US2309012A - Tunnel construction - Google Patents

Description

Jan. 1Q, 1943 R. v. PRocToR 2,309,012

TUNNEL CONSTRUCTION Filed Ot. 5, 1959 4 Sheets-Sheet l dan' 19" 1943- I LR. PRocToR- I 2,309,012v TUNNEL CONSTRUCTIONv Fired oct. 5, 1959 4 sheets-sheet 2 i i \7.s sA

INVENTOR c Robe/'fk Procfor' MQ, M l M Jan. 19, 1943. R. v. PRoCToR TUNNEL CONSTRUCTION Filed oor. '5, 1959 4 sheets-sheet s R. V. PRO'CTOR TUNNEL CONSTRUCTION Jan. 19, 1943.

Filed oct. 5, 1959 4 sheeutsl-shee i Patented Jan. 19, 1943 TUNNEL CONSTRUCTION Robert V. Proctor, Youngstown, Ohio, assignor to The Commercial Shearing and Stamping Company, Youngstown, Ohio, a corporation of Ohio Application October 5, 1939, Serial No. 298,038

(Cl. (i1- 45) 3 Claims.

This invention relates to tunnel construction and particularly to soft ground tunneling..

It is common practice to erect a steel lining in a tunnel bore through soft ground, the lining being advanced simultaneously with the excavation of the bore. The lining serves to support the earth above the bore temporarily until the concrete walls and roof of the tunnel may be poured. It is important to support the earth above the bore because of the damage to the surface improvements, if any, resulting from subsidence.

The lining construction which has been preferred heretofore for soft ground tunnels consists of curved plates or segments adapted to be assembled end to end, forming successive courses along the length of the bore, with curved beams forming ribs between the courses of segments, the segments on both sides of each rib being bolted thereto. This construction is highly satisfactory for most applications but it is the object of the present invention to improve generally thereon, particularly in respect to cost, erection time, the volume of excavation required and the necessity for lling in between the lining and the interior of the bore.

In advancing a lining for a tunnel bore composed of the bolted up segments above me-ntioned, the procedure is to excavate pilot drifts along the tops of the vertical side walls of the tunnel from which the roof arch springs. Longitudinal beams are set in the pilot drifts and connected with the portion of the lining previously erected. The face of the main bore at the end of the top heading is then Yexcavated longitudinally for a distance slightly more than the width of a completed course of liner segments. The excavation proceeds from the top center down to the spring lines and when completed, a course of liner segments is bolted to the last rib previously erected. The next rib is then installed on the wall beams and loosely bolted to the forward edge of the liner segments. While the work proceeds in the top heading as just described, the bench is cut down in the bottom heading to within 6 or 8 feet of the face of the top heading, and posts are erected on suitable footings to support the wall beams.

As the excavation proceeds downwardly from the top of the roof arch, it is the practice to carry the excavation out radially beyond the minimum absolutely required, in order to provide ample clearance for the erection of the liner segments and ribs. The only guide to the required amount of excavation radially is the edge of the rib last installed but since the width of the course is around 2 feet, the actual working point is so far from the last rib before the excavation is completed that the rib does not provide a very accurate guide for the excavation. As a result, voids remain between the interior of the bore and the exterior of the lining when the segments are nally assembled. In order to prevent surface settlement, these voids must be filled and it has been the practice to blow fine gravel through the liner segments into the voids and finally to force grout into the spaces between the gravel particles.

I have invented a novel form of lining structure for tunnelbores and a method of excavating the bore and installing the lining, which reduce to a negligible minimum the excess excavation or the voids between the lining and the interior of the bore. In a preferred embodimentthe lining structure is composed of lagging plates adapted to be laid up one on another 'between adjacent ribs with their ends in loose bearing relation to the ribs. The lagging plates are held against the ribs only by the pressure of the material surrounding the bore, the excavation being carried out radially only to the extent necessary to permit the plates to be wedged between the interior of the bore and the outer faces of the ribs. No bolts are employed and the cost of the lining and the time required for its erection are thereby reduced. Voids between the lining and the interior of the bore are practically eliminated so that it is unnecessary to provide any gravel or grout filling therefor. Other novel features and advantages of the invention will become apparent during the course of the following detailed description, referring to the accompanying drawings. In the drawings,

Fig. 1 is a vertical, central, longitudinal section through the forward end of an uncompleted tunnel bore, excavated and having a lining therein, according to the invention;

Fig. 2 is a transverse sectional view along the line II-II of Fig. l;

Fig. 3 is a partialtransverse sectional View taken valong the line IlI-III of Fig. l;

Fig. S-A' is a View similar to Fig. 3 showing how the lagging plates are installed;

Fig. 4 is a sectional View taken along the line IV-IV of'Fig. 1, showing the completed course of lagging plates in position;

Fig. 5 is a sectional view taken along the line V-V of Fig. 4;

Fig. 6 is a View similar to Fig. 4 showing the concrete walls and roof arch forming the permanent lining for the tunnel and support for the earth thereabove;

Fig. '7 is an end elevation of a lagging plate adapted for use in the construction of a lining according to the invention;

Fig. 8 is a view partly in side elevation and partly in transverse section along the line VIII- VIII of Fig. '7

Fig. 9 is a transverse section taken along the line IX-IX of Fig. 8; and

Fig. 10 is a partial elevation of the exterior of the completed lining.

Referring now in detail to the drawings, the lining of my invention comprises spaced ribs II] and lagging plates II extending therebetween. The lining is erected, in a manner which will be explained in detail shortly, in the tunnel borc I2 as the latter is excavated. The bore I2 is advanced in stages by excavating the ltop heading I3 first, leaving a bench I4 and then excavating the bottom heading I by cutting down the bench. The method which I have invented for excavating the top heading and erecting the lining therein will now be explained, assuming that the face of the top heading is at the plane indicated by the line I5 in Fig. l, that the bottom heading has been advanced to the plane indicated by the line I'I, and that the lining of the upper heading has been completed to the rib Illa.

The first step in advancing the bore is to drive pilot drifts IB forwardly of the face in the top heading, along the line of wall beams I9 on Which the ribs Ill are supported. The wall beams are carried on posts 20 resting on suitable footings 2|. It will be understood that the pilot drifts I8 are excavated the full length of a section of wall beam which may be ten or twelve feet long. The wall beams are then set to line and grade and are secured to the wall beam sections previously installed by suitable splice plates or other connections. After the pilot drifts have been advanced the length of a wall beam section and the beam sections installed as described, it is unnecessary to advance the pilot drifts further until the main bore has been advanced, by the procedure about to be described, for the full length of the wallbeam sections.

After the wall beams are in place ahead of the face of the upper heading at I6, the latter is excavated longitudinally for the full width of a complete course, i. e., 30, without support, to a new face Ita. The excavation is made starting at the top and working down but is not carried out radially beyond the outside radius of the lining previously erected. In fact, the excavation is carried out radially only to the extent indicated by the dotted line 22 in Fig. 1.

The next operation is the trimming out of a groove 23 at the proper distance from the rib Illa and of sufcient depth to receive the new rib indicated at Ib. This rib is installed on the wall beams I9 when .the groove 23 has been completed. The ribs are usually in two or more pieces to facilitate erection and are secured to the wall beam by any convenient connecting members. Fig; 3 illustrates the conditions existing at this stage of the operations.

The next stage of the operations is the trimming out of the excavation between the beams Illa and Ib to the extent necessary to permit the installation of ythe lagging plates Il.` This is done by starting at the wall beams and working upward on each side of the bore. The excavation is .trimmed out and the lagging plates installed one on the other, the bottom ones resting on the wall beams I9 as shown in Fig. 3-A. The ribs Ia and Ib form guides for the workmen, enabling them to determine very accurately how much trimming out is necessary to re ceive the lagging plates so that excessive excavation is reduced to a negligible minimum, substantially eliminating voids between the lagging and the earth surrounding the bore. 'This obviates the possibility of settlement of the surface as well as the necessity for filling voids with gravel and grout as in the previous practice.

In laying up the lagging plates as shown in Fig. 3-A, one end of each plate must be inserted sulciently beyond one of the ribs I0a, Ib, to permit the other end of the plate to clear the other rib. Thereafter, the plate is roughly centered between the two ribs with ample bearing surface on the outer flanges of each.

While the excavation of the face of the upper heading is proceeding, the rear end of the bench I4 is being cut down to advance the face I1 of -the lower heading and additional posts 20 are installed under the wall beams I9.

Since the lagging plates are laid up one on the other starting from the wall beams with the ends of the plates bearing on the outer flanges of the ribs, any voids between the plates and the earth surrounding the bore may be iilled with earth or any other material, as the plates are laid up. Such voids are easily accessible over the upper edge of the plates as the latter are installed. As shown in Fig. 3-A, the sides of the plates abut,

' the plates being wedged between the earth and the ribs.

The lagging plates II, as shown in Figs. 7 through 10, are rectangular in outline, being composed of a rectangular sheet having opposite edges bent down to form side flanges 24, the extremities of which are bent inwardly as at 25. The plate is curved between the flanges 24 and the edges of the remaining sides are dished inwardly as at 26 to provide greater rigidity. The

'1 flanges 24 are collapsed or flattened against the plate as at 21 adjacent the ends thereof. This reduces the depth of the plate at its ends where it bears on the ribs and reduces to a, minimum the amount of excavation required beyond the ribs to receive the plates.

After the lagging plates have been built up from both wall beams I9 to the top of the arched roof, as shown in Fig. 4, the excavation of the top heading is again carried forward and a new rib installed as already described. Lagging plates are then placed and the entire operation repeated, the bench being cut down at the bottom heading as the top heading advances.

At a convenient distance behind the headings the permanent concrete walls and arched roof of the tunnel indicated at 28, are poured between an inner form 29 and the completed lining indicated generally at 30. It may be desirable to install a few courses of lagging plates below the wall beams as shown at IIa in Fig. 6, to prevent inward movement of the earth between the posts 2D prior to pouring of the concrete.

While the invention is applicable briefly to cohesive, soft ground tunnels, the lagging plates I I may also be employed as poling plates in running earth where fore-poling is necessary. Lagging plates used for this purpose would not have their side channels 24 collapsed at the ends as shown at 21 nor would they have their other l sides dished in as at 26. In using the plates II as poling plates, a number of plates are driven diagonally upward into the earth ahead of the last rib installed and. then the earth beneath the poling plates is removed, a new rib installed and lagging plates positioned as disclosed herein to form the completed lining.

It will be apparent from the foregoing description that the invention is characterized by numerous advantages over lining structures and excavating methods used heretofore. In the rst place, the lining of my invention is less costly than other forms. It may be erected, furthermore, in less time which represents a further reduction in overall cost. Since no bolts are employed, the cost of this item and the time required for their installation are saved. The saving of time is most important as the earth encountered in soft ground tunneling is plastic and starts to move as soon as it is excavated. The rate and extent of movement depend on the plasticity, the available air-pressure opposing movement and the time the excavation is left unsupported. As it is never possible to use airpressure high enough to prevent any movement, it is essential to get the supporting lining in place in the shortest possible time.

A further important advantage of the construction is that special sizes and shapes of lagging plates are not necessary for installation at points where the tunnel curves, as has been necessary with previous constructions. The difference between the rib spacings on the inside and outside of any curve encountered in a tunnel design is so small that it does not reduce .the bearing area of the lagging plates on the rib ilanges below a safe value. In other words, the excess spacing of the ribs on the outside of the curve as compared to the spacing of the ribs on the inside of the curve is well within the overlap of the lagging plates on the rib flanges. To line a curved bore, therefore, the ribs on the outside are merely spread apart slightly and the courses of lagging plates likewise. On the inside of the curve, the ribs and lagging plates are crowded somewhat. This represents a great saving as compared to the previous practice of making special tapered segments which were costly to manufacture, as each differed from the others in a course, to say nothing of the inconvenience of selecting and assembling them properly in the restricted space available.

Further savings in cost result from the fact that gravel and grout filling is eliminated. The curvature or crown in the lagging plates is more than enough to conform to the curvature of the ribs and provides an arch to withstand the pressure of the surrounding earth so that a relatively thin plate will carry a considerable load. Plates 1/8" thick, for example, tested under a pressure of 2500 pounds per square foot showed no evidence of failure. The flanges of the lagging plates increase the section modulus thereof which resists forces tending to bend the plates inwardly between the ribs and the collapsing of the flanges adjacent the ends of the plates, as stated, minimizes the excavation beyond the ribs necessary to accommodate the plates.

Although I have illustrated and described but a preferred embodiment 1and practice of the invention, it will be understood that numerous changes in the construction and procedure described herein may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. A lagging plate comprising a rectangular plate having flanges on opposite edges, the extremities of said flanges being bent inwardly, said flanges being attened adjacent the other edges of the plate.

2. A lagging plate adapted to be laid loosely between adjacent ribs erected in a tunnel bore comprising `a rectangular plate having anges on opposite edges to increase the section modulus opposing forces tending to bend the plate inwardly between ribs, said flanges being iiattened against the plate adjacent the other edges thereof, whereby the ends of the plate may bear on the outside of the ribs with a minimum of excavation between ribs, the intermediate portions only of said other edges being deformed slightly out of the general surface of the plate, thereby further increasing the rigidity thereof.

3. A lagging plate comprising a rectangular plate having flanges on two opposite edges, said flanges being flattened against the plate adjacent the other two edges, the intermedi-ate portions only of said other edges being deformed slightly out of the general surface of the plate thereby increasing its rigidity.

ROBERT V. PROCTOR.

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