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backanalysed to fit the displacement ratio. To represent the real
excavation and monitoring procedure, displacements were reset
in simulations once the adit face passed the monitored section.
They are thus not biased by the pre-convergence displacements,
which are not registered by the rod dilatometers. Evaluation of
horizontal displacements in the monitored section is
demonstrated in Fig. 4.
Boháč, J., Feda, J., Herle, I. and Klablena, P. (1995), Properties of
fissured Brno Clay. Proc. 11th Eur. Conf. Soil Mech. Fndn. Eng.,
Copenhagen, 28 May - 1 June, Danish Geotechnical Society,
Bulletin No. 11, Vol. 3, 19-24.
Burland, J.B. and Maswoswe, J. (1982) Discussion on „In situ
measurements of horizontal stress in overconsolidated clay using
push-in spade-shaped pressure cells“. Géotechnique 32, No. 2, 285-
286.
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determination of initial state of stress in a rock mass and the finite
element method (in Czech). MS, Report of Hydroprojekt, Praha,
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Doran, I.G., Sivakumar, V., Graham, J. and Johnson, A. (2000)
Estimation of in situ stresses using anisotropic elasticity and suction
measurements. Géotechnique 50, No. 2, 189-196.
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calculation. Academia Prague.
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soil anisotropy and K0 on ground surface movements resulting
from tunnel excavation. Geotechnique, 55(3), 189–199.
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0
for
overconsolidated clays. Can. Geotech. J. 28, 650-659
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situ evaluation of K
0
in eastern Canada Clays. Canadian Geotech. J.
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Figure 4. 3D model geometry and predictions of horizontal
displacements.
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Results of backanalyses are summarized in Table 2. It is
clear that the 2D and 3D analyses were consistent in the
estimation of K
0
(1.37 and 1.45 respectively). The 3D analyses
overpredicted the displacement magnitude.
Lefebvre, G., Bozozuk, M., Philibert, A. and Hornych, P. (1991)
Evaluating K0 in Champlain clays with hydraulic fracture tests,
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ASCE, Vol. 106, NoGT3, 299-321.
Mašín, D. (2005). A hypoplastic constitutive model for clays,
International Journal for Numerical and Analytical Methods in
Geomechanics, 29, No. 4, 311-336.
Table 2. Results of numerical backanalysis of circular exploratory adit.
monitoring
2D model
3D model
horiz. conv.
(u ) [mm]
h
19.8
19.8
33.4
vert. conv.
(u ) [mm]
v
15.9
15.4
26.1
Ratio u /u
v
h
1.25
1.25
1.28
K
0
-
1.37
1.45
Mašín, D. (2012). Clay hypoplasticity with explicitly defined
asymptotic states. Acta Geotechnica (in print; doi: 10.1007/s11440-
012-0199-y).
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0
-OCR relationships in soil. J.
Geotech. Eng. Div. ASCE, GT6, 851-872.
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rest. Canadian Geotech. J. 30(4), 647-666.
Similarly to Sec. 4, it is expected that the results obtained are
negatively influenced by inaccurate representation of soil
anisotropy using the hypoplastic model. The development of the
new model is ongoing.
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279–299.
6
CONCLUSIONS
In the paper, we summarized different methods for
evaluation of the earth pressure coefficient at rest K
0
. Due to
limitations of different methods, it is always advisable to
combine different approaches based on laboratory investigation,
field measurements and numerical analysis. Several results of
the K
0
evaluation of the Brno Clay were presented, in all cases
leading to K
0
higher than unity. These analyses are preliminary
and they will be adjusted in the forthcoming work.
Pavlík, J., Klímek, L., Rupp, O. (2004). Geotechnical exploration for
the Dobrovského tunnel, the most significant structure on the large
city ring road in Brno. Tunel 13(2), 2-12.
Sivakumar, V., Navaneethan, T., Hughes, D. and Gallagher, G. (2009)
An assessment of the earth pressure coefficient in overconsolidated
clays. Géotechnique 59, No. 10, 825-828.
Skempton, A.W. (1961) Horizontal stresses in an over-consolidated
Eocene clay. Proc. 5th ICSMFE, Vol. 1 351-357.
Svoboda, T., Mašín, D. and Boháč, J. (2010) Class A predictions of a
NATM tunnel in stiff clay. Computers and Geotechnics 37(6), 817-
825.
Svoboda, T. and Mašín, D. (2011). Comparison of displacement fields
predicted by 2D and 3D finite element modelling of shallow
NATM tunnels in clays. Geotechnik 34(2), 115-126.
7
ACKNOWLEDGEMENTS
The financial support by the grants P105/11/1884 and
P105/12/1705 of the Czech Science Foundation, and by the
grant MSM0021620855 is gratefully acknowledged.
Tedd, P. and Charles, J.A. (1981) In situ measurements of horizontal
stress in overconsolidated clay using push-in spade-shaped pressure
cells. Géotechnique 31, No. 4, 554-558.
Wang, S.Y., Sun, L., Au A.S.K., Yang, T.H, and Tang, C.A. (2009) 2D
numerical analysis of hydraulic fracturing in heterogeneous geo-
materials. Construction and Building Materials 23, 2196-2206.
8
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