Due to overlying loads or groundwater extraction, the boundary stresses of in-situ aquitards are complex and variable. Consequently, the consolidation deformation caused thereby makes it challenging to accurately determine hydrogeological parameters and predict deformation using traditional methods. Complex stress boundaries impose a significant computational burden on the estimation of hydrogeological parameters. To simplify the computational complexity, this study proposes two generalization methods for complex stress boundaries: multistage constant and multistage linear loads. Based on these two methods, analytical solutions for the nonlinear consolidation deformation rate and magnitude of aquitards are derived. Through dimensionless analysis of the deformation rate, a new type-curve fitting method is proposed for estimating hydrogeological parameters; parameter inversion results are obtained by fitting the analytical model with laboratory measured data. Finally, by comparing the measured data with the predicted curve of subsequent deformation based on the inversion results, the results exhibit a good degree of fitting. The results show that the hydrogeological parameters estimated by the two generalization methods and corresponding analytical solutions proposed in this study exhibit good accuracy in predicting deformations under subsequent loading stages, directly verifying the rationality of the two generalizations and the accuracy of the analytical solutions. The proposed analytical approach enhances our understanding of the nonlinear consolidation behavior of aquitards, contributes to the development of consolidation theory, and provides practical guidance for engineering applications.

The estimation of groundwater released from aquitards is important for the groundwater resources assessment and disaster prevention. In this study, a mathematical model for water release from a nonlinear consolidated aquitard was established considering that the change of the void ratio is caused by effective stress and creep effect, and the corresponding analytical solutions for water release were derived while the water level in adjacent aquifers decreases. The analysis results utilizing the analytical solution show that, with the development of consolidation, the contribution of secondary consolidation to total consolidation continuously increases and dominates during the latter stage of consolidation, where the increase in thickness of aquitards and the decrease in consolidation coefficient postponed this stage. Based on this property, a quantitative method to calculate the completion time of primary consolidation and a new multi‐parameter inversion method for calculating hydraulic parameters and coefficient of secondary consolidation were proposed. The consolidation test of aquitard under drawdown condition was conducted to prove the practicality and accuracy of the analytical solutions and parameter inversion methods. Compared with the traditional linear consolidation theory, the estimated water release from aquitards using the proposed non‐linear analytical solution is in better agreement with experimental results. The estimated water release from aquitards without considering secondary consolidation apparently underestimated, especially during the latter stage of consolidation.

Flapping foil technology, a novel fluid energy harvesting technique based on biomimicry, has demonstrated significant application potential. This paper introduces deep learning methods and addresses the issues of low efficiency and lack of interpretability in traditional optimization designs of flapping foil energy harvesting. A serial double-module end-to-end prediction framework (CTP-DSCN) that links foil operational parameters to flow fields and performance has been developed. By optimizing the model’s hyperparameters, accurate capture and prediction of unsteady flow characteristics and system performance have been achieved. Using automatic differentiation techniques, an optimization strategy for the complex, multidimensional nonlinear flow problems of flapping foils has been established, resulting in a Pareto set of multi-objective solutions for energy harvesting power and efficiency. The study shows that, after data preprocessing and hyperparameter optimization, the end-to-end deep convolutional neural network architecture (CTP-DSCN) can simultaneously capture unsteady flow features and accurately predict system performance, with an accuracy improvement of over 50% compared to machine learning methods, and high interpretability in physical field reconstruction and parameter extrapolation. Energy harvesting efficiency has been improved to 44.27% under the optimization strategy, as well as providing technical support for the static design of flapping foils.

The soil heavy metal pollution centered on landfills was often affected by the surrounding production and life. The traceability and risk assessment of different pollution sources were used to strengthen the scientific management of landfills and surrounding soils. Through literature review, field investigation and statistical methods, the environmental risk assessment and source analysis of heavy metals in landfill soil were studied. The results showed that Cr ((chromium)), Cd (cadmium), and Pb (lead) were typical soil heavy metals in the municipal solid waste landfills (MSW) in the study area. The Nemerow index of Cr was high, and the PI value reached 9.17, which was considered as serious pollution. Cd had potential ecological risks (Er > 40), while Cd, Cu (copper) and As (arsenic) were greatly affected by parent materials. The health risk values of As and Cd in the study area (1.074E-04 and 1.366E-04) exceeded the tolerable value (10–4). Cr had high homology with Cd, Cu, Ni (nickel), and Pb, and was mainly derived from landfill and leachate leakage. Landfill, incineration plant and aquafarm were the main sources of heavy metals in this study.

The indentation caused by slip on the outer wall of tubing is a significant contributor to stress concentration and, consequently, fatigue failure in the tubing string. Through an analysis of the interaction between slips and tubing, a mathematical model to predict slip-tubing interaction and slip crushing load is formulated, accounting for external pressure, internal pressure, and axial forces. On this basis, the influence factors and influence rules of slip crushing load are studied, and three-dimensional yield surface and tri-axial stress ellipse of tubing are investigated, considering different transverse load factors and design factors. To accurately forecast the fatigue life of tubing subjected to slip indentation, two models are established: one for fatigue life prediction and the other for tubing string vibration. In order to quantitatively assess the stress concentration arising from slip indentation, a finite element model of tubing featuring slip indentation is established. Finite element analysis reveals that stress concentration and non-uniformity are evident in the vicinity of slip indentation, with their severity intensifying as the indentation depth grows. The initial step in assessing fatigue life involves fatigue life tests on tubing material subjected to varying stress levels. Subsequently, a case study is conducted and the variations of wellhead pressure and axial stress are evaluated. Fatigue life analysis reveals that the fatigue life is notably sensitive to variations in stress amplitude and slip indentation depth. An increase in the magnitude of alternating stress and the depth of slip indentation will result in a significant reduction in the fatigue lifespan. The methodologies employed in this research, along with the resulting findings, offer a robust theoretical framework and a solid practical basis for forecasting and managing stress concentration and fatigue durability in tubing affected by slip indentation.

Tunnels exhibit obvious continuous deformation during excavation and operation. This behavior is closely associated with the time-dependent behavior of rocks, which is induced by groundwater level fluctuation. This paper proposes a rheological model consisting of a Hooke elastomer, Kelvin body, and novel plastic element in series (called the HKP model) to describe the creep response of rocks with consideration to groundwater change characterized by dry–wet cycles. First, dry–wet cycle creep tests were carried out to investigate the time-dependent behavior, that is, the creep behavior of sandstone. Then, the creep equation of the viscoelastic–plastic model was derived, and the damage coefficients under the effect of dry–wet cycles and time were obtained. Finally, the HKP model was established to investigate the continuous deformation during tunnel excavation. The results reveal that dry–wet cycles have obvious effects on the physical properties and creep behavior of sandstone. The creep behavior of sandstone undergoes three stages, namely, the decaying, steady, and accelerated stages, which can be reasonably described by the proposed HKP model. Tunnels exhibit obvious creep behavior owing to excavation. The proposed model can accurately predict tunnel deformation in practice. Thus, the HKP model can help in establishing tunnel maintenance strategies to ensure long–term safety.

Geophysical flows, characterized by diverse particle-size mixtures, pose challenges for hazard risk assessment due to their anomalous fluidity and rheological behavior. This study investigates the rheological behavior of dry granular mixture flow in a flume setup using particle image velocimetry and triaxial force measurement. Key findings include a power-law relationship between the inertia value and the internal friction coefficient, affirming the applicability of the monodisperse friction model in mixed particle-size scenarios. A strong positive correlation is identified between the effective basal friction coefficient and internal friction coefficient, suggesting an influence of internal frictional properties on basal friction for granular flows on a flat surface. Additionally, positive correlations are observed between normalized stress fluctuation and both internal friction coefficient and inertia number, linking basal stress fluctuations to variations in internal frictional characteristics. These insights enhance our understanding of granular material dynamics, holding potential implications for geological disaster risk assessment.

Estimation of hydraulic parameters and groundwater depletion of aquitards is necessary to evaluate the groundwater resources and land subsidence. In this study, an analytical solution for water release from a nonlinear consolidated aquitard was derived by approximating the drawdown history as a continuous piecewise linear drawdown function (PLD) with several stages, while the water level in adjacent aquifers varies arbitrarily over time. According to dimensionless and parameter sensitivity analyses, groundwater depletion of an aquitard increases with an increase in compression index, aquitard thickness, and water drawdown rate in adjacent aquifers, decreases with an increase in initial void ratio and effective stress, and is not affected by the consolidation coefficient. In addition, we proposed a type-curve fitting method to calculate the hydraulic parameters of the aquitard under the condition of PLD in adjacent aquifers. The proposed method was applied to estimate the hydraulic parameters of aquitards at two field sites in the Yangtze River Delta in China, i.e., Changzhou and Shanghai. Results show that the compression index of the aquitards in Changzhou and Shanghai are 0.074 and 0.24, respectively, while the consolidation coefficients are 7.62 x 10-7 m2/s and 2.16 x 10-6 m2/s, respectively. The hydraulic conductivity and specific storage estimated by the proposed method are in good agreement with previous studies and the results of the geological method of Konikow and Neuzil (2007). The proposed analytical method for estimating hydraulic parameters and groundwater depletion of aquitards will contribute to the sustainable management of groundwater resources in multi-layer aquifer systems.

The consolidation of clay layers is of great significance for groundwater environmental protection, groundwater storage utilization, and land subsidence. In this study, the governing equation for the excess pore water pressure during the non-linear consolidation process of clay layers under load conditions is obtained based on the one-dimensional non-linear consolidation theory. Analytical solutions are then derived for clay layers with single or double drainage caused by the dissipation of the excess pore water pressure. With these analytical solutions, the groundwater dynamics and deformation of the clay layer are analyzed. Correspondingly, a type curve method is proposed to calculate the hydraulic parameters of the clay layer through laboratory experiments, which verifies the reliability of the analytical solutions. The study results show that the deformation of the clay layer predicted by the non-linear consolidation theory is smaller than that predicted by the linear consolidation theory. The deformation of the clay layer increases with the increase in the thickness of the clay layer, the compressive index, and the overburden load, while it decreases with the increase in the initial void ratio and the initial effective stress. The stable time, at which the consolidation of the clay layer is completed, increases with the increase in the compression index and the thickness of the clay layer, while it decreases with the increase in the initial void ratio, the initial effective stress, and the initial hydraulic conductivity. It does not vary with the load pressure. Conclusively, the deformation prediction based on the non-linear consolidation theory is more accurate and applicable to further load pressures.

Computing aquitard depletion, which is often overlooked, is of great significance for the assessment of groundwater resources and land subsidence. The issue is viewed as troublesome because of the additional computational burden, the poorly known hydrogeological parameters of the aquitard, and the lack of drawdown history in pumped aquifers. In this study, an analytical solution is derived to describe the drawdown variation in a nonlinear‐consolidated aquitard under the condition of variable drawdowns in adjacent aquifers. Based on the analytical solution, we study the characteristics of groundwater dynamics and water balance under the conditions of linearly increasing drawdown of aquifers in adjacent aquifers. In addition, we put forward a method to calculate the depletion and hydrogeological parameters of an aquitard corresponding to variable drawdowns in adjacent aquifers, applicable even when historical drawdown data are lacking. The accuracy of the method is generally very good, but results improve when the drawdown history of pumped aquifers is divided into more periods for estimation. Groundwater depletion of the aquitard increases with increasing compression index, coefficient of consolidation, thickness of aquitard, rate of drawdown change in the adjacent aquifer, while decreasing with initial void ratio, and initial effective stress. The proposed approach is demonstrated at a field site in Shanghai city of China, and it would help for the effective management of groundwater resources and estimation of the global transfer from groundwater to surface water.

Geomaterial rheology plays an important role in engineering stability and can be used to understand the deformation behavior of rocks. This study proposes a novel damage constitutive model to describe the rheological properties of rocks, which includes a Maxwell body, a Kelvin body, and a new damage-plastic element. A series of uniaxial rock creep tests were performed, and the experimental results can verify the proposed viscoelastic–plastic model. A closed-form analytical solution of surrounding rock creep in a circular tunnel is derived using the proposed model, and parametric studies are examined to determine the influence of parameters on the surrounding rock deformation. Dengjiashan tunnel in Sichuan, China is employed to verify the analytical solution. The results show that the proposed viscoelastic–plastic model well describes the entire rock creep process. The geological strength index has a significant influence on the surrounding rock deformation. The analytical results agree well with the experimental and monitoring data. The proposed analytical solution can therefore be applied to predict the creep deformation of surrounding rocks due to tunnel excavation.

农村生活垃圾的高效管理是实现乡村生态振兴和改善农村人居环境的重要基础,科学合理、便捷可行的生活垃圾处理技术评价指标体系可为农村生活垃圾处理技术的选择提供理论依据和实践指导.为此,该研究采用层次分析(AHP)法,结合现场和文献调研,构建了农村生活垃圾处理技术评价指标体系,并对各指标进行了量化.其中准则层指标权重由大到小依次为环境指标(46.38％)、经济指标(28.70％)、技术指标(24.92％),在环境指标中,三废排放对环境、社会影响程度(25.51％)的权重大于三废处理达标率(20.87％);在经济指标中,单位垃圾处理量的运行费用(20.39％)权重要明显大于单位垃圾处理量的设施投资费用(8.31％);在技术指标中,权重由大到小依次为垃圾无害化处理率(6.17％)、操作运行便捷程度(4.88％)、可处理的垃圾种类(3.36％)、垃圾资源化利用率(2.96％)、技术应用广泛度(2.77％)、工程设备验收情况(2.42％)、操作运行规范程度(2.35％).专家群体职业类别对农村生活垃圾处理技术选择的影响明显,其中行政管理专家(51.95％)和企业固废技术专家(56.69％)则更关注环境指标,高校科研院所专家(34.17％)更关注经济指标,企业固废技术专家(17.25％)对技术指标关注相对更弱.案例分析显示,生物处理得分最高(84.08),热处理得分最低(61.42),因此,在农村生活垃圾处理技术选择上,需因地制宜,宜首选生物处理技术,实现有机物的资源化利用.

Soil-like material (SLM) mined from municipal solid waste (MSW) landfills can be used as nursery cultivation soil, landfill cover, and as a building material. However, SLM utilization is restrained by heavy metal (HM) contents whose speciation and migration are influenced by their dissolved organic matter (DOM) content. Therefore, the properties of aged refuse and the correlation between DOM and HM forms were studied using samples from different types of MSW landfills. The dominant components of aged refuse were SLM (18.80%-83.51%) and plastics (11.17%-65.51%). The moisture, organic matter, and pH ranged from 29.55% to 57.92%, 15.70%-57.68%, and 7.84-8.51, respectively. The Zn content was highest (455.48-1379.27 mg/kg) in the SLM, followed by Cu (96.29-428.90 mg/kg), Cr (49.10-236.21 mg/kg), Pb (53.52-222.71 mg/kg), and Ni (20.92-39.10 mg/kg). The SLM cannot be used for agriculture because the HM contamination exceeds the multiple of 0.07-7.99. Zinc in the acid-soluble state and reducible state had the highest mobility in SLM. However, Cu and Pb, mainly in the oxidizable state, and Cr and Ni, in the oxidizable and residual states, were relatively stable. In the sanitary and simple MSW landfills, the average proportion of protein-like materials decreased from 84.44% to 82.61% and from 65.58% to 55.94%, respectively, as the landfill depth increased. Both the acid-soluble and oxidizable HM states and all forms of Zn in the SLM were significantly positively correlated with tyrosine-like materials (r = 0.58*-0.87**). Protein-like materials may enhance the mobility of HMs.

The higher education system is an important factor in measuring the education level and national strength of a country. A healthy and sustainable higher education system can effectively improve the country's competitiveness. The establishment of a complete and unified model for evaluating the pros and cons of the national higher education system is the basis for improving the level of the higher education system. In this article, we will build the relevant model in four steps. The first step is to search for documents and data, and use data on factors such as knowledge protection in multiple countries, higher education enrollment rates, education system quality, student Internet access, government education expenditures, the number of citations per paper, and the value of degrees. Build a model based on it. And standardize all data. In the second step, since the factors may have a certain correlation, the principal component analysis method is used to convert the equi-related variables into another set of unrelated variables and establish a model. The third step is to analyze the health and sustainability levels of higher education systems in Canada, France, Germany, Italy, Japan, Russia, the United Kingdom, the United States and other countries based on this model, and obtain rankings and comprehensive scores. The fourth step is to use the entropy method to calculate the specific weight of each factor. Select one of the countries to reform the most weighted factor. Import the reformed data into the model again, observe and analyze its changes.

This study investigated the morphology and potentially toxic metal concentrations of paper waste-based biochar (PB) and kitchen waste-based biochar (KB) obtained at 500 and 700 degrees C. The morphology and potentially toxic metals (Cr, Mn, Cu, Cd, Pb, Zn, Ag, and Ba) concentrations in the biochars were determined by SEM and FT-IR analysis. The Cr, Mn, Cu, and Cd concentrations in PB were low, while the Ba content was relatively high at 0.1 mg.kg(-1). An increase in the terminal temperature led to an increase in the concentrations of Fe/Mn oxide-bound potentially toxic metals of PB, and a decrease in the concentrations of organic matter-bound potentially toxic metals. The Fe/Mn oxide-bound Cr, Mn, Cu, Pb, and Zn concentrations of KB decreased with an increase in the terminal temperature. Therefore, increasing the terminal temperature could reduce the bioavailability of potentially toxic metals in PB and KB. The environmental risk of the different biochars when used for soil remediation was assessed by the potential ecological risk index (RI), and a case study of a Tibetan soil was also conducted. The potentially toxic metal concentrations leached from both PB and KB were lower than the relevant standards. The findings showed that both PB and KB can be safely used for soil remediation. (C) 2020 Elsevier Ltd. All rights reserved.

The biogas generation mechanism and its utilization potential in a novel spatiotemporally anaerobic/semi-aerobic bioreactor (STASAB) system with three activated bioreactors (C1, C2 and C3) was analyzed. Methane generation potential was obtained by measurements and estimation methods with similar values of 23.38 and 27.79 kg CH4/t waste, respectively. CH4 and CO2 production was quickly achieved in the STASAB, and the total amount of CH4 and CO2 was low due to the mixed leachate-recirculation operation process among bioreactors, which were at different stages of operation. The microbial communities in different bioreactors were diverse. The leachate-recirculation operation was a critical parameter to effectively enhance the microbial community structure in the STASAB, which can regulate CH4, CO2 and N2O production with global warming potential of 7.479 kg CO(2)e/(t.d). The STASAB had higher energy potential of 1.011 kWh/(t.d) compared with that of conventional landfills and sequentially anaerobic/semi-aerobic bioreactors. Moreover, direct electricity production in the STASAB is recommended for energy utilization with 38.38% GHG emission reduction, and with 131.43 million CNY (Chinese Yuan) benefit per year for national rural waste disposal via utilization of biogas from the STASAB for power generation. Hence, the STASAB shows a notable potential for treating domestic waste in rural areas. (C) 2020 Elsevier Ltd. All rights reserved.

生物反应器是处理农村中小型固体废物的有效技术,该研究以时空联合型厌氧-准好氧生物反应器(SASAB,Sequentially Anaerobic/Semi-Aerobic Bioreactor)为研究对象,利用16S rRNA高通量测序分析了STASAB中的微生物群落,以期为该反应器的高效运行提供理论依据.结果表明,各生物反应器处理单元中将C1、C2和C3生物反应器设为试验组,分别在第66、101和246天开始依次按SASAB操作运行的优势菌门为Proteobacteria(18.5％～26.6％)、Firmicutes(14.9％～26.6％)、Chloroflexi(6.6％～25.2％)、Bacteroidetes(8.2％～24.0％)、Actinobacteria(6.9％～13.8％).C3处理单元在厌氧阶段中的优势菌属为Lentimicrobiume、vadinBC27_wastewater-sludge_group、Treponema_2、norank_f_Synergistaceae(产甲烷菌)等.在STASAB各处理单元中发现了硝化细菌Deinococcus-Thermus以及大量的反硝化细菌norank_f_Anaerolineaceae、unclassified_o_Rhizobiales、Hyphomicrobiu、AKYG587、Bacillus、norank_f_Caldilineaceae等.Venn图与PCA分析显示C1、C2具有相似的微生物群落结构,C3中的特有菌属高于其他反应器;RDA(Redundancy Analysis)分析表明C1、C2(STASAB)中的微生物群落具有更高的稳定性,不易受到外界环境因素的影响.因此,STASAB的空间布局和运行方式能够有效发挥厌氧和准好氧生物反应器的优势,高效促进产甲烷菌、硝化菌和反硝化菌的共存和生长代谢,实现农村生活垃圾的快速降解.