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May 18, 2020 |
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May 18, 2020 |
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May 18, 2020 |
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May 18, 2020
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May 18, 2020 (Image: Distribution of damages in pipe jacking in Germany (source: IFB, Hanover 1993)) |
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May 18, 2020 |
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May 18, 2020 Today, the installation of gas, water and wastewater pipelines is still predominantly carried out using open trenches. In view of the numerous disadvantages associated with this method, it is imperative that trenchless pipeline construction be considered much more strongly in the future than it has been to date, as an alternative in the planning and construction of sewers and pipelines.
This module deals in detail with the numerous different types of shield machines, obstacle removal and possible errors in pipe jacking and their consequences.
After completing this module, you will have a sound knowledge of:
- limitations of the use of shield machines and
- errors and consequences of damage during pipe jacking.
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In these methods, jacking pipes [DINEN12889:2000] [ATVA125:1996] [Scher77a] [Stein85f] are jacked by pressing-in through the subsoil from a starting shaft to a target shaft with the aid of a jacking station or a main jacking station helped by intermediate jacking stations. Jacking in a straight or curved line path is made possible by means of a steerable shield machine positioned at the head of the first pipe. Operation and steering of the shield … |
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Sep 14, 2005 Trenchless Technology for Installation of Cables and Pipelines Shield machines with partial excavation by hand (hand shields) (Image: Open cowl shield with spiral conveyor for spoil removal and hydraulically extendable breast plate for gravel-sand soils without groundwater (external diameter 4280 mm) [FI-Eppin]) Natural support of the working face is always applicable when the existing subsoil is free of groundwater and the working face is a priori stable (working face without support) or is sufficiently supported by a self-forming earth wedge with a natural slope angle.… |
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Sep 14, 2005 Trenchless Technology for Installation of Cables and Pipelines Shield machines with partial excavation by hand (hand shields) With partial support, the surface of the working face is divided into sections and is either supported by means of natural partial support on bench plates (bench (plate) or platform shields) and/or by means of mechanical partial support using breast plates (Bild 9.2.1.1.2). With bench shields, this division into sections has the purpose of reducing the length of the earth wedge and the size of the surface area of the slope [Scher77a]. Depending on … |
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Sep 15, 2005 Trenchless Technology for Installation of Cables and Pipelines Shield machines with partial excavation by hand (hand shields) The use of hand shields is recommended wherever very short jacking distances make the use of mechanical excavation uneconomic due to the high initial investment for the complex machine technology. In trenchless installation they are mainly used for crossing of traffic lanes and jacking distances of less than 50 m as well as for excavating special cross sections such as rectangular or arched profiles with manaccessible cross sections (Abschnitt 3). |
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Hand shields are non-mechanised open shield machines in which the soil at the working face is loosened by hand using auxiliary tools (pickaxe, spades, shovels or pneumatic hammer) (Bild 9.2.1.1) (Bild 9.2.1.1) (Bild 9.2.1.1). The removal of the spoil is carried out with the aid of conveyor belts, transport carts or tracked conveying buckets (dump trucks) (Bild 9.2.1.1).
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Because of their relatively low costs and numerous possibilities for use in soil and rock free of groundwater, open shield machines with mechanical partial excavation enjoy a wide application for jacking lengths up to 1000 m [FI-Herreb]. Water retention measures (open water retention or groundwater lowering) are required when jacking in groundwater (Abschnitt 4.4) (Abschnitt 12.8.2). In the cases in which this is not possible or permissible, a closed … |
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(Image: Open cowl shield with spiral conveyor for spoil removal and hydraulically extendable breast plate for gravel-sand soils without groundwater (external diameter 4280 mm) [FI-Eppin]) Shield machines with special excavation and conveying installations have been developed, and used for special purposes. The features of these excavation tools are that the working face is only partially excavated at some points in the shield, e.g. more or less passively. |
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Shield machines with compressed air support are used [Krets72] :
The limits of use for jacking in compressed air are determined by [Krets72] :
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