Download Geological engineering problems with respect to location lines

Geological engineering problems with respect to
location lines especially train routes in the Lausitzer thrust end moraines
Cornelia Lindner, TU- Bergakademie Freiberg
Abstract. With increasing mobilization it is necessary to expand more and more
the infrastructure. Therefore, among other things an exactly planning and organisation of the redevelopment of existing rail routes is essentially. The stabilization
of the older railway especially traffic embankments of track is also needed and has
to be, if necessary, characterized regarding new geological engineering aspects.
For this it is required to factor both geological and geotechnical problems. This
paper’s aim is to give an overview about the several problems in the respective
fields.
Introduction
To describe the topic the Niederlausitz and the northern part of the Oberlausitz is
considered to be the relevant region.
The area of the Niederlausitz can described as the following: it lies across the
borders of Saxony and Brandenburg and takes an area of about 2323 km2. The
backswamp area of the Elster and the Muskauer Heide borders in the south. The
Fläming adjacent to the west, the valley of the Neiße in the east, the Spreewald
and the Baruther ancient river valley in the North [BfN:Landschaftssteckbrief].
The Lausitzer Grenzwall passes through the Lausitz from the Southeast to the
Northwest. The region of the Niederlausitz can subdivided in other landscapes.
The Niederlausitzer Randhügel consisting of hills of basal and end moraines with
a relief variation from 90 and 167 m above NN and lies in the west [BfN: Landschaftssteckbrief]. The Kirchhainer – Finsterwalder basin is arranged between the
Randhügel and Lausitzer Grenzwall and consists of an even basin with
backswamp areas [BfN: Landschaftssteckbrief]. In the north of the Lausitzer
Grenzwall is the Luckau – Calauer basin and has a height of 80 metres [BfN:
Landschaftssteckbrief]. This is an even basal morainic cateau containing two basins; one around Calau and one around Luckau. Thereupon it borders one more
basal morainic cateau in the Southeast; the Cottbuser Sandplatte. Within there are
moistly back swamp areas and dunes. Sandy soils are predestined for pinewood
and mixed forest. Partly there are found also areas of heath for example the Sächsische Heide [BfN: Landschaftssteckbrief]. The Black Elster and Spree present
the main rivers in this region.
2
Conny Lindner
Through the different ice advance in the Elster – Ice – Age and the Saale – Ice
– Age developed several end moraines (thrust moraines) and basal moraines. The
Weichsel – Ice – Age is only represented with larger aeolian deposits and valley
sands. The complexity of the thrust end moraines is its structure
Fig.1 systematically
sketch of a thrust end
moraine as an example of folding and
overthrust.
(modified after Ehlers
1998)
Fig.2 systematically
sketch of a thrust end
moraine with regional
thrust blocks
(modified after Ehlers
1998)
itself (look at Fig. 1 and Fig.2). Ehlers [1994] describes them as dislocations
which developed through the pressure of the glacier ice. At this the structure can
be distinguished between a) overturned folds and growth faults b) appearance of
forms of diapirism, shearing older structures c) sag structures because of the melting of the glacier [Ehlers 1994].
The detachment occurred mostly by clays. At this it plays a prominent role if
the subsoil was frozen or not.
Ingenieurgeologische Problemstellung an Trassen im Verkehrswegebau im Bereich von
Lausitzer Stauchendmoränen (Beispiel Bahntrassen) 3
On the border of the moraines fluvioglacial deposits are situated. The area is
interstratified of lignite seams and they are mined in the open pit. However this
lead to artificial caused ground – water lowering.
The thrust end moraines means a problem for the location lines because of the
inhomogenity of the formation ground. For this reason it is important to know the
characteristic of the soils for the redevelopment. To make location lines safety (on
demands of loads and velocity) after RIL 836 it is necessary to resolve the following problems:
- geotechnical problems in the railway construction (embankment, cutting,
sameness of terrain)
- engineering geological problems of the foundation ground and subsoil
- static and dynamic loading on the road bed, formation ground and the
surrounding
- technical problems of mining
To approach the single problems it is necessary to plan and record the geometry of the embankment, position of the embankment, soil characteristics, stability
of the embankment, vegetation and condition of the surface of the embankment,
erosional areas, slope caving and geological/ hydrological circumstances [Döring
– Koppatz,2006]. As well as an inquiry and interpretation of the documents is essential. In this connection for the several loads DIN 1054 and DIN 4020 are used
as standard. Likewise the acquisition of the excavation permit and permission for
the entering is very important. In the terrain the photographic and visual information assessment is essential. This is authoritative after DIN 19712 [Döring – Koppatz, 2006]. In addition geotechnical examinations, soil – mechanical laboratory
experiments for assignment of the formation ground as well as soil – mechanical
characteristics will follow.
Geological conditions
The geology of the southern Niederlausitz and the northern part of the Oberlausitz
predominantly consists of Pleistocene deposits with Elster – Ice – Age till the
Weichsel – Ice – Age and Holocene deposits. Proterozoic to Palaeozoic rocks like
the Lausitzer Granodiorite are situated to the south of the Niederlausitz. The landscape is mainly affected by the Elster – Ice – Age advance and Saale – Ice – Age
advance. That is the reason why there are basal- and end moraines. With a closer
look the end moraines can be differentiated according to the geological map in
thrust moraines, a combination of thrust moraines and dump moraines respectively. Now the area to the south of the Lausitzer Grenzwall and the Muskauer
Faltenbogen is considered for an explicit and exemplary description. At this it is
the matter of the Petershainer end moraine, Zeißholz – Liebgaster end moraine
and Hirschfeld – Ortrand end moraine with Elster – Ice – Age. These arose during
the second ice advance. Excepting the Zeißholzer end moraine the other both end
moraines are a combination of dumped and thrust moraines. The Zeißholzer end
moraine is more likely to show a character of a thrust moraine.
4
Conny Lindner
The geological overview map of Saxony 1:400000 [Säsisches Landesamt für
Umwelt und Geologie, 1992] shows regions of Elster – Ice – Age end moraines
with intercalated valley sands of Weichsel – Ice Age. Eastward of the Zeißholzer
end moraine melting water deposits from the Elster – Ice – Age and the Saale –
Ice – Age are situated. Furthermore several open pits to one another as well as
fractional Neogenic interstratification from the Lower Miocene – Middle Miocene are visible. Here it involves the Lausitzer coalbed (Miocene age). In the east
of the sheet exists several dunes and flying sand from the Weichsel – Ice – Age
exist. The rivers are surrounded by floodplains.
For the question of the geological engineering problems and characteristics the
railroad from Knappenrode till Horka through the Petershainer end moraine is
considered.
In the east there are visibly large scale sands and gravels. These correspond
above all to the valley sand sequence; only on the western side of the sheet signatures corresponds to the lower terrace of the Neiße. The valley sands developed
during the Weichsel – Ice – Age.
In the neighbourhood of open pit Bärwalde Weichsel - Ice – Age flying sands
and dune sands exist. An example for this is the Sächsische Heide. The regions
of the dunes are characterized by a loose packing and belong to the closely staged
soils.
Holocene sands and gravels which are partly silty show only a middle possibility of infiltration because of the silty parts the permeability is going down.
They can be found over all in the surrounding of seas and rivers.
The meadow loam is among the several Holocene deposits. This has because
of its condition, a higher compressibility because of a great pore volume and consequently a bad compressibility as well as a lower shearing resistance [Institut für
Geotechnik TU – Freiberg, 2005].
In addition Elster – Ice – Age consolidated till follows. This is predominantly
aquicluded. Thus their possibility of infiltration is bad. This leads to a ponding and
moisture of the formation ground. After the hydrological map M33 – Cottbus
1:200000 [Zentrales Geologisches Institut, 1970] an imbrication of the end moraines
with Miocene sands, silts, clays and brown coal is possible. The ground water
table lies also according to ground – water reservoir in deeper regions. These are
ground water – bearing but for the ground – water capture bad. Local formation of
ground - water bearing sands are alternating of hardly ground – water bearing
Quaternary sands [Institut für Geotechnik TU – Freiberg, 2005]
The sandy and gravely sequences of the Salle – Ice – Age correspond to glaciofluviatile sands and gravels which represent, in german named,
Nachschüttbildung. They are situated in the sourrounding the area of the consolidated till. [Institut für Geotechnik TU – Freiberg, 2005].
In the further route course smaller areas of bottom peats turfy moulders from
the Holocene respectively, are found. They exist over all in the west of the map. It
is clear that the ground – water table is near the surface itself [Institut für Geotechnik TU – Freiberg, 2005].
The last unit consists of Holocene bog earth, humus and organic sandy parts
[Institut für Geotechnik TU – Freiberg, 2005].
Ingenieurgeologische Problemstellung an Trassen im Verkehrswegebau im Bereich von
Lausitzer Stauchendmoränen (Beispiel Bahntrassen) 5
For the special hydrological meaning the open pit Nochten, Bärwalde, Lohsa
and Reichwalde are relevant. The open pit Bärwalde and Nochten is flooded.
Whereas Reichwalde always still possesses a lowered water level. This forms a
widespreading cone of influence.
Erection of embankment and there problems
For the construction of a railway two variations exist. On the one hand the railway
body possesses a sameness of terrain on the other hand an embankment has to be
created.
In the case of a sameness of terrain the base grad corresponds to the subsurface
level. The base grade forms the direct connection with the foundation ground. After that follows the formation protection layer and the railway ballast. If it should
be necessary to build a substructure the subsurface level has to be divided from the
base grad (Fig.3 and 4 shows this fact).
Fig.3 construction of an embankment, modified after Döring - Koppatz
Fig.4 construction of a railroad with the sameness of terrain
Outwards the embankment is limited through the top layer of embankment and
the shoulders of the embankment. The substructure has to be constructed after RIL
836. After Striegler [1998] the main forces appeared at the top layer of embankment and the slope regions of the embankment which have to consist of water proofed and non - shifting structural material of the embankment. The kind of
building itself is always in horizontal layers of which every layer will compacted.
Because of that the use can be easier with specific compaction engines and a constant verification of the several layers. The connections between compaction,
height of filling and kind of soil is fixed in the ZTVE – StB 94/97 and RIL 836.
The substructure is influenced by heavy precipitation, heat and frost. Additional
6
Conny Lindner
traffic loads (Verkehrslasten) exist which can be transmitted over the track in the
boxing and so in the base grade.
In the present example it should be mentioned that no formation protection
layer exists. At the future planning of the formation protection layer there are three
possibilities of the infiltration and the water outflow:
1) Substructure and formation ground are coarse grained soil. For this the
grain mixture 2 - a coarse grained material – is used. The water is able to
flow off the railway ballast to the subsoil without an influence.
2) Substructure and formation ground are cohesive soil. Therefore it has to
be used the grain mixture 1- a mixed grained material. Thus the water
flows along the slope in the track ditch.
3) Cohesive formation ground and coarse grained substructure. The grain
mixture 1 is also used. Because of the inclined form of the base grade the
water can drain into the track ditch.
However if the protective layer is constructed (RIL 836) wrong or not enough
sealing the water outflow is prevented and leads to moisture of the subsoil. This in
turn expresses in slacks of the tracks and deformation.
Frost damages express through a heavy deformation of the subsurface level because of the thawing of the foundation ground and moisture itself. To present the
damages it is necessary that no water can clam up in the formation ground. It has
to be realizing a dewatering of the foundation ground and embankment [Striegler,
1998].
Before beginning with the construction of the embankment the topsoil has to be
stripped. In the case of cohesive dam material a protection layer should be inserted
thus the water cannot rise to protect the embankment from moisture deposition
[Striegler, 1998]. Settlements across the whole embankment profile guarantees a
menace because the shoulders of the embankment are lower compacted as in the
middle of the embankment because of technical reasons. For this reason higher
settlements occur because of dynamical shocks and damages of erosion [Striegler,
1998]. To solve this problem it is possible to create a track packing respectively a
over breakage [Institut für Geotechnik TU – Freiberg, 2006].
The elastic sinking is located at millimetre range [Schanz, Witt, 2002]. Sinkings of the track and deformations had to keep within the RIL 836. In the case of
cohesive formation ground special construction had to be inserted to a heavy loading of the embankment body as well as solid effect of the environment (noise,
damages of building).
Geotechnical problems of the embankment foundation ground
For the connection between foundation ground and load bearing capacity of the
embankment the map Niesky 1:50000 [Sächsisches Landesamt für Umwelt und
Geologie, 1999] should been consulted. There is to note that the cutting of slope is
a result from the morphological caused differences. The largest part of the railway
consists of sameness of terrain which means that no substructure exists as dumped
embankment. The basal grad is built immediately on the formation ground. Be-
Ingenieurgeologische Problemstellung an Trassen im Verkehrswegebau im Bereich von
Lausitzer Stauchendmoränen (Beispiel Bahntrassen) 7
cause of the “waviness” of the area there are small depressions in which the water
flows in. The soils will get worse with regard to their load bearing capacity. To
understand the foundation ground and subsoil
Fig. 5 shows a generally conclusion.
Fig.5 shows the stratigraphy and facies of
the Quarternary deposits in the Saale –
Elbe – region.
The colours are defined after the geotechnical standard (DIN 4023).
[modified after Ehlers, 1994]
Light brown green = meadow
loam
dark brown green = loess
yellow
= gravel
orange
= sands
grey
= consolidates
till
mauve
= organic silt,
dark violet
= banded clay
white
= not regarded
The foundation ground can be divided in stable and little till non – stable foundation ground. The stable
foundation ground is distinguished by
no required foundation work. Because
of that it is immediately possible to
place the base grade on the formation
ground. In the present example the consolidated till is an excellent formation
ground, as it is very stable and consequently also self – supporting. This is explained through the preconsolidation of the glacier. It gets a higher compaction of
the subsoil and so the following higher shear strength. The lower compressibility
results from this. However the water content of the consolidated till shows a prob-
8
Conny Lindner
lem. This is able to contribute to frost heaving and has to be taken into consideration of the foundation [Institut für Geotechnik TU – Freiberg, 2005]. Because of
the backwater effect of the consolidated till the water outflow have to flow off
track ditch. The track ditch is sealed against the foundation ground and flows into
a larger receiving stream. The backwater effect causes moisture of the slope if the
water cannot flow off.
Sands of thaw water, valley sands and “Nachschüttbildungen” have an excellent stability and thus also belong to a good foundation ground. Because of their
good permeability they have an excellent infiltration. However the following
problems have to be noted; betting of peat, remains of wood and carbonate cementation can mean resistance while drilling and digging of development of the foundation ground. Settlements and swelling is due to bettings of peat.
Lower to non stable foundation ground required technical foundation ground
arrangements which should give an overview in Fig.6 and better foundation
ground measure to sustain the static and dynamic loadings. At this the followed
problems appear; problems of the stability (ground break and slope fracture),
problems of deformation (settlement, perpendicular displacement, sliding), hydrological problems and behaviour of the vibrations. It is being distinguished between
two kinds of soils with lower load bearing capacity; a) soft cohesive, near-surface,
loosened soils with big moisture deposition. They have a low strength which leads
to settlement and sliding. It concerns at this meadow loams and warp clays
[Schanz, Witt, 2002]. B) Soft cohesive, low lying, organic soils with a higher
share of organic matter. For this is among peats (swamps), organic silt, digested
sludge and deposits [Schanz, Witt, 2002].
The embankment often existed when there are depressions. In the depressions
turfy moulder regions can be found which have a lower load bearing capacity.
The traffic embankment was constructed for a better load bearing capacity of the
foundation ground. In the case of the little peat - bogs in the valley sands area the
peats can be exchanged for a better foundation ground. In the area of the consolidated till Miocene clays and coal seams are imbricated together because of the
thrust fault over the valley sand series. This leads to a confined ground - water
which causes problems in the exploration of the foundation ground. A dewatering
of the foundation ground is not possible.
Ingenieurgeologische Problemstellung an Trassen im Verkehrswegebau im Bereich von
Lausitzer Stauchendmoränen (Beispiel Bahntrassen) 9
Fig 6. overview of technical foundation ground arrangements of the embankment
[Striegler, 1998]
A solution for this problem can be a piling foundation to the valley sand series
or older stable horizons. Furthermore solutions are geological synthetic materials.
This problems also applied to meadow loam and warp clay.
Loose lying sediments like dunes and flying sands, Holocene deposits respectively, are characterized as closely staged grain fraction and loose packing without
compaction. These characteristics points to an unconfined aquifer with a good
possibility for infiltration. Because of this a good permeability can be concluded.
Furthermore changes in the ground – water table is adjusting because at the moment the open pit is flooded. From this it follows that one part of the ground – water table raises and one part still decreases. Thus this leads to different uplifts (flotation) or settings in the area of sands. They have no cohesion but a good load
bearing capacity.
The course of the railway shows stable slopes in the sands. Nevertheless a protection for water through erosion control blanket (geotextile) and construction of a
dip gently slope is necessary because they guarentee a danger of slope fracture.
The acid ground waters are not suitable for the structural material because of their
10
Conny Lindner
aggressive behaviour against concrete. Therefore the problem is solved by using a
special concrete [Institut für Geotechnik TU – Freiberg, 2005].
Especially these soft cohesive or organic soils involve higher charges. Their
density, saturation value and permeability coefficient changes very strongly because of the inhomogenity in the material themselves which makes an analysis
more difficult and more expensive.
Anthropogenic problems
The railroad also comprises the crossing through several open pits which are restored (Bärwalde). Here it comes to artificial filling which are loosed, unconsolidated and large scaled stratified. The deposits possess a big thickness and are
coined of extreme irregular composition because of an intense imbrication of the
material. Because of that the following problems could appear: the inhomogenity
in the composition of the dump demands different non uniform settlements in the
surface of the dump and the dump itself and different load bearing capacities. At
uniform sand the possibility of settlement flow and settling problems while the
ground water is increasing exist. So the slope stability is also endangered [Schanz,
Witt, 2002]. Furthermore it comes to the variation of the ground - water reservoir
and therefore variation of the water stage – discharge relation because of local
interstratifications of different materials.
At the moment open pit Reichwalde possesses an influence cone which has effects with a radius from 8km. The concerned sediments are predominantly dune
sands, valley sands and peats.
For the elimination of these problems a sealing of the subsoil as well as a temporary rising of the ground water table is possible. If the ground water table goes
down sands would be affected by settlements [Schanz, Witt, 2002]. In the case of
water rising leads to increases in the uniform sands because of the flotation.
Conclusion
The problems of the existing traffic embankments cannot be discussed in all its
variety in this paper. Furthermore there are scores of procedures for the safety of
the embankments which however demand further tests.
Furthermore the loadings because of the vibrations represent a future- orientated topic whose effects still could not be resolved. The topic itself represents a
multiplicity of problems which will supply geotechnics, hydrologists as well as
geologists with a future job.
References
Ingenieurgeologische Problemstellung an Trassen im Verkehrswegebau im Bereich von
Lausitzer Stauchendmoränen (Beispiel Bahntrassen) 11
BfN: Landschaftssteckbrief:Niederlausitz,
http://www.bfn.de/03/landschaften/steckbrief.php?landschaftid=84001
Döring – Koppatz, Ines: Zur Erarbeitung einer Zustandsanalyse für den Deich zwischen ADorf und B-Stadt an der Elbe. Zusammenfassung einzelner DIN – Normen. Freiberg: Geotechnisches Institut Bergakademie Freiberg.
Ehlers, Jürgen: Allgemeine und historische Quartärgeologie. Stuttgart: Enke. 1994
Geoprofil: Beiträge zum Niederlausitzer Braunkohlenrevier. Heft 1. Freiberg: VEB Geologische Forschung und Erkundung Freiberg. 1989
Institut für Geotechnik TU – Freiberg: Ingenieurgeologische Übungen I. Hochschulinternes
Lehrmaterial. Freiberg: TU – Freiberg. 2005
Institut für Geotechnik TU – Freiberg: Ingenieurgeologische Übungen II. Hochschulinternes Lehrmaterial. Freiberg: TU – Freiberg. 2006
Sächsisches Landesamt für Umwelt und Geologie: Geologische Übersichtskarte des Freistaates Sachsen 1:400000. Freiberg: Sächsisches Landesamt für Umwelt und Geologie Bereich Boden und Geologie. 1992
Sächsisches Landesamt für Umwelt und Geologie Bereich Boden und Geologie: Geologische Karte der eiszeitlich bedeckten Gebiete von Sachsen 1:50000. Blatt Niesky. Dresden:
Landesvermessungsamt Sachsen. 1999
Schanz, Tom, Josef Witt Karl: Geotechnikseminar Weimar 2002 Geotechnik im Verkehrswegebau. Heft 07, 1.Auflag. Weimar: Bauhaus – Universität Weimar Universitätsverlag.
2003
Striegler, Werner: Dammbau in Theorie und Praxis. 2. neubearb. Auflage. Berlin: Verlag
für Bauwesen. 1998
Türke, Henne: Statik im Erdbau.3. Auflage. Berlin: Ernst &Sohn.1999
Vogt, Norbert: Beiträge zum 5. Geotechnik – Tag in München Geotechnik beim Verkehrswegebau. Heft 38. München: Zentrum Geotechnik. 2006
Zentrales Geologisches Institut: Hydrologische Übersicht der Deutschen Demokratischen
Republik/ Hydrogeologische Grundkarte M33 – III Cottbus 1:200000. 1. Auflag. Berlin:
Staatssekretariat für Geologie.1970