Gluing process simula0on in realis0c railway ballast 鐵路道碴膠結模擬與分析. Chung Fang

Transcription

1 1 / 21 Gluing process simula0on in realis0c railway ballast 鐵路道碴膠結模擬與分析 Department of Civil Engineering Na7onal Cheng Kung University 04. November, 2016, Tainan, Taiwan

2 2 / 21 Contents: I. Introduc7on II. Simula7on technique and environment III. Influence of gluing solu7on layout IV. Influence of gravel segrega7on (greworldlist.wordpress.com) V. Influence on percola7on ability VI. Concluding remarks

3 I. Introduc0on 3 / 21 Ballast system : A collec7on of a large amount of gravels with prescribed distribu7ons of size/shape. A kind of dry granular maver (dry granular mixture). Important physical features: (sixpacktech.com) - Inelas7c network with force chains; - Long-term enduring fric7onal contact and sliding, and short-term elas7c/inelas7c instantaneous collision among the gravels; - Highly dissipa7ve in turbulent kine7c energy of gravels; - Temperature effect not relevant in (mechanical) characteris7cs; - Turbulent fluctua7ons.

4 Inten7ons of ballast system : - it supports the sleepers or bearers both ver7cally and laterally; - it spreads the loading from the sleepers or bearers onto the forma7on; - it provides a drainage path for precipita7on; - it facilitates adjustment of the track geometry. 4 / 21 Prac7cal ballast gravels : - the gravels assume the prescribed size, shape and volume percentage; - the gravels are sufficiently hard to resist crushing and abrasion; - the gravels are resistant to water, indicated by the wet avri7on value; - the gravels are angular to interlock into one another to form a stable matrix to support the track but allow free drainage. A ballast degrades or fails during opera7on : - destruc7ve gravel-gravel interac7on (e.g. crushing or abrasion) and environmental influence; - presence of fines, ingress of fines from above, or ingress of material from the forma7on; - presence of water, e.g. avri7on, ingress of vegetable maver, wet beds, slurry rising up through the ballast.

5 5 / 21 Purposes of ballast gluing : (midwestlab.com.uk) Protec7on from ballast flight by solidifica7on of the ballast building surface. Stabiliza7on of the ballast bed at railroad crossing and with switches. Stabiliza7on of transi7ons from concrete roadway to the ballast bed track. Solidifica7on of the ballast shoulder to avoid instabili7es. Gluing material : Polymeric resin solu7ons, usually a liquid, cold and solvent-free 2-component resin system. Gluing dura7on: hours. Non-Newtonian fluids: viscosity depending on shear rates. An7-thixotropic fluids: viscosity depending on 7me. Ballast solidifica7on by using gluing solu7on is purely empirical.

6 II. Simula0on technique and environment 6 / 21 Numerical gravel and ballast : (Lee et al) Vertex iden7fica7on technique from Prof. Lee. Generaliza7on of a single polyhedron gravel with arbitrary size, shape and volume. A realis7c ballast accomplished by following the prac7cal guide of AREMA (GMNH)

7 Rheological characteris7cs of gluing solu7on : 7 / 21

8 Simula7on environment : ( Keys to the ANSYS simula7on: Gluing process as non-newtonian fluid in gravity-driven laminar flows 8 / 21 Complex 7me-/temperature-dependent chemical reac7ons and solidifica7ons simplified by a phenomenological 7me-dependent viscosity. Gluing completed when the phenomenological viscosity approaches its maximum value. The final solidifica7on region and its shape can be iden7fied for further inves7ga7on (e.g. analysis of contact adhesion and vibra7on analysis of the glued ballast system). Fang C, Lee Y, Kuo CM, Lin YJ, Kuo C (2015) Anti-thixotropic non-newtonian fluid in complex conduct: gluing process simulation of railway ballast. Applied Rheology 25:14381 (DOI: /APPLRHEOL ).

9 Ques7ons to be clarified : 9 / 21 Op7mal gluing solu7on layout for specific solidifica7on distribu7on. Influence of gravel segrega7on. Influence on percola7on ability of solidified ballast. Geometry nata7on : gluing solu7on computa7onal domain plane 5 plane 4 plane 3 plane 2 plane 1

10 III. Influence of gluing solu0on layout 10 / 21 Single cell Network layout Matrix layout

11 11 / 21 plane 1 plane 2 plane 3

12 12 / 21 plane 4 plane 5 Ver7cal penetra7on is characterized by the solidifica7on speed. Lateral extension is rather limited and local, maximum to a width of the ini7al gluing solu7on span. Lateral extension can be improved by distribu7ng the gluing solu7on in either matrix or network layout. Directly pouring tends to create concrete gravel adhesion ver7cally, while a concrete lateral adhesion can be achieved by spreading the gluing solu7on in network layout onto the ballast with sa7sfied ver7cal adhesion. Fang C, Lee Y, Kuo CM, Lin YJ, Kuo C (2015) Anti-thixotropic non-newtonian fluid in complex conduct: gluing process simulation of railway ballast. Applied Rheology 25:14381 (DOI: /APPLRHEOL ) Fang C, Lee Y, Lin YJ, Lu LS, Chen PC (2016) Influence of gluing solution layout on gluing solution distribution in a realistic railway ballast. International Journal of Geomechics (in press) (DOI: /(ASCE)GM )

13 IV. Influence of gravel segrega0on 13 / 21 Uniform ballast Segregated ballast

14 14 / 21 plane 1 plane 2 plane 3

15 15 / 21 plane 4 plane 5 Concrete ver7cal and lateral adhesion can be achieved by using network layout for both ballasts. More concrete gravel adhesion is accomplished by using denser network layouts. Gravel segrega7on plays nearly insignificant role in the gluing solu7on distribu7on. Percola7on ability in the upper and central parts is influenced by gravel segrega7on. Fang C, Lee Y, Lin YJ, Lu LS, Chen PC (2016) Influence of gravel segregation on gluing solution solidification in a realistic railway ballasts. Acta Geotechnica (in press)

16 V. Influence on percola0on ability 16 / 21 Uniform ballast Segregated ballast

17 17 / 21 plane 1 plane 2 plane 3

18 18 / 21 plane 4 plane 5

19 19 / 21 Percola7on vs. 7me Ver7cal percola7on ability is bever in uniform ballast than the segregated one without gluing. Such a tendency is manifest in solidified ballasts. Ver7cal percola7on ability is significantly prohibited when gravel adhesion takes place. Fang C, Lee Y, Huang KL, Lu LS (2016) Percolation analysis of a solidified railway ballast. International Journal for Numerical and Analytical Methods in Geomechanics (in second review).

20 VI. Concluding remarks 20 / 21 Vertex iden7fica7on technique is proposed to generate realis7c ballast gravels. Unified elasto-visco-plas7c stress model with asympto7c 7me-increasing viscosity is proposed to account for the rheological characteris7cs of gluing solu7on. Integrated simula7on environment with ANSYS is established to simulate the solidifica7on process of gluing solu7on in realis7c ballast (an7-thixotropic, non- Newtonian flow in mul7-connected conduct system spanned by the ballast gravels). Influence of the layout and amount of gluing solu7on, as well as the percola7on ability of solidified ballast, can be es7mated a priori gluing prac7ce. Thank you for your interest

21 21 / 21 Acknowledgements Na7onal Science Council/Ministry of Science and Technology, Taiwan College of Engineering, Na7onal Cheng Kung University, Taiwan Deutsche Forschungsgemeinschai (DFG), Germany Collaborators : Prof. Yusin Lee Prof. Chen-Ming Kuo Dr. Yung-Jung Lin Mr. Li-Sin Lu, PhD candidate Mr. Gui-Lin Huang, MSc Mr. Bo-Chen Chen, MSc Mr. Chuan Kuo, MSc