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Three-dimensional numerical analysis of plant-soil hydraulic interactions on pore water pressure of vegetated slope under different rainfall patterns

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第9期16卷 3696-3706页

作者： Haowen Guo Charles Wang Wai ng Qi zhang Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong KongChina

understanding the pore water pressure distribution in unsaturated soil is crucial in predicting shallow landslides triggered by rainfall,mainly when dealing with different temporal patterns of rainfall ***,the hydrological response of vegetated slopes,especially three-dimensional(3D)slopes covered with shrubs,under different rainfall patterns remains unclear and requires further *** address this issue,this study adopts a novel 3D numerical model for simulating hydraulic interactions between the root system of the shrub and the surrounding *** series of numerical parametric studies are conducted to investigate the influences of slope inclination,rainfall pattern and rainfall *** rainfall patterns(advanced,bimodal,delayed,and uniform)and two rainfall durations(4-h intense and 168-h mild rainfall)are considered to study the hydrological response of the *** computed results show that 17%higher transpiration-induced suction is found for a steeper slope,which remains even after a short,intense rainfall with a 100-year return *** extreme rainfalls with advanced(PA),bimodal(PB)and uniform(Pu)rainfall patterns need to be considered for the short rainfall duration(4 h),while the delayed(PD)and uniform(Pu)rainfall patterns are highly recommended for long rainfall durations(168 h).The presence of plants can improve slope stability markedly under extreme rainfall with a short duration(4 h).For the long duration(168 h),the benefit of the plant in preserving pore-water pressure(PWP)and slope stability may not be sufficient.

关键词： Root-soil interactions Rainfall patterns Slope stability Three-dimensional(3D)

Modelling the water diversion of a sustainable cover system under humid climates

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2429-2440页

作者： Haowen Guo Charles Wang Wai ng Qi zhang Chuanxiang Qu Liwen Hu Shenzhen Research Institute of Hong Kong university of Science and Technology Shenzhen518057China Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong Kong SAR999077China CCCC Fourth Harbor Engineering Institute Co. LtdGuangzhou510230China

Extreme rainfall significantly threatens the safety of the landfill cover system,especially under humid *** study aims to provide design recommendations for a sustainable landfill cover system consisting of a low-permeability soil layer underlying a two-layer capillary barrier for humid ***,the numerical back-analysis was conducted for verification against a series of flume model ***,a parametric study was performed to investigate the effects of inclination angle,particle size and layer thickness on the lateral diversion length(DL)of the three-layer cover system under the 100-year return period rainfall of humid *** results show that the water lateral DL of the cover system can be greatly enhanced by increasing the inclination angle from 3°to 18°.Moreover,the bottom layer of the cover system with a coarser d10 was more susceptible to the impact of the heavy rainfall,while this can be alleviated by increasing the thickness of the bottom layer.A dimensionless number,defined as the ratio of thickness and d_(10) of the bottom layer,is proposed for designing lateral diversion of the three-layer cover system under humid *** preserve the maximum DL,it is suggested that the proposed dimensionless number should be larger than 95 and 110 for the design of rainfall events with 50-year and 100-year return periods for humid climates,respectively.

关键词： unsaturated soil Recycling Construction waste Three-layer landfill cover Water infiltration

Three-year field study on grass growth and soil hydrological properties in biochar-amended soil

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2764-2774页

作者： Haowen Guo Charles Wang Wai ng Junjun Ni Qi zhang Yuchen Wang Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong KongChina School of Transportation Southeast UniversityNanjingChina

Field monitoring was conducted to investigate and quantify the long-term effects of peanut shell biochar on soil-grass interaction over three *** 10 m5 m grassed plots were constructed in completely decomposed granitic *** of them were amended,respectively,with 5%and 10%biochar contents(m^(3)/m^(3))for grass growth,while the third was without biochar *** the threeyear monitoring,plant characteristics,saturated water permeability(k_(s))of grassed soil and soil suction were *** monitored results show that the grass leaf area index(LAI)and root length density(RLD)with biochar amendment were improved by 38%and 200%,*** the grassed plot without biochar,a threshold RLD existed with a value of 1.7 cm/cm^(3),beyond which k_(s) raised *** threshold RLD increased by 52%when biochar content increased from 0%to 10%.This implies that biochar may restrict the increase in k_(s) of grassed soil due to the rise in the threshold *** presence of biochar and grass can retain over 100%higher suction after heavy rainfalls,while 54%lower peak suction under evapotranspiration(ET)compared with the non-amended *** can alleviate the negative effects on hydraulic properties caused by plant growth and reduce ET-induced excessive water loss.A 5%peanut shell biochar content is recommended for the long-term management of vegetated earthen infrastructures.

关键词： Soil-grass interaction Biochar Long-term Water infiltration Soil drying

Master equation,design equations and runaway speed of the Kaplan turbine

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Journal of Hydrodynamics 2021年第2期33卷 282-300页

作者： zh.zhang zhAW Zurch University of Applied ScienceZurichSwitzerland

To make the Kaplan turbine technology comparable to both the Pelton and the Francis turbine,the master equation for the Kaplan turbine has been established by analyses similar to that-for the Francis *** analysis begins with the descriptions of free vortex flows at the runner inlet and the swirl flow at the impeller *** considering the Euler equation for specific work and by further evaluating the most significant shock and swirling losses,the first and the second energy equations in the form of hydraulic efficiency were *** master equation is then established by combining both energy *** addition,three design equations and a new design parameter are *** master equation relates the turbine hydromechanics to the geometrical design of both the runner and the guide-vane *** enables the complete hydraulic characteristics of a given Kaplan turbine to be analytically and simply computed.A computation example demonstrates the functionality and applicability of the *** the reconstructed master equation,the runaway speed of the Kaplan turbine and its dependence on the guide-vane setting can be easily and precisely *** bulb turbines with guide vanes directly ahead of the turbine runner in the same tube,all computations are also applicable using another equivalent control parameter.

关键词： Kaplan turbine master equation design equations design parameter runaway speed hydraulic efficiency shock loss swirling loss bulb turbines

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“如果”句功能的类型学考察

汉语学习 2024年第2期 22-32页

作者：吴炳章姜彩璨许冰中国海洋大学外国语学院山东青岛266100

“如果”句的语义结构和用法复杂多样,但学界对该结构的功能类型分析过于笼统。文章通过语料库梳理书面语中“如果”句的结构特点和语篇关系,对其进行了功能分类。从功能视角看,“如果”句在知识域、语言域和人际域中分别发挥前提限定... 详细信息

“如果”句的语义结构和用法复杂多样,但学界对该结构的功能类型分析过于笼统。文章通过语料库梳理书面语中“如果”句的结构特点和语篇关系,对其进行了功能分类。从功能视角看,“如果”句在知识域、语言域和人际域中分别发挥前提限定、语篇建构和会话修辞等功能。根据从句和主句的意义关系,“如果”句可以分为蕴含条件句和非蕴含条件句。各类“如果”句的功能各有句法语义特征。从各类“如果”句的用法分布看,“如果”句的主要功能是表达推理关系,其次是语篇关系,再次是话语修辞。

关键词： “如果”句假设条件句间接条件句

Master equation and runaway speed of the Francis turbine

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Journal of Hydrodynamics 2018年第2期30卷 203-217页

作者： zh.zhang Free Researcher Zurich Switzerland

The master equation of the Francis turbine is derived based on the combination of the angular momentum（Euler） and the energy laws. It relates the geometrical design of the impeller and the regulation settings（guide vane angle and rotational speed） to the discharge and the power output. The master equation, thus, enables the complete characteristics of a given Francis turbine to be easily computed. While applying the energy law, both the shock loss at the impeller inlet and the swirling loss at the impeller exit are taken into account. These are main losses which occur at both the partial load and the overloads and, thus, dominantly influence the characteristics of the Francis turbine. They also totally govern the discharge of the water through the impeller when the impeller is found in the standstill. The computations have been performed for the discharge, the hydraulic torque and the hydraulic efficiency. They were also compared with the available measurements on a model turbine. Excellent agreement has been achieved. The computations also enable the runaway speed of the Francis turbine and the related discharge to be determined as a function of the setting angle of the guide vanes.

关键词： Francis turbine master equation runaway speed hydraulic efficiency shock loss swirling loss streamline similarity method

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Journal of Hydrodynamics 2018年第1期30卷 140-152页

作者： zh.zhang Free Researcher Zurich Switzerland

An analytical method is presented, which enables the non-uniform velocity and pressure distributions at the impeller inlet of a pump to be accurately computed. The analyses are based on the potential flow theory and the geometrical similarity of the streamline distribution along the leading edge of the impeller blades. The method is thus called streamline similarity method（SSM）. The obtained geometrical form of the flow distribution is then simply described by the geometrical variable G（s） and the first structural constant G_Ⅰ. As clearly demonstrated and also validated by experiments, both the flow velocity and the pressure distributions at the impeller inlet are usually highly non-uniform. This knowledge is indispensible for impeller blade designs to fulfill the shockless inlet flow condition. By introducing the second structural constant G_Ⅱ, the paper also presents the simple and accurate computation of the shock loss, which occurs at the impeller inlet. The introduction of two structural constants contributes immensely to the enhancement of the computational accuracies. As further indicated, all computations presented in this paper can also be well applied to the non-uniform exit flow out of an impeller of the Francis turbine for accurately computing the related mean values.

关键词： Pumps streamline similarity method flow distribution shock loss structural constant

SuBSTRuCTuRE PRECONDITIONERS FOR NONCONFORMIng PLATE ELEMENTS

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Journal of Computational Mathematics 1998年第4期16卷 289-304页

作者： Shi, ZC Xie, zh Chinese Acad Sci ICMSEC State Key Lab Sci & Engn Comp Beijing 100080 Peoples R China Chinese Acad Sci Inst Atmospher Phys LASG Beijing 100080 Peoples R China

In this paper, we consider the problem of solving finite element equations of biharmonic Dirichlet problems. We divide the given domain into non-overlapping subdomains, construct a preconditioner for Morley element by substructuring on the basis of a function decomposition for discrete biharmonic functions. The function decomposition is introduced by partitioning these finite element functions into the low and high frequency components through the intergrid transfer operators between coarse mesh and fine mesh, and the conforming interpolation operators. The method leads to a preconditioned system with the condition number bounded by C(1 + log(2) H/h) in the case with interior cross points, and by C in the case without interior cross points, where H is the subdomain size and h is the mesh size. These techniques are applicable to other nonconforming elements and are well suited to a parallel computation.

关键词： substructure preconditioner biharmonic equation nonconforming plate element

MuLTIGRID METHODS FOR MORLEY ELEMENT ON NONNESTED MESHES

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Journal of Computational Mathematics 1998年第5期16卷 385-394页

作者： Shi, ZC Xie, zh Chinese Acad Sci ICMSEC State Key Lab Sci & Engn Comp Beijing 100080 Peoples R China Chinese Acad Sci Inst Atmospher Phys LASG Beijing 100080 Peoples R China

In this paper, we consider some multigrid algorithms for the biharmonic problem discretized by Morley element on nonnested meshes. Through taking the averages of the nodal variables we construct an intergrid transfer operator that satisfies a certain stable approximation property. The so-called regularity-approximation assumption is then established. Optimal convergence properties of the W-cycle and a uniform condition number estimate for the variable V-cycle preconditioner are presented. This technique is applicable to other nonconforming plate elements.

关键词： multigrid method Morley element nonnested meshes