Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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