Rock tunnel construction technology: essence and scope

TUNNEL (a. tunnel; n. Tunnel; f. tunnel, galerie, souterrain; and. tunel) - an extended underground (underwater) structure for transport purposes, laying engineering communications etc. By purpose, tunnels are divided into transport (see), pedestrian (see), hydraulic (see), utility (sewer, cable, collector, for heat and gas supply, etc.), mining (for removing rock and ore, ventilation , drainage) and special (defense purposes, for carrying out scientific research). Tunnels differ in length (from several tens of meters to several tens of kilometers), shape and size. cross section, depth (from several meters to several kilometers), structures, construction method, operating conditions, etc. (see Road tunnel, Railway tunnel, Underwater tunnel, Metropolitan,).

Tunnels began to be built in ancient times. In 2180 BC in Babylon under the river. Euphrates, a pedestrian tunnel 920 m long was built. In 700 BC. tunnels for water supply 1600 m long were built on the island of Samos in the Aegean Sea. From the end of the 17th century, the construction of shipping tunnels began, in the middle of the 19th century - railway, and at the beginning of the 20th century - road tunnels; the first underground was put into operation in London in 1863. During 1900-80, about 1 million km of tunnels were built in the world for various purposes; of the total volume, approximately 60% are hydraulic and utility tunnels and 40% are transport. During this period, the rate of tunneling increased by an average of 90 times, and from 1980 to 1987 - doubled. According to forecasts, by the year 2000, about 1 million km of tunnels will have to be built, and in the future, the volume of tunnel construction will double every 10 years.

With the development of tunneling technology, the length and cross-sectional dimensions of tunnels are increasing. In 1987, there were about 30 tunnels in the world with a length of more than 10 km; two- and three-tier transport tunnels with a cross-sectional area of ​​​​120-150 m 2 and more are becoming widespread. For example, in the city of Seattle (), a large two-tier tunnel with an outer diameter of 24.4 m was built, which accommodates two carriageways in different levels, compartment for cyclists and pedestrians, as well as ventilation ducts(Fig. 1).

Significant costs for the construction of tunnels (the cost of building 1 km of transport tunnels is 10-30 million rubles) are paid off by improving transport links, solving energy problems, streamlining urban economy systems, transforming and protecting the environment.

More than 50 km of hydrotechnical and utility tunnels, tens of kilometers of subway tunnels, mining tunnels, etc. are put into operation annually in the CCCP. The scale of tunnel construction is also significant abroad. The construction of underwater tunnels under the English Channel with a length of about 50 km has begun (the project cost is 2.3 billion pounds sterling). It is planned to create large underwater tunnels under the Bosphorus (12 km), Gibraltar (50 km), under the Gulf of Bothnia (22 km), etc. four basic railway tunnels in the Alps with a length of 49 to 60 km (table).

The purpose, location of the tunnels, its length and depth, outline in plan and profile, the shape and dimensions of the cross section are determined by topographic, climatic and engineering-geological conditions, the method of construction, as well as economic and environmental considerations.

For sound design and construction of tunnels, engineering surveys and studies are carried out, in which, along with traditional methods(drilling wells, driving exploratory workings) use geophysical exploration, gravimetric and emanation surveys, and for large tunnels - space aerial photography with high resolution. The cost of production of engineering and geological surveys and research is up to 3-5% of the cost of construction.

The construction of tunnels, depending on their location, depth and engineering-geological conditions, is carried out by mountain, shield or open ways; in some cases, the method of punching, lowering sections and special methods of work are used (see Underground construction).

For loading and transporting rock mass, powerful continuous rock loading machines (technical capacity up to 360 m 3 / h), tunnel excavators with buckets with a capacity of up to 2-3 m 3, heavy dumpers and self-propelled cars (capacity up to 10 m 3 and more) are used on pneumowheel and rail running, conveyor and pipeline transport. For temporary fastening of tunnel workings, arched, anchor (see) and spray-concrete contour lining are used. In disturbed and weakly stable rocks, leading support is effective in the form of screens made of pipes with a diameter of 200-300 mm installed in wells drilled along the contour of a future working, or concrete vaults, arranged by concreting a leading contour gap 12-15 cm wide. carried out with a continuous or stepped slaughter with the construction of a permanent lining in a mobile formwork (see). The concrete mixture is fed into the tunnels in truck mixers and placed behind the formwork by concrete pumps or pneumatic blowers. Special concrete trains have been created, including wagons with hoppers for cement and aggregates, platforms with concrete mixers, belt conveyors, etc. The operation of the installations is controlled by a computer. In some rocks with damped creep, the so-called. a new Austrian method of driving with the development, first of all, of the peripheral part of the excavation and the rapid fixing of its contour with a flexible shell of sprayed concrete and anchors. After stabilization of the rock mass, the central part of the working is developed and a lining is erected from sprayed concrete or monolithic concrete.

The shield method of work is used mainly in soft and weak rocks. For penetration into soft rocks mechanized shields with working bodies of continuous (rotary, planetary) or selective (milling, excavator) action, etc. . In non-cohesive soils of natural moisture, mechanized shields with horizontal dissecting shelves and jaw loaders are used, and in weak water-saturated soils (Fig. 2) - shields with bottom-hole loading chambers filled under pressure compressed air, water or clay solution (bentonite suspension); shields with soil and sludge weights have also been created.

For the normal functioning of transport and collector tunnels, they are equipped with operational ventilation systems (see Tunnel ventilation), lighting, drainage, and in transport tunnels, means of extinguishing fires and preventing their occurrence, as well as devices that contribute to traffic safety, are provided. Vehicle. The cost of operational equipment of transport tunnels is up to 30% of the cost of their construction.

Progress in the field of tunneling makes it necessary to increase the pace, reduce labor intensity and cost of construction. To do this, it is necessary to ensure: a reliable forecast of engineering and geological conditions along the tunnel route, standardization and unification of the shapes and sizes of the cross section of tunnels for various purposes, as well as tunnel structures; creation of industrial and economical linings and supports using traditional and new construction materials; development and implementation of automated tunnel design systems; improvement of tunnel construction technology based on complex mechanization and robotization of all mining operations, etc.

Tunnel linings are most often concreted in parallel with tunneling. In this case, the speed of erection of the lining is approximately equal to the speed of tunneling.

Parallel driving and concrete works reduces general term tunnel construction, but small sizes cross-section of the tunnel causes significant difficulties and inconveniences, especially when transporting rock from the face to the portals and transporting concrete mix and other materials from the portals to the face. For this reason, in tunnels of small cross-sectional area with single-track traffic, built in solid rocks, the lining is erected after the tunneling of the entire tunnel or its section between intermediate additional faces is completed.

The tunnel lining is concreted either continuously over the entire cross section of the working, or in a certain sequence along separate parts contour. In the latter case, two solutions are possible: first, the tunnel tray is concreted, or vice versa, the vault and walls.

The vaults of the tunnels are concreted simultaneously from two sides - from the heels to the castle in radial layers. The castle is concreted in inclined layers along the vault, and the formwork is laid as the concrete is poured in short sections from round to round. Lock working seams are made radial.

Concrete mixture for lining tunnels is usually prepared outside the tunnel in a concrete plant located near the portal. In short tunnels at the portal, a concrete pump (or pneumatic blower) is installed, which supplies the concrete mixture through the concrete conduit directly behind the formwork.

With a long tunnel, the concrete mixture can be delivered from the portal in trolleys 9 to the pneumatic blower 5, which delivers the mixture beyond the formwork I-IV.

Due to the fact that the mixture separates along the way, it is preferable to prepare it in the tunnel itself, if its dimensions allow. In this case, a concrete train is located in the tunnel, consisting of a concrete pump or pneumatic blower, a concrete mixer and a mobile conveyor. Aggregates and cement, usually already measured in required quantities, are brought to the concrete mixer in trolleys. The use of a mobile concrete train makes it possible to use a short length concrete pipeline when concreting the tunnel lining and simplify the concreting process.

For the formwork, the concrete mixture is fed from the end or through hatches 6 (see Formwork classification - Rolling formwork) in the formwork using a concrete pump or pneumatic blower. In the side walls of the tunnel and the tray, the concrete mixture can also be fed by tipping trolleys using distribution chutes.

The concrete mixture is compacted layer by layer with deep vibrators through the windows provided in each formwork section, or with external vibrators attached to the formwork. After concreting is completed and the concrete reaches the required strength in one section, the section of the resilient formwork is moved to the next section and all operations are repeated.

If the walls of the tunnel lining are concreted after the construction of the vault, then before concreting the formwork with bottom surface the toe of the vault is removed and the surface is thoroughly cleaned. The walls are concreted in horizontal layers while the formwork is built up to a height not reaching the heel of the vault by 40 cm. The space between the fifth vault and the adjacent wall is filled with rigid concrete mix and compact it carefully. Previously, pipes are laid at the junction for the subsequent injection of cement mortar.

Sometimes, when concreting tunnel linings, in addition to the usual method of laying the finished concrete mixture behind the formwork, separate concreting is used, which consists in sequentially laying large aggregate into the lining, and then injecting a cement-sand mortar into it. This method is found in the construction of hydraulic tunnels, for example, in two-layer lining structures, when laying the outer layer of the lining of small thickness behind its first (inner) layer, built from precast concrete or steel shell.

Coarse aggregate (most often gravel) must be well compacted by vibrating or laying it under pressure with gravity blowers before the solution is injected into it. Then, under pressure, a solution of high mobility is injected, sufficient to fill all the smallest gaps between the grains of coarse aggregate. Injection starts from the bottom of the lining.

Separate concreting is especially effective in cases where the supply of concrete mix by a concrete pipeline into a narrow gap of the annulus is difficult even for the length of one section of the inner shell, additional processing a deep vibrator of the laid mixture is not feasible, and formwork vibrators may not provide the necessary compaction. When the solution is injected, it simultaneously fills small pores and cracks in the rock.
When erecting the outer layer of the lining by separate concreting, there is no need for subsequent injection of the solution behind the lining.

1. Manufacturing technology of prefabricated reinforced concrete structures and parts
   • General issues of precast concrete production
   • Preparation of concrete mixtures
     
   • Mortar production
   • Transportation of concrete mix
   • Rebar stock
   • formwork
   • Preparation of molds, concrete molding and hardening of products
   • Reinforcement and forming of prestressed products

Features of the construction of tunnels by mining with the construction of a prefabricated lining

Page 10 of 16

This method is used in the construction of tunnels of a circular shape in stable soils with a strength factor f ≥ l.5, allowing the opening of a working to a full section and in the presence of a reliable roof. The essence of the method lies in the fact that the working is opened at once for the entire section using the inventory support of the roof and forehead of the face, and then the prefabricated lining is mounted directly in the face. The soil is developed by jackhammers or by drilling and blasting. The installation of the prefabricated lining is carried out by a mechanical stacker, therefore, before the start of tunneling, an installation chamber is built - the initial section of the same tunnel of short length, intended for installation of the stacker.

Assembly room constructioncameras. Work begins with the cutting of the adit (1) (Fig. 1.70), passed along the axis of the tunnel, under the laying of the first - slotted ringslining. The length of this adit is taken in such a way that it extends l 2 beyond the section of the cut (to accommodate a mounting winch in it). At the cutting section, additional pickups (2) are installed, a furnel is developed and the upper adit is cut. From this adit, the calotte is opened to a length l to using a wooden fan support. Longarins (3) of the calottes and upper beams (4) of the adit are installed outside the design contour of the lining, taking into account the suspension of the mounting blocks necessary for the assembly of the slotted lining rings by winches. From the calotte, the lower part of the section is developed in the form of a transverse slot with a length l 1 equal to the width of one or two rings (5) of the lining.

Rice. 1.70 - Tunnel cutting scheme for mounting the first slotted lining rings

Before laying the slotted rings of the lining, the tray of the slots is aligned according to the template, pouring crushed stone, folding irregularities or arranging preparation from the concrete mixture. To assemble the lining rings, two winches are installed at the end of the elongated part of the adit. One winch is used to lift tubings or blocks, and the other is to pull them to the place corresponding to the position of the element in the lining ring. The first tray lining elements are laid, avoiding deviations from the design position in plan and profile of more than 10 mm. When laying tray blocks or tubings, they are wedged with wooden wedges and fastened into the walls of the working, and the voids behind them are filled with impervious soil or concrete mixture. Subsequent elements are mounted alternately on one or the other side of the chamber, fastening them together with bolts.

Installation of the lining with two winches when laying tubing above the horizontal diameter is conveniently traced using (Fig. 1.71). To install it in place, each tubing is attached to winch cables (1) thrown over blocks (3) and rollers (2) mounted on brackets. The brackets are fixed on the side ribs of the tubings of the stacked ring. The place of installation of blocks and rollers is determined by the place of installation of the tubing. So, the diagram shown in the figure corresponds to the installation of tubing No. 6.

Rice. 1.71 - Scheme of mounting tubing with winches

During the laying process, the diameters of the lining rings are measured and, if necessary, wedged individual elements rings, and also install horizontal ties in order to maintain the design shape of the ring. After laying the locking elements, aligning and straightening the first rings of the mounting chamber, the space behind the lining is filled with backfilling from solid soils or concrete mixture, the ends are caulked with wood shavings and wooden wedges and pumped over the rings cement-sand mortar. The mounted slotted lining rings in the installation chamber are kept until the solution hardens, after which the chamber is continued to be driven to the length necessary to accommodate the lining stacker.

Slotted rings can be mounted without the use of winches. To do this, use a stacker of a special design type BTU (tunnel block stacker, universal). The small-sized stacker frame (2) (Fig. 1.72) allows you to mount it in an adit (1) with a cross section of about 9 m 2 without building a special chamber. Four height-adjustable supports (3) and a lever for laying lining elements (4) provide mechanized assembly of slotted rings (5) and subsequent tunneling with a diameter of 5.5 to 7.9 m.

Rice. 1.72 - Scheme of installation of slotted rings of the lining from the adit using the BTU stacker

Tunneling. All work in the face is carried out from retractable platforms equipped with a lining stacker. The soil in the face is developed with jackhammers or by drilling and blasting, drilling the face from the stacker's platforms with electric drills or hand-held drill hammers. Fastening of the working is carried out according to the approved passport. The roof is fixed with marchevans - boards 40-50 mm thick, which in clay soils they rest with one end on the outer surface of the lining, with the other - on the soil in the face, and in rocky soils they are laid on inventory metal brackets (1) (Fig. 1.73). The brackets are bolted to the end rib of each element in the upper part of the lining ring. With the appropriate equipment of the stacker, the protective visors mounted on it are pulled out. The forehead of the face is fixed with boards (2) or metal meshes within. Boards or frames are laid behind metal pipes(3) with a diameter of 125-150 mm, which are placed horizontally at a distance h from each other (1.2-1.5 m). The retractable ends of the pipes are led into the holes arranged in the sides of the working, and are fastened with spacers to the ends of the previously laid lining ring. Additionally, the pipes are attached to the face with steel pins (5) embedded in the forehead of the face, and wooden wedges (4) are bursting on them with support boards or frames.

Rice. 1.73 - Scheme of fastening the face when driving a tunnel with a solid face with the construction of a prefabricated lining

Exploded soil is loaded into trolleys by a rock loading machine, the type of which is determined depending on the required productivity, tunnel diameter and type of tunnel transport.

The method of continuous slaughter with the construction of a prefabricated lining should be considered as the main one in the construction of distillation and station tunnels of the subway in stable soils. Most of the distillation tunnels under construction in a closed way in stable soils, they are constructed with tunneling complexes KM-14Gp or ABT-5.5. The ABT-5.5 complex is designed for the construction of tunnels in rocky soils. The cycle of work begins with drilling the bottomhole with a self-propelled high-performance hydroficated drilling carriage (1) of the BKG-2 or BUR-2B type (Fig. 1.74, a). The carriage allows drilling holes with a diameter of 42 mm and a depth of up to 2.8 m in soils with a hardness factor f ≤ 6. While the face is being drilled, the lining stacker (5), equipped with explosion protection, is rolled away from the face. The metal structure of the stacker allows a self-propelled drilling carriage to pass under it. Exploded soil is loaded into trolleys by a rock loading machine (5) of type 1-PPN-5 (Fig. 1.74, b). After loading the soil, the stacker is rolled up to the face and, using the lever (2), the next ring of the lining is being installed. The drilling carriage, rock loader, lining stacker and trolleys move on rails laid on an articulated platform (6). Sections of the platform are alternately pulled to the bottom by hydraulic cylinders of movement. At the end of the complex, a technological trolley (4) with mortar blowers for the lining and a platform (7) with a turnout are installed. The unit is serviced by a team of 6 people (driller and his assistant, two sinkers, stacker driver and supercharger). The rate of penetration in soils with a hardness factor of 7, with a drilling depth of 2.75 m, reaches 110-120 m per month.

Rice. 1.74 - Scheme of the construction of a distillation tunnel in rocky soils by the ABT-5.5 mechanized complex

In soils with a hardness coefficient of not more than 4, it is advisable to consider the possibility of replacing the drilling carriage and the rock loading machine of the unit with a combine with a 4PP-2 boom executive body.

For the construction of large-diameter tunnels (8.5-10.2 m), the KM-15Gp and KM-36Gp complexes are intended.

Tunnel - a horizontal or inclined artificial underground structure designed for transport, water passage, placement of communications or industrial enterprises.

By purpose, tunnels are divided into seven groups:

• railway
• road
• subways
• hydrotechnical
• utilities
• mining
• special

By location, tunnels are divided into:

• mountainous (laid in mountainous areas - through ridges, watersheds and individual hills);
• underwater (tunnels built under a watercourse (or under another water barrier, such as a sea strait), for the passage of vehicles and the placement of utilities);
• flat, or urban (for example, subway tunnels).

The depth of the tunnel, its length, location, cross-sectional shape depend on the purpose of the tunnel, topographic, geological and climatic conditions. The longitudinal profile of the tunnel can be one- and two-slope (with a slope in both directions from the middle of the tunnel).

Tunneling is one of the most complex types construction works. Tunneling is carried out by identical sections limited in length - stopes. The length of the section - the depth of the entry - depends on the engineering and geological conditions for laying the tunnel, the dimensions of its cross section, the main of which is the width, the method of penetration, and the lining material. When driving a tunnel in rocky and semi-rocky soils, the penetration depth, which is determined primarily by the degree of stability of the excavation soil contour, is 2-4 meters.

Tunnel works are organized according to the in-line method with their cyclic execution. The construction process of the tunnel construction is divided by type of work. The principle of organizing work by the in-line method is that the advancement of the front of work of each working zone after the front face is carried out at a constant speed. In this case, all works on the construction of the tunnel are a single construction flow, which ensures the construction of the finished tunnel at the speed of advancement of the front face. The maximum possible speed of advancement of the front of work in each working area can be different and is determined by technological capabilities.

The second principle of the organization of tunnel work is the cyclical nature of their implementation. A cycle is understood as a completed process of performing a certain amount of work, repeated at regular intervals. The duration of the cycle should be such that a whole number of cycles are completed per shift or day. This allows in the best way organize the work of shift teams of workers and increase their responsibility for the quality of work.

The mining methods described above (supported arch of the support core, opening to the full section in parts) are laborious, since the excavation of the soil and the lining are carried out in separate parts, and not on the entire section of the tunnel.

With these methods, due to the cluttering of the tunnel section with temporary fastening and the need to erect a permanent lining on a narrow front of work, the possibility of using high-performance mining equipment is limited, and penetration rates are low.

New methods of work have been developed that allow opening the tunnel section immediately to the largest possible profile with the installation of a temporary lining that does not clutter up the section, and the subsequent erection of a permanent lining on a wide front. These methods include:

a tunneling method with a flexible vault device (developed by Austrian engineers in the mid-sixties and called the New Austrian);

the method of sinking with the device of arched concrete lining (proposed by Soviet specialists);

new version of the support kernel method.

Sinking method with a flexible vault device (New Austrian method). The development of technology for the construction of a tunnel by this method proceeds from the following basic provisions.

After the excavation of a mine working, the rock in the natural massif gradually passes from the elastic state to the state of buckling and then to the unstable state. The installation of temporary support during penetration should ensure the stability of the array. In this case, the support can work as a rigid support for the surrounding massif, or as a pliable structure that allows deformation together with the massif.

Rice. 118. Comparison of lining designs made using different technologies: a - mining method; b - the new Austrian method; 1 - wooden puff; 2 - steel arch; 3 - roshpans (1, 2 and 3 make up a temporary lining located outside the permanent lining); 4 - concrete or reinforced concrete permanent lining; 5 - reverse arch; 6 - bearing rock-anchor vault; 7 - anchors (staggered); 8 - the outer layer of the sprayed concrete lining 5-15 cm thick (together with the anchors it serves as a temporary lining); nine - inner layer permanent lining of sprayed concrete or concrete 10-35 cm thick

The flexible design of the support makes it possible to use the rock mass's own bearing capacity to the maximum. At the same time, the fixing of the working should be carried out as soon as possible after the development of the rock in order to effectively use the natural stability of the rock before it becomes unstable. This is achieved by creating a pliable vault consisting of a thin shell of sprayed concrete, densely applied to the rock and reinforced (if necessary) with mesh or arches, and a layer of rocks adjacent to this shell, included in the operation of the vault by installing a system of anchors of various lengths in the rock. In such an artificially created pliable vault, the flexible shell of sprayed concrete perceives only minor bending loads, and the rock layer, fixed with anchors, takes on the main rock pressure (Fig. 118).

The temporary support erected in this way, interacting with the rock and tightly pressed against it along the entire perimeter of the working, artificially lengthens the time of maintaining the stability of the rocks until a permanent lining is erected. At the same time, the section of the tunnel is released, which makes it possible to widely use high-performance mining mechanisms, and a permanent lining can be erected at a considerable distance from the face and immediately along the entire section using mechanized formwork and concrete-laying machines.

With this method, during the sinking, it is necessary to systematically conduct control measurements of rock pressure, loads on the support and deformations of the support and the array. This makes it possible, on the basis of the measurement results, depending on the thickness of the sprayed concrete layer, the length and diameter of the anchors, to increase, if necessary, the number of anchors and the thickness of the sprayed concrete layer.

The New Austrian method can be applied in a variety of complex geotechnical environments (for example, in unstable or heaving rocks in mining tunnels, as well as for sediment-free underground tunneling).

The New Austrian method enables fast and economical construction of tunnels, since the use of flexible lining and the optimal use of the natural stability of the massif make it possible to reduce the metal consumption of temporary lining and the thickness of the permanent lining, which is calculated taking into account the perception of rock pressure by temporary flexible lining.

In favorable geological conditions, such as in rock formations, only sprayed concrete can be used, leaving a small number of anchors in the rock.

Rice. 119. Technology system tunnel construction by the new Austrian method: 1 - drilling portal unit; 2 - anchors; 3 - grid; 4 - layer of sprayed concrete; 5 - installation for applying sprayed concrete, mounted on a car; 6 - trolley with measuring instruments; 7 - mechanized formwork, 8 - permanent lining of the tunnel

Depending on the size of the cross section of the tunnel and mining and geological conditions, the face is opened to a full profile or with one or two ledges (Fig. 119). The technological process includes the following main operations (their order may vary depending on geological conditions):

drilling of holes, development and cleaning of the rock. When performing these works, it is necessary to obtain as smooth a working surface as possible to simplify sprayed concrete work. It is advisable to use combine driving, and in blasting - the method of smooth blasting;

applying a layer of sprayed concrete. This process should be carried out immediately after the development of the arch rock with a minimum time delay. Depending on the geological conditions, sprayed concrete is applied to the side and frontal surfaces of the face in several layers, with a thickness of each layer from 5 to 10 cm.

anchor installation. This operation is carried out in the immediate vicinity of the face immediately after the sprayed concrete has been applied. It is necessary to strictly observe the design location, depth and diameter of the hole; the length and slope of the anchors may vary depending on the specific geological conditions in individual areas;

carrying out control measurements and maintaining the development of temporary lining until the erection of a permanent lining structure. This work is carried out according to a program developed in advance, which determines the placement of equipment for measurement, the frequency of measurement, and information processing. The data of control measurements are used when strengthening the sprayed concrete lining or when calculating the design of a permanent lining;

construction of a permanent lining structure, taking into account the data of control measurements.

Sinking method with the device of arched-concrete lining. The technology of sinking with the use of arched-concrete lining is also based on the use of supports of limited compliance, which make it possible to realize the bearing capacity of the rock mass. The main constructive and technological principles of this technology are: the immediate erection of a metal arch support at the bottom, calculated on the partial perception of the calculated value of rock pressure during the construction period, and the replacement of the traditional plank puff with a concrete layer of minimum thickness, laid between the rock and the outer shelf of the installed arch (Fig. 120).

This support of limited pliability ensures the maintenance of the development during the construction period, first due to the deformability of the arches themselves, and later due to the creep of concrete, which damps as it hardens. During this period, the deformations of the arched-concrete lining are measured to control the correctness of the accepted design assumptions. If the deformations are insignificant or absent, then the arches can be dismantled for reuse on following areas tunnel.

The temporary arch-concrete lining erected in this way (with or without arches) is used in permanent lining, as the first layer, designed to withstand rock pressure. The thickness of the second layer of the permanent lining is determined by calculating the multilayer system for the loads of the operational period (hydrostatic pressure, residual rock pressure, seismic effects, etc.).

IN technological process this method of tunnel construction includes the following operations:

drilling of holes, development and cleaning of the rock;

installation of fastening arches, formwork installation and concrete laying behind the arches;

setting marks for measuring displacements of concrete, taking measurements and deciding whether to remove or leave arches;

concreting the inner layer of the permanent lining.

A new version of the support kernel method. This method (Fig. 121) is used in soils with a strength coefficient from 1 to 4. The technology of work is as follows. At the beginning, on both sides of the future tunnel, there are supporting workings of a round or horseshoe-shaped cross section, and the driving is carried out ahead of one working in relation to the other. After carrying out the supporting workings, the walls of the future tunnel are concreted in them. Then they pass the calot profile with the simultaneous construction of the tunnel vault from prefabricated or monolithic reinforced concrete structures ahead of them by the length of the erected walls. At the last stage, the core is developed and the reverse vault is concreted.

Rice. 120. Technological scheme of tunneling with arched concrete lining: 1 - temporary arched concrete lining; 2 - drilling portal unit; 3 - steel arches; 4 - primary concrete lining; 5 - concrete mixer with concrete pump; b - ventilation box; 7 - technological trolley with arches; 8 o - mechanized formwork; 9 - permanent concrete lining;, 10 oo - concreting lower parts wall lining; 11 - wall formwork; 12 - bulldozer

Rice. 121. Technological scheme of tunnel construction by a new version of the support core method with prefabricated monolithic lining: a - driving support tunnels or adits; b - erection of side concrete walls; in-driving of the arched part; d - development of the kernel; d - construction of the reverse arch; 1 - reference tunnels; 2 - prefabricated lining of supporting tunnels; 3 - block stacker; 4 - rock loading machine; 5 - trolley for injecting the solution behind the lining; 6 - ventilation pipe; 7 - side concrete walls; 8 - pneumatic concrete blower; 9 - electric locomotive; 10 - wall formwork; 11 - core; 12 - calotte part of the tunnel; 13 - lining of the vault from prefabricated reinforced concrete blocks; 14 - vault lining stacker; 15 - self-propelled dump car; 16 - self-propelled drilling rig; 17 - dump truck; 18 - tunnel excavator; 19 - reverse "water

The whole complex of works is carried out using high-performance equipment: shields, stackers, rock-loading machines, excavators, mechanized formwork, concrete pumps and motor vehicles. Using this technology, single-vaulted stations are being built.