Multi-arch tunnel construction method suitable for IV-level and above surrounding rock

Abstract

The invention provides a multi-arch tunnel construction method suitable for IV-level and above surrounding rock, and belongs to the technical field of tunnel construction. The method comprises the steps of excavating a front hole and a rear hole, dividing a lower step into a left part and a right part, and supporting while excavating. After the upper step is excavated in the first hole, the right side of the lower step is excavated first, then the left side is excavated, a cavity is excavated when the right side of the lower step is excavated, a vibration isolation box is arranged at the cavity to serve as an upper surrounding rock supporting device, and the left side of the vibration isolation box is filled with foaming materials. After forepoling of the backward hole is conducted, vibration isolation holes are formed in the left side of an upper step, an upper step arc-shaped pilot tunnel is excavated, the left side of a lower step is excavated, the right side of a vibration isolation box is filled with foaming materials, and primary support is conducted; sequentially excavating the right side of the upper step and the right side of the lower step of the following hole, and constructing a primary support; and after the preliminary bracing of the preceding hole is closed stably, the pouring time of the secondary lining is determined through blasting vibration monitoring data. The construction steps and the surrounding rock disturbance frequency can be reduced, the construction quality is improved, and the construction progress is accelerated.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to a multi-arch tunnel construction method suitable for surrounding rocks of grade IV or above. Background Art

[0002] The arch tunnel is widely used in tunnel engineering because of its small footprint, convenient line deployment, smooth line shape, and convenient connection with bridges in later construction. The construction methods of arch tunnels are the middle guide tunnel method and the three guide tunnel method, which are widely used. There are more technical theories and construction experience. The construction steps are generally to construct the middle guide tunnel first, and then construct the middle partition wall after the middle guide tunnel is connected, and then the main tunnel is constructed. After the construction of the middle guide tunnel, the initial support of the guide tunnel is required to maintain the stability of the surrounding rock of the middle guide tunnel, and the temporary support needs to be removed in the later stage. The construction steps are relatively complicated, and the disturbance frequency of the tunnel surrounding rock is aggravated, which increases the construction period and construction cost. In the construction of arch tunnels, the distance between the left and right tunnels is relatively close. The blasting construction of the rear tunnel will have a greater impact on the leading tunnel. If the blasting charge is too small, the construction progress will be slow. If the blasting charge is too large, it will easily lead to the initial support of the leading tunnel. Fracture, deformation of the steel arch frame, delay the pouring time of the secondary lining of the tunnel, increase the construction period, and it is difficult to improve the construction efficiency.

[0003] Therefore, there is an urgent need for a construction method for a multi-arch tunnel that can improve construction efficiency and reduce the impact of blasting construction on the tunnel support structure. Summary of the invention

[0004] In view of this, in order to solve the technical problem that in the existing multi-arch tunnel construction, the blasting construction of the subsequent tunnel affects the leading tunnel, resulting in slow construction progress, low construction efficiency and difficulty in improving the construction efficiency, the present invention provides a multi-arch tunnel construction method suitable for surrounding rock of grade IV and above, which can effectively reduce the construction steps and the frequency of surrounding rock disturbance, improve the construction quality and speed up the construction progress.

[0005] To achieve the above object, the present invention provides the following technical solutions: A construction method for a multi-arch tunnel suitable for surrounding rock of grade IV or above, comprising the following steps: Step (1), carry out advance support for the pilot tunnel, excavate the upper step of the pilot tunnel, and promptly carry out initial support for the arch of the upper step; Step (2), excavating the right side of the lower step of the pilot tunnel, and expanding the cavity on the right side of the pilot tunnel, setting a vibration isolation box at the cavity as an upper surrounding rock support device, and filling the left side of the vibration isolation box with foam material; Step (3), provide initial support for the right side wall of the step below the pilot tunnel; Step (4), excavating the left side of the lower step of the pilot tunnel, constructing the initial support for the left side of the lower step, and casting the initial support for the invert arch; Step (5), perform advance support for the rear tunnel, set a vibration isolation hole on the inner side of the blasting hole around the left side of the upper step, excavate an arc-shaped pilot pit on the upper step of the rear tunnel, and perform initial support for the arch of the upper pilot pit; Step (6), after excavation, on the left side of the lower step of the tunnel, use foam material to fill the cavity on the right side of the vibration isolation box in step (2), and perform initial support on the left side wall of the lower step; Step (7), after excavation, go to the right side of the upper step; and carry out initial support on the right side of the upper step; Step (8), excavate the right side of the lower step of the tunnel, and provide initial support for the right side wall of the lower step, and cast the initial support for the invert arch; Step (9), determining the pouring time of the secondary lining of the pilot hole by monitoring and measuring the blasting vibration velocity, pouring the secondary lining of the pilot hole, and penetrating the pilot hole; Step (10): After the first tunnel is penetrated, the secondary lining of the rear tunnel is poured, and the rear tunnel is penetrated, and the construction is completed.

[0006] Preferably, in step (1), when the surrounding rock grade is grade IV, advanced support is provided, specifically: advanced support is arranged in a circumferential direction; When the surrounding rock grade is above Grade IV, no advance support shall be provided; When the surrounding rock grade is IV, the initial support is to set up steel arches first and then spray concrete; When the surrounding rock grade is above Grade IV, initial support only requires shotcrete.

[0007] Preferably, the length of the leading small catheter is 3-5 m, the circumferential spacing is 40 cm, and the external insertion angle range is 5-12°.

[0008] Preferably, in step (2), a cavity is excavated on the right side of the pilot hole by a grooving method. After the cavity is excavated and expanded, a vibration isolation box is set. A steel plate is welded on the left side of the vibration isolation box. The left side gap is filled with foam material. The right side gap is not filled as a reserved vibration isolation cavity. After the surrounding rock on the top of the vibration isolation box is leveled, the foam material is used to fill it so that the top of the vibration isolation box is in close contact with the surrounding rock.

[0009] Preferably, in step (5), the diameter and arrangement spacing of the circumferential vibration isolation holes are determined according to the surrounding rock conditions, and the arrangement range is 45 to 60 degrees inside the peripheral eye on the left side of the upper step.

[0010] Preferably, double rows of vibration isolation holes are arranged when the surrounding rock grade is Grade IV, and single row of vibration isolation holes are arranged when the surrounding rock grade is above Grade IV.

[0011] Preferably, the diameter of the vibration isolation hole is 108 mm, the hole depth is ≤5 m, and the circumferential spacing of the holes is in the range of 30 to 40 cm.

[0012] Preferably, in step (6), the left side of the lower bench of the subsequent tunnel is closer to the preceding tunnel. When excavating, smooth surface millisecond blasting is adopted, the smallest possible charge amount is selected, low detonation velocity explosives are used, and after construction, the reserved cavity on the right side of the vibration isolation box is filled with foaming materials, and the initial support on the left side of the lower bench is constructed in a timely manner.

[0013] Preferably, in step (9), blasting vibration monitoring and measurement are carried out. The velocity sensors are fixed on the secondary lining of the preceding tunnel, generally arranged on the blasting-facing side, with no less than 4 measuring points, and the test frequency is once per blast.

[0014] Preferably, in step (10), the pouring of the secondary lining of the subsequent tunnel and the secondary lining of the preceding tunnel should be staggered.

[0015] The present invention has the following beneficial effects compared with the prior art: The present invention is applicable to the construction of connected-arch tunnels in surrounding rocks of grade IV and above. Compared with the prior art, it has the following beneficial effects: (1) Compared with the traditional middle pilot tunnel or three pilot tunnel methods, the construction steps and the number of times of surrounding rock disturbance are effectively reduced, the self-stabilizing ability of the surrounding rock is fully exerted, the stability of the surrounding rock during construction is ensured, and the construction speed and quality are improved.

[0016] (2) By optimizing the construction sequence of the preceding tunnel and the subsequent tunnel, setting vibration isolation boxes and vibration isolation holes, the vibration disturbance of the subsequent tunnel blasting construction to the preceding tunnel is reduced, and the safety of the support structure of the preceding tunnel is ensured.

[0017] (3) According to different surrounding rock grades, the parameters of the advanced support, initial support, vibration isolation holes and vibration isolation boxes are flexibly adjusted to better adapt to different geological conditions and improve the construction safety.

[0018] (4) By monitoring the vibration velocity of the blasting vibration, the construction stagger distance of the secondary linings of the preceding tunnel and the subsequent tunnel is reasonably determined, the construction speed is accelerated, and the construction efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural design schematic diagram of the construction plan for the connected-arch tunnel.

[0020] Figure 2 It is a construction schematic diagram of the upper bench and initial support of the preceding tunnel.

[0021] Figure 3 It is a construction schematic diagram of the right side of the lower bench and the vibration isolation box of the preceding tunnel.

[0022] Figure 4 It is a construction schematic diagram of the initial support on the right side of the lower bench of the preceding tunnel.

[0023] Figure 5 It is a construction schematic diagram of the left side of the lower bench, initial support and inverted arch of the preceding tunnel.

[0024] Figure 6 It is a construction schematic diagram of the vibration isolation holes in the rear tunnel, the upper half of the pilot tunnel, and the initial support.

[0025] Figure 7 It is a construction schematic diagram of the left pilot tunnel in the lower bench, cavity filling, and initial support.

[0026] Figure 8 It is a structural schematic diagram of the vibration isolation box.

[0027] Figure 9 It is a construction schematic diagram of the right side of the upper bench and the initial support.

[0028] Figure 10 It is a construction schematic diagram of the right side of the lower bench, initial support, and inverted arch.

[0029] Figure 11 It is a construction schematic diagram of the secondary lining of the advanced tunnel.

[0030] Figure 12 It is a construction schematic diagram of the secondary lining of the rear tunnel.

[0031] Figure 13 It is a final construction schematic diagram of the twin-arch tunnel.

[0032] In the figure, 1. Upper bench of the advanced tunnel; 2. Cavity; 3. Left side of the lower bench of the advanced tunnel; 4. Curved pilot tunnel of the upper bench of the rear tunnel; 5. Left side of the lower bench of the rear tunnel; 6. Right side of the upper bench of the rear tunnel; 7. Right side of the lower bench of the rear tunnel; 8. Initial support of the arch part of the upper bench of the advanced tunnel; 9. Initial support of the side wall on the right side of the lower bench of the advanced tunnel; 10. Initial support of the left side of the lower bench of the advanced tunnel; 11. Initial support of the inverted arch of the advanced tunnel; 12. Initial support of the arch part of the upper pilot tunnel of the rear tunnel; 13. Initial support of the side wall on the left side of the lower bench of the rear tunnel; 14. Initial support of the right side of the upper bench of the rear tunnel; 15. Initial support of the side wall on the right side of the lower bench of the rear tunnel; 16. Initial support of the inverted arch of the rear tunnel; 17. Secondary lining of the advanced tunnel; 18. Secondary lining of the rear tunnel. Specific implementation mode

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] As Figure 1 、 13 shown, the present invention provides a construction method for a twin-arch tunnel applicable to surrounding rock of grade IV or above, including the following steps: As Figure 2As shown, in step (1), the advanced support of the pilot tunnel is constructed, and the upper bench 1 of the pilot tunnel is excavated. The initial support 8 of the arch part of the upper bench of the pilot tunnel is constructed in a timely manner. In this step, when the surrounding rock grade is level IV, the advanced support is set. Specifically, the advanced small pipes are arranged circumferentially. The length of the advanced small pipes is preferably 3 - 5 m, the circumferential spacing is 40 cm, and the range of the external insertion angle is 5 - 12°.

[0035] When the surrounding rock grade is above level IV, no advanced support is set; When the surrounding rock grade is level IV, the initial support first sets the steel arch frame and then sprays concrete; When the surrounding rock grade is above level IV, the initial support only needs to spray concrete.

[0036] As Figure 3 、 8 shown, in step (2), the right side of the lower bench of the pilot tunnel is excavated, and a cavity 2 is reserved on the right side of the pilot tunnel. A vibration isolation box is set at the reserved cavity 2 as the upper surrounding rock support device. In this step, it is preferred to use the cut method to reserve the cavity 2 on the right side of the pilot tunnel. After the cavity 2 is reserved by cutting, I-beams are used for support. Foaming materials are filled between the I-beams and the top surrounding rock to ensure close contact between the steel frame and the surrounding rock, which can avoid the instability of the surrounding rock caused by local cutting. A vibration isolation box is set at the cavity position. A steel plate is welded on the left side of the vibration isolation box, and the left side gap of the vibration isolation box is filled with foaming materials, and then the covering steel plate is welded to form a composite structure. The right side gap is not filled as the reserved vibration isolation cavity. After the top surrounding rock of the vibration isolation box is leveled, it is filled with foaming materials to make the top of the vibration isolation box close to the surrounding rock. The foaming material is preferably polyurethane foaming material. This construction method can effectively reduce the influence of the blasting construction of the subsequent tunnel on the support structure of the pilot tunnel.

[0037] As Figure 4 shown, in step (3), the initial support 9 of the right side wall of the lower bench of the pilot tunnel is constructed.

[0038] As Figure 5 shown, in step (4), the left side 3 of the lower bench of the pilot tunnel is excavated, and the initial support 10 of the left side of the lower bench of the pilot tunnel is constructed, and the initial support 11 of the inverted arch of the pilot tunnel is poured.

[0039] In the above steps (1) - (4), the pilot tunnel construction adopts the upper and lower bench method. The excavation stagger distance between the upper bench and the lower bench is not more than 15 m. The left and right sides of the lower bench are excavated staggeredly, and the stagger distance should be 3 - 5 m. The initial support closely follows the excavation face. Smooth blasting is used for blasting to protect the surrounding rock. The charge amount is strictly controlled, deep hole blasting is prohibited, and the overbreak and underbreak are strictly controlled. The subsequent tunnel construction excavation adopts the arc excavation short bench method. The depth of the vibration isolation holes does not exceed the length of the advanced support. The excavation footage of the upper drift is not more than 3 m, the excavation footage of the lower bench is not more than 3 m, the excavation stagger distance between the upper and lower benches is not more than 15 m, and the excavation stagger distance between the left and right sides of the upper bench is not more than 10 m.

[0040] AsFigure 6 As shown, in step (5), advanced support is carried out for the subsequent tunnel. Vibration isolation holes are set inside the perimeter holes on the left side of the upper bench of the subsequent tunnel. After excavation, the arched pilot tunnel 4 of the upper bench of the subsequent tunnel is excavated and the initial support 12 of the arch of the upper pilot tunnel of the subsequent tunnel is constructed. In this step, the aperture and arrangement spacing of the circumferential vibration isolation holes are determined according to the surrounding rock conditions, and the layout range is 45 - 60° inside the perimeter holes on the left side of the upper bench. It is preferred to arrange double rows of vibration isolation holes when the surrounding rock grade is grade Ⅳ, and single rows of vibration isolation holes when it is above grade Ⅳ. The aperture of the vibration isolation holes is preferably 108 mm, the hole depth is preferably ≤ 5 m, and the circumferential hole spacing is preferably in the range of 30 - 40 cm.

[0041] As Figure 7 shown, in step (6), the left side 5 of the lower bench of the subsequent tunnel is excavated. The right cavity of the vibration isolation box in step (2) is filled with foaming material, and the initial support 13 of the left side wall of the lower bench of the subsequent tunnel is constructed. In this step, the left side 5 of the lower bench of the subsequent tunnel is relatively close to the preceding tunnel. Smooth surface millisecond blasting is used during excavation, the smallest possible charge amount is selected, low-power and low detonation velocity explosives are used. After construction, the right reserved cavity of the vibration isolation box is filled with foaming material, and the initial support on the left side of the lower bench is constructed in a timely manner.

[0042] As Figure 9 shown, in step (7), the right side 6 of the upper bench of the subsequent tunnel is excavated; and the initial support 14 of the right side of the upper bench of the subsequent tunnel is constructed.

[0043] As Figure 10 shown, in step (8), the right side 7 of the lower bench of the subsequent tunnel is excavated, and the initial support 15 of the right side wall of the lower bench of the subsequent tunnel is constructed, and the initial support 16 of the inverted arch of the subsequent tunnel is poured.

[0044] In the above steps (5) - (8), the following controlled blasting measures are adopted for the subsequent tunnel to effectively control the impact of the blasting construction of the subsequent tunnel on the preceding tunnel.

[0045] (1) Smooth surface millisecond blasting is used for the excavation of the subsequent tunnel. The smallest possible maximum single-shot charge amount is selected, and low-power and low detonation velocity explosives are used.

[0046] (2) Vibration isolation holes are set inside the perimeter holes within the range of 45 - 60° on the left side of the upper bench of the subsequent tunnel. The spacing of the vibration isolation holes is 30 - 40 cm, the aperture is 108 mm, and the hole depth is not more than 5.0 m. The excavation and pouring length of the inverted arch at one time is not more than 3 m. The secondary lining of the inverted arch and the filling of the inverted arch should be poured in one go for the entire cross-section respectively. It is strictly prohibited to construct in left and right subsections, and it is also prohibited to construct the inverted arch and the filling of the inverted arch simultaneously.

[0047] (3) When constructing the arc-shaped guide pit on the upper step of the rear tunnel, a row of vibration isolation holes is pre-set, and the upper step section is divided into two parts. When constructing the lower step, the left side is constructed first and covered with thin steel plates and filled with polyurethane foam fillers in time, which reduces the amount of blasting charges per cycle of excavation of the rear tunnel and forms a ring-shaped excavation cavity, which can reduce the impact of blasting construction on the leading tunnel and avoid the initial support cracking and steel arch deformation of the leading tunnel.

[0048] (4) The distance from the back tunnel face to the front tunnel face is determined by blasting vibration velocity monitoring to ensure that the initial support vibration velocity of the front tunnel is no more than 10 cm / s when the back tunnel is blasted. In order to avoid the impact of the back tunnel construction on the cast secondary lining of the front tunnel, the distance from the back tunnel face to the secondary lining of the front tunnel is determined by blasting vibration velocity monitoring to ensure that the vibration velocity of the cast secondary lining is no more than 5 cm / s when the back tunnel is blasted. The distance from the secondary lining of the back tunnel to the secondary lining of the front tunnel is no more than 60m. The specific construction procedures are shown in the comments. Figure 13 .

[0049] like Figure 11 As shown, step (9) determines the pouring time of the secondary lining of the pilot tunnel by monitoring and measuring the vibration velocity, pours the secondary lining 17 of the pilot tunnel, and the pilot tunnel is penetrated. The vibration velocity is measured by blasting monitoring. During the vibration velocity monitoring, the velocity sensor is fixed on the secondary lining of the pilot tunnel to monitor the vibration velocity at the location with the larger vibration velocity of the tunnel (the spandrel, arch waist, and arch foot position close to the side of the rear tunnel). The number of measuring points is not less than 4, and the test frequency is one blast and one measurement.

[0050] like Figure 12 As shown, in step (10), after the first tunnel is penetrated, the second lining 18 of the second tunnel is poured, and the second tunnel is penetrated, and the construction is completed. In this step, the second lining of the second tunnel and the second lining of the first tunnel need to be poured and constructed at different times.

[0051] The above are only preferred specific implementations of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and improved concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A construction method for a multi-arch tunnel suitable for surrounding rock of grade IV or above, characterized in that: The steps include: Step (1), carry out advance support for the pilot tunnel, excavate the upper step of the pilot tunnel, and promptly carry out initial support for the arch of the upper step; Step (2), excavating the right side of the lower step of the pilot tunnel, and expanding the cavity on the right side of the pilot tunnel, setting a vibration isolation box at the cavity as an upper surrounding rock support device, and filling the left side of the vibration isolation box with foam material; Step (3), provide initial support for the right side wall of the step below the pilot tunnel; Step (4), excavating the left side of the lower step of the pilot tunnel, constructing the initial support for the left side of the lower step, and casting the initial support for the invert arch; Step (5), perform advance support for the rear tunnel, set a vibration isolation hole on the inner side of the blasting hole around the left side of the upper step, excavate an arc-shaped pilot pit on the upper step of the rear tunnel, and perform initial support for the arch of the upper pilot pit; Step (6), after excavation, on the left side of the lower step of the tunnel, use foam material to fill the cavity on the right side of the vibration isolation box in step (2), and perform initial support on the left side wall of the lower step; Step (7), after excavation, go to the right side of the upper step; and carry out initial support on the right side of the upper step; Step (8), excavate the right side of the lower step of the tunnel, and provide initial support for the right side wall of the lower step, and cast the initial support for the invert arch; Step (9), determining the pouring time of the secondary lining of the pilot hole by monitoring and measuring the blasting vibration velocity, pouring the secondary lining of the pilot hole, and penetrating the pilot hole; Step (10): After the first tunnel is penetrated, the secondary lining of the rear tunnel is poured, and the rear tunnel is penetrated, and the construction is completed.

2. A method for constructing a multi-arch tunnel suitable for surrounding rock of grade IV or above according to claim 1, characterized in that: In step (1), when the surrounding rock grade is Grade IV, advance support is set, specifically: advance support is arranged in an annular direction; When the surrounding rock grade is above Grade IV, no advance support shall be provided; When the surrounding rock grade is IV, the initial support is to set up steel arches first and then spray concrete; When the surrounding rock grade is above Grade IV, initial support only requires shotcrete.

3. The method for constructing a multi-arch tunnel suitable for surrounding rock of Grade IV or above according to claim 2, characterized in that: The length of the advance small catheter is 3~5m, the circumferential spacing is 40cm, and the external insertion angle range is 5~12°.

4. The method for constructing a multi-arch tunnel suitable for surrounding rock of grade IV or above according to claim 1, characterized in that: In step (2), a cavity is excavated on the right side of the pilot tunnel by using a grooving method. After the cavity is excavated and expanded, a vibration isolation box is set. A steel plate is welded on the left side of the vibration isolation box. The left gap is filled with foam material. The right gap is not filled as a reserved vibration isolation cavity. After the surrounding rock on the top of the vibration isolation box is leveled, the foam material is used to fill it so that the top of the vibration isolation box is in close contact with the surrounding rock.

5. The method for constructing a multi-arch tunnel suitable for surrounding rock of Grade IV or above according to claim 1, characterized in that: In step (5), the diameter and arrangement spacing of the circumferential vibration isolation holes are determined according to the surrounding rock conditions, and the arrangement range is 45~60° inside the peripheral eye on the left side of the upper step.

6. A method for constructing a multi-arch tunnel suitable for surrounding rock of grade IV or above according to claim 5, characterized in that: When the surrounding rock grade is Grade IV, double rows of vibration isolation holes are arranged; when it is Grade IV or above, single row of vibration isolation holes are arranged.

7. The method for constructing a multi-arch tunnel suitable for surrounding rock of Grade IV or above according to claim 5, characterized in that: The diameter of the vibration isolation hole is 108mm, the hole depth is ≤5m, and the circumferential spacing of the holes is 30~40cm.

8. The method for constructing a multi-arch tunnel suitable for surrounding rock of Grade IV or above according to claim 1, characterized in that: In step (6), the left side of the lower step of the rear tunnel is closer to the advance tunnel. During excavation, smooth micro-difference blasting is used, the smallest possible charge amount and low detonation velocity explosives are used. After construction, the reserved cavity on the right side of the vibration isolation box is filled with foam material, and initial support is provided on the left side of the lower step in a timely manner.

9. The method for constructing a multi-arch tunnel suitable for surrounding rock of Grade IV or above according to claim 1, characterized in that: In step (9), blasting vibration monitoring and measurement are carried out. The velocity sensor is fixed on the secondary lining of the pilot hole, generally arranged on the blasting surface, with no less than 4 measuring points, and the test frequency is one blast and one measurement.

10. A method for constructing a multi-arch tunnel suitable for surrounding rock of grade IV or above according to any one of claims 1 to 9, characterized in that: In step (10), the secondary lining of the rear tunnel and the secondary lining of the front tunnel need to be cast at different times.

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