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Acta Mechanica Solida Sinica 2012年第2期25卷 186-196页

作者： Guobin Gong Xiaoxiong Zha Jun Wei Civil and Environmental Engineering Graduate School in ShenzhenHarbin Institute of TechnologyHIT campusUniversity TownXiliNanshan DistrictShenzhen 518055China (2 School of Civil Engineering Central Sourh UniversityChangsha 410004China

Three dimensional （3D） DEM （discrete element method） simulations of drained triaxial compression and plane strain tests are presented for both dense and loose assemblies of polydisperse spheres using a periodic cell. In the work reported, drained tests were modelled by deforming the samples under constant mean stress conditions. The drained behaviour is shown to be qualitatively similar to published physical experimental results. The Bishop＇s formula for the estimation of the intermediate principal stress is evaluated. The existence of critical density is shown to be independent of initial packing densities and strain conditions. Different failure criteria have been compared based on the DEM simulation results, and the Lade criterion is found to be the most appropriate one. A new microscopic fabric parameter is introduced to give insight to structural anisotropy under general 3D fabric conditions. It is found that two parameters characterize the evolution of the stress and fabric respectively independent of strain conditions.

关键词： DEM simulations drained constant mean stress failure criteria fabric

Visualization of drained rock volume(DRV) in hydraulically fractured reservoirs with and without natural fractures using complex analysis methods(CAMs)

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Petroleum Science 2019年第3期16卷 550-577页

作者： Aadi Khanal Ruud Weijermars Harold Vance Department of Petroleum Engineering Texas A&M University

The drainage areas(and volumes)near hydraulically fractured wells,computed and visualized in our study at high resolution,may be critically affected by the presence of natural *** a recently developed algorithm based on complex analysis methods(CAMs),the drained rock volume(DRV)is visualized for a range of synthetic constellations of natural fractures near hydraulic ***,flow interference effects near a single hydraulic fracture are systematically investigated for a variety of natural fracture *** permeability contrast between the matrix and the natural fractures is increased stepwise in order to better understand the effect on the ***,a larger-scale model investigates flow interference for a full hydraulically fractured well with a variety of natural fracture *** time of flight contours(TOFCs)outlining the DRV are for all cases with natural fractures compared to a base case without any natural *** natural fractures,with different orientations,hydraulic conductivity,and fracture density,may shift the TOFC patterns in the reservoir region drained by the hydraulically fractured well,essentially shifting the location of the well’s drainage *** CAM-based models provide a computationally efficient method to quantify and visualize the drainage in both naturally and hydraulically fractured reservoirs.

关键词： Natural fracture drained rock volume Drainage area distortion Hydraulic fractures

Vibration pore water pressure characteristics of saturated fine sand under partially drained condition

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Journal of Central South University 2008年第S2期15卷 209-214页

作者：王炳辉陈国兴 Institute of Geotechnical Engineering Nanjing University of Technology

Vibration pore water pressure characteristics of saturated fine sand under partially drained condition were investigated through stress-controlled cyclic triaxial tests employed varied fine content of samples and loading frequency. In order to simulate the partially drained condition, one-way drainage for sample was implemented when cyclic loading was applied. The results show that the vibration pore water pressure's response leads the axial stress and axial strain responses, and is lagged behind or simultaneous with axial strain-rate's response for all samples in this research. In addition, the satisfactory linear relationship between vibration pore water pressure amplitude and axial strain-rate amplitude is also obtained. It means that the direct cause of vibration pore water pressure generation under partially drained conditions is not the axial stress or axial strain but the axial strain-rate. The lag-phase between pore water pressure and axial strain-rate increases with the increase of the fine content or the loading frequency.

关键词： partially drained condition loading frequency fine content vibration pore water pressure axial strain-rate

A method of determining and designing the drained slope in drained aluminum reduction cells

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Journal of Central South University of Technology 2003年第1期10卷 74-77页

作者：周乃君梅炽姜昌伟李劼 InstituteonSimulationandOptimizationofPyroinstallationsCentralSouthUniversity

Based on principles of electromagnetic fluid dynamics the exerted forces and movement states of melted aluminum in the traditional reduction cells and the drained cells were compared and analyzed in this paper. And based on the theory of slow movement, a formula in respect of the drained angle was derived, i.e. θ≥(J zB x-J xB z)ρg-(J xB y-J yB x ). It can be seen that the drained slope can be decided by respectively multiplying the area current densities and magnetic induction intensities in three coordinate directions in aluminum reduction cells, and the drained slope is approximate to 0.6% derived from typical data based on measurement and calculation, which implies that the key parameter is obtained in designing of drained cells. The results can be used for a designing basis for drained cathodes.

关键词： aluminum reduction cell drained cell drained slope electromagnetic fluid

Shear Strength and Dilatancy of Calcareous Sand in the South China Sea

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China Ocean Engineering 2022年第5期36卷 781-790页

作者： PEI Hui-min WANG Dong Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China Qingdao National Laboratory for Marine Science and Technology Qingdao 266100China

The shear strength and dilatancy of typical uncemented calcareous sand from the South China Sea are investigated by soil lab *** to drained triaxial tests at various relative densities and confining stresses,it is found that the constant volume friction angle is approximated as 39°and the traditional Bolton’s equations can be modified to estimate the peak friction angle and dilation *** reliability of the equation proposed for the peak friction angle is verified in terms of calcareous sands from more onshore and offshore sites worldwide,while the errors of the predicted dilation angles scatter in a relatively large ***,the dilation angles of sands in the South China Sea are estimated by the equation presented with an error of±30%.The peak friction angle measured by the undrained is similar to that by the drained tests as the relative density smaller than 60%,while the former is slightly lower for denser samples.

关键词： calcareous sand triaxial tests friction angle dilatancy drained South China Sea

Tapered Suction Caissons:A Numerical Investigation into Their Pull-out Performance

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China Ocean Engineering 2009年第4期23卷 695-707页

作者： M.Zeinoddini J.Keyvani M.Nabipour Faculty of Civil Engineering KNToosi University of Technology Faculty of Engineering Tarbiat Moallem University

Suction caissons have been widely used as anchors and foundations for floating and fixed offshore platforms. The pull-out performance of conventional suction caissons （with upright walls） has been investigated by a number of researchers. However, no attention has been paid to tapered suction caissons. This paper deals with the performance of tapered suction caissons under vertical pull-out loads. A numerical approach is used for this purpose. The numerical model is first verified against test data available for common upright caissons. The verified model is then used to study the pullout performance of tapered suction caissons. It is noticed that the pull-out capacities exhibited by tapered suction caissons are in general considerably higher than those from their corresponding traditional upright caissons. To obtain an insight into this superior behaviour, effects from certain soil/caisson/drainage parameters on the pull-out capacity of tapered suction caissons are studied. Soil cohesion is noticed to have a linear improving effect on the capacity of both upright and ta- pered suction caissons. The soil internal friction angle is noticed to have an exponential increasing effect on the pull-out capacity. With a constant caisson diameter, an increase in the aspect ratio is seen to particularly influence the pull-out capacity. With a constant caisson length, an increase in the aspect ratio is discovered to result in non-linear decrease in the pull-out capacity. Under undrained conditions, tapered models generally show less sensitivity to above mentioned soil/caisson parameters as compared with those under drained conditions.

关键词： suction caisson pull-out capacity numerical study upright caisson tapered caisson offshore structure sand clay drained undrained

Laboratory Study of Geotextiles Performance on Reinforced Sandy Soil

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Journal of Earth Science 2016年第6期27卷 1060-1070页

作者： Brahim Abdelkader Arab Ahmed Belkhatir Mostefa Shahrour Isam Laboratory of Materials Sciences and Environment Civil Engineering Department Hassiba Ben Bouali University of ChiefChief 02000Algeria Laboratory of Civil Engineering and Geo-Environment(LGCGE) University of Lille 1Villeneuve d'Ascq 59650France

This paper presents the results of triaxial tests conducted for the investigation of the influence of geotextiles on stress-strain and volumetric change behaviour of reinforced sandy soil. Tests were carried out on loose sandy soil. The experimental program includes drained compression tests on samples reinforced with different values of both geotextiles layers （Ng） and confining pressure （σ′c）. Two methods of preparation were used： air pluviation （AP） and moist tamping （MT）. Test results show that the geotextiles induce a quasi-linear increase in the stress deviator （q） and volume contraction in the reinforced sand. Method of preparation significantly affects the shear strength; samples prepared by the air pluviation method and mobilized deviator stresses are significantly higher than those prepared by moist tamping method. Geotextiles restrict the dilation of reinforced sandy soil and consequently the contraction increases. The mobilized friction angle increases with increasing number of layers and decreases with increasing initial confining pressure. Samples prepared by moist tamping present mobilized friction angles significantly lower than those prepared by air pluviation method. For samples prepared by the air pluviation method, the secant modulus at ε1=1% and 5% decreases with increasing geotextile layers; those prepared by the moist tamping method, secant modulus at ε1=1% and 5% increases with increasing number of geotextile layer sand confining pressure. From 10% axial strain, secant modulus increases with increasing inclusions of geotextile layers.

关键词： sand triaxial geotextile drained method of preparation strength.

Consistency of Hydrologic Relationships of a Paired Watershed Approach

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American Journal of Climate Change 2013年第2期2卷 147-164页

作者： Herbert Ssegane Devendra M. Amatya George M. Chescheir Wayne R. Skaggs Ernest W. Tollner Jami E. Nettles Biological and Agricultural Engineering North Carolina State University Raleigh USA Center for Forested Wetlands Research US Department of Agriculture-Forest Service Cordesville USA College of Engineering University of Georgia Athens USA Weyerhaeuser Company Columbus USA

Paired watershed studies are used around the world to evaluate and quantify effects of forest and water management practices on hydrology and water quality. The basic concept uses two neighboring watersheds (one as a control and another as a treatment), which are concurrently monitored during calibration (pre-treatment) and post-treatment periods. A statistically significant relationship between the control and treatment watersheds is established during calibration period such that any significant shift detected in the relationship during treatment is attributed to the treatment effects. The approach assumes that there is a consistent, quantifiable, and predictable relationship between watershed response variables. This study tests the hypothesis that the hydrologic relationships between control and treatment watersheds for daily water table elevation (WTE) and daily flow data were similar without any statistically significant difference during two different calibration (1988-1989 and 2007-2008) and treatment periods (1995-1996 and 2009), when the control and treatment watersheds were interchanged. The watersheds are two artificially drained loblolly pine forests (D1: 24.7 haand D2: 23.6 ha) located in coastal North Carolina. Results depicted significantly similar WTE regression relationships during the two calibration periods but significantly different WTE relationships during the two treatment periods with reversed control and treatment watersheds. Calibration and treatment flow relationships, and the mean treatment effects on WTE and flow, before and after treatment reversal were significantly different (α = 0.05). The study also discusses causes of differences in hydrologic relationships and treatment effects for such reversal of treatments during a 21-year span of the study on these two similar and adjacent watersheds. The observed differences in the hydrologic relationships between control and treatment watersheds before and after treatment reversal may be at

关键词： drained Pine Forests Water Table Elevation Daily Flow Calibration Treatment Effects Bootstrapped Geometric Mean Regression Recursive Residuals CUSUMS Flow Duration Curve