Small short-distance tunnel section single-side expanding excavation construction method

Abstract

The invention relates to a small-short-distance tunnel section single-side expanding excavation construction method. The method comprises the following steps that S1, a first anchor rod is placed in a middle rock wall; s2, a pre-stressed anchor cable is arranged on the arch portion, close to one side of the middle rock wall, of the tunnel; s3, pre-tightening force is applied to the first anchor rod; s4, a temporary lining is arranged in the tunnel; s5, the expanding excavation side is broken; s6, expanding excavation is conducted on the expanding excavation side; s7, a second anchor rod is arranged at the arch shoulder, close to the middle rock wall, of the tunnel; s8, advance supporting and primary supporting are conducted on the expanding excavation part; s9, inverted arch construction is conducted; and S10, the temporary lining is dismantled, and secondary lining pouring construction is conducted. The method has the advantages that the problem that the traffic volume of an existing single-lane highway tunnel is insufficient is solved, the vehicle passing efficiency is improved, surrounding rock and existing lining of the tunnel are reinforced in the construction process, the stability of the whole structure is guaranteed, the expanding excavation construction process is safe and reliable, the construction efficiency is guaranteed, and the method has high popularization value in the field of tunnel construction.

Description

Technical Field

[0001] The invention relates to the field of tunnel engineering, and in particular to a single-side excavation construction method for a small and close-distance tunnel section. Background Art

[0002] With the rapid development of my country's transportation construction in recent years, the conventional highway tunnels built in the early days are relatively old and can no longer meet the growing demand for highway transportation volume. When underground space or crossing channel space is limited, expanding existing tunnels is a relatively economical and effective method.

[0003] There are three main methods for tunnel expansion: single-side expansion, surrounding expansion, and double-side expansion. Due to the particularity of existing short-distance tunnels, the risk of surrounding expansion is extremely high. Double-side expansion makes the net distance close to the other tunnel smaller or there is no space to dig, so only single-side expansion can be used. However, due to the asymmetry of the expansion construction, single-side expansion will cause stress concentration on the other side of the expanded tunnel, which may cause the structure or surrounding rock to become unstable, resulting in irreparable economic losses.

[0004] Therefore, in order to solve the problem of expanding small and close-distance tunnels and to expand their capacity and make them smoother, a single-side expansion construction method for small and close-distance tunnel sections is urgently needed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a construction method for single-side excavation of a small and close-spaced tunnel section. The technical solution of the present invention to solve the above technical problems is as follows: A single-side excavation construction method for a small and close-spaced tunnel section comprises the following steps: S1, setting out anchor hole positions on the middle rock wall, putting an appropriate amount of cement rolls in the holes after drilling and inserting a first anchor, wherein the first anchor penetrates the middle rock wall; S2. Prestressed anchor cables are installed in the tunnel arch near the middle rock wall; S3, after the first anchor rod penetrates the middle rock wall, applying a pre-tightening force to the first anchor rod, and sequentially installing a grout stopper, a pad and a nut required for anchoring; S4. Install a temporary lining on the inner wall of the tunnel; S5. After all temporary linings of the tunnel are completed, the existing invert, secondary lining and primary support on the expansion side are demolished with the tunnel centerline as the boundary; S6. Carry out excavation construction on the excavation side; S7, after the excavation is completed, a second anchor rod is set at the spandrel of the tunnel close to the middle rock wall, a pre-tightening force is applied to the second anchor rod, and a grout stopper, a pad and a nut required for anchoring are installed in sequence; S8. Carry out advance support and initial support for the expanded excavation part; S9, construct an invert on the expanded excavation part; S10. Remove the temporary lining and carry out secondary lining pouring construction on the expanded excavation part.

[0006] The beneficial effects of the present invention are: firstly, prestressed anchor cables are applied on the non-expanded side to anchor the lining and surrounding rock, then the first anchor rod is applied at the middle rock wall for tensioning, thereby increasing the horizontal stress and the bearing capacity of the surrounding rock, then weak blasting is performed in conjunction with manual mechanical unilateral excavation, and then the second anchor rod is applied at the spandrel, and finally the sprayed anchor support is completed. This method not only effectively solves the problem of insufficient transportation capacity in existing single-lane highway tunnels and improves the efficiency of vehicle traffic, but also strengthens the surrounding rock and existing lining of the tunnel during the construction process, ensures the stability of the overall structure, makes the expansion and excavation construction process safe and reliable, and ensures the construction efficiency, and has a high promotion value in the field of tunnel construction.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, in step S1, a drilling rig is used to drill a first hole on one side of the middle rock wall and remove the debris in the hole. After the first anchor rod is placed in the hole, the drilling rig drills a second hole on the other side of the middle rock wall to ensure that the first anchor rod penetrates the entire middle rock wall.

[0009] The beneficial effect of adopting the above further solution is: using the first anchor rod to anchor both sides of the middle rock wall, thereby improving the stability and bearing capacity of the surrounding rock.

[0010] Furthermore, in step S2, the prestress of the prestressed anchor cable is set to 200-500 kN depending on the surrounding rock and the burial depth. The prestress should be applied in two steps. During the initial application, the prestress is set to 30% of the total prestress, and then applied to 100% after the existing secondary lining and the existing primary support are broken.

[0011] The beneficial effect of adopting the above further solution is: using prestressed anchor cables to anchor the surrounding rock and lining, and adjusting the preload force in accordance with the construction progress to achieve the best anchoring effect.

[0012] Furthermore, in step S3 and step S7, when a pre-tightening force is applied to the first anchor rod and the second anchor rod, a pre-tightening force of 60 kN to 100 kN should be applied.

[0013] The beneficial effect of adopting the above further solution is: pre-tightening is performed in combination with the actual situation of the surrounding rock.

[0014] Furthermore, in step S5, the demolition method of a breaker hammer and weak blasting is used to demolish the tunnel expansion side, and the demolition sequence is from the tunnel arch crown to the arch waists on both sides from top to bottom.

[0015] The beneficial effect of adopting the above further scheme is: breaking from top to bottom, reducing the impact on the non-expanded side of the tunnel, and avoiding imbalance of the surrounding rock.

[0016] Furthermore, in step S6, the excavation is expanded by using weak blasting combined with manual mechanical excavation, and the excavation depth is determined according to the stability of the surrounding rock and structure, and is controlled at 0.8-1.0 m per time.

[0017] The beneficial effect of adopting the above further scheme is: the excavation progress is controlled within a certain range to prevent the surrounding rock from collapsing.

[0018] Further, in step S8, the advance support adopts pipe-roof support; Initial support: First, install the steel arch frame on the expansion side, then install grouting anchor rods and locking anchor rods on the inner wall of the expansion side according to the design requirements, and finally install the steel mesh and spray concrete.

[0019] The beneficial effect of adopting the above further scheme is that the advance support and the initial support are used to stabilize the surrounding rock after the expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a single-side tunnel excavation of the present invention; Figure 2 It is a schematic diagram of the middle rock wall of the present invention; Figure 3 It is a schematic diagram of the excavation step of the present invention; Figure 4 It is a schematic diagram of a temporary lining of the present invention.

[0021] In the accompanying drawings, the components represented by the reference numerals are listed as follows: 1. Middle rock wall; 2. First anchor rod; 3. Prestressed anchor cable; 4. Temporary lining; 5. Existing invert; 6. Existing secondary lining; 7. Existing primary support; 8. Second anchor rod; 9. Grouting anchor rod; 10. Locking foot anchor rod; 11. Horizontal brace; 12. Vertical brace. DETAILED DESCRIPTION

[0022] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0023] Example 1 like Figures 1 to 4 As shown, a single-side excavation construction method for a small and close-spaced tunnel section comprises the following steps: S1, setting out anchor hole positions on the middle rock wall 1, putting an appropriate amount of cement rolls in the holes after drilling and inserting the first anchor rod 2, wherein the first anchor rod 2 penetrates the middle rock wall 1; S2, setting a prestressed anchor cable 3 at the tunnel arch near the middle rock wall 1; S3, after the first anchor rod 2 penetrates the middle rock wall 1, a pre-tightening force is applied to the first anchor rod 2, and a grout stopper, a pad and a nut required for anchoring are installed in sequence; S4, setting a temporary lining 4 on the inner wall of the tunnel; S5. After all temporary linings 4 of the tunnel are constructed, the existing invert 5, the existing secondary lining 6 and the existing primary support 7 on the expansion side are removed with the tunnel centerline as the boundary; S6. Carry out excavation construction on the excavation side; S7, after the excavation is completed, a second anchor rod 8 is arranged at the spandrel of the tunnel close to the middle rock wall 1, a pre-tightening force is applied to the second anchor rod 8, and a grout stopper, a pad and a nut required for anchoring are installed in sequence; S8. Carry out advance support and initial support for the expanded excavation part; S9, construct an invert on the expanded excavation part; S10, remove the temporary lining 4, and perform secondary lining pouring construction on the expanded excavation part.

[0024] In this embodiment, the middle rock wall 1 refers to the middle partition wall between two parallel tunnels, and the short-distance tunnel refers to a tunnel whose thickness of the middle rock wall 1 is less than the minimum clear distance of the separated independent double tunnels.

[0025] Among them, layout refers to the surveying work of measuring the plane position and elevation of the engineering construction features on the design drawings on the spot using certain surveying instruments and methods.

[0026] Among them, cement roll is a bonding material for anchoring, mainly used in coal mines and tunnel support. It is usually made of cement and put into a special bag to form a cylindrical shape with a diameter similar to the drilled hole so that it can be smoothly inserted into the hole.

[0027] Among them, the inverted arch refers to the reverse arch structure set at the bottom of the tunnel to improve the stress conditions of the upper supporting structure of the tunnel.

[0028] Specifically, the left and right tunnels are constructed symmetrically, with the central axis of the left or right tunnel as the reference, the side away from the middle rock wall 1 is the expansion side, and the side close to the middle rock wall 1 is the non-expansion side, and the tunnel profile radius of the non-expansion side is not changed; First, prestressed anchor cables 3 are installed on the non-expanded side to anchor the lining and surrounding rock, and then the first anchor rod 2 is installed at the middle rock wall 1 for tensioning. The first anchor rod 2 penetrates the middle rock wall 1, and both ends extend into two parallel tunnels, and then a temporary lining 4 is installed; Then, the existing invert 5, the existing secondary lining 6 and the existing primary support 7 are removed, weak blasting is used in conjunction with manual mechanical unilateral excavation, and then the second anchor 8 is applied at the spandrel, and then advanced support and initial support are carried out, and finally the sprayed anchor support is completed; After the initial support of the expanded excavation part reaches the design strength, the temporary lining 4 is removed and the secondary lining pouring construction is carried out. The secondary lining pouring construction includes: laying of waterproof board, binding of secondary lining steel bars, and construction of cast secondary lining concrete.

[0029] Among them, the invert construction needs to follow the initial support closely, so that the internal structure of the tunnel can be closed into a ring in time to ensure the force balance of the tunnel surrounding rock. The invert construction includes invert filling and invert, and the invert filling and invert are constructed separately.

[0030] Invert filling: After the invert construction is completed, the arc structure at the bottom of the tunnel is cast as a whole on the same plane to facilitate traffic and subsequent track laying.

[0031] On the basis of this embodiment, the temporary lining 4 includes an annular steel frame, a horizontal brace 11 and a vertical brace 12 that fits the inner circumference of the tunnel. The annular steel frame is erected at the bottom of the left and right ditches, and is connected to the secondary lining concrete with expansion bolts to form an integral force-bearing structure of the temporary lining 4. The horizontal brace 11 is overlapped on the vertical brace 12, and the ends on both sides are connected to the annular steel frame by locking buckles.

[0032] This method not only effectively solves the problem of insufficient capacity in existing single-lane highway tunnels and improves the efficiency of vehicle traffic, but also reinforces the surrounding rock and existing tunnel lining during the construction process, ensuring the stability of the overall structure, making the expansion and excavation process safe and reliable, and ensuring construction efficiency. It has a high promotion value in the field of tunnel construction.

[0033] Example 2 like Figures 1 to 4 As shown, preferably, on the basis of Example 1, in the step S1, a drilling rig is used to perform the first drilling on one side of the middle rock wall 1 and remove the gravel in the hole, a proper amount of cement roll is placed in the hole, and the first anchor rod 2 is placed in the hole until the first anchor rod 2 has a remaining distance of 0.2 to 0.3 m from penetrating the entire middle rock wall 1; then the drilling rig performs the second drilling on the other side of the middle rock wall 1 to ensure that the first anchor rod 2 penetrates the entire middle rock wall 1.

[0034] Preferably, in step S2, the length of the prestressed anchor cable 3 is 15-20m, and the prestress of the prestressed anchor cable 3 is set to 200-500kN depending on the surrounding rock and the burial depth. The prestress should be applied in two steps. During the initial application, the prestress is set to 30% of the total prestress, and then applied to 100% after the existing secondary lining 6 and the existing primary support 7 are broken.

[0035] Preferably, in step S3 and step S7, when a pre-tightening force is applied to the first anchor rod 2 and the second anchor rod 8, a pre-tightening force of 60 kN to 100 kN should be applied.

[0036] Preferably, in step S5, the tunnel expansion side is demolished by using a demolition hammer and weak blasting, and the demolition sequence is from the tunnel arch to the arch waists on both sides from top to bottom.

[0037] Preferably, in step S6, the excavation is carried out by weak blasting in combination with manual mechanical excavation, and the excavation depth is determined according to the stability of the surrounding rock and the structure, and is controlled at 0.8-1.0 m at a time.

[0038] Preferably, in step S8, the advance support adopts pipe-roof support; Initial support: First, install the steel arch frame on the expansion side, then install the grouting anchor rods 9 and the locking anchor rods 10 on the inner wall of the expansion side according to the design requirements, and finally install the steel mesh and spray concrete.

[0039] In this embodiment, advance support refers to an auxiliary measure taken ahead of the excavation of the tunnel face to ensure the stability of the excavation working face of the tunnel project, including pipe sheds, small guide tubes, horizontal jet grouting piles, etc. Pipe-roof support refers to a pre-support method in which thick-walled steel pipes are driven into the perimeter of the upper section of the excavation working face before excavation proceeds, and excavation is carried out under the protection of a temporary bearing shed constructed in the stratum.

[0040] Among them, initial support refers to the support implemented in time after tunnel excavation to control surrounding rock deformation and prevent collapse; Steel arch frame is a support measure that uses steel to reinforce underground projects. It bends the steel into an arch structure to support and protect the underground space and prevent deformation and collapse of the surrounding rock. The steel arch frame laid in the tunnel is connected to the original lining steel arch frame by welding.

[0041] Specifically, the demolition of the tunnel expansion part is carried out by mechanical demolition with a breaker hammer and weak blasting. The demolition sequence is from the tunnel arch crown to the arch waists on both sides from top to bottom. First, the existing secondary lining 6 is demolished, then the existing primary support 7 is demolished, and finally the existing invert 5 is demolished. The demolition interval is based on the distance of 1 steel frame each time (1 frame refers to a structural unit of the connected beam or truss).

[0042] When expanding, Figure 4 As shown, the expansion excavation adopts the step-by-step excavation method, and the excavation sequence is: ①→②→③→④; over-excavation is controlled within 10cm, and under-excavation is strictly prohibited.

[0043] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0044] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0045] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0047] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0048] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A single-side excavation construction method for a small and close-spaced tunnel section, characterized in that: The following steps are involved: S1, setting out anchor hole positions on the middle rock wall, putting an appropriate amount of cement rolls in the holes after drilling and inserting a first anchor, wherein the first anchor penetrates the middle rock wall; S2. Prestressed anchor cables are installed in the tunnel arch near the middle rock wall; S3, after the first anchor rod penetrates the middle rock wall, applying a pre-tightening force to the first anchor rod, and sequentially installing a grout stopper, a pad and a nut required for anchoring; S4. Install a temporary lining on the inner wall of the tunnel; S5. After all temporary linings of the tunnel are completed, the existing invert, secondary lining and primary support on the expansion side are demolished with the tunnel centerline as the boundary; S6. Carry out excavation construction on the excavation side; S7, after the excavation is completed, a second anchor rod is set at the spandrel of the tunnel close to the middle rock wall, a pre-tightening force is applied to the second anchor rod, and a grout stopper, a pad and a nut required for anchoring are installed in sequence; S8. Carry out advance support and initial support for the expanded excavation part; S9, construct an invert on the expanded excavation part; S10. Remove the temporary lining and carry out secondary lining pouring construction on the expanded excavation part.

2. According to claim 1, a single-side excavation construction method for a small and close-spaced tunnel section is characterized in that: In step S1, a drilling rig is used to drill a hole on one side of the middle rock wall for the first time and remove the debris in the hole. After the first anchor rod is placed in the hole, the drilling rig is used to drill a second hole on the other side of the middle rock wall to ensure that the first anchor rod penetrates the entire middle rock wall.

3. According to claim 2, a single-side excavation construction method for a small and close-spaced tunnel section is characterized in that: In step S2, the prestress of the prestressed anchor cable is set to 200-500 kN depending on the surrounding rock and the burial depth. The prestress should be applied in two steps. During the initial application, the prestress is set to 30% of the total prestress, and then applied to 100% after the existing secondary lining and the existing primary support are broken.

4. According to claim 3, a single-side excavation construction method for a small and close-spaced tunnel section is characterized in that: In step S3 and step S7, when a pre-tightening force is applied to the first anchor rod and the second anchor rod, a pre-tightening force of 60 kN to 100 kN should be applied.

5. According to claim 4, a single-side excavation construction method for a small and close-spaced tunnel section is characterized in that: In step S5, the tunnel expansion side is demolished by using a demolition hammer and weak blasting, and the demolition sequence is from the tunnel vault to the arch waists on both sides from top to bottom.

6. According to claim 5, a single-side excavation construction method for a small and close-spaced tunnel section is characterized in that: In step S6, the excavation is carried out by using weak blasting combined with manual mechanical excavation, and the excavation depth is determined according to the stability of the surrounding rock and structure, and is controlled at 0.8-1.0 m per time.

7. The method for single-side excavation of a small and close-spaced tunnel section according to claim 6 is characterized in that: In step S8, the advance support adopts pipe-roof support; Initial support: First, install the steel arch frame on the expansion side, then install grouting anchor rods and locking anchor rods on the inner wall of the expansion side according to the design requirements, and finally install the steel mesh and spray concrete.

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