Hello all.
The identification of the squeezing potential of the ground is mainly based on the rock UCS, and on the height of overburden.
Is there a direct relationship between the deformation modulus of rocks and the potential of squeezing?
Thanks.
In no manner any expert on squeezing, but the following observation might be of relevance. In the integrated Qc versus P-wave velocity versus static deformation modulus model that has appeared several times since Barton, 2002, (Figure 4) it is found that a fourth 'parameter' viz. the required support pressure Pr from Barton et al. 1974 is inversely related to the deformation modulus. So very low velocity, and very low modulus correlate with very high support pressure needs (sounds and is logical?), and very high velocity, and very high moduli correlate with the need for negligible support pressure (also logical).
If by UCS you refer to intact rock strength, then this should be related to the UCS of the rock mass (σcm) in order to be meaningful. There are plenty of approaches based on Q system (e.g. Singh et al, 1992, Correlation between observed support pressure and rock mass quality, TUST, Vol.7, pp 59-74; Goel et al, 1995, Tunnelling through the young Hima;ayas - a case history of the Maneri-Uttarkashi power tunnel, Engineering Geology, Vol. 39, pp 31-44), others based on the Hoek and Brown failure criterion (e.g. Hoek and Marinos, 2000, Predicting tunnel squeezing problems in weak heterogeneous rocjk masses, T&T Int., Nov. 2000 & Dec. 2000; etc). Other authors like Prof. Kovari, Prof. Barla, Prof. Anagnostou have writen about designing for squeezing conditions. At the end of the day, the Modulus of Elasticity or of Deformation determines the mode of yield while the strenght of the rock mass the width of the yield zone around the tunnel. Needless to say that I agree with Dr. Barton above. May I add that predicting squeezing conditions is a difficult job so much so because there is the creep element that requires complicated analysis to estimate it. Some authors propose Visco Elastic and Visco Plastic models to account for creep (e.g. Sterpi & Gioda, 2009, Visco-Plastic Behaviour around Advancing Tunnels in Squeezing Rock, R.M.R.E., Springer, Vol 42-2, pp 319-339. Good luck in your difficult work.
Hello, Thank you for both answers, Indeed, Qc-vs-Vp-Em corelations are very logical. In some rock types (shales and shales), we can obtain medium to high UCS with a low modulus of deformation (large deformation without shear). The problem is exactly the prediction of the behavior and the evolution towards the shear, and the deformation module is an important factor (certainly with many others). Very difficult to predict the results to get ... Thank you.vs-
I think the effect of squeezing more to do with the structural strength of the soil. In accordance with the mechanism of formation of landslides extrusion, the criterion of the possibility of development of deformation is to compare the structural strength (σстр.) soil and vertical pressure on the layer.
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