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Undrained vane shear strength of sand-foam mixtures subjected to different shear rates

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第6期15卷 1591-1602页

作者： Jiazheng Zhong Shuying Wang Tongming Qu School of Civil Engineering Central South UniversityChangsha410075China Tunnel and Underground Engineering Research Center Central South UniversityChangsha410075China Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyClearwater BayHong KongChina

The shear strength of sand-foam mixtures plays a crucial role in ensuring successful earth pressure balance(EPB)shield *** the sand-foam mixtures are constantly sheared by the cutterhead and the screw conveyor with varied rotation speeds during tunneling,it is non-trivial to investigate the effect of shear rates on the undrained shear strength of sand-foam mixtures under chamber pressures to extend the understanding on the tunneling *** study conducted a series of pressurized vane shear tests to investigate the role of shear rates on the peak and residual strengths of sand-foam mixtures at different pore *** from the shear-rate characteristics of natural sands or clay,the results showed that the peak strength of sand-foam mixtures under high vertical total stress(σ_(v)≥200 kPa)and low foam injection ratio(FIR30%)decreased with the increase in shear ***,the peak strength was not measurably affected by shear *** sand-foam mixtures in the residual state resembled low-viscous fluid with yield stress and the residual strength increased slightly with shear *** addition,the peak and residual strengths were approximately linear with vertical effective stress regardless of the total stress and *** peak effective internal friction angle remained almost invariant in a low shear rate(γ′shear rate continued *** residual effective internal friction angle was lower than the peak counterpart and insensitive to shear *** study unveiled the role of shear rates in the undrained shear strength of sand-foam mixtures with various FIRs and vertical total *** findings can extend the understanding of the rate-dependent shear characteristics of conditioned soils and guide the decision-making of soil conditioning schemes in the EPB shield tunneling practice.

关键词： Sand-foam mixture shear rate Peak and residual strengths Effective stress Effective internal friction angle

Influence of Reverse Pressure on the shear Viscosity of Hydrophilic Poly(ethylene terephthalate) Melt

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Chinese Journal of Polymer Science 2014年第7期32卷 923-930页

作者： Zeng-ge Guo Xin Li Jian Li Bin Zhang 程博闻 State Key Laboratory of Hollow Fiber Membrane Materials and Processes Tianjin Polytechnic University State Key Laboratory of Bio-based Fiber Manufacture Technology China Textile Academy

The effect of reverse *** theological behavior has been studied. The apparatus is a capillary rheometer with counter pressure chamber being held at a high reverse pressure by means of a cock. The results show that with the increase in temperature, the shear viscosity of hydrophilic PET is reduced. It is different that the effect of temperature on shear viscosity is varied under the condition of all shear rates or all pressures, and the effect is more prominent at 50 MPa or at 216 s^-1. At the same time, the pressure coefficients decrease with increasing the shear rate and the temperature and tend to reach a constant value nearly at the temperature of 290 ℃.

关键词： Hydrophilic PET shear viscosity Pressure Temperature shear rate Pressure coefficients.

Quantitative Investigation on Structural Evolution of Co-continuous Phase under shear Flow

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Chinese Journal of Polymer Science 2022年第6期40卷 593-601页

作者： Jin Yin Qing-Feng Ouyang Zhao-Bo Sun Feng-Yang Wu Qian Liu Xi-Xi Zhang Ling Xu Hao Lin Gan-Ji Zhong Zhong-Ming Li College of Polymer Science and Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengdu 610065China

Components of co-continuous phase can form an interpenetrating network structure,which has great potential to synergistically improve the mechanical properties of the blends,and to impart the functional blends superior electrical conductivity and *** this work,the effects of shear rates(50-5000 s^(-1))at different temperatures on the phase morphology,phase size and lamellar crystallites of biodegradable co-continuous polybutylene terephthalate(PBAT)/polybutylene succinate(PBS)blend are quantitatively *** results show that the above features of the PBAT/PBS have a strong dependence on the shear flow and thermal *** co-continuous phase of the blend is well maintained at 130℃.Interestingly,this phase structure transforms into a“sea-island”structure at 160℃,which gradually recovers to a co-continuous phase when the shear rate increases from 1000 s^(-1) to 5000 s^(-1).The phase size decreases with the increase of shear rate both at 130℃ and 160℃ due to the refinement and deformation of phase structures caused by strong shear ***,a unique phenomenon is observed that the shear-induced lamellar crystallites are oriented perpendicular to shear direction in the range of 500-5000 s^(-1) at 130℃,while the orientation of lamellar crystallites at 160℃ is along the shear direction within the whole range of shear *** degree of orientation for the PBAT/PBS blend crystals increases first and then decreases at both temperatures *** addition,the range of shear rate has reached the level in the industrial ***,this work has important guiding significance for the regulation of the co-continuous phase structure and the performance for the blend in the practical processing.

关键词： Co-continuous phase shear rate Phase size Crystal orientation

Anisotropic shearing mechanism of Kangding slate:Experimental investigation and numerical analysis

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第5期16卷 1487-1504页

作者： Ping Liu Quansheng Liu Penghai Deng Yucong Pan Yiming Lei Chenglei Du Xianqi Xie The Key Laboratory of Geotechnical and Structural Engineering Safety of Hubei Province School of Civil EngineeringWuhan UniversityWuhan430072China State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan430072China

The shear mechanical behavior is regarded as an essential factor affecting the stability of the surrounding rocks in underground *** shear strength and failure mechanisms of layered rock are significantly affected by the foliation *** shear tests were conducted on cubic slate samples with foliation angles of 0°,30°,45°,60°,and 90°.The effect of foliation angles on failure patterns,acoustic emission(AE)characteristics,and shear strength parameters was *** on AE characteristics,the slate failure process could be divided into four stages:quiet period,step-like increasing period,dramatic increasing period,and remission period.A new empirical expression of cohesion for layered rock was proposed,which was compared with linear and sinusoidal cohesion expressions based on the results made by this paper and previous *** comparative analysis demonstrated that the new expression has better prediction ability than other *** proposed empirical equation was used for direct shear simulations with the combined finite-discrete element method(FDEM),and it was found to align well with the experimental *** both computational efficiency and accuracy,it was recommended to use a shear rate of 0.01 m/s for FDEM to carry out direct shear *** balance the relationship between the number of elements and the simulation results in the direct shear simulations,the recommended element size is 1 mm.

关键词： Anisotropy Empirical expression of cohesion foliation angles Combined finite-discrete element method(FDEM) shear rate Element size

THE INVESTIGATION ON THE RHEOLOGICAL BEHAVIOR OF SEMI-SOLID ALUMINUM ALLOY DURING DIE CASTING

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Acta Metallurgica Sinica(English Letters) 2002年第6期15卷 511-516页

作者： X.J. Yang and J.Liu School of Mechanic & Electronic Engineering, Nanchang University, Jiangxi 330029, China School of Mechanic & Electronic Engineering, Shanghai University, Shanghai 200072, China Sch. of Mech. and Electron. Eng. Nanchang Univ. Nanchang 330029 China Sch. of Mech. and Electron. Eng. Shanghai Univ. Shanghai 200072 China

Under the condition of die casting and reheating temperature of 570-580 degC, the rheological behavior of semi-solid aluminum alloy (A356) is pseudoplasticity at the shearrate of 2X10^-1X10^4s^(-1), and also shows dil... 详细信息

关键词： shear rate apparent viscosity viscosity model thixocasting

pH Value Effects in shear Rheology of Concentrated Alumina Suspensions

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Chinese Journal of Chemical Engineering 2000年第2期8卷 180-183页

作者：曾人杰魏光 B.Rand InstituteofChemistryandChemicalEngineering XiamenUniversityXiamen361005China SchoolofProcess EnvironmentalandMaterialsEngineeringUniversityofLeedsLeedsLS29JTUK

The influence of pH on the rheological properties of concentrated alumina suspensions was investigated. At various pH values, the alumina exhibited pseudoplastic, near Bingham flow behaviors. The fully-deflocculated suspensions exhibited Newtonian flow behaviors, while the fully-flocculated suspensions demonstrated very high viscosity and shear yield stress.

关键词： shear rate shear stress extrapolated shear yield stress plastic viscosity pH value

Experimental investigation on shear strength deterioration at the interface between different rock types under cyclic loading

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第8期16卷 3063-3079页

作者： Qiong Wu Zhiqi Liu Huiming Tang Liangqing Wang Xiaoxue Huo Zhen Cui Shiyu Li Bo Zhang Zhiwei Lin Faculty of Engineering China University of GeosciencesWuhan430074China Guangxi Fangchenggang Beitou Environmental Protection Water Co. Ltd.Fangchenggang538021China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China

The shear strength deterioration of bedding planes between different rock types induced by cyclic loading is vital to reasonably evaluate the stability of soft and hard interbedded bedding rock slopes under earthquake;however,rare work has been devoted to this subject due to lack of *** this study,experimental investigations on shear strength weakening of discontinuities with different joint wall material(DDJM)under cyclic loading were conducted by taking the interface between siltstone and mudstone in the Shaba slope of Yunnan Province,China as research objects.A total of 99 pairs of similar material samples of DDJM(81 pairs)and discontinuities with identical joint wall material(DIJM)(18 pairs)were fabricated by inserting plates,engraved with typical surface morphology obtained by performing three-dimensional laser scanning on natural DDJMs sampled from field,into mold *** shear tests were conducted on these samples to study their shear strength changes with the cyclic number considering the effects of normal stress,joint surface morphology,shear displacement amplitude and shear *** results indicate that the shear stress *** displacement curves under each shear cycle and the peak shear strength *** number curves of the studied DDJMs are between those of DIJMs with siltstone and mudstone,while closer to those of DIJMs with *** peak shear strengths of DDJMs exhibit an initial rapid decline followed by a gradual decrease with the cyclic number and the decrease rate varies from 6%to 55.9%for samples with varied surface morphology under different testing *** normal stress,joint surface morphology,shear displacement amplitude and shear rate collectively influence the shear strength deterioration of DDJM under cyclic shear loading,with the degree of influence being greater for larger normal stress,rougher surface morphology,larger shear displacement amplitude and faster shear rate.

关键词： Discontinuities with different joint wall material(DDJM) Discontinuities with identical joint wall material(DIJM) Cyclic shear test shear strength deterioration Joint surface morphology shear displacement amplitude shear rate Normal stress

Effect of lateral stress on frictional properties of a fracture in sandstone

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第11期16卷 4416-4427页

作者： Zhechao Wang Jinmeng Zhao Derek Elsworth Xia-Ting Feng Pengyu Wang Institute of Deep Engineering and Intelligent Technology Northeastern UniversityShenyang110819China Liaoning Provincial Research Center on Underground Storage Engineering Shenyang110819China Energy and Mineral Engineering EMS Energy Institute and G3 CenterPennsylvania State UniversityUniversity Park16802USA

The injection of large volumes of natural gas into geological formations,as is required for underground gas storage,leads to alterations in the effective stress exerted on adjacent *** increases the potential for their reactivation and subsequent earthquake *** measurements of the frictional properties of rock fractures have been conducted under normal and shear ***,faults in gas storage facilities exist within a true three-dimensional(3D)stress state.A double-direct shear experiment on rock fractures under both lateral and normal stresses was conducted using a true triaxial loading *** was observed that the friction coefficient increases with increasing lateral stress,but decreases with increasing normal *** impact of lateral and normal stresses on the response is primarily mediated through their influence on the initial friction *** allows for an empirical modification of the rate-state friction model that considers the influence of lateral and normal *** impact of lateral and normal stresses on observed friction coefficients is related to the propensity for the production of wear products on the fracture *** stresses enhance the shear strength of rock(*** criterion).This reduces asperity breakage and the generation of wear products,and consequently augments the friction coefficient of the ***,increased normal stresses inhibit dilatancy on the fracture surface,increasing the breakage of asperities and the concomitant production of wear products that promote rolling *** ultimately reduces the friction coefficient.

关键词： Sandstone fracture Friction coefficient Lateral stress Normal stress shear rate rate-state friction model

Molecular dynamics study of viscosity of aqueous NaCl solution confined in nanoscale channels

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Journal of Southeast University(English Edition) 2011年第3期27卷 257-260页

作者：李家鹏毕可东陈云飞陈敏王柱东南大学江苏省微纳生物医疗器械设计与制造重点实验室南京211189 东南大学MEMS教育部重点实验室南京210096

A physical model of bulk-nanochannel-bulk with buffer baths is built up using nonequilibrium molecular dynamics （MD） simulation to study the effects of vibrating silicon atoms on the viscosity of aqueous NaCl solutions confined in the nanochannel. The simulation is performed under different moving speeds of the upper wall, different heights and different surface charge densities in the nanochannel. The simulation results indicate that with the increase in the surface charge density and the decrease in the nanochannel height and the shear rate, the vibration effect of silicon atoms on the shear viscosity of the confined fluid in the nanochannel cannot be ignored. Compared with still silicon atoms, the vibrating silicon atoms result in the decrease in the viscosity when the height of the nanochannel is less than 0.8 nm and the shear rate is less than 1.0 ×10^11 s^-1, and the effect of the vibrating silicon atoms on the shear viscosity is significant when the shear rate is small. This is due to the fact that the vibrating silicon atoms weaken the interactions between the counter-ions （Na^＋） and the charged surface.

关键词： nanochannel molecular dynamics simulation vibrating silicon atom shear rate viscosity