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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Structural Calculations of Liners Inserted by the Grouted-in-place Lining Process The characteristic bearing behaviour of the liner under a constantly increasing bending load with normal force can be divided into two different phases, whereby it behaves differently depending on the sign in front of the bending moment e.g. from the direction of bending. The first phase is defined in that the maximum acceptable tensile stress is not yet attained in the injection grout, e.g. the liner is still in a non-cracked condition (condition … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Structural Calculations of Liners Inserted by the Grouted-in-place Lining Process The basis for carrying out the structural calculations are the cross sectional values of the wall structure being used. These are not only dependent on the material and the geometry but also on the loading. The Bild 5.3.2.6.2.3, Bild 5.3.2.6.2.3 and Bild 5.3.2.6.2.3 show the loading ability of liners of various wall thicknesses produced according to the grouted-in-place lining process, whereby the thickness of the HD-PE hose is 2 mm in all cases and … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Structural Calculations of Liners Inserted by the Grouted-in-place Lining Process At the start of the calculation it is assumed that the whole of the circular cross section is in condition I. In the first step, the effects corresponding to the loading form are increased to the point where the loading capability of the cross section is reached for the first time. Depending on the direction of bending, this is the point where the cross section transfers to condition II, that is, the bending stiffness is lowered in a small region … |
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Nov 23, 2004 Structural Calculations of Liners Inserted by the Anchor Hose process |
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Nov 23, 2004 The force F for pulling-in a continuous pipe with rise or fall (Bild 5.3.2.6.3.1.1.1) is determined from the equation [FI-Hoech] : (Formula: Calculation of the tensile force for pulling-in a continuous pipe) (Image: Tensile force F and gradient reference to [Koch85] [FI-Hoech] [Image: S&P GmbH])The tensile force F with the cross section A creates the tensile stress (Bild 5.3.2.6.3.1.1.1), which must be smaller than the permissible tensile strength … |
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Nov 23, 2004 When pulling-in curved piping, the sum of the created individual extensions with pulling and bending of 3 to 4 % must not be exceeded. If an extension of 2 % is permitted during pulling-in, then the permissible extension caused by bending in the region of the curve is still approx. 1 to 2 %. (Formula: Permissible extension)As a criterion for the determination of permissible bending radii, one must view, on the one hand, the kinking, for small relationships … |
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Nov 23, 2004 |
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Nov 23, 2004 (Image: Pull head with pin connection with reference to [FI-Hoech] [Koch85] [Image: S&P GmbH]) The permissible tensile forces are limited not only by the tensile stress but also by the stresses arising in the region of the pull head. Depending on the design of the pull head, the forces are transmitted to the pipe via a welding joint (for welded-on pull-in cone), a flange joint with welding collar or a bolted connection (Bild 5.3.2.6.3.1.2.1). The … |
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Nov 23, 2004 The tensile forces determined above must be smaller than the permissible forces given in Tabelle 5.3.2.6.3.1.2. (Table: Permissible tensile forces for PE-HD pipes to DIN 8074 or DIN 8075 and PP copolymer pipes to DIN 8077 or DIN 8078 Part 2 at 20 °C (at 40 °C the values must be multiplied by the factor 0.6) (Hoechst AG)) |
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Nov 23, 2004 In the grouting of the annular space between the old pipe and the pulled-in HD-PE pipe with a material of specific gravity γD > γR (γR = specific gravity of the pipe), the ungrouted HD-PE pipe is subjected to the force (Bild 5.3.2.6.3.2.1) : (Formula: Strain of the HD-PE pipe by means of the annular space filling) (Image: Buoyancy force Fv with reference to [FI-Hoech] [Koch85] [Bild: S&P GmbH])For a pipe filled with water with the weight of the water … |
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Nov 23, 2004 When grouting the annular space, a hydrostatic pressure Ph(Bild 5.3.2.6.3.2.2) acts on the pipe. This pressure must not be greater than the permissible buckling pressure pk.perm of the pipe in order to avoid damage (Bild 5.3.2.6.3.2.2) [WRC90]. From Bild 5.3.2.6.3.2.2 there can be taken for pipes of HD-PE and PP copolymer the buckling pressures pk with reference to the time of the various pipe rows or pressure loads at 20 °C. For higher temperatures, … |
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Nov 23, 2004 The following discussions for the structural calculation of the liner are based substantially on the Hoechst AG publication "Technischen Dokumentation - Rohre aus Hostalen GM 5010 T2 und Rohre aus Hostalen PP" (Technical Documentation for Hostalen GM 5010 T2 and Hostalen PP pipes) or their corresponding publications [Meldt82] [Koch85] (see also [Britt86]). As regards loading of flexible pipes with hydrostatic external pressure see Abschnitt 5.3.2.6.1. |
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Nov 24, 2004 If the inserted pipe without annular space is used as a pressure pipe, then the pipe including pipe joints and fittings must be so sized that it can absorb the internal pressure during the desired lifespan - in the municipal field at least 50 years. This is valid also for the case that the annular space is grouted and the grouting material, including the old pipe still cannot absorb the internal pressure. In this case, the inserted plastics pipes … |
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Nov 24, 2004 (Image: Loading due to hydrostatic pressure [FI-Hoech] [Koch85]) If the pipes to be rehabilitated lie in the groundwater region, then with leaking or porous pipes, the plastics liner is loaded by the groundwater column above the pipe middle point (Bild 5.3.2.6.4.2). For un-grouted gravity operated HD-PE pipes without side support effect, for instance, the buckling pressures pk determined in the investigations to Bild 5.3.2.6.3.2.2 are then valid. … |
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Nov 24, 2004 If the pipe-soil system to be rehabilitated is not by itself able to bear the loads, then a structural calculation must be carried out for the plastics pipe. In the Federal Republic of Germany, the structural calculation for drainage sewers and pipes is carried out in accordance with ATV-A 127 [ATVA127b], whereby for plastics pipes this is based on a permissible deformation of 6 % after an operational time span of 50 years. For a pipe laid according … |
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Feb 16, 2011 The coefficient of linear extension of HD-PE and PP pipes is approx, 0.17 mm/(m·K). If a plastics pipe is anchored between two points then, due to the prevented thermal expansion, pressure is built up on warming and tensile stress on cooling. In the temperature region of -40 ° C to +20 ° C investigated, a tensile stress of 9.3 N/mm2 was measured for cooling and a compressive stress of 5.8 N/mm2 for warming. These stresses, which relax over the course … |
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Nov 24, 2004 In case I (Bild 5.3.2.6.4.2) the internal pressure for rigid piping generally forms the decisive load condition whereby an accompanying effect of the grouting material or the old pipe is not included for reasons of safety. For a given internal diameter di and internal pressure pi, there is applicable for the calculation of the wall thickness with a constant assumed stress distribution, that is, ignoring thick walling: (Formula: Formula: Calculation … |
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Nov 24, 2004 Besides the general proofing processes presented in Abschnitt 5.3.2.6.1, other proofs must be carried out because of further loads and these must be taken into account in the calculation of linings. |
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As already mentioned in Abschnitt 5.3.2.1, a distinction is made between complete lining between non-self-supporting or structurally unstable and self-supporting or structurally stable lining systems. The structurally non-self-supporting complete linings cannot carry any additional loads and must be securely fixed mechanically to the carrier cross section i.e. the sewer to be rehabilitated. In contrast to this, structurally self-supporting complete … |
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The calculation and continuous monitoring of the jacking process is an important tool for the prevention of damages in order to secure:
(Image: Crack formation as a consequence of splitting tensile stresses due to unbalanced load introduction into the pipe faces) |
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Jun 01, 2004
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Decisive for the size of the total earth or water pressures are the soil characteristics of the in-situ soil and the depth of the groundwater level. Should information on the earth characteristics from a geotechnical report (Abschnitt 4.5.2.5) not be available, the values must be taken from DIN 1055 [DIN1055c] or the "Empfehlungen des Arbeitsausschusses Ufereinfassungen" (Recommendation of the Working Committee on Banks (of rivers)) [EAU1990] (Tabelle … |
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