Support Structure System and Construction Method for Large Deformation Tunnels in Soft Rock with Bias Pressure

Abstract

The present invention relates to the field of railway tunnel construction, and particularly relates to a support structure system for a tunnel with large deformation of soft rock under bias pressure and a construction method thereof. It includes: Step 1, establishing an initial support deformation database; Step 2, selecting characteristic values of reserved deformation amounts at different positions; Step 3, separately designing the initial support section; Step 4, separately designing the construction of the initial support; Step 5, constructing the originally designed initial section; Step 6, compensating grouting; Step 7, constructing the secondary lining. Repeat Steps 1 to 7 multiple times to pass through the large deformation section of soft rock under bias pressure. The present invention can prevent and reduce the problem of repeatedly replacing the arch in a soft rock tunnel under bias pressure, avoid the synchronous amplification of the entire full section during the deformation of the initial support of the tunnel, cause serious overconsumption of the secondary lining concrete in some sections, improve the construction efficiency and save costs.

Description

Technical Field

[0001] The present invention relates to the technical field of railway tunnel construction, and particularly relates to a support structure system for a tunnel with large deformation of soft rock under unsymmetrical pressure and its construction method. Background Art

[0002] During the construction of Jingzhai Tunnel on the Yuxi-Mohan Railway in the southwest region, due to extremely complex geological conditions, sensitive environment, and fragile ecology, there are a large number of soft surrounding rocks in the tunnel site area. The soft surrounding rocks are widely distributed, with poor rock mass conditions, serious interbedding phenomena, poor interlayer connection, easy softening when encountering water, obvious anisotropy and rheological characteristics. And due to the large buried depth of the tunnel, extremely high initial ground stress will be generated. Under the superposition of the above adverse factors, the tunnel undergoes large deformations of varying degrees. The uncertainty of the deformation position and the non-uniformity of the deformation amount result in the deformation amount of the large deformation being much larger than the reserved deformation amount, causing problems such as the peeling of the primary support, the bulging of the side wall, and serious intrusion due to excessive deformation. In the case of serious intrusion, the primary support must be replaced, which has a very adverse impact on the safety of construction personnel and equipment and the construction progress.

[0003] During construction, due to unsymmetrical pressure and uneven distribution of the surrounding rock, the integrity of the surrounding rock at the tunnel face is uneven, one side is good and the other side is bad, with different stabilities, ultimately resulting in the non-uniformity of the deformation of the primary support and a large deformation of the primary support steel frame. Currently, for the treatment measures of the non-uniform large deformation of soft rock tunnels under unsymmetrical pressure, most of them select the maximum deformation amount as the reserved settlement amount and enlarge the whole section in the original design. The construction method is relatively conservative, and the excavation section is enlarged too much. On the side with good surrounding rock stability, the deformation amount is far less than the reserved deformation amount. Subsequently, during the construction of the secondary lining, the concrete overbreak is serious, resulting in waste of costs. When constructing the secondary lining, the trolley is seriously unsymmetrically pressured, posing a safety hazard. For the tunnel, it seriously affects the construction efficiency. Therefore, a better support structure system and its construction method are needed to ensure the construction progress, cost, and safety. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a support structure system for a tunnel with large deformation of soft rock under unsymmetrical pressure and its construction method to solve the above problems, control the deformation of the tunnel with soft rock under unsymmetrical pressure, and ensure safety while the measures are simple, low-cost, and high-efficiency.

[0005] The present invention provides a support structure system for a tunnel with large deformation of soft rock under unsymmetrical pressure and its construction method, which is characterized by including the following steps:

[0006] Step 1: Statistically establish a database for the deformation amount of the primary support of the soft rock tunnel under unsymmetrical pressure, and analyze the convergence and settlement amounts at different positions of the tunnel section;

[0007] Step 2: Select characteristic values of the reserved deformation amount at different positions of the tunnel according to the monitored data;

[0008] Step 3: Independently design the initial support section according to the reserved deformation amount eigenvalue;

[0009] Step 4: During the tunnel excavation process, complete the tunnel excavation according to the independently designed initial support section, and complete the subsequent initial support construction;

[0010] Step 5: After the initial support of the independently designed section is completed, continuously observe the deformation of the tunnel. When the tunnel section is close to the original designed tunnel section, immediately construct the original designed initial support;

[0011] Step 6: After the original designed initial support is constructed, grout for reinforcement, and perform compensatory grouting during each excavation cycle;

[0012] Step 7: Construct the secondary lining of the tunnel.

[0013] In the above Step 1, the database includes crown settlement and side wall convergence.

[0014] In the above Step 2, different positions of the tunnel include the crown, left springing point, right springing point, left arch waist point, right arch waist point, left arch foot point, and right arch foot point. The reserved deformation amount eigenvalue is the maximum cumulative value of crown settlement and side wall convergence in the database.

[0015] The springing point is located at the side wall position 640 - 660 cm above the arch foot. The arch waist point is located at the side wall position 200 - 220 cm above the arch foot. The crown point is the intersection point of the tunnel center line and the tunnel contour.

[0016] In Step 3, the initial support section is independently designed according to the reserved deformation amount eigenvalue. The design method is to use the five - circle tangency method after point - by - point fitting: The first circle is designed with the crown point and the springing points; The connections between the left and right springing points and the arch waist points are used as chords 1 and 2 of the second and third circles. The springing points are the tangent points of the first circle with the second and third circles. The second and third circles are designed through chords 1 and 2 and the left and right springing points; The connections between the left and right arch waist points and the arch foot points are used as chords 3 and 4 of the fourth and fifth circles. The arch waist points are the tangent points of the second and third circles with the fourth and fifth circles. The fourth and fifth circles are designed through chords 3 and 4 and the left and right arch waist points.

[0017] In Step 4, the tunnel is excavated using the three - bench method. The length of each bench is controlled within 5 - 6 m. The initial support is to install bolts, steel frames, drive foot - locking anchor pipes, advanced support, and then hang the mesh and spray concrete for closure.

[0018] The rock bolt used is a Ф22 resin rock bolt, the anchoring agent used is a Ф28 quick-anchoring agent, and the spacing of the rock bolts in the circumferential and longitudinal directions is 1m × 1m; the steel frame includes a section steel arch frame and a lattice arch frame, and the spacing of the steel frames is controlled between 0.5 - 0.8m; the foot-locking anchor pipe used is a Ф42 seamless steel pipe with a length of 4.5m, and the driving angle is controlled between 20° and 30°. The foot-locking anchor pipe is connected to the steel frame by an L-shaped bar. The grouting of the foot-locking anchor pipe uses a double-fluid grout, with cement slurry: water glass = 1:1, and the grouting pressure is controlled between 0.5 - 1.5 Mpa; the advanced support includes advanced small pipes and advanced pipe sheds, and the driving angle of the advanced support is controlled between 10° and 20°. The grouting of the advanced support uses a double-fluid grout, with cement slurry: water glass = 1:1, and the grouting pressure is controlled between 0.5 - 1.5 Mpa; the shotcrete is constructed in slices and layers by a wet shotcreting manipulator.

[0019] In Step 5, the original designed initial support is constructed, including the steel frame, foot-locking, wire meshing, and shotcrete for closure.

[0020] The steel frame includes a section steel arch frame and a lattice arch frame, and the spacing of the steel frames is controlled between 0.5 - 0.8m; the foot-locking anchor pipe used is a Ф42 seamless steel pipe with a length of 4.5m, and the driving angle is controlled between 20° and 30°. The foot-locking anchor pipe is connected to the steel frame by an L-shaped bar; the grouting of the foot-locking anchor pipe uses a double-fluid grout, with cement slurry: water glass = 1:1, and the grouting pressure is controlled between 0.5 - 1.5 Mpa.

[0021] In Step 6, the compensatory grouting is carried out by the method of radial grouting for the arch and wall. The diameter of the grouting hole is Ф50mm, the depth is 3m, the grouting uses a double-fluid grout, with cement slurry: water glass = 1:1, and the grouting pressure is controlled between 1.5 - 2 Mpa.

[0022] The advantages of the present invention are as follows:

[0023] 1. The present invention mainly solves the problems of uneven deformation of the initial support in soft and bias-pressure railway tunnels and the problems of cracking and intrusion of the initial support caused by large deformation. By selecting different positions to reserve characteristic values of deformation amounts and designing sections separately + compensatory grouting and other measures to deal with the uneven large deformation of soft and bias-pressure tunnels, it avoids the replacement of the arch due to the intrusion of the initial support, has a low cost, improves the strength of the initial support, ensures construction safety, saves costs, avoids arch replacement, and shortens the construction period.

[0024] 2. The support structure system and construction method for bias-pressure soft rock large-deformation tunnels provided by the present invention can be directly applied to the actual construction of soft and bias-pressure tunnels, and can avoid the situation of over-consumption of the secondary lining concrete and cost waste caused by the deformation amount being less than the reserved deformation amount in traditional construction. Description of the Drawings

[0025] Figure 1 It is a flow chart of the method of the present invention.

[0026] Figure 2 This is a schematic diagram of the support structure system for a large-deformation tunnel in soft rock with bias pressure of the present invention.

[0027] Figure 3 This is a schematic diagram of the cross-section design with five circles tangent to each other of the present invention.

[0028] Figure 4 This is a schematic diagram of the deformation data acquisition points of the initial support deformation of a large-deformation tunnel in soft rock with bias pressure of the present invention.

[0029] Figure 5 This is a schematic diagram of the initial support surface after deformation before construction of the construction method of the support structure system for a large-deformation tunnel in soft rock with bias pressure of the present invention.

[0030] Figure 6 This is a schematic diagram of the initial support surface after deformation after the construction of the construction method of the support structure system for a large-deformation tunnel in soft rock with bias pressure of the present invention.

[0031] In the figure: 1 - independently designed initial support section, 2 - five-circle tangent arch frame, 3 - foot-locking anchor pipe, 4 - resin bolt, 5 - advanced support, 6 - originally designed initial support, 7 - invert, 8 - initial support of the invert, 9 - secondary lining. Detailed implementation manners

[0032] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Embodiment 1

[0034] As Figures 1 to 6 shown, this embodiment provides a support structure system for a large-deformation tunnel in soft rock with bias pressure and its construction method. When soft and bias-pressure surrounding rock appears during the tunnel excavation process, it includes the following steps:

[0035] Step 1: Statistically establish an initial support deformation database for the deformation amount of the soft rock initial support; the initial support deformation database includes crown settlement and side wall convergence.

[0036] Step 2: Select the characteristic values of the reserved deformation amount at different positions of the tunnel according to the monitored and measured data; different positions include the crown, left springing point, right springing point, left arch waist point, right arch waist point, left arch foot point, and right arch foot point. The specific situation is as shown in the appendix Figure 2As shown in the figure. The springing point is located at the side wall position 660 cm above the arch foot; the waist point of the arch is located at the side wall position 200 cm above the arch foot; the apex point of the arch is the intersection point of the tunnel center line and the tunnel contour; the characteristic value of the reserved deformation amount is the maximum cumulative value of the crown settlement and the side wall convergence in the database.

[0037] Step 3: Design the initial support section separately according to the characteristic value of the reserved deformation amount; the design method is to adopt the method of five-circle tangency after point-by-point fitting: the first circle is designed with the apex point of the arch and the springing point; the connections between the two springing points and the waist points of the arch are used as chord 1 and chord 2 of the second circle and the third circle, and the springing point is used as the tangent point of the first circle and the second circle and the third circle. The second circle and the third circle are designed through chord 1, chord 2, and the two springing points; the connections between the two waist points of the arch and the arch foot points are used as chord 3 and chord 4 of the fourth circle and the fifth circle, and the waist point is used as the tangent point of the second circle and the third circle and the fourth circle and the fifth circle. The fourth circle and the fifth circle are designed through chord 3, chord 4, and the two waist points of the arch.

[0038] Step 4: During the tunnel excavation process, complete the tunnel excavation according to the separately designed initial support section, and complete the subsequent initial support construction; in step 4, the tunnel excavation adopts the three-bench method, and the length of each bench is controlled within 5 m. The initial support is to install bolts, steel frames, drive locking foot anchor pipes, advanced support, and hang nets and spray concrete for closure. The bolts adopt Ф22 resin bolts, and the anchoring agents adopt Ф28 quick-acting anchoring agents. The bolt spacing in the circumferential direction × longitudinal direction is 1 m × 1 m. The steel frames include section steel arch frames and lattice arch frames. The spacing of the steel frames is controlled within 0.5 m. The locking foot anchor pipes adopt Ф42 seamless steel pipes with a length of 4.5 m, and the driving angle is controlled at 20°. The locking foot anchor pipes and the steel frames are connected by L-shaped bars. The locking foot anchor pipes are grouted with double-fluid grout, cement slurry: water glass = 1:1, and the grouting pressure is controlled at 0.5 Mpa. The advanced support includes advanced small pipes and advanced pipe roofs. The driving angle of the advanced support is controlled at 10°. The advanced support is grouted with double-fluid grout, cement slurry: water glass = 1:1, and the grouting pressure is controlled at 0.5 Mpa. The wet shotcrete is constructed in slices and layers by a wet shotcreting robot.

[0039] Step 5: After the initial support of the separately designed section is completed, continuously observe the deformation of the tunnel. When the tunnel section is close to the original designed tunnel section, immediately construct the original designed initial support; adopt the original designed parameters.

[0040] Step 6: After the construction of the original designed initial support is completed, grout for reinforcement, and perform compensatory grouting during each excavation cycle; the compensatory grouting adopts the method of radial grouting of the arch wall. The diameter of the grouting hole is Ф50 mm, and the depth is 3 m. The grouting adopts double-fluid grout, cement slurry: water glass = 1:1, and the grouting pressure is controlled at 1.5 Mpa.

[0041] Step 7, secondary lining construction of the tunnel; the initial support is closed in time, the distance between the end of the inverted arch and the excavation face is controlled within 35 m, and the distance between the end of the secondary lining and the excavation face is controlled within 60 m.

[0042] This example can well control the uneven deformation of the soft and bias-pressure tunnel, and can avoid the over-consumption of secondary lining concrete caused by the deformation amount being less than the reserved deformation amount in traditional construction, thus avoiding the situation of cost waste. It has strong adaptability and strong popularization potential.

[0043] Example 2

[0044] In this example, each step of the support structure system for the bias-pressure soft rock large-deformation tunnel and its construction method is the same as that in Example 1. The differences are as follows:

[0045] In Step 2, the springing point is located at the side wall position 425 cm above the arch foot; the waist point of the arch is located at the side wall position 210 cm above the arch foot;

[0046] In Step 4, the length of each bench is controlled within 5.5 m; the spacing of the steel frames is controlled within 0.6 m; the locking foot anchor pipes adopt Ф42 seamless steel pipes with a length of 4.5 m, and the driving angle is controlled within 25°. The locking foot anchor pipes are connected to the steel frames by L-shaped bars. The grouting of the locking foot anchor pipes adopts double-fluid grout, with the cement slurry: water glass = 1:1, and the grouting pressure is controlled within 1.0 Mpa. The advanced support includes advanced small pipes and advanced pipe roofs. The driving angle of the advanced support is controlled within 15°. The grouting of the advanced support adopts double-fluid grout, with the cement slurry: water glass = 1:1, and the grouting pressure is controlled within 1.0 Mpa;

[0047] In Step 6, the grouting pressure is controlled within 1.75 Mpa.

[0048] Example 3

[0049] In this example, each step of the support structure system for the bias-pressure soft rock large-deformation tunnel and its construction method is the same as that in Example 1. The differences are as follows:

[0050] In Step 2, the springing point is located at the side wall position 440 cm above the arch foot; the waist point of the arch is located at the side wall position 220 cm above the arch foot;

[0051] In Step 4, the length of each bench is controlled within 6 m; the spacing of the steel frames is controlled within 0.8 m; the locking foot anchor pipes adopt Ф42 seamless steel pipes with a length of 4.5 m, and the driving angle is controlled within 30°. The locking foot anchor pipes are connected to the steel frames by L-shaped bars. The grouting of the locking foot anchor pipes adopts double-fluid grout, with the cement slurry: water glass = 1:1, and the grouting pressure is controlled within 1.5 Mpa. The advanced support includes advanced small pipes and advanced pipe roofs. The driving angle of the advanced support is controlled within 20°. The grouting of the advanced support adopts double-fluid grout, with the cement slurry: water glass = 1:1, and the grouting pressure is controlled within 1.5 Mpa;

[0052] In Step 6, the grouting pressure is controlled at 2 Mpa.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Construction method of support structure system for large deformation tunnel in soft rock under bias pressure, characterized in that, It includes the following steps: Step 1: Statistically establish a database for the initial support deformation of a large-deformation tunnel in soft rock with bias pressure, and analyze the convergence and settlement at different positions of the tunnel section; the database includes crown settlement and sidewall convergence; Step 2: Select the characteristic values of the reserved deformation amount at different positions of the tunnel according to the monitored data; the different positions of the tunnel include the crown point, the left springing point, the right springing point, the left arch waist point, the right arch waist point, the left arch foot point, and the right arch foot point, and the characteristic value of the reserved deformation amount is the maximum cumulative value of the crown settlement and sidewall convergence in the database; Step 3: Independently design the initial support section according to the characteristic value of the reserved deformation amount; the design method is to use the method of five-circle tangency after point-by-point fitting: the first circle is designed by the three points of the crown point and the springing points; the connection between the two springing points and the arch waist points is used as the chords 1 and 2 of the second and third circles, and the springing points are used as the tangent points of the first circle and the second and third circles, and the second and third circles are designed through the chords 1 and 2 and the two springing points; the connection between the two arch waist points and the arch foot points is used as the chords 3 and 4 of the fourth and fifth circles, and the arch waist points are used as the tangent points of the second and third circles and the fourth and fifth circles, and the fourth and fifth circles are designed through the chords 3 and 4 and the two arch waist points; Step 4: During the tunnel excavation process, complete the tunnel excavation according to the independently designed initial support section, and complete the subsequent initial support construction; Step 5: After the independently designed initial support of the section is completed, continuously observe the deformation of the tunnel. When the tunnel section is close to the original designed tunnel section, immediately construct the original designed initial support, including steel frames, foot-locking, mesh hanging, and shotcrete sealing. The steel frames include section steel arch frames and lattice arch frames, and the spacing of the steel frames is controlled between 0.5 - 0.8m; The foot-locking anchor pipes use Ф42 seamless steel pipes with a length of 4.5m, and the driving angle is controlled between 20° - 30°. The foot-locking anchor pipes are connected to the steel frames by L-shaped bars; the grouting of the foot-locking anchor pipes uses double-liquid grout, cement slurry: water glass = 1:1, and the grouting pressure is controlled between 0.5 - 1.5Mpa; Step 6: After the construction of the original designed initial support is completed, grout for reinforcement, and compensation grouting is carried out during each excavation cycle; the compensation grouting adopts the method of radial grouting of the arch and wall. The diameter of the grouting holes is Ф50mm and the depth is 3m. The grouting uses double-liquid grout, cement slurry: water glass = 1:1, and the grouting pressure is controlled between 1.5 - 2Mpa; Step 7: Tunnel secondary lining construction.

2. The construction method of the support structure system for a large-deformation tunnel in soft rock with bias voltage according to claim 1, characterized in that, The springing points are located at the sidewall position 640 - 660cm above the arch feet, the arch waist points are located at the sidewall position 200 - 220cm above the arch feet, and the crown point is the intersection point of the tunnel center line and the tunnel contour.

3. The construction method of the bias pressure soft rock large deformation tunnel support structure system according to claim 1, characterized in that: In Step 4, the tunnel excavation adopts the three-step method, and the length of each step is controlled between 5 - 6m. The initial support is to install bolts, steel frames, drive foot-locking anchor pipes, advanced support, and hang mesh and shotcrete for sealing.

4. The construction method of the support structure system for a large-deformation tunnel in soft rock with bias pressure according to claim 3, characterized in that: In the initial support construction of Step 4, the anchor rods used are Ф22 resin anchor rods with a circumferential × longitudinal spacing of 1m × 1m; the steel frames include section steel arch frames and lattice arch frames, and the spacing of the steel frames is controlled between 0.5 - 0.8m; the foot-locking anchor pipes are made of Ф42 seamless steel pipes with a length of 4.5m, and the driving angle is controlled between 20° and 30°. The foot-locking anchor pipes are connected to the steel frames with L-shaped bars. The grouting of the foot-locking anchor pipes uses double-fluid grout, with cement slurry: water glass = 1:1, and the grouting pressure is controlled between 0.5 - 1.5 Mpa; the advanced support includes advanced small pipes and advanced pipe roofs, and the driving angle of the advanced support is controlled between 10° and 20°. The grouting of the advanced support uses double-fluid grout, with cement slurry: water glass = 1:1, and the grouting pressure is controlled between 0.5 - 1.5 Mpa; wet shotcreting robots are used for layered construction of shotcrete in slices.

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