US 3640076 A
A method of constructing a lined tunnel comprises the steps of excavating a short length of tunnel of internal diameter greater than the external diameter of the lining, erecting within the said length of tunnel a ring of three 120 DEG lining segments, repeating the steps of excavating a short length of tunnel and erecting a lining ring within the short length, and pressing each successive ring into endwise engagement with the previously erected ring.
Description (OCR text may contain errors)
United States Patent Rees et al.
[ Feb.8, 1972  TUNNELS OR TUNNELLING  Inventors: Donald Frank Rees, Wentworth; John Baron Garnett, Alresford; Michael Alexander Richardson, Knaresborough, all of England  Assignee: William F. Rees Limited, Old Woking,
Surrey, England  Filed: June9, 1970  App]. No.: 44,809
 Foreign Application Priority Data Sept. 4, 1969 Great Britain ..43,907/69  US. Cl. ..61/42, 61/45 R  Int. Cl .1. ...E01g 5/04  Field ofSearch ..61/84, 85, 42, 43, 45 R; 299/31, 33, 11
56] References Cited UNITED STATES PATENTS 3,427,813 2/1969 Hayes ..61/85 168,146 9/1875 Dowd .L ..61/84 748,809 1/1904 Stone ..61/85 1,792,084 2/1931 Glasser 2,128,172 8/1938 Warner et a1... 3,075,591 1/1963 Pirrie et al. ..61/85 X FOREIGN PATENTS OR APPLICATIONS 964,472 8/1954 France ..61/45 R 1,141,114 3/1957 France ..61/45 R 276,496 9/1927 Great Britain ..61/45 R 531,031 12/1940 Great Britain ..61/45 R Primary Examiner-Dennis L. Taylor Attorney-Cushman, Darby & Cushman [s7] ABSTRACT A method of constructing a lined tunnel comprises the steps of excavating a short length of tunnel of internal diameter greater than the external diameter of the lining, erecting within the said length of tunnel a ring of three 120 lining segments, repeating the steps of excavating a short length of tunnel and erecting a lining ring within the short length, and pressing each successive ring into endwise engagement with the previously erected ring.
7 Claims, 12 Drawing Figures TUNNELS OR TUNNELLING The invention relates to tunnels and tunnelling and is particularly, but not exclusively, concerned with flexibly lined tunnels, especially those with a bore ofabout 4 feet or less.
In its broad form the invention provides the method of constructing a lined tunnel which comprises the steps of excavating a short length of tunnel of internal diameter greater than the external diameter of the lining, erecting within the said length of tunnel a ring of three 120 lining segments, repeating thesteps of excavating a short length of tunnel and erecting a lining ring within the short length, and pressing each successive ring into endwise engagement with the previously erected ring.
Preferably the excavation is carried out within a shield of internal diameter greater than the external diameter of the lining, and the segments are erected within the shield.
In carrying out the step of erecting a ring, a first segment may be placed on the bottom or invert ofthe shield and the other two segments may then be placed above the first at opposite ends thereof to complete the ring, the clearance between the ring and the shield due to the difference in diameter being a maximum at the top and nil at the bottom.
The first segment may be held in position during the erection of the other two by a dowel pin engaging in sockets in the segment and the shield.
When the ring is erected as above described, the method may include the additional step of centralizing the ring within the shield before effecting or completing the endwide engagement of the ring with the previously formed ring. After the shield has been advanced beyond at least the rear portion of the assembled or assembled and centralized ring, grout may be injected between the ring and the surrounding material.
Radially inward pressure may be applied around the assembled ring to effect circumferential pressure at the joints between the segments (e.g., to compress sealant material between the segment ends). This inward pressure may also centralize the ring as aforesaid and may be applied, for example. by expansion under internal fluid pressure ofa flexible annular tube between the shield and the ring. The annular tube may also serve as a temporary, or permanent, grout and water barrier.
After assembly of the segments to form a ring, the segments may be held together by an external circumferential tie.
The segments may be formed with lines or regions of weakness extending in the axial direction of the ring whereby the rings can crack at controlled locations and deform to accommodate unevenly distributed external loads. The stresses in the rings will then be mainly or wholly compressive with the advantage that the segments can be made of material such as concrete and fireclay which are strong in compression but weak in tension.
The invention includes a tunnel constructed by the above described method.
An example of the manner in which the method may be carried into effect will now be described with reference to the accompanying diagrammatic drawings in which:
FIG. 1 is a longitudinal section through a portion ofa tunnel under construction,
FIG. 2 shows halfcross sections on the lines A-A and 8-8 in FIG. 1,
FIGS. 3 to 6 are cross sections showing successive stages in the erection ofa ring of segments,
FIG. 7 is an enlarged view of the portion ringed in FIG. 6,
FIGS. 8 and 9 are longitudinal sections of the upper portion of a ring of segments and related parts, in different stages of erection,
FIGS. 10 and 11 are end and side views ofa completed ring, and
FIG. 12 is a section on the line CC in FIG. 11 through a portion ofa segment.
Referring first to FIG. 1 the method is carried out within a circular steel shield 20, fitted with mechanical or hydraulic rams 21, a thrust ring 22, and a pressure hoop 23.
The segments. three per ring. are transported within the already constructed work to the rear. i.e.. into the skirt, of the shield 24 (see also FIG. 3).
The segments are all alike and extend over I20 of are.
Segment 1' is then placed in the invert of the skirt of the shield anda temporary locating pin 25 is inserted through a preformed hole in the segment into a similar hole in the skirt of the shield. Segment ii is moved forward and its edge mated with that of i, and its other edge lifted. thus pivoting the segment until it touches the inside of the skirt near its soffit (see FIG. 4). A locking bar (not shown) temporarily holds segment ii in this position. Segment iii is similarly mated with the other edge of segment i and lifted sufficiently to allow the edges of segments ii and iii to locate with the then lowered edge ot'segment ii, thus completing the structure (see FIG. 5). i
This operation can be achieved within the skirt with three identical segments, since the skirt diameter is sufficiently larger than the outside diameter ofthe segment ring, e.g., for a 900 mm. bore segment ring of 60 mm. wall thickness, an internal shield diameter of approximately 1,060 mm. will allow the erection operation within its bore and thus the internal diameter of the skirt is not excessively larger than the external diameter of the segment ring, since the erection of the segments takes place with the invert segment lying directly on the invert of the skirt, thus taking full advantage of the skirt diameter.
The segment joints, both longitudinal and circumferential, can be coated with a suitable waterproof sealant prior to erection, e.g., bituminous based materials.
When the erection of the segment ring has been achieved, liquid or gas under pressure is forced into the circumferential pressure locking hoop 23, fabricated of a flexible. impermeable material, and which is situated in the annular void between the outside of the segment ring and the inside of the skirt and thus exerts circumferential pressure on the segments, squeezing the joints and at the same time lifting the whole ring to the approximate centerline of the shield, (see FIGS. 6 and 7) e.g.. a 50 mm. nominal bore tube of about 2 mm. wall thickness operating in an annular ring void of 25 mm. width and charged to a pressure of 7 Kg. per sq.cm. and having an area of contact with the periphery of the segment ring of approximately l.l20 sq.cm. will induce a circumferential compression load in the ring of 1,260 Kg., thus tightening the ring and sealing the longitudinal construction joints with a force of about 2] Kg. per centimeter run ofjoint for a segment ring, 900 mm. bore. 600 mm. in length. The steel locating pin 25 is now removed from the invert segment i.
The segment ring is then forced back by the rams 2] and jointed with the previously laid ring 26. The shield is also forced forward in the direction of construction, the strata being excavated at the front of the shield and transported to the tunnel entrance for disposal, via the already completed section.
The shield leaves the segment in position, which passes through a skirt ring 27, made of suitable resilient material, for example hardwood, which maintains a radial pressure on the ring during this part of the operation. The thrust pressure locking hoop 23 is now deflated or drained.
When the shield has been driven forward one ring length. cement grout 28 or other suitable filling material is forced under pressure between the segment ring and the surrounding material through the preformed locating holes of the segments, or through longitudinal holes in the skirt ring, located at the top ofthe shield.
In order to expedite progress of the work, this material may be ofa quick setting nature, for example, high alumina cement grout. This material can be used in batch quantities corresponding in volume to the void between the segment ring and the surrounding material formed by the shield cutting edge, and may be injected by means of compressed air or other suitable type of pump attached to the segment transport vehicle or transported through pipelines from a working shaft.
Alternatively, if a quick setting grout is not used, locking up the segments can be achieved using metal bands or hoops fitted to the outside of the segment ring and suitable tightened, e.g., a hoop of thin steel 30, H08. 1, 8 and 9 of about mm. width and 1 mm. in thickness and of diameter the same as that of the shield skirt, may be used. The segments are erected as before the steel hoop being previously loosely positioned on the inside of the shield skirt by means of suitable clips 31 axially coincident in position with the three grout holes 32 in the ring units. When the locking ring has been inflated the slack in the hoop is booked with a suitable tool through one of the upper grout holes and a loop pulled through the holes. A conical wedge 35 is then inserted through the loop. The wedge is driven home, thus tensioning the hoop pulling it out of the clips and. thereby locking .the ring circumferentially. The method of operation then continues as before and on setting of the grout the wedges 35 may be withdrawn, the loops cut off and the holes flushed off with a suitable compound. A rebate may be formed in the back of thesegment units to accommodate the steel hoop and be of sufficient depth to allow the hoop to be flush with the outside of the ring, thus allowing the whole to pass easily through the, shield skirt ring 27.
The three unit segment ring may be of a material .which is weak in tension (e.g., concrete) and, whilst showing the advantage of stability during erection, would require reinforcing if subjected to initiallylunequal external pressures since the ring would act as three two-pin arches, and bending stressed and thus tensile stresses will be present in the material.
In order to overcome the necessity for such reinforcing, eachsegmentis fabricated with two or more dummy joints 33, FIGS. 10, 11, and 12 which may consist of V or similarly shaped notches or rebates formed at the inner and outer faces of the segment in correspondingpositions these being positioned at approximately equal distances between the construction joints 34. The rebates are filled with suitable elastic adhesive waterproof compound to maintain watertightness.
Should tensile stresses occur in the unit after erection, due to unequal pressure of the surrounding strata, then cracking will occur at these dummy joints and small rotations will take place both at the dummy joints and at the construction joints and the segment ring will deform as a whole to equalize the external pressure thereon. The spacing of the dummy joints can be calculated such that direct stresses in the material of the segments, due to circumferential stresses and bending stresses caused by approximately uniformly distributed loading by the strata on each subsegment, are integrated to give resultant stresses within the working stress tolerances of the material, e.g., with concrete zero tensile stress, compressive stress as per the relevant Code of Practice or to other relevant specifications.
The method is also applicable where the tunnel lining is fabricated of inherently flexible material e.g., glassfiber reinforced resin or of rigid reinforced lining e.g., reinforced concrete.
The invention is not restricted to the features of the above example. For instance where ground conditions permit the shield 20 may be omitted the oversize tunnel being excavated without support, a short length at a time, and the lining rings being erected within the tunnel. Hydraulic rams are of course still provided to drive the erected rings backward.
Furthermore the dowel locking pins 25 may be omitted and it is possible to successfully erect a ring without the pins. Similarly the circumferential pressure locking hoop 23 may be omitted while still permitting successful tunnel construction.
1. A method of constructing a lined tunnel which comprises the steps of excavating a short length of tunnel within a shield of internal diameter greater than the external diameter of the lining to be erected, placing a first lining segment against the inner periphery of the shield, engaging one circumferential end of each of two further l20 lining segments at respective circumferential ends of the first segment and pivoting, in turn,
said two further segments outwards to bring the other ends of the two further segments into engagement to form a complete ring the axis of which is offset with respect to the axis of the shield, centralizing the newly erected ring within the shield. and locking the newly erected ring to the previously erected ring to prevent relative radial movement between adjacent ends of said rings, advancing the shield to a position in which a portion of the newly erected ring extends axially out of the rear end of the shield, injecting a filler material into the annular void left between the portion of the newly erected ring projecting from the shield and the surrounding material by ad vancing the shield while the ring is still supported coaxially with the shield by the shield, and then repeating the steps of excavating a shortlength of tunnel and erecting a lining ring within the shield in its advanced position.
2. The method according to claim 1 in which, in carrying out the step of erecting a ring, the first segment is placed on the bottom of the shield and the other two segments are then placed above the first at opposite circumferential ends thereof.
to complete the ring. the clearance between the ring and the shield due to the difference in diameter being a maximum at the top of the ring and nil at the bottom.
3. The method according to claim 1 in which the first segment is held in position during the erection of the other two by a dowel pin engaging in sockets in the segment and the shield.
4. The method according to claim 1 in which radially inward pressure is applied around the newly erected ring, before it is locked to the previously erected ring, to effect circumferential pressure at the joints between the segments.
5. The method according to claim 4 in which the inward pressure is applied by expansion under internal fluid pressure of a flexible annular tube between the shield and the ring.
6. The method according to claim 1 in which the segments after they have been erected to form a ring are held together by an external circumferential tie.
7. The method according to claim 1 in which the segments are formed with lines or regions of weakness extending in the axial direction of the ring whereby the rings can crack at controlled locations and deform to accommodate unevenly distributed external loads.