Err Icb 1 Sec6 B4(Cw)
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Err Icb 1 Sec6 B4(Cw) Err Icb 1 Sec6 B4(Cw) Document Transcript

  • Energy Resources Rail LLC Section 6-B4: Civil Works SECTION 6-B4: CIVIL WORKS Table of Contents 1 CIVIL WORKS .................................................................................................................................. 2 1.1 GENERAL ............................................................................................................................... 2 1.2 DESIGN OF BOX CULVERTS ................................................................................................ 4 1.3 CONSTRUCTION DETAILS ................................................................................................... 5 1.4 PREFERENCE FOR BOX CULVERTS .................................................................................. 5 1.5 ROAD CROSSINGS (ROAD OVER RAIL .............................................................................. 6 1.6 PIPELINE CROSSINGS (RAIL OVER PIPELINE).................................................................. 7 1.7 HYDROLOGICAL CULVERTS................................................................................................ 8 1.8 DRY RIVERBED CROSSING (RAIL OVER DRY RIVERBED) ............................................ 10 1.9 ANIMAL MIGRATION PATH ................................................................................................. 11 1.10 CONCLUSIONS .................................................................................................................... 11 File No. ERR-ICB-1-Sec6-B4(CW) 1
  • Energy Resources Rail LLC Section 6-B4: Civil Works 1 C IV IL WOR K S G eneral Because of the topography in the region adjacent to the line, tunnels and wide valley bridges are not necessary and therefore only small bridges (box culvert type), hydrological culverts, and animal migration paths are considered. The locations of box culverts and hydrological culverts are shown in the alignment concept. Several types of culverts have been chosen and are presented in the following table. Approx. Name Description Line Section Number Length [m] km 000+000 to 0 Road over Rail km 042+500 Rail Culvert Crossing km 42+500 to 7 End km 000+000 to Actual 0, but km 042+500 might change Rail over Pipe Pipeline Bridge before start of Line Crossing km 42+500 to railway End construction km 000+000 to Construction for 68 Hydrological km 042+500 Hydrological 3 and 5 Culverts km 42+500 to Balance 53 End km 000+000 to Rail over Dry 0 Dry Riverbed km 042+500 Riverbed 2 x 15.6 Bridge km 42+500 to Crossing 2 End km 000+000 to Under rail 0 Animal km 042+500 Crossing 5 Migration Path km 42+500 to (Culvert) (20)* End * Included in Hydrological Culverts For the design of the civil structures international standards are to be used. Only for the clearance in rail underpasses should the American standards should be used, allowing with Diesel Locomotive Traction the possible use of double stack containers which is used in the US but not in Europe. Each rail under passing will be designed and constructed for double track use. File No. ERR-ICB-1-Sec6-B4(CW) 2
  • Energy Resources Rail LLC Section 6-B4: Civil Works All crossings of the railway line with roads, pipelines and other obstacles are designed as road or rail overpasses. Level crossings have not been taken into account for safety reasons because accidents will occur when road signals and gates are ignored. Accidents also occur when animals cross the line. Therefore the entire line will be fenced on both sides. In general, the option of the rail passing under the road was chosen since these culverts are cheaper (railway induces higher loads therefore more resistance of the culvert and more materials are needed). Another reason is that the clearance of the trucks in Mongolia is in some cases very high and existing regulations are ignored, which increases the height and consequently the amount of material needed for the culvert. But since only a few culverts have been designed as road passing under rail the cost reduction through reduced clearances would be minimal. The recommended box culvert types are less costly than conventional bridges with bearings. Furthermore these box culverts incur lower maintenance costs and are safer in cases of earthquakes. Box culverts are an alternative to bridges. They are an especially good option when dry rivers have to be crossed. The culverts consist of prefabricated square units of high strength reinforced concrete which are connected to each other by joints. Since the units are prefabricated, the construction time is considerably reduced as compared to a structure cast in place and the length of a culvert can easily be adapted to the obstacle to be crossed. If the contractor proves and decides that small bridges are more advantageous than culverts, concrete bridges instead of steel bridges should be chosen because of the high and increasing price of steel. Furthermore the maintenance costs for concrete bridges are generally 0.9% of the investment costs, whereas maintenance costs for steel bridges are 1.5 %. Concrete is also more suitable for the climate in Mongolia than steel which is more sensitive to corrosion; this is another reason for the higher maintenance costs of steel bridges. The economic life of steel bridges is 80 year on average; the economic life of concrete bridges and culverts is 100 years. This is another argument to prefer the concrete type structures. If in the case of bridges abutments are constructed, a drainage system behind the abutments must be installed that prevents the build- up of water pressure. In any case of a drainage system, the soil permeability should be high enough for water infiltration into the sub base. Pipeline crossings, if any (especially with regard to water pipelines) shall be designed as rail bridges. The alternative is to lead the pipeline over the rail line but this is not recommended with regard to safety aspects of the pipeline and the interruption of the pipeline during railway construction and possibly during railway maintenance and repair works. Every type of crossing may have a different size of bridge or culvert depending on the required span. In order to keep investment costs low, a standard culvert design has been chosen for similar rail and road crossings. When the bid documents are prepared each structure can be adjusted to the individual site situation by only minor changes. File No. ERR-ICB-1-Sec6-B4(CW) 3
  • Energy Resources Rail LLC Section 6-B4: Civil Works Des ign of B ox C ulverts Proven structural software shall be used for structural design using the Finite Element Method. The calculations have to consider conditions such as: o Dead loads are mainly a result of weights. Live loads result from trains on the track respectively cars on road over rail crossings and vice versa. o In case of road bridges (box culvert type) the design shall be planned for a 60 ton vehicle with two axles. Additionally, it is recommended to add a 10 ton wheel load as specified in European Codes. It is required to provide a support walk way on bridges along the main lanes, the load of which can be determined as 5 kN/m². o Temperatures in the South Gobi (to be confirmed by the contractor) are:  Average maximum temperature – July 30.9°C  Average minimum temperature – December/January -19.7°C  Average daily temperature variation 15.7°C  Design maximum temperature (1% exceedance) 35°C  Design minimum temperature (1% exceedance) -27°C o Mongolian Design Code soil freezing depths are:  Clay soils 1.7 m  Sandy soils 2.1 m  Gravel soils 2.5 m Temperature differences between the top and bottom of superstructures lead to additional tension, and it depends on the construction of tarmac or ballast which values have to be used. Locomotive braking and acceleration loads, horizontal handrail loads, and wind loads have to be taken into account as a minimum. 25 ton axle load and a maximum train speed of 100 km/h have been chosen but the speed of freight trains will be below 100 km/h. As a result, speed resonance problems can be prevented by maintaining the conditions as above. Otherwise it would be necessary to calculate the resonances for each structure. Structures covered by soil like frames are not in danger during earthquakes except when crossing active faults. Since they are very insensitive to earthquakes these structures File No. ERR-ICB-1-Sec6-B4(CW) 4
  • Energy Resources Rail LLC Section 6-B4: Civil Works were chosen whenever possible. In addition to this they need no bearings, the superstructure cannot collapse and the piers are usually stiffer. Nevertheless, the nature of the sub base and the foundations are important factors for the resistance of structures against earthquakes. This must be verified during the detailed design phase. To improve the durability of the structure, a concrete cover of at least 50mm shall be implemented. In order to prevent that any water contact with structural concrete a waterproofing layer has to be provided. At the top of the superstructure slab, two layers of waterproofing membrane have to be provided. The walls shall be coated with three layers of bituminous painting. The waterproofing membranes shall be protected against damage by a layer of concrete on top of the superstructure slab. In addition, sulphate/chloride resistant cement shall be used, where necessary. Frames are covered with soil and ballast. Due to this fact, the elasticity of the sub base is close to the elasticity value of the embankment section. A small difference in elasticity between the structure and the earthwork has a positive influence on the trains running comfort. The crossing angle between track axis and the axis of the structure will be as close to 90 degrees as possible, so that the sleepers are uniformly supported and future maintenance is reduced. To prevent road vehicles from accidentally falling on the track, guardrails shall be installed. The impact forces of derailed trains as specified in European and UIC Standards shall be considered but this does not rule the design. Guardrails shall be installed inside the running rails where the track passes through the box culverts; these guardrails serve as a precaution. The clearance gauge shall take the possibility of double stack container traffic into account. This also allows installing a 25 kV overhead contact line.. There is no significant difference between the clearance heights; therefore the proposed culverts can be used for both cases. However, electrification excludes double stack container traffic and vice versa. C ons truc tion Details Railway structures have to be protected against damage during construction, .g. the concrete cracking must be prevented. Appropriate measures must be taken to protect fresh concrete against rapid curing, rapid drying and overheating. The requirements of the European standards must be taken into account. Other relevant issues have been given with the section: Design of Box Culverts. P referenc e for B ox C ulverts Frame structures have a number of advantages: File No. ERR-ICB-1-Sec6-B4(CW) 5
  • Energy Resources Rail LLC Section 6-B4: Civil Works o The monolithic connection between superstructure and substructures gives more stability. o Earthquake safety is much higher because they are no bearings that can be damaged. The collapse of the superstructure is impossible. o Most maintenance costs are caused by the repair of bearings, caps and superstructure expansion joints. The frame structures have been chosen where possible because they do not have bearings. o In addition, most of the box culverts are covered with soil and ballast and do not require superstructure expansion joints. In this way maintenance costs will be kept low. o Another advantage of box culverts is their high resistance against structure resonance because the substructures stabilize the superstructure. o The use of soil covered box culvert structures will prevent interference between sub ballast layer, cables and draining water that runs off easily. o Furthermore the infrastructural design can be adjusted very easily to the normal embankment section above the box culvert with regard to changes of size of cable ducts, electrification, etc… The box culvert types considered for this project are described in the sections below. R oad C ros s ings (R oad over R ail The most often used structure leads roads over single or double track railway lines. Preference shall be given to the double track crossing that allows doubling of the track at a later time. Single track crossings shall only be considered if there are constraints by the surrounding area. The characteristics given with Table 6.5.5 – 1 shall apply. Crossed Traffic Number of Spans Inner Width Number of tracks Route Any Road 1 7.8 x 8.4 m single Any Road 1 12.3 x 8.4 m double Table 6.5.5 – 1: Types of Road Crossing Structures The Road over Rail Crossing has a higher safety level for train operation. In case of a car accident there will be only a small risk to the railway due to the guard rails. Figure 6.5.5 – 1 shows a side view of a double track Road over Rail Crossing. File No. ERR-ICB-1-Sec6-B4(CW) 6
  • Energy Resources Rail LLC Section 6-B4: Civil Works Figure 6.5.5 – 1: Side View of a Double Track Road over Rail Crossing The advantage of Road over Rail Crossing is the fact that the gradients of roads can easily be adjusted. This results in fewer earthworks. It would be more expensive to lead the rail over the road because the maximum vertical gradient of rail is lower than the one used for roads. As a result investment and maintenance costs are relatively lower. P ipeline C ros s ings (R ail over P ipeline) This kind of structure guides a single or double track rail over a pipeline The pipeline crossing is given as example in case pipelines will be constructed within the rail corridor before the opening of the railway. The recommended types are given with Table 6.5.6 – 1. The safety of the pipelines is a very important aspect. It is essential not to block the File No. ERR-ICB-1-Sec6-B4(CW) 7
  • Energy Resources Rail LLC Section 6-B4: Civil Works pipeline with the structure. When building bridges the location of pipelines cannot be changed in order to keep the pipelines working. Crossed Pipeline Number of Spans Inner Width Number of tracks Small 1 1.4 x 1.4 m double Small 1 1.4 x 1.4 m single Medium 1 3x3m double Medium 1 3x3m single Large 1 9x7m double Large 1 9x7m single Table 6.5.6 – 1: Types of proposed Pipeline Crossing Structures The proposed structures provide sufficient clearance for the pipeline itself and provide enough space to work at it. Normally, pipeline corridors must provide for additional pipelines. The flexible design proposed allows placing additional pipelines easily. Figure 6.5.6 – 1 shows a pipeline under bridge. 1.7 Hydrologic al C ulverts These types of structures support the hydrological balance in the areas with regard to the rain water flow in dry riverbeds. The types given with Table 6.5.7 – 1 shall apply. Hydrological culverts of minor size are not considered as separate structures but are included in the permanent way design and shall be placed according to the needs established during the detailed design. File No. ERR-ICB-1-Sec6-B4(CW) 8
  • Energy Resources Rail LLC Section 6-B4: Civil Works Figure 6.5.6 – 1: General Layout of Pipeline Crossings (1span 3x3m) Crossed Area Number of Spans Inner Width Number of tracks Minor 1 1.4 x 1.4 m double Minor 1 1.4 x 1.4 m single Small 1 3x3m double Small 1 3x3m single Large 1 5x5m double Large 1 5x5m single Table 6.5.7 – 1: Types of Hydrological Culverts In dry riverbeds flooding resistance of the structures is essential. In case of flooding the whole structure shall resist. Where necessary, gabions are recommended as washout protection. In some locations flood water volumes and levels ares expected that exceed the capacity of a single culvert.. If more than one culvert is necessary the flexible design allows placing the culverts in a row parallel to the rail axis as given with Figure 6.5.7 – 1. File No. ERR-ICB-1-Sec6-B4(CW) 9
  • Energy Resources Rail LLC Section 6-B4: Civil Works Figure 6.5.7 – 1: Side View of Hydrological Culverts (3cell 1.4x1.4m) 1.8 Dry R iverbed C ros s ing (R ail over Dry R iverbed) This structure carries single or double track lines over dry riverbeds. The box culverts over dry riverbeds shall be constructed for a double track line. The types as given with Table 6.5.8 – 1 will apply. Crossed Area Number of Spans Inner Width Number of tracks Medium 2 15.5 x 6.8 m double Table 6.5.8 – 1: Types of Dry Riverbed Crossing Figure 6.5.8 – 1 shows a single span dry riverbed crossing box culvert as an example. The frame construction has a good flooding resistance. In the event of flooding the whole structure will resist. The monolithic culverts can be arranged in multiple and will also withstand the power of flooding water. Furthermore gabions are recommended as washout protection. The high clearance offers sufficient space for a maximum of flooding water. In cases of smaller distances between the rail track and the bottom of the dry riverbed the height of the prefabricated structure is adjusted by lowering the structure into the ground. This depends on the site conditions. File No. ERR-ICB-1-Sec6-B4(CW) 10
  • Energy Resources Rail LLC Section 6-B4: Civil Works Figure 6.5.8 – 1: Single Span Dry River Crossing Box Culvert (example) 1.9 Animal Migration P ath The entire railway line shall be fenced in order to prevent interference with railway operations. In addition to the road over-passes crossings for local people, domestic and wild animals shall be provided. Over–passes may be the preferred solution but under–passes shall be installed because of the higher maintenance costs of over-passes.. Therefore the following is suggested: o Line section from km 000+000 to km 040+00:: owing to the heavy mining activities in this area no animal migration paths shall be provided. o Line section from km 040+000 to the end of the line: about twenty hydrological box culverts with the inner size of 5 x 5 m shall be placed as animal migration paths according to the recommendations of the Environmental Impact Specialist. These large size hydrological box culverts shall substitute small size hydrological box culverts, and if necessary shall be relocated to newly defined places. 1.10 C onc lus ions The feasibility study proved the feasibility of the freight rail line in the South Gobi Region of Mongolia. For the next steps the following is proposed: o The requirements of the clients (Employer’s Requirements) shall be fixed such that the detailed design in these areas can be specified. File No. ERR-ICB-1-Sec6-B4(CW) 11
  • Energy Resources Rail LLC Section 6-B4: Civil Works o The maximum flooding has been estimated by visual terrain survey. It is important for the Contractor t carry out a hydrological study for checking dry riverbed crossings by statistically estimated floods. o All structure locations shall be checked by detailed earthquake research and detailed geological investigations for each location of a structure. o The requirements of Mongolian Roads, normal and heavy vehicle roads, for example clearances and maximum vehicle weights, shall be fixed. o The dimensions of structures have to be determined more precisely in the detailed design by the contractor. File No. ERR-ICB-1-Sec6-B4(CW) 12