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Effect of loading rate on Lateral Pile-Soil Interaction in Sand Considering Partially Drained Condition

China Ocean Engineering 2020年第6期34卷 772-783页

作者： ZHU Bin REN Jie WU Lei-ye KONG De-qiong YE Guan-lin YANG Qingjie LAI Ying MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Zhejiang UniversityHangzhou 310058China College of Civil Engineering and Architecture Zhejiang UniversityHangzhou 310058China Center for Hypergravity Experimental and Interdisciplinary Research Zhejiang UniversityHangzhou 310058China Department of Civil Engineering Shanghai Jiao Tong UniversityShanghai 200030China Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Department of Civil EngineeringHohai UniversityNanjing 210098China

Reliable assessment of the lateral pile–soil interaction is of pronounced importance for the design of mono-pile foundations of offshore wind turbines. As the offshore engineering moves to deeper waters, the diameter of monopiles is getting larger, usually about 5 m and could be up to 8 m, which may lead to partially drained behaviors of sand in the vicinity of the pile and thus imply limitations of conventional design methods in which fully drained conditions were assumed. To shed light on this issue, a fully-coupled finite element model was established using an in-house developed finite element code DBLEAVES, incorporating a cyclic mobility constitutive model that is capable of describing the instantaneous contractive and dilative response of sands simultaneously. Triaxial and centrifuge model tests were conducted to calibrate the constitutive model and validate the pile–soil interaction model respectively. This is followed by a parametric study primarily focusing on the effects of loading rates. The initial stiffness of the p–y curve was found to increase with the loading rate whilst the bearing capacity showed the inverse,and the mechanism behind this phenomenon is examined in detail. Then an explicit model was developed to evaluate the development of excess pore pressure in the pile front upon lateral loading, and an upper boundary of normalized loading rate was identified to distinguish fully and partially drained conditions.

关键词： monopiles partially drained loading rate excess pore pressure

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Effect of loading rate on shear strength parameters of mechanically and biologically treated waste

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Frontiers of Environmental Science & Engineering 2022年第12期16卷 121-132页

作者： Guoyang Fan Zhenying Zhang Jiahe Zhang Jiayue Zhang Qiaona Wang Min Wang Bang Wang Chengyu Nie School of Civil Engineering and Architecture Zhejiang Sci-tech UniversityHangzhou310018China

Mechanical biological treatment(MBT)technology has attracted increasing attention because it can reduce the volume of waste *** deal with the current trend of increasing waste,MBT practices are being adopted to address waste generated in developing urban *** this study,a total of 20 specimens of consolidated undrained triaxial tests were conducted on waste obtained from the Hangzhou Tianziling landfill,China,to evaluate the effect of loading rate on the shear strength parameters of MBT *** MBT waste samples exhibited an evident strain-hardening behavior,and no peak was observed even when the axial strain exceeded 25%.Further,the shear strength increased with an increase in the loading rate;the effect of loading rate on shear strength under a low confining pressure was greater than that under a high confining ***,the shear strength parameters of MBT waste were related to the loading *** relationship between the cohesion,internal friction angle,and logarithm of the loading rate could be fitted to a linear relationship,which was established in this ***,the ranges of shear strength parameters cohesion c and effective cohesion c′were determined as 1.0–8.2 kPa and 2.1–14.9 kPa,respectively;the ranges of the internal friction angleφand effective internal friction angleφ’were determined as 16.2°–29°and 19.8°–43.9°,*** results could be used as a valuable reference for conducting stability analyses of MBT landfills.

关键词： Mechanically and biologically treated waste Landfill Triaxial test loading rate Axial strain Shear strength parameter

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Effects of water intrusion and loading rate on mechanical properties of and crack propagation in coal–rock combinations

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Journal of Central South University 2017年第2期24卷 423-431页

作者：陈田姚强岭卫斐种照辉周健王常彬李静 School of Mines Key Laboratory of Deep Coal Resource Mining of Ministry of Education of China China University of Mining & Technology Xuzhou 221116 China

Tackling the problems of underground water storage in collieries in arid regions requires knowledge of the effect of water intrusion and loading rate on the mechanical properties of and crack development in coal–rock combinations. Fifty-four coal–rock combinations were prepared and split equally into groups containing different moisture contents(dry, natural moisture and saturated) to conduct acoustic emission testing under uniaxial compression with loading rates ranging from 0.1 mm/min to 0.6 mm/min. The results show that the peak stress and strength-softening modulus, elastic modulus, strain-softening modulus, and post-peak modulus partly decrease with increasing moisture content and loading rate. In contrast, peak strain increases with increasing moisture content and fluctuates with rising loading rate. More significantly, the relationship between stiffness and stress, combined with accumulated counts of acoustic emission, can be used to precisely predict all phases of crack propagation. This is helpful in studying the impact of moisture content and loading rate on crack propagation and accurately calculating mechanical properties. We also determined that the stress thresholds of crack closure, crack initiation, and crack damage do not vary with changes of moisture content and loading rate, constituting 15.22%, 32.20%, and 80.98% of peak stress, respectively. These outcomes assist in developing approaches to water storage in coal mines, determining the necessary width of waterproof coal–rock pillars, and methods of supporting water-enriched roadways, while also advances understanding the mechanical properties of coal–rock combinations and laws of crack propagation.

关键词： water intrusion loading rate mechanical properties coal-rock combination crack propagation stress threshold

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Characterization of loading rate Effects on the Interactions Between Crack Growth and Inclusions in Cementitious Material

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Computers, Materials & Continua 2018年第12期57卷 417-446页

作者： Shuai Zhou Xiaoying Zhuang Division of Computational Mechanics Ton Duc Thang UniversityHo Chi Minh CityVietnam Faculty of Civil Engineering Ton Duc Thang UniversityHo Chi Minh CityVietnam College of Materials Science and Engineering Chongqing UniversityChongqingChina Leibniz Universität Hannover Appelstr.1130167HannoverGermany

The microcapsule-enabled cementitious material is an appealing building material and it has been attracting increasing research *** considering microcapsules as dissimilar inclusions in the material,this paper employs the discrete element method(DEM)to study the effects of loading rates on the fracturing behavior of cementitious specimens containing the inclusion and the *** numerical model was first developed and validated based on experimental *** is then used to systematically study the initiation,the propagation and the coalescence of cracks in inclusion-enabled cementitious *** study reveals that the crack propagation speed,the first crack initiation stress,the coalescence stress,the compressive strength and the ultimate strain increase with the loading *** initiation position,the propagation direction,the cracking length and the type of the initiated cracks are influenced by the loading *** new crack coalescence patterns are *** is easier to cause the coalescence between the circular void and a propagating crack at a slow loading rate than at a fast loading rate.

关键词： Microcapsule loading rate cracking processes DEM compressive loading

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Micromechanical study of loading rate effects between a hole and a crack

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Underground Space 2019年第1期4卷 22-30页

作者： Shuai Zhou Xiaoying Zhuang Institute of Continuum Mechanics Leibniz University HannoverHannover 30167Germany Department of Geotechnical Engineering Tongji UniversityShanghai 200092China

The interactions between defects are important in *** micromechanical interactions between a circular hole and a pre-existing crack under uniaxial compression with different loading rates are investigated by the discrete element method(DEM).The crack initiation,crack propagation,and crack coalescence at different loading rates are *** loading rates influence the primary as well as secondary *** the primary and secondary cracks disturb the stress field and displacement *** DEM simulation explains the initiation position of the primary and secondary *** evolution of the displacement field and the stress field at different loading rates is analyzed.A new displacement field type is *** hole is easier to be broken by compression at higher loading rates while it tends to be broken by the coalescence crack at lower loading *** high loading rates lead to shielding effects of the hole on the pre-existing crack.

关键词： Rock Defect loading rate Cracking processes DEM Compressive loading

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MD simulations of loading rate dependence of detwinning deformation in nanocrystalline Ni

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Science China(Physics,Mechanics & Astronomy) 2013年第3期Mechanics & Astronomy) .卷 491-497页

作者： SU Hao TANG QiHeng State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of Sciences

Molecular dynamics simulations are performed to investigate the deformation behavior of nanocrystalline Ni with pre-twin atom *** simulation sample is composed of four grains with average size 12 *** simulation technique of isobaric-isothermal ensemble(NPT) with high pressure is applied to obtain a sample with two circle *** uniaxial tensile and shear loading,as well as different detwinning deformation behaviors are *** uniaxial tension the detwinning deformation is induced by the event of grain growth,and it is supported by local energy *** the shear loading the detwinning deformation is related to the loading *** results show that there may be a critical shear *** the shear rate is sufficiently high the circle twin is found to be failed;as the shear rate is less than that rate,the size of circle twin become smaller and gradually approach a constant *** simulation results are in good agreement with experiment observation.

关键词： molecular dynamics simulation detwinning loading rate

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Effects of loading rate on root pullout performance of two plants in the eastern Loess Plateau,China

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Journal of Arid Land 2023年第9期15卷 1129-1142页

作者： ZHANG Chaobo LI Rong JIANG Jing YANG Qihong College of Water Resources Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China Key Laboratory of the Regulation and Flood Control of Middle and Lower Reaches of the Changjiang River under Ministry of Water Resources Changjiang River Scientific Research InstituteWuhan 430010China

Root pullout performance of plants is an important mechanical basis for soil reinforcement by plant roots in the semi-arid *** have shown that it is affected by plant factors(species,ages,root geometry,etc.)and soil factors(soil types,soil moisture,soil bulk densities,etc.).However,the effects of loading rates on root pullout performance are not well *** explore the mechanical interactions under different loading rates,we conducted pullout tests on Medicago sativa *** Hippophae rhamnoides *** under five loading rates,i.e.,5,50,100,150,and 200 mm/*** addition,tensile tests were conducted on the roots in diameters of 0.5-2.0 mm to compare the relationship between root tensile properties and root pullout *** showed that two root failure modes,slippage and breakage,were observed during root pullout *** *** roots were pulled out,while 72.2%of *** roots were *** maximum fracture diameter and fracture root length of *** were 1.22 mm and 7.44 cm under 100 mm/min loading rate,*** displacement values were 4.63%(±0.43%)and 8.91%(±0.52%)of the total root length for *** and ***,*** values of maximum pullout force were 14.6(±0.7)and 17.7(±1.8)N under 100 mm/min for *** and ***,*** of the maximum pullout strength for *** and *** were 38.38(±5.48)MPa under 150 mm/min and 12.47(±1.43)MPa under 100 mm/min,***-soil friction coefficient under 100 mm/min was significantly larger than those under other loading rates for both the two *** of the maximum root pullout energy for *** and *** were 87.83(±21.55)mm•N under 100 mm/min and 173.53(±38.53)mm•N under 200 mm/min,*** pullout force was significantly related to root diameter(Ploading rates when the effect of root diameter was included(P<0.01),and vice *** fo

关键词： plant roots soil reinforcement loading rate root pullout properties root-soil interaction loess area

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Effect of loading rate on fracture characteristics of rock

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Journal of Central South University 2010年第1期17卷 150-155页

作者：周小平钱七虎杨海清 School of Civil Engineering Chongqing University PLA University of Science and Technology

The three-point bending experiments were applied to investigating effects of loading rates on fracture toughness of Huanglong limestone. The fracture toughness of Huanglong limestone was measured over a wide range of loading rates from 9 × 10-4 to 1.537 MPa.m1/2/s. According to the approximate relationship between static and dynamic fracture toughness of Huanglong limestone, relationship between the growth velocity of crack and dynamic fracture toughness was obtained. The main conclusions are summarized as follows. （1） When the loading rate is higher than 0.027 MPa-ml/2/s, the fracture toughness of Huanglong limestone increases markedly with increasing loading rate. However, when loading rate is lower than 0.027 MPa-ml/2/s, fracture toughness slightly increases with an increase in loading rate. （2） It is found from experimental results that fracture toughness is linearly proportional to the logarithmic expression of loading rate. （3） For Huanglong limestone, when the growth velocity of crack is lower than 100 m/s, the energy release rate slightly decreases with increasing the growth velocity of crack. However, when the growth velocity of crack is higher than 1 000 m/s, the energy release rate dramatically decreases with an increase in the crack growth velocity.

关键词： fracture toughness of rock three-point bending round bar loading rate velocity of crack growth

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INFLUENCE OF loading rate ON DYNAMIC FRACTURE BEHAVIOR OF FIBER-REINFORCED COMPOSITES

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Acta Mechanica Solida Sinica 2008年第5期21卷 457-460页

作者： Kezhuang Gong Zheng Li Weizhong Qin LTCS and College of Engineering Peking University Beijing 100871 China

The effect of loading rate on the dynamic fracture properties and the failure mechanisms of glass fiber-reinforced composite materials under mode I fracture is studied. Dynamic reflective caustic experiments are carried out for two loading rates. By measuring the characteristic dimensions of the shadow spots during the caustic experiments, the dynamic SIFs are calculated for different loading rates. The experimental results indicate that the dynamic fracture toughness Kid increases remarkably with increasing loading rate, and the crack grows faster under the high-velocity impact. Moreover, by examining the crack growth routes and the fracture surfaces, it is shown that the loading rate also greatly affects the failure mechanisms at micro-scale.

关键词： caustics method fiber-reinforced material mode I fracture loading rate

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Influence of the loading Protocol and loading rate on the Characteristics of Timber Nail Joints

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Journal of Renewable Materials 2022年第10期10卷 2655-2667页

作者： Shervin Shameli Derakhshan Lina Zhou Chun Ni Department of Civil Engineering University of VictoriaVictoriaV8P 5C2Canada Advanced Building Systems FPInnovationsVancouverV6T 1W5Canada

Nail joints are one of the key components that control the lateral performance of light wood frame shear *** previous experimental studies,researchers have used different loading rates,which failed specimens from less than a minute to more than an hour,to study the characteristics of nail ***,there have been different loading protocols used for testing of timber nail joints or shear *** some efforts have been made to address this subject,it is still unclear how the loading protocol and loading rate may influence the performance of nail *** this study,a total of 96 nail joints tests were carried out under monotonic and reversed-cyclic loads at three different loading rates,and under three different loading protocols(ISO,CUREE and SPD).The results of the test revealed that the loading rate did not have a noticeable effect on the mechanical properties of nail joints,while the loading protocol did influence those ***,protocols with larger cumulative damage demands lead to lower ultimate displacement and ductility of nail joints.

关键词： loading protocol loading rate timber nail joint reversed-cyclic load monotonic load

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