An important way to improve concrete performance is the use of alkali-resistant glass fibers (ARGFs) as reinforcement. This paper is based on the problems of the cracking of the partition wall and lining seepage in Laoshan Tunnel, Qingdao, China. Two types of ARGFs were selected as reinforcement materials for the partition wall and lining concrete: high dispersion (HD) and high performance (HP); and the compressive strength (CS), tensile strength (TS), flexural strength (FS), and impervious performance (IP) of concrete with different gradations of the two types of fibers were investigated. The results show that although the CS of graded glass fiber reinforced concrete (G-GRC) is slightly decreased, the TS, FS, and IP of G-GRC are significantly improved. When the densities of the ARGFs of HD and HP are 0.6 and 5 kg/m3, respectively, G-GRC performs best; additionally, compared with ordinary concrete, the TS, FS, and IP of G-GRC are increased by 15.86%, 14.90%, and 31.58%, respectively. Meanwhile, the tension–compression ratio is increased by 22.29%, and the mechanical properties of concrete are remarkably enhanced. The research results were successfully applied to the construction of the Laoshan tunnel, and good engineering results were obtained.
Advancing urbanization in China requires large-scale high-rise construction and underground transportation projects. Consequently, there is an increasing number of deep foundation pits adjacent to water bodies, and accidents occur frequently. This study uses a numerical simulation method to study the stability of the deep foundation pit near water based on the Biot three-dimensional seepage-stress coupling model, with the open-cut section on the south bank of the Jinan Yellow River Tunnel Project as the engineering field test. This indicates the following: (1) the maximum horizontal displacement of the diaphragm wall occurred in the fifth excavation stage, and a horizontal brace effectively controlled the inward horizontal displacement of the foundation pit; (2) considering the effect of seepage in the soft soil foundation, the maximum vertical displacement of the ground surface at each excavation stage occurred adjacent to the underground continuous wall. As the depth of the foundation pit increased, the vertical surface settlement decreases gradually in the direction away from the excavation face; (3) considering the seepage conditions, within each interval of excavation of the foundation pit, the horizontal displacement of the continuous underground wall and ground settlement declined; and (4) the numerical simulation and field monitoring data were in good agreement. Under the conditions of accurate model simplification and parameter selection, numerical simulations can adequately forecast conditions of the actual project.
The theory of the steel-plastic geogrid employed in supporting engineering is behind the practice, seriously affecting its popularization and application in engineering. Thus the tensile strength and deflection of steel-plastic geogrid and its control of surrounding rock deformations were studied and analyzed using laboratory and engineering field tests. We have contrasted the tensile strength of steel-plastic geogrid to that of metal mesh. We have also contrasted the deflection deformation of the steel-plastic geogrid concrete slabs to that of the mesh concrete slabs. In the tensile strength test, we have tested the tensile properties of three different types of steel-plastic geogrid. In the defection deformation test, two kinds of steel-plastic geogrid concrete slabs and the mesh concrete slabs are made to investigate the load and displacement they bear. By combining with the experimental application of the Wohu Mountain iron mine, we summarized the process of steel-plastic geogrid construction and monitored the surrounding rock deformation of test section. Thus, we drew the following conclusions: (1) the tensile strength of the steel-plastic geogrid was greater than metal mesh; (2) compared with metal mesh concrete slabs, steel plastic grille with concrete slab had a larger deflection and its stress tolerance ability was better; (3) the use of the steel-plastic geogrid supporting in roadway can control the deformation of its bottom and sidewalls.
The steel–plastic compound geogrid has been widely used as a new reinforcement material in geotechnical engineering and other fields. Therefore, it is essential to fully understand the mechanical properties of steel–plastic compound geogrid-reinforced belts to utilize steel–plastic compound geogrids efficiently. In this study, tensile mechanical tests of steel wire, polyethylene geogrid belt, and steel–plastic compound geogrid-reinforced belt were conducted with respect to the tensile mechanical properties of steel–plastic compound geogrid-reinforced belts. In addition, the minimum reinforcement and optimal reinforcement ratios of steel–plastic compound geogrid-reinforced belts were summarized. The results showed that the steel–plastic compound geogrid-reinforced belts possessed an incongruent force of the internal steel wire during the tensile process. The tensile stress–strain curve of the steel–plastic compound geogrid-reinforced belt can be divided into the composite adjustment, steel wire breaking, and residual deformation stages. The tensile strength of the steel–plastic compound geogrid-reinforced belt is proportional to the diameter and number of steel wires in the reinforced belt. The minimum and optimum reinforcement ratios of steel wire in the steel–plastic compound geogrid-reinforced belt were 0.63% and 11.92%, respectively.
The Sanshandao gold mine is developed near the sea and has high-chloride ion content in the groundwater, resulting in serious corrosion of metal anchors and difficulty in maintaining metal anchors. To solve the corrosion problem of anchor rods in Sanshandao, the use of fiberglass anchor rods, instead of metal anchor rods, is proposed. To verify the feasibility of fiberglass anchor application, a fiberglass anchor (diameter: 27 mm) pulling test was conducted at the Sanshandao gold mine. The test results show that (1) the pull-out resistance of fiberglass anchor rods is better than those of metal pipe slit anchor rods and threaded anchor rods currently used in the Sanshandao gold mine; (2) the failure of fiberglass anchor rods is mainly because of the destruction of anchor washer discs and nuts, whose rods play only 69.90–77.7% of their performance and remain intact; (3) the fiberglass anchor rod was damaged to different degrees several times before the pulling failure, and the damage was accompanied by sound; (4) the fiberglass anchor continued to bear pressure after each damage until complete failure occurred; and (5) the anchor washer disc relative to the nut to allow the pressure effect can avoid nut pressure collapse and improve the pulling performance of the anchor rod to a certain extent simultaneously. Through the test, it was proved that the 27 mm fiberglass anchor can meet the support demand of the Sanshandao gold mine. It also provides an important reference for the promotion and application of fiberglass anchor rods in similar mines.
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