Acta Polytechnica CTU Proceedings


DOI:10.14311/APP.2020.29.0017
Acta Polytechnica CTU Proceedings 29:17–24, 2020 © Czech Technical University in Prague, 2020

available online at http://ojs.cvut.cz/ojs/index.php/app

GEOTECHNICAL ANALYSIS OF TRANSFORMING A WATER
MANAGEMENT STRUCTURE TO A TRANSPORTATION

STRUCTURE

Ivan Slávik∗, Ľuboš Hruštinec

Slovak University of Technology in Bratislava, Faculty of Civil Engineering, Department of Geotechnics,
Radlinského 11, 810 05 Bratislava, Slovakia

∗ corresponding author: ivan.slavik@stuba.sk

Abstract.
This paper analyzes the transformation of the culvert channel under the supply channel of the

Gabčíkovo Waterworks into a road tunnel structure and the impact this had on the surrounding rock
environment. It presents the engineering-geological conditions in the area, the current structural-
material characteristics of the culvert channel and its proposed transformation into a road tunnel. The
results of the geotechnical analysis, realized through numeric modelling, are presented as a comparison
of deformation changes in the rock environment with respect to changes in loading states corresponding
with functional changes in the analyzed culvert.

Keywords: Culvert channel, deformation analysis, loading state, quaternary gravels, settlement,
supply channel.

1. Introduction
During construction work on the supply channel of
the Gabčíkovo Waterworks, a culvert channel was
built under the supply channel, situated at 4.0 km.
The culvert channel is used to drain seepage waters of
the Hrušov reservoir captured by the left-side seepage
channel under the supply channel. The captured seep-
age waters, from both left-side and right-side seepage
channels, are drained together into the Danube river
branches. The position of the culvert channel under
the supply channel is shown in Fig. 1.

Figure 1. Position of the culvert channel under the
supply channel

The culvert channel has been designed for a max-
imum flow rate of 60 m3.s−1, while the passage of
such a volume of water is provided by five rectan-
gular openings with dimensions 4.5 m × 2.2 m, as is
shown in Fig. 2. The sixth opening, 2.0 m × 2.2 m,
serves as a communication passageway that contains
infrastructure.

As early as during the design stage of the projected

Figure 2. Cross-section of the culvert under the
supply channel at km 4.0 [1]

waterworks, it was presumed that seepage into the
left-side channel would decrease over time due to col-
matation of the subsoils of the Hrušov reservoir and
that three openings of the culvert channel would be
sufficient to pass the captured seepage waters. For
this reason, an alternative use of two openings for
other than passage of seepage waters has been con-
sidered. The flow rates measured during operation of
the seepage channels and the culvert channel situated
at 4.0 km under the supply channel of the Gabčíkovo
Waterworks in 1994 – 2016 confirmed the possible use
of two openings for another purpose. Based on the
above, an alternative use of part of the culvert channel
has been considered as a road transportation structure
for permanent connection of communities divided by
construction of the supply channel of the Gabčíkovo
Waterworks. The analysis of reliability risks for use
of this water management structure as a road tun-
nel structure included geotechnical assessment of the
culvert channel.

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http://dx.doi.org/10.14311/APP.2020.29.0017
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Ivan Slávik, Ľuboš Hruštinec Acta Polytechnica CTU Proceedings

2. A structural engineering
solution of the culvert
channel

The culvert channel consists of inlet and outlet sec-
tions, which include sluice mechanisms and regulatory
gates, and the middle section consists of the culvert
tunnel. The overall length of the culvert channel is
715 m, with the middle section representing 499.74
m and the remaining length being represented by the
inlet and outlet sections. The middle section of the
culvert channel consists of a total of twenty separate
dilatation units (D1 to D20), each 19.6 m long, with
average width of 30.9 m, and seven dilatation units
under the safety dams of the supply channel (3 under
the left dam – A1, B1, C1 and 4 under the right dam
– C2, B2, E, F), 12.0 to 19.6 m long, with an average
width of 31.2 m. A longitudinal section of the culvert
channel is shown in Fig. 3.

Figure 3. Longitudinal-section of the culvert channel
under supply channel in km 4.0 [1]

The structure of the culvert channel is a framed
reinforced concrete structure comprising 27 blocks,
which is made of impermeable concrete with classifi-
cation at least C 35/45, strengthened with 10 425 (V)
reinforcing steel. At the points of contact between the
blocks, dilatation joints were made, 20 mm wide with
inner sealing around each opening of the culvert chan-
nel. The structure of the culvert channel is isolated
and the surface of backfill over the ceiling is made of
sealing clay.

3. Geological conditions at the
area of interest

The geological environment in the study area is com-
posed of fluvial deposits of quaternary age reaching
a thickness circa. 250 m [2]. This was successively
accumulated in the Gabčíkovo-Győr depression of the
Danube Basin as a result of a neotectonic basin in-
version [3]. The strata consist mostly of gravelly and
sandy-gravelly channel-fill facies of the Danube and
Western Carpathian rivers and were accumulated in
braiding depositional settings. The deposition in high
sediment supply and low accommodation rate condi-
tions caused a low content of sandy, silty and clayey
layers [2]. An exception is given by the uppermost few
meters of the basin fill, which were deposited during
the Holocene as floodplain, mostly silty and clayey
facies of the meandering Danube [4].

To characterize the geological conditions of the sub-
soil at the culvert channel location, we have assessed
the geological survey [5] made in 1978 for construction
of the culvert channel. Survey drills DKP 8 – DKP 12
were carried out for the culvert channel. Besides this,
information on the geological condition was supple-
mented by older survey works VK 390, VK 391 and
HVK 23, carried out in the past. Depths of all survey
work were within 15.0 m with the sole exception of the
HVK 23 survey, which was 30.0 m deep. The survey
works were located at the axis of the culvert channel
situated at 4.0 km. Within the examined depth of 15
– 30 m, the subsoil of the culvert channel is formed
exclusively by quaternary sediments, which can be
classified into three groups:

• surface layer of loamy sands or sandy clay soils 0.5
– 1.3 m thick;

• transition layer between surface fine-grained soils
and gravelly soils of sands with loamy and clay
ingredients;

• underlying gravel layer with 10 – 60% of sandy
ingredient where sandy or less sandy gravel positions
are alternating and mutually interlocked.

The full scope of the culvert channel’s footing bot-
tom is situated within the quaternary gravel position.
From the geotechnical point of view, the quaternary
gravel layer, located under the footing bottom of the
culvert channel is critical for analysis of the reliability
risks of the culvert channel situated at 4.0 km under
the supply channel of the Gabčíkovo Waterworks and
its use as road tunnel. According to the survey results
[5], the quaternary gravels can be characterized as
well-graded (GW – G1) or poorly graded (GP – G2)
gravels. The range of granular composition of the
gravelly soil samples taken from the culvert channel
subsoil is shown in Fig. 4.

Figure 4. Range of grain size distribution of quater-
nary gravel subsoil

Further properties of the quaternary gravels of the
culvert channel subsoil, described in the survey [5],
are as follows:

• relative density: medium dense;
• deformation parameters:

. β = 0.83; Pisson’s ratio ν = 0.25;

. Edef = 50 MPa – for depths 0.0 – 5.0 m;

. Edef = 100 MPa – for depths 5.0 – 30.0 m;

. Edef = 114.5 MPa – for depths 30.0 – 90.0 m;

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vol. 29/2020 Transformation of water management structure

Figure 5. Engineering geological profile of subsoil [1]

• effective parameters of shear strength:
ϕef = 38◦; cef = 0.0 kPa;

• filtration coefficient: kf = 3.37 × 10−3 m.s−1.

Location of the survey works with an indication of
the axes of the right-side and the left-side dam of the
seepage channels, as well as the axis of the supply
channel and the culvert channel axis, are presented
alongside the geological profile of the culvert channel
axis and with an indication of the culvert channel’s
footing bottom position in Fig. 5.

At the time of the survey work [5], the groundwater
level was encountered at 3.0 – 7.5 m underground.
Subsoil in the area of interest is made of permeable
quaternary gravelly sediments, which implies that be-
fore the culvert channel was constructed, the ground-
water level was interconnected with the Danube. The
culvert channel body was built is a sealed excavation
pit. This fact can also affect the dependence of the
groundwater level, and especially its fluctuations, on
the Danube’s water level.

4. Deformation analysis of the
construction with current and
new proposed operation of the
culvert channel

Deformation analysis of the complex interaction prob-
lem of construction, along with both current and new
proposed operation of the culvert channel was carried
out based on assumptions of the theory of flexible
half-space. Interaction calculations used the numeri-
cal finite element method (FEM). The task was solved
as planar using the computational software GEO5 –
FEM module.

In the computational models, soil characteristics of
the culvert channel’s subsoil were considered based

on evaluation of geological conditions in the area of
interest verified by all survey works [5]. Definition
of deformation properties of the gravelly subsoil re-
spected the discontinuous anisotropy, i.e. changed
(increased) deformation modulus 5.0 m underground.
The computations considered the original groundwater
level 3.0 m below the original ground level. Character-
istics of reinforced concrete culvert channel structures
were considered based on results of the “Diagnostics
of Concrete Structures” carried out within a separate
part of this task. Characteristics of the subsoils and
structural elements of the culvert channel used in the
geotechnical calculations are listed in Tab. 1.

Deformation calculations were carried out in a cross
profile under the supply channel, a cross profile under
the crown of a safety dam (within the axis of the dam
crown), and in a longitudinal profile under the dam
and the supply channel for two stages. Stage No. 1
represented excavation of the pit for the culvert chan-
nel structure and Stage No. 2 represented construction
and operation of the culvert channel. Considering the
extensive amount of achieved computational outputs,
this paper will only present the results of deformation
calculations in the longitudinal profile under the sup-
ply channel for Stage No. 2 representing construction
and operation of the culvert channel.

Loading states, representative for assessment of the
reinforced concrete structure of the culvert channel
and geotechnical calculations, were defined for the
Stage No. 2, representing construction and operation
of the culvert channel, as follows:

• Loading state 0 (LS0): represents the original
state (effective stress in the subsoil after the exca-
vation and construction of the sealed excavation
pit) used as reference for comparison of the loading
states that provide a model of stepwise construction

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Ivan Slávik, Ľuboš Hruštinec Acta Polytechnica CTU Proceedings

Table 1. Properties of subsoil and structural elements of the culvert [6]

of structural elements of the culvert channel and
its current and new proposed operation.

• Loading state 1 (LS1): LS0 + realization of
reinforced concrete culvert channel under the supply
channel and the safety dam.

• Loading state 2 (LS2): LS1 + realization of
backfills and rock cover over the culvert channel
and in the safety dam area.

• Loading state 3 (LS3): LS2 + filling of all five
culvert channels by water + water pressure from the
water level in the supply channel at the minimum
(operational) level altitude (128.2 m) + uplift of
water from the water level in the left and right
seepage channels at the operational level altitude
(120.63 m).

• Loading state 4 (LS4): LS2 + filling of all five
culvert channels by water + water pressure from the
water level in the supply channel at the maximum
(flood) level altitude (131.1 m) + uplift of water
from the water level in the left and right seepage
channels at the flood level altitude (123.32 m).

• Loading state 5 (LS5): LS2 + filling of three
culvert channels by water + water pressure from the
water level in the supply channel at the minimum
(operational) level altitude (128.2 m) + uplift of
water from the water level in the left and right
seepage channels at the operational level altitude
(120.63 m).

• Loading state 6 (LS 6): LS2 + filling of three
culvert channels by water + water pressure from the
water level in the supply channel at the maximum
(flood) level altitude (131.1 m) + uplift of water
from the water level in the left and right seepage
channels at the flood level altitude (123.32 m).

The aforementioned overview of the loading states
implies that the loading states 3 and 4 provide a model

of parallel operation of the culvert channel with all its
five channels filled at minimum (operational) water
level and maximum (flood) water level. Loading states
5 and 6 provide a model of the new proposed operation
of the culvert channel with three channels filled and
the emptying of the other two channels (pumping off
the water) of the culvert channel for road tunnel use
at the minimum (operational) water level and at the
maximum (flood) water level.
The results of the calculation modelling the con-

struction and operation of the culvert channel in its
longitudinal profile under the supply channel have
implied the following:
• The effects of construction of the reinforced con-
crete culvert channel (LS1) resulted in maximum
settlement of footing bottom smax = 17.6 mm.

• The effects of culvert channel construction and re-
alization of backfills and rock cover of the culvert
channel (LS2) (floor of the supply channel and body
of the earth embankment) resulted in maximum set-
tlement of footing bottom smax = 50.1 mm.

• The effects of culvert channel construction, real-
ization of backfills and rock cover of the culvert
channel and filling of 5 channels of the culvert chan-
nel by water at minimum water level in the supply
channel (LS3) resulted in maximum settlement of
footing bottom smax = 47.9 mm.

• The effects of culvert channel construction, real-
ization of backfills and rock cover of the culvert
channel and filling of 5 channels of the culvert chan-
nel by water at maximum water level in the supply
channel (LS4) resulted in maximum settlement of
footing bottom smax = 46.1 mm.

• The effects of culvert channel construction, real-
ization of backfills and rock cover of the culvert
channel and filling of 3 channels of the culvert chan-
nel by water at minimum water level in the supply

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vol. 29/2020 Transformation of water management structure

Figure 6. Isosurfaces of deformations for loading state LS3 – longitudinal profile of the culvert [6]

Figure 7. Isosurfaces of deformations for loading state LS4 – longitudinal profile of the culvert [6]

Figure 8. Isosurfaces of deformations for loading state LS5 – longitudinal profile of the culvert [6]

Figure 9. Isosurfaces of deformations for loading state LS6 - longitudinal profile of the culvert [6]

channel (LS5) resulted in maximum settlement of
footing bottom smax = 41.2 mm. Relative change
due to pumping off the water out of two channels
of the culvert for the planned use (transportation)
resulted in a maximum rise of the footing bottom
smax = − 6.9 mm.

• The effects of culvert channel construction, real-
ization of backfills and rock cover of the culvert
channel and filling of 3 channels of the culvert chan-
nel by water at maximum water level in the supply
channel (LS6) resulted in maximum settlement of
footing bottom smax = 42.0 mm. Relative change
due to pumping off the water out of two channels

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Ivan Slávik, Ľuboš Hruštinec Acta Polytechnica CTU Proceedings

Figure 10. Deformations resulting for loading state LS2–LS6 – longitudinal profile of the culvert [6]

Figure 11. Comparison of measured and calculated deformations for loading state LS2 – LS6 – longitudinal profile
of the culvert [6]

of the culvert for the planned use (transportation)
resulted in maximum rise of the footing bottom
smax = − 9.6 mm.

The resulting deformation values from the numerical
calculations for Stage No. 2 are presented as deforma-
tion isoplanes for the loading state 3 in Fig. 6, loading
state 4 in Fig. 7, loading state 5 in Fig. 8 and load-
ing state 6 in Fig. 9. For comparison of deformation
magnitudes in the respective loading states, deforma-
tion values are graphically evaluated for representative
points of the culvert channel’s footing bottom in the

longitudinal profile in Fig. 10. Besides the resulting
deformations for the loading states 3 to 6, Fig. 10
also presents deformations resulting from the loading
state 2, which represents construction of the culvert
channel before putting the supply channel and the
actual culvert channel into operation, that is without
water in the culvert channel and in the supply channel.
Results of deformation calculations are presented in
Fig. 6 to Fig. 10 for a half length of the culvert channel
in longitudinal direction because the computational
model also made use of the symmetry in the critical
section of the culvert channel.

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vol. 29/2020 Transformation of water management structure

5. Comparison of measured and
calculated deformations

During technical safety supervision, the structure of
the culvert channel was subject to measurements of
deformation in 11/1996 and in 11/2006 [7]. These
measurements were used as a reference for comparison
of the calculated deformation values for respective
loading states. Comparison of measured and calcu-
lated deformations in the longitudinal direction of the
culvert channel for half of the longitudinal profile is
shown in Fig. 11.

6. Conclusions
The results of measured deformation values presented
in Fig. 11 provide general information on the magni-
tude and distribution of subsoil deformations under
the culvert channel in the longitudinal direction trig-
gered by operation of the culvert channel as a water
management structure. The results of calculated de-
formation values presented in Fig. 11 provide general
information on the magnitude of deformation trig-
gered by change in the culvert channel operation –
part of the water management structure to be trans-
formed into a transportation structure. Additionally,
Fig. 11 also indicates the considered uplift effect of
water on the floor of the culvert channel. Measured
deformation values are within the range of calculated
deformations considering the uplift effect of water on
the culvert channel’s floor depending on the maxi-
mum or operational water level in the supply channel
and deformations not considering the uplift effect of
water on the culvert channel’s floor. Comparison of
the results of geotechnical calculations (LS1 to LS4)
and in situ measurements of vertical deformations of
the assessed structures implies that the measured and
calculated values are in significant agreement. Based
on observable experience, it can be assumed that the
forecast values of vertical displacement for the consid-
ered change in culvert channel use (LS5 and LS6) will
be in good alignment with reality after the proposed
changes have been implemented.

Evaluation of maximum values of the final settling
as well as values of irregular settling for the assessed
loading states of the culvert channel (LS1 to LS6) indi-
cate the possible transformation of the culvert channel
structure under the supply channel of the Gabčíkovo
Waterworks into a road tunnel structure while still
meeting the conditions for a reliable and desired state
pursuant to the European (EUROCODES) and Slovak
(STN) standards in force.

In solving the relatively complex engineering prob-
lem of the interaction of a building structure with the
subsoil, the numerical finite element method was used
the suitability of which has already been verified in
solving similar interaction problems [8], [9], [10].

Acknowledgements
This paper was supported by grant projects VEGA
1/0452/17 and VEGA 1/0412/18.

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https://doi.org/10.5593/sgem2019/1.2/S02.071

	Acta Polytechnica CTU Proceedings 29:17–24, 2020
	1 Introduction
	2 A structural engineering solution of the culvert channel
	3 Geological conditions at the area of interest
	4 Deformation analysis of the construction with current and new proposed operation of the culvert channel
	5 Comparison of measured and calculated deformations
	6 Conclusions
	Acknowledgements
	References