Red-bed mudstone from civil excavation is often treated as waste due to its poor water stability and tendency to disintegrate. This study proposes a sustainable approach for its utilization in controlled low-strength material (CLSM) by blending it with cement and water. Laboratory tests evaluated the fresh properties (i.e., flowability, bleeding rate, setting time, and subsidence rate) and hardened properties (i.e., compressive strength, drying shrinkage, and wet-dry durability) of the CLSM. The analysis focused on two main parameters: cement-to-soil ratio (C/S) and water-to-solid ratio (W/S). The results show that increasing W/S significantly improves flowability, while increasing C/S also contributes positively. Flowability decreased exponentially over time, with an approximately 30% loss recorded after 3 h. Bleeding and subsidence rates rose sharply with higher W/S but were only marginally affected by C/S. To meet performance requirements, W/S should be kept below 52%. In addition, the setting times remained within 24 h for all mixtures tested. Compressive strength showed a negative correlation with W/S and a positive correlation with C/S. When C/S ranged from 8% to 16% and W/S from 44% to 56%, the compressive strengths ranged from 0.3 MPa to 1.22 MPa, meeting typical backfilling needs. Drying shrinkage was correlated positively with water loss, and it decreased with greater C/S. Notably, cement's addition significantly enhanced water stability. At a C/S of 12%, the specimens remained intact after 13 wet-dry cycles, retaining over 80% of their initial strength. Based on these findings, predictive models for strength and flowability were developed, and a mix design procedure was proposed. This resulted in two optimized proportions suitable for confined backfilling. This study provides a scientific basis for the resource-oriented reuse of red-bed mudstone in civil engineering projects.

Bottom vacuum preloading (BVP) is the method of applying vacuum pressure at the bottom zone of soils to generate pore-water pressure difference between the top and bottom boundaries, thereby achieving the consolidation drainage. This study conducted a large-size model test to explore the engineering feasibility of combining self-weight and BVP to treat construction waste slurry (CWS). Through the treatment of the measures of self-weight consolidation (0-26 d) and BVP with a water cover (26-78 d), the average water content of CWS declined from 255.6% to 115.9%, and the volume reduction ratio reached 0.476. However, since these two measures could properly treat only the bottom CWS, the measures of BVP with the mud cover (78-141 d) and the natural air-drying (141-434 d) were performed to further decrease the CWS water content near the upper zone. The latter two-stage measures reduced the average water content of CWS to 84.9% and increased the volume reduction ratio to 0.581. Moreover, the measurements suggested that the treated CWS largely exhibited a shear strength of 10 kPa or more. Overall, the proposed approach appeared some engineering feasibility to treat CWS, and the performed test study could act as a reference for the practical treatment of CWS.

Submerged floating tunnels (SFTs) represent a promising innovative transportation infrastructure, offering advantages for crossing long, large, and deep bodies of water in the future. However, critical issues regarding their responses mechanism and technique remain unclear, leading to the absence of constructed SFT prototypes globally. A pier-type SFT (PSFT) is a typical SFT configuration with relatively high stability and safety. This study reviews the progress in PSFT research and discusses critical issues and solutions, including structural design, dynamic response characteristics, and feasibility analysis. Suggestions are provided for future research and applications. PSFTs can be considered as immersed tunnels supported by underwater bridge piers. Although adequate research has been conducted on piers, piles, and tunnel tubes, limited investigations have focused on PSFTs. Existing studies are primarily based on conceptual designs of PSFT, lacking theoretical and experimental investigations. The dynamic response characteristics and progressive collapse mechanism of PSFTs under the influence of waves, currents, and earthquakes are complicated. Scouring and liquefaction can significantly reduce the bearing capacity and alter the dynamic responses of PSFTs. Refined numerical simulations and underwater shaking table tests for PSFTs remain limited. In addition, the performance degradation mechanism and damage evolution process caused by accidental loads, such as impact and explosion, should be emphasized. PSFTs are recommended for broad waters with depths ranging from 30 m to 150 m and lengths larger than 1000 m. Although construction technologies for PSFT components are sufficient and mature, guidelines specifically for PSFTs remain imperative. This highlights the necessity for extensive investigations on PSFTs, considering their mechanism and characteristics under extreme environmental loads.

Drilling-waste management is of great importance in the oil and gas industry due to the substantial volume of multi-component waste generated during the production process. Improper waste handling can pose serious environmental risks, including soil and water contamination and the release of harmful chemicals. Failure to properly manage waste can result in large fines and legal consequences, as well as damage to corporate reputation. Proper drilling-waste management is essential to mitigate these risks and ensure the sustainable and responsible operation of oil and gas projects. It involves the use of advanced technologies and best practices to treat and utilize drilling waste in an environmentally safe and cost-effective manner. This article describes a feasibility study of four drilling-waste management options in the context of the Khanty-Mansi Autonomous Okrug of Russia. For ten years of the project life, the NPV under the base scenario is equal to RUB -3374.3 million, under the first scenario is equal to RUB -1466.7 million, under the second scenario is equal to RUB -1666.8 million and under the third scenario is equal to RUB -792.4 million. When considering projects, regardless of oil production, the project under the third scenario pays off in 7.8 years and the NPV is RUB 7.04 million. The MCD and MCV parameters were calculated to be 106 km and 2290 tons, respectively. Furthermore, the study estimates the ecological damage prevented and the environmental effect of each option. Quantitative risk assessments, conducted through sensitivity analysis, reveal that the fourth option, involving the conversion of drilling waste into construction materials, emerges as the most economically feasible. The study also evaluates the interaction between business and government and analyzes the current situation in the sphere of drilling-waste management, concluding with concise recommendations for both companies and official bodies.