Deep Earth and Deep Sea Engineering: Challenges, Theory and Advance Technologies

Overburden bed separation grouting is a green mining method to control surface subsidence and protect surface buildings (structures). The performance of cementitious grouting material is the key factor affecting grouting filling. Although offering good fluidity and low cost, the fly ash (FA) slurry demands a significant water supply, undergoes high dehydration rates, and lacks cementing property. These factors result in low grouting efficiency and negatively impact the safety of operations in complex-structure areas. This work developed a CBF + D series all-solid-waste cementitious grouting filling material with blast furnace slag (BFS), FA, carbide slag (CS), desulfurization gypsum (DG), and calcium chloride (CaCl₂) as components. Based on the orthogonal test, the basic performance test of the grouting material was carried out using macroscopic and microscopic test methods. The influences of the water–cement ratio, the mass ratio of BFS to FA, the proportion of CS, and the proportion of DG on the slurry density, fluidity, water extraction rate, and uniaxial compressive strength (UCS) of the stone body were assessed. The material’s hydration mechanism was analyzed by combining X-ray diffraction (XRD) and scanning electron microscopy (SEM) microscopic experiments. The optimal parameters for this test were as follows: a water–cement ratio of 0.7, a mass ratio of BFS to FA of 3:1, a proportion of CS of 40%, and a proportion of DG of 4%. Under the optimal conditions, the density of the slurry was 1.41 g·cm⁻³, with a fluidity of 15.7 cm, a water extraction rate of 0.107, and a UCS of the stone body of 6.25 MPa. The water extraction rate of the slurry is 67% lower than that of the FA slurry and the slurry has good cementation performance, while still maintaining its fluidity. This significantly enhanced the safety and applicability of the grouting filling process. In addition, CBF + D series all-solid-waste cementitious materials have solved the large accumulation of industrial wastes such as FA, BFS, and CS, which maximized the resource utilization rate of these wastes and brought significant economic benefits. Full article

Acid fracturing is essential in enhancing recovery efficiency, especially within carbonate reservoirs. Although extensive studies have been conducted on hydraulic fracturing, understanding the intricate dynamics between acid–rock reactions and fracture propagation in heterogeneous layered reservoirs remains limited. This study employs a comprehensive coupled hydro-mechanical-chemical flow framework to investigate acid fracturing processes in layered geological formations. The model incorporates a two-stage homogenization approach to account for rock heterogeneity, a dual-scale continuum framework for fluid flow and acid transport, and a phase field method for examining fracture propagation. We thoroughly examine how treatment parameters, particularly acid concentration and injection rate, affect fracture propagation modes. The analysis identifies three distinct propagation patterns: crossing, diversion, and arresting. These are influenced by the interplay between pressure buildup and wormhole formation. Initially, higher acid concentration aids in fracture crossing by lowering the peak pressure required for initiation, but excessive concentration results in arresting because it causes extensive wormhole development, which reduces fluid pressure. Similarly, the injection rate plays a crucial role in fracture movement across layer interfaces, with moderate rates optimizing propagation by balancing pressure and wormhole growth. This comprehensive modeling framework serves as a valuable prediction and control tool for acid fracture behavior in complex layered formations. Full article

Black carbon, a short-lived climate forcer, has the dual impact of intensifying global warming and polluting the atmosphere. The further opening of Arctic shipping routes has resulted in a severe issue of black carbon emissions in this fragile region. The use of fuel, especially heavy fuel oil, in international shipping has generated enormous black carbon emissions, posing a serious threat to the climate in the Arctic and beyond. As the international community continues to pay attention to air pollution control and greenhouse gas emissions reduction, the need for effective global governance of black carbon emissions from Arctic shipping has become increasingly evident. This issue has emerged as a critical part of the broader effort to address ocean and climate governance through the lens of international law. Despite the efforts made by both the International Maritime Organization (IMO) and the Arctic Council (AC) to reduce black carbon emissions, the current international legal framework remains fragmented, with weak enforcement mechanisms and limited capacity for coordinated governance. The findings of this research underscore the importance of strengthening international legal instruments aimed at reducing black carbon emissions from Arctic shipping. In particular, there is a pressing need for the development of a dedicated international treaty with enhanced binding force to mitigate the ecological degradation in the Arctic, address global warming, and realize sustainable development goals. Full article

Dense polymetallic nodule fields are found in different areas of the Pacific and Indian Oceans. However, limited knowledge exists about microbial diversity, processes and functions in deep-sea polymetallic nodule sediments. This study investigated microbial diversity, composition and function in sediments from various locations and depths in a western Pacific polymetallic nodule province. Sediment cores were collected, DNA extracted, and the V3–V4 regions of the 16S rRNA gene were sequenced using Illumina MiSeq. The test results show that the abundance and diversity of microbial communities in sediments from different sites vary significantly. The dominant microbial communities at the family level in the three sediment samples were all mainly Marinobacteraceae and Alcanivoracaceae. Sediment samples from core 1 had similar microbial structures and microbial community functions. Surface sediment had higher species richness, diversity and evenness than the middle layer. The dominant phylum at different depths was consistent. There was significant spatial heterogeneity in the microbial community within sediments from polymetallic nodule regions. This study expands on our knowledge of the spatial and vertical distribution of microbial community diversity beneath polymetallic nodules in deep-sea settings. Full article

The severe global hazards posed by marine microplastics must be given attention. This study evaluated the current international legal framework, and offers forward-looking recommendations for enhancing international law. The analysis began by examining the unique characteristics and profound impacts of marine microplastics, underscoring the necessity of a corresponding international regulatory regime. Through a thorough review of the existing global and regional legal instruments—both soft and hard laws—we identified key issues and challenges in the international legal response to marine microplastics, particularly in terms of legislation and enforcement mechanisms. The study emphasizes the urgent need for strengthened international legislation, including the potential development of a specialized international treaty, and calls for the enhancement of compliance mechanisms to effectively combat marine microplastic pollution and support the broader goal of sustainable development. Full article

The energy of a focused acoustic field is quite concentrated, and the ability of an acoustic vortex formed by a concave focusing transducer array to capture objects in a flowing medium remains to be investigated. In this paper, the focused pressure distributions generated by an acoustic lens and a concave focused transducer array are firstly simulated, and the analyzed results show that the focusing effect of the latter is significantly better than that of the former. The acoustic gradient force and orbital angular momentum density distributions of the focused transducer array were investigated. A focused acoustic vortex tiny object capture system was built by simulating the hydrothermal column that forms in the seafloor hydrothermal zone. It was discovered that the forces affecting microorganisms and other small objects primarily consist of acoustic gradient force, viscous force, and additional mass force. The non-destructive capture of tiny seafloor objects was accomplished by adjusting the focused acoustic vortex’s propagation direction and the transducer array’s emitted power, thereby enabling more potential applications in ocean equipment. Full article