Methods for excavation and support of tunnels in strongly weathered mudstone

Abstract

This invention provides a method for excavating and supporting a tunnel in highly weathered mudstone, comprising the following steps: excavating a lower excavation section along the inner wall of a pre-designed tunnel cross-section; installing ground connecting beams and lower section support; excavating a middle excavation section along the inner wall of the pre-designed tunnel cross-section; installing middle section support above the lower section support; excavating a top arch excavation section along the inner wall of the pre-designed tunnel cross-section; installing top arch support above the middle section support; excavating rock cores; leveling the ground for the horizontal excavation section; the pre-designed tunnel cross-section is horseshoe-shaped, with the lower excavation section located on the left and right sides of the tunnel; the middle excavation section located on the left and right sides of the tunnel; and the top arch excavation section located at the top of the tunnel. These steps achieve the excavation and support of the highly weathered mudstone tunnel. By adopting a ring excavation construction method, the excavation efficiency of mechanical equipment can be significantly improved, the excavation area is small, construction efficiency is high, and safety is high. The use of a continuous construction method for the support structure avoids long-term suspension of the support structure, improving the reliability of the support.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a method for excavation and support of tunnels in strongly weathered mudstone. Background Technology

[0002] The geological structure of a certain tunnel is as follows: a surface layer of silty clay; an upper layer of strongly weathered sandstone and mudstone interbedded, with extremely fractured rock mass, classified as soft rock; and a lower layer of moderately weathered sandstone and mudstone interbedded, with the sandstone being relatively hard and the mudstone relatively soft. The mudstone softens easily when soaked in water and is prone to fracturing after drying, resulting in a relatively fractured rock mass, also classified as soft rock. The mudstone softens easily when soaked in water, causing a sharp decrease in shear strength, making slope deformation and landslides along this weak layer highly likely. The tunnel has a long overall construction length, making construction challenging. Existing tunnel construction typically employs a stepped method, where the upper tunnel is excavated first, supported in advance, and then the lower tunnel is excavated. This linear construction method results in mutual interference between equipment and personnel at different stages, leading to low construction efficiency. Based on this, the CRD construction method was developed, in which both the upper and lower layers are divided into four excavation faces (left and right). This method offers high construction efficiency, but its management is complex. During construction, strict adherence to the principles of "advanced pipe support, rigorous grouting, short excavation times, strong support, frequent measurements, and early closure" is crucial. Timely measurements and feedback are essential to ensure construction safety. Proper coordination between construction processes is vital to shorten each cycle time and avoid prolonged soil exposure, which can lead to soil instability and increased settlement. The inventors discovered that improved construction efficiency is particularly necessary for strongly weathered mudstone. Strongly weathered sandstone and mudstone interlayers are particularly prone to collapse. Existing bench construction methods, including the bench construction method within the CRD method, typically employ advanced arch support. However, this advanced arch support method leaves the bottom of the support structure suspended for extended periods, making the structure's own weight a contributing factor to collapse. Based on this, tunnel boring machine (TBM) construction is considered. However, for tunnel sections with a large width, such as 23 meters, the cutterhead exhibits a problem where the edge linear velocity is much higher than the center linear velocity. To limit the edge linear velocity, the cutterhead rotation speed needs to be reduced, which affects construction efficiency. Furthermore, regarding the geological structure of the tunnel in this project, the upper layer consists of interbedded strongly weathered sandstone and mudstone, while the lower layer consists of interbedded moderately weathered sandstone and mudstone. The sandstone is relatively hard, resulting in low construction efficiency for the TBM cutterhead. Currently, there is no better construction method available. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for excavation and support of tunnels in strongly weathered mudstone, which can significantly improve the excavation efficiency of tunnels in strongly weathered mudstone and ensure the support and sealing effect.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for excavation and support of tunnels in strongly weathered mudstone, comprising the following steps:

[0005] S1. The excavation section is carried out along the inner wall of the pre-designed tunnel section.

[0006] S2. Install ground connecting beams and lower section support;

[0007] S3, the excavation section along the inner wall of the tunnel's pre-designed cross section;

[0008] S4. Install intermediate support above the lower support;

[0009] S5. Excavate the arch excavation section along the inner wall of the pre-set tunnel section;

[0010] S6. Install a top arch support above the middle section support;

[0011] S7. Core excavation;

[0012] S8, Leveling and tunneling section;

[0013] The above steps are used to excavate and support tunnels made of highly weathered mudstone.

[0014] In the preferred embodiment, the tunnel has a horseshoe-shaped pre-designed cross-section, which is divided into an arch section, a sidewall section, and a ground section. The arch section is a curve that is close to a circular arc, while the sidewall section and the ground section are curves with a curvature less than that of the arch section.

[0015] In the preferred embodiment, the lower excavation section is located on the left and right sides of the tunnel. The lower excavation section is a segment of a ring in which the outer wall of the lower excavation section coincides with the inner wall of the tunnel. The left and right sides of the lower excavation section are equidistant curves.

[0016] The middle tunneling section is located on the left and right sides of the tunnel. It is a segment of a ring in which the outer wall of the middle tunnel coincides with the inner wall of the tunnel. The left and right sides of the middle tunneling section are equidistant curves.

[0017] The top arch excavation section is located at the top of the tunnel. It is a segment of a ring in which the outer wall of the top arch excavation section coincides with the inner wall of the tunnel. The upper and lower sides of the top arch excavation section are equidistant curves.

[0018] In the preferred embodiment, the excavation of the lower tunneling section, the middle tunneling section, and the top arch tunneling section is carried out using a ring tunneling machine;

[0019] The aforementioned annular tunneling machine is equipped with multiple cutterheads.

[0020] In the preferred embodiment, the cross-section of the ring tunneling machine's head is inverted "U" shape, and the sides of the head are arranged in a stepped manner, with the first step, the second step, and the third step from the bottom up. The first step extends outwards, the second step is located in the middle, and the third step is located at the rear. The lower tunneling device is located on the front face of the first step, the middle tunneling device is located on the front face of the second step, and the top arch tunneling device is located on the front face of the third step.

[0021] In the preferred embodiment, the lower tunneling device, the middle tunneling device, and the top arch tunneling device are equipped with multiple fixed cutterheads, and a sliding cutterhead is also provided between the fixed cutterheads. The sliding cutterhead slides back and forth along the direction of the tunnel cross-section envelope.

[0022] In a preferred embodiment, end cutterheads are also provided at the edges of the lower tunneling device, the middle tunneling device, and the top arch tunneling device. The end cutterheads are used to remove the protrusions formed after excavation between the fixed cutterheads.

[0023] In the preferred embodiment, multiple reverse thrust cylinders are provided between the head and tail of the ring tunneling machine, and a rock breaking shed is provided at the tail. The rock breaking shed is used to break the "n"-shaped rock core formed after the head excavation.

[0024] A ground leveling support is installed after the rock breaking shed. A ground leveling excavation device is installed on the ground leveling support. The ground leveling excavation device has multiple sliding cutterheads that slide horizontally and are used to level the ground.

[0025] In the preferred embodiment, in step S2, the construction method of the ground connecting beam is to first drive multiple anchor rods or anchor piles into the bedrock, set up a steel cage, weld the anchor rods or anchor piles to the steel structure support arranged at intervals, pour the ground connecting beam as the support foundation, the steel structure support as the skeleton structure of the lower support, hang steel mesh between the steel structure supports, drive in anchor rods for reinforcement, and wet spray concrete to complete the first lining support.

[0026] In the middle tunneling section, corresponding steel structure support is installed and welded to the lower section support steel structure support. Steel mesh is hung between the steel structure supports, anchor rods are driven in for reinforcement, and wet shotcrete is used to complete the first lining support.

[0027] In the arch excavation section, small guide pipes are used for advance grouting support. Corresponding steel structure support is set up and welded to the steel structure support in the middle excavation section. Steel mesh is hung between the steel structure supports and fixedly connected to the small guide pipes. Wet shotcrete is used to complete the first lining support of the arch.

[0028] In the preferred scheme, the core excavation adopts the unconfined drilling and blasting method, that is, multiple drilling and blasting holes are set on the end face of the core. During blasting, the position near the upper outer edge is blasted first, then the position near the lower outer edge is blasted, and the position near the center is blasted last.

[0029] This invention provides a method for tunnel excavation and support in strongly weathered mudstone. By employing a ring excavation method, it significantly improves the excavation efficiency of mechanical equipment, resulting in a smaller excavation area, higher construction efficiency, and greater safety. The sequential construction method for the support structure avoids long-term suspension of the support structure, improving its reliability and preventing collapse of the surrounding rock due to the support structure's own weight. The multi-step excavation approach, prioritizing the excavation of the bottom structure, not only increases the bottom support strength but also facilitates the subsequent removal of upper waste material using a chute structure, significantly reducing the energy consumption for hoisting soil and rock waste. The core formed by the ring excavation is an unconfined structure, requiring less crushing work and making construction very convenient. This method offers high excavation and support efficiency, early rock surface closure, and is particularly suitable for construction in geological conditions involving interbedded sandstone and mudstone. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0031] Figure 1 This is a schematic diagram of the excavation cross-section of the present invention.

[0032] Figure 2 This is a schematic diagram of the cross-section of the support structure according to the present invention.

[0033] Figure 3 This is a schematic elevation view of the ring tunneling machine used in this invention.

[0034] In the diagram: Tunnel 1, Fixed cutterhead 2, Sliding cutterhead 3, End cutterhead 4, Rock core 5, Lower section support 6, Ground connecting beam 7, Middle section support 8, Top arch support 9, Anchor bolt 10, Lower tunneling device 11, Middle tunneling device 12, Top arch tunneling device 13, First step 14, Second step 15, Third step 16, Conveying auger 17, First conveyor belt 18, First conveying chute 19, Construction platform 20, Second conveying chute 21, Reaction frame 22, Reverse thrust cylinder 23, Rock crusher 24, Ground level tunneling device 25, Ground level support 26, Hoist 27, Second conveyor belt 28, Rock breaking shed 29, Anchor bolt 30, Lower tunneling section a, Middle tunneling section b, Top arch tunneling section c, Ground level tunneling section d, Head machine E, Tail machine F. Detailed Implementation

[0035] like Figures 1-3 A method for excavation and support of tunnels in strongly weathered mudstone includes the following steps:

[0036] Preferred solutions include Figure 1 In the tunnel 1, the preset cross-section is horseshoe-shaped, that is, the preset cross-section of the tunnel 1 is divided into an arch section, a side wall section and a ground section. The arch section is a curve that is close to a circular arc, and the side wall section and the ground section are curves. The curvature of the side wall section and the ground section is less than that of the arch section.

[0037] S1, excavate the lower tunnel section a along the inner wall of the pre-set section of tunnel 1; such as Figure 1 As shown,

[0038] Preferred solutions include Figure 1 In the middle, the lower excavation section a is located on the left and right sides of tunnel 1. The lower excavation section a is a segment of the ring whose outer wall coincides with the inner wall of tunnel 1. The left and right sides of the lower excavation section a are equidistant curves, that is, the distance between corresponding points of the envelope lines on the left and right sides of the cross section of the lower excavation section a is approximately the same.

[0039] S2, Install ground connecting beam 7 and lower section support 6;

[0040] Preferred solutions include Figure 2 In step S2, the construction method for the ground connecting beam 7 is to first drive multiple anchor rods or anchor piles into the bedrock. For moderately weathered sandstone, anchor rods are used for reinforcement, while for strongly weathered sandstone, anchor piles and pressure grouting are used for reinforcement. A reinforcing cage for the ground connecting beam 7 is then installed, and the reinforcing cage is tied to the anchor rods or anchor piles. The anchor rods or anchor piles are welded to the spaced steel structure supports. In this example, I-beams are preferred for the steel structure supports. The ground connecting beam 7 is poured as the support foundation, and the steel structure supports serve as the skeleton structure of the lower support 6. Reinforcing mesh is hung between the steel structure supports, anchor rods 30 are driven in for reinforcement, and wet-sprayed concrete is used to complete the first lining support.

[0041] S3, Excavation section b along the inner wall of the pre-set section of tunnel 1;

[0042] like Figure 1 In the middle, the middle tunneling section b is located on the left and right sides of tunnel 1. The middle tunneling section b is a segment of a ring whose outer wall coincides with the inner wall of tunnel 1. The left and right sides of the middle tunneling section b are equidistant curves.

[0043] Preferred solutions include Figure 2 In the middle section of the tunneling, the corresponding steel structure support is set up and welded to the lower section support 6. Steel mesh is hung between the steel structure supports, anchor rods 30 are driven in for reinforcement, and wet shotcrete is used to complete the first lining support.

[0044] S4. Install intermediate support 8 above the lower support 6;

[0045] S5. Excavate the arch excavation section c along the inner wall of the preset section of tunnel 1;

[0046] The top arch excavation section c is located at the top of tunnel 1. The top arch excavation section c is a segment of a ring whose outer wall coincides with the inner wall of tunnel 1. The upper and lower sides of the top arch excavation section c are equidistant curves.

[0047] S6. Install the top arch support 9 above the middle section support 8;

[0048] Preferred solutions include Figure 2In the middle section, small guide pipes are used for pre-grouting support in the arch excavation section c. Corresponding steel structure support is set up and welded to the steel structure support in the middle excavation section b. Steel mesh is hung between the steel structure supports and fixedly connected to the small guide pipes. Wet shotcrete is used to complete the first lining support of the arch.

[0049] S7, Excavate 5 rock cores;

[0050] Preferred solutions include Figure 2 In this process, core 5 is excavated using the unconfined drilling and blasting method. Multiple drill and blast holes are set on the end face of core 5. During blasting, the upper outer edge is blasted first, followed by the lower outer edge, and the center is blasted last. Controlled explosive charge is used throughout the drilling and blasting process to enhance safety and control. The excavation of core 5 is conducted within the rock-breaking chamber 29 of the ring tunneling machine. Alternatively, core 5 can be excavated using an excavator in a stepped excavation method.

[0051] S8, Leveling and excavation section d;

[0052] Preferably, the ground-level tunneling section d is excavated using a ground-level tunneling device 25, which is located after the rock-breaking shed 29.

[0053] The above steps are used to excavate and support tunnels made of highly weathered mudstone.

[0054] Preferred solutions include Figures 1-3 The excavation of the lower tunneling section a, the middle tunneling section b, and the top arch tunneling section c is carried out using a ring tunneling machine;

[0055] The aforementioned annular tunneling machine is equipped with multiple cutterheads, and the cutterheads are distributed as follows: Figure 1 As shown, the cutterhead is driven to rotate by a drive device. Preferably, the drive device is a hydraulic motor, which drives the cutterhead to rotate through a set of gears. Multiple alloy or artificial diamond cutter heads are provided on the surface of the cutterhead. This invention employs a multi-cutterhead structure. Because the diameter of each cutterhead is small, the rotational speed can be significantly increased, thus ensuring that the linear velocities of the cutter heads at various positions on the cutterhead are not significantly different. This greatly increases the tunneling speed, thereby improving support efficiency and rock surface sealing speed, and preventing secondary weathering.

[0056] For the preferred solution, please refer to [link / reference]. Figure 1 In the middle, the cross-section of the head E of the ring tunneling machine is inverted "U" shaped, and the sides of the head E are arranged in a stepped pattern, such as... Figure 3As shown, from bottom to top, there are three steps: the first step 14, the second step 15, and the third step 16. The first step 14 extends outwards, the second step 15 is in the middle, and the third step 16 is at the rear. The lower tunneling device 11 is located on the front face of the first step 14, the middle tunneling device 12 is located on the front face of the second step 15, and the top arch tunneling device 13 is located on the front face of the third step 16.

[0057] Preferred solutions include Figure 1 Multiple fixed cutterheads 2 are installed on the lower tunneling device 11, the middle tunneling device 12, and the top arch tunneling device 13. A sliding cutterhead 3 is also installed between the fixed cutterheads 2, sliding back and forth along the direction of the tunnel section envelope. The sliding cutterhead 3 is a cutterhead mounted on a sliding block and is driven by a hydraulic cylinder to reciprocate along a groove. The sliding cutterhead 3 is used to excavate the "X"-shaped area formed between the fixed cutterheads 2. Preferably, the area of ​​the "X"-shaped area is smaller than the area of ​​the fixed cutterheads 2 to avoid the cutting speed of the sliding cutterhead 3 affecting the tunneling speed of the fixed cutterheads 2.

[0058] In a preferred embodiment, the fixed cutter head 2 and the sliding cutter head 3 are staggered in the vertical plane to avoid mutual interference. For example... Figure 3 As shown, the fixed cutter head 2 is typically positioned closer to the working face, while the sliding cutter head 3 is located behind the fixed cutter head 2. The front and rear positions described in this example are... Figure 3 For the sake of accuracy, Figure 3 The left side is the front. Figure 3 The right side is the rear, which is also the operating direction of the ring tunneling machine.

[0059] Preferred solutions include Figure 1 In the middle, end cutterheads 4 are also provided at the edges of the lower tunneling device 11, the middle tunneling device 12, and the top arch tunneling device 13. The end cutterheads 4 are used to remove the protrusions formed after excavation between the fixed cutterheads 2. The diameter of the end cutterheads 4 is smaller than the diameter of the fixed cutterheads 2.

[0060] Preferred solutions include Figure 3In the ring tunneling machine, multiple reverse thrust cylinders 23 are installed between the head E and tail F of the machine to control the tunneling direction. In a preferred embodiment, after the lower tunneling device 11, conveying screws 17 are installed on both sides to lift mud and rock cuttings to the first conveyor belt 18. A second conveyor belt 28 is installed at the tail end of the first conveyor belt 18, and the elevation of the first conveyor belt 18 is higher than that of the second conveyor belt 28. After the middle tunneling device 12, a first conveying chute 19 is installed to transport mud and rock cuttings to the first conveyor belt 18. After the top arch tunneling device 13, a second conveying chute 21 is installed to transport mud and rock cuttings to the first conveyor belt 18. The first conveyor belt 18 gravity-feeds the material to the second conveyor belt 28, and the rock cuttings are transported to the rear end for processing, including separation, sand making, circulation, and concrete preparation. After the rock breaking shed 29, a hoist 27 is installed. The discharge port of the hoist 27 is located at the inlet of the rock crusher 24 to crush large pieces of rock. Preferably, the rock crusher 24 is a jaw crusher or an impact crusher.

[0061] A rock-breaking shed 29 is provided at the tail F of the machine. The rock-breaking shed 29 is used for the “n”-shaped rock core 5 formed after the crusher head E is excavated.

[0062] A ground leveling support 26 is provided after the rock breaking shed 29. A ground leveling tunneling device 25 is provided on the ground leveling support 26. The ground leveling tunneling device 25 is provided with multiple sliding cutterheads 3 that slide in the horizontal direction. The sliding cutterheads 3 are used to level the ground.

[0063] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in these embodiments can be arbitrarily combined without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for excavation and support of tunnels in strongly weathered mudstone, characterized in that: Includes the following steps: S1, Excavate the inner wall of the tunnel (1) along the preset cross section of the tunnel (a); The lower excavation section (a) is located on the left and right sides of the tunnel (1). The lower excavation section (a) is a segment of a ring whose outer wall coincides with the inner wall of the tunnel (1). The left and right sides of the lower excavation section (a) are equidistant curves. S2, Install ground tie beam (7) and lower section support (6); S3, Excavation of the inner wall of the tunnel (1) along the preset cross section (b); The middle tunnel section (b) is located on the left and right sides of the tunnel (1). The middle tunnel section (b) is a section of a ring whose outer wall coincides with the inner wall of the tunnel (1). The left and right sides of the middle tunnel section (b) are equidistant curves. S4. Install a middle section support (8) above the lower section support (6). S5. Excavate the arch excavation section (c) along the inner wall of the pre-set section of the tunnel (1); The top arch excavation section (c) is located at the top of the tunnel (1). The top arch excavation section (c) is a segment of the ring whose outer wall coincides with the inner wall of the tunnel (1). The upper and lower sides of the top arch excavation section (c) are equidistant curves. The excavation of the lower tunneling section (a), the middle tunneling section (b), and the top arch tunneling section (c) was carried out using a ring tunneling machine; The aforementioned annular tunneling machine is equipped with multiple cutterheads; The head (E) of the ring tunneling machine has an inverted "U" shaped cross section. The sides of the head (E) are arranged in a stepped manner, with the first step (14), the second step (15), and the third step (16) from bottom to top. The first step (14) extends out at the front, the second step (15) is located in the middle, and the third step (16) is located at the rear. The lower tunneling device (11) is set on the front end face of the first step (14), the middle tunneling device (12) is set on the front end face of the second step (15), and the top arch tunneling device (13) is set on the front end face of the third step (16). Multiple fixed cutterheads (2) are provided on the lower tunneling device (11), the middle tunneling device (12) and the top arch tunneling device (13). A sliding cutterhead (3) is also provided between the fixed cutterheads (2). The sliding cutterhead (3) slides back and forth along the direction of the tunnel (1) cross section envelope. End cutterheads (4) are also provided at the edges of the lower tunneling device (11), the middle tunneling device (12) and the top arch tunneling device (13). The end cutterheads (4) are used to remove the protrusions formed after excavation between the fixed cutterheads (2). Multiple reverse thrust cylinders (23) are provided between the head (E) and tail (F) of the ring tunneling machine. A rock breaking shed (29) is provided at the tail (F). The rock breaking shed (29) is used to break the "n"-shaped rock core (5) formed after the head (E) is excavated. A ground leveling support (26) is provided after the rock breaking shed (29). A ground leveling tunneling device (25) is provided on the ground leveling support (26). The ground leveling tunneling device (25) is provided with multiple sliding cutterheads (3) that slide in the horizontal direction. The sliding cutterheads (3) are used to level the ground. S6. Set up a top arch support (9) above the middle section support (8). S7. Excavate rock cores (5); S8, Leveling and tunneling section (d); The above steps are used to excavate and support tunnels made of highly weathered mudstone.

2. The method for excavation and support of tunnels in strongly weathered mudstone according to claim 1, characterized in that: The tunnel (1) has a horseshoe-shaped cross section, which means that the tunnel (1) has a cross section divided into an arch section, a side wall section and a ground section. The arch section is a curve that is close to a circular arc, while the side wall section and the ground section are curves. The curvature of the side wall section and the ground section is less than that of the arch section.

3. The method for excavation and support of tunnels in strongly weathered mudstone according to claim 1, characterized in that: In step S2, the construction method of the ground connecting beam (7) is to first drive multiple anchor rods or anchor piles into the bedrock, set up a steel cage, weld the anchor rods or anchor piles to the steel structure support arranged at intervals, pour the ground connecting beam (7) as the support foundation, the steel structure support as the skeleton structure of the lower support (6), hang steel mesh between the steel structure support, drive in anchor rods (30) for reinforcement, and wet spray concrete to complete the first lining support; In the middle tunneling section (b), the corresponding steel structure support is set up and welded to the lower section support (6). Steel mesh is hung between the steel structure supports, anchor rods (30) are driven in for reinforcement, and wet shotcrete is used to complete the first lining support. In the arch excavation section (c), pre-grouting support is provided using small guide pipes. Corresponding steel structure support is installed and welded to the steel structure support in the middle excavation section (b). Reinforcing mesh is hung between the steel structure supports, and the reinforcing mesh is fixedly connected to the small guide pipes. Wet sprayed concrete is used to complete the arch lining support.

4. The method for excavation and support of tunnels in strongly weathered mudstone according to claim 1, characterized in that: The core (5) excavation adopts the unrestricted drilling and blasting method, that is, multiple drilling and blasting holes are set on the end face of the core (5). During blasting, the construction plan is to blast the upper part near the outer edge first, then the lower part near the outer edge, and finally the part near the center.

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