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(Image: Realisation of pipe bursting from the insertion manhole to the reception manhole) Manhole to manhole: Utilization of discrete pipes and bursting equipment suited to the size of the manhole structure. (Image: Realisation of pipe bursting from the insertion manhole to the reception pit) Manhole to pit: Utilization of discrete pipes and bursting equipment suited to the size of the manhole structure. Installation of the pulling equipment in the pit. |
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(Image: Realisation of pipe bursting from the insertion pit to the reception manhole) Insertion pit to manhole: Installation of the pulling equipment in the manhole or above it. The discrete pipes or the continuous pipeline, together with the bursting unit, is inserted through the insertion pit. The size of the bursting unit is accordingly dimensioned as to allow for its removal from the target manhole. (Image: Realisation of pipe bursting from insertion … |
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(Image: Connection of the new pipeline to the manhole) Connection of the new pipeline to the manhole: The connection between the new pipeline and the manhole structure must be properly sealed so that water cannot infiltrate into the surrounding soil. A leaktight joint must be created between the manhole wall and the new pipe. The manhole channel and benching must be accordingly fitted to the new pipeline. (Image: Re-connection of a lateral to the new … |
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Dec 20, 2013 (Image: Gravity pipeline) The following materials are commonly used in the production of gravity, protection and product, pipelines: (Table: Commonly used types of new pipelines for the pipe bursting of gravity systems with reference to [DWAM143-15]) |
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Dec 20, 2013 Other pipe types include: (Table: Other types of new pipelines qualified for the pipe bursting of gravity systems with reference to [DWAM143-15]) |
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Dec 20, 2013 (Image: Gravity pipeline) If polyethylene pipes are to be used, only PE 100 or PE-Xa pipes specified by the DVGW Worksheet (GW 335-A3 and GW 335-A2) should be considered.
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Dec 20, 2013 (Image: Rohricon) When using PE pipes for gas and water supply lines, the SDR series listed in the tables apply. (Table: SDR-series for pipe bursting - Water supply pipelines) (Table: SDR-series for pipe bursting - Gas supply pipelines) |
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Dec 20, 2013 (Image: Rohricon) Steel and cast iron pipes
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(Image: Qualitative decription of the pneumatic bursting process with reference to [Falk95b] [Image: S&P GmbH]) (Image: Model of a cylindrical cavity expansion in ideal elasto-plastic material with reference to [Zimme88] [Image: S&P GmbH]) The first phase of the so-called Secondary condition I involves the bursting of the old sewer and the radial displacement of the pipe fragments and the surrounding soil. Subsequently, the soil settles into the overcut ( … |
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Dec 20, 2013 (Image: Groove and notch formation caused by pipe breakage fragments) The destruction of the old pipe wall from the inside and the displacement of its fragments into the surrounding soil can lead to damages to the new product pipeline. The service life of product pipelines installed using the pipe bursting method is greatly reduced by :
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Dec 20, 2013 Grooves and notches can occur in all pipe materials. According to DVGW, grooves of up to 10 % of the wall thickness are permissible for pressure pipelines. Plastic pipes are especially prone to grooving because of their material properties. (Table: Characteristics of the E-modulus (short term and long term) for various materials) |
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Dec 20, 2013 The displaced old pipeline fragments lead to the creation of point loads on the new pipeline which can cause peak stresses and thus cracks in the pipe wall. Therefore, plastic pipes should be highly resistant to stress cracking. Information on the slow crack growth of a pipe material is provided through the Notch or FNCT test. The point load test in combination with a creep rupture test is another method. (Image: Experiment set-up for the Notch-Test … |
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Dec 20, 2013 Peak stresses due to point or line loads occur especially with large fragments. First theoretical investigations in this respect showed stress differences in the pipe of up to 400 % for differently shaped fragments with the same assumed soil stresses [Naneg88]. |
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Dec 20, 2013 The Notch-Test according to ISO 13479 or DIN 33479 is a modified creep rupture internal pressure test in which the failure points are defined as four evenly distributed notches about the circumference (apex angle 60°, the notch depth equals to 20 % of the wall thickness). The test is carried out with a constant hydrostatic internal pressure in an 80 °C water bath until fracture occurs. (Image: Standstill periods for the Notch-test with reference to [… |
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Dec 20, 2013 With the FNCT test, sharp-edged circumferential notches are cut around small test rods which are loaded to failure under a constant tensile stress of 4 N/mm2 in a 80°C water bath. (Image: Full-Notch-Creep-Test) |
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Dec 20, 2013 (Image: Point load test with reference to [FI-Hesse] [Image: S&P GmbH]) The point load test for pipes installed on sand bedding using the trenchless method involves applying an external point load to the pipe. The 10 mm-diameter indentor pin is pressed into the pipe wall up to a defined depth (depression = 0.06 · De) at room temperature. The test piece is then subjected to a creep rupture test. |
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For pipelines installed using the bursting method, the following two influences must be considered in the static calculations:
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(Image: Qualitative decription of the pneumatic bursting process with reference to [Falk95b] [Image: S&P GmbH]) The static calculations of pipes for loads lateral to the pipeline axis are to be carried out according to [DWA-A 161]. Although this calculation method is geared towards pipe jacking, it does offer results that also apply to the pipe bursting procedures. In a more exact static calculation according to the finite element method (FEM), substantially … |
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In comparison with the structural calculation according to [DWA-A 161] for pipe jacking, the pipe bursting includes additional load-increasing influences caused by the ruptured old pipe, which are however compensated for by the load-reducing forces of the process itself. Conclusion: A structural analysis according to [DWA-A 161] produces results that have a greater safety factor. (Image: Point load test with internal pressure with reference to [Jürge05] [… |
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