According to the existing problems of liquefaction models of saturated sand that were put forward under dynamic action,on the basis of Handin-Drnevich model,a new calculating model of the dynamic constitutive relation...According to the existing problems of liquefaction models of saturated sand that were put forward under dynamic action,on the basis of Handin-Drnevich model,a new calculating model of the dynamic constitutive relation of saturated sand was put forward.The model was based on the basic hypothesis of instantaneous limit balance according to the basic principle that the stress estate is the destroyed condition was not overstepped.The calculated method of increment nonlinear was referenced and combined with the excellence of the model of distributed particles.The process of vibrating liquefaction of saturated sand was divided into some areas.And the phenomena of shearing dilatation and unloading shrink of saturated sand were considered.On above basic a new calculating constitutive relation model was proposed.There are a few parameters in the model.The physical means of the parameters are very evident and quantized.They could be obtained from the dynamic triaxial test in door.The model was contrasted and validated with the results of the dynamic triaxial test in door.The comparison of the results of the dynamic triaxial test in door and the calculating results of the model indicates that all sorts of phenomenon appearing in the process of liquefaction of saturated sand could be more perfectly reflected by the model.Especially at the initial stage of development of pore water pressure and strain of saturated sand,the results of the dynamic triaxial test in door are consistent with the calculated results of the model very much.But there is some difference between the results at the anaphase of development of pore water pressure and strain.On the path of stress,the calculating and experimenting ultimate state surfaces are almost identical.展开更多
To provide a seepage-stress coupling constitutive model that can directly describe the seepage-stress coupling relationship, a series of one-dimensional seepage-stress coupling tests on two kinds of soft rock (argilla...To provide a seepage-stress coupling constitutive model that can directly describe the seepage-stress coupling relationship, a series of one-dimensional seepage-stress coupling tests on two kinds of soft rock (argillaceous siltstone and brown mudstone) were performed by using an MTS-815.02 tri-axial rock mechanics test system, with which the stress-strain curves according to the seepage variation were obtained. Based on the experimental results and by employing Hooke's law, the formulation of the coefficient of strain-dependent permeability was presented and introduced to establish a coupling model. In addition, the mathematical expression and the incremental formulation for coupling model were advanced, in which five parameters that can be respectively determined by using the experimental results were included. The calculated results show that the proposed coupling model is capable of simulating the stress-strain relationship with considering the seepage-stress coupling in the nonlinear elastic stage of two kinds of soft rock.展开更多
The simplified analysis method based on the static equilibrium is generally adopted for raft design. The secondary stress of superstructure due to the differential settlement of the foundation is neglected, which lead...The simplified analysis method based on the static equilibrium is generally adopted for raft design. The secondary stress of superstructure due to the differential settlement of the foundation is neglected, which leads to larger support moments and longitudinal bending of raft compared with real values. The spring constitutive relation of composite foundation is obtained by the flat plate loading tests in Karst region. The interaction between the spring and the raft is equivalent to the interaction between the composite foundation and the raft. The model for superstructure-raft-composite foundation interaction analysis is thus established and the raft is designed. This method not only considers the nonlinear properties of composite foundation but also analyzes the influence of superstructure on bending moment and deformation of raft. Compared with the inverted floor method, the calculated values of moment become more reasonable and uneven settlements are considered. This can be references to the design of raft foundation in similar regions.展开更多
【目的】旨在评估集成学习神经网络模型对落叶松木质材料本构关系的拟合能力和泛化能力,为优化木质产品加工成型提出一种高效率、高精度预测材料受力变形关系的新技术方法。【方法】以落叶松木材为研究对象,结合顺纹压缩试验的标准,前...【目的】旨在评估集成学习神经网络模型对落叶松木质材料本构关系的拟合能力和泛化能力,为优化木质产品加工成型提出一种高效率、高精度预测材料受力变形关系的新技术方法。【方法】以落叶松木材为研究对象,结合顺纹压缩试验的标准,前期对试件的表征和湿度进行了处理,对落叶松木质材料5组试件进行单轴压缩试验,将试验数据作为数据源,在对其进行去噪、聚类、归一等处理的基础上,对12600组数据进行特征提取,建立了学习知识库。利用改进的CLIQUE(Clustering in QUEst)算法对知识库中的样本进行聚类分析,结合局部优化原理和集成学习组合优化理论,构建出一种基于集成学习神经网络的落叶松木质材料受压本构关系模型;然后对关系模型进行训练、学习和仿真,使模型的参数得到优化确认。【结果】1)相比于理论模型,基于集成学习神经网络的落叶松木质材料受压本构关系模型能够与试验数据之间取得更好的吻合效果,说明该模型适合用来描述落叶松木材顺纹受压的力学行为;2)基于集成学习神经网络模型学习速度快,拟合精度高,泛化能力强,可作为材料非线性本构关系的研究模型;3)从试验曲线来看,落叶松材料的抗压强度和弹性模量的变化规律符合弹性力学应力状态分析结论,可以根据本研究提出的模型来预测顺纹方向压力作用下落叶松材料的非线性应力-应变关系;4)预测结果与试验测试存在一定的偏差,可能来自试件的离散性、试件的加工误差和模型学习样本偏少等方面原因。【结论】该模型具有很高的拟合精度和较强的预测能力,可为研究木材本构关系提供一种技术与方法上的参考,对落叶松木材加工成型也有一定的指导意义。展开更多
岩石的短期和长期力学性能和变形特性对工程长期稳定与安全有着重要的影响。传统的本构模型难以统一描述不同岩石材料的短长期力学特性,而基于深度学习方法的理论可在不引入其他弹塑性参数以及本构规律的情况下预测不同岩石的力学特性...岩石的短期和长期力学性能和变形特性对工程长期稳定与安全有着重要的影响。传统的本构模型难以统一描述不同岩石材料的短长期力学特性,而基于深度学习方法的理论可在不引入其他弹塑性参数以及本构规律的情况下预测不同岩石的力学特性。长短期记忆(long short-term mernory,简称LSTM)深度学习算法适用于处理具有时间序列的数据任务,用于预测岩石短长期力学特性具有显著优势。通过引入LSTM算法,分别根据三轴压缩加载路径和应力松弛随时间变化的规律构建序列数据,建立了灰砂岩在常规三轴压缩以及应力松弛下的力学特性预测模型。与试验数据进行对比,可以证明基于深度学习的岩石短长期力学预测本构模型的准确性。为进一步提升模型工程应用价值,将LSTM本构模型嵌入到有限元法(finite element method,简称FEM)框架中进行数值实现,并应用于灰砂岩变形特性的模拟。对比结果表明,LSTM-FEM方法具有较好地预测岩石短长期变形特性的能力。展开更多
基金Project(59979001) supported by the National Natural Science Foundation of China
文摘According to the existing problems of liquefaction models of saturated sand that were put forward under dynamic action,on the basis of Handin-Drnevich model,a new calculating model of the dynamic constitutive relation of saturated sand was put forward.The model was based on the basic hypothesis of instantaneous limit balance according to the basic principle that the stress estate is the destroyed condition was not overstepped.The calculated method of increment nonlinear was referenced and combined with the excellence of the model of distributed particles.The process of vibrating liquefaction of saturated sand was divided into some areas.And the phenomena of shearing dilatation and unloading shrink of saturated sand were considered.On above basic a new calculating constitutive relation model was proposed.There are a few parameters in the model.The physical means of the parameters are very evident and quantized.They could be obtained from the dynamic triaxial test in door.The model was contrasted and validated with the results of the dynamic triaxial test in door.The comparison of the results of the dynamic triaxial test in door and the calculating results of the model indicates that all sorts of phenomenon appearing in the process of liquefaction of saturated sand could be more perfectly reflected by the model.Especially at the initial stage of development of pore water pressure and strain of saturated sand,the results of the dynamic triaxial test in door are consistent with the calculated results of the model very much.But there is some difference between the results at the anaphase of development of pore water pressure and strain.On the path of stress,the calculating and experimenting ultimate state surfaces are almost identical.
基金Projects(50378069, 50639090) supported by the National Natural Science Foundation of ChinaProject(50639090) supported by the Joint Fund of Yalong River Hydropower Development, China
文摘To provide a seepage-stress coupling constitutive model that can directly describe the seepage-stress coupling relationship, a series of one-dimensional seepage-stress coupling tests on two kinds of soft rock (argillaceous siltstone and brown mudstone) were performed by using an MTS-815.02 tri-axial rock mechanics test system, with which the stress-strain curves according to the seepage variation were obtained. Based on the experimental results and by employing Hooke's law, the formulation of the coefficient of strain-dependent permeability was presented and introduced to establish a coupling model. In addition, the mathematical expression and the incremental formulation for coupling model were advanced, in which five parameters that can be respectively determined by using the experimental results were included. The calculated results show that the proposed coupling model is capable of simulating the stress-strain relationship with considering the seepage-stress coupling in the nonlinear elastic stage of two kinds of soft rock.
基金Project(2011ZA05) supported by State Key Laboratory of Subtropical Building Science in South China University of Technology, China
文摘The simplified analysis method based on the static equilibrium is generally adopted for raft design. The secondary stress of superstructure due to the differential settlement of the foundation is neglected, which leads to larger support moments and longitudinal bending of raft compared with real values. The spring constitutive relation of composite foundation is obtained by the flat plate loading tests in Karst region. The interaction between the spring and the raft is equivalent to the interaction between the composite foundation and the raft. The model for superstructure-raft-composite foundation interaction analysis is thus established and the raft is designed. This method not only considers the nonlinear properties of composite foundation but also analyzes the influence of superstructure on bending moment and deformation of raft. Compared with the inverted floor method, the calculated values of moment become more reasonable and uneven settlements are considered. This can be references to the design of raft foundation in similar regions.
文摘【目的】旨在评估集成学习神经网络模型对落叶松木质材料本构关系的拟合能力和泛化能力,为优化木质产品加工成型提出一种高效率、高精度预测材料受力变形关系的新技术方法。【方法】以落叶松木材为研究对象,结合顺纹压缩试验的标准,前期对试件的表征和湿度进行了处理,对落叶松木质材料5组试件进行单轴压缩试验,将试验数据作为数据源,在对其进行去噪、聚类、归一等处理的基础上,对12600组数据进行特征提取,建立了学习知识库。利用改进的CLIQUE(Clustering in QUEst)算法对知识库中的样本进行聚类分析,结合局部优化原理和集成学习组合优化理论,构建出一种基于集成学习神经网络的落叶松木质材料受压本构关系模型;然后对关系模型进行训练、学习和仿真,使模型的参数得到优化确认。【结果】1)相比于理论模型,基于集成学习神经网络的落叶松木质材料受压本构关系模型能够与试验数据之间取得更好的吻合效果,说明该模型适合用来描述落叶松木材顺纹受压的力学行为;2)基于集成学习神经网络模型学习速度快,拟合精度高,泛化能力强,可作为材料非线性本构关系的研究模型;3)从试验曲线来看,落叶松材料的抗压强度和弹性模量的变化规律符合弹性力学应力状态分析结论,可以根据本研究提出的模型来预测顺纹方向压力作用下落叶松材料的非线性应力-应变关系;4)预测结果与试验测试存在一定的偏差,可能来自试件的离散性、试件的加工误差和模型学习样本偏少等方面原因。【结论】该模型具有很高的拟合精度和较强的预测能力,可为研究木材本构关系提供一种技术与方法上的参考,对落叶松木材加工成型也有一定的指导意义。
文摘岩石的短期和长期力学性能和变形特性对工程长期稳定与安全有着重要的影响。传统的本构模型难以统一描述不同岩石材料的短长期力学特性,而基于深度学习方法的理论可在不引入其他弹塑性参数以及本构规律的情况下预测不同岩石的力学特性。长短期记忆(long short-term mernory,简称LSTM)深度学习算法适用于处理具有时间序列的数据任务,用于预测岩石短长期力学特性具有显著优势。通过引入LSTM算法,分别根据三轴压缩加载路径和应力松弛随时间变化的规律构建序列数据,建立了灰砂岩在常规三轴压缩以及应力松弛下的力学特性预测模型。与试验数据进行对比,可以证明基于深度学习的岩石短长期力学预测本构模型的准确性。为进一步提升模型工程应用价值,将LSTM本构模型嵌入到有限元法(finite element method,简称FEM)框架中进行数值实现,并应用于灰砂岩变形特性的模拟。对比结果表明,LSTM-FEM方法具有较好地预测岩石短长期变形特性的能力。
