Plateau mountain area small-clear-distance tunnel construction method

Abstract

The invention provides a plateau mountain area small-clear-distance tunnel construction method which comprises the following steps: firstly, adjusting an excavation section of an advance hole, excavating a contour to cover interlaced rock, and constructing a steel frame; then constructing a side wall support at an excavated position of a front hole support and a rear front hole support; constructing an inverted arch primary support of the preceding hole; constructing an advance hole inverted arch and filling the inverted arch; an upper step of the following hole is excavated, and primary support is constructed; excavating a lower step of the rear hole, and constructing a primary support; excavating an inverted arch of the posterior hole, completing initial supporting of the inverted arch, and removing the part, invading the posterior hole, of the steel frame; constructing a posterior hole inverted arch, and filling the inverted arch; and finally, after tunnel anchor blasting operation is completed, secondary linings of the preceding hole and the following hole are constructed. According to the construction method, the successive hole method is adopted for construction, the construction period is shortened, the cost input is low, and the material and management cost is saved; disturbance to surrounding rocks is small, the vibration influence on blasting of the surrounding rocks is reduced, and the integrity of the surrounding rocks can be effectively kept.

Description

Technical Field

[0001] The invention belongs to the technical field of small clearance tunnel construction, and in particular relates to a small clearance tunnel construction method in plateau mountainous area. Background Art

[0002] Small clearance tunnels usually refer to special tunnel arrangements where the thickness of the middle rock wall in the tunnel is less than the minimum clearance of the separated independent double tunnels. Small clearance tunnel design uses the middle pilot tunnel method for excavation and construction. However, this excavation method is difficult to accurately control, and complex geological conditions may bring more uncertainties and risks, affecting the construction progress. Therefore, a small clearance tunnel construction method for plateau mountainous areas was invented. Summary of the invention

[0003] In view of this, the present invention aims to overcome the defects in the prior art and proposes a method for constructing a small clearance tunnel in a plateau mountainous area.

[0004] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0005] A method for constructing a small clearance tunnel in a plateau mountainous area comprises the following steps:

[0006] S1. The excavation section of the first tunnel is adjusted, the excavation outline covers the middle rock, and the steel frame is constructed;

[0007] S2. Carry out the side wall support of the excavated position of the main tunnel support behind the pilot tunnel;

[0008] S3, construction of the initial support of the inverted arch of the pilot tunnel;

[0009] S4, construction of the invert arch and invert arch filling of the pilot tunnel;

[0010] S5. After excavation, walk up the tunnel to the steps and apply initial support;

[0011] S6. After excavation, build steps under the tunnel and apply initial support;

[0012] S7, excavate the back arch of the rear tunnel, complete the initial support of the back arch, and remove the part of the steel frame that invades the rear tunnel;

[0013] S8, after construction, the tunnel is built and the invert is filled;

[0014] S9. After the tunnel anchor blasting operation is completed, the second lining of the leading tunnel and the trailing tunnel will be constructed.

[0015] Furthermore, the side walls and the middle part of the interlayer rock are backfilled and compacted with shotcrete.

[0016] Furthermore, the initial support closed loop step distance shall not exceed 35m.

[0017] Furthermore, after the advance tunnel is 30m in, the rear tunnel construction is carried out.

[0018] Furthermore, the excavation of the leading tunnel heading must always be 30m ahead of the leading and trailing tunnel headings.

[0019] Furthermore, the initial support of the invert arch of the leading tunnel formed a ring that was 15m ahead of the heading faces of the leading and trailing tunnels.

[0020] Furthermore, controlled blasting was used to expand the pilot tunnel.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The invention provides a method for constructing small-clearance tunnels in plateau mountainous areas. The method adopts the sequential pilot tunnel method to construct small-clearance section tunnels. First, construction preparation is carried out, followed by the construction of the back slope protection at the tunnel entrance, and then the guide wall and pipe shed are constructed. Then the first tunnel body is excavated and supported, and finally the second tunnel body is excavated and supported. Since the sequential pilot tunnel method is used for construction, the construction period can be greatly saved compared with the traditional method; the cost investment is low, and materials and management costs are saved; compared with the traditional middle pilot tunnel method, the blasting process is saved, the disturbance to the surrounding rock is small, and the vibration impact of the blasting on the surrounding surrounding rock is reduced, and the integrity of the surrounding rock can be effectively maintained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0024] Figure 1 This is a construction diagram of step 1 of the present invention;

[0025] Figure 2 This is a construction diagram of step 2 of the present invention;

[0026] Figure 3 This is a schematic diagram of the construction of step 3 of the present invention;

[0027] Figure 4 This is a construction diagram of step 4 of the present invention;

[0028] Figure 5 This is a construction diagram of step 5 of the present invention;

[0029] Figure 6 This is a construction diagram of step 6 of the present invention;

[0030] Figure 7 This is a construction diagram of step 7 of the present invention;

[0031] Figure 8This is a schematic diagram of the construction of step 8 of the present invention;

[0032] Fig. 9 The present invention creates a construction schematic diagram of step 9. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0035] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0036] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0037] A method for constructing a small clearance tunnel in a plateau mountainous area, such as Figures 1 to 9 As shown, the following steps are included:

[0038] S1. The excavation section of the first tunnel is adjusted, the excavation outline covers the middle rock, and the steel frame is constructed;

[0039] S2. Carry out the side wall support of the excavated position of the main tunnel support behind the pilot tunnel;

[0040] S3, construction of the initial support of the inverted arch of the pilot tunnel;

[0041] S4, construction of the invert arch and invert arch filling of the pilot tunnel;

[0042] S5. After excavation, walk up the tunnel to the steps and apply initial support;

[0043] S6. After excavation, build steps under the tunnel and apply initial support;

[0044] S7, excavate the back arch of the rear tunnel, complete the initial support of the back arch, and remove the part of the steel frame that invades the rear tunnel;

[0045] S8, after construction, the tunnel is built and the invert is filled;

[0046] S9. After the tunnel anchor blasting operation is completed, the second lining of the leading tunnel and the trailing tunnel will be constructed.

[0047] The side walls and the middle part of the interlayer rock are backfilled and compacted with shotcrete. The step distance of the initial support and closed ring is not more than 35m. After the first tunnel is 30m into the hole, the construction of the second tunnel is carried out. The excavation of the first tunnel face must always be 30m ahead of the front and rear tunnel faces. The initial support ring of the first tunnel arch is 15m ahead of the front and rear tunnel faces. Controlled blasting is used to expand the first tunnel.

[0048] After the leading tunnel is entered, controlled blasting is used to expand the leading tunnel, install the special-shaped arch frame legs and the arch frame of the lower step of the trailing tunnel. After the leading tunnel is entered for 30m, the trailing tunnel can enter the tunnel for construction. The leading tunnel's heading face excavation must always be 30m ahead of the leading and trailing tunnels' heading faces. The leading tunnel's initial support ring should be 15m ahead of the leading and trailing tunnels' heading faces. The two tunnels can be excavated forward at the same time, but cannot be blasted at the same time. According to the blasting safety regulations and design drawing requirements, the blasting vibration speed is controlled below 5cm / s, and the leading tunnel steel frame ring to the heading face is no more than 35m, and the ring structure should be formed as soon as possible.

[0049] As an example, for the V-III level surrounding rock section, the specific construction organization plan is as follows:

[0050] Construction method for Grade V surrounding rock:

[0051] ① The excavation section of the advance tunnel is adjusted, and the excavation outline covers the interbedded rock, and the construction method is the full-section method; the excavation method of the subsequent tunnel is the micro-step method. ② The spacing between the steel frames of the pilot tunnel and the rear tunnel is 60cm / frame; the pilot tunnel is equipped with a 20a steel support frame on the middle rock side, with a spacing of 60cm / frame, and two φ42 locking anchor pipes are set at the steel frame connection and the arch foot, with a total of two groups; the spacing of the steel mesh grid on the side wall of the rear tunnel on the middle rock side is 20cm×20cm; the advance small guide tube support measures are adopted in the range of 60° to 60° from the inner side of the middle rock of the pilot tunnel and the rear tunnel, with a single length of 4m, a circumferential spacing of 40cm, and a longitudinal overlap of not less than 2m; the advance support measures of φ42 small guide tube + grouting are adopted in the range of 60° to 90° from the inner side of the middle rock of the pilot tunnel and the rear tunnel, with a single length of 4m, a circumferential spacing of 40cm, and a longitudinal overlap of not less than 2m; system anchor rods are driven at the side wall, with a length of 4m and a spacing of 1m×1m (circumferential×longitudinal). ③When the first tunnel is excavated, the steel frame of the side wall of the rear tunnel near the middle rock is reserved for installation. The parts with a net distance of less than 25cm between the two steel frames within the lower step range are connected with φ22 stirrups, with a stirrup spacing of 40cm. The longitudinal connection reinforcement of the steel frame at this part is 60cm in the circumferential direction. ④The first tunnel is constructed first, and then the rear tunnel is constructed in sequence. This section adopts controlled blasting excavation.

[0052] Construction method for Grade IV surrounding rock:

[0053] ① The excavation section of the pilot tunnel is adjusted, and the excavation outline covers the middle rock. The construction method is the full section method; the excavation method of the rear tunnel is the micro-step method. ② The spacing between the steel frames of the rear tunnel and the pilot tunnel is adjusted to 80cm / frame; I18 steel support steel frames are added to the side of the pilot tunnel near the middle rock, with a spacing of 80cm / frame, and 2 φ42 locking foot anchor pipes are set at the connection between the steel frame and the arch foot, a total of two groups; the spacing of the steel mesh grid of the side wall of the rear tunnel near the middle rock is 20cm×20cm. In the leading tunnel and the trailing tunnel, the φ60 medium pipe shelf + grouting advance support measures are adopted in the range of 60° to 60° on the inner side of the rock in the leading tunnel and the trailing tunnel (the φ60 medium pipe shelf support is not applied in the 30m pipe shelf area of ​​the tunnel entrance, and the advance small guide tube support is adopted). The length of a single pipe shelf is 9m, the circumferential spacing is 40cm, and the longitudinal overlap is not less than 3.2m; in the leading tunnel and the trailing tunnel, the φ42 small guide tube + grouting advance support measures are adopted in the range of 60° to 90° on the inner side of the rock in the leading tunnel and the trailing tunnel. The length of a single small guide tube is 5m, the circumferential spacing is 40cm, and the longitudinal overlap is not less than 2.4m; system anchors are driven at the side walls, with a driving length of 3m and a spacing of 1.2m×1.2m (circumferential×longitudinal). ③Add φ42 steel tubes within 90° of the arch of the middle interlayer rock (the en-stepping part above the middle interlayer rock) in the leading and trailing tunnels for radial grouting reinforcement in order to improve the bearing capacity of the middle interlayer rock. The outer diameter of the steel tube is 42mm, the wall thickness is 3.5mm, the length is 4.0m, the spacing is 1.0m×1.0m (circumferential×longitudinal), and the plum blossom arrangement is arranged. The angle of the steel tube is appropriately adjusted upward according to the change of clearance. The grouting material is cement single liquid slurry. ④When the leading tunnel is excavated, the steel frame of the side wall of the trailing tunnel close to the middle interlayer rock is installed and reserved. The parts with a net distance of less than 25cm between the two steel frames within the range of the lower step are connected with φ22 stirrups. The spacing between the stirrups is 40cm, and the circumferential spacing of the longitudinal connecting reinforcement of the steel frame in this part is 60cm. ⑤Controlled blasting is used for blasting, and the vibration monitoring speed is not more than 5cm / s.

[0054] Construction method for Grade III surrounding rock:

[0055] ① The excavation section of the pilot tunnel is adjusted, and the excavation profile covers the middle interlayer rock. The construction method is the full section method, and the excavation method of the rear tunnel is the micro-step method. ② The spacing between the steel frames of the rear tunnel and the pilot tunnel is adjusted to 1m / frame; I16 steel support steel frames are added to the side of the pilot tunnel near the middle interlayer rock, with a spacing of 1m / frame, and 2 φ42 locking foot anchor pipes are set at the connection of the steel frame and the arch foot, a total of two groups; the grid spacing of the steel mesh of the side wall of the rear tunnel near the middle interlayer rock is 25cm×25cm; φ42 small guide tubes + grouting advance support measures are adopted in the range of 90° to 60° from the inner side of the middle interlayer rock of the pilot tunnel and the rear tunnel. The length of a single small guide tube is 4m, the circumferential spacing is 40cm, and the longitudinal overlap is not less than 2m; the other support measures are consistent with the original design. ③Determine whether radial grouting is needed in combination with the surrounding rock excavation situation; add φ42 steel flower pipes within 90° of the arch of the middle interlayer rock in the leading and trailing tunnels for radial grouting reinforcement in order to improve the bearing capacity of the middle interlayer rock. The outer diameter of the steel flower pipe is 42mm, the wall thickness is 3.5mm, the length is 4.0m, the spacing is 1.0m×1.0m (circumferential×longitudinal), and the plum blossom arrangement is arranged. The angle of the steel flower pipe is appropriately adjusted upward according to the change of clearance. The grouting material is cement single liquid slurry. ④When the leading tunnel is excavated, the steel frame of the side wall of the trailing tunnel close to the middle interlayer rock is installed and reserved. The parts with a net distance of less than 25cm between the two steel frames within the range of the lower step are connected with φ22 stirrups, the stirrup spacing is 40cm, and the circumferential spacing of the longitudinal connecting reinforcement of the steel frame in this part is 60cm. ⑤Use controlled blasting, and the vibration monitoring speed of blasting vibration is not more than 5cm / s.

[0056] The invention provides a method for constructing small-clearance tunnels in plateau mountainous areas. The method adopts the sequential pilot tunnel method to construct small-clearance section tunnels. First, construction preparation is carried out, followed by the construction of the back slope protection at the tunnel entrance, and then the guide wall and pipe shed are constructed. Then the first tunnel body is excavated and supported, and finally the second tunnel body is excavated and supported. Since the sequential pilot tunnel method is used for construction, the construction period can be greatly saved compared with the traditional method; the cost investment is low, and materials and management costs are saved; compared with the traditional middle pilot tunnel method, the blasting process is saved, the disturbance to the surrounding rock is small, and the vibration impact of the blasting on the surrounding surrounding rock is reduced, and the integrity of the surrounding rock can be effectively maintained.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for constructing a small clearance tunnel in a plateau mountainous area, characterized in that: The steps include: S1. The excavation section of the first tunnel is adjusted, the excavation outline covers the middle rock, and the steel frame is constructed; S2. Carry out the side wall support of the excavated position of the main tunnel support behind the pilot tunnel; S3, construction of the initial support of the inverted arch of the pilot tunnel; S4, construction of the invert arch and invert arch filling of the pilot tunnel; S5. After excavation, walk up the tunnel to the steps and apply initial support; S6. After excavation, build steps under the tunnel and apply initial support; S7, excavate the back arch of the rear tunnel, complete the initial support of the back arch, and remove the part of the steel frame that invades the rear tunnel; S8, after construction, the tunnel is built and the invert is filled; S9. After the tunnel anchor blasting operation is completed, the second lining of the leading tunnel and the trailing tunnel will be constructed.

2. A method for constructing a small clearance tunnel in a plateau mountainous area according to claim 1, characterized in that: The side walls and middle parts of the interlayer rock are backfilled and compacted with sprayed concrete.

3. The method for constructing a small clearance tunnel in a plateau mountainous area according to claim 1, characterized in that: The step distance of the initial support closed ring shall not exceed 35m.

4. The method for constructing a small clearance tunnel in a plateau mountainous area according to claim 1, characterized in that: After the advance tunnel has been entered for 30m, the rear tunnel construction will be carried out.

5. The method for constructing a small clearance tunnel in a plateau mountainous area according to claim 1, characterized in that: The excavation of the leading tunnel heading must always be 30m ahead of the leading and trailing tunnel headings.

6. The method for constructing a small clearance tunnel in a plateau mountainous area according to claim 1, characterized in that: The initial support of the invert arch of the leading tunnel forms a ring that is 15m ahead of the headings of the leading and trailing tunnels.

7. The method for constructing a small clearance tunnel in a plateau mountainous area according to claim 1, characterized in that: Controlled blasting is used to expand the pilot tunnel.

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