CN107245989A - Bear the tunnel structure and its construction technology of external water pressure in height - Google Patents

Abstract

The invention discloses a tunnel structure bearing high internal and external water pressure and its construction technology, comprising: a plurality of circular flat jacks, the outer side of the flat jacks is the surrounding rock, and the outer layer of the surrounding rock is a consolidation grouting ring; drainage The system includes longitudinal drainage grooves, circumferential drainage grooves, drainage layers and drainage holes. The longitudinal drainage grooves are set at the lowest point of the surrounding rock surface and communicate with the collection wells; the circumferential drainage grooves are set between the flat jacks; the drainage layer is located at Between the prestressed concrete lining and the consolidation grouting ring; one end of the drainage hole communicates with the circumferential drainage ditch, and the other end passes through the surrounding rock and is close to the consolidation grouting ring. In the present invention, the prestress is applied by the external prestress method to offset the tensile stress produced by the internal water pressure, and the high external water pressure borne by the lining is reduced or eliminated by consolidating the grouting, vertical and horizontal drainage systems and drainage hole systems, and reducing the stress of the lining. Small seepage flow.

Description

Tunnel structure and its construction technology under high internal and external water pressure

technical field

The invention relates to a tunnel structure bearing high internal and external water pressure and its construction technology.

Background technique

The characteristics of the pressure tunnel are: first, the section shape is mostly circular, because the main load is high internal water pressure and high external water pressure, so the stress condition of the circular section is better, and the wetted circumference of the section is the smallest; The body is excavated in the rock mass, and the original balance state of the rock mass is damaged, which may cause large deformation or collapse. Therefore, permanent lining is often used to ensure safety; third, the cave body must withstand high internal and external water pressure and surrounding rock pressure etc. Therefore, the lining of the cave body must have sufficient strength and anti-leakage function.

The main purpose of the tunnel lining is to withstand high internal water, external water pressure and other loads; prevent internal water from seeping out, endangering the safety of surrounding rock and adjacent buildings, etc. At present, the commonly used lining types include ordinary reinforced concrete, prestressed reinforced concrete, and steel plate lining. Since the use of steel bars to prevent the occurrence of concrete cracks proves to be unfeasible both in theory and in practice, so bonded or unbonded prestressed reinforced concrete is often used to line tunnels at home and abroad. The above-mentioned prestressed concrete requires a lot of prestressed High-strength, low-relaxation steel and anchors, as well as quite a lot of ordinary steel bars, the construction is troublesome. At the same time, due to the loss of prestress along the way, the distribution of circumferential precompression stress is uneven, and the stress state is not good. Therefore, it is an economical and reasonable choice to choose the external prestressing method and use the ring-shaped flat jack to apply the prestressing, which not only saves a lot of high-strength steel, but also distributes the stress evenly.

Generally speaking, the existence of groundwater is always an unfavorable factor. In addition to deteriorating the geological conditions, it will also generate a large external water pressure outside the tunnel lining, and the external water pressure is one of the main reasons for the damage of the lining. one. The tunnel in the rock mass must be compatible with the burial characteristics, structure and water chemical characteristics of the rock mass, and the fissure degree, water permeability of the rock mass, and the solubility of the groundwater to the rock must be investigated in detail, especially when there are faults and cracks. Weak fillings that are easily eroded by water and washed away should not be ignored. It should be noted that the most dangerous situations are aquifers composed of fine sand and silt. In this case, any disturbance of the natural balance, rapid pumping or backwatering may cause shifting of quicksand, causing the upper strata to slide or collapse.

The permeable and cracked rock mass often makes rainwater and water in mountain streams, snow and lakes above the tunnel elevation flow to the deep, thus causing a large external water pressure on the outside of the tunnel lining. In the original rock mass without groundwater, the water in the high-pressure tunnel may slowly seep out of the tunnel over a long period of time and fill the pores of the surrounding rock mass. When the tunnel is later emptied, the lining will be destroyed under the action of the external water pressure close to the internal water pressure strength. Some rock masses contain layers of clay, which may be primary or metamorphic. This layered rock mass has the potential to slide along layers of clay or other rock formations, where the presence of groundwater is a particularly dangerous factor. In this case, the rock formation will undergo a large displacement, and the rock pressure will increase sharply immediately, and the mica shale wetted by water is also in this danger.

The effective way to eliminate the external water pressure is to adopt the engineering measures of "blocking" first and then "draining". The so-called "blocking" is to consolidate and grout the surrounding rock of the lining, drill holes at a certain depth into the surrounding rock, and perform cement grouting under pressure , Mortar filling joints, fissure seepage channels, so that the integrity of the surrounding rock is improved, while improving its impermeability and firmness, in order to achieve the purpose of forming a strong bearing ring and a dense anti-seepage ring. However, consolidation grouting cannot completely cut off the seepage. In order to collect and drain the infiltrated water, a drainage system needs to be installed behind the lining. The so-called "drainage" is to set drainage holes behind the lining layer, and penetrate to a certain depth in the surrounding rock, but do not pass through the consolidation grouting layer, so as to discharge the seepage water outside the lining out of the tunnel, so as to further reduce the water pressure outside the lining. Under the combined action of the consolidated grouting layer and system drainage, the external water pressure of the lining is reduced to the allowable value.

Most of the built tunnels are designed and constructed based on the principle of plugging, and the idea of groundwater anti-seepage combined with plugging and drainage. It is believed that the consolidation grouting treatment measures should be taken first to form a good anti-seepage grouting circle, which can control the high groundwater pressure in the grouting circle. The surrounding rock of the grouting circle becomes the main structure that bears the external water pressure. Then, the top and side walls of the tunnel are drilled to a certain depth into the surrounding rock to strengthen the drainage effect and reduce the external water pressure. For the design of the drainage system of pressure tunnels, most of them use existing exploratory tunnels, construction branch tunnels or drainage tunnels specially designed for drainage purposes according to factors such as surrounding rock geological structure, and then arrange horizontal and vertical slopes in the tunnels. drainage hole. For the support of the drainage tunnel, only shotcrete is used for supporting the surrounding rocks of types II and III, and the supporting structure of shotcrete is used for the surrounding rocks of types IV and the broken zone.

The effective engineering measure to eliminate or reduce the external water pressure is the principle of combining plugging and drainage. Plugging means to consolidate and grout the surrounding rock of the lining to reduce the permeability of the surrounding rock. There are two kinds of grouting time: one is to carry out after the lining is completed, the quality is guaranteed, but it may cause blockage to the drainage holes; The construction is troublesome and difficult to popularize. The design of the drainage system of the pressure tunnel is mainly to set up drainage holes, and arrange drainage holes in the holes. The problem is the layout of drainage tunnels, of course, using construction branch tunnels or geological exploration tunnels, or excavating horizontal tunnels for water supply and drainage, which are more or less perpendicular to the tunnel axis. Because larger drainage tunnels arranged parallel to the pressure tunnel are dangerous. In short, the water outlet of the drainage system of the pressure tunnel should not be in the cave at most, because it is afraid that the internal water will run out. However, there are also studies where the outlet of the drainage pipe is arranged in the cave. At this time, the outlet is equipped with a pressure valve. When the pressure of the external water is greater than the pressure of the internal water, the valve is opened and the external water is discharged into the cave; when the pressure of the external water is lower than the pressure of the internal water , the valve is closed to prevent the inner water from flowing out. Because the pressure valve is often out of control and cannot eliminate the external water pressure, it has not been widely used.

Contents of the invention

The object of the present invention is to provide a tunnel structure that reduces or eliminates the pressure of high external water pressure on the lining by first consolidating the grouting, and then setting the vertical and horizontal drainage systems and drainage hole systems.

The purpose of the present invention is to also provide a prestressing method of external prestressing, which can not only save the prestressed steel and anchorage, but also save a large amount of ordinary steel bars by properly proposing the prestressing degree in consideration of the characteristics of the compressive strength of concrete. The construction technology of the tunnel structure under the pressure of high external water pressure.

In order to achieve the above object, the present invention provides the following technical solutions:

A tunnel structure bearing high internal and external water pressure according to the present invention, comprising:

A number of round flat jacks, the outer side of the flat jacks is the surrounding rock, and the outer layer of the surrounding rock is the consolidation grouting circle,

The prestressed concrete lining arranged on the inner side of the flat jack,

Drainage system, including longitudinal drainage groove, circular drainage groove, drainage layer and drainage holes, the longitudinal drainage groove is set at the lowest point of the surrounding rock surface, and communicates with the water collection well; the circular drainage groove is set between the flat jacks, and the bottom The end is connected with the longitudinal drainage groove; the drainage layer is located between the prestressed concrete lining and the consolidation grouting circle; one end of the drainage hole is connected with the circumferential drainage ditch, and the other end passes through the surrounding rock and is close to the consolidation grouting circle .

The interior of the drainage hole is provided with a filter drainage flower tube, and one end of the filter drainage flower tube with a back cover is inserted into the drainage hole. The filter drainage flower tube includes a tube body, and several layers of filter drainage non-woven fabrics are distributed on the tube body.

The cross section of the circumferential drain is rectangular or arched.

The number of flat jacks between two adjacent circumferential drains is one, two or three.

A construction technique for a tunnel structure subjected to high internal and external water pressure of the present invention comprises the following steps:

1) After the excavation of the tunnel section is completed, the consolidation grouting treatment shall be carried out first; then the stakeout shall be carried out to determine the installation positions of several flat jacks, the longitudinal drainage grooves, the circumferential drainage grooves and the drainage holes;

After the excavation of the tunnel section is completed, holes are drilled on the inner wall of the tunnel. The depth of the hole is about half the diameter of the tunnel. The row spacing along the tunnel axis and the spacing of each row of holes in the circumferential direction are related to factors such as the grouting pressure and the diffusion radius of the cement slurry in the grouting hole. , to be determined by field tests. Insert a grouting pipe into the drilled hole, and install an air pressure grout stopper on the grouting pipe to improve the grouting effect. When grouting, firstly carry out deep grouting. The air pressure grout stopper is located at the depth of 1/2 hole, and the grouting pressure is about 2 times Internal water pressure; open the valve of the air pressure grout stopper, let off the air, and pull out the grouting pipe, so that the air pressure grout stopper is about 1/3 of the hole depth from the hole, and perform shallow grouting after inflating the grout stopper , The grouting pressure is slightly lower. In view of the general occurrence of loose cracks in the cave wall, shallow grouting and deep grouting are designed to improve the bearing capacity and impermeability of the grouting layer;

2) Drill drainage holes in the circular drainage ditch and install the filter drainage flower pipe. After completion, the hole is blocked with a wooden plug to prevent debris from falling into the hole; finally, lay it on the surrounding rock side of the circular drainage ditch non-woven fabric.

3) Excavate the longitudinal drainage groove at the bottom of the excavation section of the tunnel and line it with reinforced concrete. Except for the intersection with the circumferential drainage groove, the rest of the parts are sealed with thin steel plates to prevent concrete from falling into the groove;

4) Install flat jacks longitudinally and evenly along the centerline of the tunnel, and seal the gaps on both sides with cement mortar; and embed grouting pipes and exhaust pipes for backfill grouting behind the flat jacks;

5) After unplugging the wooden plug on the drain hole, install the steel plate member that surrounds the upper part of the drain, and fix the member to the anchor screw with a thin lead wire. The gap between the component and the contact portion of the circular flat jacks on both sides is smoothed with cement mortar to form a smooth curved surface. It should be pointed out that the cross connection between longitudinal and circumferential drainage grooves and ditches should be unobstructed;

6) Pouring the tunnel lining concrete After the lining concrete reaches the design strength, the external prestress can be applied.

In the above technical solution, the present invention provides a tunnel structure that withstands high internal and external water pressure. By adopting external prestressing, prestressed steel and anchorage can be saved; increasing the prestressing degree can save a lot of ordinary steel bars. The measures of blocking first and draining later can eliminate the external water pressure on the lining and reduce the leakage flow.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings that are required in the embodiments. Obviously, the accompanying drawings in the following description are only described in the present invention For some embodiments of the present invention, those skilled in the art can also obtain other drawings according to these drawings.

Fig. 1 is a schematic longitudinal section view of a tunnel structure subjected to high internal and external water pressure provided by an embodiment of the present invention;

Fig. 2 is a schematic cross-sectional view of a tunnel structure subjected to high internal and external water pressure provided by an embodiment of the present invention;

Fig. 3 is a schematic diagram of the structure of the filter drainage floral tube in Fig. 1;

Fig. 4 is one of the enlarged structural diagrams of part A in Fig. 1;

Fig. 5 is one of the enlarged schematic diagrams of part A in Fig. 1;

Fig. 6 is a schematic diagram of an enlarged structure of part B in Fig. 1;

Fig. 7 is a schematic diagram of a grouting structure of a consolidated grouting circle in the construction process of a tunnel structure subjected to high internal and external water pressure provided by an embodiment of the present invention.

Explanation of reference signs:

1. Flat jack; 2. Surrounding rock; 3. Consolidation grouting area; 4. Prestressed concrete lining; 5. Longitudinal drainage groove; 6. Circular drainage ditch; 7. Drainage layer; 8. Drain hole; 10. Filtration non-woven fabric; 11. Grouting pipe; 12. Air pressure grout stopper; 13. Back cover; 14. Deep grouting area; 15. Drain hole area; 16. Shallow grouting area.

detailed description

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings.

See Figure 1-6;

A tunnel structure bearing high internal and external water pressure according to the present invention, comprising:

A number of round flat jacks 1, the outer side of the flat jacks 1 is the surrounding rock 2, and the outer layer of the surrounding rock 2 is the consolidation grouting circle 3,

The prestressed concrete lining 4 arranged on the inner side of the flat jack 1,

The drainage system includes a longitudinal drainage groove 5, a circumferential drainage groove 6, a drainage layer 7 and a drainage hole 8. The longitudinal drainage groove 5 is set at the lowest point on the surface of the surrounding rock 2 and communicates with a water collection well (not shown). The pump drains the water in the sump well to the outside of the hole; the circular drainage ditch 6 is opened between the flat jacks 1, and the bottom end communicates with the longitudinal drainage groove 5; the drainage layer 6 is arranged between the flat jacks 1 and the shallow Between layers of grouting areas 15; one end of the drainage hole 7 communicates with the circumferential drainage ditch 6, and the other end passes through the surrounding rock 2 and is close to the consolidation grouting circle 3.

The interior of the drainage hole 8 is provided with a filter drainage flower tube, and one end of the filter drainage flower tube with a back cover 13 is inserted into the drainage hole 8. The filter drainage flower tube includes a tube body 9, and several layers of filter non-woven fabrics are distributed on the tube body 9. Object 10.

The cross section of the circumferential drain 6 is rectangular or arched.

The number of flat jacks 1 between two adjacent circumferential drains 6 is one, two or three.

A construction technique for a tunnel structure subjected to high internal and external water pressure of the present invention comprises the following steps:

1) After the excavation of the tunnel section is completed, the consolidation grouting treatment shall be carried out first; then the setting out shall determine the installation positions of several flat jacks 1, the positions of the longitudinal drainage groove 5, the circumferential drainage groove 6 and the drainage hole 8;

After the excavation of the tunnel section is completed, and the hole is drilled, the depth of the hole is about half the diameter of the tunnel. Determined by field tests. Insert the grouting pipe 11 (as shown in Figure 7) in the drilled hole, the air pressure grout stopper 12 is set on the grouting pipe 11, and the rear end of the air pressure grout stopper 12 on the grouting pipe 11 is the deep grouting area 14, One end of the drainage hole area 15 close to the surrounding rock 2, and the shallow grouting area 16 is between the drainage hole area 15 and the air pressure grout stopper 12 to improve the grouting effect. The plug 12 is located at the depth of 1/2 hole, and the grouting pressure is about 2 times the internal water pressure; open the valve of the air pressure grout stop plug 12, release the air, and pull out the grouting pipe 11 to make the air pressure grout stop plug 12 away from the hole When the mouth is about 1/3 of the hole depth, perform shallow grouting after filling the grout, and the grouting pressure is slightly lower. In view of the general occurrence of loose cracks in the cave wall, shallow grouting and deep grouting are designed to improve the bearing capacity and impermeability of the grouting layer;

2) Drill the drainage hole 8 in the circular drainage ditch 6 and install the filter drainage flower pipe. After completion, the hole is blocked with a wooden plug to prevent debris from falling into the hole; finally, pave the surrounding rock side of the circular drainage ditch Several layers of non-woven fabric are placed.

3) Excavate the longitudinal drainage groove 5 at the bottom of the tunnel excavation section and line it with reinforced concrete. Except for the intersection with the circumferential drainage groove 6, the rest of the parts are sealed with thin steel plates to prevent concrete from falling into the groove Inside;

4) Install the flat jack 1 longitudinally and evenly along the center line of the tunnel, and seal the gaps on both sides with cement mortar; and bury the grouting pipe and exhaust pipe for backfill grouting behind the flat jack 1;

5) After unplugging the wooden plug on the drainage hole 8, install the steel plate member on the upper part of the ring to the drainage ditch 6, and fix the member on the anchor screw with a thin lead wire. The gap between the component and the contact portion of the flat jacks 1 on both sides is smoothed with cement mortar to form a smooth curved surface. It should be pointed out that the cross-connection of the longitudinal drainage groove 5 and the circumferential drainage ditch 6 should be unobstructed;

6) Pouring the tunnel lining concrete After the lining concrete reaches the design strength, the external prestress can be applied.

The huge tensile stress in the lining concrete of the present invention is mainly offset by the precompression stress in the lining concrete produced by the external prestressing method. As for the pressure tunnel designed with high external water pressure control lining concrete, it is advisable to adopt measures combining consolidation grouting and setting up an effective drainage system.

The thickness of the lining concrete of the tunnel (excluding the over-excavation part of the surrounding rock) can be determined through comprehensive analysis and calculation according to the requirements of strength, impermeability and structure, combined with the construction method of applying external prestress by the ring-shaped flat jack 1, and is the diameter of the tunnel. About 1/10. If the lining cracks, resulting in internal water seepage, which will endanger the stability of the surrounding rock or the safety of adjacent buildings, it should be designed according to the crack resistance, and the prestressing degree can be increased appropriately. The lining does not crack, and naturally there will be no leakage of internal water. As the external prestressing method is adopted, no additional expenditure is required, and the precompression stress value required by the design can be obtained only by increasing the grouting pressure.

The cross-sectional shape of the circumferential drainage ditch 6 can be a rectangular section, as shown in Figure 4, or it can be a city gate shape or a parabola, as shown in Figure 5, the circumferential drainage ditch 6 is made of surrounding rock surface and thin steel plate. Its pitch is the width of one or two, three ring-shaped flat jacks 1, and decides according to geology and seepage situation. Drainage holes 8 are arranged in the circumferential drainage ditch 6 . The cross-connection of the longitudinal drainage groove 5 and the circumferential drainage groove 6 is shown in Fig. 6 . The entire tunnel constitutes a vertical and horizontal drainage network, until it finally converges into the water collection well, and then is discharged downstream through the water pump.

Certain exemplary embodiments of the present invention have been described above only by way of illustration, and it goes without saying that those skilled in the art can use various methods without departing from the spirit and scope of the present invention. The described embodiments are modified. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the protection scope of the claims of the present invention.

Claims (6)

1. a kind of tunnel structure for bearing external water pressure in height, it is characterised in that：Including：

Some flat jacks (1) for surrounding circle, the outside of the flat jack (1) is outside country rock (2), the country rock (2) Layer is consolidation grouting circle (3),

The pre-stress concrete lining cutting (4) on the inside of flat jack (1) is arranged on,

Drainage system, including longitudinal drainage groove (5), circle draining ditch (6), drainage blanket (7) and osculum (8), the longitudinal direction row Tank (5) is opened in the lowest part on country rock (2) surface, and is connected with sump；The circle draining ditch (6) is opened in flat very heavy Between top (1), and bottom is connected with longitudinal drainage groove (5)；The drainage blanket (7) is located at pre-stress concrete lining cutting (4) and filled with consolidation Between slurry circle (3)；One end of the osculum (8) is connected with circle draining ditch (6), and the other end passes through described country rock (2) simultaneously Close to consolidation grouting circle (3).

2. a kind of tunnel structure for bearing external water pressure in height according to claim 1, it is characterised in that the osculum (8) draining floral tube is filtered in be internally provided with, in one end insertion osculum (8) of the filtering draining floral tube with back cover (13), mistake Filter draining floral tube and include body (9), body (9) if on dried layer filtering non-woven fabric (10) is distributed with.

3. a kind of tunnel structure for bearing external water pressure in height according to claim 1, it is characterised in that the ring row The cross section in ditch (6) is rectangle or arch.

4. a kind of tunnel structure for bearing external water pressure in height according to claim 1, it is characterised in that described adjacent The number of flat jack (1) between two circle draining ditches (6) is one, two or three.

5. the pressure tunnel construction technology for bearing the tunnel structure of external water pressure in height as described in claim any one of 1-4, It is characterized in that：Comprise the following steps：

1) after the completion of tunnel section is excavated, consolidation grouting processing is carried out first；Then setting-out, by the peace of some flat jacks (1) Holding position, longitudinal drainage groove (5), the position of circle draining ditch (6) and osculum (8) are determined；

2) beat osculum (8) in the circle draining ditch (6) and install and filter draining floral tube, after the completion of aperture blocked with stopper, with Anti- debris is fallen into hole；Then country rock (2) between flat jack (1) is if surface lays dried layer filtering draining adhesive-bonded fabric (10)。

3) longitudinal drainage groove (5) is excavated in the bottom of tunnel excavation section and with reinforced concrete lining layer, except with circle draining ditch (6) outside crossover sites, remaining position seals top opening with sheet metal, is fallen into prevent concrete etc. in groove；

4) flat jack (1) is installed along tunnel center line longitudinal direction is uniform, both sides gap is blocked with cement mortar；And it is embedded to slip casting Pipe and blast pipe, to carry out the rockfill grouting of flat jack (1) behind；

5) pull out after the stopper on osculum (8), then the steel plate member on ring gutter (6) top is installed, with thin galvanized wire by structure Part is fixed on fang bolt.The gap of the component and both sides annular flat jack (1) contact site is floating with cement mortar, Form smooth surface；

6) tunnel lining concrete is poured after lining concrete reaches design strength, you can apply External prestressed.

6. a kind of pressure tunnel construction technology for bearing the tunnel structure of external water pressure in height according to claim 5, its Be characterised by, step 1) in consolidation grouting process step be：After the completion of tunnel section is excavated, and drill, hole depth is about tunnel Radius, sets air pressure stop grouting plug (12), air pressure stop grouting plug (12) position in drilling in insertion Grouting Pipe (11), Grouting Pipe (11) At 1/2 hole depth, during grouting, deep layer grouting, 2 times or so internal water pressures of grouting pressure are carried out first；Open air pressure stop grouting plug (12) valve, bleeds off air, and pulls out Grouting Pipe (11), makes position of the air pressure stop grouting plug (12) away from the hole depth of aperture about 1/3 When putting, inflation carries out shallow-layer grouting after only starching.