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 many geoscienceand geo-engineering disciplines. Many outstanding issues need to be investigated to enhance theknowledge on this subject, specifically more in-depth research in testing and modeling of thecoupled processes in rough rock fractures and intersections of rock fractures is needed. This
collaborative research focuses on this subject, which is especially important for infrastructuredevelopment, safety assessment of energy facilities and geothermal energy exploitation (GED).
This research aims at solving two important problems met in geo-engineering: a) fast closuresof 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 the macroscopic scales offracture networks. For the first problem, we modeled numerically the asperity deformation andfailure processes during initial normal loading, by adopting both elastic and elastic-plastic
deformation models for the asperities on a real rock fracture with measured surface topography
data, and estimated its impact on initial conditions for fluid flow test performed underlaboratory conditions. The results showed that 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 thedamages 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 roughness of rockfractures. 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 solutetransport behavior in different macroscopic direction may be significantly different, but thedifference 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 are planning tocontinue the collaboration.

8. Deployment Plans for Future Collaborative Research:
The previous collaborative research focused on stress effect on fluid flow of rough rockfractures, with simple tracer tests considering only solute advection, under room temperature.
The research now needs to be extended to consider deformation, damage and failure ofcontacting asperities of rock fractures and their effects on transport mechanisms, especially theshearing, cracking and crushing of contacting asperity tips, where local stress concentration ismuch higher and reactive transport processes most active.
In the future studies, a comprehensive lab testing and mathematical model development (inNagasaki University), and numerical simulations (in KTH) for contact mechanics of rockfractures during normal loading will be carried out. Based on the knowledge obtained from thecontact mechanics research, tests on fluid flow and solute transport will be conducted without
shear, with the aim of quantitative model establishments for: a) evolution of fluid flow
channeling and flow field distribution with loading; b) processes of different solute transportmechanisms of stress solution of minerals at contacting asperities, solute sorption on fracturesurfaces, and diffusion in the rock matrix; c) solute advection with fluid flow.
A four-year plan has been established to accomplish these objectives, including the target often 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 and Rock Engineering. Doi:
10.1007/s00603-013-0497-1.
2. Li B. and Jiang Y. (2013) Quantitative estimation of fluid flow mechanism in rock fracture
taking into account the influences of JRC and Reynolds number. Journal of MMIJ. 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 andsolute transport in rock fractures (Keynote lecture). In: Proc. of Sinorock2013, Shanghai,
China, pp.33-44.