m in the Jiaodong area. The test results show that under a depth of 1050 m, the increase in the vertical principal stress is the same as the increase in the minimum horizontal principal stress, which is about 3 MPa per 100 m. When the depth increases to 1350 m, the vertical principal stress increases by about 3% per 100 m, and the self-weight stress and the maximum horizontal principal stress maintain a steady growth rate of about 3 MPa per 100 m. In addition, based on the test results, the operation of the ground pressure monitoring system in each mine is investigated. The investigation results show that in some of the roadway and stope mines with depths of more than 800 m, varying degrees of rock mass instability have occurred, and a few mines have had sporadic slight rockbursts, accounting for about 5%. There was a stress concentration area in the lower part of the goaf formed in the early stage of mining, and slight rockburst phenomena such as rock mass ejection have occurred; meanwhile, the area stability for normal production and construction was good, and there was no obvious ground pressure. This paper compares the researched mines horizontally as well as to international high-level mines and puts forward some suggestions, including: carrying out ground pressure investigations and improving the level of intelligence, which would provide countermeasures to balance the safety risks of deep mining, reducing all kinds of safety production accidents and providing a solid basis for risk prevention and supervision.

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This article applies the borehole strain observation technology to mine dynamic disaster monitoring for the first time, and uses the fractal box dimension to quantitatively analyse the time history change characteristics of borehole strain data and its correlation with rock bursts. The article uses the drilling multi-parameter test device to test in the mine, and judges the stress distribution by collecting the drilling parameter data obtained from the test hole of the working face of the test point. The study found that the application of borehole strain observation technology to mine dynamic disaster monitoring can directly and accurately record the micro-dynamic change process of rock mass in the area before and after the occurrence of rock burst. The fractal box dimension can quantify the complex changes and evaluation of strain data. Abnormal degree of water tide distortion.