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imageShield Tunnelingn Method


The Naka Ochiai shield tunnel extends approx. 2,020m starting from the vertical departure shaft at Rikkyo Street in Toshima Ward as far as the Nakai Oedo Line subway station building in Shinjuku Ward, and is constructed by the earth pressure balance shield method. This shield has the outer diameter of the machine is 12.02m, making it the largest diameter earth pressure balance shield in the world. The outer diameter of segmetal lining is 11.8 m. With an earth coverage of between 9 -24m, and running underneath some major city center trunk roads as well as being constructed adjacent to important structures such as railway lines and bridge pier foundations, make the construction conditions extremely severe.
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(Presented by Metropolitan Expressway Public Corporation)




Large Variable Section Tunnel by MMST Method



The Multi-Micro Shield Tunnel (MMST) method is the name given to the method for making tunnels where the outer perimeter wall structure, called an 'outer lattice', is first formed by excavation by numerous small rectangular shield machines, of which adjacent sections are then linked together by reinforcing bars, and then filled up with concrete to form the overall large section rectangular tunnel, after which the soil within the internal section is then excavated.
The special characteristic of this method is that the spacing of the elemental tunnel sections formed by the small scale rectangular shield machines can be controlled, so that the size of the tunnel can be varied. For this tunnel, the spacing was changed from 0.6m to 1.6m, thus increasing the inside section area by more than 15%.
(Presented by Metropolitan Expressway Public Corporation)






Compact Shield Method



(1) Integrated secondary lining type segment
Until now, after the primary lining, the secondary lining was constructed using in-situ concrete. The functions of the secondary lining to prevent corrosion, act as waterproofing and to smooth the internal surface of the tunnel are kept, but this method uses one-piece integral segments with the same anti-corrosion qualities instead of the in-situ concrete, placed on the inside of the primary lining segments.
(2) 4- piece 3-hinge lining structure
Compared to the standard segment for shield works (Japan Sewers Association), the number of pieces was reduced, and a statically determinate 4- piece 3-hinge segment was adopted, which forms a safe and stable tunnel structure
(3) 3-part shield machine including following-on internal equipment.
By preserving enough work space behind the shield machine, following-on equipment work was accommodated in the shield machine. Furthermore, as divided into 3-parts, the structure allows for easy starting and withdrawal. As a result, the size of the departure and arrival shafts was reduced by 30%, and multiple re-use of the shield machine also became possible.
(4) Tire-mounted Transportation wagon
Usually, materials and excavated soil were transported using battery locomotives on rails and sleepers. In this method, the invert ditch formed in the secondary lining integral segment acts as a guide for a self-steering tire-mounted transportation system. As using this method, the invert becomes the walk path, walking becomes both easier and safer
 This method was in May 2003 given technically innovative appraisal by the Japan Society of Civil Engineers, and was awarded a Technical Development Prize.
(Presented by Bureau of Sewerage Tokyo Metropolitan Government)





F-NAVI


Recently, for the construction of power cable tunnels by the shield method in city street areas, it has become an issue to carry out high speed construction because of increasing tunnel distances from the vertical shaft, and from the viewpoint of reducing cost and shortening the construction schedule. From this background, the construction of the shield tunnel works (length 1,934m, internal diameter 3.0m, excavated external diameter 3.61m) of the 2.8km long 220kV
Kurume Branch Line Works in Fukuoka Prefecture, the F-NAVI Shield Method, was applied. Using RC segments and a sliding steel wagon muck removal method, a progress rate of over 500m per month was achieved. The F-NAVI Shield Method, as described below, is able to
carry out high speed construction by controlling the direction of excavation during coincidently advance, Coincident advance is where the tunnel excavation work and segment erection work are done at the same time. Furthermore, in the F-NAVI shield machine, the articulation joint structure connecting the main body and front body parts features a semi-spherical shape bearing surface, allowing the front body to move freely in both horizontal and vertical directions, so the excavation direction can be controlled irrespective of the selection of the shield jacks operation by reducing the high thrust force at the following items were carried out:
_ Test Construction of thrust reduction (excess excavation volume, sliding materials etc)
_ Carrying out F-NAVI coincident excavation construction using manual operation by increasing the number and capacity of the jacks.
_ Software for transformation to completely automatic operation by increasing the number of propulsion jacks during simultaneous excavation.
From the results, using manual operation of the F-NAVI simultaneous excavation from February 2001 and then carrying out completely automatic simultaneous excavation from March 2001, and using sliding steel muck wagons and RC segments, we were able to confirm the main construction by F-NAVI coincident construction. In addition, a maximum monthly progress rate of 526m was recorded based on actual daily operation.
The factors for the success of this high speed construction method are:
_ Reduction of assembly time of RC segments by using one-touch connection method.
_ Carrying out F-NAVI coincident excavation construction using manual operation by increasing the number and capacity of the jacks.
_ High accuracy of the direction control using the head swivel mechanism and positional control system of the F-NAVI shield machine.
_ Application of sound proofing of the temporary earth storage yard allowing construction during day and night.
_ The ability of the following-on rear equipment to achieve the assumed 500m monthly progress.
By using this high speed construction shield method, we were able to reduce the tunnel construction work schedule by 2 months, and open the electrical transmission facilities for operation by June 2003

(Presented by Kyushu Electric Power Co., Ltd.)






Coincident Segment Erection / Shield Driving System


 Recently, due to social needs for cost reduction, longer distance drive and shorter construction period are being expected for shield tunneling. The double jack coincident excavation shield method, compared to conventional shield machines, allows for the difficult erection of segments coincidently together with tunnel excavation, speeding up the construction schedule and thus making it possible to shorten the construction schedule.
 The machine developed for this system is equipped with a drum that can slide inside the machine. The drum has two types of jack; one is specifically used for excavation and is fitted on the front side of the drum, and connects the drum to the main body of the machine. The other is mainly used for segment erection and is fitted on the rear side of the drum. Equipped with these two types of jacks, excavation work and segment erection can be performed concurrently, thus making it possible to shorten the construction period.
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 For the sequence of excavation and erection, by pushing forward with the excavation jack, the whole shield machine is moved forward and as excavation is carried out, the erection jack is extended and segments are assembled into place.
 This method was adopted for use on the Yarimizu Shield JV Project for a part of the water mains works commissioned by the Tokyo Metropolitan Government Water Works Bureau.

(Presented by Kajima Corporation)





Mucking System using Pneumatic Dispatch Capsule for Vertical Shafts


 Recently, although the depth of underground structures has been progressing, for methods used until now for the removal of muck waste by using a lifting bucket, concerns remain on the safety aspects associated with the scattering of soil and accidents from rope breakage, and also the self-weight of the rope markedly decreasing the transportation efficiency. Furthermore, although studies have been made for underground construction at depths of around 1,000m, demands exist for the development of rope-less and highly reliable systems for the movement of goods both for during construction and after completion.
 This technique is for transporting excavated debris from a tunnel, which has then been placed in a hopper at the base of the shaft, and which is then loaded into a capsule, which is then sent to the ground surface inside a vertical transport shaft using a pneumatic dispatch system.
 The special features of this technique are that the air drive source can be used and be applicable even for vertical shafts of depths around 1,000m, and that transport speed of around 3 times more can be achieved compared to current bucket systems. In addition, as it is transported inside a closed shaft, soil and dirt can not fall out onto below, high levels of safety can be preserved, and using compact equipment and the efficiency of energy saving systems, and the automatic transportation system can reduce manpower and thus reduce costs, and expectations exist for the further application of mucking and vertical transportation systems at great depths using this technique.
 This technique has been adopted for use for mucking in the vertical shaft of the Numakuma Sewerage Tunnel works, part of the sewer works commissioned by Hiroshima Prefecture.
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( Presented by Kajima Corporation)




QB Segment



 Recently for Shield tunnel projects, reducing cost by omitting secondary linings and increasing the length of tunnels etc., are major objectives and the QB (Quick Block) segment has been developed in response to these.
 The QB segment has segment joints using a concrete butt joint structure, and ring joints using a pin joint (DS (Locked Disc Spring). It also forms a smooth inner surface and thus it makes high-speed construction possible.
In cases where the ground is relatively good, axial forces are predominant, making the tunnel stable, and it is rational in the design for the segment joint parts to use simple butt joint structures, as a splicing effect can be expected between the segment rings.
 The notable characteristics of the QB segment are that as steel joint pieces are reduced and the structure simplified, the cost of the segments is reduced; due to the smooth inner face the secondary lining can be deleted; the segments need only to be inserted in the axial direction by the erector or shield jack and then erected, so making high-speed construction possible and improving construction safety.
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( Presented by Kajima Corporation)




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