Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
Customized state-of-the-art segment production
Jörg Riechers
Product Manager, Herrenknecht Formwork Technology GmbH, Germany.
ABSTRACT
Efficient mechanized tunneling projects, using segments for its structural lining, depend on a
harmonized segment production at highest standards in segment quality and accuracy. As a result of a
consequent product management, Herrenknecht Formwork has successfully established itself as the
world market leader for the supply of segment moulds, handling equipment and carousel plants. Up to
now, more than 4,000 moulds were manufactured for 140 realized projects. Herrenknecht Formwork
designs and supplies customized equipment for any type of segment production at highest standards.
With three workshops in Germany, Slovenia and China, Herrenknecht Formwork is able to offer and
manufacture equipment at short notice and in outstanding quality. Due to short project lead times and
an increasingly growing demand, contractors often rely on mould manufacturers’ project experience
with regards to the selection of a suitable variant of segment manufacturing, determination of suitable
sets of moulds for an efficient manufacturing as well as on comprehensive concrete and curing
concepts.
Based on increasing world-wide interest in multipurpose tunnels, enabling either a temporary or
permanent use of its overall or partial structure for more than the essential purpose, Herrenknecht
Formwork is aware of the importance of cutting-edge developments. Especially for tunnels with
®
segmental lining, for conveyance of water and sewage water, Combisegments has been developed.
This segment embedded corrosion-protective liner (CPL) is extended by a liner frame and a
mechanically integrated gasket, whereby e.g. welding at radial and circumferencial joints and
conventional gasket gluing become obsolete. In addition, Herrenknecht Formwork is active in the field
of thermally activated tunnel structures, whereby conventional segmental lining is turned into a heat
exchanger for heating of municipal properties.
This paper compares segment productions using immovable stand moulds and a manufacturing
carousel with associated handling equipment. In this context, influencing factors such as tunnel length,
regional labour cost, lead and assembly time as well as cycle times of segment production are taken
into consideration. In addition, new and promising product developments are introduced.
INTRODUCTION
Each tunnel project is individual as regards technical requirements, geographical, topographical,
infrastructural, climatic and – most important – geological aspects. Therefore, the segment production
plant has to be exactly adapted to the local conditions of the project. This is the only way of ensuring
that each segment is in the right place at the right time as well as in required quality. This presents a
huge challenge to the planners and contractors, to ensure that reinforcement production, concrete
mixing, segment production and handling merge into in an optimal workflow for installation in the
tunnel.
Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
th
Together with the first use of mechanical tunnel boring machines in the 19 century, technical
solutions for pre-fabrication of reinforced concrete segments were developed stepwise. Based on
increasing project demands, on both accuracy and efficiency of segment manufacturing, two types of
manufacturing established themselves: stationary segment production and carousel production.
SEGMENT PRODUCTIONS IN SPOTLIGHT
Stationary production
A stationary production line is characterized by a precisely defined positioning of used segment
formworks during production. Consequently, the moulds are fixed on the floor during the whole
production period (Figure 1). Concrete can be supplied both by trucks, specially developed flying
bucket systems with concrete distribution buckets as well as by means of overhead cranes.
Figure 1: Stationary segment production (left) and connection of vibrator interface to the mould (right)
[Herrenknecht Formwork, 2011].
In order to ensure an efficient concrete compaction, vibration is supplied either by pneumatic or
electrical vibrators and distributed by its fastening positions underneath each formwork bottom.
Both vibratory methods enable supply of sufficient vibration energy at usually 6,000 RPM, although
systems differ both in terms of investment costs and costs for installation but as well with regards to
possibilities for adjustments and synchronization of frequency and RPM of used vibrators.
Latter aspects directly affect quality of concrete compaction related to parameters as concrete slump
and influencing natural frequency of concrete moulds. Operating manuals and maintenance
recommendations should be considered by all means, independent of chosen equipment.
An accelerated concrete curing can be achieved either by integrated heating installations, located in
the base frame of each mould, or by means of heating tubes/ radiators installed on the factory floor
(Figure 2). In order to achieve optimal curing conditions in terms of temperature and humidity,
furthermore, tarps or insulated hoods for covering each mould are used after filling and compaction.
Figure 2: Heating tubes / radiators pre-installed at the later position of neighbored moulds [Herrenknecht Formwork, 2010].
Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
Carousel production
In contrast, when concrete segments are produced by means of a carousel system, the moulds are
moved on rails to pass different working stations for the purposes such as mould cleaning, concreting,
finishing, etc. For curing, the filled moulds are moved in a special curing chamber with an appropriate
heating system and afterwards pre-stored indoor before being stacked outside near to the segment
plant.
The main elements of the carousel plant are as follows (Figure 3):
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Concreting system with concrete hopper, concrete supply, automatic mould cover for large
moulds (if required), concreting table, concreting chamber
Carousel-type rail system, thrust bars, cross transfer trolleys with rail system, clamping
Reinforcement supply with monorail and magazine for reinforcement cages
Heating system with curing chamber, heating, pipes
Demoulding equipment, e.g. vacuum lifter
Finishing and evacuation line including rotator, gasket gluing station (if necessary, please refer
to Combisegments®), etc.
Figure 3: Carousel segment production [Herrenknecht Formwork, 2009].
The carousel plant is equipped with several control units for automated operation of the different
components such as movement of the moulds on the rails by means of thrust bars, movement of the
cross transfer trolleys, movement of the cranes, doors of the curing chamber, handling equipment,
etc., thus reduction in the share of manual works.
The core part of the carousel plant is the concreting chamber. With its automatic doors, its steel/ brick
structure with noise insulating panels and its control panel separated from the concreting chamber by
a window, it guarantees a maximum of safety and noise reduction (issue of working without ear
protection) with less manpower required (Figure 4). After concreting and stripping the surface, the
filled moulds are pushed into the curing chamber where they remain usually for approx. 6 to 10 h in
dependence of e.g. the segment size, characteristics of the concrete, ambient temperature. The curing
chamber guarantees optimum conditions for a controlled and accelerated concrete curing due to
adjustable heating radiators (55 – 65°C). To improve the efficiency, moulds are often covered with
tarps, in order to create high humidity at a certain temperature beneath cover and concrete surface.
Optionally, a steam distribution system in the chamber can be used to control humidity conditions
(Figure 4). Especially in the beginning of the curing phase, a sufficient supply of heat and humidity
accelerates the curing process, i.e. hydration of cement.
Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
Figure 4: Operation panel for the concreting station (left); filled moulds in the curing chamber (right)
[Herrenknecht Formwork, 2013].
For each type of production, appropriate handling and logistic equipment is required and made
available according to customer requirements by Herrenknecht Formwork. When starting planning of a
segment production plant, construction companies, precasting companies and suppliers of the
equipment have to choose the appropriate production type and related equipment. They are usually
facing the question of advantages and disadvantages of each production type related to a certain
project. Therefore, the most important selection criteria have to be defined, for example as follows.
Criteria for selection of the production mode
As already mentioned in the introduction, the local conditions of the project are crucial for selection of
the production mode. However, there are further aspects that have to be considered: number of TBMs,
expected advance rate, project time, production time and schedule, setup time, space requirements,
labour requirements versus availability of (skilled) labour, cost of labour, project budget, forecast for
follow-up projects as well as climatic conditions. In the following, these aspects will be pointed out and
their influence on the selection of the production mode shall be explained.
Local conditions
Local conditions have to be divided into different categories either referring to location of the tunneling
site or national regulations regarding safety, working time, importation of goods, etc..
When the project is located in a large city, for example, space requirement of the production plant is
one of the decisive criteria. If there is already an existing precast plant, stationary moulds can be
integrated into the existing factory more easily. By contrast, in case of a remote tunneling site, logistic
and infrastructural conditions have to be determined and evaluated. Here, for example, a just-in-time
supply of the necessary wear and spare parts for a highly automated carousel plant could be
challenging.
Figure 5: Remote project location in Palomino, Dominican Republic [Herrenknecht AG, 2008].
In addition, the wage level of the country has to be considered. In a country with low wage costs,
stationary production tends to be more efficient as personnel costs would probably be lower than the
additional cost for the automated carousel plant.
Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
As regards the national regulations, some countries, for instance Brazil, impose strict safety
regulations, i.e. one person may only be responsible for one special function. In such a case, the
approval for a stationary production plant, usually operated by a certain number of teams with
alternating tasks, is rather difficult to obtain. In contrast, an authorization for a carousel plant with only
few people responsible for the same production procedure would be comparatively easier. Customs
procedures are another important aspect. In some countries, customs clearance of complex
equipment, including parts from different suppliers, lead to delays in shipment. Non-functioning
carousels, due to missing equipment or required spare parts, cause expensive production downtimes.
Tunneling – advance rate
Precast concrete segments have to be available in the tunnel just-in-time in order to guarantee
continuous advance of the TBM. As storage capacity is restricted in most of the cases, the segment
production speed has to be adjusted to the tunneling speed. Segment production speed can mainly be
defined by the number of sets of moulds used as well as the number of working hours per week.
The latter is often limited by national regulations. By the way, a set of moulds consists of a certain
number of segments required for forming a segmented ring. According to Herrenknecht Formwork’s
experience, the number of production cycles with each set of moulds per day is 2 - 3 for carousel
plants and in dependence of the optimization degree between 1 - 2 and 2 up to 3.25 for stationary
moulds. However, from the aspect of tunneling speed alone the appropriate production mode cannot
yet be derived, as both systems are able to fulfill such requirements, as for example stationary moulds
with an efficient heating system, together with favorable climatic conditions, sufficient qualified
employees within a team of colleagues used to working together can achieve more than three
production cycles per day as a best performance.
Project time schedule/ setup time
This aspect may be decisive in case of a tight project schedule. Due to the high degree of automation,
the carousel system requires more time for conception, design, construction and setup compared to
stationary mould production lines. Further, a more intensive and time-consuming training of the
operator’s personnel is required which in turn leads to minor cost increase.
In order to get an impression, stationary moulds can usually be commissioned within e.g. one or two
weeks (depending on the number of moulds, personnel capacity, etc.), whereas commissioning of a
carrousel production plant takes e.g. two to three months (depending on the scope of supply and
services). This period, however, strongly depends on the client’s support for preparation works,
e.g. construction of a suitable foundation for the segment plant, and provision of suitable personnel.
Expected operation period of the plant
The calculated operation period often depends on the tunnel length or also on the overall
infrastructure development of the region or country, i.e. if any subsequent projects can be expected.
In case of a short operation period, a stationary production would probably be more efficient as a
carousel solution. Comparatively higher investment cost for additional carousel equipment cannot be
justified in case of a small-series production. In contrast, if the number of segments required is
comparatively high in combination with large dimensions, which is basically attributable to the tunnel
length and diameter, the operator could benefit from the lower personnel requirement of the carousel.
Otherwise, this saving of personnel cost could be offset the higher the investment costs of the
carousel equipment. In case of different projects to be realized in a certain area, the carousel plant
can easily be adjusted and re-used for follow-up construction lots/ projects, even for rings with different
diameters. In this case, the number of sets of segment moulds required for each diameter would be
smaller compared to stationary production. Thus, it is important to determine and evaluate important
parameters resulting in a balanced calculation.
Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
Comparison of different aspects
Time, available land plot, personnel requirement, production capacity
The following Table 1 briefly summarizes differences between selection criteria and indicates labour
requirements and costs as well as an assumption of usually required time for the entire chain from
design to production launch. This comparison reflects a metro project with an internal diameter of
5,400mm, external diameter of 6,000mm, ring configuration 6+1 using segments with right / left
conicity and a width of 1,400mm. The tunneling job itself and the segment manufacturing have been
executed in Moscow. In order to evaluate efficiency of production methods for a required avg. casting
capacity of 15 rings/ day, a stationary production plant with eight sets of moulds at seven moulds/ set
has been compared with a carousel production plant which only requires six sets of moulds.
Table 1: Differences in assumed requirements for stationary and carrousel productions.
Assumed requirements (avg.)
Carrousel production
with 6 sets of moulds
Stationary production
with 8 sets of moulds
Period for conception of the factory
(hours of supplier)
approx. 200 h
(batching plant and cranes not included)
approx. 100 h
Period for design and construction
approx. 800 h
(without evacuation/ finishing line)
+ 600 h for moulds
= total: 1,400 h
approx. 600 h
Plot of land
a) for production line
b) for indoor storage with evacuation line
a) 18m x 65m = 1,170m²
b) 18m x 55m = 990m²
a) 21m x 85m = 1,785m²
b) 21m x 50m = 1,050m²
total approx. 2,000 m²
total approx. 2,835 m²
Period for assembly, commissioning and training of client’s
personnel (weeks)
7 – 10
2-4
Labour for assembly, commissioning and training of client’s
personnel (labour of supplier)
4 – 6 persons
1 – 2 persons
Additional personnel from the client for setup
(usually made available by the client)
15 – 20 persons
5 - 6 persons
Effort for maintenance per month
approx. 50 h
approx. 16 h
Personnel for production per shift
(please refer to Table 2)
13 – 14 persons
22 – 25 persons
Requested avg. production capacity
15 rings/ day
15 rings/ day
Scheduled production cycles per day
(assuming 24 working hours);
higher rates possible in other projects
2.5 - 3
max. 2
Production rate (rings/ day)
15 - 18
16
It should be noted that given figures on daily productions cycles are related to this specific reference
production and precasters schedule of production. By means of an example, during segment castings
in Abu Dhabi at CCI, outstanding performances up to 3.25 cycles/ day could be achieved at average
rates of 3 cycles/ day. Table 2 summarizes different types of work necessary for production of precast
segments, divided in types of production. The numbers listed refer to recent project experience with
the metro project in Moscow and similar projects. It should be noted that indicated information depend
basically on required production capacity related to project aspects as well as on the qualification of
available personnel, national health and safety regulations, etc..
Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
Table 2: Comparison of necessary works for production and the required number of persons.
Required type of work (job steps)
Carrousel production
employees per shift
Stationary production
employees per shift
Demoulding
2
3
Cleaning of the mould
2
3
Preparation of mould: installation of insert
parts and reinforcement
2
3
Closing of the mould and final check
1-2
2-3
Concreting
1
3-4
Finishing
3
3
Covering of filled mould
0
2
Turning, storage
2
3-4
Total number of employees
13 - 14
22 - 25
Based on previously discussed influencing parameters and this project example, it becomes clear that
several criteria have to be considered referring to the tunnel project itself, e.g. tunnel length, tunneling
speed and project schedule as well as local conditions, e.g. infrastructural, social, and environmental.
Therefore, without considering these aspects, it is not possible to state that a carrousel system is
favorable in general. Comparatively, small but important equipment accessories such as vibrators
(pneumatic or electrical) offer potential for further improvements of production efficiency.
The presented reference project and related comparison between both production modes show clearly
that each of both can fulfill the requested production rate. Based on experience of Herrenknecht
Formwork the following net diagram (Figure 6) shows essential decision criteria and its emphasis
related to each production mode.
Personel for production
1
Assembly,
commissioning, training
0,75
Labour costs
0,5
0,25
Design and conception
0
Production capacity
Stationary
Required land plot
Occupational safety
Investment costs
Carousel
0,5: basis = stationary mode
1:
higher (effort/ capacity/ quality)
Figure 6: Net diagram for illustrating differences between production modes by means of different criteria.
In this specific case, two different precasters have chosen a carousel production after internal and
external consultation. The land plot of precasting plants is located in Odinzovo, a city with limited
available industrial areas, not far from Moscow. In addition, higher production rates in this specific
case at low labour requirements per shift including safety issues influenced their decision. This
tendency can be confirmed by a close look on already 27 carousel production plants being designed
and assembled by Herrenknecht Formwork. Geographically, they are distributed as follow: 14 in
Europe & Russia, 8 in South Central America, 3 in Asia & Pacific and 2 in Israel. The majority of all
carousels were located in an urban area in densely populated regions. Nevertheless, as a conclusion,
it can be highlighted that a careful, detailed assessment of the above mentioned aspects at the
beginning of the project is crucial for a successful and cost-efficient segment production and
consequently for a successful tunnel project.
Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
CUTTING-EDGE SOLUTIONS FOR PRECAST CONCRETE SEGMENTS
Especially for segmental lined tunnels with highest demands on durability, e.g. for conveyance of
water and sewage water, Herrenknecht AG
and Herrenknecht Formwork
developed
Combisegments®. The designation Combisegments® describes a composite product consisting of a
common reinforced concrete segment incorporating an advanced corrosion resistant lining element.
Based on first project experience with Combisegments in Moscow in 2009 using GRP as lining
material, further improvements have been implemented in order to achieve both highest quality
standards and a simplified usability during segments manufacturing and tunneling.
A Combisegments® lining element consists of a Telene®-pDCPD (poly-dicyclopentadiene) corrosionprotective liner, extended by a liner frame and a mechanically integrated gasket, whereby e.g. welding
at radial and circumferencial joints after/ during tunneling becomes obsolete.
Manufacturing of Combisegments® can be integrated into usual production cycles without additional
equipment or additional training of labour. Based on its design, a Combisegments® lining element is
simply placed centered at the bottom of the Combisegments®-mould, with its smooth surface facing
the base plate. Mechanical fixation of this liner is achieved after closing mould shutters by means of an
integrated groove system. After demoulding, fastening of required sealing frames by means of
adhesive, resulting in additional effort for the precaster, is no longer required due to already integrated
EPDM gasket within the Combisegments® lining element (Figure 7). Thus, investment for a gasket
gluing station is not necessary as well as costs for consumables, application tools and additional wage
costs do not apply (cf. chapter Segment Production in Spotlight).
Figure 7: Combisegments®-mould (ID 2000) - handling demonstration [Herrenknecht Formwork, 2013].
Based on increasing world-wide interest on multipurpose tunnels, enabling either a temporary or
permanent use of its overall or partial structure for more than the essential purpose, Herrenknecht
Formwork is active in the field of thermally activated tunnel structures, whereby conventional
segmental lining is turned into a heat exchanger for heating of municipal properties. The so called
Energy Lining Segment “Energietübbing®” was developed by the companies Ed. Züblin AG and
REHAU AG & Co..
Together with Herrenknecht Formwork, three world-wide known companies have jointed their
expertises to provide tailored concepts and equipment turning tunnels into a source of renewable
energy. Energy lining segments are equipped with absorber pipes fastened at the reinforcement cage.
By integrating coupling pockets into segments, achieved by using special mould components, access
to protruding absorber pipes is achieved, whereby segments respectively erected rings can be
connected to thermal cycles after tunneling (Figure 8).
Jörg Riechers | CBIP Segmental Lining Conference, Delhi, India, 26th February 2014
Figure 8: Energietübbing® with absorber pipes (red), fixed to a reinforcement cage
[Ed. Züblin AG, Geotechnical & Tunneling Division].
SUMMARY AND CONCLUSION
In summary it can be stated that besides core competences in design, manufacturing and delivery of
perfectly project harmonized equipment increasing demands are being placed on equipment
manufacturer. Throughout the entire project cycle a holistic consultancy and service is increasingly of
importance and, in turn, offers business opportunities for experienced solutions suppliers.
By means of an exemplary metro project in Moscow criteria for the selection between methods of
segment production stationary and carousel have been discussed. It became apparent that the
decision between stationary and carrousel production depends on numerous infrastructural and
economic aspects and should be based on a thorough evaluation of all criteria relevant for the
corresponding project. In addition to this competence, two cutting-edge solutions were introduced:
®
Combisegments and Energietübbing®. Combisegments® meets requirements on durability with
simultaneous advantages during production and tunneling. Unlike conventional liners, this solution
enables one-pass segmental lining without subsequent welding at radial and circumferencial joints,
after being manufactured accelerated without the need of a gasket gluing station. Based on increasing
world-wide interest in multipurpose tunnels, the Energietübbing® - Energy Lining Segment turns
tunnels into a source of renewable energy.
Since being a well-experienced system supplier with a modern philosophy and a wide-ranging team of
experts in mechanical engineering and civil engineering, Herrenknecht Formwork meets the challenge
to develop, design and supply customized solutions for state-of-the-art, sustainable traffic and utility
tunneling.