Loess tunnel supporting structure and construction method

Abstract

The invention belongs to the technical field of tunnel construction, discloses a loess tunnel supporting structure and a construction method, and aims to solve the problems that an existing advanced large pipe shed technology is obvious in cutting effect, prone to clamping stagnation in jacking and poor in grouting adaptability in loess tunnel application. The supporting structure comprises a guide wall with an oval guide hole, a pipe shed assembly with the oval cross section, a cutting head with an installation cavity formed in the end and an intra-cavity tunneling mechanism. The pipe shed assembly is internally provided with two partition plates and divided into three independent areas. The construction method comprises the steps that after the guide wall is constructed, the motor drives the transmission assembly to drive the tunneling mechanism to work, the pipe shed assembly is jacked synchronously and mechanically, partition grouting is conducted after jacking is conducted in place, and tunnel excavation is conducted after grouting of all the pipe shed assemblies is completed. Cutting of loess cracks and surrounding rock disturbance are reduced through the oval pipe shed, jacking clamping stagnation is avoided through the active tunneling mechanism, supporting reliability is improved through partition grouting, and tunnel construction safety and efficiency are guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of tunnel construction technology, specifically relating to a support structure and construction method for loess tunnels. It is particularly suitable for advanced support engineering of loess tunnels with well-developed vertical fissures, poor self-stability of surrounding rock, and sensitivity to construction disturbance. The aim is to solve key technical problems in loess tunnel support, such as cutting effect, jacking jamming, and grouting compatibility, through synergistic innovation of structure and construction technology. Background Technology

[0002] In tunnel construction, loess tunnels present significant challenges due to the unique engineering geological characteristics of the loess layer. Loess layers commonly exhibit problems such as well-developed vertical fissures, large fluctuations in water content, poor self-stability of the surrounding rock, and susceptibility to softening and disintegration upon contact with water. These issues lead to frequent occurrences during tunnel construction, including rockfalls, excessive over-excavation, and severe overconsumption of concrete. These problems not only significantly reduce construction efficiency but also pose major safety risks such as surface subsidence, rockfalls, and roof collapses. Therefore, there is an urgent need to develop efficient advanced support technologies adapted to the geological characteristics of loess.

[0003] Currently, advanced pipe roof technology is a commonly used advanced support method for weak and fractured surrounding rock sections of tunnels. Among them, the patent document with publication number CN115898415A proposes a self-drilling advanced pipe roof structure and construction method for large-span tunnels without excavation. This scheme uses steel arch frames in conjunction with casings and limiting blocks, and uses a self-drilling rig to drill the pipe roof into the surrounding rock. Cement mortar grouting is used to achieve rock mass cementation and strengthening. It has achieved certain results in the support of weak and fractured surrounding rock in general large-span tunnels, and can reduce construction procedures and control surface settlement.

[0004] However, the aforementioned existing technologies and similar advanced large-diameter pipe roof technologies are mainly designed for weak surrounding rock in general tunnels, and do not fully consider the special geological requirements of loess tunnels (especially in areas with developed vertical fissures). When actually applied to loess tunnels, they have many key defects and are difficult to meet engineering requirements: Firstly, existing technologies mostly use conventional circular cross-section pipe roofs, which have poor fit with the vertical fissures in the loess layer. During the jacking process, they are prone to rigidly cutting the fissure loess, destroying the original self-stabilizing structure of the surrounding rock, causing the fissures to expand further and the blocks to separate. This exacerbates the risk of rockfall and over-excavation, which contradicts the core requirement of protecting the fissure structure and reducing disturbance in loess tunnels.

[0005] Secondly, existing technologies rely on passive jacking or borehole-assisted jacking modes, without integrating active tunneling and obstacle clearing structures. When encountering obstacles such as hard soil blocks and calcareous nodules in the loess layer, jacking jams, steel pipe displacement and deformation, or even damage may occur, seriously affecting the continuity of construction. At the same time, passive jacking requires a large jacking force to overcome resistance, which not only makes construction difficult but also causes severe disturbance to the loose loess layer, further damaging the self-stability of the fractured surrounding rock.

[0006] In summary, while existing advanced large pipe roof technology has certain advantages in general tunnel support, it still has drawbacks such as significant cutting effect and low jacking efficiency when considering the special needs of loess tunnels, such as the development of vertical cracks and sensitivity to construction disturbance. There is an urgent need for a special support structure and construction method for loess tunnels that can reduce crack cutting and achieve active excavation. Summary of the Invention

[0007] Addressing the core engineering challenges of loess tunnels, such as well-developed vertical fissures, poor surrounding rock stability, and sensitivity to construction disturbances, existing advanced large-diameter pipe roof technology suffers from significant drawbacks, including pronounced cutting effects, easy jamming during jacking, poor grouting adaptability, and insufficient support reliability. This invention aims to provide a support structure and construction method for loess tunnels. This structure reduces rigid cutting of loess fissures by employing elliptical cross-section pipe roofs. A cutting head integrating an active tunneling mechanism is installed at the end of the pipe roof assembly to achieve low-disturbance jacking. Internal partitions within the pipe roof create zoned grouting spaces, and grouting status monitoring sensors are installed. Combined with differentiated grouting processes and post-grouting core sampling, this effectively reduces construction disturbance in the loess surrounding rock, improves grout fullness and adaptability, ensures pipe roof jacking accuracy, and controls construction costs. This precisely adapts to the specific engineering needs of loess tunnels, completely resolving the insufficient adaptability and reliability issues of existing technologies in loess tunnel support.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On the one hand, a loess tunnel support structure includes a guide wall set along the tunnel entrance, and further includes: Several guide holes, with an elliptical cross-section, are spaced through the guide wall along the tunnel depth direction; The pipe roof assembly is adapted to the guide hole and corresponds one-to-one; A cutting head is located at the front end of the pipe shed assembly, and an installation cavity is provided inside the installation cavity, wherein a transmission assembly is provided. The tunneling mechanism is installed in the mounting cavity and is driven by a transmission assembly to excavate the soil in front of the support structure.

[0009] Furthermore, the pipe roof assembly includes: The pipe body has an elliptical cross-section and several grouting holes on its outer perimeter. Two partitions are fitted inside the tube, and their end faces are parallel to the long axis of the tube.

[0010] Furthermore, the tunneling mechanism includes: The push-forward assembly is rotatably mounted in the middle of the mounting cavity and periodically contacts the transmission assembly; The side-push assembly is rotatably mounted on the top and bottom of the cutting head via bearings and is slidably connected to the transmission assembly.

[0011] Furthermore, the push-forward component includes: Two transmission rods are symmetrically installed on both sides of the support plate inside the installation cavity, and elastic elements are provided between them and the support plate. Through slots are opened at the ends. Two forward-pushing scrapers correspond one-to-one with the transmission rods and are slidably installed in the through groove.

[0012] Furthermore, the side-pushing component includes: Two lower push plates are symmetrically installed on both sides of the central axis of the support plate, and each lower push plate is slidably connected to the transmission assembly through a rotating wheel; Two upper push plates, corresponding one-to-one with the lower push plate, are installed on opposite sides of the lower push plate.

[0013] Furthermore, the transmission assembly includes: The driving wheel has first truncated pyramids spaced at intervals on its outer periphery; Two driven wheels are located on the same horizontal plane as the driving wheel and are rotatably installed in the mounting cavity. Each wheel has a second truncated pyramid spaced apart on its outer periphery.

[0014] Furthermore, the driving wheel and the two driven wheels are arranged sequentially along the cross-section of the tube roof assembly, and the middle driven wheel periodically meshes with the driving wheel and the other driven wheel through the second truncated pyramid.

[0015] Furthermore, the tunneling mechanism also includes: Two advancing turntables are symmetrically mounted on both sides of the front pushing assembly. Each advancing turntable is connected to the transmission assembly via a belt and has prismatic teeth spaced apart on its outer periphery.

[0016] On the other hand, a method for supporting loess tunnels includes the following steps: S1. Construct a guide wall with an elliptical guide hole at the tunnel entrance; S2. The pipe roof assembly is pushed forward along the guide hole. During the pushing process, the tunneling mechanism's advancing turntable, front push scraper and side push plate are driven by the transmission assembly to work together to carry out active excavation and soil dredging. S3. After the pipe roof assembly is jacked into place, the independent areas formed by the partition are grouted in sections. The grout penetrates into the loess fissures through the grouting holes on the outer periphery of the pipe body. S4. After all pipe roof components have been grouted and the grout has solidified, tunnel excavation will commence.

[0017] Furthermore, the jacking process in S2 is specifically as follows: By driving the transmission assembly, the driving wheel and the driven wheel periodically mesh to transmit power, driving the advancing turntable to rotate and break the obstacles in front. At the same time, the driven wheel drives the transmission rod of the forward pushing assembly to swing, causing the forward pushing scraper to push the soil back and forth. The lower and upper side pushing plates of the side pushing assembly guide the soil to both sides, realizing active excavation and low-disturbance jacking.

[0018] The beneficial effects of this invention are: 1. The elliptical cross-section pipe roof component in this invention has a higher degree of fit with the vertical cracks in the loess. Combined with the transition arc design of the cutting head, it avoids rigid cutting of the cracked loess during jacking. At the same time, the tunneling mechanism drives the active wheel and driven wheel through the motor to rotate the advancing turntable to break up obstacles. The forward pushing component and the side pushing component work together to push and guide the soil, replacing the traditional passive jacking mode, greatly reducing the disturbance to the loess layer, protecting the self-stabilizing structure of the surrounding rock, and reducing the phenomenon of rockfall and over-excavation from the root.

[0019] 2. The transmission component of the tunneling mechanism of this invention transmits power through the periodic meshing of the driving wheel and the driven wheel. The prismatic teeth of the advancing turntable can efficiently break obstacles such as hard soil blocks and calcareous nodules. The forward pushing scraper achieves reciprocating soil pushing through the sliding cooperation of the transmission rod and the sliding column. The side pushing plate guides the soil to both sides through the sliding connection between the rotating wheel and the driven wheel. The three work together to complete active excavation, obstacle clearing and soil dredging, avoiding the jamming problem of traditional jacking, ensuring construction continuity, reducing jacking resistance and improving construction efficiency.

[0020] 3. The partitions inside the pipe roof assembly of this invention divide the pipe body into different areas. With the selection of differentiated grout, the grout in the middle area is used to fill the core space, while the grout in the upper and lower areas is used to penetrate and reinforce the surrounding rock, which is suitable for the characteristics of loess layers with large fluctuations in permeability and water content. During the grouting process, the filling status can be monitored in real time by sensors on the partitions. Combined with multi-stage pressure grouting technology, it can be ensured that the grout is fully filled and firmly bonded, effectively solving the problem of insufficient filling by traditional single grouting and greatly improving the stability and reliability of the support structure. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the guide wall structure for installing the pipe roof assembly of the present invention; Figure 2 Top view of the pipe roof assembly of the present invention; Figure 3 This is a schematic diagram of the pipe roof assembly structure according to Embodiment 1 of the present invention; Figure 4 This is a top view of a pipe roof assembly according to an embodiment of the present invention; Figure 5 This is a side view of a pipe roof assembly according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the pipe roof assembly-tunneling mechanism structure according to Embodiment 2 of the present invention; Figure 7 This is a side view of the pipe roof assembly-tunneling mechanism according to Embodiment 2 of the present invention; Figure 8 For the present invention Figure 7 Cross-sectional view at the MM section; Figure 9 This is a schematic diagram of the cutting head structure of the pipe roof assembly of the present invention; Figure 10 For the present invention Figure 5 The main view; Figure 11 For the present invention Figure 10 Cross-sectional view at point NN; Figure 12 This is a schematic diagram of the driven wheel-lower push plate-forward scraper structure of the present invention; Figure 13 This is a schematic diagram of the transmission rod-forward scraper structure of the present invention; Figure 14 This is a schematic diagram of the single upper push plate-lower push plate structure of the present invention; Figure 15 This is a schematic diagram of the lower push plate structure of the present invention; Figure 16 This is a schematic diagram of the rotary wheel structure of the present invention; Figure 17 This is a schematic diagram of the driven wheel structure of the present invention.

[0022] in: 1. Guide wall; 101. Guide hole; 2. Cutting head; 201. Installation cavity; 2011. Support plate; 3. Pipe roof assembly; 301. Pipe body; 3011. Grouting hole; 302. Partition plate; 4. Tunneling mechanism; 401. Advancing turntable; 402. Transmission rod; 4022. Through groove; 403. Front push scraper; 404. Lower push plate; 4041. Slide groove; 405. Upper push plate; 5. Bearing; 6. Rotary wheel; 601. Limiting post; 7. Driving wheel; 8. Driven wheel; 801. Second truncated pyramid; 802. Limiting groove. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] Example 1 This embodiment discloses a foundation support structure for a loess tunnel, including a guide wall 1 and a pipe roof assembly 3. The guide wall 1 is installed along the tunnel entrance and serves as the installation foundation for the entire support structure. Several pre-set guide holes 101 penetrate the guide wall 1 at intervals along the tunnel depth direction. The cross-section of each guide hole 101 is elliptical, adapted to the pipe roof assembly 3, providing a precise guiding channel for the jacking of the pipe roof assembly 3. The pipe roof assembly 3, as the core support component, is installed corresponding to the guide holes 101. After jacking, it penetrates deep into the loess layer, and the surrounding rock is reinforced through zoned grouting.

[0025] Specifically, the guide wall 1 is mainly constructed of C30 reinforced concrete, with an internal steel frame welded together by connecting ribs to ensure sufficient load-bearing strength to withstand the horizontal thrust during the jacking of the pipe roof assembly 3. The diameter of the guide hole 101 is slightly larger than the outer diameter of the pipe roof assembly 3, and the hole wall is smooth and flat, ensuring that the pipe roof assembly 3 can pass through smoothly and also providing initial positioning through the fit between the hole wall and the pipe roof assembly 3. The axis of the guide hole 101 is parallel to the tunnel design axis, with a hole inclination rate ≤0.5%, to avoid route deviation during the jacking process.

[0026] The pipe roof assembly 3 includes a pipe body 301 and two partition plates 302. The pipe body 301 is a steel pipe with an elliptical cross-section, made of Q355 steel, possessing good bending and shear resistance. The elliptical structure provides a higher degree of fit with the vertical cracks in the loess layer, significantly reducing the rigid cutting effect during the jacking process. Several grouting holes 3011 are opened on the outer periphery of the pipe body 301, evenly distributed along the axial and circumferential directions to ensure uniform penetration of grout into the surrounding loess cracks. The two partition plates 302 are fitted inside the pipe body 301, with their end faces parallel to the long axis of the pipe body 301, dividing the interior of the pipe body 301 into three independent grouting zones, providing a structural basis for zoned grouting. The partition plates 302 are made of 304 stainless steel plate, precisely fitted to the inner wall of the pipe body 301, and tightly fitted after installation to prevent grout leakage during injection.

[0027] The working principle of this embodiment is as follows: First, a guide wall 1 with an elliptical guide hole 101 is constructed at the tunnel entrance. After the concrete strength of the guide wall 1 reaches the design requirements, the pipe roof assembly 3 is slowly jacked along the guide hole 101 to the preset depth. During the jacking process, the elliptical cross-section pipe body 301 reduces the cutting of vertical cracks in the loess, protecting the self-stabilizing structure of the surrounding rock. After the pipe roof assembly 3 is jacked into place, differentiated grout is injected into the area separated by three partitions 302 through the open end of the pipe body 301. The grout seeps into the loess cracks through the grouting holes 3011 on the outer periphery of the pipe body 301, achieving cementation and reinforcement of the surrounding rock. After all the pipe roof assemblies 3 are grouted and the grout solidifies, a continuous and stable advanced support system is formed, providing a safety guarantee for subsequent tunnel excavation.

[0028] Example 2 This embodiment, based on Embodiment 1, adds a cutting head 2, a tunneling mechanism 4, and a transmission assembly to form a complete support structure with active tunneling function. The cutting head 2 is fixedly installed at the front end of the pipe body 301, and the internal installation cavity 201 provides installation space for the tunneling mechanism 4 and the transmission assembly. The tunneling mechanism 4 is installed within the installation cavity 201 and is driven by the transmission assembly to achieve active excavation operations. Combined with the elliptical structure of the pipe body 301, it achieves low-disturbance, high-efficiency jacking.

[0029] Specifically, the cutting head 2 is a conical shell structure made of the same Q355 steel as the pipe body 301. A transition arc is provided at the connection point with the pipe body 301 to avoid localized stress concentration due to structural abrupt changes during jacking, while also reducing additional disturbance to the loess surrounding rock. A support plate 2011 is fixedly installed inside the mounting cavity 201 of the cutting head 2. The support plate 2011 provides stable mounting support for the tunneling mechanism 4 and transmission components, ensuring stable stress distribution to each component during tunneling.

[0030] The transmission assembly includes a drive wheel 7 and two driven wheels 8. The drive wheel 7 is fixedly connected to the output shaft of the motor, and a first truncated pyramid is provided at intervals on its outer periphery. The two driven wheels 8 are located in the same horizontal plane as the drive wheel 7 and are rotatably mounted on the support plate 2011 in the mounting cavity 201. A second truncated pyramid 801 is provided at intervals on the outer periphery of each of them. The drive wheel 7 and the two driven wheels 8 are arranged sequentially along the cross-section of the pipe roof assembly 3. The middle driven wheel 8 periodically meshes with the first truncated pyramid of the drive wheel 7 and the second truncated pyramid 801 of the other driven wheel 8 through the second truncated pyramid 801, so as to realize the transmission and conversion of power and provide continuous and stable power for the tunneling mechanism 4.

[0031] The tunneling mechanism 4 includes a front thrust assembly, a side thrust assembly, and two advancing turntables 401. The two advancing turntables 401 are symmetrically rotated and installed on both sides of the front thrust assembly. Each advancing turntable 401 is connected to the driven wheel 8 of the transmission assembly via a belt. The diamond-shaped teeth spaced on its outer periphery can efficiently break up obstacles such as hard soil blocks and calcareous nodules in the loess layer. The forward pushing assembly includes two transmission rods 402 and two forward pushing scrapers 403. The two transmission rods 402 are symmetrically installed on both sides of the support plate 2011. An elastic element (specifically a helical spring) is provided between the transmission rods 402 and the support plate 2011. One end of the helical spring is fixedly connected to the transmission rod 402, and the other end is fixedly connected to the support plate 2011 to realize the reciprocating reset of the transmission rods 402. A through groove 4022 is opened at the end of the transmission rod 402. The two forward pushing scrapers 403 correspond one-to-one with the transmission rods 402 and are slidably installed in the through groove 4022. The end of the transmission rod 402 periodically contacts the second truncated pyramid 801 of the driven wheel 8, which can drive the forward pushing scrapers 403 to push soil reciprocally.

[0032] It should be noted that, in order to prevent soil from entering the installation cavity 201 during drilling and affecting the operation of the components, flexible sealing elements are installed between the front push scraper 403 and the inner wall of the installation cavity 201, and between the front push scraper 403 and the support plate 2011. The flexible sealing element is a rubber bellows, one end of which is fixedly connected to the side of the front push scraper 403, and the other end is fixedly connected to the inner wall of the installation cavity 201 and the support plate 2011 respectively. It can deform synchronously with the extension and retraction of the front push scraper 403 to achieve dynamic sealing.

[0033] The side-pushing assembly includes two lower side-pushing plates 404 and two upper side-pushing plates 405. The two lower side-pushing plates 404 are symmetrically installed on both sides of the central axis of the support plate 2011. Each lower side-pushing plate 404 is slidably connected to the driven wheel 8 of the transmission assembly through the rotating wheel 6. The two upper side-pushing plates 405 correspond one-to-one with the lower side-pushing plates 404 and are installed on the opposite side of the lower side-pushing plates 404. They can swing to both sides under the drive of the driven wheel 8 to guide the cut soil to both sides of the pipe roof assembly 3.

[0034] It should be noted that, since the rotating wheel 6 needs to be slidably connected to the outer lower push plate 404, and the rotating wheel 6 is installed through the side wall of the cutting head 2, to prevent soil from entering the mounting cavity 201 through the through hole between the rotating wheel 6 and the cutting head 2 during drilling, and subsequently intruding into the mating gap between the rotating wheel 6 and the driven wheel 8 and the inside of the bearing 5, a flexible sealing sleeve is installed between the inner wall of the through hole between the rotating wheel 6 and the cutting head 2. One end of the flexible sealing sleeve is fixedly connected to the inner side wall of the cutting head 2, and the other end is tightly fitted to the outer peripheral wall of the rotating wheel 6. It can deform synchronously with the rotation of the rotating wheel 6 to form a dynamic seal. At the same time, skeleton oil seals are installed between the inner ring of the bearing 5 and the connecting shaft of the side push assembly, and between the outer ring of the bearing 5 and the mounting hole of the cutting head 2. The lip of the skeleton oil seal is tightly fitted to the mating surface to achieve dual sealing protection of static and dynamic properties.

[0035] In this embodiment, the support structure fully considers environmental protection requirements in material selection. The main structure, such as the pipe body 301 and the partition plate 302, is made of low-carbon alloy steel that is corrosion-resistant and harmless to soil, avoiding the release of harmful heavy metals after long-term rusting in the soil. Flexible components such as rubber corrugated pipes and elastic sealing sleeves are made of biodegradable polymer materials that can gradually decompose in the soil environment, preventing the accumulation of long-term solid waste. At the same time, the elliptical cross-section design optimizes the wall thickness of the pipe body 301, reducing the amount of steel used while ensuring support strength, thus reducing resource consumption and adapting to usage scenarios where the structure is not recyclable.

[0036] The working principle of this embodiment is as follows: Based on Embodiment 1, the motor drives the transmission assembly to operate, the driving wheel 7 rotates and transmits power through the periodic meshing of the driven wheel 8; the driven wheel 8 drives the two advancing turntables 401 to rotate through the belt, using the rhomboid teeth to break the obstacles in front, and drives the transmission rod 402 of the forward pushing assembly to swing, driving the forward pushing scraper 403 to push the soil back and forth, while the rotating wheel 6 drives the lower side pushing plate 404 and the upper side pushing plate 405 of the side pushing assembly to swing and guide the soil; while the tunneling mechanism 4 completes active excavation, obstacle clearing and soil guiding, the mechanical jacking equipment applies a continuous jacking force to the pipe roof assembly 3, and the pipe body 301 is jacked along the guide hole 101 in the direction of tunnel depth, the elliptical cross section reduces the cutting effect, and the transition arc reduces local disturbance; after jacking into place, differentiated grout is injected according to the zonal grouting method of Embodiment 1 to form a reinforced support system, and then tunnel excavation is carried out.

[0037] Example 3 This embodiment, based on the support structure with active tunneling function described in Embodiment 2, discloses a complete construction method for loess tunnel support, ensuring precise adaptation between the construction process and the support structure. The steps are as follows: S1. Based on the tunnel design axis and loess geological survey data, determine the construction location and dimensions of guide wall 1. After excavating the foundation pit, erect a steel reinforcement frame, use connecting bars to weld the steel frame into a whole, tie the steel mesh and set up the formwork, and pour C30 concrete to form guide wall 1. Before the concrete initially sets, open guide holes 101 with an elliptical cross-section at preset intervals and angles to ensure that the axis of guide holes 101 is parallel to the tunnel design axis. When the concrete strength reaches more than 80% of the design requirements, the construction of guide wall 1 is completed.

[0038] S2. Hoist the pipe roof assembly 3, equipped with the cutting head 2, the tunneling mechanism 4, and the transmission assembly, to the guide hole 101, aligning the cutting head 2 with the entrance of the guide hole 101; start the motor to drive the transmission assembly to operate, driving the tunneling mechanism 4's advancing turntable 401, the front push scraper 403, and the side push plate to work together, while simultaneously starting the mechanical jacking equipment to drive the pipe roof assembly 3 along the guide hole 101 towards the tunnel depth at a uniform speed; during the jacking process, observe the operating status of the tunneling mechanism 4 in real time to ensure that the obstacles are completely broken and the soil is smoothly cleared, until the pipe roof assembly 3 is jacked to the preset depth.

[0039] S3. First, check the installation firmness of the two partitions 302 inside the pipe body 301 to ensure good sealing of each grouting area; set up grouting stations on the outside of the guide wall 1 and prepare differentiated grouts, with ordinary silicate cement grout injected into the middle area of ​​the pipe body 301 and cement-water glass double-liquid grout injected into the upper and lower areas; connect the grout outlet pipe of the grouting equipment to the interface of each grouting area of ​​the pipe body 301 respectively, and grout into each area in sequence. During the grouting process, control the grouting pressure and grouting volume to ensure that the grout fully penetrates into the loess cracks through the grouting hole 3011 to achieve cementation and reinforcement; after grouting, cure according to the design requirements until the grout setting strength reaches the specified value.

[0040] S4. After all the grouting slurry of the pipe roof components 3 has solidified and formed a continuous and stable advanced support system, the tunnel excavation is carried out in stages according to the tunnel excavation process. During the excavation process, the surrounding rock condition is closely monitored, and the support effect of the pipe roof components 3 is used to suppress rockfall and collapse, so as to ensure construction safety and stability. After excavating a certain distance, subsequent support operations are carried out in a timely manner to ensure the overall structural safety of the tunnel.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A loess tunnel support structure comprising a guide wall (1) arranged along the tunnel portal, characterized in that, Also include: A number of guide holes (101), cross-section is oval structure, along the tunnel depth direction interval through the guide wall (1) is provided; Pipe shed assembly (3), with the guide hole (101) is adapted, and one to one correspondence; Cutting head (2), set in the front end of the pipe shed assembly (3), inside opening has installation cavity (201), the installation cavity (201) is equipped with transmission assembly; Tunneling mechanism (4), installed in the installation cavity (201), through transmission assembly drive tunneling mechanism to the soil in front of the support structure is excavated.

2. The loess tunnel support structure according to claim 1, characterized in that, The pipe shed assembly (3) comprises: Pipe body (301), cross-section is oval structure setting, and the outer periphery is provided with a plurality of grouting hole (3011); Two baffle (302), sleeve joint in the pipe body (301), and the end face is parallel to the long axis of the pipe body (301).

3. The loess tunnel support structure according to claim 2, characterized in that, The tunneling mechanism (4) comprises: Front push assembly, rotationally installed in the middle of the installation cavity (201), and with transmission assembly periodic contact; Side push assembly, through the bearing (5) rotationally set in the top and bottom of the cutting head (2), and with transmission assembly sliding connection.

4. The loess tunnel support structure according to claim 3, characterized in that, The front push assembly comprises: Two transmission rod (402), symmetrically installed in the installation cavity (201) both sides of the support plate (2011), and the support plate (2011) is provided with elastic element between, end opening has through slot (4022); Two front push scraper (403), with the transmission rod (402) one to one correspondence, and slidingly installed in the through slot (4022).

5. The loess tunnel support structure according to claim 4, characterized in that, The side push assembly comprises: Two lower side push plate (404), symmetrically installed in the both sides of the central axis of the support plate (2011), each lower side push plate (404) through the pulley (6) and transmission assembly sliding connection; Two upper side push plate (405), with the lower side push plate (404) one to one correspondence, installed on the opposite side of the lower side push plate (404).

6. The loess tunnel support structure according to claim 1, wherein The transmission assembly comprises: Driving wheel (7), the outer periphery is provided with a first prism; Two driven wheels (8), with the driving wheel (7) located in the same horizontal plane, rotationally installed in the installation cavity (201), the outer periphery is provided with a second prism (801).

7. The loess tunnel support structure according to claim 6, characterized in that, The driving wheel (7), two driven wheels (8) along the cross section of the pipe shed assembly (3) are arranged in turn, and the middle driven wheel (8) is periodically engaged with the driving wheel (7) and the other driven wheel (8) through the second prism (801).

8. The loess tunnel support structure according to claim 1, characterized in that, The tunneling mechanism (4) further comprises: Two advance turntable (401), symmetrically rotationally installed in the both sides of the front push assembly, each advance turntable (401) is connected with the transmission assembly through the belt, and the outer periphery is provided with a prismatic tooth.

9. A loess tunnel support construction method, characterized by, The steps include: S1, in the tunnel portal construction with oval structure guide hole (101) guide wall (1); S2, the pipe shed assembly (3) is pushed into along the guide hole (101), the advance turntable (401), front push scraper (403) and side push plate of tunneling mechanism (4) are driven by transmission assembly during the pushing process, and the active excavation and soil dredging are carried out; S3, after the pipe roof assembly (3) is jacked into place, the independent areas formed by the partition plate (302) are partition grouting, and the slurry penetrates into the loess cracks through the grouting holes (3011) on the outer periphery of the pipe body (301); S4, after all the pipe roof assemblies (3) are grouted and the slurry is solidified, tunnel excavation operation is performed.

10. The loess tunnel support construction method according to claim 9, characterized by, The jacking process in S2 is specifically as follows: Through the operation of the driving transmission assembly, the driving wheel (7) and the driven wheel (8) periodically mesh to transmit power, driving the jacking turntable (401) to rotate and break the obstacles in front, while the driven wheel (8) drives the transmission rod (402) of the front pushing assembly to swing, making the front pushing scraper (403) reciprocate to push the soil, and the lower side pushing plate (404) and the upper side pushing plate (405) of the side pushing assembly to dredge the soil to the two sides, realizing active excavation and low disturbance jacking.

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