UNITRACC - Underground Infrastructure Training and Competence Center

Shield machine types - overview

(Image: Overview of shield machine types)

May 18, 2020

Definition open shields

Open shields:
Shield machine without pressure tight sealing between the working face and the following pipe string [Stein05a].

Open shields do not have a pressure-tight seal between the working face and the subsequent pipe string. They are characterized by relatively good access to the working face and easy-to-use machine technique.

(Image: Hand shields - Overall view of a hand shield (external diameter 2098 mm) [FI-Nishi]) (Image: Open shield) (Image: …

May 18, 2020

Shield machines with partial excavation

Shield machines with partial excavation feature an open (SM-T1 or SM-T2) or closed shield (SM-T3 or SMT4) and partial loosening of the soil or material at the working face.

Shield machines with partial excavation of the working face are grouped according to the method of excavation into:

Shield machines with partial excavation by hand (hand shields)
Shield machines with mechanical partial excavation
Shield machines with hydraulic partial excavation

May 18, 2020

Definition closed shields

Closed shields:
Shield machines equipped with a pressure bulkhead between the working face and the shield tail in order to build up an artificial pressure at the working face [Stein05a].

(Image: Possible designs of boring heads for earth pressure balance shields - Shield with eight-spoke cutting wheel and circumferential rim (external diameter 3100 mm) [Breme])

Closed shields are – depending on the used pressure balancing fluid – executed with …

May 18, 2020

Shield machines with full-face excavation

Shield machines with full-face excavation (SM-V) differ from those with partial excavation (SM-T) in that they process and loosen the whole working face in one working step by means of a rotating boring head equipped with corresponding excavation tools.

(Image: Shield machines with full-face excavation - Working face with natural support SM-V1)	(Image: Shield machines with full-face excavation - Working face with mechanical support SM-V2)
(Image: …

May 18, 2020

Shield machines

May 18, 2020

Partial cutting machines - excavation machines

Excavation machines

(Image: Attention!) Excavation machines are used with shield machines with partial excavation. Operating and steering of the shield machine are carried out directly at the site by a machine operator who has a continuous view of the working face.
(Image: Shield machine with fixed installed boom cutting machine - With axial cutting head)	(Image: Axial cutter head of the boom cutting machine equipped with round shank cutter bits)	(Image: Principles …

May 18, 2020

Partial cutting machines - excavation machines

Excavation machines - classification

May 18, 2020

Partial cutting machines - excavation machines

May 18, 2020

Full-face cutting machines - design of the cutting head

Design of the cutter head

May 18, 2020

Full-face cutting machines - design of the cutting head

Cutting wheel

(Image: Three-spoke rim cutting wheel with scraper teeth (standard bore head) [FI-Rasa])

The cutting wheel is a largely openly designed drilling head that is not used for the mechanical support of the working face. Their advantages lie with the low coverage and thus the good accessibility of the working face when needed. A distinction is made between the spoke and the rim cutting wheel [Maidl98].

(Image: Possible designs of boring heads for earth …

May 18, 2020

Full-face cutting machines - design of the cutting head

Scraper cutting head

(Image: Scraper cutting head with pick bits and scraper teeth (standard bore head) [FI-Rasa])

Scraper cutting heads are nearby, closed, disc-shaped boring heads or cutting wheels with adjustable or fixed supporting plates with soil entry openings that are adapted to suit the size of the maximum particle to be transported.

(Image: Open shield machine with scraper cutting head and mechanical support of the working face - Variably adjustable soil …

May 18, 2020

Full-face cutting machines - design of the cutting head

Rock cutting head

(Image: Rock cutting head with disc cutters and TCI insert roller cutter for hard rock [FI-Rasa])

Rock cutting heads consist of almost closed, disc-shaped basic constructions with usual slot-shaped entry openings (removal slots) and are flat with a rounded periphery, slightly coned or almost convex.

(Image: Rock cutting head of a shield with fluid support of the type AVN 1500 for jacking in rock - view)

May 18, 2020

Full-face cutting machines - design of the cutting head

May 18, 2020

May 18, 2020

Rippers

May 18, 2020

Buckets and Cutting Knifes

May 18, 2020

Round Shank Cutter Bits

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Roller cutters

May 18, 2020

Force distribution at the disc cutter

(Image: Attention!)

With increasing stability and/or hardness of the rock and rolling speed of the disc cutters the temperature and wear of the single discs increases [Schad03].

(Image: Forces affecting the disc cutters ? single disc cutter with reference to [Schad03] [Image: S&P GmbH])

Forces affecting the disc cutters - single disc …

May 18, 2020

Centre cutters

Centre cutters are excavation tools arranged in advance in the centre of the boring head in order to release the pressure in the centre of the working face during boring and especially in cohesive soils such as clay and silt with low to high plastic properties to counteract sticking of the boring head.

May 18, 2020

Possible combinations of different excavation tools

(Table: Combination possibilities of the various excavation tools as well as the utilization of stone crushers with reference to the subsoil conditions)

May 18, 2020

Backloading - exchange of excavation tools

(Image: Pros and cons)

Backloading:
In shield machines with full face excavation, special attention must be paid to the possibility of changing the excavation tools without changing the support conditions of the working face. One method to securely and easily perform the task underground without withdrawing the machine from the back of the drill head is the so-called backloading system.

The advantages of the backloading system:

Tools can be changed …

May 18, 2020

Excavation tools

May 18, 2020