Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale m...Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale model test of sand-flow method. The real-time data of sand-deposit height and radius were obtained by the self-developed sand-deposit detectors. The test results show that the detecting method is simple and has high precision. In the use of sand-flow method, the sand-carrying capability of fluid is limited, and sand particles are all transported to the sand-deposit periphery through crater, gap and chutes after the sand deposit formed. The diffusion range of the particles outside the sand-deposit does not exceed 2.0 m. Severe sorting of sand particles is not observed because of the unique oblique-layered depositing process. The temporal and spatial distributions of gap and chutes directly affect the sand-deposit expansion, and the expansion trend of the average sand-deposit radius accords with quadratic time-history curve.展开更多
The objective of this work is to model the microstructure of asphalt mixture and build virtual test for asphalt mixture by using Particle Flow Code in three dimensions(PFC^(3D))based on three-dimensional discrete elem...The objective of this work is to model the microstructure of asphalt mixture and build virtual test for asphalt mixture by using Particle Flow Code in three dimensions(PFC^(3D))based on three-dimensional discrete element method.A randomly generating algorithm was proposed to capture the three-dimensional irregular shape of coarse aggregate.And then,modeling algorithm and method for graded aggregates were built.Based on the combination of modeling of coarse aggregates,asphalt mastic and air voids,three-dimensional virtual sample of asphalt mixture was modeled by using PFC^(3D).Virtual tests for penetration test of aggregate and uniaxial creep test of asphalt mixture were built and conducted by using PFC^(3D).By comparison of the testing results between virtual tests and actual laboratory tests,the validity of the microstructure modeling and virtual test built in this study was verified.Additionally,compared with laboratory test,the virtual test is easier to conduct and has less variability.It is proved that microstructure modeling and virtual test based on three-dimensional discrete element method is a promising way to conduct research of asphalt mixture.展开更多
Employing an ideal elasto-plastic model,the typically used strength reduction method reduced the strength of all soil elements of a slope.Therefore,this method was called the global strength reduction method(GSRM).How...Employing an ideal elasto-plastic model,the typically used strength reduction method reduced the strength of all soil elements of a slope.Therefore,this method was called the global strength reduction method(GSRM).However,the deformation field obtained by GSRM could not reflect the real deformation of a slope when the slope became unstable.For most slopes,failure occurs once the strength of some regional soil is sufficiently weakened; thus,the local strength reduction method(LSRM)was proposed to analyze slope stability.In contrast with GSRM,LSRM only reduces the strength of local soil,while the strength of other soil remains unchanged.Therefore,deformation by LSRM is more reasonable than that by GSRM.In addition,the accuracy of the slope's deformation depends on the constitutive model to a large degree,and the variable-modulus elasto-plastic model was thus adopted.This constitutive model was an improvement of the Duncan–Chang model,which modified soil's deformation modulus according to stress level,and it thus better reflected the plastic feature of soil.Most importantly,the parameters of the variable-modulus elasto-plastic model could be determined through in-situ tests,and parameters determination by plate loading test and pressuremeter test were introduced.Therefore,it is easy to put this model into practice.Finally,LSRM and the variable-modulus elasto-plastic model were used to analyze Egongdai ancient landslide.Safety factor,deformation field,and optimal reinforcement measures for Egongdai ancient landslide were obtained based on the proposed method.展开更多
Series of testing on coarse grained soils were carried out with a true triaxial testing apparatus.The loads were applied from the major principal and minor principal directions,respectively,to simulate the constructio...Series of testing on coarse grained soils were carried out with a true triaxial testing apparatus.The loads were applied from the major principal and minor principal directions,respectively,to simulate the construction and water impounding process of a rock fill dam.The stress and strain relationships induced by the different loading methods were investigated.A remarkable stress-induced anisotropy under complex stress state was observed.Contrary to popular assumptions in traditional numerical analysis and constitutive models,it was found that different elastic modulus and Poisson ratio exist in different principal directions in rock fill dams.From the testing results,an anisotropic constitutive model based on Duncan-Chang nonlinear model is presented to overcome the limitations of axi-symmetric assumptions in conventional triaxial experiments and constitutive models.Both models were then applied in FEM analysis of an under-construction earth core high rock soil filled dam with the focus on hydraulic fracturing.The study reveals the major biases that exist when numerical analysis and constitutive models do not give serious consideration to the intermediate principal stress and anisotropy effects in soil rock built structures.展开更多
电子轰击有源像素传感器(electron bombardment active pixel sensor,EBAPS)的光响应非均匀性是指EBAPS中光电阴极被均匀光源照射时,不同像素输出灰度不一致的现象,尤其是在低光环境下,图像的非均匀性会使细节识别变得困难,影响后续图...电子轰击有源像素传感器(electron bombardment active pixel sensor,EBAPS)的光响应非均匀性是指EBAPS中光电阴极被均匀光源照射时,不同像素输出灰度不一致的现象,尤其是在低光环境下,图像的非均匀性会使细节识别变得困难,影响后续图像处理和分析的准确性。光响应非均匀性主要由光电阴极不同区域对光响应的差异、电子敏感互补金属氧化物半导体不同区域的电子倍增特性差异、各像素间对同一激励的响应差异以及读出电路中传输信道的差异性等因素导致。针对EBAPS的非均匀性问题,提出了一种基于EBAPS光电阴极响应、电子倍增以及像素响应非均匀性协同适配的测试方法。实验结果表明,该方法能够有效评价EBAPS的非均匀性,并且能够对器件的测试筛选和算法校正起到指导作用。展开更多
基金Project(51108190) supported by the National Natural Science Foundation of ChinaProject(2012ZC27) supported by the Independence Research Subject from State Key Laboratory of Subtropical Building Science,ChinaProject(GTCC 2008-253) supported by the Research Subject from Guangzhou City,China
文摘Against the background of the sand-flow foundation treatment engineering of Guangzhou Zhoutouzui variable cross-section immersed tunnel, a kind of sand deposit-detecting method was devised on the basis of full-scale model test of sand-flow method. The real-time data of sand-deposit height and radius were obtained by the self-developed sand-deposit detectors. The test results show that the detecting method is simple and has high precision. In the use of sand-flow method, the sand-carrying capability of fluid is limited, and sand particles are all transported to the sand-deposit periphery through crater, gap and chutes after the sand deposit formed. The diffusion range of the particles outside the sand-deposit does not exceed 2.0 m. Severe sorting of sand particles is not observed because of the unique oblique-layered depositing process. The temporal and spatial distributions of gap and chutes directly affect the sand-deposit expansion, and the expansion trend of the average sand-deposit radius accords with quadratic time-history curve.
基金Project(51378006) supported by National Natural Science Foundation of ChinaProject(141076) supported by Huoyingdong Foundation of the Ministry of Education of China+1 种基金Project(2242015R30027) supported by Excellent Young Teacher Program of Southeast University,ChinaProject(BK20140109) supported by the Natural Science Foundation of Jiangsu Province,China
文摘The objective of this work is to model the microstructure of asphalt mixture and build virtual test for asphalt mixture by using Particle Flow Code in three dimensions(PFC^(3D))based on three-dimensional discrete element method.A randomly generating algorithm was proposed to capture the three-dimensional irregular shape of coarse aggregate.And then,modeling algorithm and method for graded aggregates were built.Based on the combination of modeling of coarse aggregates,asphalt mastic and air voids,three-dimensional virtual sample of asphalt mixture was modeled by using PFC^(3D).Virtual tests for penetration test of aggregate and uniaxial creep test of asphalt mixture were built and conducted by using PFC^(3D).By comparison of the testing results between virtual tests and actual laboratory tests,the validity of the microstructure modeling and virtual test built in this study was verified.Additionally,compared with laboratory test,the virtual test is easier to conduct and has less variability.It is proved that microstructure modeling and virtual test based on three-dimensional discrete element method is a promising way to conduct research of asphalt mixture.
基金Project([2005]205)supported by the Science and Technology Planning Project of Water Resources Department of Guangdong Province,ChinaProject(2012-7)supported by Guangdong Bureau of Highway Administration,ChinaProject(2012210020203)supported by the Fundamental Research Funds for the Central Universities,China
文摘Employing an ideal elasto-plastic model,the typically used strength reduction method reduced the strength of all soil elements of a slope.Therefore,this method was called the global strength reduction method(GSRM).However,the deformation field obtained by GSRM could not reflect the real deformation of a slope when the slope became unstable.For most slopes,failure occurs once the strength of some regional soil is sufficiently weakened; thus,the local strength reduction method(LSRM)was proposed to analyze slope stability.In contrast with GSRM,LSRM only reduces the strength of local soil,while the strength of other soil remains unchanged.Therefore,deformation by LSRM is more reasonable than that by GSRM.In addition,the accuracy of the slope's deformation depends on the constitutive model to a large degree,and the variable-modulus elasto-plastic model was thus adopted.This constitutive model was an improvement of the Duncan–Chang model,which modified soil's deformation modulus according to stress level,and it thus better reflected the plastic feature of soil.Most importantly,the parameters of the variable-modulus elasto-plastic model could be determined through in-situ tests,and parameters determination by plate loading test and pressuremeter test were introduced.Therefore,it is easy to put this model into practice.Finally,LSRM and the variable-modulus elasto-plastic model were used to analyze Egongdai ancient landslide.Safety factor,deformation field,and optimal reinforcement measures for Egongdai ancient landslide were obtained based on the proposed method.
基金Project(50809023)supported by the National Natural Science Foundation of ChinaProject(2015B17714)supported by the Fundamental Research Funds for Central Universities,China
文摘Series of testing on coarse grained soils were carried out with a true triaxial testing apparatus.The loads were applied from the major principal and minor principal directions,respectively,to simulate the construction and water impounding process of a rock fill dam.The stress and strain relationships induced by the different loading methods were investigated.A remarkable stress-induced anisotropy under complex stress state was observed.Contrary to popular assumptions in traditional numerical analysis and constitutive models,it was found that different elastic modulus and Poisson ratio exist in different principal directions in rock fill dams.From the testing results,an anisotropic constitutive model based on Duncan-Chang nonlinear model is presented to overcome the limitations of axi-symmetric assumptions in conventional triaxial experiments and constitutive models.Both models were then applied in FEM analysis of an under-construction earth core high rock soil filled dam with the focus on hydraulic fracturing.The study reveals the major biases that exist when numerical analysis and constitutive models do not give serious consideration to the intermediate principal stress and anisotropy effects in soil rock built structures.
文摘电子轰击有源像素传感器(electron bombardment active pixel sensor,EBAPS)的光响应非均匀性是指EBAPS中光电阴极被均匀光源照射时,不同像素输出灰度不一致的现象,尤其是在低光环境下,图像的非均匀性会使细节识别变得困难,影响后续图像处理和分析的准确性。光响应非均匀性主要由光电阴极不同区域对光响应的差异、电子敏感互补金属氧化物半导体不同区域的电子倍增特性差异、各像素间对同一激励的响应差异以及读出电路中传输信道的差异性等因素导致。针对EBAPS的非均匀性问题,提出了一种基于EBAPS光电阴极响应、电子倍增以及像素响应非均匀性协同适配的测试方法。实验结果表明,该方法能够有效评价EBAPS的非均匀性,并且能够对器件的测试筛选和算法校正起到指导作用。
