ABSTRACT
Glass-fiber reinforced polymer (GFRP) bars are increasingly widely used in slope support instead of steel bars or steel pipes. GFRP Bars are generally connected with the slope by combining conical nut and tray, but the tray stress still lacks corresponding theoretical calculation and strength verification methods. Therefore, assuming that the tray is an equal thickness thin plate, the internal force distribution of the tray is calculated using the thin plate bending and cavity expansion theory, and compared with the finite element numerical analysis results of the tray. The calculation and analysis show that the elastic theoretical solution of internal force distribution of equal thickness tray is basically the same as the numerical simulation solution of variable thickness tray. The tray loading and free surface are controlled by hoop tensile and radial compressive stress, respectively. The inner wall of the free surface of the tray is the weakest part of the tray, and the ultimate strength of a GFRP tray is 35.81-53.00% of the standard tensile strength of Φ20 GFRP bars by distortion energy density. This theoretical method can be used for stress analysis of variable thickness trays and has played technical support for promoting the application of GFRP bars in slope support.
ABSTRACT
This paper proposes a novel personnel positioning scheme for a tunnel network with blind areas, which compared with most existing schemes offers both low-cost and high-precision. Based on the data models of tunnel networks, measurement networks and mobile miners, the global positioning method is divided into four steps: (1) calculate the real time personnel location in local areas using a location engine, and send it to the upper computer through the gateway; (2) correct any localization errors resulting from the underground tunnel environmental interference; (3) determine the global three-dimensional position by coordinate transformation; (4) estimate the personnel locations in the blind areas. A prototype system constructed to verify the positioning performance shows that the proposed positioning system has good reliability, scalability, and positioning performance. In particular, the static localization error of the positioning system is less than 2.4 m in the underground tunnel environment and the moving estimation error is below 4.5 m in the corridor environment. The system was operated continuously over three months without any failures.
