Strategic Young Researcher Overseas Visits Programfor Accelerating Brain Circulation 2011
“Development of Young Researchers
Based on International Joint Research
on Green Energy Systems”
Progress Report

1. Name: Bo Li
2. Title: Assistant Professor
3. Host Institution: Royal Institute of Technology (KTH) (Sweden)
4. Host Researcher: Associate Professor Lanru Jing
5. Duration: 26-September-2012 – 26-September-2013
6. Research Topic:
Coupled stress, flow, heat and mass transport behavior of fractured rockmasses
7. Overview of the Results of the Collaborative Research:
Coupled stress, flow, heat and mass transport is the corner stone subject for manygeoscience and geo-engineering disciplines. Many outstanding issues need to beinvestigated to enhance the knowledge on this subject, specifically more in-depth
research in testing and modeling of the coupled processes in rough rock fractures andintersections of rock fractures is needed. This collaborative research focuses on thissubject, which is especially important for infrastructure development, safety assessmentof energy facilities and geothermal energy exploitation (GED).
This research aims at solving two important problems met in geo-engineering: a) fastclosures of rock fractures observed in the initial stage of fluid flow experiments at
environmental temperatures under low or moderate normal stresses; b) the influences oflocal surface roughness of fractures on fluid flow and solute transport processes at themacroscopic scales of fracture networks. For the first problem, we modeled numericallythe asperity deformation and failure processes during initial normal loading, byadopting both elastic and elastic-plastic deformation models for the asperities on a realrock fracture with measured surface topography data, and estimated its impact on initialconditions for fluid flow test performed under laboratory conditions. The results showedthat the calculated local stresses were concentrated on the contacts of a few major
asperities, resulting in crushing of asperity tips. Single pressure solution may not likely
to be the principal compaction mechanism for this fast closure, and the damages on
contacting asperities that occur during the initial normal loading stage may play animportant role. For the second problem, we simulated flow and transport processes in
two different fracture networks, taking into account the influences of surface roughnessof rock fractures. The results showed that fracture roughness can affect the flow rates
and residence time to some extent. However, fracture roughness had negligible
influences on the general patterns of fluid flow and solute migration. In a highly
anisotropic fracture network, the solute transport behavior in different macroscopic
direction may be significantly different, but the difference was minor in an intensive
fracture system with relatively low anisotropy.
These studies led to one submission (under review) and one accepted publication oninternational journals. We consider this collaborative research a success and areplanning to continue the collaboration.

8. Deployment Plans for Future Collaborative Research:
The previous collaborative research focused on stress effect on fluid flow of roughrock fractures, with simple tracer tests considering only solute advection, under room
temperature. The research now needs to be extended to consider deformation, damage
and failure of contacting asperities of rock fractures and their effects on transportmechanisms, especially the shearing, cracking and crushing of contacting asperity tips,
where local stress concentration is much higher and reactive transport processes mostactive.
In the future studies, a comprehensive lab testing and mathematical model
development (in Nagasaki University), and numerical simulations (in KTH) for contact
mechanics of rock fractures during normal loading will be carried out. Based on theknowledge obtained from the contact mechanics research, tests on fluid flow and solutetransport will be conducted without shear, with the aim of quantitative model
establishments for: a) evolution of fluid flow channeling and flow field distribution withloading; b) processes of different solute transport mechanisms of stress solution ofminerals at contacting asperities, solute sorption on fracture surfaces, and diffusion in
the rock matrix; c) solute advection with fluid flow.
A four-year plan has been established to accomplish these objectives, including thetarget of ten publications on international journals.

9. List of Collaborative Research Progress:Publication(s)1. Zhao Z., Li B. and Jiang Y. (2013) Effects of fracture surface roughness on
macroscopic fluid flow and solute transport in fracture networks. Rock Mechanics andRock Engineering. Doi: 10.1007/s00603-013-0497-1.
2. Li B. and Jiang Y. (2013) Quantitative estimation of fluid flow mechanism in rockfracture taking into account the influences of JRC and Reynolds number. Journal ofMMIJ. Vol. 129. pp.479-484. (in Japanese)

Conference Presentation(s)Jing L., Koyama T., Zhao Z. & Li B. (2013) Stress and shear effects on fluid flow
and solute transport in rock fractures (Keynote lecture). In: Proc. of Sinorock2013,
Shanghai, China, pp.33-44.