US 3334945 A
Description (OCR text may contain errors)
Aug. 8, 1967 J v. BARTLETT TUNNELLING MACHINE SHIELD HAVING FLUID CIRCULATING BULKHEAD AND ROTARY CUTTING HEAD Filed March 17, 1965 3 Sheets-Sheet l Iuvan-roe 1mm v. BARTLETT JWMWW ATTOENEV Aug. 8, 1967 J. v. BARTLETT TUNNELLING MACHINE SHIELD HAVING FLUID CIRCULATING BULKHEAD AND ROTARY CUTTING HEAD s Sheets-Shet 2 Filed March 17, 1965 INVENTOR Joo-m V. BARTLETT J. v. BARTLETT 3,334,945 TUNNELLING MACHINE SHIELD HAVING FLUID CIRCULATING Aug. 8, 1967 BULKHEAD AND ROTARY CUTTING HEAD 5 Sheets-Sheet 3 Filed March 17, 1965 IN'vauTo JOHN \I. BARTLETT A-r-roauev United States Patent 3,334,945 TUNNELLING MACHINE SHIELD HAVING FLUID CIRCULATING BULKHEAD AND ROTARY CUT- TING HEAD John V. Bartlett, Wimbledon, London, England, assignor to Mott, Hay & Anderson, London, England, a private company Filed Mar. 17, 1965, Ser. No. 440,391 Claims priority, application Great Britain, Mar. 21, 1964, 12,063/ 64 6 Claims. (Cl. 29933) ABSTRACT OF THE DISCLOSURE A tunnelling shield for tunnelling through water bearing gravel, including a power driven rotary digging head contained in a working chamber in front of a transverse pressure bulkhead. The digging head is driven in either direction by multiple motors whose shafts pass through the bulkhead and have pinions engaging a pin wheel on the head, and the head is supported by peripheral thrust bearings. Ducts through the bulkhead supply a liquid bentonite suspension over the pinions to pressurise the working chamber and to form a seal in the gravel, and the spoil is removed by vanes on the digging head which lift the spoil and discharge it rearwards through a duct offset from the rotary axis. The effective diameter of the digging head is approximately equal to the diameter of the shield. The bentonite suspension is separated from the spoil and returned to the working chamber.
This invention relates to methods and apparatus for tunnelling generally horizontally, or on an incline, through ground which is capable of being excavated by mechanical digging or cutting mechanisms. It is common practice to employ a tunnelling shield in the form of a hollow cylindrical drum or shell which contains or supports the digging mechanism, and which advances forwards as the ground is excavated, the tunnel lining being constructed behind the shield. Such tunnelling shields have been successfully used in a wide variety of conditions where the ground is sufliciently cohesive for the working face to require no support, for example in clays, silts, and some silty sands, and tunnelling machines have also been used in soft rocks. Where the tunnelling is in progress below water level it is also common practice to employ compressed air techniques, to prevent or reduce the tendency for water to flow into the tunnel. However, compressed air techniques in themselves cannot meet the problems encountered when the working face is not selfsupporting, for example in loose gravel, and the like, and the problem is greatly aggravated if the tunnel is below the water table.
It is an object of the present invention accordingly to provide an improved method and means for tunnelling which will facilitate operations in non-cohesive water bearing ground such as gravel where the working face is not self-supporting.
From one aspect the invention consists broadly in tunnelling equipment comprising a tunnelling shield including a transverse pressure bulkhead, a rotary digging head mounted wholly in front of said bulkhead, the rotary digging head carrying multiple digging members, the maximum effective diameter of the digging members being approximately equal to the diameter of the shield, and said digging head also carrying multiple deflector surfaces for lifting and discharging spoil rearwardly, roller thrust bearings located inside the working chamber distributed around the periphery of the digging head and acting between the tunnelling shield and the digging head to locate the digging head in radial and axial directions,
Patented Aug. 8, 1967 "ice multiple driving motors located at the rear of the bulkhead and each connected via a drive shaft passing through the bulkhead to a driving pinion at the front of the bulkhead within the working chamber, an annular pin wheel or gear ring secured to the digging head, to be engaged by said driving pinions, jacking means adapted to be engaged between the shield and a stationary anchorage, for forcing the shield forwardly in the tunnel, supply duct means through the bulkhead for delivering a liquid thixotropic suspension under pressure to the working chamber, and discharge duct means through said bulkhead, at a point spaced from the rotary axis and above the bottom thereof for discharging spoil mixed with said suspension rearwardly from said working chamber.
In some cases it will be desirable to use the invention in conjunction with the plenum process of compressed air in the tunnel. In other cases an air lock may be fitted to the rear of the shield so that the introduction of compressed air is limited to the working chamber within the shield.
According to another preferred feature of the invention the suspension is delivered through the bulkhead at points close to drive gearing for driving the digging mechanisms.
In some cases it may be found desirable also to deliver the suspension under pressure around or behind the shield.
According to another, and important preferred feature of the invention, the suspension has thixotropic properties. As a result the suspension will be relatively free-flowing, and can be pumped into the working chamber at the front of the shield, but having reached or penetrated partly into the working face it will become substantially solid, or semi-solid, or viscous, and will thus materially assist in supporting the face, or in forming in effect a pressure membrane on or in the ground, against which the pressure of the liquid suspension in the working chamber acts.
The suspension may consist of, or contain mud, and a particularly preferred material comprises bentonite. Thickening or hardening additives, such as cement, may also be added in some cases.
The invention also renders it possible to tunnel by a process in which the tunnelling shield is periodically moved forwards in front of the' tunnel lining, and new sections of the lining are erected behind the shield in direct contact with the surrounding ground and without filling or grouting, the exposed ground being permeated and coated with the mud and when necessary supported by air pressure within the tunnel.
From another aspect the invention consists in a method of tunnelling using a tunnelling shield as defined, in which a liquid thixotropic suspension is supplied under pressure from outside the tunnel to the supply duct means through the pressure bulkhead, to the working chamber, and spoil mixed with the liquid thixotropic suspension is returned from the working chamber to a point outside the tunnel, where the spoil is separated from the liquid suspension which is then returned under pressure to the working chamber.
The equipment preferably includes means for separating at least the coarser ingredients of the spoil from the material extracted from the working chamber, and for recirculating the remainder.
In one form the ducts through which the relatively clean liquid suspension is admitted to the working chamber are located in the vicinity of the gear mechanism, to maintain the mechanism in relatively spoil-free conditions.
The gear mechanism may be example be contained in one or more subsidiary gear chambers into which the suspension is delivered before passing into the working chamber proper.
As stated above the discharge duct is at an elevated level in the bulkhead. As a result of this construction it is possible, when conditions permit, to operate the shield as a conventional mechanical tunnelling shield without the liquid suspension, and to remove spoil by means of a belt conveyor or the like.
According to yet another prefer-red feature of the invention the digging mechanism comprises a rotary cutting head, which is reversible. Thus continued rotation of the cutting head in one direction may tend to rotate the main body part of the shield in the opposite direction, but reverse rotation will then tend to restore the position.
The invention may be performed in various different ways but one specific method according to the invention, and equipment for use therein, and certain modifications thereof, will now be described by way of example with reference to the accompanying drawings, in which,
FIGURE 1 is a diagrammatic sectional side elevation through a complete tunnelling apparatus in accordance with the invention, with a tunnelling shield in operation at the working face of the tunnel, I
FIGURE 2 is a sectional side elevation on an enlarged scale, through the tunnelling shield of FIGURE 1 on the line 11-11 of FIGURE 3,
FIGURE 3 is a composite end view of the shield, the left half being a rear view on the line III-III in FIGURE 2, while the right half is a front view of the shield,
FIGURE 4 is a fragmentary section on the line IV-IV in FIGURE 3, and
FIGURES 5 and 6 are respectively a sectional side elevation and a part front end view of an alternative tunnelling shield structure in accordance with the invention, FIGURE 5 being a section on the line VV in FIGURE 6.
In the example illustrated in FIGURES 14 the tunnel 10 is proceeding substantially horizontally through noncohesive ground 11 such as gravel or sand. The tunnel is lined with conventional tunnel lining segments as it proceeds and communicates with the surface through a vertical shaft 12. At the working face 13 there is a tunnelling shield comprising a hollow cylindrical drum 14 of somewhat larger diameter than the tunnel lining, with a rotary cutting head 15 mounted coaxially, or almost coaxially, therewith, having digging members 16 rigidly carried by four radial arms 17 and acting on the working face itself. The tunnel lining is normally erected in sections within the skirt 18 of the shield and the shield is moved forwards as the face is excavated by means of a series of hydraulic jacks 19 arranged around the periphery of the tunnel lining.
The tunnelling shield includes a transverse pressure bulkhead comprising a central plane bulkhead 20 with a removable access door 21, and a surrounding frustoconical wall 22 which diverges outwards towards the front edge of the shield, and is sealed thereto in a pressure tight manner, thus forming a frusto-conical working chamber 23 at the front of the shield. In this chamber is mounted the rotary cutting head which is also of generally frusto-conical overall shape, having a surrounding outer shell 24, and the four radial arms 17 at its front face, each arm supporting a series of the digging tines 16. In addition the cutting head has a number of angularly spaced vanes or deflectors 25 which act to lift the spoil as it is removed by the tines, and carry it upwards until it falls by gravity into a stationary exhaust chute 26 which projects somewhat in front of the bulkhead 20 and communicates with a discharge duct 27 passing rearwards into the tunnel.
The cutting head is driven by four angularly spaced hydraulic motors 30 mounted on the rear of the bulkhead 20 and each driving a pinion 31 mounted within the working chamber, by means of a shaft passing through a pressure seal in the bulkhead. The four pinions engage an angular pin Wheel 32 secured at the rear end of the cutting head. The head is supported approximately coaxially within the working chamber by means of bearings 33 and the rearward thrust on the cutting head is absorbed by a series of thrust bearings 34 in the form of rollers mounted on the bulkhead on radial axes, and engaging a thrust ring at the rear of the cutting head.
Each of the pinions 31 is mounted in a subsidiary gear chamber 35 (see FIGURE 4) contained within the working chamber 23, and communicating therewith, and a supply duct 36 for delivering purified mud leads through the bulkhead 22 into each of these gear chambers, so that the pinions operate in relatively clean and spoil-free conditions. The mud passes from each gear chamber into the working chamber proper.
The working chamber is maintained full of liquid mud, containing a thixotropic ingredient such as bentonite, and at a pressure sufficient to cause the mud to penetrate somewhat into the working face, where it will form in effect a compact coat or membrane against the working face, and will be supported by the pressure of the liquid behind it.
For this purpose there is provided within the tunnel a supply pump 38 for delivering purified mud at a selected constant pressure to the four delivery ducts 36 in the bulkhead. This pump receives purified mud from a cleaning plant positioned on the surface and communicating therewith via ducting 37 passing through the vertical shaft 12. The mixture of spoil and mud passing from the discharge duct 27 in the bulkhead is passed to a booster pump 39 within the tunnel, where large stones and other diflicult bodies may also be removed, and the mixture is pumped to the surface via a return duct 40 in the vertical shaft.
The cleaning plant at the surface includes screening apparatus 41 for removing at least the coarser proportions of the spoil, and may include settling tanks 42, centrifuges or other separating equipment if necessary. Means are provided at 43 for adding or removing water, and for adding further quantities of bentonite to maintain the desired physical properties, and the purified mud is then delivered by means of a further pump 44 to the supply duct. Thus the same mud is re-circulated continuously, with make-up quantities being added as necessary.
A pump 50 and low level extraction pipe 51 are provided, as shown in FIGURE 2, for emptying the working chamber occasionally as desired.
In the modified cutting head described, illustrated in FIGURES 5 and 6, the single high-level discharge duct 27 through the bulkhead of FIGURE 2 is replaced by a pair of outlet ducts 45, one on each side of the axis of the head and passing through the frusto-conical wall 46 of the bulkhead, and the head itself includes a doublesided plough-shaped deflector 47 at the end of each radial arm 48, arranged to deflect the spoil outwards into the appropriate outlet duct. Each deflector has a pair of opposed inclined plough blades 49 as seen in FIGURE 5, the blades being formed of a tough abrasion resistant slightly flexible material. This deflecting action is assisted by centrifugal force, and the outlet ducts 45 each have a tangential component of direction as illustrated, so that the rotary movement of the ploughs tends to urge the material into the mouth of the duct. Each duct 45 preferably points forwards and downwards, so that one of the ducts operates at maximum efficiency irrespective of the direction of rotation of the head.
1. Tunnelling equipment comprising a tunnelling shield including a transverse pressure bulkhead, a rotary digging head mounted wholly in front of said bulkhead, the rotary digging head carrying multiple digging members, the maximum effective diameter of the digging members being approximately equal to the diameter of the shield,
and said digging head also carrying multiple deflector surfaces for lifting and discharging spoil rearwardly, roller thrust bearings located inside the working chamber distributed around the periphery of the digging head and acting between the tunnelling shield and the digging head to locate the digging head in radial and axial directions, multiple driving motors located at the rear of the bulkhead and each connected via a drive shaft passing through the bulkhead to a driving pinion at the front of the bulkhead within the working chamber, an annular pin wheel or gear n'ng secured to the digging head, to be engaged by said driving pinion, packing means ada ted to be engaged between the shield and a stationary anchorage, for forcing the shield forwardly in the tunnel, supply duct means through the bulkhead for delivering a liquid thixotropic suspension under pressure to the working chamber, and discharge duct means through said bulkhead, at a point spaced from the rotary axis and above the bottom thereof for discharging spoil mixed with said suspension rearwardly from said working chamber.
2. Tunnelling equipment as claimed in claim 1, Wherein the forward extremities of said multiple digging members, at least at the periphery of the rotary digging head, lie approximately in the same transverse plane, as a plane containing the forward edge of the tunnelling shield, and substantially the whole of the rotary digging head is located within said working chamber surrounded by the forward part of said shield.
3. Tunnelling equipment as claimed in claim 1, wherein said supply duct means includes ducts delivering the liquid thixotropic suspension into close proximity to said driving pinions.
4. Tunnelling equipment as claimed in claim 1, including an openable access hatch through the said pressure bulkhead.
5. Tunnelling equipment as claimed in claim 1, wherein each of said multiple driving motors is a reversible hydraulic motor, whereby said rotary digging head can be driven selectively in either direction of rotation.
6. Tunnelling equipment as claimed in claim 5, wherein said discharge duct means includes two horizontally spaced discharge openings through said bulkhead and located on opposite side of a vertical centre line through the centre of said bulkhead, whereby the spoil will be discharged through one or other openings depending upon the direction of rotation of the digging head.
References Cited UNITED STATES PATENTS 360,959 4/1887 Greathead 61-85 2,941,783 6/1960 Stinson -66 X 3,260,054 7/1966 Lorenz 61-85 X 3,260,548 7/1966 Reichl 299-18 FOREIGN PATENTS 1,136,361 9/1962 Germany.
934,996 8/ 1963 Great Britain. 143,416 1961 U.S.S.R.
ERNEST R. PURSER, Primary Examiner.