I am deriving a relationship between RQD and hydraulic conductivity in discontinuous sedimentary rocks. Aperture of the discontinuity is a very important parameter to include in the relationship. Can anyone suggest, how to proceed with it?
Yes, there is relationship of aperture of joints with overall hydraulic conductivity. First of all, as you may know that the cubic law explains relationship between aperture and conductivity of simple joint model. If apertures of joints are big then certainly hydraulic conductivity of rock mass will be high. However, we need some more information, such as number of joint sets, orientations of joint sets, characteristics of each joint sets(filling, roughness, tortuoucity, etc...).
Once we have all those information, one of candidate methods is we generate joint networks and simulate the flow through joints. We may or may not consider hydraulic conductivity of rock matrix during the simulation. Once we have result of flow through network, then we can back calculate the rock mass hydraulic conductivity K = flowrate (q) /hydraulic gradient (i). Hydrogeology is one of my favorite topic, although I am geomechanics major.
The topic is quite interesting. If you need collaboration, then please let me know. I will be happy to join.
Thanks,
Myung Kyu Song.
I just know the cubic law and I already used to calculate the area of fracture surfaces exposed to percolating water, with good results (Pacheco and Alencoão, 2006, Journal of Hydrology; Pacheco and Van der Weijden, 2014a,b, Journal of Hydrology)
you can refer to the special issue of Rock Mechanics and Rock Engineering
Volume 47, Issue 3, May 2014
Special Issue: Water Issues in Underground Excavations
ISSN: 0723-2632 (Print) 1434-453X (Online
Hi, check the attached file , you might find an answer to your question. Regards
The fractured masses often have a fill material compressed amid the joints. Such rock masses may be classified as permeating rock masses. Few related issues are addressed in the following freely downloadable paper;
DOI:http://www.icevirtuallibrary.com/content/article/10.1680/envgeo.13.00043
Regards
In fact the hydraulic conductivity in fractured media is function of the hydraulic head. If the head is lowered, the neutral stresses decrease, the effective stresses increase, the fractures close and consequently the hydraulic conductivity decreases. You can check this reasoning in my Ph.D. thesis at Colorado School of Mines, 1971.
Reiss, L.H., 1980. The reservoir engineering aspects of fractured formations. Editions
Technip 27 Rue Ginoux 75737. Cedex, Paris, p. 15.;
Chen et al., 2012. Characteristic of anisotropic coal permeability and its impact on optimal design of multi-lateral well for coalbed methane production, Journal of Petroleum Science and Engineering s 88–89:13–28.
Drilling direction has a great effect on RQD , or in other words, RQD varies greatly from different orientations of fractured rock mass, and RQD is mostly used in the stage of geotechnical engineering reconnaissance, while the hydraulic conductivity is almost stable for a specific rock mass, so i wonder how will you tackle the varied RQD from different directions with mostly certained hydraulic conductivity?
I recommend a paper I'm currently reading; it is excellent and closely related to the question posted. It focuses on hydromechanical (stress-related) factors but it also reviews (briefly) geometry-related factors (such as aperture), pointing out that these are coupled, interdependent factors.
Article Investigating the Role of Hydromechanical Coupling on Flow S...
For this problem, there are several solutions ussualy taking in account aperture of joint sets and joint spacing. I can mention Vangham method, Lois method etc. For example Vangham method can help in calculation of permeability coefficient k and effective porosity for each joint set. RQD in my opinion is a parameter that cannot help,you a lot in this problem.Here, Yaman answer lead you well on possible problems. If necessary, I can send you some formulas about this problem.
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