Lightweight flexible tunnel profile steel arch frame based on equivalent substitution principle

Abstract

The utility model relates to the technical field of tunnel engineering, and discloses a light-weight flexible tunnel section steel arch frame based on an equivalent substitution principle, which comprises an arch section, the arch section comprises light-weight flexible section steel, the light-weight flexible section steel comprises two wing plates with at least upper and lower outer surfaces parallel to each other, and a web plate is arranged between the two wing plates. At least one of the cross-sectional area and the strong-axis inertia moment Ix of the light-weight flexible profile steel is smaller than that of the standard part, and the change range of the maximum strong-axis bending moment Mx of the profile steel arch frame is + / -20% compared with that of the standard part; when the strength of the light-weight flexible profile steel is consistent with that of steel used by the standard part, at least one of the thickness of a web plate and the thickness of a wing plate is smaller than that of the standard part, and at least one of the section height and the section width is larger than that of the standard part; or the section height of the light-weight flexible profile steel is smaller than that of the standard part; or when the strength of the steel used by the light-weight flexible profile steel is larger than that of the standard part, at least one of the web plate thickness, the wing plate thickness, the section height and the section width of the light-weight flexible profile steel is smaller than that of the standard part.

Description

Technical Field

[0001] This utility model relates to the field of tunnel engineering technology, specifically to a lightweight and flexible tunnel steel arch frame based on the principle of equivalent substitution. Background Technology

[0002] In the initial support stage of tunnel construction, the specifications and models of the steel arch frames mainly originate from the I-beams in the national standard GB / T 706-2016 Hot-rolled Steel Sections and the H-beams in GB / T 11263-2024 Hot-rolled H-beams and Split T-beams, and both I-beams and H-beams are standard parts. However, the following major problems currently exist:

[0003] (1) I-beams are essentially a type of general-purpose building steel and are not specifically designed for the special working conditions of tunnel engineering. Their narrow width and excessively thick plates, resulting in a "thick limb and short leg" structural defect, prevent the material performance from being fully utilized and lead to resource waste. Similarly, H-beams, as a type of general-purpose building steel, are not specifically designed for tunnel working conditions, and in practical applications, they also suffer from the problem of material waste due to the incomplete utilization of material utility.

[0004] (2) In terms of the implementation of steel products in the major sectors of plates, pipes, bars, sections, and wires, except for sections, steel with a strength of 300-400MPa has been widely used in other sectors, and steel with a strength of 500-600MPa has also been widely promoted. Some industries have even begun to use steel with a strength of 1000MPa or higher. In foreign countries, high-strength steel with a strength of 600MPa or higher has become the mainstream in the market. However, according to the information from steel mills, in the production of section steel (here referring only to I-beams and H-beams), Q235 accounts for as much as 70-80%, and the remaining part is basically Q355. Higher strength section steel products are almost nowhere to be found, which is significantly different from the requirements of national policies.

[0005] (3) Initial support arches in tunnel engineering are the main application scenario for I-beams and H-beams, especially for I-beams. Tunnel engineering design has significant unique characteristics, and accumulated experience plays a dominant role. After decades of development, railway, highway, and municipal tunnels have each formed complete standards and specifications, and a large number of engineering practices have proven that these specifications have high safety and reliability. In the early days, Q235 material was the mainstream choice and was naturally included in the standard and specification system, which continues to this day. The current situation is that Q235 I-beams are almost entirely used in the general standards for railway, highway, and municipal tunnels, and high-strength steels have almost no place in this field.

[0006] (4) Currently, there are clear specifications for the selection of steel profiles in standard tunnels, while the steel profiles used in non-standard tunnels are self-selected standard components without clear specifications. Due to a lack of experience, materials with excessively high stiffness are often mistakenly selected. Due to their excessive stiffness, it becomes extremely difficult to process them into small-radius arch segments during the manufacturing process. In actual tunnel construction scenarios, the need for processing small-radius arch segments is not uncommon, and the processing obstacles in this regard due to the selection of high-stiffness standard components seriously affect the construction progress and efficiency. More importantly, when the arch frame is put into use in the later stages, due to its excessive stiffness, it is very easy for material deformation to occur when facing complex and changing tunnel conditions, causing buckling deformation of the arch frame, which seriously threatens the stability and safety of the tunnel structure, and also causes the arch frame to fail to play its due support role. In order to ensure the safe operation of the tunnel, it is necessary to maintain and replace the arch frames that have buckled, which undoubtedly increases the later maintenance costs and manpower and material resources of the tunnel project, further exacerbating the waste of resources and the complexity of the project.

[0007] In conclusion, achieving lightweight and high-strength steel profiles remains a long and arduous task, while flexibility is urgently needed. Therefore, designing equivalent lightweight and flexible steel profiles that can be replaced one-to-one is of paramount importance. Utility Model Content

[0008] This utility model aims to provide a lightweight and flexible tunnel steel arch frame based on the principle of equivalent substitution. Under the premise of ensuring the maximum bending moment resistance of the strong axis of the arch frame is equivalent, the steel arch frame is made lightweight and flexible, reducing the amount of steel used, improving the flexibility performance, realizing green and low-carbon development, and helping the country's industrial upgrading.

[0009] To achieve the above objectives, this utility model adopts the following technical solution: a lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution, comprising multiple arch segments with the same bending radius, each arch segment comprising lightweight flexible steel, the lightweight flexible steel comprising at least two wing plates arranged parallel to each other on their upper and lower outer surfaces, and a web plate vertically provided in the middle of the two wing plates, wherein the cross-sectional area and strong axis moment of inertia I of the lightweight flexible steel are... x At least one of the components is less than the standard component it replaces, and the maximum bending moment M of the strong axis of the steel arch frame is... x The variation range compared to standard parts is ±20%; and it is achieved through any of the following methods:

[0010] When the lightweight flexible steel section has the same strength as the steel used in the standard part, at least one of the web thickness and flange thickness of the lightweight flexible steel section is less than that of the standard part it replaces, and at least one of the section height and section width is greater than that of the standard part it replaces; or the section height of the lightweight flexible steel section is less than that of the standard part it replaces; or

[0011] When the steel used in lightweight flexible steel profiles has a strength greater than that of the standard component it replaces, at least one of the web thickness, flange thickness, section height, and section width of the lightweight flexible steel profile must be less than that of the standard component it replaces.

[0012] Furthermore, the minimum bending radius of the lightweight flexible steel section... ≤6m.

[0013] Furthermore, the cross-sectional area and strong axial moment of inertia I of the lightweight flexible steel section... x At least one of them has a reduction ratio greater than 10% compared to the standard part it replaces.

[0014] Furthermore, when the steel used in the lightweight flexible steel section has a strength greater than that of the standard component it replaces, at least two of the web thickness, flange thickness, section height, and section width of the lightweight flexible steel section are less than those of the standard component it replaces.

[0015] Furthermore, the web thickness, flange thickness, section height, and section width of the lightweight flexible steel section are at least three smaller than those of the standard section it replaces.

[0016] Furthermore, when the strength of the steel used in the lightweight flexible steel section is the same as that used in the standard part, the difference between the cross-sectional height of the lightweight flexible steel section and that of the standard part is 0-10%, and the difference between the cross-sectional width of the lightweight flexible steel section and that of the standard part is 0-10%.

[0017] Furthermore, the difference between the cross-sectional height of the lightweight flexible steel and that of the standard part is 0-8%, and the difference between the cross-sectional width of the lightweight flexible steel and that of the standard part is 0-8%.

[0018] Furthermore, the inner surfaces of the two wing plates have the same slope, ranging from 0 to 16.7%; the radius r of the arc at the connection between the wing plate and the web plate includes two cases, namely r=0 or r>0.

[0019] The principle of this scheme is as follows:

[0020] This scheme is based on the principle of equivalent bending moment substitution, that is, the maximum bending moment M of the strong axis of the arch frame. x The variation range compared to the standard part being replaced is ±20%, where the variation range can be ±20%, ±15%, ±10%, ±5%, or ±1%, and the specific range is set according to the actual engineering design requirements, which will not be elaborated here; where M x =W x f, W x For the strong axis section modulus W x =I x / (H / 2), where f is the bending design strength of the steel. The purpose of this study is to determine the maximum bending moment M along the strong axis. xUnder equivalent conditions before and after replacement, material savings and / or reduced arch stiffness are achieved. Lightweighting is specifically manifested in a reduction in the cross-sectional area of ​​the steel arch frame, while flexibility is specifically manifested in a reduction in the strong axis moment of inertia of the steel arch frame.

[0021] When the strength of lightweight flexible steel is the same as that of the steel used in standard parts, M x =W x All three values ​​in f remain unchanged, but according to W x =I x / (H / 2)I x =∫y 2 From dA, we can derive the theory of "wide limbs and thin walls", that is, when achieving the same maximum bending moment of the strong axis, the height is higher, the width is wider, and the thickness is thinner, which can save materials. According to the experimental data in Tables 1-3 and 5 of Example 1, under the premise of equivalent bending moment, the cross-sectional area of ​​the arch frame is reduced, and at least one of the web thickness and wing thickness of the lightweight flexible steel arch frame is reduced, while at least one of the height and width is increased. Only in this way can the lightweight steel arch frame be achieved.

[0022] Furthermore, the experimental data in Table 4 of Example 1 shows that when the cross-sectional height of the lightweight flexible steel section is smaller than that of the standard section it replaces, although the cross-sectional area of ​​the steel arch frame is increased compared to the standard section, the strong axis moment of inertia of the steel arch frame is significantly reduced. That is, the stiffness of the steel arch frame is reduced and the flexibility is increased. While achieving equivalent bending moment, it better realizes flexible support and improves the stability of tunnel steel support.

[0023] When the strength of the steel used in lightweight flexible steel sections is greater than that of the standard parts it replaces, according to the bending moment formula M... x =W x f, bending moment M x Keeping the bending design strength f of steel constant, when the section modulus W of the strong axis increases, x The relative flexural design strength f decreases proportionally, and according to W... x =I x / (H / 2)I x =∫y 2 Based on dA and the experimental data from Example 2, it can be concluded that for lightweight flexible steel sections, at least one of the web thickness, flange thickness, section height, and section width must be less than that of the standard section for W to be feasible. x Only by reducing the bending moment can we ensure that the steel arch frame is made lightweight and flexible under the premise of equivalent bending moment.

[0024] This scheme limits the minimum bending radius of lightweight flexible steel sections, which requires... ≤6m, where 6m is the minimum bending radius commonly used in tunnel engineering construction. If R minA value greater than 6m indicates that the performance of this type of steel arch frame is lower than that of existing arch frame structures, and it cannot achieve an equivalent replacement under the same tunnel conditions.

[0025] The lightweight and flexible steel arch frame obtained based on the above technical principles has the following beneficial effects:

[0026] 1. Lightweight and flexible steel arch frames help the national manufacturing industry transform and upgrade, and promote the national green and low-carbon development strategy:

[0027] The promotion and application of lightweight and flexible steel arch frames, especially as my country's transportation construction gradually focuses on the central and western regions with more mountainous areas, where tunnels account for a high proportion, is of even greater significance.

[0028] 2. Lightweight and flexible steel arch frames save steel consumption, reduce project costs, and offer significant economic benefits, making them highly promising for widespread adoption.

[0029] Experimental data from Examples 1 and 2 show that the lightweight design reduces the cross-sectional area of ​​the steel arch frame, saving material usage. The maximum reduction in steel consumption can reach approximately 20%, demonstrating a significant weight reduction effect. While using high-strength steel for the arch frame increases the unit price of the material and thus the manufacturing cost, actual calculations show that the decrease in steel usage cost outweighs the increase in material unit cost, resulting in a significant overall cost reduction. The cost of steel used in large-scale projects often reaches tens of millions of yuan. Given the current situation of meager profits or even losses in existing projects, Examples 1 and 2 demonstrate that the lightweight, flexible steel arch frame of this solution can reduce project costs by approximately 5%-10%, saving millions of yuan. This is an extremely effective cost reduction method with significant economic benefits. Currently, steel arch frames are used extensively in highways, railways, municipal works, subways, and water conservancy tunnels, offering substantial economic benefits. Using the lightweight, flexible steel arch frame of this solution saves costs for all parties, making this technology highly promising for widespread adoption.

[0030] 3. Research on lightweight and flexible steel arch frames has provided a new direction for solving the world-class problem of tunnel construction in my country:

[0031] The construction of tunnels in high-stress, weak, fractured, and large-deformation surrounding rock is a recognized world-class challenge. Although my country has accumulated rich experience in dealing with large deformation in weak surrounding rock tunnels in actual engineering projects, its support theory and construction methods are still not mature enough. When encountering major deformation, construction always proceeds slowly in a cyclical process of "construction-destruction-replacement" of support. Large deformation in weak surrounding rock remains one of the key control problems for the entire tunnel and even the entire line.

[0032] The inventors collected a large amount of foreign data, studied and deduced repeatedly, and boldly concluded that the key to the arch support technology lies in its "reasonable strength and moderate rigidity and flexibility." This solution addresses both of these technical challenges. Experimental data from Examples 1 and 2 show that using high-strength steel to increase strength significantly improves flexibility, or changing the height of standard components enhances the flexibility of the steel. The resulting reduction in stiffness is precisely what flexible support requires and is a positive indicator. However, current research on high-strength, flexible support for steel arches in my country is extremely limited. Currently, steel arches exhibit two extremes in terms of rigidity and flexibility: one is excessive softness, and the other is excessive rigidity. This reflects a lack of in-depth understanding of moderately rigid flexible support within the industry, and a serious deficiency in practical application. Therefore, this research on lightweight, flexible steel arches provides a new direction for solving this world-class tunnel problem in my country.

[0033] In practical applications, in high-stress soft rock tunnels, the surrounding rock undergoes extreme and prolonged deformation due to its inherent characteristics and the effects of high stress. The flexible steel arch frame in this design, however, can slowly deform alongside the surrounding rock during this deformation process, continuously releasing stress and reducing rock pressure by 20%-30%. This effectively avoids brittle failure caused by excessive rigidity, significantly improving the safety and stability of the support structure. When traversing tunnels across active faults, the flexible support in this design can absorb energy through its elastic deformation when fault activity triggers rock deformation, maintaining the integrity of the support structure and ensuring tunnel safety. For shallow-buried urban tunnels, the flexible steel arch frame in this design, while ensuring tunnel safety, can better coordinate with the deformation of the surrounding soil, reducing the impact on the surrounding environment.

[0034] 4. Lightweight and flexible steel arch frames can also significantly improve the seismic resistance of tunnels:

[0035] Due to the inventor's unexpected discovery during the research of this solution that the arch frame stiffness decreased while its flexibility increased, and that this significantly improved its seismic performance, this solution optimizes the design of the steel materials and structure. In terms of materials, high-strength, high-toughness steel is selected, improving the overall strength and toughness of the structure and enhancing the flexibility of the steel arch frame. When encountering seismic wave impacts, the arch frame can more flexibly deform with ground vibrations rather than rigidly resisting them, greatly reducing the degree of instantaneous stress concentration. In terms of structure, by optimizing the cross-sectional shape and dimensional parameters, the natural frequency of the structure is adjusted to avoid the frequency range of seismic and other vibration loads, reducing the occurrence of resonance and significantly improving the seismic performance of the tunnel support structure, providing strong protection for the safety of tunnel engineering in disaster environments such as earthquakes.

[0036] 5. Lightweight and flexible steel arch frames reduce tunnel defects during its service life and lower the total life-cycle cost of the tunnel:

[0037] Currently, the service life of tunnels in my country is the same as that of foreign countries, with the longest reaching 100 years. However, due to the limitations of the initial support of tunnels, the steel arch frame is often the weak link, which leads to frequent defects in the tunnel, such as collapse, water leakage, secondary lining cracking, and surface uplift. These defects are often related to the damage to the arch frame support, requiring the tunnel to be closed for repair or even large-scale replacement. This not only results in high maintenance costs but also restricts traffic.

[0038] This solution fundamentally improves the load-bearing capacity and durability of the tunnel support structure by optimizing the structural design of the steel arch frame and selecting high-performance steel. The optimized steel arch frame structure can distribute stress more evenly, reducing structural damage caused by localized stress concentration. Simultaneously, the high-performance steel has better corrosion resistance, effectively resisting the erosion of the complex environment inside the tunnel (such as humidity and corrosive gases), delaying structural aging and damage. These factors combined significantly extend the service life of the tunnel support structure, reduce the frequency of defects, lower later maintenance costs and impact on traffic, and improve the long-term economic and social benefits of the tunnel project.

[0039] 6. Lightweight and flexible steel arch frames effectively facilitate efficient construction of non-standard tunnels and improve the support stability of non-standard tunnels:

[0040] This solution optimizes and improves the steel arch frame by reducing its stiffness and enhancing its flexibility. This makes it easier to process small-radius arch sections, improving processing efficiency and allowing the entire project to proceed rapidly. More importantly, non-standard tunnels face complex and variable working conditions, requiring extremely high adaptability of the support structure. The lightweight, flexible steel arch frame demonstrates its advantages in this regard, as it can flexibly adjust its shape according to different geological conditions and stress distributions. When facing complex geological structures, it can more accurately adapt to changes in surrounding rock pressure, effectively dispersing pressure and avoiding buckling deformation caused by stress concentration. This provides stable support for the tunnel structure and ensures safety during tunnel construction and operation. Simultaneously, it significantly reduces maintenance and replacement needs, lowers manpower and material resources, saves maintenance costs, and avoids interference with normal tunnel operation, achieving a double harvest of economic and social benefits and ensuring the continuous and efficient operation of non-standard tunnels. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the steel arch frame according to an embodiment of the present utility model.

[0042] Figure 2 This is a schematic diagram of the H-section of the lightweight flexible steel profile according to an embodiment of the present invention. Figure 1 .

[0043] Figure 3 This is a schematic diagram of the H-section of the lightweight flexible steel profile according to an embodiment of the present invention. Figure 2 .

[0044] Figure 4 This is a schematic diagram of the I-shaped cross-section of the lightweight flexible steel according to an embodiment of the present invention. Detailed Implementation

[0045] The following detailed description illustrates the specific implementation method:

[0046] The reference numerals in the accompanying drawings include: 1. Steel arch frame; 2. Lightweight flexible steel frame; 3. Wing plate; 4. Web plate; 5. Section height H of the lightweight flexible steel frame; 6. Section width B of the lightweight flexible steel frame; 7. Web plate height h; 8. Wing plate overhang width b; 9. Web plate thickness t1; 10. Wing plate thickness t2; 11. Arc radius r at the connection between the wing plate and the web plate; 11. Bending radius R of the steel arch frame.

[0047] This application discloses a lightweight, flexible tunnel steel arch frame 1 based on the principle of equivalent substitution, as shown in the attached figure. Figures 1-4 As shown, it includes multiple arch segments with the same bending radius. Each arch segment includes a lightweight flexible steel section 2. The lightweight flexible steel section 2 includes at least two wing plates 3 arranged parallel to each other on their upper and lower outer surfaces, and a web plate 4 is provided vertically in the middle of the two wing plates 3.

[0048] The lightweighting of the steel arch frame in this application is reflected in the reduction of the cross-sectional area of ​​the steel arch frame, that is, the cross-sectional area of ​​the lightweight flexible steel is smaller than that of the standard component it replaces, thereby reducing the weight of the steel arch frame. The flexibility is reflected in the strong axial moment of inertia I of the steel arch frame. x Reducing the stiffness of the steel arch frame decreases while increasing its flexibility; and the maximum bending moment M along the strong axis of the steel arch frame... x (hereinafter referred to as bending moment M) x The variation range compared to the standard component being replaced is ±20%, which can be ±20%, ±15%, ±10%, ±5%, or ±1%, depending on the actual engineering design requirements, and will not be elaborated here; the minimum bending radius Rmin of the lightweight flexible steel is ≤6m. This is specifically achieved through any of the structures described in Example 1 or Example 2 below.

[0049] In the field of tunnel engineering, hot-rolled ordinary I-beams in the national standard GB / T 706-2016 and hot-rolled H-beams in GB / T11263-2024 are the main steel materials used for steel arch frames. The commonly used steel profiles range in height from 100-350mm and width from 50-300mm. Embodiments 1 and 2 of this application select two endpoints of the height and width, as well as the middle value, as representative models for lightweight and flexible improvements to the cross-sectional dimensions. Specifically, three models are selected: H100×50 H-beams, 20a# I-beams, and H350×300 H-beams.

[0050] Example 1

[0051] In this embodiment, the lightweight flexible steel section uses steel with the same strength as the standard component. At least one of the web thickness t1 and flange thickness t2 of the lightweight flexible steel section is less than that of the standard component it replaces, and at least one of the section height H and section width B is greater than that of the standard component it replaces. Specifically, there are at least nine optimization and improvement methods, but only the following nine have practical engineering significance:

[0052] (1) Experimental groups 1 to 4 adopted the optimization and improvement method of "single increase and single decrease":

[0053] Experimental group 1: H↑, B→, t1↓, t2→;

[0054] Experimental group 2: H↑, B→, t1→, t2↓;

[0055] Experimental group 3: H→, B↑, t1↓, t2→;

[0056] Experimental group 4: H→, B↑, t1→, t2↓.

[0057] (2) Experimental groups 5 and 6 adopted the optimization and improvement method of "single increase and double decrease":

[0058] Experimental group 5: H↑, B→, t1↓, t2↓;

[0059] Experimental group 6: H→, B↑, t1↓, t2↓.

[0060] (3) Experimental groups 7 and 8 adopted the optimization and improvement method of "double increase and single decrease":

[0061] Experimental group 7: H↑, B↑, t1↓, t2→;

[0062] Experimental group 8: H↑, B↑, t1→, t2↓.

[0063] (4) Experimental group 9 adopted the "double increase and double decrease" optimization and improvement method:

[0064] Experimental group 9: H↑, B↑, t1↓, t2↓.

[0065] Tables 1, 2, and 3 are based on standard H-beams of H100×50, 20a# H-beams, and H350×300, respectively, to optimize and compare the cross-sectional dimensions; among them, all standard parts and experimental groups in Tables 1-3 use Q235 steel with a bending design strength f of 215MPa.

[0066] Table 1: Cross-sections and parameters of standard H100×50 H-beams and experimental groups 1-9

[0067]

[0068] Table 2: Cross-sections and parameters of standard 20a# I-beams and experimental groups 1-9

[0069]

[0070] Table 3: Cross-sections and parameters of standard H350×300 H-beams and experimental groups 1-9

[0071]

[0072] Based on the experimental data in Tables 1, 2, and 3, the following conclusions can be drawn:

[0073] 1. When the strength of the steel used in the lightweight flexible steel section is the same as that used in the standard section, at least one of the web thickness t1 and flange thickness t2 of the lightweight flexible steel section is smaller than that of the standard section it replaces, and at least one of the section height H and section width B is larger than that of the standard section it replaces. This results in a reduction in the cross-sectional area of ​​the steel arch frame compared to the standard section it replaces, thus reducing the weight of the steel arch frame and achieving a lightweight effect. Furthermore, the maximum bending moment M of the steel arch frame obtained in all experimental groups is... x Compared to the standard parts that are replaced, the variation range is within ±20%, and the minimum bending radius is less than 6m, which meets the bending design requirements and achieves equivalent bending moment under the same tunnel working conditions.

[0074] 2. The slope of the inner surface of the flange can be 0~16.7%. Specifically, when the slope is 0, the cross section of the lightweight flexible steel is H-shaped. When the slope is greater than 0, the cross section of the lightweight flexible steel is I-shaped. Among them, the standard I-beam is optimized into lightweight flexible H-beam or lightweight flexible H-beam, and the standard H-beam is optimized into lightweight flexible H-beam.

[0075] 3. The radius r of the arc at the connection between the flange and the web includes two cases: r=0 or r>0. When r=0, the steel arch frame is formed by welding; when r>0, the steel arch frame is formed by hot rolling.

[0076] 4. As shown in Table 1-3, for experimental group 9, the cross-sectional height H and cross-sectional width B of the steel arch frame are both greater than those of the standard component it replaces, and the web thickness t1 and wing thickness t2 are both less than those of the standard component it replaces. This achieves the best weight reduction effect, with a steel reduction of no less than 15%, resulting in better lightweighting. Furthermore, the "double increase and double reduction" optimization and improvement method is the optimal choice for practical engineering applications and has significant engineering implications.

[0077] This embodiment is based on the principle that the steel used in the lightweight flexible steel section has the same strength as that used in the standard part. It also provides an engineering example, in which the optimization method is that the cross-sectional height of the lightweight flexible steel section is smaller than that of the standard part it replaces, while the cross-sectional width, web plate and flange plate thickness are larger than those of the standard part. In this engineering example, the standard part is the H294×200 H-beam in "GB / T 11263-2024 Hot-rolled H-beams and Split T-beams". Both the standard part and the experimental group use Q420 steel, and its bending design strength f is 375MPa. Table 4 shows the optimization and improvement of the cross-sectional dimensions of the standard part and the comparison.

[0078] Table 4: Cross-sections and parameters of standard H294×200 H-beams and experimental groups

[0079]

[0080] Based on the experimental data in Table 4, the following conclusions can be drawn:

[0081] When the lightweight flexible steel profile uses the same steel strength as the standard component, and the only difference between the lightweight flexible steel profile and the standard component is its cross-sectional height H, the cross-sectional area of ​​the lightweight flexible steel profile is larger and its weight is increased compared to the standard component. However, the strong axis moment of inertia Ix of the steel arch frame is reduced. According to the formula stiffness = elastic modulus (E) × moment of inertia (I), the stiffness of the steel arch frame is reduced, and the flexibility performance is significantly increased, with an increase of nearly 20%, thus achieving flexible support for the tunnel. Furthermore, the minimum bending radius of the lightweight flexible steel arch frame is less than 6m, and the maximum bending moment Mx varies within ±20% compared to the standard component, meeting the bending design requirements and achieving equivalent bending moment under the same tunnel conditions.

[0082] Furthermore, Table 5 shows the optimization and comparison of cross-sectional dimensions based on standard H100×50 H-beams, 20a# H-beams, and H350×300 H-beams. In experimental groups 1 / 3 / 5, the differences in cross-sectional height H and width B between the medium-sized steel arch frames and the standard components range from 0-10%. In experimental groups 2 / 4 / 6, the differences in cross-sectional height H and width B between the medium-sized steel arch frames and the standard components range from 0-8%, and the difference in width B between the medium-sized steel arch frames and the standard components ranges from 0-10%. All standard components and experimental groups in Table 4 use Q235 steel with a bending design strength f of 215MPa.

[0083] Table 5: Cross-sections and parameters of standard H350×300 H-beams and experimental groups 1-9

[0084]

[0085] Based on the experimental data in Table 5, the following conclusions can be drawn:

[0086] 1. The difference between the cross-sectional height H and cross-sectional width B of the steel arch frame and the standard component being replaced is within 0-10%. Furthermore, the difference between the cross-sectional height H and cross-sectional width B of the lightweight flexible steel frame and the standard component is reduced to 0-8%. The steel arch frames achieve superior lightweighting effects, with a cross-sectional area reduction of over 15%, meaning a reduction in steel material usage of no less than 15%. Moreover, the lightweight flexible steel arch frames meet bending design requirements, achieving equivalent bending moments under the same tunnel conditions. Simultaneously, it effectively improves the balance of the cross-sectional height H and cross-sectional width B of the lightweight flexible steel frame, thereby enhancing plate stability during manufacturing and reducing the overall instability rate during arch frame processing.

[0087] 2. The difference between the cross-sectional height H of the steel arch frame and the standard component it replaces is within 0-10%, and the difference between the cross-sectional width B and the standard component it replaces is within 0-10%. The steel arch frame has a better weight reduction effect, and the cross-sectional area can be reduced by up to 20%, meaning that the amount of steel reduced can be up to 20%.

[0088] 3. Economic Benefit Analysis: Taking experimental group 4 in Table 5 as an example, the cross-sectional area of ​​the lightweight flexible steel arch frame decreased by 15.2%:

[0089] In engineering, arch frames are usually measured by length. The weight per unit length of an arch frame is called the weight per meter (= cross-sectional area × length × steel density). The calculated weight per meter of a standard arch frame is 27.9 kg / m, and the weight per meter of a lightweight flexible arch frame is 23.7 kg / m.

[0090] The cost per meter of arch frame is called the price per meter. The price per meter of standard parts = weight per meter of standard arch frame × unit price of standard parts. The steel used in the standard parts is Q235, and the unit price of standard parts is 3500 yuan / ton, resulting in a price per meter of 97.6 yuan / meter. The price per meter of lightweight flexible steel = weight per meter of lightweight flexible arch frame × unit price of lightweight flexible steel. The steel used in the experimental group is Q235, with a cost unit price of 3900 yuan / ton (mainly due to the increased cost unit price caused by re-producing the mold), resulting in a price per meter of 91.3 yuan / meter for lightweight flexible steel.

[0091] Therefore, the cost saving per meter = standard component price per meter - lightweight flexible component price per meter = 6.3 yuan / meter, and the cost saving ratio (cost saving per meter / standard component price per meter) is 6.45%. For large-scale projects, using this solution's lightweight flexible arch frame can save at least millions of yuan, resulting in a very significant cost reduction.

[0092] Example 2

[0093] In this embodiment, the steel used in the lightweight flexible steel section has a higher strength than the standard component it replaces, and at least one of the web thickness t1, flange thickness t2, section height H, and section width B of the lightweight flexible steel section is smaller than that of the standard component it replaces. Specifically, there are 15 optimization and improvement methods, all of which have practical engineering significance:

[0094] (1) Experimental groups 1-4 adopted the optimized and improved form of "single reduction":

[0095] Experimental group 1: H↓, B→, t1→, t2→;

[0096] Experimental group 2: H→, B↓, t1→, t2→;

[0097] Experimental group 3: H→, B→, t1↓, t2→;

[0098] Experimental group 4: H→, B→, t1→, t2↓.

[0099] (2) Experimental groups 5 and 6 adopted a "double reduction" optimization method:

[0100] Experimental group 5: H↓, B↓, t1→, t2→;

[0101] Experimental group 6: H↓, B→, t1↓, t2→.

[0102] Experimental group 7: H↓, B→, t1→, t2↓;

[0103] Experimental group 8: H→, B↓, t1↓, t2→.

[0104] Experimental group 9: H→, B↓, t1→, t2↓;

[0105] Experimental group 10: H→, B→, t1↓, t2↓.

[0106] (3) Experimental groups 7 and 8 adopted the "three reductions" optimization and improvement method:

[0107] Experimental group 11: H↓, B↓, t1↓, t2→;

[0108] Experimental group 12: H↓, B↓, t1→, t2↓;

[0109] Experimental group 13: H↓, B→, t1↓, t2↓;

[0110] Experimental group 14: H→, B↓, t1↓, t2↓.

[0111] (4) Experimental group 9 adopted the "four reductions" optimization and improvement method:

[0112] Experimental group 15: H↓, B↓, t1↓, t2↓.

[0113] In Table 6, the standard parts use Q235 steel, while all experimental groups use Q355 steel; in Table 7, the standard parts use Q355 steel, while all experimental groups use Q390 steel; in Table 8, the standard parts use Q390 steel, while all experimental groups use Q420 steel.

[0114] The bending design strength f of Q235 is 215MPa, that of Q355 is 305MPa, that of Q390 is 345MPa, and that of Q420 is 375MPa.

[0115] The bending strength f of the steel used in the lightweight flexible tunnel steel arch frame of this embodiment is not limited to the examples listed in this embodiment, and can be selected according to different design requirements.

[0116] Table 6: Cross-sections and parameters of standard H100×50 H-beams and experimental groups 1-15

[0117]

[0118] Table 7: Cross-sections and parameters of standard 20a# I-beams and experimental groups 1-15

[0119]

[0120] Table 8: Cross-sections and parameters of standard H350×300 H-beams and experimental groups 1-15

[0121]

[0122] According to the experimental data in Tables 6, 7, and 8:

[0123] 1. When the strength of the steel used in the lightweight flexible steel section is greater than that of the standard component it replaces, and at least one of the following parameters—web thickness t1, flange thickness t2, section height H, and section width B—is less than that of the standard component it replaces, the cross-sectional area of ​​the steel arch frame is reduced compared to the standard component it replaces, thereby reducing the weight of the steel arch frame and achieving a lightweighting effect; and the maximum bending moment M of the steel arch frame obtained in all experimental groups is... xCompared to the standard parts that are replaced, the variation range is within ±20%, and the minimum bending radius is less than 6m, which meets the bending design requirements and achieves equivalent bending moment under the same tunnel working conditions.

[0124] 2. As shown in Table 5-7, for experimental group 15, the best weight reduction effect can be achieved when the cross-sectional height H, cross-sectional width B, web thickness t1, and flange thickness t2 of the steel arch frame are all smaller than the standard parts being replaced. The amount of steel reduced is not less than 20%, and the lightweight effect is even better. Furthermore, the product obtained by this optimization and improvement has practical engineering significance and is the optimal choice for practical engineering applications.

[0125] 3. As can be seen from the experimental data in Table 5-7, the strong axis moment of inertia I of the lightweight flexible steel arch frame obtained according to the optimization method of this embodiment is... x According to the formula bending stiffness = elastic modulus (E) × moment of inertia (I), the stiffness of the steel arch frame decreases and the flexibility increases significantly. This result is considered a disadvantage under traditional thinking because, in traditional thinking, once the arch frame deforms, it is often regarded as a dangerous signal that the tunnel support is about to fail. Deformation may cause the support structure to be unable to continue to effectively bear the pressure of the surrounding rock, thus leading to serious engineering accidents.

[0126] However, the applicant found from practical application and monitoring results that the more flexible steel arch frame can undergo elastic deformation better under stress, achieving good coordination with the deformation of the surrounding rock. Specifically:

[0127] In high-stress soft rock tunnels, the surrounding rock undergoes extremely large deformations over a long period of time due to its own characteristics and the effects of high ground stress. The flexible steel arch frame in this solution can slowly deform along with the surrounding rock during the deformation process, continuously releasing the surrounding rock stress and reducing the surrounding rock pressure. This effectively avoids brittle failure caused by excessive rigidity and greatly improves the safety and stability of the support structure.

[0128] When traversing tunnels through active faults, the flexible support in this scheme can absorb energy through its own elastic deformation when the surrounding rock is deformed due to fault activity, maintain the integrity of the support structure, and ensure the safety of the tunnel.

[0129] For shallow-buried tunnels in cities, the flexible steel arch frame in this solution can better coordinate the deformation of the surrounding soil and reduce the impact on the surrounding environment while ensuring tunnel safety.

[0130] 4. Based on the increased flexibility of the steel arch frame, the steel arch frame can better undergo elastic deformation under stress and achieve good coordination with the deformation of the surrounding rock. The steel arch frame of this scheme can better dissipate vibration energy and load through flexible deformation, reduce resonance, and significantly improve the seismic performance of the tunnel support structure, providing a strong guarantee for the safety of tunnel engineering in disaster environments such as earthquakes.

[0131] 5. Economic Benefit Analysis: Taking experimental group 15 in Table 8 as an example, the cross-sectional area of ​​the lightweight flexible steel arch frame decreased by 20.2%:

[0132] In engineering, arch frames are usually measured by length. The weight per unit length of an arch frame is called the weight per meter (= cross-sectional area × length × steel density). The calculated weight per meter of a standard arch frame is 108 kg / m, and the weight per meter of a lightweight, flexible arch frame is 86.4 kg / m.

[0133] The cost per meter of arch frame is called the price per meter. The price per meter of standard parts = weight per meter of standard parts arch frame × unit price of standard parts. The steel used in the standard parts is Q390, with a unit cost of 4100 yuan / ton, resulting in a price per meter of 442.8 yuan / meter. The price per meter of lightweight flexible steel = weight per meter of lightweight flexible arch frame × unit price of lightweight flexible steel. The steel used in the experimental group is Q420, with a unit cost of 4600 yuan / ton (the higher unit cost is mainly due to the re-production of molds and the improvement of materials), resulting in a price per meter of 397.4 yuan / meter for lightweight flexible steel.

[0134] Therefore, the cost saving per meter = standard component price per meter - lightweight flexible component price per meter = 36.7 yuan / meter, and the cost saving ratio (cost saving per meter / standard component price per meter) is 10.25%. For large-scale projects, the cost savings of using this solution for lightweight flexible arch frames can reach at least one million yuan, which is a very significant cost reduction.

[0135] The above descriptions are merely embodiments of this utility model. Commonly known technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solution of this utility model. These modifications and improvements should also be considered within the scope of protection of this utility model, and will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution, comprising multiple arch segments with the same bending radius, each arch segment comprising lightweight flexible steel, the lightweight flexible steel comprising at least two wing plates arranged parallel to each other on their upper and lower outer surfaces, and a web plate vertically provided in the middle of the two wing plates, characterized in that: The cross-sectional area and strong axial moment of inertia I of the lightweight flexible steel section x At least one of the components is less than the standard component it replaces, and the maximum bending moment M of the strong axis of the steel arch frame is... x The variation range compared to the standard part is ±20%; and it is achieved through any of the following structures: When the strength of the steel used in the lightweight flexible steel section is the same as that used in the standard part, the web thickness and flange thickness of the lightweight flexible steel section are at least less than those of the standard part being replaced, and the section height and section width are at least greater than those of the standard part being replaced; or the section height of the lightweight flexible steel section is less than that of the standard part being replaced. or When the strength of the steel used in lightweight flexible steel sections is greater than that of the standard parts it replaces, at least one of the web thickness, flange thickness, section height, and section width of the lightweight flexible steel section must be less than that of the standard parts it replaces.

2. The lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution as described in claim 1, characterized in that: The minimum bending radius R of the lightweight flexible steel section min ≤6m.

3. The lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution as described in claim 1, characterized in that: The cross-sectional area and strong axial moment of inertia I of the lightweight flexible steel section x At least one of them has a reduction ratio greater than 10% compared to the standard part it replaces.

4. The lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution according to any one of claims 1-3, characterized in that: When the steel used in the lightweight flexible steel section has a strength greater than that of the standard part it replaces, at least two of the web thickness, flange thickness, section height, and section width of the lightweight flexible steel section shall be less than those of the standard part it replaces.

5. The lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution as described in claim 4, characterized in that: The web thickness, flange thickness, section height, and section width of the lightweight flexible steel section are at least three smaller than those of the standard section it replaces.

6. The lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution according to any one of claims 1-3, characterized in that: When the strength of the steel used in the lightweight flexible steel section is the same as that used in the standard part, the difference between the cross-sectional height of the lightweight flexible steel section and that of the standard part is 0-10%, and the difference between the cross-sectional width of the lightweight flexible steel section and that of the standard part is 0-10%.

7. The lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution as described in claim 6, characterized in that: The difference between the cross-sectional height of the lightweight flexible steel section and that of the standard part is 0-8%, and the difference between the cross-sectional width of the lightweight flexible steel section and that of the standard part is 0-8%.

8. The lightweight flexible tunnel steel arch frame based on the principle of equivalent substitution according to any one of claims 1-3, characterized in that: The inner surfaces of the two flanges have the same slope, ranging from 0 to 16.7%; the radius r of the arc at the junction of the flange and the web includes two cases, namely r = 0 or r > 0.

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