A shotcrete flatness control system

Abstract

The utility model relates to a kind of shotcrete flatness control system, by the longitudinal interval multiple cross sections of tunnel are set up steel pipe arch, steel pipe arch is fixed in the surrounding rock inner wall of corresponding cross section, so that steel pipe arch is along the circumferential setting of corresponding cross section of tunnel, and ensure that the inside of steel pipe arch is equal with the chord height of tunnel to be constructed primary support inside surface, so that it can provide shotcrete reference standard using the inside of steel pipe arch, wet spray hand of guniting can easily observe arch top guniting flatness condition according to the inside of steel pipe arch, improve the control of wet spray machine operator to arch top position injection effect, so that the primary support flatness of III grade, IV grade surrounding rock not erecting steel frame section has been obviously improved, improve primary support flatness qualification rate and primary support apparent quality;And by the inside of steel pipe arch control primary support flatness, reduce primary support invasion line, and avoid the lining cavity, insufficient thickness caused by primary support flatness deficiency, provide favorable conditions for later drainage construction and lining construction.

Description

Technical Field

[0001] This utility model relates to the field of shotcrete flatness control technology, and in particular to a shotcrete flatness control system. Background Technology

[0002] In tunnel construction, when the surrounding rock is Class III or Class IV, steel arch frames are generally not designed for the initial support. Tunnel sections without steel arch frames are called "no-steel-frame sections." During the construction of these sections, excavation and initial support construction are entirely carried out by manual labor combined with large machinery. The meshing and shotcreting rely entirely on the large machinery to provide the working space. However, the wet shotcreting operator cannot observe the smoothness of the shotcreting at the arch crown from a distance of about 8 meters. In addition, the reduced visibility at the tunnel face during shotcreting makes it even more difficult for the shotcreting operator to grasp the specific condition of the shotcreting surface. This results in unevenness on the initial support surface, a reduced pass rate for initial support smoothness, and seriously restricts the physical and surface quality of the initial support. Utility Model Content

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology in which, when the steel frame section is not erected during construction, the wet sprayer cannot observe the flatness of the sprayed grout on the arch top, resulting in unevenness on the initial support surface and a reduced pass rate for the flatness of the initial support. This seriously restricts the physical and surface quality of the initial support. The invention provides a sprayed concrete flatness control system.

[0004] In a first aspect, this utility model provides a shotcrete smoothness control system, comprising:

[0005] The steel pipe arch is set at multiple cross sections spaced longitudinally along the tunnel. The steel pipe arch is set circumferentially along the corresponding cross sections of the tunnel and is fixed to the inner wall of the surrounding rock of the corresponding cross sections.

[0006] The inner side of the steel pipe arch is equal to the chord height of the inner side of the initial support to be constructed in the tunnel.

[0007] The shotcrete flatness control system described in this utility model provides a shotcrete reference standard by utilizing the inner side of the steel pipe arch. The wet shotcrete operator can easily observe the flatness of the shotcrete at the top of the arch based on the inner side of the steel pipe arch, improving the operator's control over the shotcrete effect at the top of the arch. This significantly improves the flatness of the initial support in Class III and IV surrounding rock without steel frame sections, increasing the pass rate and appearance quality of the initial support. Furthermore, by controlling the flatness of the initial support from the inner side of the steel pipe arch, it reduces the encroachment of the initial support line and avoids lining voids and insufficient thickness caused by insufficient initial support flatness, providing favorable conditions for subsequent waterproofing and drainage construction and lining construction.

[0008] Preferably, the distance between two adjacent steel pipe arches arranged along the longitudinal direction of the tunnel is less than or equal to the longitudinal distance between the anchor bolts; some or all of the steel pipe arches are set with corresponding anchor bolts, and the steel pipe arches set with corresponding anchor bolts are welded to the head of the corresponding anchor bolts;

[0009] When some of the steel pipe arches are set with anchor bolts, and the steel pipe arches that are not set with anchor bolts are welded to the exposed steel bar ends of the steel bars implanted into the inner wall of the surrounding rock, the depth of the steel bars implanted is greater than or equal to 30cm and the diameter of the steel bars is greater than or equal to 12mm.

[0010] Using the above method, the anchor heads can be used to fix the corresponding steel pipe arches, resulting in high installation stability. This avoids the need for extensive or even no reinforcement bars being implanted into the inner wall of the surrounding rock, reducing construction workload and costs. Furthermore, it does not affect the quality of the inner rock wall, thus enhancing its safety. This longitudinally spaced arrangement of the steel pipe arches also allows for better control of the initial support flatness after shotcreting.

[0011] Preferably, the steel pipe arch is divided into several arc-shaped segments in the circumferential direction. The two ends of each arc-shaped segment are sealed by connecting steel plates, and adjacent arc-shaped segments are connected by connecting steel plates. The inner side of all the arc-shaped segments is equal to the chord height of the inner side of the initial support to be constructed in the tunnel.

[0012] The processing is simpler, and it is easier to control the inner side of the arc segment to be equal to the chord height of the inner side of the initial support to be constructed in the tunnel.

[0013] Preferably, the connecting steel plates between adjacent arc segments are connected by bolts, which facilitates connection and installation.

[0014] Preferably, the length of the connecting steel plate is arranged along the longitudinal direction of the tunnel, and the width of the connecting steel plate is arranged along the radial direction of the steel pipe arch, which facilitates longitudinal connection by bolts and avoids the connecting steel plate encroaching on the line.

[0015] Preferably, the elevation of the side of the connecting steel plate facing the tunnel is equal to the chord height of the inner side of the initial support to be constructed in the tunnel. This allows the side of the connecting steel plate facing the tunnel to guide the spraying of the initial support concrete, increasing the guidance area and helping to control the flatness of the initial support after spraying concrete.

[0016] Preferably, the arc segment is unit A or unit B, with unit B located at both ends of the steel pipe arch and unit A located between the two ends of the steel pipe arch. Unit A located at the top of the steel pipe arch is symmetrically arranged along the longitudinal central axis of the tunnel, and units A located on both sides of the longitudinal central axis of the tunnel are arranged opposite each other. Unit B located on both sides of the longitudinal central axis of the tunnel are arranged opposite each other.

[0017] The steel pipe arch is set in a symmetrical manner, which makes its stress capacity better, reduces the deformation caused by the impact of shotcrete, improves its stability, and makes it easier to process.

[0018] Preferably, the diameter of the arc segment is 40mm-42mm, and the wall thickness of the arc segment is greater than or equal to 3mm, so as to reduce the deformation caused by the impact of sprayed concrete and improve its stability.

[0019] Preferably, the elevations at both ends of the steel pipe arch are higher than the elevations of the sidewalls of the tunnel.

[0020] Preferably, the steel pipe arch is symmetrically arranged about the longitudinal central axis of the tunnel. This symmetrical arrangement of the steel pipe arch improves its load-bearing capacity, reduces deformation caused by the impact of shotcrete, and enhances its stability.

[0021] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0022] This invention provides a shotcrete smoothness control system. It involves installing steel pipe arches at multiple longitudinally spaced cross sections of the tunnel and fixing these arches to the inner wall of the surrounding rock at the corresponding cross sections. This ensures the steel pipe arches are circumferentially positioned along the corresponding cross sections of the tunnel, and that the inner side of the steel pipe arch has the same chord height as the inner side of the initial support to be constructed in the tunnel. This allows the inner side of the steel pipe arch to provide a reference standard for shotcrete. The wet shotcrete operator can easily observe the smoothness of the shotcrete at the arch top based on the inner side of the steel pipe arch, improving the operator's control over the shotcrete effect at the arch top. This significantly improves the smoothness of the initial support in Class III and IV surrounding rock sections without steel frames, increasing the pass rate and appearance quality of the initial support. Furthermore, controlling the smoothness of the initial support through the inner side of the steel pipe arch reduces encroachment on the initial support line and avoids lining voids and insufficient thickness caused by insufficient initial support smoothness, providing favorable conditions for subsequent waterproofing and drainage construction and lining construction. Attached Figure Description

[0023] Figure 1 This is a cross-sectional schematic diagram of the shotcrete smoothness control system.

[0024] Figure 2 This is a longitudinal section schematic diagram of the shotcrete smoothness control system.

[0025] Figure 3 This is a schematic diagram of a steel pipe arch structure;

[0026] Figure 4 This is a schematic diagram showing the connection between the arc segments of a steel pipe arch unit.

[0027] Marked in the diagram: 1. Steel pipe arch; 111. Unit A; 112. Unit B; 12. Connecting steel plate; 2. Tunnel; 21. Inner wall of surrounding rock; 22. Side wall. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments. However, it should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0029] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of this utility model is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the utility model product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the utility model solution or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on this utility model.

[0030] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," "parallel," and "coaxial" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, parallel, or coaxial. Slight tilt or deviation is permissible, as long as it does not affect the normal function of the relevant component. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," not that the structure must be perfectly horizontal; a slight tilt is acceptable. "Coaxial" means that two components are set as coaxially as possible, allowing them to move coaxially or approximately coaxially when their relative positions change. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," "parallel," or "coaxial" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. For example, the deviation in the "coaxial" direction is controlled within 0.2-1mm, preferably within 0.2-0.5mm. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0031] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0032] Furthermore, in the description of the embodiments of this utility model, "several", "multiple", and "several" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0033] Furthermore, in the description of the technical solution of this utility model, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "equipped with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0034] Example 1

[0035] like Figure 1 and Figure 2 As shown, a shotcrete smoothness control system includes: steel pipe arches 1 set at multiple cross-sections spaced longitudinally along the tunnel 2; the steel pipe arches 1 are arranged circumferentially along the corresponding cross-sections of the tunnel 2; the steel pipe arches 1 are fixed to the inner wall 21 of the surrounding rock of the corresponding cross-section; the inner side of the steel pipe arches 1 is equal to the chord height of the inner side of the initial support to be constructed in the tunnel 2; the inner side of the steel pipe arches 1 serves as a control mark for the shotcrete operator to observe the smoothness of the initial support shotcrete.

[0036] Compared to using a single, integral steel pipe arch 1, directly controlling the inner chord height of the entire steel pipe arch 1 is more difficult. In an optional embodiment, the steel pipe arch 1 is divided into several arc-shaped segments in the circumferential direction, such as... Figure 3 As shown, both ends of each arc segment are sealed by connecting steel plates 12 to prevent the initial support shotcrete from entering the arc segment; adjacent arc segments are connected by connecting steel plates 12, and the inner side of all the arc segments is equal to the chord height of the inner side of the initial support to be constructed in tunnel 2. This control of the inner chord height of the arc segments simplifies the manufacturing process and makes it easier to control the inner side of the arc segments to be equal to the chord height of the inner side of the initial support to be constructed in tunnel 2. Furthermore, the connecting steel plates 12 between adjacent arc segments are connected by bolts 13, such as... Figure 4 As shown, compared to welding, its connection and installation are more convenient. The length of the connecting steel plate 12 is set along the longitudinal direction of the tunnel 2, and the width of the connecting steel plate is set along the radial direction of the steel pipe arch 1. That is, the length of the connecting steel plate 12 set along the longitudinal direction of the tunnel 2 is greater than the width of the connecting steel plate set along the radial direction of the steel pipe arch 1, so that two connecting steel plates can be connected in the longitudinal direction of the tunnel 2 by bolts 13, thereby connecting two adjacent circumferential arc segments, and avoiding the connecting steel plate 12 from encroaching on the radial line.

[0037] Furthermore, by using the connecting steel plate 12 to guide the spraying of the initial support concrete on one side of the tunnel 2, the elevation of the connecting steel plate 12 on the side of the tunnel 2 facing the tunnel 2 is equal to the chord height of the inner side of the initial support to be constructed in the tunnel 2. This increases the guiding area and helps control the flatness of the initial support after spraying concrete.

[0038] In optional implementations, such as Figures 1-3 As shown, the arc-shaped segment is either unit A 111 or unit B 112. Unit B 112 is located at both ends of the steel pipe arch 1, and unit A 111 is located between the two ends of the steel pipe arch 1. Unit A 111 located at the top of the steel pipe arch 1 is symmetrically arranged along the longitudinal central axis of the tunnel 2. Unit A 111 located on both sides of the longitudinal central axis of the tunnel 2 are arranged opposite each other, and units B 112 located on both sides of the longitudinal central axis of the tunnel 2 are arranged opposite each other. The steel pipe arch 1 is formed by connecting steel plates 12 using units A 111 and B 112, which makes processing more convenient. Furthermore, the steel pipe arch 1 is arranged in a transversely symmetrical manner, that is, the steel pipe arch 1 is symmetrical about the longitudinal central axis of the tunnel 2, which improves its stress resistance, reduces deformation caused by the impact of shotcrete, and enhances its stability.

[0039] In this embodiment, the diameter of the arc segment is 40mm-42mm, and the wall thickness of the arc segment is greater than or equal to 3mm, which can reduce the deformation of the steel pipe arch 1 after being impacted by shotcrete and improve its stability.

[0040] In an optional embodiment, the elevations of both ends of the steel pipe arch 1 are higher than the elevations of the sidewalls 22 of the tunnel 2.

[0041] In this embodiment, the steel pipe arch 1 is fixed to the inner wall 21 of the surrounding rock in the corresponding cross section, and it is necessary to ensure stable fixation. Various existing fixing methods in tunnels can be adopted. In an optional embodiment, the distance between two adjacent steel pipe arches 1 arranged along the longitudinal direction of the tunnel 2 is less than or equal to the longitudinal distance of the anchor bolts. This longitudinal spacing arrangement of the steel pipe arches 1 can better control the initial support flatness after shotcreting. Some steel pipe arches 1 are set with corresponding anchor rods. The steel pipe arches 1 set with the anchor rods are welded to the head of the corresponding anchor rods. The steel pipe arches 1 not set with the anchor rods are welded to the exposed head of the reinforcing bars implanted in the inner wall 21 of the surrounding rock. The depth of the reinforcing bars implanted is greater than or equal to 30cm and the diameter of the reinforcing bars is greater than or equal to 12mm. Alternatively, all steel pipe arches 1 are set with corresponding anchor rods. All steel pipe arches 1 are welded to the head of the corresponding anchor rods. Using the above method, the head of the anchor rod can be used to fix the corresponding steel pipe arches 1. The installation stability is high. It avoids the need to implant a lot of reinforcing bars in the inner wall 21 of the surrounding rock or to implant no reinforcing bars in the inner wall 21 of the surrounding rock. It can reduce the amount of construction work and reduce the construction cost. Moreover, it will not affect the quality of the surrounding rock of the inner wall 21 of the surrounding rock, so that the safety of the inner wall 21 of the surrounding rock is higher.

[0042] This invention provides a shotcrete flatness control system, which utilizes the inner side of the steel pipe arch 1 as a reference standard for shotcrete. The wet shotcrete operator can easily observe the flatness of the shotcrete at the top of the arch based on the inner side of the steel pipe arch 1, improving the operator's control over the shotcrete effect at the top of the arch. This significantly improves the flatness of the initial support in Class III and IV surrounding rock without steel frame sections, increasing the pass rate and appearance quality of the initial support. Furthermore, by controlling the flatness of the initial support from the inner side of the steel pipe arch, the encroachment of the initial support line is reduced, and lining voids and insufficient thickness caused by insufficient initial support flatness are avoided, providing favorable conditions for subsequent waterproofing and drainage construction and lining construction.

[0043] When using this shotcrete smoothness control system to construct the initial support of a tunnel section without an arch frame, the construction details are as follows:

[0044] 1. Construction preparation: Purchase sufficient φ42mm×3.5mm curved steel pipe, 6mm thick connecting steel plate 12 and M16×40mm bolts according to the plan, conduct visual inspection and verification, and conduct timely material testing to ensure that the materials are qualified.

[0045] 2. Steel Pipe Arch Fabrication: Considering that the excavation radius and lining construction equipment radius within the tunnel are both 5cm larger than the design, and taking into account the deformation of the steel pipe arch during the shotcrete re-spraying process, the steel pipe arch is fabricated at the rebar fabrication yard according to the inner radius of the steel pipe arch. For Class III surrounding rock without a steel frame, the inner diameter is 405cm, and for Class IV surrounding rock without a steel frame, the inner diameter is 410cm. Each steel pipe arch is 13 meters long and consists of 5 assembled segments: Unit A has 3 segments, each 3 meters long; Unit B has 2 segments, each 2 meters long. The units are connected using connecting steel plates and bolts. The steel pipe end is tightly fitted to the connecting steel plate and then fully welded to form the unit. Each connecting steel plate is a 5mm thick steel plate (material head), 20cm long and 6cm wide. The connecting steel plates of two units are spliced ​​together and then bolted together with M16×40mm bolts. Each splice point is fixed with two bolts. Furthermore, after every 20 rings of steel pipe arch fixtures are processed, one ring is randomly selected for inspection and trial assembly at the steel reinforcement yard. The inner chord length and chord height of the steel pipe arch fixture after trial assembly are then checked. If the deviation is too large, the processing dimensions are adjusted in a timely manner to minimize the processing error.

[0046] Materials required for one cycle of support:

[0047] D42 steel pipe: 3.32 × 13 × 2 = 86.32 kg;

[0048] φ22 threaded steel bar: 2.98×9×2×1.6=85.82kg;

[0049] 5mm thick connecting steel plate: 39.25×8×0.06×0.2=3.768kg;

[0050] 3. Measurement and Setting Out: Since the longitudinal spacing of the anchor bolts in the Class III and IV surrounding rock of the tunnel is 1.5m, the on-site installation of the steel pipe arch is controlled by measurement and setting out according to the longitudinal spacing of no more than 1.5m. The measurement, setting out and installation of the steel pipe arch can be carried out along the mileage of the anchor bolt construction. The anchor bolt head is effectively used as the positioning and fixing point. The positioning spatial information of the steel pipe arch is marked on the surrounding rock at the corresponding installation position of the steel pipe arch, and the on-site measurement instructions are given to the construction workers.

[0051] The installation location of the steel pipe arch fixture must be marked with no fewer than 7 points. Three points should be precisely marked at the center of the arch top and the left and right pipe feet of the fixture. The remaining four points should be precisely marked at the locations of the steel pipe splicing connection plates, i.e., two points on each side. All measurements and markings should be conducted using a lifting trolley or a three-arm drilling jumper with a hanging basket.

[0052] 4. Positioning and assembly of steel pipe arch fixtures: The steel pipe arch fixtures are constructed in accordance with the initial support progress of the working face.

[0053] The on-site positioning and installation of steel pipe arch fixtures can be carried out by: assembling the steel pipe arch in one go, hoisting it to the predetermined position as a whole, and then reinforcing and welding it point by point after overall positioning; or by assembling and positioning the arch segments one by one.

[0054] The installation position of the steel pipe arch fixture fully utilizes the head of the circumferential anchor rod of the same cross section as the fixing point for welding. When the position of the local anchor rod is deviated and cannot be used, a hand-held electric drill is used to drill a hole at the fixing point. The hole depth is not less than 30cm, and a steel bar with a diameter of not less than 12mm is hammered into the hole. Finally, the exposed steel bar head is fixedly welded to the steel pipe arch fixture.

[0055] The positioning and assembly of the steel pipe arch were carried out using a lifting trolley or a three-arm rock drilling trolley with a hanging basket.

[0056] 5. Acceptance of steel pipe arch installation fixtures:

[0057] For the steel pipe arch fixtures that have been positioned and welded, the surveyors used measuring instruments to remeasure units A and B.

[0058] Surveyors used a total station to re-measure the installation position of the steel pipe arch, and accurately re-measured the middle position of the arch top and the position of the pipe feet of each unit of the steel pipe arch fixture (a total of 7 points) to ensure that the steel pipe arch does not encroach on the line.

[0059] 6. Initial spraying and leveling:

[0060] After the installation and acceptance of the steel pipe arch fixture for controlling the flatness of the tunnel's initial support are completed, and it is confirmed that the fixture's spatial position is correct and does not encroach on the line, the initial support shotcrete re-spraying process will commence. During the initial support shotcrete re-spraying process, the sidewalls must be sprayed first, followed by the arch crown, and the spraying must be completed in layers. That is, the left and right arch foot positions are sprayed first, followed by the arch waist, and finally the arch crown. If there is over-excavation, the over-excavated area is sprayed first, and steel mesh or multiple layers of shotcrete are added to the over-excavated area as needed.

[0061] Taking advantage of the time for concrete mixer truck changes and passing, the wet spraying machine nozzle with scraper, using the steel pipe arch fixture as a reference surface, scrapes off excess shotcrete along the inside of the steel pipe arch. After the shotcrete is re-sprayed onto the initial support surface of the cycle, the wet spraying machine nozzle with scraper is used again to finely scrape off excess shotcrete along the inside of the steel pipe arch to ensure that the flatness of the initial support meets the standard after re-spraying.

[0062] Quality standards and control measures:

[0063] 1. Steel pipe arches must be processed strictly according to the designed radius and length;

[0064] 2. Ensure the chamfer at the weld between the unit and the connecting steel plate to ensure the overall curvature of the steel pipe arch after assembly;

[0065] 3. The cross-section of the steel pipe arch and the connecting steel plate should be fully welded;

[0066] 4. When installing the steel pipe arch fixtures, the bolts at the connecting steel plates of each unit should be tightened.

[0067] 5. The installed steel pipe arch fixture should be stable and free from encroachment.

[0068] The benefits of using the shotcrete smoothness control system provided in this embodiment are analyzed as follows:

[0069] 1. Social benefits

[0070] The application of the shotcrete flatness control system has greatly reduced the waste of shotcrete and saved resources; reduced the dust generated by milling the initial support and under-excavation, thus improving the construction environment inside the tunnel; improved the appearance quality of the initial support; improved the overall flatness of the waterproof layer and improved the waterproof quality of the lining; and consequently reduced the number of lining defects caused by unevenness of the initial support, greatly improving the overall quality of tunnel construction and resulting in significant social benefits.

[0071] 2. Economic benefits

[0072] The use of the shotcrete flatness control system reduces excessive concrete consumption in the milling of the initial support line, thus reducing concrete waste; it also reduces the difficulty of laying the steel mesh in the section without arches, reduces the time required for laying the steel mesh, accelerates the construction progress, and has significant economic benefits.

[0073] (1) The adoption of a shotcrete smoothness control system reduces construction time.

[0074] When the shotcrete flatness control system is not used, the flatness is mainly treated by multiple spraying, fine spraying, milling and leveling. Based on previous experience and data, after multiple sprayings, the spraying section is generally 30 meters long, each time taking about 6 hours. Each section needs to be sprayed 2-3 times. It is calculated that each cycle is affected by about 2 hours due to the spraying.

[0075] After multiple rounds of spraying, the initial support surface was severely under-excavated, requiring milling treatment. According to the actual records of the inlet and cross tunnel processes, when steel pipe arches were not used, the treatment was carried out once every 30 linear meters, with each treatment taking about 10.5 hours. On average, each cycle of treating the under-excavation of the initial support consumed 1 hour and 10 minutes.

[0076] Comprehensive data analysis shows that before adopting steel pipe arch construction, the initial support flatness control and handling of over- and under-excavation resulted in a delay of 3 hours and 10 minutes per cycle. Currently, based on tunnel entrance experience and records, the installation time for steel pipe arches is approximately 2 hours, with the most recent process time controlled at 1.5-2 hours. Based on a 2-hour calculation, using steel pipe arches (with small guide pipe positioning rings) can save 1 hour and 10 minutes of process time. According to the actual construction efficiency of the project, the total cost saving in labor and machine shifts per linear meter is 466.67 yuan.

[0077] (2) Material and processing costs of steel pipe arches:

[0078] ① Steel pipe arch fixtures for Class III surrounding rock (without arch frame section):

[0079] Steel pipes for each steel pipe arch: (2.829m×3+2m×2)×3.323kg / m=41.49kg;

[0080] Connecting steel plates for the steel pipe arch: 0.2m × 0.016m × 0.006m × 8 pieces × 7850kg / m³ = 1.206kg;

[0081] Φ22 connecting steel bars: 9 bars × 1.5m × 2.984kg / m = 40.23kg;

[0082] Bolts: 16 sets of M16*60mm.

[0083] The spacing between steel pipe arches is 1.5m / arch; the processing and material cost of the steel pipe arch is 6500 yuan / ton; the processing and material cost of the connecting steel bars is 5500 yuan / ton; the connecting steel plates use leftover scraps, and the material and processing cost is calculated at 3300 yuan / ton. Bolts cost 7 yuan per set; therefore, the processing and material cost per linear meter of steel pipe arch increases by:

[0084] (41.49kg × 6500 yuan / ton ÷ 1000 + 40.23kg × 5500 yuan / ton ÷ 1000 + 1.206kg × 3300 yuan / ton ÷ 1000 + 16 × 7 yuan) ÷ 1.5m / piece = 404.62 yuan;

[0085] ② Steel pipe arch fixtures for Class IV surrounding rock (without arch frame section):

[0086] Steel pipes for each steel pipe arch: (2.862m×3+2m×2)×3.323kg / m=41.82kg;

[0087] Connecting steel plates for the steel pipe arch: 0.2m × 0.016m × 0.006m × 8 pieces × 7850kg / m³ = 1.206kg;

[0088] Φ22 connecting steel bars: 9 bars × 1.5m × 2.984kg / m = 40.23kg;

[0089] Bolts: 16 sets of M16*40mm.

[0090] The spacing between steel pipe arches is 1.5m / arch; the processing and material cost of the steel pipe arch is 6500 yuan / ton; the processing and material cost of the connecting steel bars is 5500 yuan / ton; the connecting steel plates use leftover scraps, and the material and processing cost is calculated at 3300 yuan / ton. Bolts cost 7 yuan per set; therefore, the processing and material cost per linear meter of steel pipe arch increases by:

[0091] (41.82kg × 6500 yuan / ton ÷ 1000 + 40.23kg × 5500 yuan / ton ÷ 1000 + 1.206kg × 3300 yuan / ton ÷ 1000 + 16 × 7 yuan) ÷ 1.5m / piece = 406.04 yuan;

[0092] (3) The use of steel pipe arch fixtures reduced the consumption of shotcrete in Class III and IV surrounding rock sections without steel frames. Without this fixture, multiple re-spraying and milling processes were required, resulting in a very high over-consumption rate of shotcrete. According to statistical data analysis, the use of steel pipe arch fixtures reduced the over-consumption rate of shotcrete by 40.2% (relative to the design consumption) in Class III surrounding rock sections without steel frames; and by 25.6% (relative to the design consumption) in Class IV surrounding rock sections without steel frames. The cost savings per linear meter after using steel pipe arch fixtures are analyzed as follows:

[0093] Class III surrounding rock (without arch frame): Concrete volume saved: (0.96+0.78)×52.2%=0.908m³, cost saved: 0.908m³×640 yuan / m³=581.12 yuan.

[0094] Class IV surrounding rock (without arch frame): Concrete volume saved: 3.29 × 25.6% = 0.84 m³, cost saved: 0.84 m³ × 900 yuan / m³ = 758 yuan.

[0095] (4) Comprehensive calculation:

[0096] The cost savings for Class III surrounding rock (without arch support section) are: 466.67 - 404.62 + 581.12 = 643.17 yuan;

[0097] The cost savings for Class IV surrounding rock (without arch support section) are: 466.67 - 406.04 + 756 = 816.63 yuan;

[0098] In summary, the application of the shotcrete flatness control system provides wet sprayers with a clear reference mark for the initial support flatness, making it easier to control the shotcrete thickness at various points during the shotcrete process and improving the pass rate of initial support flatness. It also improves the overall flatness of the waterproofing layer, enhances the waterproofing quality of the lining, reduces lining defects, and effectively improves the physical quality of the initial support and secondary lining, as well as the appearance quality of the initial support.

[0099] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A shotcrete smoothness control system, characterized in that, include: A steel pipe arch (1) is provided at multiple cross sections spaced longitudinally along the tunnel (2). The steel pipe arch (1) is arranged circumferentially along the corresponding cross section of the tunnel (2). The steel pipe arch (1) is fixed to the inner wall (21) of the surrounding rock of the corresponding cross section. The inner side of the steel pipe arch (1) is equal to the chord height of the inner side of the initial support to be constructed of the tunnel (2).

2. The shotcrete smoothness control system according to claim 1, characterized in that, The distance between two adjacent steel pipe arches (1) arranged along the longitudinal direction of the tunnel (2) is less than or equal to the longitudinal distance between the anchor rods; some or all of the steel pipe arches (1) are set with corresponding anchor rods, and the steel pipe arches (1) set with corresponding anchor rods are welded to the rod head of the corresponding anchor rod; When a portion of the steel pipe arch (1) is set with an anchor rod, the exposed steel bar head of the steel pipe arch (1) that is not set with an anchor rod is welded to the inner wall (21) of the surrounding rock. The depth of the steel bar implantation is greater than or equal to 30cm and the diameter of the steel bar is greater than or equal to 12mm.

3. The shotcrete smoothness control system according to claim 1, characterized in that, The steel pipe arch (1) is divided into several arc segments in the circumferential direction. The two ends of each arc segment are sealed by connecting steel plates (12). Adjacent arc segments are connected by connecting steel plates (12). The inner side of all the arc segments is equal to the inner chord height of the initial support of the tunnel (2) to be constructed.

4. The shotcrete smoothness control system according to claim 3, characterized in that, The connecting steel plates (12) between adjacent arc segments are connected by bolts (13).

5. A shotcrete smoothness control system according to claim 4, characterized in that, The length of the connecting steel plate (12) is arranged along the longitudinal direction of the tunnel (2), and the width of the connecting steel plate is arranged along the radial direction of the steel pipe arch (1).

6. A shotcrete smoothness control system according to claim 5, characterized in that, The elevation of the side of the connecting steel plate (12) facing the tunnel (2) is equal to the chord height of the inner side of the initial support to be constructed in the tunnel (2).

7. A shotcrete smoothness control system according to claim 3, characterized in that, The arc segment is either unit A (111) or unit B (112). Unit B (112) is located at both ends of the steel pipe arch (1). Unit A (111) is located between the two ends of the steel pipe arch (1). Unit A (111) located at the top of the steel pipe arch (1) is symmetrically arranged along the longitudinal central axis of the tunnel (2). Unit A (111) located on both sides of the longitudinal central axis of the tunnel (2) is arranged opposite to each other. Unit B (112) located on both sides of the longitudinal central axis of the tunnel (2) is arranged opposite to each other.

8. A shotcrete smoothness control system according to claim 3, characterized in that, The diameter of the arc segment is 40mm-42mm, and the wall thickness of the arc segment is greater than or equal to 3mm.

9. A shotcrete smoothness control system according to any one of claims 1-8, characterized in that, The elevations at both ends of the steel pipe arch (1) are higher than the elevations of the sidewalls (22) of the tunnel (2).

10. A shotcrete smoothness control system according to any one of claims 1-8, characterized in that, The steel pipe arch (1) is symmetrically arranged about the longitudinal central axis of the tunnel (2).

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