Highway tunnel thin-wall composite reinforcing structure and design method
By designing a thin-walled composite reinforcement structure for highway tunnels, and using precast concrete structures for the thinned section and main support section, combined with concrete materials with different compressive strengths, the problem of frequent tunnel defects was solved, the compressive strength and load-bearing capacity of the tunnel were improved, the passage space was optimized, and the construction safety and stability were ensured.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA MERCHANTS CHONGQING COMM RES & DESIGN INST
- Filing Date
- 2025-03-17
- Publication Date
- 2026-06-23
AI Technical Summary
As existing highway tunnels age, they frequently suffer from defects, affecting their compressive strength, load-bearing capacity, and traffic space. Furthermore, it is difficult to optimize traffic space while improving compressive strength and load-bearing capacity during tunnel design.
The highway tunnel adopts a thin-walled composite reinforcement structure, which includes multiple sets of reinforcement segments. Through the precast concrete structure design of the thinning section and the main support section, and combined with concrete materials with different compressive bearing capacities, an NC-UHPC-NC composite reinforcement is formed. The reinforcement area is determined by the equal compressive strength method and the ultimate bending value M. The transition section is gradually thickened, and the location and size of the holes are designed to achieve the assembly connection.
To improve the tunnel's compressive strength and bearing capacity, optimize traffic space, shorten the construction period, overcome the risk of structural settlement, ensure construction safety and stability, enhance interface bonding, and improve the overall structural performance of the tunnel.
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Figure CN119981973B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of tunnel technology, specifically to thin-walled composite reinforcement structures and design methods for highway tunnels. Background Technology
[0002] With the continuous advancement of infrastructure construction in transportation, water conservancy, and other fields, the demand for tunnel engineering is increasing daily. As vital transportation channels, tunnels face increasingly stringent requirements for construction technology and quality. Simultaneously, with the ongoing development of highway tunnel projects, many projects have transitioned from the construction phase to the operation and maintenance phase. As tunnels age, potential defects in their design and construction gradually surface, leading to frequent occurrences of tunnel defects. These defects, such as cracking, water seepage, and lining spalling, can, in mild cases, impair the tunnel's visual aesthetics and distract drivers, while severe defects can directly trigger collapses, falls, and other safety accidents, causing significant economic losses and negative social impacts. Therefore, improving the compressive strength, load-bearing capacity, and structural durability of tunnels during the design and construction phases has become a key technical issue for ensuring the long-term safe operation of tunnels.
[0003] Furthermore, from the perspective of tunnel functional requirements, the effective space available for passage within the tunnel is a crucial indicator for evaluating its design rationality. Maximizing the effective space within the tunnel, while ensuring structural safety and durability, has become another significant technical challenge in tunnel design and construction. Therefore, optimizing tunnel cross-section design to expand passage space while simultaneously improving the tunnel's compressive strength and load-bearing capacity to extend its service life is a core technical issue that urgently needs to be addressed in the field of tunnel engineering. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a thin-walled composite reinforcement structure and design method for highway tunnels, which can improve the tunnel's compressive strength and bearing capacity while increasing its usable passage space.
[0005] To achieve the above objectives, the present invention provides a thin-walled composite reinforcement structure for highway tunnels, comprising:
[0006] The system comprises multiple sets of reinforced segments, which are sequentially spliced along the length of the tunnel. Each set of reinforced segments includes two segments, which are connected at the top and staggered left and right. The bottom of each reinforced segment is connected to the tunnel's internal beam. The reinforced segments are precast concrete structures. Each reinforced segment includes a thinned section and a main support section connected to both sides of the thinned section. The thinned section is 4-5 meters above the ground, and its thickness is less than that of the main support section. The thinned section and the main support section have the same normal compressive bearing capacity. Each reinforced segment has holes for hoisting, grouting, or connection.
[0007] Furthermore, the reinforced segments are divided into wide reinforced segments and narrow reinforced segments, with the width of the wide reinforced segments being twice that of the narrow reinforced segments, along the length of the tunnel.
[0008] Furthermore, the thinning portion includes a central thin portion and transition portions located on both sides, wherein the transition portions gradually thicken from the center to both sides.
[0009] Furthermore, the inner surface of the thinned portion is reinforced.
[0010] Furthermore, the holes include hoisting holes, grouting holes, anchoring holes, bottom support holes, top bolt holes, hand holes, longitudinal quick-connect bolt holes, longitudinal prestressing holes, and positioning tenon holes:
[0011] The lifting holes are located on both sides, as well as the inner and outer sides of the reinforced pipe segment. The number of lifting holes on a single side should not be less than two, and they should be arranged symmetrically along the axis of symmetry where the center of gravity is located.
[0012] The grouting holes are evenly distributed on the edge or surface of the reinforced pipe segment, with a circumferential spacing of 1.5m to 2m and a longitudinal spacing of 0.5m to 1m.
[0013] The anchoring holes are evenly distributed along the joint between the reinforced pipe segment and the original lining, and the diameter of the anchoring holes is 30-50 mm larger than the diameter of the anchor cable.
[0014] The bottom support hole is located at the bottom of the reinforced pipe segment and is used to connect with the ground beam;
[0015] The top bolt holes are arranged along the middle of the thickness direction of the reinforced segment, and the hole size is equal to or less than 1 / 4 of the segment thickness;
[0016] The handhole is provided on the reinforced segment, and the width of the handhole along the circumferential direction of the tunnel is greater than or equal to 15cm, and the width of the handhole along the longitudinal direction of the tunnel is greater than or equal to 15cm.
[0017] The spacing between the longitudinal quick-connect bolt holes is 4–6 m;
[0018] The longitudinal prestressed holes are symmetrically arranged on both sides of the longitudinal quick-connect bolt holes, and the distance between them and the quick-connect bolt holes makes the entire structure more stable.
[0019] The positioning tenon holes are provided on the longitudinal side of each of the reinforced tube segments.
[0020] A design method for a thin-walled composite reinforcement structure for highway tunnels, used to design the aforementioned thin-walled composite reinforcement structure for highway tunnels, characterized in that it includes:
[0021] Based on the concrete structural properties used in both the thinned section and the main support section connected to both sides of the thinned section, the thickness of the thinned section and the main support section is determined using the isobaric strength method.
[0022] The area of reinforcement at the thinned section is calculated using the ultimate bending strength value M.
[0023] The dimensions of the transition section are designed using a gradually thickening method;
[0024] An uneven surface is used to design and reinforce the interface of the pipe segments;
[0025] The location and size of the corresponding holes are designed according to the length and width of the tunnel, the casting method of the reinforcing segments, and the installation method of the reinforcing segments;
[0026] The method of assembly involves connecting multiple sets of reinforced segments sequentially along the length of the tunnel. Each set of reinforced segments includes two reinforced segments, with the tops of the two segments connected to each other and staggered left and right. The tops of the two reinforced segments are then connected to each other.
[0027] Furthermore, the determination of the local thinning thickness using the isobaric strength method is as follows:
[0028] Using the equal compressive strength method, the compressive bearing capacity of the thinned section is made consistent with that of the non-thinned section. The calculation formula for the thinned section is as follows:
[0029]
[0030] —The compressive strength of the first type of concrete
[0031] d1 — Thickness corresponding to the first type of concrete
[0032] —The compressive strength of the second type of concrete
[0033] d2 — the thickness corresponding to the second type of concrete.
[0034] Furthermore, the specific method for calculating the reinforcement area at the local thinning point using the ultimate bending strength value M is as follows:
[0035] The reinforcement of the strengthened structure is designed based on the "equal bending resistance" of the entire ring after reinforcement. During the calculation process, the existing tunnel structure is not considered because its contribution to the bending moment of the thinned and unthinned sections is similar. In determining the thickness, the bending resistance of the strengthened structure is first calculated using the unthinned section to determine the ultimate bending resistance value M. Based on this, the width of the compression zone concrete and the area of the reinforcing steel reinforcement are calculated using the aforementioned bending moment value M.
[0036] Furthermore, the specific method for designing the dimensions of the transition section by gradually increasing the thickness is as follows: the length of the transition section is 3 to 5 times the thickness of the interface.
[0037] Furthermore, it also includes roughening the surface of the reinforced segment.
[0038] The beneficial effects of this invention are:
[0039] The aforementioned thin-walled composite reinforcement structure for highway tunnels comprises multiple sets of reinforcing segments, sequentially spliced along the length of the tunnel. Each set of reinforcing segments consists of two segments, their tops connected and staggered left and right, while their bottoms connect to the tunnel's internal beams. The reinforcing segments are precast concrete structures. Each segment includes a thinned section and main support sections connected to both sides of the thinned section. The thinned section is 4-5 meters above the ground, and its thickness is less than that of the main support sections. The thinned section and the main support sections have the same normal compressive bearing capacity. Each reinforcing segment has holes for hoisting, grouting, or connection. The design method used in this design of the thin-walled composite reinforcement structure for highway tunnels is described.
[0040] The aforementioned thin-walled composite reinforcement structure for highway tunnels, by employing a prefabrication and assembly method, shortens the construction period and overcomes the risk of tunnel structure settlement, ensuring safety at the boundary between the tunnel segments and the building. Furthermore, by locally thinning the tunnel segments while maintaining the same overall compressive strength, the on-site applicability of the segments is improved without reducing load-bearing capacity, thereby increasing the usable passage space in the tunnel. Simultaneously, by using concrete with different compressive strengths to form NC-UHPC-NC combined reinforced segments, a thin-walled composite reinforcement structure for tunnels can be easily achieved. Attached Figure Description
[0041] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly described below. In all the drawings, the elements or parts are not necessarily drawn to scale.
[0042] Figure 1 This is a schematic diagram of a thin-walled composite reinforcement structure for a highway tunnel after installation, according to an embodiment of the present invention.
[0043] Figure 2 for Figure 1 The image shows a side view of a single reinforcing segment in a thin-walled composite reinforcement structure for highway tunnels.
[0044] Figure 3 for Figure 1 The diagram shows a thinned section in a thin-walled composite reinforcement structure for highway tunnels.
[0045] Figure 4 for Figure 1 The diagram shows the assembly of a thin-walled composite reinforcement structure for highway tunnels.
[0046] Figure 5 for Figure 1 The image shows a top view of a reinforced segment of a thin-walled composite reinforcement structure for highway tunnels (a is a schematic diagram of a wide reinforced segment, b is a schematic diagram of a narrow reinforced segment);
[0047] Figure 6 for Figure 1 The diagram shows a schematic of the holes on the reinforced segments of a thin-walled composite reinforcement structure for highway tunnels (a is a top view, b is a sectional view 1-1 in Figure a, and c is a sectional view 2-2 in Figure a).
[0048] Figure 7 for Figure 1 The diagram shows the connection between a thin-walled composite reinforcement structure for a highway tunnel and a ground beam.
[0049] Figure 8 for Figure 1 A schematic diagram of a partially protruding keyway on the thinned portion of a thin-walled composite reinforcement structure for highway tunnels is shown.
[0050] Figure 9 for Figure 1 A schematic diagram of all the protruding keyways on the thinned section of a thin-walled composite reinforcement structure for highway tunnels is shown.
[0051] Figure 10 for Figure 1 A schematic diagram of the connecting steel bars in a thin-walled composite reinforcement structure for highway tunnels is shown.
[0052] Figure 11 for Figure 1 The image shows the effect of using interface water washing on the thinned portion of the reinforced segment in a thin-walled composite reinforcement structure for highway tunnels.
[0053] Figure 12 for Figure 1The image shown is an effect diagram of the main support part of the reinforced segment in a thin-walled composite reinforcement structure for highway tunnels after interface water washing.
[0054] Figure 13 A schematic diagram of a non-scraping strip;
[0055] Figure 14 for Figure 1 The image shows the effect of the reinforced segments in a thin-walled composite reinforcement structure for highway tunnels after being treated with a non-chuckling strip.
[0056] Figure 15 for Figure 1 The image shows the effect of the reinforced segments in a thin-walled composite reinforcement structure for highway tunnels after being treated with a non-chuckling strip.
[0057] Figure label:
[0058] 100. Reinforced segment; 110. Thinned section; 111. Intermediate thin section; 112. Transition section; 120. Main support section; 201. Lifting hole; 202. Grouting hole; 203. Anchoring hole; 204. Bottom support hole; 300. Ground beam. Detailed Implementation
[0059] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention; therefore, the invention is not limited to the specific embodiments disclosed below.
[0060] Please see Figures 1 to 14 This invention provides a thin-walled composite reinforcement structure for highway tunnels, comprising multiple sets of reinforcing segments 100, which are sequentially spliced along the length of the tunnel. Each set of reinforcing segments 100 includes two segments 100, whose tops are connected to each other and staggered left and right. The bottoms of the two segments 100 are connected to the tunnel's internal beam 300. The reinforcing segments 100 are precast concrete structures. Each reinforcing segment 100 includes a thinned portion 110 and main support portions 120 connected to both sides of the thinned portion 110. The thinned portion 110 is 4-5 meters above the ground, and its thickness is less than that of the main support portion 120. The thinned portion 110 and the main support portion 120 have the same normal compressive bearing capacity. Each reinforcing segment 100 is provided with holes for hoisting, grouting, or connection.
[0061] In practical implementation, the concrete materials for the main support section 120 and the thinning section 110 can be ordinary concrete (NC) and ultra-high performance concrete (UHPC), respectively. (For example, if the main support section 120 is C35 concrete, then the thinning section 110 can use C50, C55, or C60 concrete; if the main support section 120 is C50, C55, or C60 concrete, then the thinning section 110 can use UHPC, i.e., UC120 to UC180 materials). During construction, the thinning section 110 and the main support section 120 are prefabricated in the factory, then spliced together to form the reinforced segment 100, and then transported to the construction site for assembly with the ground beam 300. Furthermore, the height of the thinning section 110 can be adjusted according to the tunnel height.
[0062] The above-mentioned thin-walled composite reinforcement structure for highway tunnels is adopted because it uses a prefabrication and then assembly method (refer to...). Figure 4 This shortened the construction period, overcame the risk of tunnel structure settlement, and ensured the safety of the segment structure at the building boundary. Furthermore, by locally thinning the segments while maintaining the same overall compressive strength, the on-site applicability of the segments was improved without reducing load-bearing capacity, thereby increasing the usable passage space in the tunnel. Simultaneously, by using concrete with different compressive strengths to form NC-UHPC-NC composite reinforced segments, a thin-walled composite reinforcement structure for the tunnel can be easily achieved.
[0063] Please refer to Figure 5 In specific implementation, the reinforcing segment 100 can be configured with two widths, one being a wide reinforcing segment A ( Figure 5 (Figure a) Another type is the narrow reinforcement plate B (Figure a). Figure 5 (See Figure b). The width of the wide reinforcing segment is twice that of the narrow reinforcing segment. Along the length of the tunnel, a transverse staggered assembly is used, with the basic form being B, A, A, (A being an even number of segments) B, meaning the prefabricated structure has rotating symmetry between the two sides of the segments. During assembly, half of the previous ring of segments can serve as a support point for the next segment, thus ensuring that each segment, except for the first one, forms a load-bearing ring after installation, guaranteeing structural stability.
[0064] Please refer to Figure 3 In this embodiment, the thinning portion 110 includes a middle thin portion 111 and transition portions 112112 located on both sides, and the transition portions 112112 gradually thicken from the center to both sides.
[0065] This method has the following advantages:
[0066] First, it can make the stress transition smoothly, prevent stress concentration caused by the stiffness difference between two different types of concrete, thereby improving the durability and load-bearing capacity of the interface.
[0067] Secondly, gradually thinning the interface can reduce the peak values of shear stress and tensile stress, avoiding interface cracking or peeling; it can also enhance the interface bonding effect. A reasonable transition length design can improve the bonding performance between two different types of concrete, thereby increasing the interface bearing capacity.
[0068] Third, it can optimize the overall structural performance, improve the stress transfer efficiency in the transition area, and make the entire structure more stable and reliable.
[0069] Please refer to Figure 6 In this embodiment, the holes include a hoisting hole 201, a grouting hole 202, an anchoring hole 203, a bottom support hole 204, a top bolt hole, a hand hole, a longitudinal quick-connect bolt hole, a longitudinal prestressing hole, and a positioning tenon hole.
[0070] The lifting hole 201 provides a connection point for lifting ropes or lifting equipment, enabling the component to be lifted and moved safely and stably. A properly positioned lifting hole 201 can distribute the lifting force evenly, preventing cracks or damage to the component due to uneven stress during lifting, thus ensuring the safety of the construction process. The location of the lifting hole 201 is determined based on the shape of the component, its center of gravity, and the lifting method, and should be as close as possible to the component's center of gravity to reduce tilting and swaying during lifting.
[0071] Specifically, lifting holes 201 are installed on both sides, as well as the inner and outer sides, of the reinforced tunnel segment 100 to meet the functional requirements of segment lifting and flipping. The number of lifting holes 201 on each side should not be less than two, and they should be symmetrically arranged along the axis of symmetry where the center of gravity is located. The spacing between lifting holes 201 should not exceed 4m. For the inner and outer lifting holes 201, through holes can be used to integrate them, avoiding multiple openings. The size of the lifting hole 201 should not be less than M20, but M24 is commonly used.
[0072] Grouting holes 202 are small holes pre-drilled in the concrete segments for injecting grout. During tunnel construction, after the segments are installed, grouting holes 202 are evenly distributed along the edges or surfaces of the segments. Their purpose is to inject grout into the gaps behind the segments through these holes, filling the voids and enhancing the bond between the segments and the existing lining. To avoid grout blockage, the hole diameter is slightly larger, typically 50–60 mm, and prefabricated components are used.
[0073] The spacing of the grouting holes 202 is usually determined based on the diameter of the reinforced segment 100 and the specific construction requirements. Generally, for highway tunnels, the circumferential spacing of the grouting holes 202 can be 1.5m to 2m, and the longitudinal spacing of the grouting holes 202 can be set to 0.5m to 1m. For example, for thin-walled prefabricated reinforcement of tunnels, when the width of the wide reinforced segment is 1.2m, the width of the narrow reinforced segment is 0.6m, and the circumferential length is about 8m, the circumferential spacing of the grouting holes 202 can be 2m, and one ring of grouting holes is arranged for each ring of segments in the longitudinal direction.
[0074] In tunnel reinforcement, the circumferential location of the anchor holes 203 of the reinforced segment 100 should take into account the stress conditions of the original lining and the assembly method of the reinforced segment 100. Generally, they are evenly distributed along the joint between the reinforced segment 100 and the original lining, with a spacing typically between 2m and 3m. For tunnels with larger diameters and more complex stress conditions, the spacing can be smaller, between 1.0m and 2.0m, to ensure the uniformity and stability of the connection between the segment and the original lining.
[0075] From a longitudinal perspective, the number of anchor holes 203 can be determined based on factors such as the length of the reinforced segment 100 and the longitudinal slope of the tunnel. If the length of the reinforced segment 100 is 1–2 m, 2–3 longitudinal anchor holes 203 can be installed on each reinforced segment 100. For tunnels with a certain longitudinal slope, the density of anchor holes 203 can be appropriately increased at the contact points between the segments and the original lining in the downslope direction of the tunnel to resist the sliding force generated by the weight of the segments.
[0076] The diameter of anchor hole 203 needs to be determined based on the selected anchoring material and the size of the anchor rod (cable). When using anchor cables, due to their relatively complex structure and the presence of protective sleeves, the hole diameter needs to be 30-50mm larger than the anchor cable diameter. For example, if the anchor cable diameter is 15mm, the diameter of anchor hole 203 should be 45-65mm. Therefore, anchor hole 203 can be shared with grouting hole 202, with anchoring performed first and grouting followed by grouting. In general, the diameter of anchor hole 203 is smaller and can be shared with lifting hole 201.
[0077] Please see Figure 7 The bottom support holes 204 of the tunnel segment are specific holes pre-reserved at the bottom of the precast concrete tunnel segment. Their core purpose is to install supports, thereby providing stable support for the tunnel segment. During the tunnel reinforcement process, after the reinforced tunnel segment 100 is assembled ring by ring, the ground beam 300 is firmly connected to the reinforced tunnel segment 100 through these reserved holes. This safely and efficiently transfers the vertical load (including its own weight, the pressure of the overlying soil, and operational loads such as trains) borne by the reinforced tunnel segment 100 to the ground beam 300 below, and to the subbase, foundation, or track bed at the bottom of the tunnel. This ensures the vertical stability of the tunnel structure and prevents the reinforced tunnel segment 100 from sinking, displacing, or experiencing other adverse conditions.
[0078] The bottom support connection is as follows: each set of bottom support holes 204 consists of two holes, one for connecting the original lining structure and the other for connecting the lower support. Generally, at least two sets of support holes are provided for the reinforced segment 100 to maintain structural stability. To ensure uniform stress distribution, the spacing between each set of support holes is no more than 0.6m. To facilitate construction and prevent bolts from becoming difficult to turn in or out smoothly after slight deformation of the support, the support holes adopt a non-fully threaded design. To reduce costs, the lower nut and upper steel pipe are welded together.
[0079] In the project, to ensure that the embedded part of the bottom support hole 204 forms a load-bearing whole with the concrete structure, a connecting steel plate with a thickness of 3-5mm can be installed below the bottom support hole 204. The spacing between the two anchor holes 203 should be 5-10cm, neither too large nor too small. If it is too large, the steel plate will be too large, which is not conducive to construction control; if it is too small, it will be not conducive to concrete pouring. Vertical anchoring bars with a length of not less than 10cm are installed on both sides of the steel plate. Horizontal anchoring bars with a length of not less than 30cm are installed at the top of the embedded part.
[0080] Tunnel segments are assembled circumferentially, meaning they are connected as a whole by bolts. This forms a continuous ring structure with high overall rigidity and stability, enabling the segment structure to withstand large external loads, such as groundwater pressure and soil pressure, ensuring the safety and stability of the tunnel. In circumferential assembly, the connections between segments are tighter, allowing for more effective load transfer and distribution. Simultaneously, the bolted connections between segments create prestress, improving the tunnel's resistance to deformation.
[0081] In practice, the top bolt holes should be arranged along the middle of the segment thickness. The hole size should not exceed 1 / 4 of the segment thickness; that is, for a segment thickness of 15cm, the hole size should not exceed 4cm. Furthermore, the net concrete thickness after subtracting the hole size from the concrete thickness should not be less than the concrete thickness of the non-thickened section.
[0082] When selecting the diameter of the bolt for the top bolt hole, factors such as the reserved bolt hole size, segment manufacturing errors, structural construction errors, and joint force transmission requirements should be comprehensively considered. Generally, the difference between the bolt diameter and the bolt hole diameter should be 10mm. For example, based on load-bearing requirements, if the bolt diameter is 30mm, the bolt hole diameter should be 40mm. If there are no special load-bearing requirements, and the bolt hole diameter is 40mm, the maximum bolt diameter can be 30mm. In practice, for ease of construction, a smaller value can be used, such as a bolt diameter of 25mm.
[0083] In addition to bolt holes, bolt installation also requires manholes on the reinforced segment 100. To facilitate bolt tightening, the width of the manholes should not be less than 15cm along the tunnel circumferential direction and also not less than 15cm along the tunnel longitudinal direction. If the thickness of the main concrete structure is 15cm and the thickness of the outer concrete is less than 50mm, the manhole should be a through-hole design that connects the inner and outer sides. If the thickness of the outer concrete is greater than 50mm, the manhole should not be a through-hole, and the concrete on the outer side of the manhole should be reinforced in the middle to meet the load-bearing requirements. To facilitate manhole construction, the manhole structure should have a cross-section with a larger inner thickness and a smaller outer thickness. For the segments on both sides of the reinforced structure, end working holes should be provided for aesthetic purposes, with the diameter of the end working hole minus the bolt hole diameter > 5cm.
[0084] For tunnel structures experiencing large deformations or uneven longitudinal deformation, longitudinal connecting bolts are required for the tunnel segments. These bolts consist of three parts: pre-embedded nuts on both sides, a middle bushing, and connecting bolts. The pre-embedded nuts on both sides are pre-embedded during the segment casting process, and the connecting bolts are pressed into the pre-embedded nuts through longitudinal compressive stress. For prefabricated tunnel segments, the spacing between longitudinal quick-insertion bolt holes should be 4–6 m, and each segment should have no fewer than two longitudinal quick-insertion bolts, which should be evenly distributed across the segments.
[0085] Because the longitudinal prestressing holes in the tunnel segments are pre-drilled channels along the longitudinal direction of the segments for inserting prestressing tendons, the depth of these holes extends through the entire longitudinal thickness of the segments. These channels, penetrating the longitudinal portion of the segments, are primarily used for longitudinal compaction of the segments or for installing quick-connect bolts. This improves the crack resistance and overall structural integrity of the segments, making the tunnel structure more stable in the longitudinal direction and enhancing the overall load-bearing capacity of the tunnel.
[0086] Longitudinal prestressing holes are symmetrically arranged on both sides of the longitudinal quick-insertion bolt holes, at a distance of 20-40 cm. This distance prevents local stress concentration, which could lead to localized cracking or damage, from being too small, and also prevents insufficient tightening of the quick-insertion bolts from being impossible. Generally, the hole diameter should be 10-20 mm larger than the prestressing tendon diameter to facilitate tendon insertion and subsequent grouting. Using a prestressing tendon diameter of 15.2 mm, the prestressing hole diameter is designed to be 25-35 mm.
[0087] In this embodiment, each reinforced segment 100 has two positioning tenon holes on its longitudinal side. The positioning tenon matching the positioning tenon hole has a spindle-shaped structure, with its maximum central diameter not exceeding 1 / 2 of the tunnel segment, its minimum diameter on both sides not less than 3cm, and its length not less than 15cm (7.5cm on each side). To prevent damage to the segment caused by local stress at the point where the positioning tenon acts, the positioning tenon should preferably be placed at the thickened connection part of the structure, i.e., on both sides of the segment. During construction, the use of positioning tenons ensures the accurate position and orientation of the segments during assembly and installation, which can prevent misalignment, offset, or tilting of the segments and ensure the accuracy of the tunnel's geometry and longitudinal extension.
[0088] Additionally, please see Figure 15 The present invention also discloses a design method for a thin-walled composite reinforcement structure for highway tunnels, used to design the aforementioned thin-walled composite reinforcement structure for highway tunnels, comprising:
[0089] S110. Based on the concrete structural properties of both the thinned portion 110 and the main support portion 120 connected to both sides of the thinned portion 110, the thickness of the thinned portion 110 and the main support portion 120 is determined by the compressive strength method.
[0090] S120. Calculate the reinforcement area at the thinned section 110 using the ultimate bending resistance value M.
[0091] S130, The dimensions of the transition section are designed using a gradually thickening method;
[0092] S140, The interface of the reinforced segment 100 is designed with an uneven surface;
[0093] S150. Design the corresponding hole positions and dimensions according to the tunnel length, width, casting method of reinforced segment 100, and installation method of reinforced segment 100;
[0094] S160. Using an assembly method, multiple sets of reinforced segments 100 are sequentially connected along the length of the tunnel. Each set of reinforced segments 100 includes two reinforced segments 100. The tops of the two reinforced segments 100 are connected to each other and arranged staggered left and right. The tops of the two reinforced segments 100 are also connected to each other.
[0095] In practical implementation, considering the load-bearing capacity of the tunnel segments and to ensure their stability and strength, the thinned sections are designed using the "equal compressive strength" method. The basic idea is that, under the action of external normal supports, the compressive bearing capacity of the thinned sections is consistent with that of the non-thinned sections. The material for the thinned sections is selected based on the space requirements. Generally, if the main support section 120 is made of C35 concrete, then C50, C55, or C60 concrete can be used for the thinned sections; if the main support section 120 is made of C50, C55, or C60 concrete, then UHPC (UC120 to UC180) can be used for the thinned sections.
[0096] The calculation formula for the 110-bit thinned section:
[0097]
[0098] The specific steps for determining the thickness of localized thinning using the isobaric strength method are as follows:
[0099] Using the equal compressive strength method, the compressive bearing capacity of the thinned section is made consistent with that of the non-thinned section. The calculation formula for the thinned section is as follows:
[0100]
[0101] —The compressive strength of the first type of concrete
[0102] d1 — Thickness corresponding to the first type of concrete
[0103] —The compressive strength of the second type of concrete
[0104] d2 — the thickness corresponding to the second type of concrete.
[0105] Case Study on Local Thinning Thickness Calculation
[0106] Taking C35 with a thickness of 25cm as an example, the isobaric thickness of UHPC
[0107] 35 × 25 = 120 × d²
[0108] The calculated isobaric thickness of UHPC is 7.2 cm.
[0109] In actual engineering projects, parameter values are generally rounded up. The following table can be used as a reference for determining the thickness.
[0110] Table 1. Calculation diagram of cross-sectional thickness of isobaric material
[0111]
[0112]
[0113] Note: Minimum thickness (C50~C60 not less than 10cm, UHPC not less than 5cm)
[0114] In this embodiment, the specific method for calculating the reinforcement area at the thinned section using the ultimate bending strength value M includes a method for determining the local thinning reinforcement and a method for calculating the local thinning reinforcement, wherein:
[0115] The method for determining the reinforcement for local thinning is as follows:
[0116] To ensure the stress coordination between the reinforced structure and the existing lining, the reinforcement of the reinforced structure is designed based on the "equal bending resistance" of the entire ring of the reinforced structure from the perspective of the most unfavorable stress. During the calculation process, the existing tunnel structure is not considered because its contribution to the bending moment of the thinned and unthinned sections is similar. In determining the thickness, the bending resistance of the reinforced structure is first calculated using the unthinned section to determine the ultimate bending resistance value M. Based on this, the width of the concrete in the compression zone and the area of the reinforcing steel in the reinforced structure are calculated using the aforementioned bending moment value M.
[0117] The calculation method for local thinning reinforcement is as follows:
[0118] When the concrete material in the non-thinning sections is conventional concrete such as C35 to C60, the calculation formula for the flexural performance of the composite structure is as follows:
[0119]
[0120] l1=D l +D r ―C+D gr ―x d
[0121] l2=D l +C+D gr ―x d
[0122] Where: M—the total bending moment borne by the composite structure
[0123] x d —Area of the compression zone of the composite structure
[0124] f cd —Concrete compressive strength corresponding to the grade
[0125] f cd —Tensile strength of steel bars
[0126] —Reinforcement area at the bottom of C35 tunnel segments
[0127] — Reinforcement area of upper part of C35 tunnel segments
[0128] The tensile moment of the lower reinforcement of l1-C35 segment
[0129] The tensile moment of the upper steel reinforcement of l2—C35 pipe segment
[0130] D l —Original lining thickness
[0131] D r —segment thickness
[0132] D gr — Grouting material thickness
[0133] C—Thickness of the protective layer for the tunnel segments.
[0134] When using UHPC (ultra-high performance concrete) for the thinned section 110, in addition to considering the tensile properties of the steel reinforcement, the tensile properties of the UHPC material itself must also be considered. The reinforcement calculation formula for the composite structure is as follows:
[0135]
[0136] l1=D l +D r ―C+D gr ―x d
[0137] l2=D l +C+D gr ―x d
[0138]
[0139] In the formula: —UHPC segment bottom reinforcement area
[0140] —UHPC segment upper reinforcement area
[0141] b—UHPC segment width
[0142] f tk —UHPC tensile strength
[0143] l1—Tensile moment of the lower reinforcement of UHPC segment
[0144] l2—UHPC segment upper reinforcement tensile moment
[0145] l3—UHPC tube segment cross-section under tensile moment
[0146] The meanings of other symbols are the same as in the above formula.
[0147] Example of calculation for localized thinning reinforcement:
[0148] The segment material is C35, the segment width b is 1.2m, and the original lining thickness D is... l The diameter is 35cm, and the thickness of the segment is D. r The thickness of the grout is 25cm, and the grout thickness D is... gr The concrete cover thickness is 2cm, and the protective layer thickness C is 3.5cm. The reinforcement is Ф20@200. According to the table, the steel reinforcement area is 314.2mm². 2 .
[0149]
[0150] Calculate x d =5cm, M=758kN / m.
[0151] If the main structure is C35 and the local structure is C60, then the thickness of the C60 structure is 15cm as per the previous table, and the grouting material thickness D... gr The reinforcement value is 2cm, and the protective layer thickness C is 2.0cm. Using the aforementioned M and formula, the reinforcement value can be calculated.
[0152]
[0153] It can be solved Reinforcement Ф20@150.
[0154] If the main structure is C60 and 15cm thick, the grouting material thickness D gr The thickness of the protective layer is 2cm, and the thickness C is 1.0cm. Using the above M and the following formula, the reinforcement of UHPC 1560mm can be calculated. 2 , Reinforcement Ф20@200.
[0155]
[0156] The main functions of the transition section are: to smoothly transition stress, preventing stress concentration caused by the stiffness difference between ordinary concrete and ultra-high performance concrete (UHPC), thereby improving the durability and load-bearing capacity of the interface; to reduce interface cracking, as the gradual thinning of the interface can reduce the peak shear and tensile stresses, avoiding interface cracking or delamination; to enhance the interface bonding effect, as a reasonable design of the transition section length can improve the bonding performance between ordinary concrete and UHPC, thus increasing the interface load-bearing capacity; and to optimize the overall structural performance, improving the stress transfer efficiency of the transition area, making the entire structure more stable and reliable.
[0157] The specific method for designing the dimensions of the transition section by gradually increasing the thickness is as follows: make the length of the transition section 3 to 5 times the thickness of the interface.
[0158] For example:
[0159] For the transition zone between ordinary concrete and UHPC, the transition length is typically 3 to 5 times the interface thickness (or contact length). For example, if the interface thickness is 10 cm, a transition length of 30 cm is recommended. The transition angle can be calculated to be between 10 and 30 degrees.
[0160] The interface of the reinforced segment 100 is designed with an uneven surface, specifically including:
[0161] First: The production method when ultra-high performance concrete (UHPC) is poured first and then C60 concrete (NC) is poured;
[0162] During the prefabrication process, a specially treated mold is used, resulting in a raised keyway on the UHPC at the connection between the UHPC and NC. There are two types of keyways: one is a partially raised keyway (…). Figure 8 The keyway height is 20-30mm, the keyway width is 30-40mm, and the keyway spacing is 50-100mm; another type is a fully raised keyway. Figure 9 The groove depth is 20-30mm and the groove width is 30-40mm.
[0163] The UHPC portion is partially embedded into the NC to strengthen the connection between the two different types of concrete and improve the shear mechanical properties at the interface. In addition to keyways, the interface between UHPC and NC also includes steel reinforcement connections (10) and interface washing (…). Figure 11 Interface treatment methods to enhance the mechanical properties of the interface, such as reinforcement, are used. When reinforcing the concrete, the thickness of the concrete cover should be determined according to the requirements of the weaker side of the concrete, i.e., 35mm for C35 to C45, 20mm for C50 to C80, and 10mm for UC120 and above. When washing the interface, the surface laitance must be completely washed away to expose the steel fibers.
[0164] Second: Pour ordinary concrete (NC60) first, then pour ultra-high performance concrete (UHPC).
[0165] How to make a clock:
[0166] During the prefabrication process, a specially treated mold is used, resulting in a recessed keyway on the NC at the connection between the UHPC and NC. There are two types of keyways, as described above. Figure 8 , Figure 9 The interface enhancement method is the same as described above. Figure 10 , Figure 11 This refers to the interface keyway + reinforcing steel + interface washing. For interface washing of ordinary concrete, the quality requirement is to wash away the surface laitance and expose the concrete aggregate.
[0167] In addition, for precast tunnel segments, to ensure the interfacial bonding performance between the segments and the grouting material, the surface of the reinforced tunnel segment 100 can be roughened. The specific method is as follows:
[0168] Use no-chamber tape (such as) Figure 13 The roughening process can be performed using either a grating silicone mold or a roughening strip. It's important to note that the no-chuck strip size should not be too small, the maximum protrusion height should not be less than 5mm, the maximum particle spacing should not exceed 3cm, and the protruding particle cross-section can be triangular, rectangular, etc., to facilitate demolding. Compared to traditional manual roughening, it is more aesthetically pleasing, convenient, saves labor costs, and shortens roughening time. Furthermore, the no-chuck strip can be reused, saving production costs and offering significant economic advantages. This process enhances the adhesion strength between the segments and the grouting material, ensuring structural stability. The finished segment appearance after treatment is shown in the image. Figure 14 .
[0169] The thin-walled composite reinforcement structure for highway tunnels designed using the above method shortens the construction period, overcomes the risk of tunnel structure settlement, and ensures safety at the boundary between the tunnel segments and the building. Furthermore, it improves the on-site applicability of the tunnel segments without reducing load-bearing capacity, thereby increasing the usable passage space in the tunnel. Simultaneously, by using concrete with different compressive strengths to form NC-UHPC-NC combined reinforced tunnel segments, the thin-walled composite reinforcement structure for tunnels can be easily achieved.
[0170] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.
Claims
1. A highway tunnel thin-wall composite reinforcement structure, characterized by, The system comprises multiple sets of reinforced segments, which are sequentially spliced along the length of the tunnel. Each set of reinforced segments includes two segments, which are connected at the top and staggered left and right. The bottom of each reinforced segment is connected to the tunnel's internal beam. The reinforced segments are precast concrete structures. Each reinforced segment includes a thinned section and a main support section connected to both sides of the thinned section. The thinned section is 4-5 meters above the ground, and its thickness is less than that of the main support section. The thinned section and the main support section have the same normal compressive bearing capacity. Each reinforced segment has holes for hoisting, grouting, or connection. The reinforced segments are divided into wide reinforced segments and narrow reinforced segments, with the width of the wide reinforced segments being twice that of the narrow reinforced segments, along the length of the tunnel; The thinning section includes a thin middle section and transition sections on both sides. The transition sections gradually thicken from the center to both sides, and the transition length is 3 to 5 times the interface thickness. The concrete materials of the main support section and the thinning section are ordinary concrete and ultra-high performance concrete, respectively. During construction, the thinning section and the main support section are prefabricated in the factory, then spliced into reinforced segments, and then transported to the construction site for assembly with the ground beam. The connection between the ordinary concrete and ultra-high performance concrete materials is strengthened by using interface keyways, reinforcing steel bars, and interface washing to improve the shear mechanical properties at the interface. The surface of the reinforced segments is roughened using no-chiseling strips or grid silicone molds.
2. The thin-walled composite reinforcement structure for highway tunnels according to claim 1, characterized in that, The holes include hoisting holes, grouting holes, anchoring holes, bottom support holes, top bolt holes, hand holes, longitudinal quick-connect bolt holes, longitudinal prestressing holes, and positioning tenon holes; The lifting holes are provided on both sides, as well as the inner and outer sides of the reinforced tube segment. The number of lifting holes on a single side shall not be less than two, and they shall be arranged symmetrically along the axis of symmetry where the center of gravity is located. The grouting holes are evenly distributed on the edge or surface of the reinforced pipe segment, with a circumferential spacing of 1.5m to 2m and a longitudinal spacing of 0.5m to 1m. The anchoring holes are evenly distributed along the joint between the reinforced pipe segment and the original lining, and the diameter of the anchoring holes is 30-50 mm larger than the diameter of the anchor cable. The bottom support hole is located at the bottom of the reinforced pipe segment and is used to connect with the ground beam; The top bolt holes are arranged along the middle of the thickness direction of the reinforced segment, and the hole size is equal to or less than 1 / 4 of the segment thickness; The handhole is provided on the reinforced segment, and the width of the handhole along the circumferential direction of the tunnel is greater than or equal to 15cm, and the width of the handhole along the longitudinal direction of the tunnel is greater than or equal to 15cm. The spacing between the longitudinal quick-connect bolt holes is 4–6 m; The longitudinal prestressed holes are symmetrically arranged on both sides of the longitudinal quick-connect bolt holes, and are 20-40cm away from the longitudinal quick-connect bolt holes; The positioning tenon holes are provided on the longitudinal side of each of the reinforced tube segments.
3. A design method for a thin-walled composite reinforcement structure for highway tunnels, used to design the thin-walled composite reinforcement structure for highway tunnels as described in claim 2, characterized in that, include: Based on the concrete structural properties used in both the thinned section and the main support section connected to both sides of the thinned section, the thickness of the thinned section and the main support section is determined using the isobaric strength method. The area of reinforcement at the thinned section is calculated using the ultimate bending strength value M. The dimensions of the transition section are designed using a gradually thickening method; An uneven surface is used to design and reinforce the interface of the pipe segments; The location and size of the corresponding holes are designed according to the length and width of the tunnel, the casting method of the reinforcing segments, and the installation method of the reinforcing segments; The method of assembly involves connecting multiple sets of reinforced segments sequentially along the length of the tunnel. Each set of reinforced segments includes two reinforced segments, with the tops of the two segments connected to each other and staggered left and right. The tops of the two reinforced segments are then connected to each other.
4. The design method for the thin-walled composite reinforcement structure of highway tunnels according to claim 3, characterized in that, The specific steps for determining the thickness of localized thinning using the isobaric strength method are as follows: Using the equal compressive strength method, the compressive bearing capacity of the thinned section is made consistent with that of the non-thinned section. The calculation formula for the thinned section is as follows: - Compressive strength of the first type of concrete -Thickness corresponding to the first type of concrete - Compressive strength of the second type of concrete - The thickness corresponding to the second type of concrete.
5. The design method for the thin-walled composite reinforcement structure of highway tunnels according to claim 4, characterized in that, The specific method for calculating the reinforcement area at the local thinning point using the ultimate bending strength value M is as follows: The reinforcement of the reinforced structure is based on the "equal bending resistance" of the entire ring of the reinforced structure. In the calculation process, for the existing tunnel structure, it is considered that its contribution to the bending moment of the thinned section and the unthinned section is similar, so it is not considered. In the process of determining the thickness, the bending performance of the reinforced structure is first calculated using the unthinned section to determine the ultimate bending value M. Based on this, the width of the concrete in the compression zone and the area of the reinforcing steel in the reinforced structure are calculated using the ultimate bending value M.
6. The design method for the thin-walled composite reinforcement structure of highway tunnels according to claim 5, characterized in that, The specific method for designing the dimensions of the transition section by gradually increasing the thickness is as follows: make the length of the transition section 3 to 5 times the thickness of the interface.
7. The design method for the thin-walled composite reinforcement structure of highway tunnels according to claim 5, characterized in that, It also includes roughening the surface of the reinforced pipe segment.