Geotechnical properties and
stress-strain-time behavior evaluation
of industrial waste deposits in Bulgaria
by Prof. D-r Eng. Trifon Germanov
Department of Geotechnics

This report presents the results from some recent
studies elaborated under supervision of the author. Part
of the results under consideration are reported on the
Main Session 1 - “Man Made deposits - recent and
ancient” of the 13th European Conference on Soil
Mechanics and Geotechnical Engineering, Prague, 2003.
• The results presented in this report are published in the
Proceedings of the Conference as followed:
• Germanov, T. (2003). “Geotechnical properties of
industrial waste deposits in Bulgaria”. Proceeding XIIIth
European conference on SMGE, Prague, Vol.1, pp. 93-101.
 Germanov, T. (2003). “Limit states (Stability,
deformation, erosion….)”. Proceeding XIIIth European
conference on SMGE, Prague, Vol.3, pp. 119 - 125.
Basic consideration




The stability of waste deposits, such as tailings dam, landfill, waste
banks and other depends on the mechanical properties of the waste
materials and the shape of the deposit’s body.
The basic principles of soil mechanics are usually used for the
purpose. On the other hand, the materials included in the waste
deposits often have an unusual behavior, different from natural soils.
This circumstance requires a comprehensive program for laboratory
and in situ study for determination of the real mechanical properties
of the waste materials
Summarizing the problems, related to the stability of waste deposits,
the following limit states could be considered:
 slope stability analysis,
 bearing capacity,
 subgrade settlement and differential surface settlement,
 erosion (internal and surface).
Basic consideration



The slope stability analysis is very important problem,
mainly for the tailings dams and landfills, where a slope
failure under gravity and filtration efforts is possible.
Depending on the type of the project, different design
methods are used. If the type of the slip surface is accepted,
conventional (based on the Bishop, Jnbu or Spencer
principles) methods could be applied.
Erosion is important problem in the case of tailings, ash or
other dams built up of fine-grained materials where, after
raining, a surface slope failure is possible.
The most parts of the industrial waste deposits are in watersaturated conditions. By this reason, the effect of the pore
water pressure should be taken into account evaluating the
deposit stability.
Part 1.
Geotechnical Properties of
some industrial waste deposits
in Bulgaria
Introduction




The design of geotechnical works related to encapsulation
and stability analysis of industrial waste deposits requires
the determination of real physical and mechanical properties
of the waste material.
The Soil Mechanics principles are usually used for this
purpose.
However, taking into account the specific features of the
waste materials (short time of deposit, usually uniformly
grain size distribution, great ability for deformation), some
deviations from the standard methods for soils testing are
possible.
During the last 10-15 years an intensive program for
construction works related to the environmental protection
in Bulgaria has started.
Introduction

Part of this program is related to designing of
equipment with the purpose to encapsulation
and remediation of industrial waste deposits.
 The laboratory of Soil and Rock Mechanics at
the University of Architecture, Civil
Engineering and Geodesy took part in these
programs, mainly conducting laboratory
testing for determination of geotechnical
properties of waste materials.
Introduction






Only part of the results from laboratory testing is
presented in the here.
Three projects, developed under supervision of the
author are considered:
Encapsulation of “Blue lagoon”;
Encapsulation of the oxidative pond near the town of
Burgas;
Stability analysis of “Liuliakovitsa” tailings dam.
The waste deposits, under consideration, are situated in
different part in Bulgaria.
Encapsulation of “Blue Lagoon”





The slime pond (called “Blue Lagoon”) is situated on the territory
of the Pirdop Copper Metallurgical Plant located some 70 km to
the east of Sofia. Industrial activities on this site started in the late
1950’s.
The Blue Lagoon designates the settling pond, which contains the
calcium arsenic precipitate (slime) coming from the copper
metallurgical plant.
The northern edge of the Blue Lagoon is rather close to the SofiaBurgas railway.
The initial slime pond was constructed in 1956, mostly on the
original sloping (~ 3.5%) ground surface of alluvial soil with a
high clay content which is underlain by gneiss bedrock.
The elevation of the bedrock surface is variable.
Encapsulation of “Blue Lagoon”

Drill holes advanced to either establish the
depth to be more than 20 m below the
ground surface.
 The slime surface has an area of about 9.6
ha and the greatest depth, in 1997 was
12.70 m below the slime surface.
 The estimated total volume of the stored
sediments (slime) was about 600 000 m3.
Encapsulation of the oxidative pond near Burgas





The oxidative pond is situated near the quarter “Meden
Rudnik” (Cooper mine) in the town of Burgas.
To the west the pond is bounded by “Mandra” dam. At first,
the pond had been used as a settling basin for water supply.
During 1984 it was taken out from the scheme of the water
treatment and had been used as a site for deposit of floating
refuse products from cleaning of the other oxidative ponds.
During 1991 the free filling of the pond by mixture of
constructions refuses, sediments and ash from the ovens for
burning of petroleum and biological sediments began. As a
result of this, an area of 298 ha was filled.
Thus, the oxidative pond was formed of three parts: filled
body (swamp), settled lake, and slime field.
“Liuliakovitsa” tailings dam stability analysis




The tailings dam “Liuliakovitsa” is a part of the Assarel
cooper flotation plant, designed with an improved
construction.
Its final height will be 190 m. The starter dam, built of
draining rock fill, has a tongue-shaped projecting lower
upstream part. The length of this part is equal to the distance
from the starter dam to the decant pond at the initial stage.
It is calculated to ensure stability of the tailings dam at its
final height.
The coarser fractions are laid off in the supporting part over
the tongue, and the finer material is washed off into the
pond.
This kind of sorting makes it possible to use the good
strength of the coarse tailings deposited over the tong, as a
substitute of the rockfill.
“Liuliakovitsa” tailings dam stability analysis

The construction of the starter dam began late in
1984, and the deposition of the tailings started in
1990.
 Preliminary study for determination of consolidation
characteristics of the tailings, obtained in laboratory,
was carried out in 1987.
 Nowadays, the height of tailings dam reaches to 130 m
 Thus,
supporting starter dam of rockfill
with a lower-than-usual height is used.
Methodology of the laboratory testing

Waste materials sampling

The aim of sampling is to obtain samples for identification of
the waste materials as well as to perform laboratory testing
for determination of the geotechnical properties.
The techniques used for sampling depend on the in-situ
conditions of the settled waste materials.
Different methods for sampling are applied.
The drilling works in the Blue Lagoon were done according
to preliminary elaborated pattern of borehole net, consisting
of 32 drillings, with dimensions of gird 50m to 50 m.
A floating caisson/pontoon was used.
Sampling was done through an opening in the center of the
pontoon by means of a pipe-drilling device of 2.5 inches,
internal diameter, with jointed sections of 100 cm each.





Waste materials sampling

During the process a total of 220 m have been drilled
and 225 samples were taken.
 The samples for laboratory study were delivered in
liquid condition using plastic bottles.
 Before the beginning of the official program of
laboratory
geotechnical
study,
several
methodological compression tests were carried out.
 A similar methodology has been applied for
sampling of the refuse materials from the oxidative
pond.
Preliminary methodological compression tests of the slime
from “Blue Lagoon”







Two bottles with slime, taken from 0,5m and 4,5m depth
were used for the purpose. Both samples have
approximately uniform initial density and water content.
The following initial characteristics for the sample from
4,5m depth are determined:
water content
Wn0=205,6%;
wet density
rn0=1,185 g/cm3;
dry density
rd0=0,397 g/cm3;
void ratio
e0=5,73;
degree of saturation Sr =1,00.
Initial identification characteristics of the
refused materials form the oxidative pond

The refuse materials have a large quantity of
petroleum products.
 To decrease the effect of these products on the
geotechnical properties, a special procedure was
applied.
 At first, the refuse materials have been laid on a
filter paper and rest one day to free drying.
 After drying in the oven at a temperature of 50 - 60
С0 and after free settling, the refuse materials
showed approximately 70% soil particles and 30%
organic contents.
Initial identification characteristics of the
refused materials form the oxidative pond

The identification geotechnical characteristics in
“natural conditions” are evaluated according to
standard methods as follows:
 the bulk density in by means of direct filling of the
refuse materials in the oedometers; the water
content - drying the samples at a temperature of 50
- 60 С0;
 grain size distribution – by sieve and areometric
analysis.
 The average characteristics are given in Table 1.
Basic physical characteristics of the refuse materials
from the oxidative pond
Characteristics
1.
2.
3.
4.
5.
6.
7.
Specific gravity
Bulk density
Water content
Dry density
Void volume
Void ratio
Degree of saturation
rs
rn
w
rd
n
e
Sr
Settled Slime Swamp
lake
field
3
g/cm
1.354
1.427 1.437
g/cm3
%
g/cm3
-
0.983
580
0.145
0.892
8.335
0.941
0.985
237
0.292
0.795
3.879
0.871
0.930
279
0.245
0.827
4.811
0.826
Basic physical characteristics of tailings materials
1.
2.
3.
4.
5.
6.
7.
8.
Characteristics
Specific gravity
Bulk density
Water content
Dry density
Void volume
Void ratio
Degree of saturation
rs
rn
w
rd
n
e
Sr
g/cm3
g/cm3
%
g/cm3
-
From
2.68
1.53
4.9
1.32
0.366
0.525
0.53
To
2.78
2.06
32.0
1.78
0.528
1.12
0.99
%
%
%
14
36
13
64
80
22
Grain size distribution
 Sand
 Silt
 Clay
Determination of the mechanical properties


Oedometric tests
Two types of oedometer have been used for
compression tests:
 Oedometer without friction along the circular area
of the sample for long term consolidation tests with
one side vertical drainage.
 ELE Rowe type consolidation cells for compression
tests with radial inwards drainage
 The oedometric tests of the tailings were carried out
directly by using undisturbed samples.
Oedometric tests - “Blue Lagoon”

Taking into account that it is impossible to take
undisturbed samples of the slime and refused material
from pond “Blue Lagoon” and “Oxidative pond” and
after the conclusion that there is not great variation of
the unit weight with depth, a non-standard procedure
was applied for preparation of samples for all
oedometric tests.
 According to the approximate evaluation of density of
samples, measuring the cell volume, the required mass
of the natural slime and refused materials (mixture from
3-4 bottles) was measured.
 This mass is put into the cell, compacted uniformly, on 4
- 6 layers
Oedometric tests - results






Time - deformation properties are determined by using timedeformation curves in “log scale” mainly. The coefficients of
consolidation Cv are computed applying Casagrande’s method.
The creep indexes Cae (coefficients of secondary consolidation)
are computed by using formula:
Cae = (1 + e0)ea, where: e0- initial void ration; ea - coefficient of
secondary compression.
Initial times of creeping, t0, are computed from the log-timesettlement curves.
The coefficients of radial consolidation Cri are computed by
using square-root time curves according to BS 1377.
The average compression and consolidation characteristics are
presented in Table 3.
Triaxial tests - results

Triaxial shear tests were carried out only with slimes and
tailings samples.
 The following types of triaxial shear tests are performed:
undrained-unconsolidated (UU) and consolidated undrained
(CU) tests, with pore pressure measurement.
 After preparation of the specimen, each triaxial shear test is
carried out following the standard procedures according to
standards (ASTM D 280-95 and NF P 94-070, October 1994).
Each shear strength parameter is determined using four Mohr
circles.
 The results from UU and CU tests are presented by following
relationships: deviator stress-axial strain, pore pressure
increment – axial strain and relations t = f(s) and t’ = f(s’)
[t’=(s1-s3)/2; s=(s1+s3)/2; s’=(s'1+s'3)/2]. Average results from
triaxial shear tests are presented in Table 3.
Basic deformation and strength characteristics
Blue Oxidative Tailings
pond
dam
lagoon
Characteristics
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Initial void ratio
Preconsolidation pressure
Compression index
Swell index
Oedometric secant modulus
Oedometric elastic modulus
Coef. of vertical consolidation
Coef. of radial consolidation
Creep index
Initial time of creeping
Undrained shear strength
Effective cohesion
Effective angle of int.friction
e
s ’p
Cc
Cs
Eoed
E
Cv
Cri
Ce
t0
cu
c

kPa
kPa
kPa
10-6m2/s
10-6m2/s
min
kPa
kPa
degree
10.27
7.45
10
8
1.501 0.553
0.157 0.285
415
560
1250
4630
0.165
6.05
3.036
4.4
0.0205 0.0128
1450
420
32
12
25
0.825
20.0
0.0733
0.005
14000
45450
0.96
0.076
0.0016
205
15
21
Part 2.
Stress-strain-time behavior
evaluation
The effect of the pore water
pressure on the stress-strain
behavior
Basic constitutive equations for the pore
water pressure evaluation


Following Germanov (2000), the massifs of saturated waste
materials could be considered as multi-phase medium and their
stress-strain behavior being accompanied by two simultaneous,
rheological processes: filtration and creeping.
It is assumed that the deformation of the soil skeleton could be
presented according to the theory of linear creep by the equation:
 (t )
t
1
e0  e(t ) 
mv (t , t ) 
 ( )mv (t , )d

1  2K0
1  K 0 1
where: e0 and e(t) are the initial and variable over time void ratios;
 (t) is the sum of normal effective stresses at a fixed point of the soil
massifs;
K0 is the coefficient of the lateral pressure at rest;
mv(t, ) is the generalized coefficient of volume strain.
Basic constitutive equations for the pore
water pressure evaluation
mv (t , )  m0 ( )   ( )1  exp[  (t   )]
m0( ) is the coefficient of instantaneous strain (linear compressibility);
 ( ) is the function of ageing (tixotropic strengthening) of the soil skeleton.
mh
 ( )  ml 

ml is the coefficient of volume creep strain (secondary compression);
 - the parameter of creeping speed;
mh - the coefficient of "ageing" strain of the soil skeleton;
1 - the parameter of the soil skeleton age (the previous stressed
condition).
The methods for determining the coefficients of volume strains and
the creep parameters are developed by the author (see Germanov
2000).
Basic constitutive equations for the
pore water pressure evaluation

Assuming that the fluid filtration is according to Darcy's law,
the function uw(t,x,y) for two-dimensional consolidation, is
determined by the solution of the following differential
equation:
 2u w
uw


2
a1 2  f1 (t )
 Cv [( uw )  uw ]  f 2 (t ) 1 (t )  a2 1 (t )
t
t
t
t
t
where: 1(t) = sy(t) + sz(t);
sy(t) and sz(t) are the total normal stresses which would be accepted:
constant, when the period of operation is considered; variation with
a constant velocity for the construction period; variation under
cyclic loads (machine foundations or earthquake motions).
Basic constitutive equations for the
pore water pressure evaluation

The other coefficients and functions depend on
the soil properties.
 The author has received an exact solution of the
one-dimensional
consolidation,
under
corresponding
initials
and
boundaries
conditions, according to equation (Germanov,
1988). Using the finite element method, the twodimensional consolidation has been solved
(Germanov, 2000).
Liquefaction potential
evaluation of a tailings
dam
Liquefaction potential evaluation of a tailings dam

The increasing of the pore water pressure under static
and dynamic (seismic) excitation loads may lead to
decrease the effective stresses to zero.
 This phenomenon, known as liquefaction, may provoke
a loss of the bearing capacity and failure of the soil
massifs.
 Evaluation of the exceed pore water pressure under
static loading is performed by using the solutions
developed by the author (Germanov, 2000), based on the
theory of the two-dimensional consolidation, taking into
account the rheological properties of the materials.
Liquefaction potential evaluation of a tailings dam






Liquefaction is a phenomenon in which the strength and stiffness
of a soil is reduced by earthquake shaking or other rapid loading.
The phenomenon is only generally considered for sandy soils and
usually for loose sands.
However, the increase of the pore pressure could reduce the
effective pressure, not only in fine-grained soils and coarsegrained soils.
It was established that clay or silt with low plasticity index, such
as tailings material, has been found to be as vulnerable to
liquefaction (Ishihara, 1985).
One of the criteria for liquefaction potential evaluation is the
grain size distribution.
The results of the laboratory investigation of the tailings materials
from “Liuliakowitsa” tailings dam shows that the investigated
tailings could be classified as fine silty sand.
100
80
60
40
20
0
1.000
0.100
0.010
Diameter ( mm)
0.001
Percent finer by weight (%)
The representative grain-size distribution curves are shown below. It
can be seen that the grain size curves belong to the boundaries of the
most liquefable soils (Ishihara, 1985). This means that in some
conditions, tailings could reach to a state of liquefaction.
Liquefaction potential evaluation of a tailings dam



An approximate method based on theoretical evaluation of
the increase of pore water pressure in tailings dam’s body
during an earthquake is applied herein.
Following Martin & Seed (1978), the basic assumption for
pore pressure generation and dissipation analysis is that the
excess pore water pressure, uw, in a soil element, could be
presented as the sum of the pore water pressure under static
loading, uw,st, and pore water pressure increment generated
under dynamic excitation - uw,d.
The static pore water pressure uw,st could be computed by
using a computer program, developed by the author
(Germanov, 2000) based on the constitutive equations given
in the paper.

The computations are performed, applying nonlinear
experimental relations of the physical and consolidation
characteristics and expressing their variation with the dam height.

A cross section of the tailings dam and in situ measured pore
water pressure are presented below (Kalchev, 2003).
The computations for static conditions show that there are no
differences between theoretical and in-situ measured values of the
pore water pressure.

Nonlinear linear characteristics of
tailings dam for static analysis
Depth, m
19.0
0
10
20
30
40
50
60
70
80
90
100
19.5
20.0
20.5
Compression modulus E oed , kPa
3
21.0
0
21.5
0
10
20
Depth, m
Unit weight g n, kN/m
30
40
50
60
70
10000 20000 30000 40000
Liquefaction potential evaluation of a tailings dam

The dynamic pore water pressure (uw,d) is computed,
considering the tailings dam, under cycling loading, in
undrained conditions, by using the expression (Martin &
Seed 1978):
u w, d
N
 s . arcsin 

 Nl
'
0
2



1
2
where: s'0 is the effective overburden pressure; N – the
number of uniform stress cycles undergone by the soil
element; Nl – the number of cycles at the same levels
required to reach initial liquefaction.
Liquefaction potential evaluation of a tailings dam
The number of cycles are accepted: N = 12 for an earthquake with
magnitude equal to 7; Nl =50, according to Germanov & Kostov
(1994). The distribution of the pore water pressure at the dam height
is presented below.
The maximum value of pore pressure ratio uw/s'0 reaches to 0.8. It is
obviously, under the stress strain conditions, that there is no area in
tailings dam, which would be susceptible to liquefaction.
140
120
120
100
100
uw,st
80
Height, m
Height, m
140
60
40
80
60
40
20
20
uw,d
0
0
200
400
600
Pore pressure, kPa
800
1000
0
0.00
0.20
0.40
0.60
0.80
Pore pressure ratio uw/s 'v
1.00
Evaluation of the ultimate stressstrain state of the slime pond before
encapsulation
Situation of the “Blue Lagoon” before
Encapsulation
Evaluation of the ultimate stress strain state of the
slime pond during encapsulation




One of the variants of the project for encapsulation of the slime
pond “Blue Lagoon” considers establishment of drainage wells
and filling the pond with granular materials as well as
construction of embankment 8 m high.
Another variant without vertical drainage is considered as well. It
is supposed that after dewatering the filling will be made
approximate by constant speed.
For evaluation of ultimate stress-strain state the Mohr-Coulomb
equation for ultimate equilibrium could be used (Germanov, 1986,
2000).
Considering the slime pond in unconsolidated conditions under
embankment’s loads, the dimensions of the so-called "plastic
zones" could be evaluated by using the expression:
Evaluation of the ultimate stress strain state
of the slime pond during encapsulation
 cr  arcsin
s
'
z
s

' 2
y
 4 zy2
s z'  s y'  2c ' cot g '
where, sz, sy and zy, are effective normal and tangential stresses in
a given point of the slime pond.
The zones of ultimate equilibrium are defined by the
condition cr >' ('- effective angle of internal friction). If these
zones are relatively large, the subgrade (slime pond) will lost its
overall stability.
A computer program for ultimate stress-strain behavior evaluation
of saturated soil massifs, taking into account of the pore water
pressure generation and dissipation during construction and
operation has been developed by the author (Germanov, 1986).
Evaluation of the ultimate stress strain state of the
slime pond during encapsulation

Some results from computations are given in Table 4. Two loading
steps are considered: q=80 kPa and q=160kPa, corresponding to
4.0 m and 8.0 m embankment fill respectively. All computations
are performed by using input data (geotechnical characteristics),
according to Germanov (2003).
Table 4. cr values for different depts.
1.
2.
3.
4.
5.
6.
Z
cr (degree)
cr (degree)
(m) for q = 80 kPa for q = 160 kPa
2
15
25
4
12
21
6
10
18
8
9
15
10
8
14
12
7
12
For this case ('  180), the
plastic zone could be formed
to 6.0m depth at the final
stage of loading.
Determination of the timedepending settlement of the
Oxidative pond
Determination of the time-depending settlement of
the Oxidative pond






The first stage of the project for encapsulation and remediation
of the oxidative pond near the town of Burgas, proposes a
filling the pond by granular material over geotextile.
The results of the consolidation tests (Germanov, 2003) show
some specific features of the petroleum refuses which
considerably distinguish them from natural soils.
First of all, the test results show a very low value of densities
and very large porosity (rn 1.0 g/cm3; e = 8.0 10.0).
Water content reaches 500 – 600%.
On the other hand, during the consolidation tests, the
settlements are developing very slowly over time under small
loading.
The great part of the secondary consolidation presumes the
presence of rheological processes.
Determination of the time-depending
settlement of the Oxidative pond
In order то receive a preliminary prognosis of timedepending settlement, a computation was
performed for the subgrade (i.e. petroleum refuses)
under loading from embankment 2.0m high.
 It is accepted that the construction works (time of
filling) will last six months.
 The degree of consolidation at the end of
construction period and during “operation” after
one, two and five years is computed.

Situation of the oxidative pond, slime
field and swamp
Time-depending settlement of the Oxidative pond
Table 5. Final settlement and degree of consolidation
Cross sections
Maximum length, m
Maximum depth, m
Final settlement, cm
Degree of
consolidation, %
At the end of filling
At the end of the
first year
At the end of the
second year
At the end of the
fifth year
II-II
III - III IV - IV V - V Longi-
202
2,10
27.3
220
1.80
25.1
160
1.80
25.6
195
4.20
76.5
341
3.95
63.9
tudinal
550
4.95
79.8
16
24
19
26
16
24
14
22
14
24
14
22
37
39
37
35
35
35
63
64
63
62
63
61
I-I
Determination of the time-depending settlement of
the oxidative pond

The results presented in Table 5 show a low value of
the degree of consolidation at the end of filling.
 With respect to the homogeneous composition of the
petroleum refuses, the computations showed an
approximately equal degree of consolidation at the
end of the different periods.
 An increase of the degree of consolidation could be
reached by increasing the construction period (time
of filling).
 On the other hand, under this loading, in spite of the
low values of the deformation modulus, the final
settlements are comparatively small – from 25cm to
78 cm.
Determination of the time-depending
settlement of the oxidative pond
 Increasing
the final settlements could be
possible by means of additional loads, which,
after reaching the predicted settlement, should
be removed.
 The great value of water content supposed
compression under static loading only.
 The influence of the dynamic loading (for
example vibrations) on such type of refuse
materials needs an additional study.
Conclusion

The results presented in the presentation
underline the considerable influence of the pore
water pressure on the stress-strain behavior of
waste deposits which reached a limit state.
 Besides the conventional methods for stability
analysis of the saturated waste deposits,
additional analyse, such as liquefaction, bearing
capacity and time depending settlements should
be made.
References






Germanov, T.(1988). Creep and ageing effects on stresses and
deformations of saturated clayey soils”. Proc. Int. conf. on rheology
and soil mechanics, Coventry, pp 194-203.
Kaltchev (1998). Instrumentation system for Assarel Tailings dam.
Proc. Green 2. Krakow, pp. 270-272.
Abadjiev, Germanov, Markov. (1987).Determination of tailings
consolidation for a high spigotted tailings dam. Proc. 9th ECSMGE,
Dublin, vol.4.1, pp.355-357.
Germanov,T. (1986). Special problems in analyzing embankments).
Proc.8-th Danube-European Conference on SMFE, Bericht zu Sitzung
E, Nurnberg, vol.II, pp 65-67.
Germanov, T.(1988). Creep and ageing effects on stresses and
deformations of saturated clayey soils”. Proc. Int. conf. on rheology
and soil mechanics, Coventry, pp 194-203.
Germanov, T. & V.Kostov (1994). Determination of Tailings Properties
for Seismic Response Analysis of a Tailings Dam. Proc., 1st
International Conference on Environmental Geotechnics, Edmonton,
pp. 499- 504.
References






Germanov, T. (2000). Effect of the Pore Water Pressure on the StressStrain behavior of Earth Dams. Proc. of the GEOTECH - Year 2000
Development in Geotechnical Engineering, AIT, Bangkok, pp.429-438.
Isihara, K. (1985). Stability of natural deposits during earthquakes;
Proc. 11th International Conf. On SMFE, San Francisco, Vol 2, pp.321376.
Jessberger, H.L. & R. Kockel (1995). Determination and assessment of
the mechanical properties of waste. Proc. Symposium Green
93,.Balkema, pp.313 – 322.
Kaltchev I.(2003). Investigation and testing of pore pressure, phreatic
surface location and hydrodynamic
pressure in “Asarel –
Medet” tailings dam. Proc. 13th ECSMGE, Prague.
Martin P., H.B.Seed (1978. Apollo, a computer program for the analysis
of pressure generation and dissipation on horizontal sand layers during
cyclic or earthquake loading.. UCB/EEC-78/21
Vanicek, I. (1998). Talings dams for flying ash – some experiences
gained in CR. Proc. 3th International Conference on environmental
geotechnics, Lisbon.
Situation of the projects
Blue Lagoon
Oxidative
pond
“Liuliakovitsa”
tailings dam
View of the slime pond “Blue Lagoon”
before encapsulation
Overview of all oxidative ponds near Burgas
Sampling of Tailings Materials

A borehole net consisting of 40 drillings, was elaborated
for sampling from tailings dam. By using a standard
drive sampling method, more than 50 undisturbed
samples were taken at different depths through 5 m. A
representative sample is shown below.
Oedometric tests apparatus
Oedometric tests - “Blue Lagoon”
Oedometric tests - “Oxidative pond”