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Experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering boundary effect

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 1072-1084页

作者： Xuwei Wang Yeshuang Xu State Key Laboratory of Ocean Engineering School of Naval ArchitectureOceanand Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China Shanghai Key Laboratory for Digital Maintenance of Buildings and Infrastructure Department of Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

The boundary condition is a crucial factor affecting the permeability variation due to suffusion.An experimental investigation on the permeability of gap-graded soil due to horizontal suffusion considering the boundary effect is conducted,where the hydraulic head difference(DH)varies,and the boundary includes non-loss and soil-loss conditions.Soil samples are filled into seven soil storerooms connected in turn.After evaluation,the variation in content of fine sand(ΔR_(f))and the hydraulic conductivity of soils in each storeroom(C_(i))are analyzed.In the non-loss test,the soil sample filling area is divided into runoff,transited,and accumulated areas according to the negative or positive ΔR_(f) values.ΔR_(f) increases from negative to positive along the seepage path,and Ci decreases from runoff area to transited area and then rebounds in accumulated area.In the soil-loss test,all soil sample filling areas belong to the runoff area,where the gentle-loss,strengthened-loss,and alleviated-loss parts are further divided.ΔR_(f) decreases from the gentle-loss part to the strengthened-loss part and then rebounds in the alleviated-loss part,and C_(i) increases and then decreases along the seepage path.The relationship between ΔR_(f) and Ci is different with the boundary condition.Ci exponentially decreases with ΔR_(f) in the non-loss test and increases with ΔR_(f) generally in the soil-loss test.

关键词： Suffusion Permeability Experimental investigation boundary effect Horizontal seepage

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boundary effect of toppling failure based on three-dimensional mechanical model

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Journal of Mountain Science 2022年第11期19卷 3314-3322页

作者： CAI Jun-chao ZHENG Da JU Neng-pan HUANG Run-qiu ZHAO Wei-hua School of Civil Engineering Henan University of Science and TechnologyLuoyang 471023China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu 610059China College of Environment and Civil Engineering Chengdu University of TechnologyChengdu 610059China

Previous researches on the mechanical model of toppling failure mainly concentrated on twodimensional mechanical model(TwDM) analysis. The TwDM analysis assumes the width of the slab beam is unit width without considering the lateral constraint force. The assumed conditions are obviously different from the site conditions, thus there is a certain difference between the calculated results and the field work. A three-dimensional mechanical model(ThDM)of toppling failure was established, considering that the slab beam was mainly subject to self-weight, the frictional resistance of interlayer and lateral constraint force. Due to the progressive characteristics of toppling failure, the concept and the formula of the first fracture depth(FFD) of toppling was raised and constructed. The case study indicates that the ThDM is more effective and can be accurately used to calculate the toppling fracture depth of the slab beam. The FFD decreases proportionally with the increase of slab beam width. FFD grows fast when the slab beam width is less than 2.0 m and it tends to be stable when the slab beam width is above 2.0 m. The FFD decreases with the increase of the lateral constraint coefficient, indicating that the boundary condition of the free space is positively correlated with the stability and depth of toppling. This is a good explanation of the free space effect. This study provides a reference for the stability evaluation and prevention-control design of toppling slope in the future.

关键词： boundary effect Toppling failure Three-dimensional mechanical model(ThDM) First fracture depth(FFD) Free face Slope failure

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Semi-analytical solution for drained expansion analysis of a hollow cylinder of critical state soils

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2326-2340页

作者： He Yang Jialiang Zhang Haisui Yu Peizhi Zhuang School of Qilu Transportation Shandong UniversityJinan250002China School of Civil Engineering University of LeedsLeedsLS29JTUK

The expansion of a thick-walled hollow cylinder in soil is of non-self-similar nature that the stress/deformation paths are not the same for different soil material points.As a result,this problem cannot be solved by the common self-similar-based similarity techniques.This paper proposes a novel,exact solution for rigorous drained expansion analysis of a hollow cylinder of critical state soils.Considering stress-dependent elastic moduli of soils,new analytical stress and displacement solutions for the nonself-similar problem are developed taking the small strain assumption in the elastic zone.In the plastic zone,the cavity expansion response is formulated into a set of first-order partial differential equations(PDEs)with the combination use of Eulerian and Lagrangian descriptions,and a novel solution algorithm is developed to efficiently solve this complex boundary value problem.The solution is presented in a general form and thus can be useful for a wide range of soils.With the new solution,the non-self-similar nature induced by the finite outer boundary is clearly demonstrated and highlighted,which is found to be greatly different to the behaviour of cavity expansion in infinite soil mass.The present solution may serve as a benchmark for verifying the performance of advanced numerical techniques with critical state soil models and be used to capture the finite boundary effect for pressuremeter tests in small-sized calibration chambers.

关键词： Cavity expansion Drained analysis boundary effect Critical state soil Non-self-similar Eulerian-Lagrangian approach

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boundary effect of Planar Glow Dielectric Barrier Discharge and Its Influence on the Discharge Structure

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Plasma Science and Technology 2015年第5期17卷 384-391页

作者：徐绍伟李璐璐欧阳吉庭 School of Physics Beijing Institute of Technology

The dielectric barrier discharge （DBD） in the glow regime in neon has been investigated by experiment and two-dimensional （2D） fluid modeling. The discharge was carried out in a planar DBD system with segmented-electrodes driven by square-wave voltage. The results show that the glow DBD originates in the center of the electrode and expands outward to the electrode edge during each half cycle of the voltage, forming a radial structure. The discharge decays firstly in the inner area but sustains longer in the edge area, showing a reversed discharge area. The discharge cannot completely cover the entire electrode surface, but remains a border of nonor weak discharge. The fluid modeling shows a similar result in agreement with the experiments. The simulations indicate that the electric field in the edge area is distorted due to the boundary effect so that the electric field and charge distribution are different from that in the inner part. The distorted field reduces the longitudinal component near the edge and causes the local field to be lower than that in the center, and hence makes the discharge behindhand. It also induces a transverse field that makes the discharge extend radially outward to the edge. The boundary effect plays an important role in the glow DBD structure.

关键词： DBD radial structure glow discharge boundary effect

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Influence of boundary effect on Fracture of Concrete

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青岛理工大学学报 2010年第4期31卷 1-11页

作者： K Duan X Z Hu F H Wittmann T Zhao CQ University Gladstone Australia School of Mechanical Engineering University of Western Australia35 Stirling Highway Crawley WA 6009 Australia Aedificat Institute Freiburg Germany Qingdao Technological University Qingdao 266033 China

The recently-developed boundary effect concept and the associated asymptotic model are used to analyze size-dependent fracture of concrete specimens.It is shown that the dependence of concrete fracture on specimen size,crack and/or ligament length is due to the same mechanism,i.***.the interactions between the crack tip fracture process zone and specimen's boundaries.By introducing an equivalent crack length ae,dimension dependent fracture becomes equivalent to fracture of a large plate with a small edge crack,and therefore,follows the same relationship of the 'net' nominal strength σn versus ae.As a result,the size dependent fracture can be predicted using the data measured on different types of specimens.To demonstrate the flexibility and effectiveness of the asymptotic boundary effect model,previously published results of three test series are analyzed.Excellent agreement has been found.Implications of the successful prediction are discussed.

关键词： boundary effect fracture of concrete asymptotic model

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effect of boundary Condition on Impact Response and Damage Meso-mechanism for Scarf Bonded Repair of Load-bearing Composite Structures

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International Journal of Plant Engineering and Management 2018年第1期23卷 7-17页

作者： LIU Bin HAN Qing LU Zhi-xian ZHONG Xiao-ping School of Aeronautics Northwestern Polytechnical UniversityXi'an 710072China

Composite scarf repair is applied in airplane load-bearing structures. But the repairs would have different boundary supports in real situation, such as simply support, clamped support and flexible support. With different boundary supports, the bonded scarf repair of composite structures could have diverse damage mechanisms and responses. This work intends to study the impact performance of different boundaries. For this purpose, experimental tests were carried out on the specimens with two sides support and four sides support. The impact load and deflection was monitored during the tests. After impact being finished, the meso-mechanism was studied by means of micro-cracks of the side section for two sides support condition and cross section for the four sides support condition. It was possible to conclude that the four sides boundary possess higher impact resistance maximum loads, lower displacements and lower extent load dropping. In terms of damage modes, as the impact energy relative low 12 J and 16 J, the central position of scarf bonding zone for two sides support appears adhesive cohesive failure and adhesive-composite interface failure. When the energy increases to 20 J, the dominated damage of two sides support moves down to the feathered tip. For four sides support, the critical energy level is 25 J, under which the scarf adhesive begins to be damaged.

关键词： boundary effect repair scarf CFRP meso-mechanism micro-cracks

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数字基础设施、边界效应与区域发展差距

区域与城市经济

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区域与城市经济 2024年第2期

作者：张翱孙久文

影响中国经济高质量发展的一个重要短板是由行政区边界效应带来的区域经济发展差距过大问题。数字基础设施建设的市场整合效应，加快了不同类型区域市场之间的融通，更有利于行政区边界区域经济的发展，缩小区域经济发展差距，促进区域... 详细信息

影响中国经济高质量发展的一个重要短板是由行政区边界效应带来的区域经济发展差距过大问题。数字基础设施建设的市场整合效应，加快了不同类型区域市场之间的融通，更有利于行政区边界区域经济的发展，缩小区域经济发展差距，促进区域协调发展。以“宽带中国”政策的实施作为数字基础设施建设的代理变量，以是否位于省级边界线上作为不同类型区域的划分标准，采用双重差分法，实证检验了数字基础设施建设缩小区域经济发展差距的作用。研究发现，“宽带中国”政策对位于省级边界线上的县的收入水平的提升作用更大，说明该政策降低了行政区边界效应，缩小了区域经济发展差距。从机制上看，数字基础设施建设主要通过促进行政边界地区居民获取金融服务、提升行政边界地区的工业和服务业劳动生产率来促进行政边界地区居民收入水平的提高。

关键词：数字基础设施边界效应市场整合区域发展差距 digital infrastructure boundary effect market integration regional coordinated development

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A simple method for determining independent fracture toughness and tensile strength of rock

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International Journal of Mining Science and Technology 2022年第4期32卷 707-726页

作者： Junfeng Guan Yulong Zhang Jiangfeng Meng Xianhua Yao Lielie Li Shuanghua He School of Civil Engineering and Communication North China University of Water Resources and Electric PowerZhengzhou 450045China State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan UniversityChengdu 610065China

This paper develops a model that only requires two sets of small-size rock specimens with the ratio of the structural geometry parameter maximum to minimum ae,max:ae,min≥3:1 to determine the rock fracture and strength parameters without size effect and predict the actual structural performance of rock.Regardless of three-point-bending,four-point-bending,or a combination of the above two specimen types,fracture toughness KICand tensile strength ftof rock were determined using only two sets of specimens with ae,max:ae,min≥3:1.The values KICand ftwere consistent with those determined using multiple sets of specimens.The full structural failure curve constructed by two sets of small-size specimens with ae,max:ae,min≥3:1 can accurately predict large-size specimens fracture failure,and±10%upper and lower limits of the curve can encompass the test results of large-size specimens.The peak load prediction curve was constructed by two sets of specimens with ae,max:ae,min≥3:1,and±15%upper and lower limits of the peak load prediction curve can cover the small-size specimen tests data.The model and method proposed in this paper require only two sets of small-size specimens,and their selection is unaffected by the specimen type,geometry,and initial crack length.

关键词： Rock Size effect boundary effect Structural geometry parameter Fracture toughness Tensile strength

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Molecular force mechanism of hydrodynamics in clay nanopores

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浙江大学学报(英文版)A辑:应用物理与工程 2023年第9期24卷 817-827页

作者： Shengjie WEI Yuchao LI Peng SHEN Yunmin CHEN MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering College of Civil Engineering and ArchitectureZhejiang UniversityHangzhou 310058China

Nanopores are prevalent within various clay morphologies,and water flow in clay nanopores is significant for various engineering applications.In this study,we performed non-equilibrium molecular dynamics(NEMD)simulations to reveal the molecular force mechanisms of water flow in clay nanopores.The water dynamic viscosity,slip length,and average flow velocity were obtained to verify the NEMD models.Since the water confined in the nanopores maintained a dynamic mechanical equilibrium state,each water lamina can be regarded as a simply supported beam.The applied driving force,the force from clay crystal layers,the force from compensating sodium ions,and the force from other water laminae were further calculated to investigate the force mechanisms.The van der Wals barrier above the surface and hydraulic gradient lead to distribution differences in water oxygen atoms,which contribute to a net van der Waals resistance component of the force from clay crystal layers.Meanwhile,the water molecules tend to rotate to generate the electrostatic resistance component of the force from clay crystal layers and balance the increasing hydraulic gradient.Due to the velocity difference,the water molecules in the slower lamina have a higher tendency to lag and generate a net electrostatic resistance force as well as a net van der Waals driving force on the water molecules in the faster lamina,which together make up the viscous force.

关键词： Molecular dynamics Hydrodynamics Clay Nanopore Molecular force boundary effect Viscous force

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boundary effect of Electrophoresis: Cylinder in Cylindrical Pore

Boundary Effect of Electrophoresis: Cylinder in Cylindrical ...

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中国颗粒学会2002年年会暨海峡两岸颗粒技术研讨会

作者：徐治平高承远 Department of Chemical Engineering Taiwan University Taipei 10617 Department of Chemical Engineering Taiwan University Taipei 10617

＜正＞ Electrophoresis, one of the electrokinetic phenomena, is a widely used analytical tool in practice to characterize the surface properties of a colloidal particle. Although it has been studied extensively, the behavior of electrophoresis under general conditions has not been reported yet. In particular, when the boundary effect needs to be considered. In this case, due to the presence of complicated interactions between hydrodynamic and electric fields, solving the governing equations, which are nonlinear and coupled differential equations, is not an easy task. The boundary effect of electrophoresis is of both fundamental and practical significance. In the electrophoresis of an entity in a narrow space such as a pore, for instance, the presence of pore wall should be taken into account. Another example is the electrophoresis of a concentrated dispersion in which the interaction between neighboring particles can not be ignored. Previous results for electrophoresis are ample in the literature. Most of them, however, are based on the case when the boundary effect can be neglected, and available results for the case when this effect is taken into account are limited to simple geometries in that the end effect is insignificant. In this study, the boundary effect of electrophoresis is investigated by considering a finite cylinder in a cylindrical pore. We show that while the direction of the movement of a particle is determined by the charged conditions on its lateral surface, the magnitude of its mobility is controlled by that on its top and bottom surfaces. It was found that the mobility of a uniformly charged particle may have a local maximum as the ratio（particle radius/pore radius） varies. The mobility decreases with the increase in particle aspect ratio.

关键词： electrophoresis boundary effect finite cylinder cylindrical pore

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