The Research on Stability of Surrounding Rock in Gob-side Entry Driving in Deep and Thick Seam

The gob-side entry driving is driving in low pressure area, which bears less support pressure and is easy to maintain, so it is widely used. Taking the gob-side entry driving in thick coal seam of Dongtan Coal Mine as an example, the reasonable size of pillar and the section of roadway are numerically simulated by combining numerical with measurement, and the roadway support is designed. According to the distribution of lateral stress in working face, eight pillars of different sizes are designed. By simulating and comparing the stress distribution of surrounding rock and the development range and shape of plastic zone in different positions, the pillar size of gob-side entry driving is optimized to be 4.5m. According to the results of optimization of roadway section, the section of straight wall semi-circular arch roadway is adopted. According to the analysis, the roadway is supported by bolt + steel mesh + anchor cable. By observing the stability of roadway, it provides experience for the stability study of roadway the gob-side entry driving with small pillar in thick seam.

Combined Support Technology with Bolt, Steel Mesh and Anchor Applied in Baoxin Coal Mine

For the caving danger of the haulage roadway with thin and broken coal roof in Baoxin coal mine, the combined support technology with bolt, steel mesh and anchor was proposed. According to the geological conditions of the mine, the appropriate support program was determined. The simulation analysis by FLAC3D software showed that the program could effectively increase the roadway confining pressure, reduce roadway displacement and deformation, and thus keep the stability of the surrounding rock. Site practice showed that the support program was feasible and the control effect was good.

Development of Universal Breakaway Steel Post for Bullnose Median Barrier

A new fracturing-bolt universal breakaway steel post (UBSP) was developed and evaluated for use as a replacement for the controlled-release terminal (CRT) wood post currently used in the Thrie beam bullnose system. After numerous steel post concepts were investigated, a fracturing-bolt steel post was selected as the most promising design. The fracturing-bolt steel post successfully matched the strength and dynamic behavior of the CRT wood post in three impact orientations. The UBSP was incorporated into the Thrie beam bullnose barrier system and subjected to three full-scale vehicle crash tests according to the Test Level 3 guidelines provided in NCHRP Report 350. Test Designations 3–30, 3–31, and 3–38 were chosen to evaluate the performance of the Thrie beam bullnose system with UBSPs. All three full-scale crash tests demonstrated that the UBSP performed in a satisfactory manner in the bullnose system, as the vehicle was captured and safely brought to a controlled stop. On the basis of the successful completion of the three full-scale crash tests, it is recommended that the UBSP be considered a safe alternative to CRT posts in the original Thrie beam bullnose median barrier system. It is also noted that the performance of the UBSP suggests that it may have additional applications, including in long-span guardrail, end terminals, and guardrail in mow strips or encased in pavement.