I'm gonna model a 3D fractured media using ITASCA discrete element package "3DEC". The aim of the model is obtaining deformability modulus of the rock mass. As you know, there is no direct method to do that. So,... I wonder if anyone could present any helpful numerical or statistical way to obtain the deformability.
Thanks in advance.
as we know, deformability modulus is a property of rock which used almost in numerical analyses. you can obtain deformability modulus directly using ASTM D4394 or determine it using other indirect methods like using equation based on RMR, GSi, ....
but if the aim of your numerical analysis is to obtain deformability modulus, then you can run a back analysis model, in this method you should run several models based different deformability modulus and then compare your result with the response of ground.
excuse me for my bad English
kind Regards Saleh
Dear Saleh,
Thanks for your contribution. If you mean young's modulus... yes, it is a rock property which the software demands, or calculates automatically from another input data. But what matters is deformability modulus which changes in any direction and regarding to joint frequency, orientation, spacing,etc.
As you know, determination of deformability modulus using analytical solutions like those you mentioned will be just an approximation. I am looking for a solution which can help me to do the stuff numerically.
As you mentioned, there are some difference between Young's modulus and deformability modulus. in 1976 International society of rock mechanics (ISRM) has published the definition of Deformability modulus and young modulus;
Modulus of elasticity or young's modulus (E): The ratio of stress to corresponding strainbelow the proportionality limit of a material. and
deformability modulus (Em) ; The ratio of stress to corresponding strain during loading of a rock mass, including elastic and inelastic behaviour
today the following three type of insitu tests are mostly used to determine the modulus of deformation (Palmstrom and Singh 2001)
1- Plate jacking test (PJT)
2- Plate loading test (PLT)
3- redial jacking test (Goodman jack test)
and also there are some indirect methods for determining modulus. ( you can fined these equations in Bieniawski 1978 (Based RMR), Serafim and Pereira 1983 (Using RMR), Grimstad and Barton 1993 (based Q) and .... )
i am agree, there are some errors and uncertainty in using these methods (indirect methods) but there are some advantage in using these method like saving in time and cost. with all regard, in my opinion Em is only one of hundred parameters which we can used for creating our numerical models for predicting the ground behavior. and now i am ready to receive your answer and your opinion on the use of Em
you can find comparison between field data measurement and indirect measurement in paper titled " THE DEFORMATION MODULUS OF ROCK MASSES - comparisons between in situ tests and indirect estimates" by Palmstorm and Singh
thanks you Mr. Mazraehli for this good disscussion
Dear Saleh,
Deformability moduli are the most important parameters in dam engineering and it is why to use jacking or plate loading tests. I recommend you to refer to Amadei & Goodman (1981) and Huang et al (1995). These articles will help you have a broad vision on rock mass deformation. The study I am dealing with, comprises a wide framework in which determination of deformability of the abutments of a dam has been considered.
Wish the best.
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