Supporting system for treating collapse of layered tunnel vault and construction method

Abstract

The invention provides a supporting system for treating collapse of a layered tunnel vault and a construction method, and relates to the field of tunnel engineering.The supporting system comprises a top surrounding rock reinforcing unit and a tunnel main body structure which are arranged in a tunnel collapse area, and the supporting system is further provided with an arched I-shaped steel unit which is located in the tunnel main body structure to form primary supporting; and a supporting structure reinforcing unit for resisting the rock pressure in the tunnel collapse area and reinforcing the supporting force is arranged on the arched I-shaped steel unit. Through the cooperation of the structures, the structure has the following beneficial effects that firstly, the layered rock mass is asymmetrically reinforced through the grouting anchor rods, and the integrity and the self-bearing capacity of the top surrounding rock are improved to the maximum extent; and secondly, the surrounding rock is supported and reinforced through the spring rod supporting component, the secondary collapse phenomenon caused by overweight backfilled concrete or poor cohesiveness of the surrounding rock is avoided, and a concrete sealing layer with the thickness of 10 cm is laid on the surface of the surrounding rock through the concrete spraying technology.

Description

Technical Field

[0001] The invention relates to the field of tunnel engineering, and in particular to a support system and a construction method for processing layered tunnel vault collapse. Background Art

[0002] Due to the particularity of tunnel engineering, its construction process will inevitably cause disturbance to the rock mass. Therefore, many engineering disasters often occur during tunnel excavation, among which landslides inside the tunnel are the most serious, often resulting in a large number of casualties and economic losses.

[0003] During the construction of tunnel projects, due to the limitation of site conditions, it is difficult to fully implement exploration. During the construction process, the geological environment ahead will be greatly different, and the adverse geological conditions are difficult to accurately predict, which increases the risk of tunnel collapse and affects the construction progress and cost. For layered rock tunnels, the main characteristics of the surrounding rock are the development of rock stratification and relatively poor interlayer adhesion. It is very easy for the tunnel vault to collapse along the stratification surface during tunnel construction, and once a collapse occurs, the amount of collapse is often large. Since the phenomenon of tunnel collapse cannot be avoided during the construction of tunnel projects, in addition to strengthening prevention, reasonable disposal measures must also be taken.

[0004] The existing landslide treatment method mainly adopts concrete backfilling, but does not consider the concrete deadweight and surrounding rock bonding problem, and may also cause secondary landslide. Therefore, it is necessary to provide a method for handling tunnel vault collapse and a reinforcement support device to ensure the safety of the tunnel construction process. Summary of the invention

[0005] In view of the shortcomings of the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a support system and construction method for dealing with the collapse of layered tunnel vaults, which can improve the integrity and stability of the layered rock tunnel vault surrounding rock through asymmetric grouting anchor reinforcement, spring rod support and steel arch frame sealing, effectively prevent surrounding rock collapse and secondary landslide, and ensure construction safety and efficiency.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: the present invention provides a support system and construction method for dealing with layered tunnel vault collapse, including a top surrounding rock reinforcement unit and a tunnel main structure arranged in the tunnel collapse area, wherein an arched I-beam unit is also provided in the tunnel main structure to form an initial support, and a support structure reinforcement unit is provided on the arched I-beam unit to resist the rock pressure in the tunnel collapse area and enhance the supporting force.

[0007] In a preferred solution, the tunnel collapse zone includes the collapse zone vault surrounding rock, the vault collapse zone and the tunnel surrounding rock; The top surrounding rock reinforcement unit includes grouting anchor rods arranged inside the arch surrounding rock in the collapsed area and distributed asymmetrically, and spring support rods asymmetrically arranged in the arch collapse area; Grouting anchors are used to reinforce the surrounding rock in the arch collapse area, and a concrete layer is sprayed on the surface of the surrounding rock in the arch collapse area to form a protective barrier.

[0008] In a preferred solution, a plurality of arched I-beam units are laid inside the surrounding rock of the tunnel, and the plurality of arched I-beam units are equidistantly arranged along the axis of the main structure of the tunnel, and the arch axis of the arched I-beam unit matches the contour of the main structure of the tunnel. The end of the spring support rod is arranged on the arched I-beam unit, and the top end is buried in the concrete layer to abut the surrounding rock on the collapsed area of ​​the arch crown, and grouting is used to form an arched initial support structure between the I-beam unit and the concrete layer inside the main structure of the tunnel to provide initial support.

[0009] In a preferred solution, the support structure reinforcement unit includes a first connecting rod group and a steel mesh respectively arranged on the outer diameter surface of the arched I-beam unit to form an outer layer protection structure for resisting the rock pressure of the arch surrounding rock in the collapsed area; A second connecting rod group is also provided at the center of the arched I-beam unit, and a supporting rod group is provided on both sides of the inner diameter surface of the arched I-beam unit and is symmetrically arranged; The second connecting rod group is composed of a plurality of second guiding tubes, the first connecting rod group is composed of a plurality of first guiding tubes, and the plurality of first guiding tubes and the plurality of second guiding tubes are arranged equidistantly along the arch axis of the arched I-beam unit.

[0010] In a preferred solution, the first guide tube is located between the outer diameter surfaces of a plurality of arched I-beam units, and the second guide tube sequentially penetrates the plurality of arched I-beam units, and an integrated arched structure is formed by combining the first guide tube and the second guide tube; The steel sheet mesh is laid on the top of the plurality of first guide tubes to cover the outer surfaces of the plurality of arched I-beam units.

[0011] In a preferred solution, the support rod assembly includes a convex base, a threaded rod, a support jack and a threaded sleeve; The top end of the support bracket is connected to the inner diameter surface of the arched I-beam unit, and one end of the threaded rod is embedded in the support bracket, and the other end extends into the interior of the internal threaded sleeve and is connected to the thread of the threaded sleeve. The threaded rod can rotate relative to the internal threaded sleeve and move axially along the threaded sleeve to adjust the telescopic length of the threaded rod in the internal threaded sleeve. The end of the threaded sleeve is connected to a convex base that abuts the ground.

[0012] In a preferred embodiment, the present invention provides a construction method for the support system for handling the collapse of the layered tunnel vault as described above, which comprises the following steps: S1. Concrete spraying and grouting anchor reinforcement: When encountering a tunnel collapse area during tunnel main structure excavation, firstly spray concrete on the arch collapse area to seal the surface, and then install grouting anchors inside the arch surrounding rock in the collapse area for reinforcement; S2. Installation of steel arch frame and formation of initial support structure: After the top surrounding rock is reinforced with grouting anchor rods, the steel arch frame is installed below. Each section of the steel arch frame is composed of multiple arched I-beam units to form a closed support structure; S3. Arrangement of support rods and installation of spring support rods: In order to protect the unenclosed steel arch support structure, support rods are arranged on the left and right sides of the steel arch to support the steel arch; S4, welding of connecting rods and steel wire mesh: a first connecting rod group is welded above the arched I-beam unit located at the arch top along the arch axis to connect multiple groups of steel arch frames at the front and rear to jointly bear the load. In addition, fine-mesh steel wire mesh is welded above multiple first connecting rod groups, and a closed initial support structure is formed by spraying concrete; S5. Removal of the support rod group and final closure: The support rod group is removed before the initial support shotcrete. At this time, the front closed and rear unclosed steel arch frames are connected by the second connecting rod group and the first connecting rod group to play the role of auxiliary support.

[0013] In a preferred solution, in step S1, according to the layered rock mass characteristics of the arch surrounding rock in the collapsed area, the grouting anchor rods are asymmetrically distributed, including layer-oriented anchor rods, reverse layer-oriented anchor rods and bottom anchor rods, and the layer-oriented anchor rods, reverse layer-oriented anchor rods and bottom anchor rods are arranged differently according to their different characteristics; Among them, the reinforcement angle of the bedding-oriented anchor rods is arranged parallel to the bedding plane of the surrounding rock of the arch in the collapsed area; The reinforcement angle of the reverse layer anchor is arranged vertically to the bedding plane of the surrounding rock of the arch in the collapsed area; The reinforcement angle of the bottom anchor rod is arranged to intersect the bedding plane of the arch surrounding rock in the collapsed area at a certain angle.

[0014] In a preferred solution, in step S4, a row of second connecting rods is welded at the center of the arched I-beam unit to connect the front and rear multiple groups of steel arch frames again.

[0015] In a preferred solution, in step S4, the arched I-beam unit and its matched second connecting rod group and first connecting rod group can determine the stability of the structure through a specific algorithm, and the calculation process is expressed as follows: S41, input parameters; S42, calculation process: Calculation of the distance from the centroid to the edge of the arched I-beam unit section: The centroid coordinates of the arched I-beam unit are , and the radius of curvature is , then from the centroid to the edge of the arc The distance formula is: ; Through the radius of curvature Calculate the degree of arch bending and the estimated maximum bearing capacity threshold, then the bending moment The formula is: ; in, is the force, is the span, and the arch can be simplified as ; For the arched I-beam element, the bending moment It can be calculated by the method of structural mechanics, that is, it can be determined according to the load distribution and the shape of the arch axis. The formula for the bending section coefficient is: ; in, is the moment of inertia, is the distance from the centroid of the cross section to the outermost edge; According to the bending stress formula in material mechanics, substitute it into the formula and , then the maximum bending stress of the arched I-beam unit is: ; in, is the bending moment, is the bending section coefficient; The tensile strength of the steel selected for the arched I-beam unit is obtained as , then the safety factor is introduced , to calculate the allowable bending stress for: ; Among them, the safety factor The value range is between 1.5 and 3.0; After comparing the maximum bending stress and allowable bending stress To ensure the safety of the structure, the maximum bearing capacity threshold The following conditions should be met: ; Among them, if Close to or exceed , then adjust the cross-sectional size and change the material parameters until the safety requirements are met; Therefore, the maximum carrying capacity threshold The calculation formula is as follows: ; Substitution ,available: ; Next, based on factors such as steel strength and load distribution, an algorithm is used to determine the optimal diameter of the first guide tube in the first connecting rod group. ,quantity and layout; Get the yield strength of the material selected for the first conducting tube and load , then the cross-sectional area of ​​the first conducting tube is: ; Next, according to the diameter of the rod of the first guide tube The calculation formula is determined as: ; Finally, the quantity It can be determined based on the span, load distribution and connection requirements of the structure; The layout can be evenly distributed or optimized according to the load concentration area; Then, the maximum bearing capacity of the first connecting rod group can be calculated by the following formula: ; in, Select the yield strength of the material for the first conducting tube. is the cross-sectional area of ​​a single first conducting tube, is the number of the first conducting tube; According to the number and layout of the first guide tubes in the first connecting rod group, the coverage area of ​​the steel mesh is adjusted accordingly. ; Among them, the width of the steel mesh is , the length is , then the coverage area Determined by the following formula: ; The width of the steel mesh can be determined according to the spacing and distribution of the first guide tubes in the first connecting rod group. and length ; If the spacing between each first guide tube in the first connecting rod group is , then the width of the steel mesh Can be taken as: ; in, is the number of the first conducting tube; Tensile strength of steel mesh The enhancement effect on the overall bearing capacity can be calculated by the following formula: ; in, is the yield strength of the steel bar, is the cross-sectional area of ​​the steel mesh; Next, a row of second connecting rods is welded at the center of the arched I-beam unit, wherein the second connecting rods are composed of The cross-sectional area of ​​each second conducting tube is The yield strength of the material selected for the second conducting tube is ; For the cross-sectional area of ​​the rod , whose diameter is ,but: ; Here, the diameter ,quantity And yield strength , which can be determined according to the steel performance in the actual construction project, the maximum bearing capacity calculation formula of the second connecting rod group is as follows: ; Comprehensive analysis shows that the maximum bearing capacity of the arched I-beam unit is , the maximum bearing capacity of the first connecting rod group is , the maximum bearing capacity of the second connecting rod group is , the tensile strength of the steel mesh is The interaction coefficient between the parts is ,and , then the comprehensive carrying capacity threshold The formula is: ; S43, output results: The predicted comprehensive carrying capacity threshold Output to achieve relevant safety performance indicators.

[0016] The present invention provides a support system and construction method for handling layered tunnel vault collapse. Through the coordination between the above structures, the following beneficial effects can be achieved: First, by using grouting anchors to asymmetrically reinforce the layered rock mass, the integrity and self-bearing capacity of the top surrounding rock are maximized, preventing the surrounding rock from continuing to loosen and collapse.

[0017] Secondly, the surrounding rock is supported and reinforced by spring rod support components, replacing the traditional method of backfilling concrete, avoiding secondary collapse caused by excessive backfill concrete or poor adhesion of the surrounding rock, and being safer and more reliable. At the same time, a 10cm thick concrete sealing layer is laid on the surface of the surrounding rock using sprayed concrete technology, and the top of the spring rod is buried in it, and the bottom is connected to the double-layer support internal steel frame by bolts and welded steel plates, ensuring the firmness and stability of the support components.

[0018] Third, the collapsed cavity is fully blocked by the steel arch frame in conjunction with the first connecting rod and the second connecting rod to provide effective support and bearing capacity. Especially in the roof collapse area, temporary top support devices can be used to ensure the safety and stability of the initial support structure during the landslide control period, thereby ensuring the safety of construction personnel and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a schematic diagram of the grouting anchor structure of the present invention; Figure 2 It is a schematic diagram of the asymmetric support structure of the main structure of the tunnel of the present invention; Figure 3 The present invention Figure 2 Schematic diagram of the three-dimensional Figure 4 It is a schematic diagram of the construction method of the present invention.

[0020] In the figure: tunnel collapse area 1, collapse area arch surrounding rock 11, arch collapse area 12, tunnel surrounding rock 13, grouting anchor rod 2, spring support rod 3, concrete layer 4, initial support structure 5, arch I-beam unit 6, second connecting rod group 7, first connecting rod group 8, steel mesh 9, support rod group 10, convex base 11, threaded rod 12, support top bracket 13, threaded sleeve 14. DETAILED DESCRIPTION

[0021] In order to better understand the purpose, structure and function of the present invention, the embodiments and features in the embodiments of the present application can be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] Example 1 like Figures 1 to 3As shown, a support system for handling the collapse of the arch crown of a layered rock tunnel includes a top surrounding rock reinforcement unit and a tunnel main structure arranged in the tunnel collapse zone 1, wherein an arched I-beam unit 6 is also provided in the tunnel main structure to form an initial support, and a support structure reinforcement unit is provided on the arched I-beam unit 6 to resist the rock pressure in the tunnel collapse zone 1 and enhance the supporting force, and the top surrounding rock is reinforced by means of anchor rods, grouting and the like to prevent further rock slippage or collapse, thereby ensuring construction safety.

[0023] The preferred solution is Figure 1 As shown, the tunnel collapse zone 1 includes the collapse zone vault surrounding rock 11, the vault collapse zone 12 and the tunnel surrounding rock 13; Specifically, the arch surrounding rock 11 in the collapsed area is located at the top of the tunnel main structure and is the key pressure-bearing area of ​​the tunnel structure. The arch collapse area 12 refers to the arch area with potential collapse risk. The tunnel surrounding rock 13 is the rock mass surrounding the tunnel main structure, which provides natural support for the tunnel main structure.

[0024] The top surrounding rock reinforcement unit includes grouting anchor rods 2 arranged inside the arch surrounding rock 11 in the collapsed area and asymmetrically distributed, and spring support rods 3 asymmetrically arranged in the arch collapse area 12, which are used to provide support force immediately to prevent the surrounding rock from further collapsing. The spring support rods 3 have a certain elastic deformation capacity and can automatically adjust when under pressure to maintain the support effect.

[0025] Specifically, by injecting cement slurry into the grouting anchor rod 2 under high pressure, the grouting anchor rod 2 is tightly combined with the surrounding rock of the arch collapse area 12, thereby improving the integrity and shear strength of the surrounding rock of the arch collapse area 12, and effectively reinforcing the surrounding rock of the arch collapse area 12.

[0026] Furthermore, grouting anchor rods 2 are used to reinforce the surrounding rock of the arch collapse area 12, and a concrete layer 4 is sprayed on the surface of the surrounding rock of the arch collapse area 12 to form a protective barrier and further reinforce the surface of the surrounding rock of the arch collapse area 12 to prevent weathering, peeling and other phenomena from occurring, thereby improving the safety of the overall structure to protect and reinforce the surface of the surrounding rock of the arch collapse area 12.

[0027] The preferred solution is Figure 1 , 2 As shown, a plurality of arched I-beam units 6 are laid inside the tunnel surrounding rock 13. The plurality of arched I-beam units 6 are equidistantly arranged along the axis of the tunnel main structure and customized according to the tunnel cross-sectional shape. The arch axis matches the tunnel contour to provide uniform pressure distribution and effective structural support. The end of the spring support rod 3 is arranged on the arched I-beam unit 6, and the top end is buried in the concrete layer 4 to abut against the surrounding rock on the arch collapse zone 12. Grouting is performed to form an arched initial support structure 5 with the I-beam unit 6 and the concrete layer 4 inside the tunnel main structure to provide initial support.

[0028] The preferred solution is Figure 2 , 3 As shown, the support structure reinforcement unit includes a first connecting rod group 8 and a steel mesh 9 respectively arranged on the outer diameter surface of the arched I-beam unit 6, forming an outer protective structure to resist the rock pressure from the arch surrounding rock 11 in the collapsed area, thereby enhancing the stability and bearing capacity of the overall structure, ensuring that the safety and stability of the tunnel can be maintained even under complex geological conditions. A second connecting rod group 7 is arranged at the center of the arched I-beam unit 6, and a supporting rod group 10 is arranged on both sides of the inner diameter surface of the arched I-beam unit 6 and is symmetrically arranged; Among them, the second connecting rod group 7 serves as the core part of the internal support system, ensuring that the arch structure will not bend or deform when subjected to high pressure, thereby improving the reliability and safety of the overall structure. In addition, the support rod group 10 provides necessary lateral support for the internal structure, ensuring that the arch structure remains stable when subjected to force and avoiding displacement or tilting caused by lateral force.

[0029] It should be noted that the second connecting rod group 7 is composed of a plurality of second guide tubes, and the first connecting rod group 8 is composed of a plurality of first guide tubes, and the plurality of first guide tubes and the plurality of second guide tubes are arranged equidistantly along the arch axis of the arched I-beam unit 6, thereby ensuring uniform force on the structure and avoiding the occurrence of stress concentration. Specifically, the first connecting rod group 8 not only enhances the rigidity of the external structure, but also effectively transmits and disperses the rock pressure from the arch surrounding rock 11 in the collapsed area. The second connecting rod group 7 mainly provides internal support and enhances the compressive strength and overall rigidity of the arched I-beam unit 6. Furthermore, the first guide pipe is located between the outer diameter surfaces of the plurality of arched I-beam units 6, and serves as a transverse connector to ensure a tight connection between adjacent units. These first guide pipes are arranged equidistantly along the arch axis, providing the necessary transverse support force and helping to evenly distribute the external load. The second guide pipe sequentially penetrates the plurality of arched I-beam units 6, and serves as another transverse connector to achieve a continuous connection between the plurality of units. The second guide pipe not only enhances the overall rigidity of the structure, but also ensures the stability and compressive resistance of the structure under complex geological conditions. By using the first guide pipe and the second guide pipe in combination, the plurality of arched I-beam units 6 can be closely connected to form an integrated arched structure, which effectively improves the strength and stability of the overall structure. The steel sheet mesh 9 is laid above the plurality of first guide pipes to cover the outer surfaces of the plurality of arched I-beam units 6. The steel sheet mesh 9 increases the integrity and shear resistance of the surface, and can further enhance the integrity and compressive resistance of the structure. It works together with the plurality of first guide pipes to form a solid protective barrier to prevent the direct impact of the surrounding rock pressure on the arched structure.

[0030] Specifically, through the double connection of the first guide tube and the second guide tube, and the covering of the steel mesh 9, the entire arch structure not only has a strong compressive resistance, but also can effectively resist the rock pressure from the arch surrounding rock 11 in the collapsed area, and can maintain the safety and stability of the tunnel even under complex geological conditions. In addition, with the coordinated action of the first guide tube and the second guide tube, the external load can be evenly distributed on each arch I-beam unit 6, avoiding the problem of local stress concentration, so as to extend the service life of the structure.

[0031] In this embodiment, the support rod assembly 10 includes a convex base 101, a threaded rod 102, a support bracket 103 and a threaded sleeve 104; The top end of the support bracket 103 is connected to the inner diameter surface of the arched I-beam unit 6, and one end of the threaded rod 102 is embedded in the support bracket 103, and the other end extends into the interior of the internal threaded sleeve 104 and is connected to the thread of the threaded sleeve 104. The threaded rod 102 can rotate relative to the internal threaded sleeve 104 and move axially along the threaded sleeve 104 to adjust the telescopic length of the threaded rod 102 in the internal threaded sleeve 104. The end of the threaded sleeve 104 is connected to the convex base 101 abutting the ground to provide a stable support foundation. Its convex structure can increase the contact area between the convex base 101 and the ground, thereby improving its anti-slip ability.

[0032] During specific implementation, the support top bracket 103 is firmly connected to the arched I-beam unit 6. By rotating the threaded rod 102, its telescopic length in the threaded sleeve 104 can be changed, thereby fine-tuning the overall height of the support rod group 10, so that the support rod group 10 can adapt to different geological conditions and construction requirements to ensure the best support effect. In addition, the supporting force is transmitted from the ground to the threaded sleeve 104 through the convex base 101, and then transmitted to the support top bracket 103 by the threaded rod 102, and finally acts on the arched I-beam unit 6 to ensure that the threaded rod 102 can stably transmit the supporting force from the ground to the arched I-beam unit 6.

[0033] Example 2 Further description based on Example 1, as Figure 4 The construction method of the support system for handling layered tunnel vault collapse shown includes the following steps: S1. Concrete spraying and grouting anchor rod 2 reinforcement: When encountering tunnel collapse area 1 during tunnel main structure excavation, firstly, concrete is sprayed on the arch collapse area 12 to seal the surface, and then grouting anchor rod 2 is installed inside the arch surrounding rock 11 in the collapse area for reinforcement.

[0034] Specifically, in step S1, according to the layered rock mass characteristics of the arch surrounding rock 11 in the collapsed area, the grouting anchor rods 2 are asymmetrically distributed, including the layer-oriented anchor rods, the layer-reverse anchor rods and the bottom anchor rods, and the layer-oriented anchor rods, the layer-reverse anchor rods and the bottom anchor rods are arranged differently according to their different characteristics; Among them, the reinforcement angle of the anchor bolts along the layer is arranged parallel to the bedding plane of the surrounding rock 11 of the arch in the collapsed area, which means that they directly pass through the bedding plane, which can effectively prevent slip along the bedding plane and enhance the interlayer bonding force; The reinforcement angle of the reverse layer anchor is arranged perpendicular to the bedding plane of the arch surrounding rock 11 in the collapsed area, which can help provide lateral support force, prevent the rock mass from moving in the horizontal direction, and facilitate installation.

[0035] The reinforcement angle of the bottom anchor rod is arranged to intersect the bedding plane of the arch surrounding rock 11 in the collapsed area at a certain angle to ensure convenient installation.

[0036] The asymmetric arrangement ensures the convenience of installation, especially the easier construction of the layer-directed anchor rods, and maximizes the support effect of the anchor rods in the main structure of the layered surrounding rock tunnel, thereby enhancing the stability and safety of the overall structure.

[0037] S2. Installation of steel arch frame and formation of initial support structure 5: After the top surrounding rock grouting anchor rod 2 is reinforced, the steel arch frame is installed below. Each section of the steel arch frame is composed of multiple arched I-beam units 6 to form a closed support structure.

[0038] Specifically, the closed initial support structure 5 can only be formed after all excavations from top to bottom are completed, and this process requires multiple excavation advances.

[0039] S3. Arrangement of the support rod group 10 and installation of the spring support rod 3: In order to protect the unclosed steel arch support structure, the support rod group 10 is arranged on the left and right sides of the steel arch to support the steel arch.

[0040] Among them, in step S3, a spring support rod 3 is installed between the steel arch frame and the arch collapse area 12, one end of which is welded to the top of the steel arch frame, and the other end is pressed against the concrete sprayed on the surface of the surrounding rock. Then, a layer of 10 cm thick arch collapse area 12 is sprayed to fix the top of the spring support rod 3.

[0041] S4. Welding of connecting rods and steel wire mesh: A first connecting rod group 8 is welded above the arched I-beam unit 6 located at the arch top along the arch axis to connect multiple groups of steel arch frames at the front and rear to jointly bear the load. In addition, fine-pore steel wire mesh is welded above multiple first connecting rod groups 8 to prevent subsequent collapse and facilitate subsequent top spraying of concrete to form a closed initial support structure 5, which can avoid uneven spraying and uneven distribution of top concrete, resulting in structural hollowing and leaving safety hazards.

[0042] It should be noted that in step S4, a row of second connecting rods 7 is welded at the center of the arched I-beam unit 6 to weld the front and rear multiple groups of steel arch frames together again, thereby achieving the purpose of secondary reinforcement.

[0043] In the preferred solution, in step S4, the arched I-beam unit 6 and its matched second connecting rod group 7 and first connecting rod group 8 can determine the stability of the structure through a specific algorithm, and the calculation flow of the formula is expressed as follows: S41. Input parameters: Geometric dimensions of the arched I-beam unit 6.

[0044] The shape of the arch axis and the radius of curvature.

[0045] Material properties (such as steel strength).

[0046] S42, calculation process: Calculation of inertia moment of arched I-beam unit 6: When the cross section of the arched I-beam unit 6 is an arc, the calculation of the moment of inertia is more complicated than that of an ordinary straight I-beam. For the arc-shaped cross section, the integral method can be used to calculate the moment of inertia. The cross-sectional curve equation of the arched I-beam unit 6 is: ; in, and They are points on the coordinate axes in the cross-sectional plane, and the arc is rotated around a certain axis to form a cross-section.

[0047] In the moment of inertia calculation, for a plane shape, the cross section is centered around Calculate the moment of inertia of the axis , then the moment of inertia The definition formula is: ; in, is the microelement area, is the microelement area arrive The distance between the axes, for arc-shaped cross-sections, the moment of inertia cannot be simply calculated using the area formula for rectangles or other regular shapes , so it is necessary to divide the arc section into countless tiny area units , and use and Express it.

[0048] That is, the thickness of the arc is , and thickness It is uniform on the cross section, then the formula is: ; in, yes The first derivative of Indicated in Small length increments in the axial direction, Indicated on the arc curve On, due to Small length increments in the axial direction The arc length increment caused by multiplying the two gives the micro-element area enclosed by this tiny length increment and thickness. , then the moment of inertia Determined by the following formula: ; The above integral needs to be calculated according to the specific function expression of the arc, and the formula of the arched I-beam unit 6 is as follows: ; in, is one of the minor arc, major arc, semicircle or quadrant arc, then , substituting the moment of inertia The formula is: ; The value of the moment of inertia can be obtained through a series of complex integration operations.

[0049] Calculation of the centroid position of the arched I-beam unit 6 section: Calculating the centroid of an arc-shaped I-beam section is also relatively complex. For a plane curved section, the centroid coordinates The calculation formulas are: ; ; in, is the cross-sectional area, The representation method is the same as the previous moment of inertia Same in calculation.

[0050] Taking the arched I-beam unit 6 in this embodiment as an example, the cross-sectional area is calculated first, and the formula is: ; Thickness , then calculate by integration and ,for ,but: ; Substitution and , we can get: ; The centroid is obtained by integral operation. coordinate.

[0051] Calculation of the distance from the centroid to the edge of the arched I-beam unit 6 section: After calculating the centroid position using the above formula, the calculation of the distance from the centroid to the outermost edge needs to consider the geometric shape of the arc.

[0052] For the arched I-beam unit 6, if the distance from a certain point in the cross section to the centroid is taken as the outermost distance, it needs to be determined through geometric relationships.

[0053] In this embodiment, the centroid coordinates of the arched I-beam unit 6 are , and the radius of curvature is , then from the centroid to the upper edge of the semicircle The distance formula is: ; Bending degree and bearing capacity estimation: The degree of arch curvature and the estimated maximum bearing capacity threshold are calculated by the curvature radius, and the bending moment The formula is: ; in, is the force, is the span, and the simply supported arch can be simplified as .

[0054] For the arched I-beam element 6, the bending moment It can be calculated by the method of structural mechanics, that is, it can be determined according to the load distribution and the shape of the arch axis. The formula for the bending section coefficient is: ; in, is the moment of inertia, It is the distance from the centroid to the outermost edge of the cross section.

[0055] According to the bending stress formula in material mechanics, substitute it into the formula and , then the maximum bending stress of the arched I-beam unit 6 is: ; in, is the bending moment, is the bending section coefficient.

[0056] The tensile strength of the steel selected for the arched I-beam unit 6 is obtained as , then the safety factor is introduced , to calculate the allowable bending stress for: ; Among them, the safety factor The value range is between 1.5 and 3.0.

[0057] After comparing the maximum bending stress and allowable bending stress To ensure the safety of the structure, the maximum bearing capacity threshold The following conditions should be met: ; Among them, if Close to or exceed , it is necessary to adjust the design parameters, such as increasing the cross-sectional size and changing the material, until the safety requirements are met.

[0058] Therefore, the maximum carrying capacity threshold The calculation formula is as follows: ; Substitution ,available: ; Next, based on factors such as steel strength and load distribution, an algorithm is used to determine the optimal diameter of the first guide tube in the first connecting rod group 8. ,quantity and layout.

[0059] Get the yield strength of the material selected for the first conducting tube and load , then the cross-sectional area of ​​the first conducting tube is: ; Next, according to the diameter of the rod of the first guide tube The calculation formula is determined as: ; Finally, the quantity It can be determined based on the span, load distribution and connection requirements of the structure.

[0060] Specifically, the number The higher it is, the better the stability of the connection will be, but it will also increase the cost and construction difficulty accordingly.

[0061] The layout can be uniformly distributed or optimized according to the load concentration area.

[0062] Then, the maximum bearing capacity of the first connecting rod group 8 can be calculated by the following formula: ; in, Select the yield strength of the material for the first conducting tube. is the cross-sectional area of ​​a single first conducting tube, is the number of the first conducting tubes.

[0063] In addition, it is also necessary to determine the coverage area of ​​the steel mesh 9: According to the number and layout of the first guide tubes in the first connecting rod group 8, the coverage area of ​​the steel mesh 9 is adjusted accordingly. .

[0064] Among them, the width of the steel mesh 9 is , the length is , then the coverage area Determined by the following formula: ; The width of the steel mesh can be determined according to the spacing and distribution of the first guide tubes in the first connecting rod group 8. and length .

[0065] If the spacing between each first guide tube in the first connecting rod group 8 is , then the width of the steel mesh 9 Can be taken as: ; in, is the number of the first conducting tubes in the above formula.

[0066] Tensile strength of steel mesh 9 The enhancement effect on the overall bearing capacity can be calculated by the following formula: ; in, is the yield strength of the steel bar, is the cross-sectional area of ​​the steel sheet mesh 9.

[0067] Next, a row of second connecting rods 7 is welded at the center of the arched I-beam unit 6, wherein the second connecting rods 7 are composed of The cross-sectional area of ​​each second conducting tube is The yield strength of the material selected for the second conducting tube is .

[0068] For the cross-sectional area of ​​the rod , whose diameter is ,but: ; Here, the diameter ,quantity And yield strength , which can be determined according to the steel performance in the actual construction project, the maximum bearing capacity calculation formula of the second connecting rod group 7 is as follows: ; Combining the above formula, the maximum bearing capacity of the arched I-beam unit 6 is , the maximum bearing capacity of the first connecting rod group 8 is , the maximum bearing capacity of the second connecting rod group 7 is , the tensile strength of the steel mesh 9 is .

[0069] Considering that the entire structure works in coordination, the comprehensive bearing capacity threshold It is not a simple addition, but the interaction coefficients between the parts need to be considered. ,and Generally less than 1, the comprehensive bearing capacity threshold The formula is: ; The comprehensive carrying capacity threshold The formula takes into account the comprehensive bearing capacity of the arched I-beam unit 6 itself, the first connecting rod group 8, the second connecting rod group 7 and the steel mesh 9, and can be used to evaluate the safety of the structure under various loads in actual engineering design.

[0070] S43, output results: The predicted comprehensive carrying capacity threshold Output to achieve relevant safety performance indicators.

[0071] S5, removal of the support rod group 10 and final closure: the support rod group 10 is removed before the initial support shotcrete, at which time the front closed and rear unclosed steel arches are connected by the second connecting rod group 7 and the first connecting rod group 8, playing the role of auxiliary support.

[0072] Example 3 Further described in conjunction with Examples 1 and 2, the electronic device used in the construction method of the support system for processing layered tunnel vault collapse includes: A memory, a processor, and a computer program stored in the memory and executable on the processor.

[0073] When the processor executes the program, the construction method of the support system for handling layered tunnel vault collapse provided in the above embodiment is implemented.

[0074] Furthermore, the electronic device further comprises: Communication interface, used for communication between memory and processor.

[0075] Memory is used to store computer programs that can be run on the processor.

[0076] The memory may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0077] If the memory, processor and communication interface are implemented independently, the communication interface, memory and processor can be connected to each other through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 4 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0078] The processor may include one or more processing units, for example, the processor may include an application processor (AP), an application specific integrated circuit (ASIC), a modem processor, a graphics processor (CPU), an image signal processor (ISP), a controller, a memory, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural-network processing unit (NPU). Among them, different processing units may be independent devices or integrated into one or more processors. Among them, the controller may be a neural center and a command center. The controller may generate an operation control signal according to the instruction opcode and the timing signal to complete the control of fetching and executing instructions. A memory may also be provided in the processor for storing instructions and data. In some embodiments, the memory in the processor is a high-speed cache memory. The memory may store instructions or data that have just been used or circulated by the processor. If the processor needs to use the instruction or data again, it may be directly called from the memory. Repeated access is avoided, the waiting time of the processor is reduced, and the efficiency of the system is improved.

[0079] Optionally, in a specific implementation, if the memory, processor and communication interface are integrated on a chip, the memory, processor and communication interface can communicate with each other through an internal interface.

[0080] An embodiment of the present application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above-mentioned construction method of a support system for handling layered tunnel vault collapse.

[0081] The embodiment of the present application also provides a computer program product, which can run computer instructions. When the computer instructions are executed by a processor, the construction method of the support system for handling layered tunnel vault collapse as described above is implemented.

[0082] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0083] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0084] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0085] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or N wirings (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways as necessary and then storing it in a computer memory.

[0086] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0087] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0088] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0089] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A support system for handling layered tunnel vault collapse, comprising a top rock reinforcement unit and a tunnel main structure arranged in a tunnel collapse zone (1), characterized in that: An arched I-beam unit (6) is also provided in the main structure of the tunnel to form an initial support, and a support structure reinforcement unit is provided on the arched I-beam unit (6) to resist the rock pressure of the tunnel collapse zone (1) and to enhance the supporting force.

2. The support system for treating layered tunnel vault collapse according to claim 1, characterized in that: The tunnel collapse zone (1) comprises collapse zone vault surrounding rock (11), vault collapse zone (12) and tunnel surrounding rock (13); The top surrounding rock reinforcement unit comprises grouting anchor rods (2) arranged inside the arch surrounding rock (11) in the collapsed area and distributed asymmetrically, and spring support rods (3) asymmetrically arranged in the arch collapsed area (12); Grouting anchor rods (2) are used to reinforce the surrounding rock of the arch collapse zone (12), and a concrete layer (4) is sprayed on the surface of the surrounding rock of the arch collapse zone (12) to form a protective barrier.

3. The support system for treating layered tunnel vault collapse according to claim 2, characterized in that: A plurality of arched I-beam units (6) are laid inside the tunnel surrounding rock (13), the plurality of arched I-beam units (6) are arranged equidistantly along the axis of the tunnel main structure, the arch axis of the arched I-beam unit (6) matches the profile of the tunnel main structure, the end of the spring support rod (3) is arranged on the arched I-beam unit (6), the top end is buried in the concrete layer (4) to abut against the surrounding rock on the arch collapse zone (12), and grouting is used to form an arched initial support structure (5) inside the tunnel main structure by the I-beam unit (6) and the concrete layer (4) to provide initial support.

4. The support system for treating layered tunnel vault collapse according to claim 3 is characterized in that: The support structure reinforcement unit comprises a first connecting rod group (8) and a steel mesh (9) respectively arranged on the outer diameter surface of the arched I-beam unit (6) to form an outer layer protection structure for resisting the rock pressure of the arch surrounding rock (11) in the collapsed area; A second connecting rod group (7) is also provided at the center of the arched I-beam unit (6), as well as a supporting rod group (10) which is symmetrically arranged on both sides of the inner diameter surface of the arched I-beam unit (6); The second connecting rod group (7) is composed of a plurality of second guiding tubes, and the first connecting rod group (8) is composed of a plurality of first guiding tubes, and the plurality of first guiding tubes and the plurality of second guiding tubes are arranged equidistantly along the arch axis of the arched I-beam unit (6).

5. The support system for treating layered tunnel vault collapse according to claim 4, characterized in that: The first guide pipe is located between the outer diameter surfaces of the plurality of arched I-beam units (6), the second guide pipe sequentially penetrates the plurality of arched I-beam units (6), and an integrated arched structure is formed by combining the first guide pipe and the second guide pipe; The steel sheet mesh (9) is laid above the plurality of first guide tubes to cover the outer surfaces of the plurality of arched I-beam units (6).

6. The support system for treating layered tunnel vault collapse according to claim 4 or 5, characterized in that: The support rod assembly (10) comprises a convex base (101), a threaded rod (102), a support bracket (103) and a threaded sleeve (104); The top end of the support bracket (103) is connected to the inner diameter surface of the arched I-beam unit (6), and one end of the threaded rod (102) is embedded in the support bracket (103), and the other end extends into the interior of the internal threaded sleeve (104) and is connected to the thread of the threaded sleeve (104). The threaded rod (102) can rotate relative to the internal threaded sleeve (104) and move axially along the threaded sleeve (104) to adjust the telescopic length of the threaded rod (102) in the internal threaded sleeve (104). The end of the threaded sleeve (104) is connected to a convex base (101) that abuts against the ground.

7. A construction method for a support system for handling layered tunnel vault collapse as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Concrete spraying and grouting anchor rod (2) reinforcement: When encountering a tunnel collapse area (1) during the excavation of the main structure of the tunnel, firstly, concrete is sprayed on the arch collapse area (12) to seal the surface, and then grouting anchor rods (2) are installed inside the arch surrounding rock (11) of the collapse area for reinforcement; S2, installation of steel arch frame and formation of initial support structure (5): after the top surrounding rock is reinforced by grouting anchor rods (2), a steel arch frame is installed below, and each section of the steel arch frame is composed of a plurality of arched I-beam units (6) to form a closed support structure; S3, arranging the support rod group (10) and installing the spring support rod (3): in order to protect the unenclosed steel arch support structure, the support rod group (10) is arranged on the left and right sides of the steel arch to support the steel arch; S4, welding of connecting rods and steel wire mesh: a first connecting rod group (8) is welded above the arched I-beam unit (6) at the arch top along the arch axis, connecting the front and rear multiple groups of steel arch frames to jointly bear the load, and in addition, fine-mesh steel wire mesh is welded above the multiple first connecting rod groups (8), and a closed initial support structure (5) is formed by spraying concrete; S5, removal of the support rod group (10) and final closure: the support rod group (10) is removed before the initial support shotcrete, and the front closed and rear unclosed steel arch frames are connected by the second connecting rod group (7) and the first connecting rod group (8) to play an auxiliary support role.

8. The support system and construction method for handling layered tunnel vault collapse according to claim 7, characterized in that: In step S1, according to the layered rock mass characteristics of the arch surrounding rock (11) in the collapsed area, the grouting anchor rods (2) are asymmetrically distributed, including the layer-oriented anchor rods, the layer-reverse anchor rods and the bottom anchor rods, and the layer-oriented anchor rods, the layer-reverse anchor rods and the bottom anchor rods are arranged differently according to their different characteristics; Among them, the reinforcement angle of the anchor bolts in the layer direction is arranged parallel to the bedding plane of the arch surrounding rock (11) in the collapsed area; The reinforcement angle of the inverse layer anchor is arranged perpendicular to the bedding plane of the arch surrounding rock (11) in the collapsed area; The reinforcement angle of the bottom anchor rod is arranged to intersect the bedding plane of the arch surrounding rock (11) in the collapsed area at a certain angle.

9. The support system and construction method for handling layered tunnel vault collapse according to claim 7, characterized in that: In step S4, a row of second connecting rod groups (7) are welded at the center position of the arched I-beam unit (6) to connect the front and rear multiple groups of steel arch frames again.

10. The support system and construction method for handling layered tunnel vault collapse according to claim 7, characterized in that: In step S4, the stability of the structure of the arched I-beam unit (6) and its matched second connecting rod group (7) and first connecting rod group (8) can be determined by a specific algorithm. The calculation process is expressed as follows: S41, input parameters; S42, calculation process: Calculation of the distance from the centroid to the outermost edge of the arched I-beam unit (6): The centroid coordinates of the arched I-beam unit (6) are , and the radius of curvature is , then from the centroid to the edge of the arc The distance formula is: ； Through the radius of curvature Calculate the degree of arch bending and the estimated maximum bearing capacity threshold, then the bending moment The formula is: ； in, is the force, is the span, and the arch can be simplified as ; For the arched I-beam element (6), the bending moment It can be calculated by the method of structural mechanics, that is, it can be determined according to the load distribution and the shape of the arch axis. The formula for the bending section coefficient is: ； in, is the moment of inertia, is the distance from the centroid of the cross section to the outermost edge; According to the bending stress formula in material mechanics, substitute it into the formula and , then the maximum bending stress of the arched I-beam unit (6) is: ； in, is the bending moment, is the bending section coefficient; The tensile strength of the steel selected for the arched I-beam unit (6) is , then the safety factor is introduced , to calculate the allowable bending stress for: ； Among them, the safety factor The value range is between 1.5 and 3.0; After comparing the maximum bending stress and allowable bending stress To ensure the safety of the structure, the maximum bearing capacity threshold The following conditions should be met: ； Among them, if Close to or exceed , then adjust the cross-sectional size and change the material parameters until the safety requirements are met; Therefore, the maximum carrying capacity threshold The calculation formula is as follows: ； Substitution ,available: ； Next, based on factors such as steel strength and load distribution, an algorithm is used to determine the optimal diameter of the first guide tube in the first connecting rod group (8). ,quantity and layout; Get the yield strength of the material selected for the first conducting tube and load , then the cross-sectional area of ​​the first conducting tube is: ； Next, according to the diameter of the rod of the first guide tube The calculation formula is determined as: ； Finally, the quantity It can be determined based on the span, load distribution and connection requirements of the structure; The layout can be evenly distributed or optimized according to the load concentration area; Then, the maximum bearing capacity of the first connecting rod group (8) can be calculated by the following formula: ； in, Select the yield strength of the material for the first conducting tube. is the cross-sectional area of ​​a single first conducting tube, is the number of the first conducting tube; According to the number and layout of the first guide tubes in the first connecting rod group (8), the coverage area of ​​the steel sheet mesh (9) is adjusted accordingly. ; Among them, the width of the steel mesh (9) is , the length is , then the coverage area Determined by the following formula: ； The width of the steel mesh can be determined according to the spacing and distribution of the first guide tubes in the first connecting rod group (8). and length ; If the spacing between each first guide tube in the first connecting rod group (8) is , then the width of the steel mesh (9) Can be taken as: ； in, is the number of the first conducting tube; Tensile strength of steel mesh (9) The enhancement effect on the overall bearing capacity can be calculated by the following formula: ； in, is the yield strength of the steel bar, is the cross-sectional area of ​​the steel mesh (9); Next, a row of second connecting rod members (7) is welded at the center of the arched I-beam unit (6), wherein the second connecting rod member group (7) is composed of The cross-sectional area of ​​each second conducting tube is The yield strength of the material selected for the second conducting tube is ; For the cross-sectional area of ​​the rod , whose diameter is ,but: ； Here, the diameter ,quantity And the yield strength , which can be determined based on the steel performance in the actual construction project, the maximum bearing capacity of the second connecting rod group (7) is calculated as follows: ； Comprehensive analysis shows that the maximum bearing capacity of the arched I-beam unit (6) is , the maximum bearing capacity of the first connecting rod group (8) is , the maximum bearing capacity of the second connecting rod group (7) is , the tensile strength of the steel mesh (9) is The interaction coefficient between the parts is ,and , then the comprehensive carrying capacity threshold The formula is: ； S43, output results: The predicted comprehensive carrying capacity threshold Output to achieve relevant safety performance indicators.

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