scholarly journals Modelling desiccation crack geometry evolution in clayey soils by analytical and numerical approaches

2019 ◽  
Vol 56 (5) ◽  
pp. 720-729 ◽  
Author(s):  
Thi Dong Vo ◽  
Amade Pouya ◽  
Sahar Hemmati ◽  
Anh Minh Tang
Keyword(s):  
General Trend ◽  
Crack Depth ◽  
Numerical Results ◽  
Soil Parameters ◽  
Desiccation Rate ◽  
Empirical Relations ◽  
Proposed Model ◽  
Numerical Approaches ◽  
Soil Tensile Strength

In the present work, the development and geometry of desiccation cracks are studied by using a finite element code including cohesive joints elements. The numerical results show that cracking occurs sequentially to form different crack families. The propagation of each crack at the onset suddenly reaches an ultimate depth. The cracks in each family appear simultaneously and reach an identical ultimate depth. From the numerical results and additional analytical analysis, empirical correlations are proposed to predict the spacing and crack depth as a function of suction applied on the top surface, the soil parameters, and the desiccation rate. The proposed model shows that higher suction is required to initiate cracks at a higher value of soil tensile strength. In addition, there is a general trend of larger spacing and deeper cracks for a slower desiccation rate. Finally, empirical relations are evaluated by comparing them with in situ experimental observations published previously.

scholarly journals Development of Fragility Curves for Piping and Slope Stability of River Levees

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 738
Author(s):  
Nicola Rossi ◽  
Mario Bačić ◽  
Meho Saša Kovačević ◽  
Lovorka Librić
Keyword(s):  
Slope Stability ◽  
Fragility Curves ◽  
Safety Margin ◽  
Water Levels ◽  
Flood Event ◽  
Soil Parameters ◽  
Design Code ◽  
A Site ◽  
Insight Into

The design code Eurocode 7 relies on semi-probabilistic calculation procedures, through utilization of the soil parameters obtained by in situ and laboratory tests, or by the means of transformation models. To reach a prescribed safety margin, the inherent soil parameter variability is accounted for through the application of partial factors to either soil parameters directly or to the resistance. However, considering several sources of geotechnical uncertainty, including the inherent soil variability, measurement error and transformation uncertainty, full probabilistic analyses should be implemented to directly consider the site-specific variability. This paper presents the procedure of developing fragility curves for levee slope stability and piping as failure mechanisms that lead to larger breaches, where a direct influence of the flood event intensity on the probability of failure is calculated. A range of fragility curve sets is presented, considering the variability of levee material properties and varying durations of the flood event, thus providing crucial insight into the vulnerability of the levee exposed to rising water levels. The procedure is applied to the River Drava levee, a site which has shown a continuous trend of increased water levels in recent years.

Effects of Stress Path and Stress History on the Stiffness of Reconstituted London Clay

1986 ◽  
Vol 2 (1) ◽  
pp. 139-144 ◽  
Author(s):  
J. H. Atkinson ◽  
J. S. Evans ◽  
D. Richardson
Keyword(s):  
Stress Path ◽  
Triaxial Tests ◽  
Soil Parameters ◽  
Stress History ◽  
Strain Behaviour ◽  
Reconstituted Soil ◽  
Path Dependent ◽  
London Clay ◽  
Soil Behaviour

AbstractSoil behaviour is stress history dependent and stress path dependent and soil parameters, particularly those for stress-strain behaviour, measured in conventional triaxial tests may not represent the behaviour of soil in many civil engineering works.To obtain more realistic parameters it may be necessary to conduct laboratory tests which more closely represent in situ conditions before and during construction.The paper describes equipment developed at The City University to carry out stress path tests simply and economically. A series of CU triaxial tests and stress path tests on reconstituted soil illustrate the dependence of measured soil parameters on stress history and stress path.

scholarly journals Abnormal Prediction of Dense Crowd Videos by a Purpose–Driven Lattice Boltzmann Model

2017 ◽  
Vol 27 (1) ◽  
pp. 181-194 ◽  
Author(s):  
Yiran Xue ◽  
Peng Liu ◽  
Ye Tao ◽  
Xianglong Tang
Keyword(s):  
Lattice Boltzmann ◽  
General Trend ◽  
Lattice Boltzmann Model ◽  
Training Procedure ◽  
Particle Collisions ◽  
Proposed Model ◽  
Dense Crowds ◽  
Dense Crowd ◽  
Boltzmann Model ◽  
Abnormal Events

Abstract In the field of intelligent crowd video analysis, the prediction of abnormal events in dense crowds is a well-known and challenging problem. By analysing crowd particle collisions and characteristics of individuals in a crowd to follow the general trend of motion, a purpose-driven lattice Boltzmann model (LBM) is proposed. The collision effect in the proposed method is measured according to the variation in crowd particle numbers in the image nodes; characteristics of the crowd following a general trend are incorporated by adjusting the particle directions. The model predicts dense crowd abnormal events in different intervals through iterations of simultaneous streaming and collision steps. Few initial frames of a video are needed to initialize the proposed model and no training procedure is required. Experimental results show that our purpose-driven LBM performs better than most state-of-the-art methods.

scholarly journals Soil physico-chemical characterization in the different soil layers of National Maize Research Program, Rampur, Chitwan, Nepal

2018 ◽  
Vol 3 (1) ◽  
pp. 28-44
Author(s):  
Dinesh Khadka ◽  
Sushil Lamichhane ◽  
Amit P Timilsina ◽  
Bandhu R Baral ◽  
Kamal Sah ◽  
...  
Keyword(s):  
Research Program ◽  
Soil Structure ◽  
Sandy Loam ◽  
Chemical Properties ◽  
Single Layer ◽  
Chemical Characterization ◽  
Bottom Layer ◽  
Soil Parameters ◽  
Physico Chemical

Soil pit digging and their precise study is a decision making tool to assess history and future of soil management of a particular area. Thus, the present study was carried out to differentiate soil physico-chemical properties in the different layers of excavated pit of the National Maize Research Program, Rampur, Chitwan, Nepal. Eight pits were dug randomly from three blocks at a depth of 0 to 100 cm. The soil parameters were determined in-situ, and in laboratory for texture, pH, OM, N, P (as P2O5), K (as K2O), Ca, Mg, S, B, Fe, Zn, Cu and Mn of collected soils samples of different layers following standard analytical methods at Soil Science Division, Khumaltar. The result revealed that soil structure was sub-angular in majority of the layers, whereas bottom layer was single grained. The value and chrome of colour was increasing in order from surface to bottom in the majority pits. Similarly, the texture was sandy loam in majority layers of the pits. Moreover, four types of consistence (loose to firm) were observed. Furthermore, mottles and gravels were absent in the majority layers. Likewise, soil was very to moderately acidic in observed layers of majority pits, except bottom layer of agronomy block was slightly acidic. Regarding fertility parameters (OM, macro and micronutrients), some were increasing and vice-versa, while others were intermittent also. Therefore, a single layer is not dominant for particular soil physico-chemical parameters in the farm. In overall, surface layer is more fertile than rest of the layers in all the pits.     

RECENT DEVELOPMENTS IN THE NUMERICAL SIMULATION OF SHALLOW WATER EQUATIONS II: TEMPORAL DISCRETIZATION

1994 ◽  
Vol 04 (04) ◽  
pp. 533-556 ◽  
Author(s):  
V. AGOSHKOV ◽  
E. OVCHINNIKOV ◽  
A. QUARTERONI ◽  
F. SALERI
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Finite Difference ◽  
Shallow Water ◽  
Shallow Water Equations ◽  
Numerical Results ◽  
Finite Difference Approximation ◽  
Difference Approximation ◽  
Recent Developments ◽  
Numerical Approaches

This paper deals with time-advancing schemes for shallow water equations. We review some of the existing numerical approaches, propose new schemes and investigate their stability. We present numerical results obtained using the time-advancing schemes proposed, with finite element and finite difference approximation in space variables.

scholarly journals Asymmetric multifractal model for solar wind intermittent turbulence

2008 ◽  
Vol 15 (4) ◽  
pp. 615-620 ◽  
Author(s):  
A. Szczepaniak ◽  
W. M. Macek
Keyword(s):  
Solar Wind ◽  
Solar Maximum ◽  
Solar Wind Plasma ◽  
Intermittent Turbulence ◽  
Proposed Model ◽  
Scaling Parameters ◽  
Generalized Dimensions ◽  
Multifractal Nature ◽  
Turbulent Cascade

Abstract. We consider nonuniform energy transfer rate for solar wind turbulence depending on the solar cycle activity. To achieve this purpose we determine the generalized dimensions and singularity spectra for the experimental data of the solar wind measured in situ by Advanced Composition Explorer spacecraft during solar maximum (2001) and minimum (2006) at 1 AU. By determining the asymmetric singularity spectra we confirm the multifractal nature of different states of the solar wind. Moreover, for explanation of this asymmetry we propose a generalization of the usual so-called p-model, which involves eddies of different sizes for the turbulent cascade. Naturally, this generalization takes into account two different scaling parameters for sizes of eddies and one probability measure parameter, describing how the energy is transferred to smaller eddies. We show that the proposed model properly describes multifractality of the solar wind plasma.

J-Integral Analysis of Surface Cracks in Round Bars under Bending Moments

2011 ◽  
Vol 52-54 ◽  
pp. 43-48 ◽  
Author(s):  
Al Emran Ismail ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Mariyam Jameelah Ghazali ◽  
Ruslizam Daud
Keyword(s):  
Finite Element ◽  
Crack Depth ◽  
Crack Tip ◽  
Bending Moment ◽  
Limit Load ◽  
Fe Model ◽  
Surface Cracks ◽  
Element Analysis ◽  
Reference Stress ◽  
Proposed Model

This paper presents a non-linear numerical investigation of surface cracks in round bars under bending moment by using ANSYS finite element analysis (FEA). Due to the symmetrical analysis, only quarter finite element (FE) model was constructed and special attention was given at the crack tip of the cracks. The surface cracks were characterized by the dimensionless crack aspect ratio, a/b = 0.6, 0.8, 1.0 and 1.2, while the dimensionless relative crack depth, a/D = 0.1, 0.2 and 0.3. The square-root singularity of stresses and strains was modeled by shifting the mid-point nodes to the quarter-point locations close to the crack tip. The proposed model was validated with the existing model before any further analysis. The elastic-plastic analysis under remotely applied bending moment was assumed to follow the Ramberg-Osgood relation with n = 5 and 10. J values were determined for all positions along the crack front and then, the limit load was predicted using the J values obtained from FEA through the reference stress method.

scholarly journals Examination of soil parameters based on the evaluation of the spectroradiometric reflectance characteristics of the topsoil

2014 ◽  
pp. 75-80
Author(s):  
Károly Bakos ◽  
Attila Dobos ◽  
János Nagy
Keyword(s):  
Measurement Techniques ◽  
Soil Surface ◽  
Soil Parameters ◽  
Surface Reflectance ◽  
Imaging Spectrometer ◽  
Top Soil ◽  
Multiple Samples ◽  
Physical And Chemical ◽  
Landscape Formation

In this article we are presenting the methodology applied to analyse and interpret the topsoil surface reflectance parameters of multiple samples collected in the Mugello valley area in northern Italy in October 2012. The main aim of the whole project was to discover geomorphological behaviour and situation of the area ino order to improve potential for correct dating of certain archaeological artefacts found in the nearby areas. One of the crucial problem researchers are facing in the area is the lack of understanding of the underlying geological and geomorphological processes that were describing and characterizing the area and that played important role not only in the current geography and landscape formation but also in the transportation of various sediments and artefacts. In this particular research the main aim is to examine the possibility of developing a quick way to assess low level properties of the soil using hand held spectrometer and rapid analysis of cross-section using in situ measurement techniques. In this work we collected over 2000 individual samples of topsoil surface reflectance properties that we organized into a spectral library. This library is then to be used to describe physical and chemical processes in the soil. To support the analysis results were compared to analysis results from different kind of assessments in the same area. Our results show a great potential of application of hand held imaging spectrometer in soil property analysis based on the top soil surface reflectance parameters.

Effect of a local crack on the dynamic characteristics of a rotating grouped blade disc

2001 ◽  
Vol 216 (4) ◽  
pp. 447-457 ◽  
Author(s):  
B W Huang ◽  
J H Kuang
Keyword(s):  
Dynamic Characteristics ◽  
Rotational Speed ◽  
Crack Depth ◽  
Numerical Results ◽  
Galerkin’S Method ◽  
Mode Localization ◽  
Torsion Spring ◽  
Crack Distribution ◽  
Localization Phenomenon ◽  
Blade Crack

The effects of a local blade crack and the group arrangement on the mode localization in a rotating turbodisc are studied in this paper. Periodically coupled Euler—Bernoulli beams are used to approximate the grouped and shrouded turboblades. A two-span beam with a torsion spring is used to model the cracked blade. The crack depth characterizes the stiffness of the assumed torsion spring. Galerkin's method is applied to formulate the localization equations of the grouped turbodisc system. Numerical results indicate that the crack depth, crack distribution and rotational speed in a rotating grouped blade disc may significantly affect the localization phenomenon.

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