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Effect of microstructure on water retention behavior of lateritic clay over a wide suction range 大吸力范围内红土粘土微观结构对保水性能的影响
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.5.417
Jin Pan, Zhen Wenzhan, Bo Chen, De’an Sun, You Gao, Y. Xiong
To investigate the effects of soil structrue and dry density on water retention behavior of lateritic clay over a wide suction range, the axial translation technique (ATT), filter paper technique (FPT) and vapour equilibrium technique (VET) were combined to obtain soil-water retention curves (SWRCs) of specimens with different structures and dry densities. Measured SWRCs indicate that the air-entry value (AEV) and descent gradient in terms of saturation degree versus suction relationship are smallest for undisturbed specimens, and are largest for pre-consolidated specimens. The SWRCs obtained from compacted specimens with different dry densities illustrate that the AEV and descent gradient of saturation degree versus suction relationship increase with increasing the dry density. However, the effects of soil structure and dry density on the water retention behavior can be negligible at high suctions, which are verified by the curves of gravimetric water content (w) verusus suction (s) coincided after a limiting suction for specimens with different structures and dry densities. In addition, the water retention behavior can be well illustrated by pore size distributions (PSDs), obtained from mercury intrusion porosimetry (MIP). The AEVs depend on the diameters that corresponding to dramatically increase in differential intruded void ratio. And the descent gradients in the saturation degree versus suction relationship depend on their distinct PSD ranges and incremental peaks in the dominant pore sizes. Furthermore, the consistences of the AEVs and limiting suctions, deduced from the PSDs and SWRCs, demonstrate that the water retention behavior is highly dependent on the PSDs, and the SWRC features can be captured well by the PSDs.
为了研究土结构和干密度对大吸力范围内红土粘土保水特性的影响,采用轴向平移技术(ATT)、滤纸技术(FPT)和蒸汽平衡技术(VET)相结合的方法,获得了不同结构和干密度下红土粘土的土-水保持曲线(SWRCs)。实测swrc表明,未扰动试样的空气入口值(AEV)和下降梯度(饱和度与吸力关系)最小,预固结试样最大。不同干密度压实试样的SWRCs结果表明,随着干密度的增加,AEV和饱和度-吸力关系的下降梯度增大。在高吸力条件下,土体结构和干密度对保水性能的影响可以忽略不计,不同结构和干密度的试样在极限吸力条件下的重力含水率(w)和吸力(s)曲线吻合证明了这一点。此外,汞侵入孔隙度法(MIP)得到的孔隙尺寸分布(psd)可以很好地说明水潴留行为。aev依赖于相应的直径,这对应于微分侵入空隙比的急剧增加。饱和度-吸力关系的下降梯度取决于其不同的PSD范围和优势孔径的增量峰值。此外,从psd和SWRC推断出的AEVs和极限吸力的一致性表明,psd高度依赖于psd,并且psd可以很好地捕捉SWRC特征。
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引用次数: 1
Development of orthotropic Winkler-like model for rotating cylindrical shell: Stability analysis 旋转圆柱壳正交各向异性类温克勒模型的建立:稳定性分析
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.3.253
M. Khadimallah, M. Hussain, Yahya Ahmad, Elaloui Elimame, A. Tounsi
Vibration investigation of rotating functionally graded cylindrical shells with fraction laws is studied here. Shell motion equations are framed according to the orthotropic Winkler-like model. For isotropic materials, the physical properties are same everywhere where the laminated and functionally graded materials, they vary from point to point. The influence of the polynomial, exponential and trigonometric fraction laws is investigated with simply supported condition. Also the variations have been plotted against the circumferential wave mode, length-to-radius and height-to-radius ratio. Moreover, backward and forward frequency pattern is observed increasing and decreasing for the various position of angular speed. The frequency first increases and gain maximum value for circumferential wave number. It is also exhibited that the effect of frequencies is investigated by varying the surfaces with stainless steel and nickel as a constituent material. The frequencies of trigonometric law is less than remaining laws.
本文研究了具有分数律的旋转功能梯度圆柱壳的振动特性。壳层运动方程根据正交各向异性类温克勒模型建立。对于各向同性材料,层压材料和功能梯度材料的物理性能在任何地方都是相同的,它们在每个点上都是不同的。在简支条件下研究了多项式定律、指数定律和三角分数定律的影响。此外,还根据周波模式、长度-半径比和高度-半径比绘制了变化曲线。此外,在不同的角速度位置,反向和正向的频率分布有增大和减小的趋势。频率首先增加,周向波数达到最大值。用不锈钢和镍作为组成材料改变表面,研究了频率的影响。三角律的频率比其他律少。
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引用次数: 1
End bearing capacity of embedded pile with inclined base plate:Field dynamic and static tests 斜底板预埋桩端部承载力:现场动、静力试验
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.3.261
Mi-Jeong Seo, Kyungsoo Han, Jongbae Park, Kyeong-han Jeong, Jong Sub Lee
The objective of this study is to investigate the effects of incorporating inclined base plates on the end bearing capacities of embedded piles by conducting dynamic pile tests and static load tests. Two types of embedded piles were prepared – conventional piles with a 50-cm-diameter flat base plate and piles with a 56-cm-diameter inclined base plate. The dynamic pile tests were conducted during pile construction, and the static load tests were conducted after curing the cement paste to investigate the end bearing capacities of the test piles. Test results indicate that the base resistances of piles with inclined base plates are greater than those of conventional piles and that the base resistances increase with an increase in the inclination angle. The increased projected area, increased contact area, extended rupture surface, and enhanced slime discharge due to the inclined base plate may result in an increase in the end bearing capacity of the pile. This study demonstrates that the end bearing capacities of the embedded piles may be maximized by incorporating inclined plates to the pile base. Thus, the pile with the inclined base plate may be effectively used for the construction of embedded piles.
本文通过动桩试验和静荷载试验,探讨加入倾斜底板对内嵌桩端部承载力的影响。制备了两种类型的嵌入式桩,一种是直径为50cm的平基桩,另一种是直径为56cm的斜基桩。施工过程中进行动桩试验,水泥浆养护后进行静载试验,研究试桩端部承载力。试验结果表明,斜底板桩的桩基阻力大于常规桩基阻力,且随着倾角的增大,桩基阻力增大。由于底板倾斜,桩的投影面积增大,接触面积增大,破裂面扩大,泥浆排出量增大,可能导致桩端承载力增大。研究表明,在桩底加装斜板可使桩端承载力最大化。因此,斜底板桩可以有效地用于预埋桩的施工。
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引用次数: 0
Influence of a preset fissure on clay behavior under uniaxial compression 单轴压缩下预设裂隙对粘土特性的影响
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.4.357
W. Wang, Bin Zhao, Aiyu Hu, J. Shang
Under compression, the flaws in soils will not only weaken the mechanical properties of soils, but also affect the strain localization of soils. In order to study the influence of flaws on the behavior of soils under compression, the uniaxial compression tests of clays with different inclination and position fissures were carried out, and the two-dimensional numerical analysis was also discussed based on the damage plasticity model. Analyzing the results of the uniaxial compression test and simulation of the intact and fissured clays, the following conclusions can be drawn: (1) The 60-degree fissure located on the upper position of the right edge of the clay has the greatest influence on the failure form and damage energy of clays, which can reduce the compression strength by 30% compared with that of the intact clay. (2) The numerical method based on the damage plasticity model can basically simulate the compression behavior of clays containing a pre-existing fissure and reproduce the failure characteristics of clays. (3) The preset fissure has obvious influence on the evolution of maximum principal stress in the area with serious damage, but less on the shear stress. And in the area with slight damage, the effect on the maximum principal stress and shear stress is very weak.
在压缩作用下,土的缺陷不仅会削弱土的力学性能,而且会影响土的应变局部化。为了研究裂纹对土体压缩特性的影响,进行了不同倾角和不同位置裂纹的单轴压缩试验,并基于损伤塑性模型进行了二维数值分析。通过对原状和裂隙粘土的单轴压缩试验和模拟结果的分析,得出以下结论:(1)位于粘土右边缘上部的60度裂隙对粘土的破坏形态和损伤能影响最大,与原状相比,该裂隙可使粘土的抗压强度降低30%。(2)基于损伤塑性模型的数值方法可以基本模拟含裂隙土体的压缩行为,重现土体的破坏特征。(3)在严重破坏区域,预设裂缝对最大主应力演化有明显影响,而对剪应力演化影响较小。在轻度损伤区域,对最大主应力和剪应力的影响非常弱。
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引用次数: 0
Effects of soaking on a lime stabilized clay and implications for pavement design 浸水对石灰稳定粘土的影响及其对路面设计的启示
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.2.115
I. Bozbey, M. K. Kelesoglu, S. Oztoprak, Muhammet Komut, Senol Comez, T. Ozturk, Aykan Mert, K. Ocal
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引用次数: 4
Reliability analysis of strip footing under rainfall using KL-FORM 基于KL-FORM的条形基础雨下可靠度分析
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.2.167
Suozhu Fei, Xiaohui Tan, W. Gong, Xiaole Dong, F. Zha, Long Xu
Spatial variability is an inherent uncertainty of soil properties. Current reliability analyses generally incorporate random field theory and Monte Carlo simulation (MCS) when dealing with spatial variability, in which the computational efficiency is a significant challenge. This paper proposes a KL-FORM algorithm to improve the computational efficiency. In the proposed KL-FORM, Karhunen-Loeve (KL) expansion is used for discretizing random fields, and first-order reliability method (FORM) is employed for reliability analysis. The KL expansion and FORM can be used in conjunction, through adopting independent standard normal variables in the discretization of KL expansion as the basic variables in the FORM. To illustrate the effectiveness of this KL-FORM, it is applied to a case study of a strip footing in spatially variable unsaturated soil under rainfall, in which the bearing capacity of the footing is computed by numerical simulation. This case study shows that the KL-FORM is accurate and efficient. The parametric analyses suggest that ignoring the spatial variability of the soil may lead to an underestimation of the reliability index of the footing.
空间变异性是土壤性质固有的不确定性。目前的可靠性分析在处理空间变异性时通常采用随机场理论和蒙特卡罗模拟方法,这对计算效率提出了很大的挑战。为了提高计算效率,本文提出了一种KL-FORM算法。在KL-FORM中,采用Karhunen-Loeve (KL)展开对随机场进行离散化,采用一阶可靠度法(FORM)进行可靠度分析。通过采用KL展开离散化中的独立标准正态变量作为FORM中的基本变量,可以将KL展开与FORM结合使用。为了说明该KL-FORM的有效性,将其应用于降雨条件下空间可变非饱和土条形基础的实例研究,并通过数值模拟计算了基础的承载力。实例研究表明,KL-FORM是准确、高效的。参数分析表明,忽略土体的空间变异性可能会导致对基础可靠度指标的低估。
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引用次数: 4
Theoretical model for the shear strength of rock discontinuities with non-associated flow laws 具有非关联流动规律的岩石结构面抗剪强度的理论模型
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.4.307
R. Galindo, Jose Andres, A. Lara, Bin Xu, Z. Cao, Yuanqiang Cai
In an earlier publication (Serrano et al. 2014), the theoretical basis for evaluating the shear strength in rock joints was presented and used to derive an equation that governs the relationship between tangential and normal stresses on the joint during slippage between the joint faces. In this paper, the theoretical equation is applied to two non-linear failure criteria by using non-associated flow laws, including the modified Hoek and Brown and modified Mohr-Coulomb equations. The theoretical model considers the geometric dilatancy, the instantaneous friction angle, and a parameter that considers joint surface roughness as dependent variables. This model uses a similar equation structure to the empirical law that was proposed by Barton in 1973. However, a good correlation with the empirical values and, therefore, Barton's equation is necessary to incorporate a non-associated flow law that governs breakage processes in rock masses and becomes more significant in highly fractured media, which can be induced in a rock joint. A linear law of dilatancy is used to assess the importance of the non-associated flow to obtain very close values for different roughness states, so the best results are obtained for null material dilatancy, which considers significant changes that correspond to soft rock masses or altered zones of weakness.
在早期的一篇论文(Serrano et al. 2014)中,提出了评估岩石节理抗剪强度的理论基础,并用于推导出一个方程,该方程用于控制节理面之间滑动时节理上的切向应力和法向应力之间的关系。本文采用非关联流动规律将理论方程应用于两种非线性失效判据,包括修正的Hoek和Brown方程和修正的Mohr-Coulomb方程。该理论模型考虑了几何剪胀、瞬时摩擦角和以节理表面粗糙度为因变量的参数。该模型使用了与巴顿在1973年提出的经验法则相似的方程结构。然而,与经验值的良好相关性,因此,巴顿方程是必要的,以纳入一个非关联的流动规律,控制岩体中的破坏过程,在高度断裂的介质中变得更加重要,这可以在岩石节理中引起。利用剪胀率的线性规律来评估非关联流动的重要性,以获得不同粗糙度状态下非常接近的值,因此零材料剪胀率得到了最好的结果,它考虑了对应于软岩体或改变的软弱带的显著变化。
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引用次数: 0
Evaluation of failure mode of tunnel-type anchorage for a suspension bridge via scaled model tests and image processing 基于比例模型试验和图像处理的悬索桥隧道型锚固破坏模式评价
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.5.457
S. Seo, H. Lim, M. Chung
In this study, the pull-out behavior of a tunnel-type anchorage for suspension bridges was investigated using experimental tests and image processing analyses. The study focused on evaluating the initial failure behavior and failure mode of the tunnel-type anchorage. In order to evaluate the failure mode of tunnel-type anchorage, a series of scaled model tests were conducted based on the prototype anchorage of the Ulsan Grand Bridge. In the model tests, the anchorage body and surrounding rocks were fabricated using a gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests demonstrate that the tunnel-type anchorage underwent a wedge-shaped failure. In addition, the failure mode changed according to the differences in the physical properties of the surrounding rock and the anchorage body and the size of the anchor plate. The size of the anchor plate was found to be an important parameter that determines the failure mode. However, the difference in physical properties between the surrounding rock and the anchorage body did not affect its size. In addition, this study analyzed the initial failure behavior of the tunnel-type anchorage through image analysis and confirmed that the failure was sequentially transferred from the inside of the tunnel to the surrounding rock according to the image analysis. The reasonable failure mode for the design of the tunnel-type anchorage should be wedge-type rather than pull-out type.
本文采用试验试验和图像处理分析的方法,对悬索桥隧道型锚杆的拉拔行为进行了研究。对隧道型锚固的初始破坏行为和破坏模式进行了研究。为了评价隧道型锚固的破坏模式,以蔚山大桥原型锚固为基础,进行了一系列的比例模型试验。在模型试验中,锚固体和围岩采用石膏混合料制作。研究了在平面应变条件下的拉拔行为。模型试验结果表明,隧道型锚杆发生楔形破坏。此外,破坏模式会根据围岩和锚固体物理性质的不同以及锚板尺寸的不同而发生变化。发现锚板的尺寸是决定其破坏模式的重要参数。但围岩与锚固体物理性质的差异并不影响锚固体的大小。此外,本研究通过图像分析分析了隧洞型锚固的初始破坏行为,并根据图像分析确认了破坏是由隧洞内部向围岩依次传递的。隧道式锚杆设计的合理破坏模式应为楔型而非拉拔型。
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引用次数: 4
Effects of dry density and water content on compressibility and shear strength of loess 干密度和含水量对黄土压缩性和抗剪强度的影响
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.5.419
Ye-xia Guo, W. Ni, Haisong Liu
Investigation on the compressibility and shear strength of compacted loess is of great importance for the design and operation of engineering infrastructures in filling area. In this study, the mechanical behaviors of Yan'an compacted loess are investigated at various dry densities and water contents by conducting one dimensional compression and direct shear tests. And the elastic compressibility, plastic compressibility, yield stress and strength are obtained from the experiments. Results show that when water content increases, plastic compressibility parameter increases, but yield stress decreases. However, the increase of dry density leads to a decrease in plastic compressibility parameter but an increase in yield stress. In addition, elastic compressibility parameter is found to be a constant which is irrelevant to water content and dry density. As for strength, cohesion and internal friction angle is directly proportional to dry density, but inversely proportional to water content. Moreover, the mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) tests were also performed to observe the pore size distribution and microstructure of the specimens. Finally, by using results of MIP and SEM tests, the compressibility and strength behaviours of Yan'an compacted loess are explained from the perspective of pore-size distribution and microstructure.
研究压实黄土的抗压性和抗剪强度对填筑区工程基础设施的设计和运行具有重要意义。通过一维压缩和直剪试验,研究了延安压实黄土在不同干密度和含水量下的力学行为。通过实验得到了材料的弹性压缩率、塑性压缩率、屈服应力和强度。结果表明:随着含水量的增加,塑性压缩系数增大,屈服应力减小;干密度的增大导致塑性压缩系数的减小,而屈服应力的增大。此外,发现弹性压缩系数是一个常数,与含水量和干密度无关。强度方面,黏聚力和内摩擦角与干密度成正比,与含水量成反比。采用压汞法(MIP)和扫描电镜(SEM)观察了试样的孔径分布和微观结构。最后,利用MIP和SEM测试结果,从孔隙尺寸分布和微观结构的角度解释了延安压实黄土的压缩性和强度特性。
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引用次数: 6
Deterministic and probabilistic analysis of tunnel face stability using support vector machine 基于支持向量机的巷道工作面稳定性确定性与概率分析
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.1.017
Bin Li, Yong Fu, Yi Hong, Zijun Cao
This paper develops a convenient approach for deterministic and probabilistic evaluations of tunnel face stability using support vector machine classifiers. The proposed method is comprised of two major steps, i.e., construction of the training dataset and determination of instance-based classifiers. In step one, the orthogonal design is utilized to produce representative samples after the ranges and levels of the factors that influence tunnel face stability are specified. The training dataset is then labeled by two-dimensional strength reduction analyses embedded within OptumG2. For any unknown instance, the second step applies the training dataset for classification, which is achieved by an ad hoc Python program. The classification of unknown samples starts with selection of instance-based training samples using the k-nearest neighbors algorithm, followed by the construction of an instance-based SVM-KNN classifier. It eventually provides labels of the unknown instances, avoiding calculate its corresponding performance function. Probabilistic evaluations are performed by Monte Carlo simulation based on the SVM-KNN classifier. The ratio of the number of unstable samples to the total number of simulated samples is computed and is taken as the failure probability, which is validated and compared with the response surface method.
本文提出了一种利用支持向量机分类器对巷道工作面稳定性进行确定性和概率性评价的简便方法。该方法包括两个主要步骤,即训练数据集的构建和基于实例的分类器的确定。第一步,在确定影响巷道工作面稳定性因素的范围和水平后,利用正交设计产生具有代表性的样品。然后,OptumG2中嵌入的二维强度降维分析对训练数据集进行标记。对于任何未知的实例,第二步应用训练数据集进行分类,这是由一个特设的Python程序实现的。未知样本的分类首先使用k近邻算法选择基于实例的训练样本,然后构建基于实例的SVM-KNN分类器。它最终提供未知实例的标签,避免计算其相应的性能函数。基于SVM-KNN分类器,通过蒙特卡洛模拟进行概率评估。计算不稳定样本数与模拟样本总数之比,作为失效概率,并与响应面法进行验证和比较。
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引用次数: 4
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Geomechanics and Engineering
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