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To prevent or reduce the loss caused by land subsidence in delta region, the land subsidence of the Zhuangxi–Wuhaozhuang oil area in Shengli Oilfield is predicted based on the elastic theory of porous medium and classical consolidation theory, and the prediction results are analyzed and verified by numerical simulation. The influencing factors and mechanism of land subsidence in delta resource exploitation area are studied. The research shows that: (1) the land subsidence in delta resource exploitation area is mainly caused by the underground brine exploitation, oil exploitation, consolidation of loose sediments, shallow groundwater exploitation, and soil load consolidation. The maximum land subsidence rate obtained by numerical simulation is 22 mm/a for single oil well and 81 mm/a for single brine well. (2) Pore pressure, physical and mechanical parameters of oil and brine reservoirs, development mode, and development degree are influencing factors of land subsidence in delta resource exploitation area, and pore pressure, permeability, and reservoir burial depth are controlling factors. (3) The exploitation wells in the Zhuangxi–Wuhaozhuang oil area are dense, and the influence range of land subsidence of different exploitation wells overlaps, which further aggravates the uneven land subsidence, and makes the result of InSAR subsidence monitoring larger. [ABSTRACT FROM AUTHOR]

In abandoned open-pit coal mines, surface water and groundwater form acidic waters with high concentrations of metal ions due to chemical interactions with ores such as pyrite, and the formation of acid mine drainage (AMD) is one of the major sources of pollution of world concern. For this reason, this paper reviews the formation mechanisms and influencing factors of AMD. It also describes the prediction, prevention, and remediation techniques for AMD, identifying key research gaps. It also discusses the current challenges and shortcomings faced globally in the management of AMD. The formation of AMD is mainly caused by the oxidation of pyrite in mines, but it is mainly influenced by history, climate, topography, and hydrogeology, making the formation mechanism of AMD extremely complex. Currently, the remediation technologies for AMD mainly include active treatment and passive treatment, which can effectively neutralize acidic wastewater. However, the prediction technology for AMD is blank, and the source treatment technology such as passivation and microencapsulation only stays in the experimental stage. This leads to the high cost of treatment technologies at this stage and the inability to identify potential risks in mines. Overall, this review provides remediation tools for AMD from predicting root causes to treatment. Geophysical technology is an effective method for predicting the motion path and pollution surface of AMD in the future, and resource recovery for AMD is a key point that must be paid attention to in the future. Finally, integrated treatment technologies that deserve further exploration need to be emphasized. [ABSTRACT FROM AUTHOR]

An exponential rise in global pollution and industrialization has led to significant economic and environmental problems due to the insufficient application of green technology for the chemical industry and energy production. Nowadays, the scientific and environmental/industrial communities push to apply new sustainable ways and/or materials for energy/environmental applications through the so-called circular (bio)economy. One of today's hottest topics is primarily valorizing available lignocellulosic biomass wastes into valuable materials for energy or environmentally related applications. This review aims to discuss, from both the chemistry and mechanistic points of view, the recent finding reported on the valorization of biomass wastes into valuable carbon materials. The sorption mechanisms using carbon materials prepared from biomass wastes by emphasizing the relationship between the synthesis route or/and surface modification and the retention performance were discussed towards the removal of organic and heavy metal pollutants from water or air (NOx, CO2, VOCs, SO2, and Hg0). Photocatalytic nanoparticle–coated biomass-based carbon materials have proved to be successful composites for water remediation. The review discusses and simplifies the most raised interfacial, photonic, and physical mechanisms that might take place on the surface of these composites under light irradiation. Finally, the review examines the economic benefits and circular bioeconomy and the challenges of transferring this technology to more comprehensive applications. [ABSTRACT FROM AUTHOR]

The Guantao Formation is the most important reservoir with significant faces developed, and this is different from the near-source accumulation of Nanpu sag. Guantao Formation in Matouying Uplift was found far away from the source area, which is a typical accumulation outside sources. What is the difference on accumulation condition and main controlling factors between the far-source accumulation and near-source accumulation? And what is the reasonable explanation for these reservoirs? According to the main controlling factors of Guantao Formation reservoir in Matouying Uplift, the abundant accumulation in hydrocarbon generation sag, efficient transport system and good spatial and temporal configuration of reservoir cap rock are the main controlling factors for its hydrocarbon accumulation outside sources. The hydrocarbon movement follows a migration model when it passes through a multiple faulted terrace zone and an effective connection to faults has an increase in the hydrocarbon abundance. The determination of oil sources and the correct understanding of the transport system are the keys to the reservoir understanding of the Guantao Formation in Matouying Uplift, as well as to the establishment of the reservoir model and the prediction of favorable oil and gas development areas. It provides enlightenment for the exploration of reservoir outside sources in peripheral convex and although oil and gas displays have been seen during single-well drilling, no large-scale reservoirs have been discovered until the industrial flow of oil and the results enrich the future exploration trend and potential areas in the uplift around the Nazione and Npu sag are determined. [ABSTRACT FROM AUTHOR]

Urban underground space (UUS) is an important resource to address the shortage of land, save resources and reduce environmental pollution, but it is irreversible. Therefore, it is necessary to evaluate its suitability before development. Rock mass is not only the carrier of UUS utilization, but also a key evaluation index, as it directly affects the evaluation results. Therefore, it is necessary to evaluate the 3D quality of rock mass from the perspective of UUS development. In this paper, a 3D quality evaluation model of rock mass in UUS is established based on an improved fuzzy analytic hierarchy process (IFAHP). Firstly, the subjective weight is calculated by analytic hierarchy process (AHP), and the objective weight is calculated by super-standard multiple method (SSMM). Then a new weight combination method (grey correlation analysis) is adopted. This method organically combines the subjective and objective weights, and the results show that the combined weight is more reasonable. Then the combination weight and fuzzy comprehensive evaluation method are combined with MapGIS to establish a 3D evaluation model. The case analysis shows that the evaluation results of the national standard BQ method are conservative, the traditional fuzzy analytic hierarchy process (TFAHP) is smaller, and the IFAHP is more robust. The case analysis also shows that the 3D evaluation has the advantages of strong intuition, good visualization and high precision, which is better than the traditional 2D evaluation. Moreover, the 3D evaluation model can not only be applied to this case, but also to other projects, and can provide decision-making for the development of UUS. [ABSTRACT FROM AUTHOR]

East Sichuan is rich in shallow natural gas; however, such gas substantially influences tunnel construction in the region. Accordingly, we analyzed the geological characteristics of shallow natural gas in eastern Sichuan and evaluated the risk the gas poses to tunnels along the Chongqing–Wanzhou (YW) high-speed railway employing a fuzzy synthetic evaluation approach. We conducted isothermal adsorption, gas chromatography, total organic carbon (TOC), carbon isotope, porosity and permeability, and field gas pressure test experiments and thin section examination of rock. Our results showed that the potentially harmful components in shallow natural gas in East Sichuan are mainly CH4, with small amounts of H2, CO, CO2, and H2S. The shallow natural gas mainly derives from shale and limestone in the Xujiahe and Ziliujing formations, but migrates to adjacent reservoirs through intraformational shear fractures in the strata. Sandstones of the Xujiahe and Shaximiao formations are porous reservoirs, with the best reservoir physical properties, belonging to the main enrichment strata of shallow natural gas in the region. Compared with the west of the study area, shallow natural gas is more developed in the east. According to synthetic evaluation of shallow natural gas influence presented in the paper, tunnels along the YW high-speed railway number eight in high-gas zones, four in medium gas zones, and two in no or low-gas zones. [ABSTRACT FROM AUTHOR]

The coal-bearing Longtan Formation is widely distributed in South China. However, its gas concentration often exceeds the standard limit in tunnels, which compromises the safety of tunnel construction and operation. In this study, statistical analysis of gas-bearing tunnels in the Longtan Formation (GTLF) and coal bed methane (CBM) experiment of Longtan Formation as related to engineering information, gas content, and pressure are discussed with the regional distribution features and influencing factors of GTLF revealed. The hazards of Longtan Formation in each province to tunnels are evaluated by fuzzy synthetic evaluation approach. The findings strongly suggest that the distribution of GTLF is characterized by east–west zonation and controlled by coal-rich zones and sedimentary facies. The western region is more harmful than the eastern region because of weak tectonic movement and more developed karstification. The influencing factors mainly include coal seam conditions, sedimentary environments, tectonic evolution history, hydrogeology, geological structure, and CBM weathering zone. Longtan Formation in Guizhou and Chongqing is the most harmful to tunnels. [ABSTRACT FROM AUTHOR]

Biochar (BC) has been extensively studied as adsorbent for the treatment of water pollution. Despite the distinct advantages, the high calcination temperature and low adsorption capacity of pristine BC limit its practical applications. Most of the former studies focused on the structure and/or surface modification to improve the adsorption capacity of BC. However, the harsh experiment conditions involved in the biochar modification limited the application in industrial level. Herein, we introduced mechanical treatment into BC preparation to reduce the calcination temperature and improve the adsorption capacity simultaneously. The results indicated that the calcination temperature was reduced and the adsorption capacity of the treated BC was improved after mechanochemical treatment. Characterization of the samples disclosed that BCs were graphitized with the particle size reduced to nanoscale after treatment. Adsorption tests indicated that the mechanochemically treated BCs showed much better removal performance of organic contaminants than that of pristine BCs. For instance, among four pristine BCs (BC600, BC700, BC800, and BC900), only BC900 has strong adsorption capacity for MB, while BC600 has low adsorption capacity (1.2 mg/g). By comparison, the adsorption capacity of MB increased greatly to 173.96 mg/g by BC600-500/1 (treated at 500 r/min for 1 hour). To optimize the mechanochemical treatment, the effects of rotation speed and agitation duration were also investigated. [ABSTRACT FROM AUTHOR]

To explore reasons for deformation of retaining soil and slope in the Maternal-Child Health Care Hospital of Hanyuan County, the meteorology, geological lithology, geological structure, and hydrological conditions were surveyed. Moreover, types and distributions of weak intercalated layers were found out by drilling, and physical and mechanical properties were obtained through physical mechanics and field shear test. Meanwhile, by means of drilling and monitoring, deformation range and characteristics of retaining soil and slope were determined, and deformation mechanism was obtained through monitoring crack opening and deep displacement. The structures showed that deformation occurred at new 2# counterweight retaining wall is caused by shallow slip control surface RJ0; the pulling and crack of settlement joints between the new 2# counterweight retaining wall and the new 1# slab-pile wall are caused by the deformation of shallow slip control surface RJ0; the deformation and failure of new 2# counterweight retaining wall and new 1# slab-pile wall and their foundation rock mass at the lower part are caused by creep displacement of "shallow weak intercalated layers" RJ0 and RJ1; in addition, the deep creep control surface RJ2 has certain influence on the deformation of upper building and its foundation rock mass. Therefore, anti-slide piles should be used to control the shallow slipping control surface RJ1, with the depth reaching the structural plane where the deep creep control surface RJ2 is located. [ABSTRACT FROM AUTHOR]

Coal fly ash (FA) is one of the main byproducts of coal burning. Nearly half of FA cannot be reused or recycled. The potential environmental leaching of trace elements in FA may limit its application. Microbially induced carbonate precipitation (MICP) is a promising technology to improve soil properties. This study was to investigate the effect of fly ash in MICP-stabilized soil on its mechanical and environmental impacts. Two kinds of fly ash were considered: FA1 was Class-F fly ash, FA2 was off-specific fly ash. The 0% (sand only), 3%, 6% and 9% content of FA were introduced to FA-sand mixtures to perform MICP process. Triaxial compression test was performed to evaluate the effect of FA content on the development of strength. The triaxial test results indicated that with 3% addition of FA, the peak deviator stress increased significantly. When MICP-treated sand mixed with 3% FA1, the deviator stress increased to 1,959 kPa compared to that of MICP-treated sand only samples of 800 kPa. The peak deviator stress increased by 154% and 115% when the additions of FA1 were 6% and 9%, respectively. The stress increase was caused by the bonding of precipitated CaCO3 in MICP However, higher content of FA1 (9% or higher) could restrict the activity of bacteria by reducing the void spaces. MICP-treated samples with the addition of FA2 presented a better enhancement in peak stress for its higher CaO content which could lead to additional cementation besides MICP. Leaching tests by toxicity characteristic leaching procedure (TCLP) and sequential extraction tests indicated that there was no potential risk to introduce fly ash into the MICP process during the soil improvement. MICP process resulted to the fraction change of trace metals which could make trace metal more stable. Microscale images at scale of 10 µm, 100 µm and 200 µm have clearly presented the precipitated CaCO3. It showed that large amount of precipitated CaCO3 coated the particle surfaces and filled the void spaces. Small particles were buried and formed aggregates. There was a highly cemented phases produced between soil particle matrix. XRD analysis also confirmed the presence of CaCO3 crystal after the MICP process. [ABSTRACT FROM AUTHOR]

A numerical model of three-dimensional (3D) ancient landslide stability analyses is by the local strength reduction method (LSRM) and the strength reduction method (SRM). A numerical model of three-dimensional (3D) ancient landslide stability analyses is by the local strength reduction method (LSRM) and the strength reduction method (SRM). However, it is obvious that the slope is instability when the sliding soil is sufficiently weakened. In this paper, the LSRM is adopted that represents the slip zone weakened by an ancient landslide in the FLAC3D. The authors have founded many unexpected results about the value of FOS, computing time and the symmetrical plane displacement by comparing the LSRM and the SRM. It is also found that the value of FOS of 3D slope with weak layer is closely related to the local load. [ABSTRACT FROM AUTHOR]

The stainless steel pickling residue (SSPR) produced from the stainless steel industries in China contains large amounts of heavy metals such as chromium (Cr) and nickel (Ni). The study found that the hexavalent chromium Cr (VI) was the primary contributor to the leaching of Cr in the toxicity character leaching test. A chemical fixation with sodium sulfide was used to treat the SSPR, and the response surface methodology (RSM) was employed to optimize the process. The results revealed that the sodium sulfide dose and curing time had significant effects on the fixation of Cr. The higher was the sodium sulfide dose, and the longer the curing time, the lower the leaching concentration of Cr would be. The water addition amount had insignificant effect when it was higher than 70%. A dose of 1.2% sodium sulfide on dry mass basis, a water addition of 90–100%, and a curing time of longer than 10 days in the open air could reduce the leaching of Cr to below the beneficial use threshold. The low chemical dose and simple procedures established in this study make this treatment method cost-effective for rendering the SSPR into a nonhazardous and useful material. [ABSTRACT FROM AUTHOR]