GB1592672A

GB1592672A - Process and apparatus for forming structures below ground level

Info

Publication number: GB1592672A
Application number: GB3717377A
Authority: GB
Original assignee: Banyaszati Kutato Intezet
Current assignee: Banyaszati Kutato Intezet
Priority date: 1977-09-06
Filing date: 1977-09-06
Publication date: 1981-07-08
Also published as: FR2403448A1; FR2403448B1

Description

(54) PROCESS AND APPARATUS FOR FORMING STRUCTURES BELOW GROUND LEVEL (71) We, BANYASZATI KUTATÓ IN TENET of Budapest III., Mikoviny utca 3., Hungary, a body corporate organized under the laws of Hungary, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention provides a process and apparatus for forming structures below ground level. The main field of application is the completion of permanent extensive underground spaces, e.g., underground stations, city underpasses, or underground car parks.

In these cases the structure is constructed in an opening which is developed with the aid of supporting structures which are suitable for bearing the pressure of surrounding ground, and can be recovered at least in part.

The formation of extensive spaces and structures below ground level is a task that often occurs in the building practice of underground structures of cities. The building of these extensive spaces, and structures, which are much larger than the sections of line tunnels is very slow, especially when the work is done in difficult ground, e.g. one liable to caving.

If the difficult subground or the unstable surrounding rock is susceptible to large-scale deformation, the complication of the construction technology and the slowness of workmanship are particularly striking.

Namely, in the course of the excavation of the openings for purposes mentioned above significant time and construction of accessory structures are necessary for the prevention or at least the restriction of deformations. Most of the difficulties are caused by off-grade scale deformations accompanied by surface sinking on account of the rearrangement of the internal stresses of the original natural ground.

These movements may be in the order of decimetres and they endanger the safety of buildings and establishments near the surface. The buildings are not stressed for ground movements of such size and cannot bear this deformation or can be seriously damaged.

In the course of supporting the formation of openings below ground level, so-called supporting operations are used and supporting structures are built in the interior of the opening to restrict the deleterious deformations of the ground. Two main types of these supporting structures are known: the socalled provisional and the so-called permanent supporting structures. The former have an effect only while building and support the surrounding of the opening against big deformations; the latter form a permanent part of the structure built in the opening. Naturally, both structures have to bear the socalled geostatic pressure, the load of the ground above the forming or formed opening, to support the opening against collapse.

Many versions are known for forming underground structures and the building and the method of development of the necessary supporting structures. Most of them are based on the principle of driving bores side by side or above one another, the larger opening needed being formed by the gradual junction of these bores. Those parts of these bores, which form or contain the boundary surface of the scheduled large opening, can be supplied during the construction with the permanent supporting structures which will be the parts of the structure built in the opening. The internal supports of the other bores are created with the aid of provisional supporting structures.

The built-in supporting structures always have a "passive" character in the known methods of underground opening formations, so that the walls of the excavated opening are not "charged" by active forces.

This means that the built-in and more or less stressed supporting structure does not work unless it is obliged by the deformation of the surrounding ground. Therefore these supporting structures are loaded by the "loading" effect of the ground pressure and since this loading appears only for the deformation of the surrounding ground, these supporting structures cannot inhibit significant ground deformations taking place.

One of the known methods for opening formation is the so-called "German process" in which bores are completed first along the sidewalls of the proposed permanent opening, with the aid of suitable supporting structures. After this, the sidewalls of the structure are built by creating the provisional support of the bores, then the material under the intended roof or top arch is mined under the support of suitable provisional support, and the roof or top arch is formed bearing against the sidewalls formed before. The further part of the opening is formed when the sidewalls and the ceiling walling are complete, and a bottom or base arch of the structure is built in. Another opening built by this or another method can join to the sidewall is either broken out at the end or supplied with apertures in advance.The station of the Budapest underground at Moszkva-Square and some new stations of the Leningrad underground are built by this process.

Another known method is the so-called "Moscow-process". In this process three tunnels are built successively and settled side by side by the method conventional in the case of line-tunnels, the tunnels are supported by lining segments. The built-in lining segments are taken out at some places along those sides of the tunnels which face one another, and throughcuts are created between the parallel tunnels. In addition to the recent stations of the Budapest underground at Baross Square and Blaha Lujza-Squares and that part of the station at Deak-Square which belong to the so-called East-West underground line, numerous stations of the Moscow underground are built by this process.

The "Budapest process" is similar to the German process from several points of view.

In this process colonnades are formed which are supported by bottom beams and fastened by top beams instead of solid or throughcut sidewalls. In the course of building first the bottom drift and then the top drift are excavated, by placing provisional supporting structures in the place of the proposed bottom beams and top beams. The elements of the opening formed by this process are connected under the support of the provisional struts at the places of the columns of the colonnade. After this the permanent bottom beam is built in the bottom drift, the columns of the colonnade are set on it, then the top beam is formed on the top of the columns.More columned beam systems can be set side by side according to the size of the developing space when these structures are complete; the German process is used for excavating first that part of the opening, which is near the top arch, then the parts of the base arch in the support of supporting structures. Wide rooms supported by slender columns can be created with the aid of the Budapest process, so this process proved to be substantially more advantageous and aesthetically more successful for the formation of rooms for underground stations than either the German or the Moscow process.

Namely, in the latter cases the bulk of the pillars considerably restrict the room for pedestrian traffic.

The fact that the larger openings are always formed from smaller ones, for example by connecting them, is not the only common characteristic of the known methods of formation of openings for structures under ground level. The other common principle is that these small openings can be created only successively in time.

In the case of forming openings this way, only distant tunnels can be created simultaneously. Ground excavation in neighbouring tunnels can be carried out only if the complete tunnel is supplied with permanent or at least enduring supporting structures.

The formation of the opening developed by these processes is lengthy, for the reasons mentioned above, especially for the successive excavation of the single parts of the opening.

According to experience, it is also undesirable that the load rearrangement which appears on account of the disturbation of the neighbouring parts of ground, causes the "pillars" and "partitions" of the ground to be exposed to big power impulses which are often superimposed unfavourably so that the multiple of the original "primary" ground pressures may rise sometimes. For this reason very big deformations are expected in these remaining pillars and partitions. According to experience in structural engineering, extended deformations cannot be effectively impeded by conventional "passively" functioning supporting structures, at most they can be restricted in a later period of their development.

The formation of extensive openings below ground level from smaller ones is clumsy and unfavourable from another point of view as well: the mechanization of these operations is difficult or even at times impossible.

So the building operations take a long time.

It is also undesirable that not only the necessary amount of physical energy is great, but this work should be performed generally under very difficult conditions. For the reasons mentioned, the formation of extended openings of structures below ground level is not usually developed by the former methods, but the so-called subcrustal building methods are applied instead of them. However the subcrustal construction is accompanied by the well-known disadvantage that the ground layers must be disturbed over the developing room. This method is not always possiblee.g. because there are buildings on the surface above the scheduled opening--or if it is, it still causes a long and considerable disturbance in establishments on the surface or in public traffic.

For the reasons mentioned above there is a need all over the world for developing large structures under ground level by such methods, which provide that the ground layers over the opening of the structure may remain undisturbed and possibly immobile in its original state. This immobility is particularly important for supporting the state of structures and buildings on the surface against damages.

The advanced building technology of large-scale structures under ground level was actually developed all over the world in the last decades, when the constructional principles in city underground buildings changed from the subcrustal tracing to the development of deep-lined city underground networks. E.g. the Victoria line in London, and the Leningrad and Moscow underground were built during this extensive progress. In these cases the approximately round openings were formed with the aid of a shield then the rapid walling construction and finally the stress of the walling by tangential forces were executed in rings behind the sheild.

In another method, a circular segment- or ellipse-shaped arch was built, it was stressed to the surrounding ground by tangential forces in Leningrad and by radial ones in Paris.

In every known method, including those developed recently, both the excavation of the opening and its stress to the surrounding ground take place in successive worksteps. In the course of these steps the surrounding ground does not get such an "active" support which could supply the presence of the excavated opening. Hereby, more or less, the rearrangement of the ground tensions takes place in the surrounding of the opening, and internal movements also appear inevitably in a degree depending on the stability and heaviness of the ground.

The purpose of this invention is to create a process and means which can be applied for the formation of extended structures underground in a way which is more efficient than the former ones; the formation is executed without "recovering" the surface and provides the possibility and maintenance of such construction conditions which continuously guarantee the survival of the equilibrium of the original ground in the surrounding of the developing opening.

Furthermore, the purpose of this invention is to provide favourable working conditions for people working in the opening during the formation of extensive structures below ground level and to eliminate the effects which are dangerous to the surrounding of the construction.

The basis of the invention is the idea that on one hand, the effective, rapid progress in the development of the opening can be reached, and on the other hand, the tension (stress) rearrangements in the surrounding of the opening can be eliminated by constructing such supports immediately in the course of the excavation of the opening which are suitable for exerting regulatable active forces to supply the presence of the excavated ground. These supports exerting active forces can be of provisional or permanent character, namely the provisionally placed structures can be continuously changed to permanent ones during the development of the construction.

The immediate support of the walls of the opening and the supply of the excavated parts of ground by active forces makes it possible to excavate and/or to keep opened an opening of theoretically optional size and shape. Therefore, with the aid of this method, the size of the excavated opening is independent of the ground conditions, and it may depend only on the extension of the structure and the technology of the excavation and the construction.

This invention provides a process for excavating an underground cavity which is as claimed in the appended claim 1.

A further characteristic of the process is that the opening is formed by leaving the part of ground between the surface and the planned structure, in a procedure where a starting room is formed first, then one or more starting tunnels are created which follow the shape of the scheduled structure, advisably give one of its side dimensions; when the starting tunnel is complete, the opening for the structure is formed by excavating along the whole dimension of the starting tunnel proceeding transversely in comparison with the longitudinal axis of the starting tunnel.

In the case of one of the possible variations of the process the opening is excavated in several layers, interposing parting surfaces.

In this case a layer is excavated for some kind of lining construction of the structure, and the permanent lining construction is built in it. Several working levels are created in the course of the excavation and/or the provisional support of the opening or one of its layers.

Preferably, the steps of excavation material, extension of the structure, dismantling of the strut means and placement of the permanent support means are repeated until the opening forms the cavity.

Alternatively, the step of placement of the permanent support means may be achieved by progressively filling the opening with concrete to form a first solid slab, and the process comprises forming a similar second solid slab of concrete spaced above or below the first slab, building permanent columns spanning the slabs and excavating the material between the slabs and around the columns in order to provide said cavity.

The apparatus for carrying out the process is known per se and when it is used in the process of this invention, it comprises the temporary structure which is capable of being extended and dismantled and which includes said strut means for applying forces to the ground, the apparatus also including permanent support means.

Another feature of the structure may be that besides elements which are suitable to exert active forces in the vertical direction of probable movement of the supported ground it contains elements which can also exert active forces in other different directions optionally with the aid of provisional structural units displaying power.

The whole or a part of the provisional structural units, in other cases the whole or a part of the permanent structural units is made of hardenable material. Likewise, the permanent structural units or a part of them are prefabricated. The system constructed from provisional structural units contains the cap pieces placed along the surface of the opening and one or more serials of struts supporting the cap pieces.

The cap pieces or struts may be suitable for exerting active forces. The cap pieces contain tubes which work with a fluid medium or in other cases the elements bear against the wall of the opening with the aid of rollers and the cap pieces are assembled with the corresponding rollers to form a mobile, e.g. Caterpillar (Registered Trade Mark) type powered support.

At one of the possible shapes of realization the cap pieces are joined releasably and optionally suitably for force transmission, while in other cases they can be pushed forward in the direction of the face excavation. The cap pieces may have a geared surface facing the wall of the opening.

The struts contain hydraulic or pneumatic hacks. Two or more of them can be connected. The cap pieces supported by struts can be connected to form twoor morelegged frame units. The series of the cap pieces and/or the struts optionally bears up against an open or closed rack, arch or ring.

In the case of one of the possible shapes of realization, working and/or bracing means are constructed from the additional supporting elements and/or cap pieces. The supporting elements forming the working and/or bracing means are constructed as the permanent structural elements of the structure.

In the case of any shape of realization, the hardenable and/or prefabricated structural units are optionally assembled from elements, and a transmissional supporting system is composed from the structural units.

The elements of this transmissional supporting system are joined with one another so that they are adjustable and provide loading co-operation; e.g. they are supplied with wedge-like slotted joining surfaces.

It is also conceivable within the scope of this invention that the transmissional supporting system contains such parts of the structure which were prepared by methods differing from the process of this invention, or joins with such constructions.

In the case of a preferred form of realization the elements of a transmissional supporting system which are along the wall of the opening are placed in joints. Additional mechanical joints, e.g. wedges, tensioning elements, inserts, screws, etc., in other cases molecular joints, e.g. hardenable and optionally swelling fillings may be inserted in between the elements to provide their cooperation.

The process and means of the present invention have numerous advantages. The most important is the advantage in ground mechanics that such active supporting structures are built in immediately in the course of the excavation of the opening which approximately supply the presence of the excavated part of ground, therefore it eliminates the rearrangement and the movements of the tension of the surrounding ground, respectively.

Due to this effect, openings for extended underground structures can be excavated -as well with "tunnelling"-avoiding the probable ground movements which could damage the establishments on the surface.

It is also favourable that the excavation and the transport of the excavated material can be carried out by known equipments and by known methods which can be mechanized easily because such internal rooms remain vacant for the purposes of excavation, structure construction and transport which are much larger than those of the traditional methods.

It is a considerable advantage and a notable progress compared with the former methods that with the aid of the process of this invention there is a possibility for the formation of such underground rooms which are not only horizontal but may also slope.

The process is also suitable for the construction of the rooms of pedestrian escalators serving for the approach to deep-lined underground lines. With the aid of cap pieces and strut elements, respectively, which form active supports, it is easy to accommodate breaking sections having different internal height. E.g. the struts formed like hydraulic jacks--can often compensate relatively big differences of height, but it is not difficult to splice the struts, too.

Furthermore, it is favourable that a room which may be several hundred metres wide and long can also be formed with the aid of the process of this invention, and the ground excavation itself may also be executed simultaneously in a length of several hundred metres. Hereby a working range is given for more people and machines at the same time, so the construction work becomes faster.

Hence city parking garages can be built with ease by this method in densely built-up areas without significant disturbance of the foundations and the network of public works, respectively. According to the experiments up to now, the purpose of the process of this invention and the utilization of the advantages mentioned above can be realized because the provisional supporting structures can exert active forces to supply the presence of the excavated parts of ground and this fact makes it possible to form working ranges which are more extensive than ever without the danger of ground movements. At the same time the establishment of large working ranges means the fast advance of the excavation of the opening and the construction of the structure and an efficiency greater than ever.

The invention is described in detail with reference to the accompanying drawings, in which: Figure 1. is the schematic drawing of the station area of a deep-lined underground; Figure 2. is a section taken along the line II-II in Figure 1; Figure 3. is a drawing scheme of this same station at a more advanced state of the construction; Figure 4. is a section taken along the line IV-IV in Figure 3; Figure 5. is a section taken along the line V-V in Figure 3; Figure 6. is a section taken along the line VI-VI in Figure 3; Figure 7. shows the excavation of the internal room of the station area in the case of building in a permanent intermediate space-dividing floor; Figure 8. shows a possible way of distributing the transmission system of the permanent supporting structure which can be assembled from prefabricated elements;; Figure 9. shows a possible way for placing the secondary beams and waterproofing of the prefabricated transmission system; Figure 10. shows another possible way for placing the secondary beams and waterproofing; Figure 11. shows a third possible way for placing the secondary beams and waterproofing; Figure 12. shows the joining of the profile capping beams of the prefabricated transmission system to one another and to the top beams; Figure 13. shows a possible way for placing the inserting billets which are suitable for stretching in the beams of the transmission system; Figure 14. shows another possible way for placing inserts; Figure 15. shows a third possible way for placing inserts;; Figure 16. is a schematic vertical section showing the method of the connection of the parts of the opening and the method of the excavation which can be carried out simultaneously on several levels; and Figure 17. is a section taken along the XVII-XVII straight marked on Figure 16.

Figure 1 shows the initial stage a deeplined underground station in a horizontal plot. Accordingly, the interior of the station 2 which is suitable for approaching both line tunnels 1 and the tunnel of the escalator 3 serving for the approach from the surface must be established between the line tunnels 1. A preferable sequence of the construction is, if the escalator tunnel 3 is built first, because it is suitable for personal traffic, material transports and ventilation, too. The construction of the room of the station 2 begins at the throat of the escalator tunnel with the formation of the starting tunnels 4 excavated preferably in two directions. Provisional frame units shown on figure 2 are established for the provisional support of the starting tunnel 4 from cap pieces 5, socket elements 6 and struts 7. Three-legged frame units are shown in the figure as examples.

During the work of excavation the place for the cap piece 5 placed along the top arch of the opening is excavated first, and it is joined to the neighbouring cap piece 5, previously built-in. The next step is the excavation of the part of ground under that cap piece 5 which was previously and recently built-in; the work is done in the support of this element. Now the socket elements 6 are laid on the bottom of the opening, then the strut 7 is placed in between the cap piece 5 and the socket elements 6.

The strut is optionally fixed with the aid of an additional beam 8 to the complete parts of the frame unit. If it is necessary, a platform 9 can also be built in, which forms a working or simply bracing level. The strut 7 can also be formed as a single unit containing active hydraulics, but it is also possible, e.g., to place an hydraulic jack I Il-as the active part of the strut 7--on a joining form 10 placed on the lower passive part 7a of the strut.

The starting tunnel 4 can be built with the aid of this provisional support in its total length, namely the further limiting wall of the line tunnel 1. The further excavation of the opening can be carried out simultaneously as well along the face 16 which corresponds to the total width of the room of the station 2 when the starting tunnel 4 is complete. It is not important what the permanent structure is, which forms the structure built in the room of the station 2.

E.g. it is possible to build a front wall 12 simultaneously and continuously with the formation of the starting tunnel 4, and then to create permanent bottom beams 13 and top beams 14 shown on figures 6 and 7.

These bottom beams 13 and top beams 14 are provisionally supported to one another and stressed to the wall of the excavated opening with the aid of the struts 7 containing the hydraulic jacks I I, then the struts 7 are gradually changed to permanent supporting columns 15 also shown on figure 6.

Figure 3 shows that the excavation of the face 16 can be developed along the whole width of the room of the station 2, after excavating the starting tunnel 4 to left and right from the escalator tunnel 3, and optionally after building up the front wall 12. An intermediate stage of this work is shown on figure 3. Within this stage of work the step of beginning the excavation of the face 16 near the top of the top arch is shown on figure 4.

The place of the cap piece 5 is created first near the top arch, and it is fixed with the aid of a joint to that cap piece 5 of the complete three-legged frame unit which is the nearest to the face 16.

It can be seen in Figure 5, that the ground can be taken out under the cap piece which overhangs like a bracket, according to Figure 4--in the support of this element; and the socket element 6 can be placed on the platform of the opening. The socket element 6 is temporary, but it can also become a part of the permanent structure which is to be built in the opening.

The bottom beam 13 placed along the platform of the opening and the top beam 14 built along the top arch of the opening are marked in Figure 6. It can be noticed in the Figure, that the struts 7 which are more distant from the face 16 and contain the hydraulic jacks 11 can be taken out gradually while establishing a new frame unit near the face 16, secondary beams 17 and the permanent supporting columns 15 can be built in between the top beams 14 of the ceiling forming the top arch of the opening. In the case of unfavourable ground conditions the cap pieces 5 can be difficult to take out, but this time it is possible to build them permanently in the ceiling structure of the top arch.

Faces 16a and 16b can be seen in Figure 7, they are dissected in two parts according to their height. A permanent ceiling 19 which is a part of the permanent structure, is formed by intermediate parting surfaces, namely ceiling elements 18. The face of the lower level 16b follows the face of the upper level 16a under the permanent ceiling 19 preferably remaining behind it.

The "phase shift" between the faces 16a and 16b may have the order of several metres only, according to figure 7, but it is also possible that this difference is much bigger, or the structure-which is scheduled to have several levels permanentlycan be constructed separately by levels. Theoretically it is also possible that the face of the lower level 16b is advanced and the face of the upper level 16a remains behind it or in extreme case the whole lower level can be formed sooner than the upper one.

E.g. a ceiling structure which is being built along the top arch of the opening is schematically shown in Figure 8. The temporary ceiling elements 20, which look like cap pieces, are illustrated on the upper third of the Figure: they serve for temporary supporting purposes during the excavation of the opening and are supported by struts 21 on the same way as it was shown on the preceding Figures.

The ceiling structure which is a part of the permanent structure and forms a transmission supporting system can be seen on the further parts of Figure 8. Its parts are permanent ceiling elements 23 supported by struts 22. The permanent ceiling elements 23 are placed either in the same orientation as the provisional ones 20 or e.g. transversely to them, as in Figure 8. It is also expedient to build the permanent ceiling elements 23 in offset rows.

Secondary beams 24 supporting the permanent ceiling elements 23, top beams 24 and supporting columns 26 form a further part of the transmission supporting system.

The simplest realization of placing the secondary beams 24 on the top beams 25 is shown on figures 9 and 10. The adjustable connection of the front surfaces of the secondary beams 24a facing onto the top beams 25 serving for the joining is preferable. It is also possible to stress the secondary beam 24 together from beam elements 24b and 24c e.g. with the aid of the stressing element 27. This example can be seen in Figure 11.

In most cases it is necessary to supply the ceiling structure with waterproofing. A possible way of waterproofing is shown in Figure 9 where the waterproofing sheet 28 lies under the top beams 25 and the permanent ceiling elements 25 and it is fixed automatically by the secondary beams 24a joining adjustably to the top beams 25.

It is a little more complicated case, when the waterproofing sheet 29 must be placed under the secondary beams 24a as it is shown on figure 10, because in this case it is necessary to take care of the fixation of the waterproofing sheet 29 with the aid of fixing structures 30. It is still more complicated when the secondary beams 24 are constructed from beam elements 24b and 24c in a way according to figure 11. I.e. in this case the waterproofing 31 and 32 should be placed at the joining points or along the joining edges of the beam elements, respectively, and at the joints of the beam elements 24b to the top beams 25. Special additional operations are to be done for fixing these caulkings.

As it is shown in Figure 12, the permanent ceiling elements 23 can be preferably joined to one another and to the top beams 25 if these elements are formed to have special cross-sections. E.g. the permanent ceiling elements 23 can be supplied with slots 33 and tongues 34 so that the neighbouring permanent ceiling elements 23 can be joined adjustably with them. The top beams 25 can be supplied likewise with slots 35 and tongues 36 so that the permanent ceiling elements can join to one another as well as to the top beams 25.

Examples are shown in Figures 13, 14 and 15 for the stressing of the secondary beams 24a and 24b between the top beams 25 with the aid of inserts elements 37, 38 and 39 having different shapes. E.g. Figure 13 shows the simplest case of placing the insert element 37 with a seam-filling purpose in between the secondary beam 24a and the top beam 25. It is practical if the secondary beam is shorter than the distance between the top beams 25.

The total extension of the beam elements 24 is shorter than the distance between the top beams 25 in Figure 14, too, and accordingly the beam elements 24 are stressed in between the top beams 25 with the aid of the wedge-shaped insert element 38. A larger insert element 39 is placed in between the beam elements 24b which are between the top beams 25, the insert element can provide the immobility of the beam elements 24b optionally cooperating with the stressing element 27-as can be seen in Figure 15.

In both Figures 14 and 15, the insert elements 38 and 39, respectively, may be fixed to the beam elements 24b with the aid of additional binding elements 40. The additional binding elements 41 can be placed likewise along the joining surfaces onto the top beams.

Another example is shown for the creation of the hall of an underground station in Figure 16. In this case the supporting ceiling is made of monolithic concrete. The first step of the method of the work is the excavation of the part of an opening of the lower supporting platform ceiling Hydraulic jacks 43 and temporary cap pieces at the head 44 supported by the hydraulic jacks 43 are applied during this work as struts suitable for active power efforts in a way described above. It can be practical to place a set of cap pieces at the bottom 45 along the platform of the part of the opening. Frame units can be formed from the cap pieces at the head 44, the cap pieces at the bottom 45 and the hydraulic jacks 43 which form the struts-as was shown in figures 2, 4, 5, 6 and 7.

Lining plates 46 serving for the direct support of the arch of the opening, which can be formed as Larssen sheet piles, can be placed optionally in between the top arch of the excavated part of the opening and the cap pieces at the head 44. Theoretically it is necessary to interpose such lining plates 46 also along the platform of the part of the opening. These lining plates 46 can be recovered at the lower supporting ceiling but generally remain in the structure at the upper ceiling supporting the top arch.

The vertical part of an opening 49, the wall of which is supported by a casing 50 following tightly the advance of the drilling like a "sliding formwork" is formed with the aid of a drilling machine 48 at the desired final locations of the permanent supporting columns 47.

As can be seen in Figure 17, the cap piece at the head 4#hanging back like a brack eft is surrounded by a backing element 52 taking out the back strut of the frame units assembled from the cap pieces at the head 44, the cap pieces at the bottom 45 and the hydraulic jacks in the usual way this strut is the most distant from the face 51-then the cap piece at the bottom 45 is removed and the transportable formwork 54 is supported by the hydraulic jacks 53 at places where it is necessary.

This latter operation also serves for the limitation of the working range 55 of the part of the opening which is on the opposite side comparing with the face 51.

A formation of reinforcements or armours 56 may be necessary at the places of the permanent supporting columns 47 it can be realized with the aid of curved reinforcements in the simplest case. The space behind a transportable formwork 54 is filled with cast concrete 57. This cast concrete is subjected to the compressive force of the hy draulicjacks 53 so that the cast concrete 57 is compacted and the compressive force displays a part of the forces supplying the presence of the excavated part of ground until the concrete sets; while most of the forces supplying the presence of the excavated part of ground are displayed by the cap pieces 44 and the hydraulic jacks supporting them.

The cap pieces at the head 44 can be taken out from the backing elements 52 after the cast concrete 57 sets, so that the place becoming vacant this way can also be filled with concrete. After this a new "hold" can be excavated along the face 5 1 and it can be provisionally supported by the same method as was shown in Figures 14. The formation of the part of air opening 58 serving for the upper supporting ceiling of the structure, its temporary support and the building of the permanent supporting ceiling can be created entirely in the same way. The cast concrete 59 produced in the part of the opening 58 forms a part of the permanent supporting system as well as the cast concrete 57 produced in the lower part of the opening 42.

The permanent supporting columns 47 can be practically formed starting from the working range 60 of the upper part of the opening 58. The crust of the column 79 which is built -into the prefabricated vertical parts of the opening 49 is assembled from several adjustable tube tracts then the interior of the crust of the column 79 is filled with concrete 61.

Naturally the formation of the upper supporting ceiling simultaneously with the advance of the lower ceiling can only be realized with a phase shift such that a certain period is needed for the setting of the cast concrete 57 which forms the supporting of the lower ceiling and the concrete 61 which forms the supporting of the permanent supporting columns 47. The excavation of that part of ground which is between the supporting ceilings can be carried out after the upper and lower ceilings and the columns have set.

This work can be done practically by the mechanized excavation of the face 62. It is also possible to build in the columns which consist of the crust of the column 79 and the concrete 61 after the lining units 57 and 59 produced from cast concrete are complete. In this latter case struts which can display active forces are to be placed at the excavation made at the face 62, practically according to the position of the armour 56. These elements can be taken out after the permanent columns are complete.

The process and the means of this invention which are suitable for its realization can be adapted theoretically to whatever concrete case of building structures below ground level, but its advantages are most apparent in the case of extended or deeplined line-shaped structures which are placed deeply below ground level and can be created by tunnelling methods. It is the consequence of the invention that ground deformations are prevented by creating the walls of the opening by active forces, before the deformations could appear. Thus the force phenomena of the original ground continuum is approximately copied, namely the excavated part of ground is supplied by such forces which approximately supply its former presence.The opening of the structure can be formed according to the extension and the shape of the structure and the moving structures and machines, without regard to the ground conditions, because of the support of these forces mentioned above.

WHAT WE CLAIM IS: 1. A process for excavating an underground cavity without disturbing the ground immediately above the cavity, comprising forming an underground opening having a wall elongated in a generally horizontal direction, supporting the ground surrounding the opening by a temporary structure which is positioned adjacent the elongated wall and which has strut means which are vertically extendible and apply upwardly directed and downwardly directed forces to the ground in order to support the ground surrounding the opening, extending the structure in a direction towards the wall as excavation along the wall progresses in order that the structure. takes the place of the excavated material in supporting the ground surrounding the opening, and dismantling the strut means from the structure along the length of the latter remote from the wall as excavation continues, permanent support means being placed in position to support the ground surrounding the opening at the locations where the strut means is dismantled, the steps of excavation of material, extension of the structure, dismantling of the strut means and placement of the permanent support means being repeated.

2. A process according to claim 1, wherein the steps of excavation of material, extension of the structure, dismantling of the strut means and placement of the permanent support means are repeated until the opening forms the cavity.

3. A process according to claim 2, wherein the opening is formed to extend for a length corresponding to one horizontal dimension of the cavity, the wall being excavated to widen the opening until the latter has sufficient width to form the other horizontal dimension of the cavity.

4. A process according to claim 1, wherein the step of placement of the permanent support means is achieved by progressively filling the opening with concrete to form a first solid slab, and the process comprises forming a similar second solid slab of concrete spaced above or below the first slab, building permanent columns spanning the slabs and excavating the material between the slabs and around the columns in order to provide said cavity.

5. A process according to any preceding claim, wherein the structure comprises roof members, floor members and hydraulic jacks which constitute said strut means and which extend between the roof members and the floor members.

6. A process according to claim 5, wherein the structure is extended by the addition of a roof member extending into a

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. excavated along the face 5 1 and it can be provisionally supported by the same method as was shown in Figures 14. The formation of the part of air opening 58 serving for the upper supporting ceiling of the structure, its temporary support and the building of the permanent supporting ceiling can be created entirely in the same way. The cast concrete 59 produced in the part of the opening 58 forms a part of the permanent supporting system as well as the cast concrete 57 produced in the lower part of the opening 42. The permanent supporting columns 47 can be practically formed starting from the working range 60 of the upper part of the opening 58. The crust of the column 79 which is built -into the prefabricated vertical parts of the opening 49 is assembled from several adjustable tube tracts then the interior of the crust of the column 79 is filled with concrete 61. Naturally the formation of the upper supporting ceiling simultaneously with the advance of the lower ceiling can only be realized with a phase shift such that a certain period is needed for the setting of the cast concrete 57 which forms the supporting of the lower ceiling and the concrete 61 which forms the supporting of the permanent supporting columns 47. The excavation of that part of ground which is between the supporting ceilings can be carried out after the upper and lower ceilings and the columns have set. This work can be done practically by the mechanized excavation of the face 62. It is also possible to build in the columns which consist of the crust of the column 79 and the concrete 61 after the lining units 57 and 59 produced from cast concrete are complete. In this latter case struts which can display active forces are to be placed at the excavation made at the face 62, practically according to the position of the armour 56. These elements can be taken out after the permanent columns are complete. The process and the means of this invention which are suitable for its realization can be adapted theoretically to whatever concrete case of building structures below ground level, but its advantages are most apparent in the case of extended or deeplined line-shaped structures which are placed deeply below ground level and can be created by tunnelling methods. It is the consequence of the invention that ground deformations are prevented by creating the walls of the opening by active forces, before the deformations could appear. Thus the force phenomena of the original ground continuum is approximately copied, namely the excavated part of ground is supplied by such forces which approximately supply its former presence.The opening of the structure can be formed according to the extension and the shape of the structure and the moving structures and machines, without regard to the ground conditions, because of the support of these forces mentioned above. WHAT WE CLAIM IS:

1. A process for excavating an underground cavity without disturbing the ground immediately above the cavity, comprising forming an underground opening having a wall elongated in a generally horizontal direction, supporting the ground surrounding the opening by a temporary structure which is positioned adjacent the elongated wall and which has strut means which are vertically extendible and apply upwardly directed and downwardly directed forces to the ground in order to support the ground surrounding the opening, extending the structure in a direction towards the wall as excavation along the wall progresses in order that the structure. takes the place of the excavated material in supporting the ground surrounding the opening, and dismantling the strut means from the structure along the length of the latter remote from the wall as excavation continues, permanent support means being placed in position to support the ground surrounding the opening at the locations where the strut means is dismantled, the steps of excavation of material, extension of the structure, dismantling of the strut means and placement of the permanent support means being repeated.

recess excavated in the wall, after which the ground underneath the recess is excavated, a further floor member and a further jack then being added to the structure.

7. Apparatus when used in the process according to any of the preceding claims, comprising said temporary structure which is capable of being extended and dismantled and which includes said strut means for applying forces to the ground, the apparatus also including the permanent support means.

8. A process for excavating an underground cavity substantially as herein described with reference to and as shown in the accompanying drawings.

9. Apparatus according to claim 7, substantially as herein described with reference to and as shown in the accompanying drawings.