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非饱和粉砂临界状态的试验研究

岩土工程学报 2018年第S1期40卷 8-15页

作者：蔡国庆 asreazad saman 刘超赵成刚北京交通大学城市地下工程教育部重点实验室北京交通大学土木建筑工程学院天津市市政工程设计研究院桂林理工大学土木与建筑工程学院

非饱和土临界状态给出了土变形过程的终点,对于分析土的基本力学性质和建立相应的本构模型十分重要。以非饱和粉砂为研究对象,利用非饱和土双压力室三轴试验系统(GDS)开展相关试验研究,对不同干密度粉砂在不同净应力和吸力条件下剪切至... 详细信息

非饱和土临界状态给出了土变形过程的终点,对于分析土的基本力学性质和建立相应的本构模型十分重要。以非饱和粉砂为研究对象,利用非饱和土双压力室三轴试验系统(GDS)开展相关试验研究,对不同干密度粉砂在不同净应力和吸力条件下剪切至临界状态过程中,分别测定了强度、体变、含水率及饱和度等相关状态参量的变化规律。结果表明:剪切至临界状态过程中,不同干密度非饱和粉砂的强度和变形特性差异明显;随轴向应变的不断增加,不同初始干密度粉砂试样的偏应力、体应变以及饱和度曲线最终趋于稳定值,试样剪切达到临界状态。基于试验结果,揭示了临界状态条件下非饱和粉砂强度、孔隙比、孔隙水比体积随吸力的变化规律,并建立了q–p?、ν–ln p?、νw–ln p?平面内的临界状态线方程,提出了从强度、变形和孔隙水三个方面对非饱和粉砂临界状态进行综合描述的方法。

关键词：非饱和土粉砂三轴剪切试验临界状态

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非饱和土力学中几个基本问题的探讨

岩土力学 2013年第7期34卷 1825-1831页

作者：赵成刚李舰刘艳蔡国庆 asreazad saman 北京交通大学土木建筑工程学院北京100044

近些年非饱和土力学的研究非常活跃,但对一些基本问题的认识并不一致,有时甚至概念混淆。针对非饱和土力学的几个基本问题:非饱和土状态变量的选择、非饱和土有效应力变量的选择、吸力概念的界定和轴平移技术的局限性、非饱和土的结构... 详细信息

近些年非饱和土力学的研究非常活跃,但对一些基本问题的认识并不一致,有时甚至概念混淆。针对非饱和土力学的几个基本问题:非饱和土状态变量的选择、非饱和土有效应力变量的选择、吸力概念的界定和轴平移技术的局限性、非饱和土的结构的表征方法等问题进行了分析和探讨。其中非饱和土状态变量和有效应力的选择对于非饱和土力学的理论和相应本构模型的建立具有重要影响,因此,首先深入讨论了这一问题,概括论述了非饱和土有效应力的演变并深入探讨了目前各种形式有效应力的优缺点。其次,指出由于受负压孔隙水气化(液-气相变化)的影响,在实际场地中大于某一界限值的基质吸力是不存在的;目前被广泛使用的轴平移试验技术却掩盖了这一情况,而基于此所建立的非饱和土强度和变形理论的适用性需要进一步的研究和论证。再次,指出非饱和土的结构除了包括组构和颗粒之间作用力的综合效应外,还建议增加孔隙水和孔隙气的分布以及各相之间的相互作用和物理-化学作用。最后对一些容易混淆的概念进行了梳理。其目的是希望国内同行在今后的研究中对这些问题加以关注,并建立正确的认识,促进非饱和土力学沿着正确的方向发展。

关键词：非饱和土吸力非饱和土有效应力轴平移技术的局限性非饱和土结构

The input work expression and the thermodynamics-based modelling framework for unsaturated expansive soils with double porosity

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Chinese Science Bulletin 2013年第13期58卷 3422-3429页

作者： LI Jian ZHAO ChengGang CAI GuoQing asreazad saman XU Xi Frank HUANG QiDi School of Civil Engineering Beijing Jiaotong University ARC Centre of Encellence for Geotechnical Science and Engineering The University of Newcastle

In this paper, based on the porous media theory, the specific expressions of the total stress and the input work of unsaturated expansive soils with double porosity are proposed, and then the energy-conjugate variables are further derived. We make distinctions between the effects of capillary water and adsorbed water on the soil behaviour, as well as between the deformations of microand macrostructure. According to the derived input work expression and the work-energy-dissipation relations for an open multiphase thermodynamic system, we establish a thermodynamics-based modelling framework for unsaturated expansive soils with double porosity.

关键词：非饱和膨胀土热力学系统输入饱和双重介质建模框架工作表多孔介质宏观结构

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试样尺寸及制样粒径大小对粗粒土三轴试验抗剪强度的影响

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北京交通大学学报 2014年第4期38卷 133-136页

作者：沙曼赵成刚康凯北京交通大学土木建筑工程学院北京100044

三轴试验是确定土的抗剪强度的主要方法,试样尺寸是影响三轴试验结果的重要因素之一.粗粒土的三轴试验需要采用大尺寸的试样进行,相应需要采用大尺寸试验装置及更多的制样用土.与大尺寸三轴试验相比,采用小尺寸三轴压力室,所需的试样较... 详细信息

三轴试验是确定土的抗剪强度的主要方法,试样尺寸是影响三轴试验结果的重要因素之一.粗粒土的三轴试验需要采用大尺寸的试样进行,相应需要采用大尺寸试验装置及更多的制样用土.与大尺寸三轴试验相比,采用小尺寸三轴压力室,所需的试样较小,制样用土较少,且小尺寸三轴试验过程更快,试验成本更低.但采用小尺寸试样对粗粒土进行三轴试验时,往往得到偏小的抗剪强度参数,导致实际工程设计过于保守而不经济.为了降低试验成本,可以采用小尺寸试样进行试验,通过对试验结果进行修正来获得大尺寸试样试验结果,进而使工程设计具有良好的经济性.针对以上问题,本文对比研究了不良级配砾质砂混合物在采用去粗法前后制样试验所得的抗剪强度,提出了采用不同尺寸试样进行试验时对试验结果进行修正的方法及计算公式.

关键词：抗剪强度粗粒土三轴试验试样尺寸颗粒级配重塑

Macroseismic intensity attenuation in Iran

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Earthquake Engineering and Engineering Vibration 2018年第1期17卷 139-148页

作者： saman Yaghmaei-Sabegh Department of Civil Engineering University of Tabriz

Macroseismic intensity data plays an important role in the process of seismic hazard analysis as well in developing of reliable earthquake loss models. This paper presents a physical-based model to predict macroseismic intensity attenuation based on 560 intensity data obtained in Iran in the time period 1975-2013. The geometric spreading and energy absorption of seismic waves have been considered in the proposed model. The proposed easy to implement relation describes the intensity simply as a function of moment magnitude, source to site distance and focal depth. The prediction capability of the proposed model is assessed by means of residuals analysis. Prediction results have been compared with those of other intensity prediction models for Italy, Turkey, Iran and central Asia. The results indicate the higher attenuation rate for the study area in distances less than 70 km.

关键词： intensity prediction equations macroseismic attenuation model intensity data Iran

Effect of ground motion duration on inelastic displacement ratio of SDOF systems

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Earthquake Engineering and Engineering Vibration 2023年第2期22卷 423-439页

作者： saman Yaghmaei-Sabegh Sonia Daneshgari Department of Civil Engineering University of TabrizTabriz 51666-16471Iran

In this paper,the influence of ground motion duration on the inelastic displacement ratio,C_(1),of highly damped SDOF systems is *** this purpose,two sets of spectrally equivalent long and short duration ground motion records were used in an analysis to isolate the effects of ground motion duration *** effect of duration was evaluated for observed values of C_(1) by considering six ductility levels,and different damping and post-yield stiffness ratios.A new predictive equation of C_(1) also was developed for long and short duration *** of non-linear regression analysis of the current study provide an expression with which to quantify the duration *** on the average values of estimated C_(1) ratios for long duration records divided by C_(1) for a short duration set,it is concluded that the maximum difference between long and short duration records occurs when the damping ratio is 0.3 and the post-yield stiffness ratio is equal to zero.

关键词： inelastic displacement ratio long and short duration earthquakes highly damped SDOF systems ductility

A modified three–term conjugate gradient method with sufficient descent property

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Applied Mathematics(A Journal of Chinese Universities) 2015年第3期30卷 263-272页

作者： saman Babaie–Kafaki Department of Mathematics Faculty of Mathematics Statistics and Computer Science Semnan University

A hybridization of the three–term conjugate gradient method proposed by Zhang et al. and the nonlinear conjugate gradient method proposed by Polak and Ribi`ere, and Polyak is suggested. Based on an eigenvalue analysis, it is shown that search directions of the proposed method satisfy the sufficient descent condition, independent of the line search and the objective function convexity. Global convergence of the method is established under an Armijo–type line search condition. Numerical experiments show practical efficiency of the proposed method.

关键词： unconstrained optimization conjugate gradient method eigenvalue sufficient descent condition global convergence

Determination of influential parameters for prediction of total sediment loads in mountain rivers using kernel-based approaches

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Journal of Mountain Science 2020年第2期17卷 480-491页

作者： Kiyoumars ROUSHANGAR saman SHAHNAZI Department of Water Resource Engineering Faculty of Civil EngineeringUniversity of TabrizTabrizIran Center of Excellence in Hydroinformatics University of Tabriz29 Bahman AveTabrizIran

It is important to have a reasonable estimation of sediment transport rate with respect to its significant role in the planning and management of water resources projects. The complicate nature of sediment transport in gravel-bed rivers causes inaccuracies of empirical formulas in the prediction of this phenomenon. Artificial intelligences as alternative approaches can provide solutions to such complex problems. The present study aimed at investigating the capability of kernel-based approaches in predicting total sediment loads and identification of influential parameters of total sediment transport. For this purpose, Gaussian process regression(GPR), Support vector machine(SVM) and kernel extreme learning machine(KELM) are applied to enhance the prediction level of total sediment loads in 19 mountain gravel-bed streams and rivers located in the United States. Several parameters based on two scenarios are investigated and consecutive predicted results are compared with some well-known formulas. Scenario 1 considers only hydraulic characteristics and on the other side, the second scenario was formed using hydraulic and sediment properties. The obtained results reveal that using the parameters of hydraulic conditions asinputs gives a good estimation of total sediment loads. Furthermore, it was revealed that KELM method with input parameters of Froude number(Fr), ratio of average velocity(V) to shear velocity(U*) and shields number(θ) yields a correlation coefficient(R) of 0.951, a Nash-Sutcliffe efficiency(NSE) of 0.903 and root mean squared error(RMSE) of 0.021 and indicates superior results compared with other methods. Performing sensitivity analysis showed that the ratio of average velocity to shear flow velocity and the Froude number are the most effective parameters in predicting total sediment loads of gravel-bed rivers.

关键词： Total sediment loads Support vector machine Gaussian process regression Kernel extreme learning machine Mountain Rivers

Printabilitye-A key issue in extrusion-based bioprinting

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Journal of Pharmaceutical Analysis 2021年第5期11卷 564-579页

作者： saman Naghieh Xiongbiao Chen Division of Biomedical Engineering College of EngineeringUniversity of SaskatchewanSaskatoonSKS7N 5A9Canada Department of Mechanical Engineering College of EngineeringUniversity of SaskatchewanSaskatoonSKS7N 5A9Canada

Three-dimensional(3D)extrusion-based bioprinting is widely used in tissue engineering and regenerative medicine to create cell-incorporated constructs or scaffolds based on the extrusion *** critical issue in 3D extrusion-based bioprinting is printability or the capability to form and maintain reproducible 3D scaffolds from bioink(a mixture of biomaterials and cells).Research shows that printability can be affected by many factors or parameters,including those associated with the bioink,printing process,and scaffold design,but these are far from *** review highlights recent developments in the printability assessment of extrusion-based bioprinting with a focus on the definition of printability,printability measurements and characterization,and printability-affecting *** issues and challenges related to printability are also identified and discussed,along with approaches or strategies for improving printability in extrusion-based bioprinting.

关键词： Extrusion 3D bioprinting Bioink Printability Tissue engineering