A rapid transition construction method for variable-section and large-span tunnels

Abstract

The present invention relates to the field of tunnel construction technology, and more particularly to a method for rapidly transitioning a two-lane or three-lane tunnel of normal span into an extra-large span tunnel. The method involves accessing the extra-large cross-section tunnel via a step in the two-lane or three-lane tunnel, then excavating the extra-large cross-section tunnel via a transverse tunnel. This method enables a rapid and safe transition from a small cross-section tunnel to a large cross-section tunnel using a double-wall construction method. The present invention ensures orderly and controllable construction while ensuring safety, achieving the goal of rapidly transitioning from a small cross-section tunnel to a large cross-section tunnel. This method ensures construction schedules are met, facilitates process transitions, reduces labor intensity, improves construction efficiency, and reduces costs.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, in particular to a method for rapid transition construction of a variable-section large-span tunnel, and in particular to a method for rapid transition construction of a two-lane or three-lane normal-span tunnel into an ultra-large-span tunnel. Background Art

[0002] With the advancement of urbanization in my country, tunnel construction has entered a new era of rapid development. Due to factors such as the constraints of surrounding terrain and foundation structures, as well as the need to connect to and cross existing roads, urban mountain tunnels are designed with continuously variable cross-sections. For example, shallow, narrow-spacing tunnels transition to continuous arches, and then to continuous arches that transition to larger cross-sections. These tunnels present variations in cross-section clearance and stress concentration at the cross-section transitions. Improper construction control can easily lead to tunnel instability hazards such as landslides. Furthermore, excavation from small-section tunnels to larger cross-sections is difficult and complex, involving multiple conversions between construction methods. This results in low construction efficiency and extremely high safety and quality risks. Several construction techniques for transitioning from a small-section to a large-section tunnel are currently available. One approach involves excavating the tunnel from a small section to a large section in a bell-shaped, sloped pattern 5 to 15 meters before entering the large-section tunnel. The bell-shaped section is then filled with concrete. However, this concrete filling increases project costs and significantly disturbs the surrounding rock. Another approach involves excavating the tunnel again in a bell-shaped, sloped pattern after entering the large-section tunnel, then returning to the climb section for excavation. However, excavating the climb section of the tunnel is prone to significant vault strata instability, inadequate support measures, and collapse, resulting in poor safety and controllability. Therefore, to ensure the safety of continuously variable-section, large-span tunnels, it is necessary to rationally arrange the construction sequence and develop a rapid transition construction method suitable for these tunnels. Summary of the Invention

[0003] In response to the problems of traditional tunnel excavation methods for continuously variable cross-section and large-span tunnels, such as many safety hazards, great construction difficulty and slow construction progress, the present invention proposes a rapid transition construction method for variable cross-section and large-span tunnels, which is suitable for the conversion construction project from the CD method of two-lane lining section to the double-side wall method of five-lane lining section.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows:

[0005] A method for rapid transition construction of a variable-section large-span tunnel comprises the following steps:

[0006] Step 1: Construct a small advance guide tube, excavate the double lane CD method 1, construct temporary vertical support and double lane primary support, and construct a temporary steel frame within 2m before the demarcation mileage;

[0007] Step 2: Construct a small advance guide tube, excavate two sections of the five-lane lining, construct temporary steel frame support for Section II and primary support for the five-lane lining. After ensuring sufficient operating space for construction machinery and safety for cross-channel construction, stop excavating in the forward direction after 5m of longitudinal construction.

[0008] Step 3: Build an advance small duct, excavate three sections horizontally, remove the temporary steel frame support, and build a third section of temporary portal frame support. The portal frame support is welded to the two primary support steel frames. At the same time, reserve operating space for the connection of the steel frame support of the five-lane lining section in the later stage. Add arch locking feet and strengthen construction monitoring.

[0009] Step 4: Construct an advance small guide tube, excavate along the five-lane lining section excavation line and complete the construction of the portal frame support. Construct the initial support steel frame for the five-lane lining within the portal frame range. At this time, the excavation of the upper step of the five-lane lining is completed, and construction monitoring is strengthened;

[0010] Step 5: construct an advance small guide tube, construct four longitudinal excavations on the right upper steps of the double side walls of the five-lane road, and construct the temporary steel frame support and primary support steel frame of Section IV;

[0011] Step 6: After longitudinally excavating 5 to 8 meters of the four sections of the double side walls of the five-lane lining section, longitudinally excavate the five sections of the double side walls of the five-lane section and implement temporary support and primary support for Section V;

[0012] Step 7: After longitudinally excavating 5 to 8 meters of the double-side walls of the five-lane lining section, longitudinally excavate six sections of the five-lane lining section and construct temporary support and primary support steel frames for Section VI;

[0013] Step 8: After longitudinally excavating 5 to 8 meters of the six sections of the double-side walls of the five-lane lining section, longitudinally excavate seven sections of the five-lane lining section and construct temporary support and primary support steel frames for Section VII;

[0014] Step 9: After longitudinally excavating 5 to 8 meters of the double-side walls of the five-lane lining section, longitudinally excavate the eight sections of the five-lane lining section and construct temporary support and primary support steel frames for Section VIII;

[0015] Step 10: After 5 to 8 meters of longitudinal excavation of 8 sections of the double side walls of the five-lane lining section, longitudinal excavation of 9 sections of the five-lane lining section is carried out, and temporary support and primary support steel frame of section VIII are constructed.

[0016] Specifically, the temporary steel frame in step 1 is supported by reinforced support with a spacing of 0.4m.

[0017] Specifically, this construction method is suitable for the conversion construction project from the CD method of a two-lane lining section to the double-side wall method of a five-lane lining section.

[0018] The beneficial effects of the present invention are:

[0019] The present invention enters the upper steps of the pilot pit on one side of the super-large section through the upper steps of a two-lane or three-lane tunnel, and then excavates the pilot pit on the other side of the super-large section by constructing a cross passage, thereby realizing a rapid and safe conversion of the double-side wall construction method from a small-section tunnel to a large-section tunnel. While ensuring safety, the construction can be orderly and controllable, achieving the goal of rapid excavation construction of continuously variable-section large-span tunnels, ensuring the construction schedule, facilitating process conversion, reducing labor intensity, improving construction efficiency, and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of a method for rapid transition construction of a variable-section, large-span tunnel according to an embodiment of the present invention;

[0021] Figure 2 This is a front view of the five-lane double sidewall method according to an embodiment of the present invention;

[0022] Figure 3 This is a plan view of a continuously variable cross-section large-span tunnel according to embodiment 5 of the present invention;

[0023] Figure 4 This is a large sample diagram of node A in an embodiment of the present invention;

[0024] Figure 5 This is a schematic structural diagram of a portal frame according to an embodiment of the present invention;

[0025] Figure 6 Schematic diagram of the relative positions of the portal frame and the primary support steel frame in Example S104 of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] Reference Attachment Figure 1-6 A method for rapid transition construction of a variable-section large-span tunnel comprises the following steps:

[0028] S101: Construct a small advance guide tube, excavate the double lane CD method 1, construct temporary vertical supports and initial support for the double lane, and construct a temporary steel frame to support within 2m before the demarcation mileage.

[0029] Furthermore, the temporary steel frame support involved in the present invention adopts reinforced support with a spacing of 0.4m. During the construction excavation process, the advance support spacing is 0.4m / root, which can avoid the phenomenon of over-excavation and block loss of the arch, and over-excavation can be effectively controlled.

[0030] S102: Construct a small advance guide tube, excavate two sections of the five-lane lining, construct temporary steel frame support for section II and initial support for the five-lane lining section, and stop excavating in the forward direction after 5m of longitudinal construction to ensure the operating space for construction machinery and the safety of cross-channel construction.

[0031] S103: Build an advance small duct, excavate three sections horizontally, remove the temporary steel frame support and build a temporary portal frame support of section III, weld the portal frame support with the two primary support steel frames (see Figure 4 ), and at the same time reserve operating space for the subsequent five-lane lining section steel frame support connection, add arch locking feet, and strengthen construction monitoring.

[0032] S104: Construct an advance small conduit, excavate along the five-lane lining section excavation line and construct and complete the portal frame support (see Figure 5 ), construct the five lane lining primary support steel frame within the scope of the portal frame (see Figure 6 ), at this time, the excavation of the upper steps of the five-lane lining was completed, and construction monitoring was strengthened.

[0033] S105: Construct a small advance guide tube, construct four sections of longitudinal excavation on the right side upper steps of the double side walls of the five-lane road, and construct the temporary steel frame support and primary support steel frame of Section IV.

[0034] In one embodiment, a Φ42 seamless steel pipe with a wall thickness of 4mm and a length of 5m is used to construct the advance small conduit. Before construction, a hoop is welded to the tail of the steel pipe, and the front end is made into a pointed cone. Overflow holes with a diameter of 8mm are drilled on the pipe wall, distributed in a plum blossom shape with a spacing of 15cm. No holes are drilled within 40cm of the leakage end.

[0035] In one of the embodiments, before grouting with a small pipe in advance in the tunnel, the excavation surface and the tunnel within a range of 5m should be sealed by spraying 8 to 10 cm thick concrete, and then a small pipe with holes should be driven into the surrounding rock in front along the periphery of the tunnel, and cement slurry should be injected into the surrounding rock through the small pipe. After the slurry solidifies, a bearing arch will be formed in the surrounding rock above the excavation outline, which will facilitate the next step of construction.

[0036] In one embodiment, the advance small guide tube is set within the 120° range of the arch, with a single length of 5 meters, drilled into the rock mass at an external insertion angle of 10°, with an annular spacing of 20 cm, a longitudinal horizontal overlap of 1 m, a longitudinal spacing of 3 m, and 50 tubes per ring.

[0037] In one embodiment, the small lead pipe is preferably passed through the belly of the steel frame, with the tail end welded to the frame. A pneumatic rock drill is used to drill the hole, with the diameter 3-4 mm larger than the steel pipe. After drilling to the designed depth, the hole is promptly blown with an air pipe to remove any debris and stone dust. The lead pipe is then hammered or drilled into the hole, with the insertion length being no less than 95% of the steel pipe. To prevent slurry backflow, after the small lead pipe is installed, the gap between the grouting pipe and the grouting hole is sealed, and a check valve is installed at the pipe opening.

[0038] In one of the embodiments, a grouting machine is used for grouting, and micro-expansion grouting material is used. The UJOIN-112 micro-expansion grouting material of Wuhan Yuanjin Building Materials Technology Co., Ltd. is purchased. Water is added according to a water-to-material ratio of 0.20, and the grouting pressure is used to control whether the grouting is completed. Among them, the preferred grouting pressure is 0.5-1.0 MPa. When the grouting pressure continues to rise to 2.0 MPa, the grouting is stopped. If the pressure does not drop or the drop is not obvious, the grouting is ended and the check valve is closed. If it quickly drops below 0.5 MPa, the grouting is continued until the grouting pressure meets the design requirements.

[0039] S106: After longitudinal excavation of 5 to 8 m in four sections of double side walls of the five-lane lining section, longitudinal excavation of five sections of double side walls of the five-lane section is carried out, and temporary support and primary support are applied to Section V.

[0040] S107: After longitudinal excavation of 5 to 8 m in 5 sections of the double side walls of the five-lane lining section, longitudinal excavation of 6 sections of the five-lane lining section is carried out, and temporary support and primary support steel frames are installed in section VI.

[0041] S108: After longitudinal excavation of 5 to 8 meters on both sides of the 6 sections of the five-lane lining section, longitudinal excavation of 7 sections of the five-lane lining section is carried out, and temporary support and primary support steel frame of section VII are constructed.

[0042] S109: After longitudinal excavation of 5 to 8 meters on both sides of the 7 sections of the five-lane lining section, longitudinal excavation of 8 sections of the five-lane lining section is carried out, and temporary support and primary support steel frame of Section VIII are constructed.

[0043] S110: After 5 to 8 meters of longitudinal excavation of 8 sections of double side walls of the five-lane lining section, longitudinal excavation of 9 sections of the five-lane lining section is carried out, and temporary support and primary support steel frame of Section VIII are constructed.

[0044] In one of the embodiments, the double-side wall pilot tunnel method adopted by the present invention is a branch of the New Austrian Tunneling Method (NATM), which divides a large section into two symmetrical pilot tunnels and several independent small sections. The pilot tunnel section is approximately elliptical, and the peripheral contour is smooth, which can effectively avoid stress concentration. The tunnel is excavated in sections and batches, reducing the difficulty of excavating the entire section of a large-span tunnel.

[0045] In one of the embodiments, the construction process must be carried out in accordance with the design requirements and the construction principle of the double-side wall pilot tunnel method. The excavation of the soft geological tunnel body should adhere to the principle of "short advance, weak blasting, strong support, early lining, and frequent monitoring", and strengthen the construction monitoring corresponding to the aforementioned steps to ensure construction safety. If the actual surrounding rock level does not match the design data during construction, the construction plan should be adjusted in time to ensure safe and smooth excavation.

[0046] In one embodiment, the arch locking foot is an important measure to ensure the safety of the initial support. The arch foot and the corner position of the section will be subject to greater lateral pressure. At this time, the anchor rods there act as "pull rods" to ensure that the steel frame does not move into the hole when subjected to lateral force, thereby ensuring the stability of the initial support structure during construction.

[0047] In one embodiment, during the tunnel construction process, any voids are strictly prohibited behind the supporting steel frame. On the one hand, this is to control over-excavation and under-excavation. On the other hand, if the back of the steel frame is not tightly attached, it should be filled tightly with concrete pads of the same grade to facilitate the stress bearing of the steel frame.

[0048] In one embodiment, during the tunnel construction process, surrounding rock measurements must be timely and accurate, and real-time data must be obtained through monitoring and measurement. Analysis and feedback are used to adjust design parameters and construction operations.

[0049] The present invention discloses a method for rapid transition construction of a variable-section large-span tunnel, which is not only applicable to the construction project of converting a two-lane lining section using the CD method to a five-lane lining section using the double side wall method, but also applicable to the construction project of converting a two-lane lining section using the CD method to a four-lane and five-lane lining section using the double side wall method, the construction project of converting a two-lane lining section using the CD method to a five-lane lining section using the double side wall method, the construction project of converting a two-lane lining section using the CD method to a five-lane lining section using the double side wall method, and the construction project of converting a four-lane lining section using the CD method or the double side wall method to a five-lane lining section using the double side wall method.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for rapid transition construction of a variable cross-section and large span tunnel, characterized in that: The following steps are involved: Step 1: construct a small advance guide tube, excavate the double lane CD method 1, construct temporary vertical supports and double lane primary support, and construct temporary steel frames within 2m before the demarcation mileage. The temporary steel frames use reinforced support with a spacing of 0.4m; Step 2: Construct a small advance guide tube, excavate two sections of the five-lane lining, construct temporary steel frame support for Section II and primary support for the five-lane lining. After ensuring sufficient operating space for construction machinery and safety for cross-channel construction, stop excavating in the forward direction after 5m of longitudinal construction. Step 3: Build an advance small duct, excavate three sections horizontally, remove the temporary steel frame support, and build a third section of temporary portal frame support. The portal frame support is welded to the two primary support steel frames. At the same time, reserve operating space for the connection of the steel frame support of the five-lane lining section in the later stage. Add arch locking feet and strengthen construction monitoring. Step 4: Construct an advance small guide tube, excavate along the five-lane lining section excavation line and complete the construction of the portal frame support. Construct the initial support steel frame for the five-lane lining within the portal frame range. At this time, the excavation of the upper step of the five-lane lining is completed, and construction monitoring is strengthened; Step 5: construct an advance small guide tube, construct four longitudinal excavations on the right upper steps of the double side walls of the five-lane road, and construct the temporary steel frame support and primary support steel frame of Section IV; Step 6: After longitudinally excavating 5 to 8 meters of the four sections of the double side walls of the five-lane lining section, longitudinally excavate the five sections of the double side walls of the five-lane section and implement temporary support and primary support for Section V; Step 7: After longitudinally excavating 5 to 8 meters of the double-side walls of the five-lane lining section, longitudinally excavate six sections of the five-lane lining section and construct temporary support and primary support steel frames for Section VI; Step 8: After longitudinally excavating 5 to 8 meters of the six sections of the double-side walls of the five-lane lining section, longitudinally excavate seven sections of the five-lane lining section and construct temporary support and primary support steel frames for Section VII; Step 9: After longitudinally excavating 5 to 8 meters of the double-side walls of the five-lane lining section, longitudinally excavate the eight sections of the five-lane lining section and construct temporary support and primary support steel frames for Section VIII; Step 10: After 5 to 8 meters of longitudinal excavation of 8 sections of the double side walls of the five-lane lining section, longitudinal excavation of 9 sections of the five-lane lining section is carried out, and temporary support and primary support steel frame of section VIII are constructed.

2. A variable cross-section large span tunnel rapid transition construction method according to claim 1, characterized in that: This construction method is suitable for the conversion construction project from the CD method of two-lane lining section to the double-side wall method of five-lane lining section.

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