Study on Parameter Optimization and Mechanism of Rigid-Flexible Coupling Underground Engineering Structure of Steel Panel and Polymer

Polymer grouting is carried out between the steel panel and surrounding soil in underground engineering, and the polymer material consists of isocyanates and polyols. The isocyanate/polyol composite slurry expands rapidly due to chemical reaction and solidifies immediately. Then, a dense impermeable polymer layer is formed after rapid expansion of isocyanate and polyol, which is widely used for ground reinforcement and foundation remediation. Thus, a steel panel-polymer composite structure is developed. Mechanical properties of the steel panel-polymer structure are studied. The results show that the steel panel-polymer structure exhibited excellent mechanical properties. The steel panel and polymer layer should be designed above 3 mm and 10 mm in thickness, respectively. The steel panel showed superior mechanical properties to those of polymer layers. Considering good rigidity of the steel panel and good flexibility of the polymer layer, the steel panel and polymer layer presented perfect interfacial contact. It is concluded that the mechanical properties of the whole structure were increasingly enhanced with the increase of the steel panel thickness and the structural flexibility increased with the thickness of the polymer layer. Besides, the combination of the steel panel and polymer layer could also improve the mechanical properties of this coupling structure. This study provided an initial attempt for investigating the feasibility of applying polyurethane foam to steel panels in underground engineering. The stress analysis along the grouting direction inside the prefabricated wall was conducted. It may lay the foundation for further application of polymer grouting in underground engineering.

Experimental study on duplex assembled I-shaped steel panel dampers strengthened by CFRP sheets

The shear steel panel damper (SPD) is gradually used in the seismic design owing to the stable energy dissipation capacity. To date, most shear panels in the conventional SPD are welded with stiffeners against excessive local buckling. In this study, a duplex assembled I-shaped steel panel damper strengthened by CFRP sheets (C-DAISPD) is proposed to avoid the failure owing to undesired cracks in the web plate. A hot-rolled H-beam is processed to an energy dissipation unit with the web strengthened by the carbon fiber reinforced polymer (CFRP) sheets and stiffeners welded to the flanges. Then, two units are assembled back-to-back to form a damper. The C-DAISPD is developed to enhance the effect of buckling restraint, the ductility, and the sustainable stable energy absorption. Quasi-static tests of three specimens and numerical models were conducted to investigate the strengthening effect on the damper. The results indicated that the CFRP sheets benefited the hysteretic performance and the ductility of the C-DAISPD. The bearing capacity and the energy dissipation capacity could be significantly improved with the four-edge weld connection and the increase in the width of the web.

The application of compaction device for highway structural layer in the road construction of Yun-Mao Highway

The compaction device for highway structural layer is the hinge connection of the end of the hydraulic breaker rod of a conventional excavator and the base of a compaction device. During operation, the steel panel of the compaction device is positioned on top of the construction area, which is then compacted by controlling the hydraulic breaker of the excavator. This device can quickly and effectively solve the common quality issues such as the insufficient compactness of the earth shoulder in highway construction projects.