摘要：
VOCs are the major harmful pollutants released from MSW landfills, which are toxicity to human health. In order to in-situ biodegradation of VOCs released from landfill, two novel laboratory-scale biocovers, including waste-char obtained from MSW pyrolysis (WC), and sewage sludge modified the WC (SWC), are used to degradate VOCs. The removal performances of VOCs as well as the bacterial community in the WC and SWC are investigated in a simulated landfill systems with the contrast experiment of a landfill cover soil (LCS) for 60 days. Meanwhile, the adsorption-biodegradation of VOCs model compounds over the LCS, WC, and SWC are also tested in fixed-bed adsorption reactor and in-situ FTIR. The VOCs removal efficiencies by the SWC are maintained above 85% for a long-term, much higher than that of the LCS and WC. The higher removal efficiencies and long-term stability for VOCs degradation in SWC are attributed to a strongly positive synergistic between adsorption and biodegradation that the gaseous VOCs released from MSW is effectively adsorbed by the SWC due to its higher VOCs adsorption capacity, and then the adsorbed-VOCs is converted into CO(2 )and H2O by the microorganisms that consuming the adsorbed-VOCs as energy and carbon sources. Subsequently, the decrease of the adsorbed-VOCs in SWC would also promote the transformation of the gaseous VOCs into the adsorbed VOCs and accelerate the growth of microorganisms by taking the adsorbed-VOCs as the energy and carbon source, resulted in a higher adsorption rate and degradation rate for VOCs. (C) 2020 Published by Elsevier Ltd.
摘要：
This study focused on the permeability and structural evolution of impeded soil layers in landfill. A series of laboratory tests including a permeability test, X-ray diffraction, nuclear magnetic resonance, scanning electron microscopy, and laser particle size tests were conducted to analyze the permeability and microstructure characteristics of undisturbed silty clay polluted by landfill leachate. The hydraulic conductivities increased with time in the first 108 h. After 108 h, the hydraulic conductivities of undisturbed silty clay polluted by landfill leachate decreased. After 205 h, the changes in the hydraulic conductivity stabilized, and the hydraulic conductivity decreased with the increase of the concentration of leachate. The volume fractions of inter-particle and intra-aggregate pores were much higher than those of other pores. The optimal radius decreased as the concentration of leachate increased. The blockage of the pore channel and weakened permeability was caused by solid matter interception by the porous medium. As the height of the specimen increased, the volume fraction of coarse grain changed rapidly and sharply, and the volume fraction of fine grain changed slowly. The average particle size increased with increased specimen height and decreased as the leachate concentration increased. A comprehensive structural parameter (zeta) of undisturbed silty clay polluted by landfill leachate was obtained based on the test results. The equation of comprehensive structural parameter zeta of undisturbed silty clay polluted by leachate was established. These results can provide fundamental data for evaluating the stability of the underlying stratum of landfill sites.
期刊：
Bulletin of Engineering Geology and the Environment,2019年78(6):4611-4622 ISSN：1435-9529
通讯作者：
Lu, Haijun
作者机构：
[Lu, Haijun; Xu, Shicheng; Li, Jixiang] Wuhan Polytech Univ, Sch Civil Engn & Architecture, Wuhan 430023, Hubei, Peoples R China.;[Lu, Haijun] Chinese Acad Sci, Inst Rock & Soil Mech, State Key Lab Geomech & Geotech Engn, Wuhan 430071, Peoples R China.;[Liu, Junzhu] Beijing Geo & Inv Engn Inst, Beijing 100083, Peoples R China.
通讯机构：
[Lu, Haijun] W;[Lu, Haijun] C;Wuhan Polytech Univ, Sch Civil Engn & Architecture, Wuhan 430023, Hubei, Peoples R China.;Chinese Acad Sci, Inst Rock & Soil Mech, State Key Lab Geomech & Geotech Engn, Wuhan 430071, Peoples R China.
关键词：
Structured clay;Landfill leachate;Triaxial shear test;Microstructure;Particle distribution
摘要：
City solid waste stock has exceeded 8 billion tons in China, and the output and coverage area of solid waste are increasing daily. Landfill leachate can be generated during biodegradation of disposed and stored solid waste. Leachate contains high concentrations of organic mixtures and heavy metal ions. Natural undisturbed soil has high anti-seepage capacity and its permeability coefficient is less than 1 x 10(-7) cm/s in underlying stratum, which can delay leachate contamination of the environment surrounding a landfill site. However, undisturbed soil exhibits certain structural characteristics. After long-term leachate corrosion, leachate leakage will inevitably influence the stability of stratum underlying a landfill. In this study, the mechanical characteristics of undisturbed clay under the actions of landfill leachate and stress were analyzed via a consolidated-undrained triaxial shear test. Comprehensive microstructure laboratory tests, including X-ray diffraction, scanning electron microscopy, and laser particle size tests, were performed to determine at different times the microstructure of undisturbed clay due to corrosion by landfill leachate. Experimental results indicate the strength and microstructural evolution of structured clay under the actions of landfill leachate and stress. The research results are helpful for evaluating the safety and predicting the stability of a landfill's underlying stratum.
摘要：
To investigate the shear strength and microstructure of undisturbed loess polluted by landfill leachate, a series of laboratory tests were carried out to determine the shear strength, mineral composition, surface morphology, particle size distribution and pore characteristics of the loess. The stress-strain curve of undisturbed soil polluted by landfill leachate showed typical strain-softening behavior. The deviatoric stress, cohesion and angle of shearing resistance of undisturbed soil decreased at increased landfill leachate concentrations, decreased by 31.03%, 30.01%, respectively. But pore water pressure was positively related to leachate concentrations. The content of primary minerals remained stable, and the content of montmorillonite and illite decreased with increased leachate concentration, reduced by 26.02%, 23.93%, respectively. Soil structure changed into an unstable honeycomb structure when the leachate concentration increased. Moreover, the average particle size decreased by 62.1%, and the specific surface area increased and then stabilized at 500 similar to 650 m(2)/kg. The soil particles became nonuniform and porous and their sizes gradually decreased. The pore radius of soil mainly ranged from 0.02 mu m to 1 mu m. The maximum radius and optimal radius of the pore increased when the leachate concentrations increased.
摘要：
In order to reasonably predict failure law of compacted clay presented in landfill leachate as well as help provide theoretical basis for curbing and restoration of contaminated soil, triaxial shear, SEM, XRD and laser particle size tests were used to determine strength and microstructure of compacted clay presented in landfill leachate in this paper. The results show that when the leachate concentration was low, the stress-strain curve of compacted clay belonged to typical strain-softening behavior. With the increase of leachate concentration, the stress-strain curve of soil began to show typical strain-hardening behavior. The concentration of leachate was negatively related to the cohesion and internal friction angle of soil sample. In the aspect of soil microstructure, with the increase of leachate concentration, a series of microstructural changes, such as a decrease of secondary minerals, an increase of pore, the overhead pores developed into cracks and so on, had result in a decrease of the strength of compacted clay. The particle size curve of compacted clay presented in landfill leachate was about single peak curve and the value of D-v(50) tend to stable.
作者机构：
[蔡光华; 刘松玉] School of Transportation, Southeast University, Nanjing;210096, China;[陆海军] School of Civil Engineering and Architecture, Wuhan Polytechnic University, Wuhan;410023, China;[蔡光华; 刘松玉] 210096, China
通讯机构：
[Cai, G.-H.] S;School of Transportation, Southeast University, Nanjing, China
摘要：
Suction-controlled triaxial tests have been used extensively to characterize unsaturated soils. However, this type of tests requires sophisticated and therefore expensive equipment and is very time-consuming. These limitations have been the main obstacles for research, dissemination, and implementation of unsaturated soil mechanics in engineering practice. Compared with the suction-controlled triaxial test apparatus, an oedometer for saturated soils is much simpler. It is 300 to 400 times more efficient to run a constant water content oedometer test for unsaturated soils than a suction-controlled triaxial test. The major disadvantage of the constant water content oedometer test is that its stress path is difficult to analyze and no method is available to take advantage of the test results for constitutive modeling purposes. In this paper, a conventional oedometer for saturated soils was modified to characterize unsaturated soils under constant water content compression. An analysis method was also developed to use the results directly from constant water content oedometer tests for constitutive modeling. A series of constant water content oedometer tests was used to demonstrate the application of the proposed method from which the capability and the effectiveness of the proposed developments were evaluated. With developments in equipment and analysis, it is now possible to characterize unsaturated soils rapidly in a simple and efficient way.
作者机构：
[朱登峰; 李继祥; 杨建康] Institute of Poromechanics, Wuhan Polytechnic University, Wuhan, 430023, China;Institute of Geotechnical Engineering, School of Civil Engineering, Dalian University of Technology, Dalian, 116024, China;[陆海军] Institute of Poromechanics, Wuhan Polytechnic University, Wuhan, 430023, China, Institute of Geotechnical Engineering, School of Civil Engineering, Dalian University of Technology, Dalian, 116024, China
通讯机构：
[Lu, H.-J.] I;Institute of Poromechanics, Wuhan Polytechnic University, Wuhan, China
作者机构：
[陆海军; 董祎挈; 汪为巍; 张芊] Institute of Poromechanics, Wuhan Polytechnic University, Wuhan, 430023, China;[董祎挈] School of Resource and Environmental Science, Wuhan University, Wuhan, 430072, China;[蔡光华] Institute of Geotechnical Engineering, School of Transportation, Southeast University, Nanjing, 210096, China
通讯机构：
[Lu, H.] I;Institute of Poromechanics, Wuhan Polytechnic University, Wuhan, China
作者机构：
[李继祥; 张雄; 张芊] Institute of Poromechanics, Wuhan Polytechnic University, Wuhan, 430023, China;Institute of Geotechnical Engineering, School of Civil Engineering, Dalian University of Technology, Dalian, 116024, China;[陆海军] Institute of Poromechanics, Wuhan Polytechnic University, Wuhan, 430023, China, Institute of Geotechnical Engineering, School of Civil Engineering, Dalian University of Technology, Dalian, 116024, China
通讯机构：
[Lu, H.-J.] I;Institute of Poromechanics, Wuhan Polytechnic University, Wuhan, China
摘要：
In order to research the corrosive state of landfill liner system, which affected by landfill leachate, and explore its strength and microstructure properties, contacting reaction between landfill leachate and compacted clay landfill liner system was simulated. Then, clay samples of different layers were investigated by unconfined compressive testing, shear testing and static nitrogen adsorption testing. The results showed that corrosion degree of clay samples caused by landfill leachate increased with the decrease of deepness of clay. And the maximum unconfined compressive strength (UCS) decreased obviously along with the shear strength. The UCS at 10cm was 53.1% that of layer at 50cm and the shear strength was 40.4∼62.4% at 10cm that of 50cm. The static nitrogen adsorption testing showed that the shape of clay particle was bottleneck like, and with the decrease of the depth of clay, there was a decrease in the number of micropores whose size was no smaller than 6nm. And the number of pores which was between 2nm and 5nm increased. In addition, there also appeared micropore which was smaller than 2nm. And the average pore size was decreased from 5.083nm at 50cm to 3.768nm at 10cm.<br/>
