Soil-rock mixture(S-RM)is a widely distributed geotechnical medium composed of "soil" and "rock block" different both in size and strength. Internal rock blocks form special and variable meso-struc...Soil-rock mixture(S-RM)is a widely distributed geotechnical medium composed of "soil" and "rock block" different both in size and strength. Internal rock blocks form special and variable meso-structural characteristics of S-RM. The objective of this work was to study the control mechanism of meso-structural characteristics on mechanical properties of S-RM. For S-RM containing randomly generated polygonal rock blocks, a series of biaxial tests based on DEM were conducted. On the basis of research on the effects of rock blocks' breakability and sample lateral boundary type(rigid, flexible) on macroscopic mechanical behavior of S-RM, an expanded Mohr-Coulomb criterion in power function form was proposed to represent the strength envelop. At the mesoscopic level, the variations of meso-structure such as rotation of rock block, and the formation mechanism and evolution process of the shear band during tests were investigated. The results show that for S-RM with a high content of rock block, translation, rotating and breakage of rock blocks have crucial effects on mechanical behavior of S-RM. The formation and location of the shear band inside S-RM sample are also controlled by breakability and arrangement of rock blocks.展开更多
A new and simple microwave-assisted alkaline degradation （MAAD） method for the elimination of organoehlorine-pesticide interference on the determination of polychlorinated biphenyls （PCBs） in soil by GC is present...A new and simple microwave-assisted alkaline degradation （MAAD） method for the elimination of organoehlorine-pesticide interference on the determination of polychlorinated biphenyls （PCBs） in soil by GC is presented. Under the optimal conditions, the interference of α- HCH, β- HCH, γ -HCH,δ -HCH, o. p＇ - DDT, p. p＇ - DDD and p. p＇ - DDT could be eliminated completely, and p. p＇ - DDE, Aldrin and Dieldrin could be partially eliminated; however, Dieldrin could be completely eliminated by using concentrated sulphurie acid. The method was evaluated by analyzing the spiked-soil sample. The mean recovery obtained was 84. 1% and the Relative Standard Deviation （RSD） was 2. 7%. Experimental results also indicate that the degradation of the interference and the extraction of the target analytes, PCBs, could be carried out simuhaneously. Compared with the traditional methods, the MAAD method is a rapid, efficient and solvent-saving method,展开更多
With the increasing development of Brazil in recent years, major engineering construction works have been designed and built, partieutarly those involving large volumes of mass concrete, such as in the case of dams. M...With the increasing development of Brazil in recent years, major engineering construction works have been designed and built, partieutarly those involving large volumes of mass concrete, such as in the case of dams. Mass concrete, due to its large size and volume, presents a considerable temperature rise caused by cement grain hydration. This temperature rise can be sufficient to cause concrete crack and/or cracking, which may lead to serious problems. In this paper, we sought to study heat generation and temperature field in mass concrete through ANSYS software, which uses finite element method to analyze the problem. This program allows temperatures to be checked for different concrete ages. With that, it is possible to evaluate the temperatures obtained and the factors influencing the results in a short period of time at a low cost. With the help of the software, it is possible to check the temperatures for different concrete properties by analyzing them on different concreting days. Therefore, it was possible to establish that the properties of the concrete directly influence the temperature evolution phenomenon.展开更多
This paper is concerned with the stability analysis of reinforced slopes.A new approach based on the limit equilibrium principle is proposed to evaluate the stability of the reinforced slopes.The effect of reinforceme...This paper is concerned with the stability analysis of reinforced slopes.A new approach based on the limit equilibrium principle is proposed to evaluate the stability of the reinforced slopes.The effect of reinforcement is modeled as an equivalent restoring force acting the bottom of the slice and added into the general limit equilibrium(GLE) method.The equations of force and moment equilibrium of the slice are derived and corresponding iterative solution methods are provided.The new method can satisfy both the force and the moment equilibrium and be applicable to the critical failure surface of arbitrary form.Furthermore,the results predicted by the proposed method are compared with the calculation examples of other researchers and the centrifuge model test results to validate its correctness and effectiveness.展开更多
基金Projects(51323014,51479095)supported by the National Natural Science Foundation of ChinaProject(20111081125)supported by Independent Research Plan of Tsinghua University,ChinaProject(2013-KY-4)supported by the State Key Laboratory of Hydroscience and Engineering Project,China
文摘Soil-rock mixture(S-RM)is a widely distributed geotechnical medium composed of "soil" and "rock block" different both in size and strength. Internal rock blocks form special and variable meso-structural characteristics of S-RM. The objective of this work was to study the control mechanism of meso-structural characteristics on mechanical properties of S-RM. For S-RM containing randomly generated polygonal rock blocks, a series of biaxial tests based on DEM were conducted. On the basis of research on the effects of rock blocks' breakability and sample lateral boundary type(rigid, flexible) on macroscopic mechanical behavior of S-RM, an expanded Mohr-Coulomb criterion in power function form was proposed to represent the strength envelop. At the mesoscopic level, the variations of meso-structure such as rotation of rock block, and the formation mechanism and evolution process of the shear band during tests were investigated. The results show that for S-RM with a high content of rock block, translation, rotating and breakage of rock blocks have crucial effects on mechanical behavior of S-RM. The formation and location of the shear band inside S-RM sample are also controlled by breakability and arrangement of rock blocks.
基金Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholar State Education Ministry (Grant No.415409) and the Scien-tific Research Foundation for Doctors, Guangdong Natural Science Foundation (Grant No.974078).
文摘A new and simple microwave-assisted alkaline degradation （MAAD） method for the elimination of organoehlorine-pesticide interference on the determination of polychlorinated biphenyls （PCBs） in soil by GC is presented. Under the optimal conditions, the interference of α- HCH, β- HCH, γ -HCH,δ -HCH, o. p＇ - DDT, p. p＇ - DDD and p. p＇ - DDT could be eliminated completely, and p. p＇ - DDE, Aldrin and Dieldrin could be partially eliminated; however, Dieldrin could be completely eliminated by using concentrated sulphurie acid. The method was evaluated by analyzing the spiked-soil sample. The mean recovery obtained was 84. 1% and the Relative Standard Deviation （RSD） was 2. 7%. Experimental results also indicate that the degradation of the interference and the extraction of the target analytes, PCBs, could be carried out simuhaneously. Compared with the traditional methods, the MAAD method is a rapid, efficient and solvent-saving method,
文摘With the increasing development of Brazil in recent years, major engineering construction works have been designed and built, partieutarly those involving large volumes of mass concrete, such as in the case of dams. Mass concrete, due to its large size and volume, presents a considerable temperature rise caused by cement grain hydration. This temperature rise can be sufficient to cause concrete crack and/or cracking, which may lead to serious problems. In this paper, we sought to study heat generation and temperature field in mass concrete through ANSYS software, which uses finite element method to analyze the problem. This program allows temperatures to be checked for different concrete ages. With that, it is possible to evaluate the temperatures obtained and the factors influencing the results in a short period of time at a low cost. With the help of the software, it is possible to check the temperatures for different concrete properties by analyzing them on different concreting days. Therefore, it was possible to establish that the properties of the concrete directly influence the temperature evolution phenomenon.
基金funded by the Key Industrial Science and Technology Project of Shaanxi Province(No.2015GY149)the Scientific Project funded by the Ministry of Housing and Urban-Rural Development of the People’s Republic of China Council(No.2015-K2-008)
文摘This paper is concerned with the stability analysis of reinforced slopes.A new approach based on the limit equilibrium principle is proposed to evaluate the stability of the reinforced slopes.The effect of reinforcement is modeled as an equivalent restoring force acting the bottom of the slice and added into the general limit equilibrium(GLE) method.The equations of force and moment equilibrium of the slice are derived and corresponding iterative solution methods are provided.The new method can satisfy both the force and the moment equilibrium and be applicable to the critical failure surface of arbitrary form.Furthermore,the results predicted by the proposed method are compared with the calculation examples of other researchers and the centrifuge model test results to validate its correctness and effectiveness.
