Advances in Civil Engineering

The deep sea is the frontier of materials research in the 21st century. Owing to the particularity of pressure (15–120 MPa), hydrothermal temperature (90–400°C), and explosive fluid (strong H₂S) in the deep-sea hydrothermal field environment, the research on the corrosion mechanism of service materials in this environment under the coupling action of many harsh factors is almost blank. It has become the bottleneck of equipment and material research and development for China to explore the deep sea. This paper reviews the research progress of corrosion mechanisms of deep-sea environmental materials at home and abroad, and forecasts the research trend and difficulties in this field, especially in the deep-sea hydrothermal field. At the same time, it points out the urgency of the construction of harsh environment materials platform and its relevance to the discipline construction of marine college.

In view of the current problems in China’s special education resource centers, such as lack of functional cognition and unreasonable architectural function and spatial organization, which result in the inability to coordinate regional education resources, the formulation and implementation of special education ISP program are undertaken, and the development of integrated education is promoted. This paper draws on the concept of integrated education in developed areas and the design wisdom of resource centers. The research is carried out from the perspective of meeting the behavior patterns and special needs of different users, and the perfect and reasonable functional composition and the key points of special space design are put forward, and the feasible design strategies are expressed through establishing the model and plane layout.

In order to promote the resin modifying agent applied into pavement materials, a type of resin modifying agent was selected as the modifier to prepare modified asphalt. The molecular crystal structure of the modifying material was characterized by using the X-ray diffraction test (XRD). The microstructure and element composition of PA6 was investigated through focused ion beam scanning electron microscopy (FIB-SEM). The thermal property and functional groups of PA6 were studied by thermogravimetric analysis-Fourier infrared spectroscopy (TG-FTIR) test. The physical property and rheological properties of PA modified asphalt were evaluated to confirm the applying feasibility of PA6 in asphalt. The results indicated that PA6 was the semicrystalline polymer and the existence of γ crystal form might improve the toughness of asphalt materials effectively. The thermal decomposition process of PA6 could be divided into three stages roughly: inert weight loss stage, rapid weight loss stage, and stable stage. The amount of PA6 modifier should be appropriately controlled during the application process to ensure the comprehensive effect of PA6 on high-temperature performance and low-temperature performance. The corresponding initial modulus attenuation value of PA modified asphalt was less than 70# asphalt under the same test conditions.

The utilization of coal bottom ash (CBA) and fly ash in concrete has become more common. For CBA concrete, curing conditions would influence the thermal properties of the concrete due to the high water absorption capacity of the CBA aggregate. In addition, CBA and fly ash contents in concrete affect the thermal properties of the concrete. Therefore, the effects of the drying conditions and the CBA and fly ash contents on the thermal conductivity of CBA concrete were investigated in this study. The thermal conductivity of concrete was measured under two different curing and drying conditions: oven-dried conditions and saturated surface-dry (SSD) conditions, with curing times of 28 and 91 days. The concrete mixtures also contained different levels of CBA and fly ash. Crushed sand in the concrete mixtures was replaced by CBA with replacement ratios of 25%, 50%, 75%, and 100% by volume. In addition, cement in the concrete mixture was substituted by fly ash with replacement ratios of 20 and 40% by volume. The thermal conductivity of concrete under the oven-dried conditions was much lower than that under the SSD conditions. Moreover, the thermal conductivity of the concrete decreased as the CBA content increased under both the oven-dried and SSD conditions. The material properties of the concrete, including unit weight, compressive strength, and ultrasonic velocity, were also measured in the study. Compared with the SSD conditions, the compressive strength, unit weight, and ultrasonic velocity of CBA concrete were considerably lower under the oven-dried conditions. Moreover, the relationships between the thermal conductivity and unit weight, compressive strength, and ultrasonic velocity were suggested.

In this paper, the methane hydrate phase transition process in deep-sea methane hydrate-bearing soil under heating and compression was simulated by the molecular dynamics method. The evolution of deep-sea methane hydrate-bearing soil’s microstructure, system energy, intermolecular interaction energy, and radial distribution function during heating and compression was investigated. The micromechanism of the influence of the methane hydrate phase transition on the mechanical properties of deep-sea methane hydrate-bearing soil was analyzed. The results demonstrated that the methane hydrate dissociation starts from both sides to the middle and the void spaces between the soil particles had nearly no change during the heating process. For the compression process, the methane hydrate on both sides and the middle dissociated at the same time, and the void spaces became smaller. The methane hydrate phase transition on the effects of mechanical properties of the deep-sea methane hydrate-bearing soil is mainly caused by three aspects. (1) the dissociation of methane hydrate incurs the decrease of methane hydrate saturation. The free water and methane molecules generated cannot migrate in time and thus lead to the increase of excess pore water press and excess pore gas press. (2) The dissipated energy causes the decrease of the effective stress between the soil particles. (3) Due to the methane hydrate decomposition, the free water molecules increase, which reduces the friction of soil particles.

In this paper, an investigation on the behaviour of RC beams with circular openings in the flexural zone and shear zone strengthened using steel plates is presented. Totally seven beams were cast: a control beam, one beam with a circular opening of size of one-third the depth of the beam (100 mmϕ) in the flexural zone, one beam with opening strengthened using the steel plate, one beam with a circular opening of size of 100 mmϕ in the shear zone, one beam with an opening in the shear zone strengthened using the steel plate, one beam with two circular openings of size of 100 mmϕ in the shear zone, and another beam with two openings in the shear zone strengthened using the steel plate. The experiments were conducted in a loading frame of 400 kN capacity. The beams were subjected to two-point loading. The ultimate load carrying capacity reduced marginally by 1.78% and 2.8% compared to that of the control beam when a circular opening of 100 mmϕ was provided in the flexural zone and shear zone, respectively, and when the opening was strengthened with steel plates, it reduced by 3.04% and 25%, respectively, but the ductility increased when steel plates were provided. Beams with an opening of size of one-third the depth of the beam (100 mmϕ) in the flexural zone strengthened with the steel plate can be provided, as the load carrying capacity is only marginally reduced compared to the control beam, and the ductility is more when compared with beams with unstrengthened openings.