TABLE OF CONTENTS
A.Text part:1. Introduction.
2. Hydrogeological Research.
2.1. Experimental Water-Drawing in Hydrogeological Research Lots.
2.2. Experimental Water-Infusion.
3. Geotechnical Research.
4. Conclusion.5. Hydrological Research
B. Graphic Supplements:
|
1. Situation of the Belene Island Wetland Area. |
1 copy |
|
2. Graphics of Experimental Water-Drawing. |
3copies |
|
3. Graphics of Experimental Water-Infusion. |
4 p. |
|
4.Engineering-Geological Block-Diagram M 1:10000/2000 |
1 copy |
|
5. Graphics of Dynamic Penetrations of a Light Type |
18 p. |
|
6. Graphics of Geophysical Experiments with the WES Method |
4 p. |
|
7. Geotechnical Columns of Exploratory Borings |
15 p. |
1. Introduction
During the period May - July 2003 there was conducted a hydrogeological and geotechnological piece of research of the sites “Belene Island Wetland Area” including the implementation of geological-research-works pursuant to the requirements of the technical task. For the two sites together, there were implemented: 3 hydrogeological exploratory lots/each with a central and observation boring with a depth of 25 m./, 4 tests for water-infusion /each test was implemented with the usage of two different methods/, 15 exploratory borings, 18 dynamic penetrations of a light type and 4 geophysical research with the WES method. From the site, there were taken and given for analysis 5 inviolate earth samples, the results of which will be delivered later on. The location of all geological work out was defined with the help of a GPS apparatus and drawn on the large-scale maps elaborated for this purpose.
For the preparation of the present report, the selfless work of the drill teams and engineering-technical personnel were of decisive significance.
2. Hydrogeological research.
The island of Belene is the largest Bulgarian island along the river Danube. It is formed of alluvial sedimentations as is the whole Belensko-Svishtovska lowland.
Form a hydrogeological viewpoint, there are two units on the island:
a) Cretaceous water-support (Alb marls);
b) Quaternary cover (alluvial types of gravel, sand and sandy clay).
Practically, two basic hydrogeological units correspond to them, and namely:
¨ Alluvial water-carrying horizon in the contemporary terrace of the river Danube.
¨ Watertight marl pad.
The alluvial terrace consists of two main layers:
¨ upper layer - yellow-brown sandy and dusty clays, with a lift of 4 and 12 m.;
¨ lower layer - gravel with sand, with a lift of 7 and 15 m.
2.1. Experimental Water-Drawing in Hydrogeological Research Lots.
In order to insure reliable hydrogeological information about the parameters of the alluvial water-carrying horizon, three exploration lots were constructed which were located along the axis north-south through the island’s whole latitude /see the enclosed survey map/. Each lot includes one water-drawing and one observation boring with a core siege without washing out. The boring is with a depth of 25 m., it serves as an observational one, but with the help of its information the dimensions have been determined of filters and deaf pipes of the water-drawing boring’s pipe-filter column. The observation one has been fulfilled with a diameter of 182 mm. and a perforated PVC column has been lowered with a diameter of 90mm, into it which has been preliminarily wrapped up in a nylon net with an opening of 1 mm. The space behind the pipe has been filled with felt.
Depending on the particular field conditions, at 6 or at 3 m. from the observation boring a water-drawing boring has been implemented with a diameter of the chisel 250 mm. The boring has been performed with clay washing out, a non-core /three-roller chisel/ to the depth of 25 m. In the boring opening a pipe-filter column has been lowered which consists of deaf and perforated pipes /filters/ in compliance with the geological information of the observation boring. After the lowering of the pipe-filter column, the space behind the pipe has been filled with felt, fraction 5-15 as together with it through an airlifting pipe outfit, on pushes, a clearing and stimulation of the water-carrying horizon has been realized.
After the restoration of the static water level in the water-drawing boring, an exploratory water-drawing with duration of 48 hours has been conducted. After the ceasing of water-drawing the restoration of the entry level in the central and observational boring has been followed up.
The results of the conducted field research works have been systematized and used for calculation of filtration parameters of the water-carrying horizon. The obtain in a calculation way values of the hydrogeological indices and the defined border conditions have been used for choosing of a conceptual model and conduction of hydrogeological modeling.
The hydrogeological parameters of the water-carrying horizon have been defined by means of the data from the lowering measured in the central and observational boring during the water-drawing. The defining of the conductivity T (m2 /dn) can be made according to Jacob’s method on the basis of Theis formula and more precisely of its logarithmic type responding to a quasistabilized regimen, and namely:
S = 0,183.Q lg 2,25.a.t /1/
T r2
where:S - lowering at the end of water-drawing, m;
Q - capacity of boring, m3 / d;
a - a coefficient of piezotrasmission, m2 /d;
t - time from the beginning of water-drawing, min.;
r - effective radius of drawing boring, m.;
T - conductivity of water-carrying Quaternary sedimentations, m2 /d;
This solving is valid when the following condition is observed: r2 < 0.1
4.a.t.b
i.e. some time after the beginning of water-drawing when the quasistabilized filtration takes place. The equation /1/ is an equation on a straight line in co-ordinates with an ordinate S and an abscissa lg (t). The slant i of the straight line is
lg j = i = 0.l83.Q
Tfrom where we could define
T = 0.l83.Q /2/
i
where:Q - capacity of boring, m3 / d;
i - slant of the straight line;
T - conductivity of water-carrying sedimentations, m2 /d;
On the basis of the results from the exploratory water-drawing, graphics have been drawn up representing co-ordinates with an ordinate S and an abscissa lg (t). From the straight line lot which is formed some time after the beginning of water-drawing and corresponds to the quasistabilized regiment the slant i is defined. Through it and with the help of Formula 2 the layer’s conductivity is defined.
The hydrogeological parameters of the water-carrying horizon are defined also according to the data about restoration of the underground waters’ level after the ceasing of water-drawing. On the basis of the results from the restoration of underground waters’ level graphics have been drawn up representing co-ordinates with an ordinate S and an abscissa lg (t). From the straight line lot which is formed at the beginning of the co-ordinates the slant i is defined. Through it and with the help of Formula 4 the layer’s conductivity is defined.
This decision is also valid when the following condition is observed:
r2 < 0.1
4.a.t.b
i.e. some time after the beginning of restoration when a quasistabilized filtration takes place. The equation /3/ is an equation of a straight line in co-ordinates with an ordinate S and an abscissa lg(t0 + tB)/ tB. The slant of the straight line is:
lg j = i = 0.l83.Q
Tfrom where we can define:
T = 0.l83.Q /4/
i
where:Q - capacity of boring;
i - slant of the straight line, 0,32 m.;
T - conductivity of water-carrying sedimentations, m2 /d.
During the period of water-drawing, due to hydrodynamic imperfection, there have been created additional resistances which can lead to big errors in the defining of the hydrogeological parameters: conductivity of the water-carrying layer ( T ), coefficients of piezotransmission ( a ) and water- giving ( m ). This is why, for the defining of the above mentioned coefficients it is necessary to use the results of the lowering and restoration of water level in the observational boring obtained during the filtration test.
After the processing of the data from the experimental water-drawings and restoration of the water level according to the so far described methods, we obtain the following values:
|
i |
T |
a |
m | |
|
SK - 1c. - water-drawing |
0,050 |
790,6 |
4466 |
0,177 |
|
SK - 1c. - restoration |
0,052 |
760,1 |
3990 |
0,190 |
|
SK - 1n. - water-drawing |
0,040 |
988,2 |
5009 |
0,197 |
|
SK - 1n. - restoration |
0,050 |
790,6 |
3979 |
0,198 |
|
SK - 2c. - water-drawing |
0,100 |
632,5 |
4463 |
0,140 |
|
SK - 2c. - restoration |
0,117 |
540,5 |
3277 |
0,165 |
|
SK - 2n. - water-drawing |
0,130 |
486,5 |
3217 |
0,151 |
|
SK - 2n. - restoration |
0,150 |
421,6 |
3421 |
0,210 |
|
SK - 3c. - water-drawing |
0,080 |
921,0 |
5007 |
0,180 |
|
SK - 3c. - restoration |
0,075 |
982,4 |
7033 |
0,139 |
|
SK - 3n. - water-drawing |
0,090 |
818,7 |
5114 |
0,160 |
|
SK - 3n. - restoration |
0,086 |
921,0 |
4177 |
0,200 |
Mean of the conductivity T = 750 m2 /d
Mean for the filtration coefficient Cf = 66,5 m/d
2.2. Experimental Water-Infusion.
Filtration tests for defining of the coefficient of filtration of the dust-sandy clays over the water-carrying horizon (the aeration zone).
Scope of experimental-filtration research.
The coefficient of filtration of the clays constituting the aeration over the water-carrying horizon of the alluvial types of gravel is defined at two levels:
· Level 1 - including a layer with a depth of 0.4 - 0.5 m. under the terrain. i.e. the layer lying just under the bottom of the future lake;
· Level 2 - including the deeper part of the aeration zone (between 0.5 and 2 meters under the terrain) during which mainly the infiltrated from the lake water will flow to the water-carrying horizon.
We shall notice that it was not possible (neither necessary) to conduct deeper tests in the aeration zone as the level of underground waters during the research period was quite high - at some places it was by 2.5 - 3 m. under the terrain.
Methods of taking and interpretation of the filtration tests.
The relatively low water-permeability of the clay sediments predetermined as most suitable the express water-infusions.
a. Shallow tests (Level 1).
At first express water-infusions in “SHURFI” (rings) were planned. However, the tests were conducted according to a scheme which differs from the water-infusions in the standard rings. In the dug shallow “SHURFI” a pipe with a small diameter (85 mm.) was stuck in which the fast water-infusion was conducted and the resulting lowering of the level was followed up. Actually, this test corresponds to the scheme “water-infusion through boring working with his bottom only”. For this reason, jointly with the consultant, in order to define the coefficient of filtration respective methods which are adequate to these tests were applied.
The defining of the coefficient of filtration according to the data from similar tests is treated in the works of Kirkham [1946], Joungs [1968], Mironenko & Shestakov [1978] and other. Over the abscissa axis the values of time (t) are drawn up from the beginning of the test (the instant infusion) and over the ordinate axis in a logarithmic scale - the remaining water column (H) at the respective moment - Fig...1. The slant of the obtained representative straight line (I) is defined after which the coefficient of filtration is calculated with the help of the formula:
k = 1040 r I,
where r is the boring’s radius in m.; i is the slant of the straight line in min-1 . The coefficient of filtration is in m/d.
|
 
      
|
|||||||||||||||||||||||||||
|
Figure 1 |
|||||||||||||||||||||||||||
b. “Deep” tests (Level 2).
In this kind of tests the boring “operates” with all it’s open trunk. The data processing is conducted according to a procedure famous in the literature as “Method of Ernst” (here it is presented with an insignificant modification). The data about the lowering of the level are drawn up in the co-ordinates
lg(s+0.5r) = f(t). I.e. along the abscissa, the time t is drawn up and along the ordinate the respective values of the expression (s + 0.5r ) - Fig.2. The result is a straight line with a slant i. Having defined the slant of the representative straight line, the coefficient of filtration k can be calculated according to the formula
k = 16.5 r i
where the boring’s radius r is in cm, and the slant of the straight line - in min-1 . Yet, the coefficient of filtration is in m/d.
We have to notice that the initial moments deviate from the representative straight line in an ordinary way as the latter corresponds to the approximate solution of the problem which becomes valid some time after the beginning.
|
|
|
|||||||||||||||||||||||
| Figure 2 |
||||||||||||||||||||||||
Results from the calculations.
The results from the conducted tests and defined coefficients of filtration are given in Appendix I.3 and in Table 1.
Express water-infusions in borings - values of the coefficient of filtration
Table 1
|
Lot |
Kmid | ||||
|
Level 1 |
1 |
2 |
3 |
4 |
|
|
0.085 |
0.188 |
0.053 |
0.018 |
0.086 m/d | |
|
Lot |
Kmid | ||||
|
Level 2 |
1 |
2 |
3 |
4 |
|
|
0.395 |
0.456 |
0.309 |
0.432 |
0.398 m/d | |
From the results described it is seen that the thin layer (about 50 cm) under the terrain which in many aspects is identified with the soil layer has a lower water-permeability. The mean coefficient of filtration for it can be accepted to be:
k » 0.9 m/d.
Under it, the aeration zone differs with significant filtration homogeneity and a higher coefficient of filtration for which we can accept a mean computing value of:
k » 0.4 m/d.
3. Geotechnical research.
In correspondence to the technical task, on the island geotechnical research were conducted about:
1. The road-bed of the new draining canal parallel to the border dike “north-south” with an approximate length of 5 538 m and a width of 100 m.
For the implementation of the task 11 exploratory borings were conducted with a depth depending on the height of the dikes and 12 dynamic penetrations of a light type according to the Bulgarian State Standard of the terrain with a depth to 4 meters. With the volume of work measured in this way a density of the makes is achieved - one per every 250 m of the road-bed.
2. Point F of the north side (569.3 r.km of Danube) and Point A from the south side of the Danube’s arm (570.5 r.km of the Danube) and the exit points - Point E (r.km of the Danube) and Point D (561.5 r.km of the Danube) in the east part, inclusive the entrance-exit canals. The entrance canal in Point A (r.km 570.5) has an approximate length of 270 m and in Point F (r.km 569.3) 520 m and also the drainage canals.
For the implementation of the task, 4 borings altogether were implemented from the dike with a depth depending on the dike, 8 dynamic penetrations of a light type according to the Bulgarian State Standard /depth to 4m/ and 4 research with the help of the WES method.
From the research conducted it was found that the earth base consists of:
Layer 1. - An embankment of clay, dust-sandy and sandy. From this material the safety dikes of the island are constructed. The thickness of dikes varies from 2-3 to 7-8 m. For their construction the nearest possible embankment materials have been used which have been thoroughly congested by hand at the time of their putting into the embankment. The dikes have no ant filtration core.
- volume density - 1,75-1,8 g/cm3
- category of ditch - earth
Quaternary-alluvium Qal
Layer 2. Sand, grey, with various grains, at places with fine and medium-sized gravels. This layer is in alternation with the others of the alluvial complex but usually occurs over the gravel layer 5 and their border is quite conditional. The layer’s thickness reaches up to 5 meters at certain places. For this layer we accept:
- volume density - 1,65-1,75 g/cm3
- category of ditch - earth
Layer 3. - Clay, brown, with grey strips, dust-sandy, with thin seams of dust and clay sand. This layer is the basic covering water impermeable layer of the territory under research. Its power is about 7-8 m. The upper 40-50 cm of the layer are covered with soil. In the location of this layer 18 dynamic penetrations, with a depth of 4 m, have been realized as in it the main capacity of earth work will be done. In compliance with it for this layer there are defined:
- volume density - 1,8 g/cm3
- coefficient of pores - 0,8-1,1
- compression module for a vertical load 0,2-0,3 MPa M=up to 6,5 MPa.
- module of general deformation Eo=0 to 23 MPa /see Appendix I.4./
- calculation angle of internal friction -10°
- calculation cohesion - 0.05 MPa
- calculation loading Ro - depending on the results from the penetrations for each separate case /see Appendix I.4./
- category of ditch - earth
Layer 4. - Clay, dust, motley, medium- to mildly plastic. It occurs as seams with thickness up to 0,5-1 m in the location of sandy and gravel sediments. It is not of specific importance for the future building. For this layer there are defined:
- volume density - 1,9 cm3
- category of ditch - earth
Layer 5. – Gravel with various grains, with sandy filling lays at the lower parts alluvial complex. This layer is the basic covering water impermeable layer of the territory under research. Its power is about 10-12 m. For this layer there are defined:
- volume density - 1,95-2.0g/cm3
- category of ditch - earth
4. Conclusion
The geotechnical and hydrogeological research of both water areas were conducted in a way and in a capacity enough for the insurance of reliable geological information for projecting.
In a hydrogeological and geotechnical respect, the conditions for building on both platforms are complicated due to the presence of soils relatively unable to bear loads, swampings, high subsoil waters, big fluctuations in the level of the Danube etc. For this reason, especially precious proved to be the information acquired with field and easily portable apparatuses - penetrometer, UPI installation for geophysical studies as well as the usage of express and relatively simple for implementation methods for water-infusion.
The preparation of the entire research was in compliance with the technical task of the Assignor.
5. Hydrological research 2.2
The period of research at the ІVth – VІth months, was at the same time as the critical mode, known as “low waters” with permanent tendency of reducing.
That interlocked the opportunity for the execution of the assignment of task №2.2, including:
Accomplish measuring the level of the Danube river and branches at the site from rkm 554.0 tо rkm 581.2 /Belene Island Wetland Area/ - two times during the high water period.
At the period of expansion and accomplishment of the field works, it wasn’t determined “high water” and there weren’t accomplished such measurements. There are available archives of measurements from year 2001 at zone standing at 10m. from the Island, down steam the river, at different points from the river water track, made at the time of the geological measurement then, which are systemized by time and place and are disposed for use and juxtaposing with the available at the APPD-Russe statistics for the period.
WATER LEVEL AT BELENE ISLAD
Coordinate System 1970
Zone К-7|
No |
X |
Y |
Water Level |
Time and Date of measurement |
|
1 |
4732623.57 |
9421130.03 |
17.63 |
11:53 20.06.2001 |
|
2 |
4733110.02 |
9421962.77 |
17.62 |
11:57 20.06.2001 |
|
3 |
4733307.13 |
9422952.57 |
17.61 |
12:02 20.06.2001 |
|
4 |
4733629.48 |
9423916.51 |
17.60 |
12:06 20.06.2001 |
|
5 |
4733828.52 |
9424877.78 |
17.60 |
12:10 20.06.2001 |
|
6 |
4733986.03 |
9425852.10 |
17.59 |
12:14 20.06.2001 |
|
7 |
4734162.35 |
9426827.06 |
17.60 |
12:18 20.06.2001 |
|
8 |
4734183.20 |
9427812.92 |
17.59 |
12:22 20.06.2001 |