MnO-based materials are one of the most promising cathodes for rechargeable zinc ion batteries (ZIBs) owing to their high energy density and abundant resources. However, the notorious electronic conductivity and large volumetric expansion issues have severely restricted their practical application. Herein, 1D nanowires (NWs) with abundant internal void space, composed of ultra-small MnO@C nanoreactors, is proposed to get rid of the above dilemma. Specifically, carbon layer dramatically enhances electrically conductive, the elaborated constructed void space between MnO@C nanoreactors effectively avoid the physical clogging and restacking of MnO, relieving the strain upon charge and discharge process, and ultimately ensuring cathode satisfactory integrity maintenance, different from traditional 1D NWs composite architecture. As expected, the NWs constructed by MnO@C nanoreactors exhibit the superior cycling stability (102.9% capacity retention after 2000 cycles) and good rate performance. Moreover, we firstly construct freestanding MnO@C NWs/CNTs film as cathode and assemble a quasi-solid-state ZIB by using soaking-free PAM hydrogel electrolyte. The device without extra binders and additives affords an impressive reversible capacity of 357.2 mAh g−1 at 0.1 A g−1, and remarkable volumetric energy density of 20.8 mWh cm−3 (higher than commercial Li thin-film battery). Furthermore, our soft-packaged ZIBs also exhibits satisfactory flexibility and high safety.
Collapse accident frequently occurs at tunnel export. In order to reveal the mechanism of this kind of tunnel collapse, three-dimensional elastic-plastic calculation model is established according to Maanshan mountain tunnel. Thick soft overburden, untimly support and rainwater infiltration are considered as the main influencing factors of the tunnel collapse. Its special geological condition is determinative factor and rainwater infiltration is inducing factor. The study shows that collapse at tunnel export is induced by tunnel face instability and loose rock and soil mass collapse at tunnel roof. This kind of tunnel collapse belongs to the failure model which is induced by the combined action of shearing and tension. The support behind excavating face can prevent plastic zone extending to ground surface. It is better that the distance from excavating face is shorter. So the primary support should be constructed timely and advanced support is necessary. The best length of advanced support is 5 m. At the end of this paper, the influence of rainfall to surrounding rock is analyzed through field monitoring data of surface settlement and surrounding rock pressure. It is presented that rainwater infiltration can accelerate the failure of surrounding rock and its influence effect mainly reflects on 1 to 2 days after rainfall. So waterproof and drainage measures should be done to prevent the collapse for rainy season construction.
The application of integrated geophysical prospecting technique to the investigation of ground fracture hazards was described in combination with the ground fracture hazards project.The geological problems that can be solved during the investigation of ground fracture hazards,the extent of solution,the applicable conditions and the accuracy show that the integrated geophysical prospecting technique is an digitalized high precision means to solve the problem of ground fracture hazards.
Rock-like materials generally manifest both strain-softening and pressure-dependent effects. The critical plastic strain corresponding to the residual state also increases with the confining pressure. In this case, all of the mechanical property parameters are the functions of plastic strain and confining pressure. The elastoplastic coupling strain-softening model (EPCSS) is established by dividing the elastic and plastic surrounding rock of circular openings into m and n annuli, respectively. When the range of each annulus is significantly small, the surrounding rock can be considered as isotropic and uniform. Then, the elastoplastic coupling analytical solutions can be derived by representing the material properties of each annulus with the corresponding value at each annulus's outer radius for both Mohr–Coulomb (M-C) and Hoek–Brown (H-B) rock masses, respectively. Based on the continuum conditions of adjacent annuli, the equations for determining the radius of each annulus were established. Finally, the solutions were validated by strain-softening rock mass, and examples of EPCSS rock mass were further studied.
The fault fracture zone is vital to the stability of the surrounding rock of tunnels in geological engineering. In this study, a three-dimensional numerical model was established for Wuzhuling Tunnel of Zhuji-Yongjia Highway in Zhejiang Province, China. The dynamic processes of tunnel excavation were simulated through the fault fracture zone. The deforming performance and stress distribution of surrounding rock were investigated. Moreover, the stability of surrounding rock in tunnels was analyzed with consideration of the slope angle and the width of the fault. The simulation results indicate that the fault fracture zone in the tunnel can reduce the stability of surrounding rock. The slope angle and the width of the fault all have obvious influences on the stability of surrounding rock in tunnels. Furthermore, the collapse processes of a tunnel in the construction steps were investigated in a laboratory model. Reasonable agreements can be obtained to validate the model presented here and the simulation results. When excavating tunnels in a fault fracture zone, numerical analysis can be performed to find the dangerous area at which collapse might occur easily. This study can provide useful information on a supporting structure to prevent collapse disaster when designing a tunnel.
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