GB2057541A - Building a shaft on a submerged tunnel - Google Patents

Abstract

The object of the invention is to provide a method for building a shaft on a submerged tunnel, e.g. a railway tunnel, comprising caissons (10, 3) which are connected successively under water which method can be performed without unduly delaying the construction of the tunnel itself. The method of the invention is characterized by incorporating into the train of caissons (10, 3) a shaft caisson (4) with a joint portion on the upper side thereof at a predetermined shaft building spot; stabilizing the shaft caisson (4) if not already stable; and stacking and joining a number of shaft blocks on the shaft caisson (4) to build a shaft (25) of a desired height thereon. <IMAGE>

Description

SPECIFICATION Building a shaft on a submerged tunnel This invention relates to a method for building a shaft (e.g. ventilation tower) on a submerged tunnel which is constructed under water, for example under the water of a river or the sea, for laying a railway or for other purposes.

The conventional methods for building a shaft on a submerged tunnel include: (1) A method of forming a bank in the water and performing the necessary building work by means of a pneumatic caisson; (2) A method of providing a dry yard by coffering to perform the building work; and (3) A method of submerging and installing the so-called floating caisson, which contains as an integral assembly a shaft and a caisson, on a foundation which is provided at the bottom of water.

However, the above-mentioned conventional methods (1) to (3) have the following drawbacks.

The methods (1) and (2) are very expensive and can only be carried out where the depth of water at the shaft building spot is not too large. On-the other hand, in the method (3), the floating caisson is simply left on the foundation until the installation of the adjoining caissons is completed, so that it is easily knocked down by the waves acting on the upright shaft portion or at the time of an earthquake. In addition, it becomes necessary to use a large crane ship for towing the floating caisson and to ensure a water depth large enough for the towing operation.

There has also been known a method in which a floating caisson is produced in the form of a number of separate blocks which are to be joined together under water This method presents a difficulty in that the installation work has to be postponed until the rigid connections of the joints between the respective blocks are completed. In any one of the above-mentioned conventional methods, the construction of the other part of the submerged tunnel is considerably delayed due to the work on the shaft.

It is a main object of the present invention to provide a method for building a shaft on a submerged tunnel without unduly delaying the construction of the tunnel itself.

The object can be achieved by the steps or the combination of the steps which constitute the present invention, which will become apparent from the following particular description of the invention, taken in conjunction with the accompanying drawings.

It is to be noted that it is possible to make modifications and alterations in details of the particular embodiment shown below, within the scope of the invention as defined in the appended claims.

The method according to the present invention comprises the steps of: incorporating into a train of caissons of a submerged tunnel a shaft caisson with a joint portion on the upper side thereof, at a predetermined shaft building spot; stabilizing the shaft caisson; and stacking and joining under water a number of shaft blocks on the shaft caisson to build a shaft of a desired height thereon. The shaft caisson may be placed on a foundation with its fore and rear ends joined with the ordinary caissons of the tunnel, and the lowermost shaft block is connectible to the upper joint of the shaft caisson on the foundation.

In order that the invention may be more fully understood, an embodiment in accordance therewith will now be described with reference to the accompanying drawings, wherein: Fig. 1 is a diagrammatic vertical section of a submerged tunnel with a shaft which has been built according to the invention; Fig. 2 is a vertical section of a shaft caisson which is being positioned under water; Fig. 3 is a vertical section of the shaft caisson which has been joined with preceeding and succeeding ordinary caissons; Fig. 4 is a diagrammatic vertical section of a shaft block which has been joined to the upper side of a shaft caisson under water; Fig. 5 is a vertical section of the shaft caisson and shaft block, ready to receive a further shaft block;; Fig. 6 is a vertical section of a shaft built on a submerged tunnel, showing the height and length of the tunnel on the scale of 1/500 and 1/2000, respectively; Fig. 7 is a vertical section of a shaft block guide which is provided in the joint portion on the upper side of the shaft caisson; Fig. 8 is a plan view of the shaft block guide; Fig. 9 is a vertical section of a temporary partition wall which is provided in the upper joint portion of the shaft caisson; Figs. 10 and 11 are sectional views of the joint of the shaft caisson as coupled with an ordinary caisson; Fig. 1 2 is a vertical section taken on line A-A of Fig. 13, showing the shaft block of Fig. 5 on an enlarged scale; Fig. 1 3 is a vertical section taken on line B-B of Fig. 12;; Fig. 14 is a vertical section taken on line C-C of Fig. 13; Fig. 1 5 is a plan view of the shaft block of Fig. 13; Fig. 1 6 is a vertical section showing a mechanism for correcting the verticality of the shaft blocks; and Fig. 1 7 is a vertical section of coupled joints of the shaft caisson and shaft block.

The present invention is hereafter described in connection with the construction of a double-track railway tunnel shown in Fig. 1. In the first place, a trench (not shown) is formed at the bottom of the water in the same manner as in the conventional trench method, laying a foundation 1 at the spot where a shaft is to be built. A number of ordinary caissons 3 are laid successively in the trench toward the foundation 1 through approaches 2 which are provided on opposite shores. The respective caissons 3 are press-joined with an adjacent caisson through a rubber gasket under water pressure. Then, a shaft caisson 4 is submerged and fixed on the foundation 1.

The shaft caisson 4 has at its opposite ends joint portions 5a and 5b of a construction similar to the joint portions of the ordinary caissons 3 and on its top side a third joint portion Sc which is provided with a rubber gasket 6 around its circumference and a removable block guide 7 at each corner thereof. The joint portions 5a to Sc are each closed by a temporary wall 8 with a manhole, as shown in Fig. 9 joint portion Sc is shown by way of example). The shaft caisson is suspended by a crane ship over the installing spot for installation on the foundation 1 and submerged by loading a weight which is greater than the buoyancy of the caisson 4.

As shown in Fig. 3, after submerging the shaft caisson 4 onto the installing spot, the joint portion 5a at the front end is press-joined to the rear end of the connected ordinary caissons 3 through a rubber gasket under water pressure. Thereafter, the joint portion 5b at the rear end of the shaft caisson 4 is coupled with a terminal one of the series of ordinary caissons 10 which are laid to form a tunnel between a pair of shafts 4 (only one of which is shown) at opposite ends of the tunnel.

After laying all of the ordinary caissons 10 or after laying a sufficient number of ordinary caissons 10 (for the stabilization of the shaft), crushed stones or the like are back-filled over the caissons 3, 4 and 10 to stabilize the foot portion of the shaft.

The respective caisson are joined with each other by a joint construction forming a soft connection as shown in Fig. 10 or a rigid connection as shown in Fig. 11.

In the joint construction of Fig. 10, the caissons 3 and 4 are clamped together by PC cables 12 which are passed through longitudinal cases 11 of the respective caissons, gripping a rubber gasket 13 in the joint gap 14. The gap 14 is further sealed by an "5" type rubber plate 16 which is located within a recess 1 5 on the inner side of the gap 14 and which is clamped in position by washers 17 and bolts 18. The recess is covered by a 9 mm thick steel plate 19 which has one side thereof fixed to one caisson and the other side longitudinally slidably disposed on the other caisson.

In the joint construction of Fig. 11, a rubber gasket 13 is gripped in the joint gap 14 between the two caissons to be joined and a 25 mm thick steel plate 20 is fixed in the recess 1 5 to seal the joint gap 14 which is primarily sealed by the rubber gasket 13. The reinforcing iron rods 22 which extend longitudinally out of the two caissons 3 and 4 are connected in the recess 1 5 by iron rods 23 of 25 mm diameter. The recess 1 5 which is closed by a 1 9 mm thick steel plate 21 is filled with concrete or mortar 24.

Referring to Fig. 3, the joint portion Sc on the upper side of the shaft caisson 4 which has been joined with the ordinary caissons 3 and 10 is coupled under water with the lowest one of the shaft blocks 25a which are stacked and joined one on the other until a predetermined height is attained as shown in Fig. 1.

Each shaft block 25a is provided with upper and lower joint portions 26 the construction of which is similar in its principle to the joint portions of the ordinary caissons. The upper joint portion 26 is provided with a rubber gasket 6 around its circumference and with a block guide 7 at each corner. In addition, the upper and lower joint portions 26 are closed by temporary partition walls 8.

The first shaft block 25a is submerged and joined to the shaft caisson 4 under water by the following steps. The succeeding shaft blocks 25a are joined to each other in a similar manner so that the description in this regard is omitted.

(a) The shaft block 25a is towed to and supported in a suspended state at the installing spot by a crane ship or other suitable means, and then submerged by loading a weight which is greater than the buoyancy of the block 25a, as shown in Fig. 3.

(b) The block 25a is slowly lowered onto the shaft caisson 4 along the block guides 7 with the aid of a diver. As soon as the block 25a is seated on the rubber gasket 6, the crane wire is slackened to remove the hoisting load.

(c) After checking the uniformity of compression and the adherence of the rubber gasket 6 which has been compressed by the load of submersion, the diver opens a suction valve and a drain valve (not shown) which are provided in the temporary partition wall 8 of the shaft caisson 4 beneath the shaft block 25a, draining water from the space between the opposing temporary partition walls 8.

(d) Thereafter, a worker enters the space between the opposing partition walls 8 through a manhole 9 in the lower partition wall 8 to check the uniformity of compression of the rubber gasket 6 and the verticality of the shaft blocks 25a, while the diver removes the block guides 7 and hooks 27 for reusing.

(e) In a case where the verticality of the shaft block 25a falls outside the predetermined range, four or five hydraulic jacks 30 are set up in the recess 29 which is formed between the joint portion 26 of the shaft block 25a and the joint portion Sc of the shaft caisson 4 on the inner side of the joint gap 20 with the rubber gasket 6, as shown in Fig. 1 6. thereby correcting the verticality of the block 25a. After correcting the verticality into the allowable range, steel material is inserted into the recess 29 to support the shaft block 25a in the corrected vertical position and the jacks 30 are removed.

(f) The shaft caisson 4 and the block 25a are united by forming the rigid joint construction of Fig. 7 within the recess 29. More particularly, a 25 mm thick steel plate 31 is fixed on the inner side of the joint gap 28 with the sealing rubber gasket 6 and the temporary partition walls 8 in the united portion are removed. Next, the ends of the longitudinal reinforcing iron rods 32 which project out of the shaft caisson and block are connected by welding thereto a 25 mm diameter iron rod 33, and a steel plate 34 which serves as a molding wall and a siding is fixed to close the opening of the recess 29. The recess 29 is then filled with mortar 35.

When the shaft block joining work has proceeded to a stage where part or whole structure of the shaft block to be joined is positioned above the surface level of the water, it becomes necessary to employ a crane ship or other lifting means which is capable of supporting the total weight of the joining shaft block 25a in step (a).

The above-described operations, which are similar to the joining operations for the ordinary caissons, are repeated to build the shaft 25 as shown in Fig. 6.

It will be appreciated from the foregoing description that, according to the present invention, the shaft caisson at the shaft building spot is provided with a joint portion on the upper side thereof and the shaft is constituted by a number of shaft blocks which can be joined with each other and with the shaft caisson, preferably by the same joint construction as that of the ordinary caisson. The shaft caisson is installed in the initial stage at a predetermined spot of the submerged tunnel to be constructed so that the shaft can be built safely and efficiently after completion of or simultaneously with the construction of the tunnel, without causing time delays to the construction of the tunnel itself as in the conventional methods where the shaft has to be built independently in the water. In addition, the shaft caissons and shaft blocks are very economical since they do not require special facilities for the production, transportation and joining operation and are connectible with each other in a manner similar to the ordinary caissons.

Claims (10)

1. A method for building a shaft on a submerged tunnel comprising a train of caissons which are connected successively under water, characterized by: incorporating into said train of caissons a shaft caisson with a joint portion on the upper side thereof at a predetermined shaft building spot; stabilizing said shaft caisson if not already stable; and stacking and joining a number of shaft blocks on said shaft caisson to build a shaft of a desired height thereon.

2. A method according to claim 1, wherein said shaft caisson is stably installed on a foundation provided in a trench at the bottom of the water.

3. A method according to claim 1 or claim 2, wherein the joint portions of said shaft caisson and blocks have the same principle of joint construction, forming a recess around and on the inner side of the joined ends.

4. A method according to any one claims 1 to 3, wherein at least one of said shaft blocks is placed in position under guidance of block guides provided in the joint portion of said shaft caisson or of a lower shaft block.

5. A method according to claim 4, wherein said block guides are detachably clamped to the outer periphery of the joint portion of said shaft caisson or said lower shaft block.

6. A method according to any one of claims 1 to 5, wherein said shaft block is press-joined under water pressure to said shaft caisson or to a lower shaft block through a rubber gasket, checking uniformity in compressibility and adherence of said rubber gasket and verticality of said shaft block in a predetermined allowable range.

7. A method according to claim 6, wherein the verticality of said shaft block is corrected, where necessary, by inserting jacks between coupled joint portions.

8. A method according to claim 6 or claim 7, wherein a rigid joint is formed by sealing with a steel plate a joint gap which is stopped by said rubber gasket, connecting ends of longitudinal reinforcing iron rods in said recess, closing the opening of said recess by a steel plate, and filling said recess with mortar.

9. A method for building a shaft on a submerged tunnel, the method being substantially as hereinbefore described with reference to, and as schematically illustrated in, the accompanying drawings.

10. A shaft on a submerged tunnel, wherever built by a method in accordance with any one of claims 1 to 9.