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Water-weakening effect is one of the most important factors inducing large deformation and stability problems of shale strata in the Huangjiazhai Tunnel. The influence of water on shale with various water contents and its mechanism still needs more study. In this paper, the X-ray diffraction and water absorption test were first conducted to determine the influence of mineral components on water-rock interaction. Then, a series of rock mechanical tests, including uniaxial compressive test, Brazilian disk test, and triaxial compressive test, were carried out on shale under dried condition, wetted condition with various water contents, and saturated condition. For the uniaxial compression, tension, and triaxial compression, the softening coefficient could reach 0.38, 0.63, and 0.52, respectively. Based on the macroscale experiments, a numerical case study of tunnel excavation was investigated to evaluate the water effect. Finally, with the aid of scanning electron microscope and failure morphology, the mechanism of water-weakening effect on shale was discussed from microscopic and macroscopic perspectives. The thickness of the double layer increases with the increase of water immersion time. This paper provides a set of useful data for reference in construction in shale strata, and a methodology to evaluate water-weakening effect through laboratory and numerical modelling approaches.

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Conversion of carbon dioxide (CO 2 ) and water (H 2 O) to methanol (CH 3 OH) is achieved through an artificial photosynthesis procedure utilizing cobalt (Co) micro-particle based photocatalyst and solar energy in a simple, closed reactor. The photocatalyst is fabricated by exposing the surfaces of cobalt microparticles to femtosecond laser irradiation in a gold chloride (AuCl) solution. The morphology and composite of the photocatalyst surfaces were observed and detected to be a layer of cobalt dioxide (CoO) nano-flakes on which some gold (Au) nanoparticles were deposited. The Au nanoparticles harvest the Sunlight energy through a plasmonic effect. The energy absorbed by Au nanoparticles creates electrons and holes which excite the H 2 O and CO 2 molecules adsorbed on CoO nanostructure surfaces to form excited hydrogen (H 2 ) * and excited carbon monoxide (CO) * on the CoO surface. The excited molecules combine to form CH 3 OH on the CoO surface. The Au/CoO/Co nanostructured surfaces are useful for developing a low-cost method to convert solar energy to chemical energy in the form of methanol.