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The minimum distances to neighbouring utilities and structures depend on:
In case that minimum distances cannot be adhered to, special protective measures such as open cut excavation at the crossing points must be taken in order to prevent the transfer of loads. (Image: Underground utilities in … |
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Soil deformation is generally defined as the horizontal or vertical positional change of the soil surface or a point inside the soil. Vertical soil deformation in the direction of the ground surface is called heaving and in the opposite direction is referred to as subsidence, settling or settlement. |
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Subsidence is the vertical displacement of an entire soil layer (stratum), as a result of soil movement at a great depth. In this case, the size of the displacement can be determined, but not its timing [Schmi96]. Settling occurs in granular soils due to a sudden rearrangement of the grain particles caused by the addition of water. For loosely compacted soils, this settling can amount to up to 5 % of the layer thickness, and for densely compacted … |
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May 13, 2020 (Image: Soil deformation during pipe bursting as per [TTC2001]) |
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(Image: Target manhole - capstan winch) (Image: Tension sensor) (Image: Overload protection [Jürge05]) During the pulling-in process, the value of the allowable tensile forces on the new pipe must be strictly enforced. This is accomplished by continuous monitoring (measurement and documentation). Methods of tensile force monitoring:
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(Image: Target manhole - capstan winch) Pulling devices automatically limit the tensile force to the predetermined maximum value. Additional systems for the measurement and documentation of the tensile forces on the pulling device (cable winch) include electronic monitoring gauges and detailed printout reports. In some cases, these devices also have a PC interface for convenient data transfer. |
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In order to receive real time data from the pulling head, a data cable must be inserted ahead of the new pipe and connected to a computer. Otherwise, the data can only be collected after the completion of the pulling-in of the new pipe. (Image: Tension sensor) |
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As a reference, the following table shows the allowable tensile forces for PE 100 pipes for a load duration of 30 minutes (according to the German DVGW working sheet GW 323: Trenchless replacement of gas and water supply pipelines with pipe bursting; Requirements, quality assurance and inspections / not available in English at present). (Table: Allowable tensile forces for PE 100 pipes under a 30 min load) |
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The rupture strength of HDPE pipes is 2.5 times the allowable tensile strength [DVGWGW323]. The cross sectional area of a pipe section used as overload protection may only amount to 40 % of the cross sectional area of the new pipe being pulled in. (Image: Overload protection in form of a predetermined breaking point by reduction of the wall thickness) (Table: Example calculation of an overload protection for HDPE 100 used in pipe bursting) |
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Illustrated example of the steps involved in the manufacturing of the overload protection in the form of a predetermined breaking point. (Image: Step 1: New pipeline) (Image: Step 2: Wall thickness reduction) (Image: Step 3: Welding on of the overload protection) (Image: Step 4: Removing the weld seam) |
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A cross section reduction is obtained by reducing the effective circumference of the pipe or the effective cross-sectional area. (Image: Overload protection in form of a predetermined breaking point by reduction of the effective pipe circumference) (Table: Overload protection) |
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Congratulations! You have successfully finished this module. Next you will have the opportunity to review the newly acquired knowledge with an interactive questionnaire. You can still navigate back to any point in the lessons if you wish to review a specific point or subject. Stay curious! |
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May 13, 2020 This module focuses on the pipe bursting method as a special method of replacing gas, water, and wastewater pipelines in the same alignment. In addition to the functional principle, the requirements on materials and equipment are presented in detail. After completing this module, you will have a sound knowledge of:
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Today, supply and discharge lines are still predominantly installed by using the open-cut method: a trench is dug, the lines are installed. Under the protection of an embankment or sheeting and the trench is filled afterwards. In the face of the numerous disadvantages as well as the citizens' growing environmental consciousness in the future it is urgently necessary to take trenchless technology into account much stronger than until today as an alternative … |
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Jacking pipe: (Image: Reinforced concrete jacking pipe) (Image: Jacking pipes of different diameters and … |
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Jacking pipes have a double function: They constantly support the excavated cavity and, in the case of a single shell lining, they provide the structure of the pipeline (final lining). (Image: View into the jacking pipes) (Image: Reinforced concrete jacking pipes) (Image: Example of the final lining of a pipeline tunnel) |
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In trenchless installation, casing pipes, host pipes, utility ducts and utility tunnels act as cavity security and for carrying or supporting the actual product pipe(s). (Image: Functional classification of jacking pipes) |
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(Image: Materials for jacking pipes) |
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