Acta Polytechnica CTU Proceedings


doi:10.14311/APP.2017.10.0034
Acta Polytechnica CTU Proceedings 10:34–37, 2017 © Czech Technical University in Prague, 2017

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

FIBER REINFORCED SAND BACKFILL FOR UNDERGROUND
PEDESTRIAN CROSSING

Andrey B. Ponomarev∗, V.I. Kleveko, O.V. Moiseeva,
K.R. Kashapova

Perm National Research Polytechnic University, Kuibysheva street 109, Perm, Russia
∗ corresponding author: spstf@pstu.ru

Abstract. Crosswalk is an essential element of the transport system of any city. A priority assignment
in any such crossing is to ensure the safety of pedestrians. Underground pedestrian crossings are much
safer than crossings at another level, but they lose in attraction when it comes to cost. The cost of the
construction of an underground pedestrian crossing often leads to project abandonment. The cost of
construction can be reduced through the use of flexible corrugated metal structures instead of ordinary
concrete structures. The stress-strain state of the structural shells need to be known to facilitate their
rational design.

The stress-strain state of flexible corrugated metal shells largely depends on the strength and
deformation characteristics of the surrounding soil. Therefore, improving the characteristics of backfill
soil is an urgent task in reducing the cost of construction for such tunnels.

One way to improve the strength and deformation characteristics of soils is the use of reinforcement.
Currently, there are a large number of reinforcement schemes and also associated reinforcing materials.
One of the most prospective methods of soil reinforcement is the use of fibre filaments. Fibre reinforced
soils have significantly higher strength and deformation characteristics in comparison with unreinforced
soils.

Numerical modelling of a tunnel shell made out of a corrugated metal structure was undertaken
to evaluate the effectiveness of using fibre reinforced sand. Ordinary sand and sand reinforced with
polypropylene fibres have been used as soil backfill.

The calculation results for a pedestrian tunnel structure involving different strength and deformation
characteristics of the backfill soil are presented in this article.

Keywords: Fibre reinforced soil, FEM, tunnel lining.

1. Introduction
Crosswalk is an integral element of the transportation
system of any city. The first and foremost function
of a pedestrian crossing is user safety. Annually, in
Russia, a large number of people travelling on foot
are killed, which indicates some lack of effectiveness
in the transfer and transport system as a whole [1, 2].
The most commonly used and the most projected

type is a pedestrian crossing with a light regulation of
type “Zebra”. This type of transit actually maximises
the probability of pedestrian-car contact.
Underground pedestrian crossings offer a signifi-

cantly safer transit to light regulation, but lose on the
cost criterion. This cost of construction often leads
to abandonment of the concept. However, the cost
of construction can be reduced through the use of
corrugated metal structures instead of the standard
concrete shell [3–6].

To reduce the earthworks and consequently the cost
of construction, the pedestrian tunnel is laid at the
ground-level for traffic vehicles and in this case is
carried out using the device of the mound (Fig. 1).

Earlier studies showed that the optimal cross section
is a round pipe [6].

The stress-strain state of flexible metal corrugated
shells largely depends on the strength and deformation
characteristics of the surrounding soil [7, 8]. There-
fore, the characteristics of the soil backfill gives an
actual opportunity to reduce the cost of construction
of pedestrian tunnels.

One way to improve the strength and deformation
characteristics of soils is the use of reinforcement.
Currently, there are a large number of schemes for
reinforcement and their related reinforcing materials.

2. Fibre reinforced sandy
backfill

One of the most promising ways of reinforcement
of soils is using fibre. Fibre reinforced soils have a
significantly higher strength characteristics compared
to unreinforced soils [9–12].

Fig. 1 shows the structure of the pedestrian crossing
at ground level. This design of pedestrian crossing
does not need light regulation, and thus saves time for
drivers and pedestrians, requires less effort compared
to aboveground and underground pedestrian crossings
and generally serves to enhance the safety of all road
users.

34

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vol. 10/2017 Fiber Reinforced Sand Backfill

Figure 1. The construction of a pedestrian crossing at ground level

Figure 2. A round pipe

Figure 3. Specifications of corrugated sheet GL 55

To identify the optimal soil backfill there was cal-
culation by the finite element method, implemented
in the software package PLAXIS 2D.

The construction of a pedestrian crossing at ground
level was made for specific geological conditions. At
the construction site there were identified the following
primers:

• loam, layer thickness h = 7.2 m, intercept cohesion
c = 20.5 kPa, angle of internal friction ϕ = 18°,
modulus of deformation E = 11 MPa;

• sand, h = 1.0 m, c = 2 kPa, ϕ = 18°, E = 11 MPa;
• gravel, h = 1.8 m, c = 1 kPa, ϕ = 40°, E = 30
MPa;

• mudstone, h = 2.1 m, E = 20 MPa.

Fig. 2 shows the geometrical dimensions of a metal
corrugated pipe.
In the pipe there was used corrugated sheet GL55

(Fig. 3), which had the following characteristics:

• thickness - 4 mm;
• the moment of inertia of the cross section I -

181.92 cm4/m;

Figure 4. Design scheme

• the moment of resistance of section W -
61.67 cm3/m;

• the plasticity moment of resistance of section Wp -
79.72 cm3/m.

The most common soil backfill for underground
structures is sand. Therefore, to evaluate the influence
of soil characteristics on the stress-strain state of the
shirred casing, two calculations were done. The first
calculation was derived from a filling with sand with
the following characteristics: E = 30 MPa; ϕ = 40°;
C = 1 kPa. The second calculation was made for
the filling out of fibrocartilagenous sand with the
following characteristics: E = 30 MPa; ϕ = 45°;
C = 67.0 kPa. The characteristics of sand reinforced
with polypropylene fibres to an amount of 0.5 % is
taken from test results given in [9–12].
According to the current design standard SP

35.13330.2011 “Bridges and pipes”, the cargo load was
a four-axle truck N14 with an axle load of 252 (kN),
and the distance between the axles 1.2 m.
The design scheme is shown in Fig. 4. The results

of calculating the stress-stain state of the tunnel lining
with soil backfill are in Figs. 5, 6, 7 and 8.

Analysis of the graphs showed that in the tunnel
lining there occurs compressive strength with a maxi-
mum value of Nmax = 147.87 kN and a considerable
alternating bending moment with a maximum value

35



A. B. Ponomarev, V.I. Kleveko, O.V. Moiseeva, K.R. Kashapova Acta Polytechnica CTU Proceedings

Figure 5. Deformed scheme

Figure 6. The diagram of shell displacements for
sand backfill (umax = 29.32 mm)

of Mmax = 6.5 kNm. The maximum displacement of
the tunnel lining was observed in the upper zone and
amounted to 29.32 mm.

The results from calculating the stress-strain state
of the tunnel lining and soil backfill from fibroareolar
sand is shown in Figs. 9, 10 and 11.

Based on the calculation results the following data
was obtained:

• max. travel: Imax = 20.71 mm;
• max axial force Nmax = 164.28 kN;
• max bending moment Mmax = 3.78 kNm.

The analysis of the above plots shows that using
fibre reinforced soil instead of unreinforced soil leads
to a decrease of the deformations of the tunnel shell by
8.6 %, a bending moment at 42 % and to an increase
in longitudinal force of 9.7 %.

Based on the obtained calculation results there were
calculated the normal stresses in the metal corrugated
shell. The calculation results are presented in Figs. 12
and 13.
The analysis of these plots shows that the normal

stresses in a metal enclosure when using the filling
out fibre reinforced soil is much less than for soil that
is unreinforced.

Figure 7. The diagram of axial force for sand backfill
(Nmax = 147.87 kN)

Figure 8. The diagram of bending moment for sand
backfill (Mmax = 6.5 kNm)

Figure 9. The diagram of shell displacements for
fibre reinforced sand backfill (umax = 20.71 mm)

Figure 10. The diagram of axial force for fibre rein-
forced sand backfill (Nmax = 164.28 kN)

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vol. 10/2017 Fiber Reinforced Sand Backfill

Figure 11. Bending moment diagram for fibre rein-
forced sand backfill (Mmax = 3.78 kNm)

Figure 12. Stress diagram for sand backfill (σmax =
105.39 MPa)

3. Conclusions
(1.) Using fibre reinforced soil can improve the
strength and deformation characteristics of the soil
backfill corrugated metal tunnel lining, which leads
to a significant reduction of stresses and strains in it.
Stress was reduced by 42 %, and the deformation
by 8.6 %.

(2.) The results of the calculations showed that im-
provement of the mechanical characteristics of the
soil backfill for the tunnel allows the use of thin-
ner corrugated sheets, which reduces the cost of
construction.

References
[1] O. Moiseeva, V. Kleveko. Analysis of accident cases
involving pedestrians in perm. PNRPU Construction
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[2] P. A. Tretyakova, V. Kleveko. Modern methods of
increasing the efficiency of urban transport systems.
PNRPU Construction and Architecture Bulletin
(1):101–108, 2012.

Figure 13. Stress diagram for fibre reinforced sand
backfill (σmax = 61.19 MPa)

[3] O. V. Moiseeva, V. I. Kleveko. Choice of a rational
type of pedestrian crossing with safety for pedestrians
and construction costs. World Science and Innovation
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[4] A. E. Polovnikova, V. I. Kleveko. Choice of a rational
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[5] O. V. Moiseeva, V. I. Kleveko. Choice of rational type
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[8] A. L. Novodzinsky, V. I. Kleveko. The account influence
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[10] A. B. Ponomarev, A. S. Kuznetsova, V. G. Ofrikhter.
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[11] A. S. Kuznetsova, V. G. Ofrikhter, A. Ponomarev.
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	Acta Polytechnica CTU Proceedings 10:34–37, 2017
	1 Introduction
	2 Fibre reinforced sandy backfill
	3 Conclusions
	References