Temporal and spatial design method of rock-bolt-shotcrete synergistic effect in railway tunnel active support considering temporal and spatial effects

Abstract

The present invention specifically discloses a spatiotemporal design method for the synergistic effect of rock-anchor-shotcrete in active support of railway tunnels that takes into account spatiotemporal effects, and relates to the field of civil engineering technology. The method first clarifies the performance characteristics of the load-time effect, material-time effect, face-space effect, and rock-anchor bearing arch-space effect of active support, establishes a spatiotemporal effect characterization method, and then constructs a spatiotemporal calculation model for the synergistic effect of rock-anchor-shotcrete in active support of tunnels; then determines the calculation parameters of the rock-anchor bearing arch and shotcrete layer, and constructs a surrounding rock pressure calculation method and a safety evaluation method that considers the effect of advance support; finally, based on the calculation results of the spatiotemporal calculation model for the synergistic effect of rock-anchor-shotcrete in active support of tunnels, the safety is judged and the design parameters of prestressed anchor rods and shotcrete are determined. This method can simply, quickly, and accurately calculate the internal force distribution and safety of the rock-anchor bearing arch and shotcrete layer in tunnels under different times, geological conditions, and support design parameters, and has good engineering value.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, in particular to a time-space design method for active support rock-bolt-spraying synergy in a railway tunnel taking time-space effects into consideration. Background Art

[0002] With the advancement of mechanized and intelligent construction technologies, tunnel projects are expanding in scale and increasing in number. Large, mechanized tunnels often utilize the full-section excavation method to ensure efficiency. However, due to the large excavation area and rapid construction speed, this method can easily lead to damage such as rock fragmentation and collapse in the surrounding rock. To mitigate this damage and ensure construction safety, tunnels often utilize an active support system consisting of prestressed anchors and early-stage, high-strength shotcrete.

[0003] Active support systems utilize high-performance materials with high early strength, and their mechanical properties evolve over time, exhibiting significant temporal effects. Furthermore, tunnel construction is a three-dimensional process, subject to strong spatial effects. Therefore, exploring and quantifying the temporal and spatial effects of active support is crucial. Furthermore, establishing a corresponding temporal and spatial design model for active support is essential to achieve precise and efficient tunnel support to minimize hazards.

[0004] Currently, research on the spatiotemporal effects of active support and corresponding design models has been conducted through methods such as analogical design, theoretical analysis, and field testing. However, a detailed definition and quantitative calculation method for the spatiotemporal effects of active support have not yet been established. Existing design models analyze the rock anchor bearing arch and shotcrete layer separately, lacking a design model that integrates the two. Furthermore, consideration of the spatiotemporal effects of active support is limited. Therefore, it is of great significance to propose a spatiotemporal design method for the synergistic effect of rock anchor and shotcrete in railway tunnel active support that considers spatiotemporal effects. This method can be used to implement the spatiotemporal effect-based design of prestressed anchors and shotcrete supports. Summary of the Invention

[0005] The purpose of the present invention is to propose a spatiotemporal design method for the synergistic effect of rock-anchor and shotcrete in active support of railway tunnels, which takes into account the spatiotemporal effects. The method can simply, quickly and accurately calculate the internal force distribution and safety of the tunnel rock-anchor bearing arch and shotcrete layer under different time, geological conditions and support design parameters, and provide a reference for the design of tunnel engineering using active support systems with prestressed anchors and shotcrete.

[0006] To achieve the above objectives, the present invention proposes a spatiotemporal design method for active support of railway tunnels using rock bolting and shotcrete in consideration of spatiotemporal effects, comprising the following steps:

[0007] Step S1: clarify the characteristics of the temporal and spatial effects of active support, including load time effect, material time effect, tunnel face spatial effect, and rock anchor bearing arch spatial effect;

[0008] Step S2: establishing a method for characterizing the temporal and spatial effects of active support based on the temporal and spatial effects of active support;

[0009] Step S3: establishing a spatiotemporal calculation model for the coordinated effect of rock bolting and shotcrete in active tunnel support;

[0010] Step S4, determining the calculation parameters of the rock anchor bearing arch according to the spatiotemporal calculation model of the rock anchor shotcrete synergistic effect of active tunnel support;

[0011] Step S5, determining the calculation parameters of the shotcrete layer according to the spatiotemporal calculation model of the rock-bolt-shotcrete synergy in active tunnel support;

[0012] Step S6: establishing a calculation method for tunnel surrounding rock pressure taking into account the effect of advance support;

[0013] Step S7: establishing a safety evaluation method for tunnel active support rock anchor bearing arch and shotcrete layer;

[0014] Step S8: judging the safety of the rock anchor bearing arch and the shotcrete layer according to the calculation results of the spatiotemporal calculation model of the rock anchor shotcrete synergy in the tunnel active support;

[0015] Step S9: Determine the design parameters of the prestressed anchor rods and shotcrete according to the calculation results of the spatiotemporal calculation model of the rock-bolt-shotcrete synergy for active tunnel support.

[0016] Preferably, in step S2, the specific steps of establishing the method for characterizing the spatiotemporal effect of active support are as follows:

[0017] Step S21: The time effect of active support load is characterized by a deformation load calculation formula that considers time development. The deformation load calculation formula can be obtained by fitting the field measured data. The formula is as follows:

[0018] ;

[0019] ;

[0020] in, is the calculation function of the vertical pressure of deformation load changing with time; is time, (s); and are the load reduction factor and lateral pressure coefficient reduction factor obtained by fitting based on field measured data; is the vertical pressure value of deformation load, (Pa); is the vertical pressure of the surrounding rock calculated according to the railway tunnel design specifications, (Pa); are the fitting parameters obtained by fitting the field measured data; is the calculation function of the deformation load horizontal pressure changing with time; is the horizontal pressure value of the deformation load, (Pa); is the lateral pressure coefficient determined according to the railway tunnel design specifications;

[0021] Step S22: The time effect of the active support material is characterized by calculating the elastic modulus, compressive strength, and tensile strength of shotcrete with consideration of time. The calculation formulas for the elastic modulus, compressive strength, and tensile strength of shotcrete can be obtained by fitting data obtained from indoor tests, field measurements, or literature research. The formulas are as follows:

[0022] ;

[0023] ;

[0024] ;

[0025] in, is the calculation function of the compressive strength of tunnel shotcrete changing with time; Shotcrete for tunnels Compressive strength at the moment, (Pa); is the compressive strength of tunnel shotcrete at the final moment, (Pa); is the calculation function of the change of tensile strength of tunnel shotcrete with time; Shotcrete for tunnels Tensile strength at the moment, (Pa); is the calculation function of the elastic modulus of tunnel shotcrete changing with time; Shotcrete for tunnels Elastic modulus at the moment, (Pa); is the elastic modulus of tunnel shotcrete at the final moment, (Pa);

[0026] Step S23: The spatial effect of the active support face is characterized by introducing a calculation formula for virtual support force. The virtual support force refers to the supporting force exerted by the face on the tunnel profile, which can be obtained through literature research or formula derivation. The formula is as follows:

[0027] ;

[0028] ;

[0029] ;

[0030] in, is the calculation function of virtual support force; is the virtual support force, (Pa); is the friction angle of surrounding rock, (°); is the cohesion of surrounding rock, (Pa); is the tunnel radius, (m); is the maximum plastic zone radius of the tunnel, (m); is the distance from the tunnel face, (m); is the distance from the tunnel face when the plastic zone just appears, (m); is the calculation function of the maximum plastic zone radius of the tunnel; is the calculation function of the distance from the tunnel face when the plastic zone just appears;

[0031] Step S24: The spatial effect of the active support rock anchor arch is characterized by the equivalent elastic modulus, friction angle, and cohesion calculation formula of the rock anchor arch formed by the prestressed anchor and the surrounding rock after the prestressed anchor is applied. The calculation formulas for the equivalent elastic modulus, friction angle, and cohesion of the rock anchor arch can be obtained through theoretical derivation or data fitting, and are as follows:

[0032] ;

[0033] ;

[0034] ;

[0035] in, is the calculation function of the equivalent friction angle of the rock anchor bearing arch; is the equivalent friction angle of the rock anchor bearing arch, (°); is the diameter of the anchor rod, (m); is the friction resistance coefficient between the anchor and the surrounding rock; is the longitudinal spacing of anchor rods, (m); is the circumferential spacing of anchor rods, (m); is the calculation function of the equivalent cohesion of the rock-anchored bearing arch; is the equivalent cohesion of the rock anchor bearing arch, (Pa); is the anchor rod prestress value, (kN); is the calculation function of the equivalent elastic modulus of the rock anchor bearing arch; is the equivalent elastic modulus of the rock anchor bearing arch, (Pa); is the elastic modulus of surrounding rock, (Pa); is the elastic modulus of the anchor rod, (Pa).

[0036] Preferably, in step S3, the specific steps of establishing a spatiotemporal calculation model of the synergistic effect of rock bolting and shotcrete in active tunnel support are as follows:

[0037] Step S31: Based on the active support reinforcement mechanism, prestressed anchor rods are applied to improve the mechanical parameters of the surrounding rock to form a rock anchor bearing arch;

[0038] Step S32: The shotcrete acts as a surface protector for the rock anchor bearing arch and bears the surrounding rock pressure together, thereby establishing a spatiotemporal calculation model for the active support rock-anchor-shotcrete synergistic effect;

[0039] In step S33, in the active support rock-anchor-shotcrete synergistic spatiotemporal calculation model, both the rock anchor bearing arch and the shotcrete layer are simulated using beam elements. The two structures are connected by radial compression-only springs and tangential springs, representing the radial and tangential bonding between the shotcrete layer and the surrounding rock. The rock anchor bearing arch and the surrounding rock are connected by radial compression-only springs. The rock anchor bearing arch and the bottom of the shotcrete layer are constrained and fixed by hinged supports, and a virtual support force is applied to the bottom of the rock anchor bearing arch to account for the spatial effect of the tunnel face.

[0040] Preferably, in step S4, the calculation parameters of the rock anchor bearing arch are determined, and the specific steps are:

[0041] Step S41: Determine the rock anchor bearing arch thickness and set it as the anchor rod length L ;

[0042] Step S42: Calculate the equivalent elastic modulus, friction angle, and cohesion of the rock anchor bearing arch according to the spatial effect characterization method of the active support rock anchor bearing arch;

[0043] Step S43: Calculate the virtual support force borne by the rock anchor bearing arch according to the active support tunnel face spatial effect characterization method;

[0044] Step S44: Determine the spring reaction coefficient between the rock anchor bearing arch and the surrounding rock. The spring reaction coefficient may be selected according to the spring reaction coefficient specified in the Railway Tunnel Design Code.

[0045] Preferably, in step S5, the calculation parameters of the shotcrete layer are determined, and the specific steps are:

[0046] Step S51, determine the thickness of the sprayed layer, and select it according to the thickness of the sprayed concrete;

[0047] Step S52: Calculate the elastic modulus of shotcrete at different times according to the time effect characterization method of active support materials;

[0048] Step S53: Determine the spring reaction coefficient between the shotcrete layer and the rock anchor bearing arch. The spring reaction coefficient may be selected according to the spring reaction coefficient specified in the Railway Tunnel Design Code.

[0049] Preferably, in step S6, the effect of the advanced pipe-roof pre-support on reducing the overburden load on the surrounding rock is taken into consideration, and the calculation formula for the surrounding rock pressure borne on the outer side of the rock anchor bearing arch is modified to be as follows:

[0050] ;

[0051] ;

[0052] ;

[0053] in, is the calculation function of the vertical surrounding rock pressure on the outer side of the rock anchor bearing arch; is the vertical surrounding rock pressure on the outer side of the rock anchor bearing arch, (Pa); Correction coefficient for surrounding rock pressure after tunnel construction with advanced pipe roof; is the weight of surrounding rock, (kN / m 3 ); To calculate the height, (m); is the calculation function for calculating the height; is the surrounding rock level; is the width influence coefficient; is the calculation function of the horizontal surrounding rock pressure on the outer side of the rock anchor bearing arch; is the horizontal surrounding rock pressure on the outer side of the rock anchor bearing arch (Pa); is the lateral pressure coefficient.

[0054] Preferably, in step S7, a safety evaluation method for the active support rock anchor bearing arch and shotcrete layer of the tunnel is established, and the specific steps are as follows:

[0055] Step S71: Calculate the bending moment and axial force of the rock anchor bearing arch based on the spatiotemporal calculation model of rock anchor shotcrete synergy in active tunnel support, and convert them into the safety factor of the rock anchor bearing arch. Considering that the rock anchor bearing arch is thick and the stress state is generally slightly eccentric, the formula is as follows:

[0056] ;

[0057] ;

[0058] in, is the calculation function of the safety factor of the rock anchor bearing arch; is the rock anchor bearing arch safety factor; is the arch axial force carried by the rock anchor, (N); is the longitudinal bending coefficient of the section; is the axial force eccentricity influence coefficient; is the compressive strength of the rock anchor bearing arch, (Pa); Calculate the width of the rock anchor bearing arch (m); is the thickness of the rock anchor bearing arch, (m); is the calculation function of the compressive strength of the rock anchor bearing arch;

[0059] Step S72: Calculate the bending moment and axial force of the shotcrete layer based on the spatiotemporal calculation model of the rock-bolt-shotcrete synergistic effect of active tunnel support, and convert the calculated safety factor of the shotcrete layer into the following formula:

[0060] ;

[0061] ;

[0062] in, is the safety factor when the spray layer is under pressure; is the calculation function of the compressive safety factor of shotcrete; is the longitudinal bending coefficient; is the eccentricity influence coefficient of the axial force; is the ultimate compressive strength of shotcrete, (Pa); is the ultimate tensile strength of shotcrete, (Pa); is the axial force of the spray layer, (N); is the longitudinal depth of the spray layer, (m); is the height of the spray layer, (m); is the radial safety factor of shotcrete under compression; is the calculation function of the tensile safety factor of shotcrete; is the bending moment of the spray layer (Nm).

[0063] Therefore, the present invention proposes a temporal and spatial design method for the coordinated action of rock bolting and shotcrete in railway tunnel active support considering the temporal and spatial effects, which has the following beneficial effects:

[0064] (1) By establishing a systematic method for characterizing the spatiotemporal effects of active support and a synergistic calculation model, this invention can accurately capture the multi-dimensional spatiotemporal effects of load, material, tunnel face, and rock anchor bearing arch, and achieve rapid calculation of the internal force distribution of the tunnel rock anchor bearing arch and shotcrete layer under different time, geological conditions, and support design parameters. Its calculation formula is based on field measurements, indoor tests, and theoretical derivation. It is logically rigorous and easy to operate, allowing ordinary designers to efficiently complete the mechanical analysis of support structures under complex working conditions.

[0065] (2) This invention breaks through the limitation of traditional design that analyzes the rock anchor bearing arch and the shotcrete layer separately. For the first time, it incorporates the two into a synergistic framework and fully considers the impact of advance support on surrounding rock pressure, making the support design more consistent with the actual three-dimensional stress state of the project. The safety factor calculated by the safety evaluation method can quantitatively reflect the bearing capacity and risk of the support structure, providing a clear basis for the optimization of design parameters and avoiding the safety redundancy or insufficiency that may be caused by empirical design.

[0066] (3) This invention can provide a direct reference for tunnel projects using active support systems with prestressed anchors and shotcrete, effectively guiding the determination of support parameters (such as anchor length, prestress value, shotcrete thickness, etc.), thereby reducing the risks of surrounding rock instability and support structure damage during tunnel construction and ensuring construction safety. At the same time, through precise design, it reduces material waste and rework costs, taking into account both safety and economy, and has broad prospects for promotion and application in large-scale mechanized tunnel projects.

[0067] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is a flow chart of a temporal and spatial design method for active support of railway tunnels with rock-bolt-shotcrete synergy taking into account temporal and spatial effects according to the present invention;

[0069] Figure 2 Schematic diagram of the spatiotemporal calculation model structure of rock-bolt-shotcrete synergistic action for active tunnel support provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0070] To make the technical solutions, advantages, and objectives of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The described embodiments are part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0072] Example

[0073] like Figure 1 As shown, the present invention provides a temporal and spatial design method for the coordinated action of rock bolting and shotcrete in active support of railway tunnels considering temporal and spatial effects, and the specific steps are as follows:

[0074] S1. Clarify the characteristics of the temporal and spatial effects of active support, including load-time effect, material-time effect, tunnel face spatial effect, and rock-anchor bearing arch spatial effect;

[0075] The load-time effect of active support is as follows: as the tunnel excavation progresses, the stress inside the surrounding rock is redistributed and the surrounding rock gradually deforms. At this time, the load exerted by the surrounding rock on the support structure gradually increases with time and eventually tends to be stable.

[0076] The material time effect of active support is: the shotcrete in active support adopts high-performance concrete material, and its mechanical properties (elastic modulus, compressive strength, etc.) show an obvious growth trend over time.

[0077] The spatial effect of the active support face is as follows: as the tunnel face continues to advance, along the longitudinal section of the tunnel, due to the supporting effect of the face, the elastic-plastic deformation of the tunnel surrounding rock after excavation cannot be fully released, and the elastic-plastic stress redistribution cannot be completed quickly. The elastic-plastic deformation of a certain section is gradually released until it is completed as the distance from the face increases.

[0078] The spatial effect of the active support rock anchor bearing arch is: when prestressed anchor rods are applied to the surrounding rock, its mechanical parameters and bearing capacity will be significantly improved. The prestressed anchor rods and the surrounding rock together form a bearing structure, namely the rock anchor bearing arch.

[0079] S2. Establish a characterization method for the temporal and spatial effects of active support based on the temporal and spatial effects of active support. The specific steps are as follows:

[0080] S21. The time effect of active support load is characterized by a deformation load calculation formula that considers time development. The deformation load calculation formula can be obtained by fitting the field measured data. The formula is as follows:

[0081] ;

[0082] ;

[0083] in, is the calculation function of the vertical pressure of deformation load changing with time; is time, (s); and are the load reduction factor and lateral pressure coefficient reduction factor obtained by fitting based on field measured data; is the vertical pressure value of deformation load, (Pa); is the vertical pressure of the surrounding rock calculated according to the railway tunnel design specifications, (Pa); are the fitting parameters obtained by fitting the field measured data; is the calculation function of the deformation load horizontal pressure changing with time; is the horizontal pressure value of the deformation load, (Pa); is the lateral pressure coefficient determined according to the railway tunnel design specifications;

[0084] S22. The time effect of active support materials is characterized by calculating the elastic modulus, compressive strength, and tensile strength of shotcrete with time consideration. The calculation formulas for the elastic modulus, compressive strength, and tensile strength of shotcrete can be obtained by fitting data obtained from indoor tests, field measurements, or literature research. The formulas are as follows:

[0085] ;

[0086] ;

[0087] ;

[0088] in, is the calculation function of the compressive strength of tunnel shotcrete changing with time; Shotcrete for tunnels Compressive strength at the moment, (Pa); is the compressive strength of tunnel shotcrete at the final moment, (Pa); is the calculation function of the change of tensile strength of tunnel shotcrete with time; Shotcrete for tunnels Tensile strength at the moment, (Pa); is the calculation function of the elastic modulus of tunnel shotcrete changing with time; Shotcrete for tunnels Elastic modulus at the moment, (Pa); is the elastic modulus of tunnel shotcrete at the final moment, (Pa); e is the base of the natural logarithm function;

[0089] S23. The spatial effect of the active support face is characterized by introducing a calculation formula for virtual support force. The virtual support force refers to the supporting force exerted by the face on the tunnel profile. It can be obtained through literature research or formula derivation. The formula is as follows:

[0090] ;

[0091] ;

[0092] ;

[0093] in, is the calculation function of virtual support force; is the virtual support force, (Pa); is the friction angle of surrounding rock, (°); is the cohesion of surrounding rock, (Pa); is the tunnel radius, (m); is the maximum plastic zone radius of the tunnel, (m); is the distance from the tunnel face, (m); is the distance from the tunnel face when the plastic zone just appears, (m); is the calculation function of the maximum plastic zone radius of the tunnel; is the calculation function of the distance from the tunnel face when the plastic zone just appears;

[0094] S24. The spatial effect of the active support rock anchor arch is characterized by the equivalent elastic modulus, friction angle, and cohesion calculation formulas for the rock anchor arch formed by the prestressed anchor and surrounding rock after the prestressed anchor is applied. The calculation formulas for the equivalent elastic modulus, friction angle, and cohesion of the rock anchor arch can be obtained through theoretical derivation or data fitting, and are as follows:

[0095] ;

[0096] ;

[0097] ;

[0098] in, is the calculation function of the equivalent friction angle of the rock anchor bearing arch; is the equivalent friction angle of the rock anchor bearing arch, (°); is the diameter of the anchor rod, (m); is the friction resistance coefficient between the anchor and the surrounding rock; is the longitudinal spacing of anchor rods, (m); is the circumferential spacing of anchor rods, (m); is the calculation function of the equivalent cohesion of the rock-anchored bearing arch; is the equivalent cohesion of the rock anchor bearing arch, (Pa); is the anchor rod prestress value, (kN); is the calculation function of the equivalent elastic modulus of the rock anchor bearing arch; is the equivalent elastic modulus of the rock anchor bearing arch, (Pa); is the elastic modulus of surrounding rock, (Pa); is the elastic modulus of the anchor rod, (Pa).

[0099] S3, such as Figure 2 As shown in the figure, a spatiotemporal calculation model of the coordinated effect of rock bolting and shotcrete in active tunnel support is established. The specific steps are as follows:

[0100] S31. Based on the active support reinforcement mechanism, prestressed anchors are applied to improve the mechanical parameters of the surrounding rock to form a rock-anchor bearing arch;

[0101] S32. Shotcrete plays a protective role on the rock anchor bearing arch and jointly bears the surrounding rock pressure, and establishes a spatiotemporal calculation model of active support rock-anchor-shotcrete synergistic effect;

[0102] In the spatiotemporal calculation model of active support rock-anchor-shotcrete synergy, beam elements are used to simulate both the rock-anchor bearing arch and the shotcrete layer. The two structures are connected by radial compression-only springs and tangential springs to represent the radial and tangential bonding between the shotcrete layer and the surrounding rock. The rock-anchor bearing arch and the surrounding rock are connected by radial compression-only springs. The bottom of the rock-anchor bearing arch and the shotcrete layer are constrained and fixed with hinged supports, and a virtual support force is applied to the bottom of the rock-anchor bearing arch to account for the spatial effect of the tunnel face.

[0103] S4. Determine the calculation parameters of the rock anchor bearing arch based on the spatiotemporal calculation model of the rock anchor shotcrete synergistic effect of active tunnel support. The specific steps are as follows:

[0104] S41. Determine the rock anchor bearing arch thickness and set it as the anchor rod length L ;

[0105] S42. Calculate the equivalent elastic modulus, friction angle, and cohesion of the rock anchor bearing arch based on the spatial effect characterization method of the active support rock anchor bearing arch;

[0106] S43. Calculate the virtual support force borne by the rock anchor bearing arch based on the spatial effect characterization method of the active support tunnel face;

[0107] S44. Determine the spring reaction coefficient between the rock anchor bearing arch and the surrounding rock. The spring reaction coefficient specified in the Railway Tunnel Design Code can be selected.

[0108] S5. Determine the calculation parameters of the shotcrete layer based on the spatiotemporal calculation model of the rock-bolt-shotcrete synergy in active tunnel support. The specific steps are as follows:

[0109] S51. Determine the thickness of the sprayed layer and select it according to the thickness of the sprayed concrete;

[0110] S52. Calculate the elastic modulus of shotcrete at different times based on the time effect characterization method of active support materials;

[0111] S53. Determine the spring reaction coefficient between the shotcrete layer and the rock anchor bearing arch. The spring reaction coefficient specified in the Railway Tunnel Design Code can be selected.

[0112] S6. Establish a calculation method for tunnel surrounding rock pressure taking into account the effect of advance support;

[0113] Considering the effect of advanced pipe-roof pre-support on reducing the overburden load on the surrounding rock, the calculation formula for the surrounding rock pressure borne on the outside of the rock anchor bearing arch is modified as follows:

[0114] ;

[0115] ;

[0116] ;

[0117] in, is the calculation function of the vertical surrounding rock pressure on the outer side of the rock anchor bearing arch; is the vertical surrounding rock pressure on the outer side of the rock anchor bearing arch, (Pa); Correction coefficient for surrounding rock pressure after tunnel construction with advanced pipe roof; is the surrounding rock mass, (kN / m 3 ); To calculate the height, (m); is the calculation function for calculating the height; is the surrounding rock level; is the width influence coefficient; is the calculation function of the horizontal surrounding rock pressure on the outer side of the rock anchor bearing arch; is the horizontal surrounding rock pressure on the outer side of the rock anchor bearing arch (Pa); is the lateral pressure coefficient.

[0118] S7. Establish a safety evaluation method for active support rock anchor bearing arch and shotcrete layer in tunnels. The specific steps are as follows:

[0119] S71. Based on the spatiotemporal calculation model for the coordinated action of rock-bolt and shotcrete in active tunnel support, the bending moment and axial force of the rock-bolt bearing arch are calculated and converted to the safety factor of the rock-bolt bearing arch. Considering the large thickness of the rock-bolt bearing arch and the generally small eccentric stress state, the formula is as follows:

[0120] ;

[0121] ;

[0122] ;

[0123] in, is the calculation function of the safety factor of the rock anchor bearing arch; is the rock anchor bearing arch safety factor; is the arch axial force carried by the rock anchor, (N); is the longitudinal bending coefficient of the section; is the axial force eccentricity influence coefficient; is the compressive strength of the rock anchor bearing arch, (Pa); Calculate the width of the rock anchor bearing arch (m); is the thickness of the rock anchor bearing arch, (m); is the calculation function of the compressive strength of the rock anchor bearing arch;

[0124] S72. Calculate the bending moment and axial force of the shotcrete layer based on the spatiotemporal calculation model of rock-bolt-shotcrete synergy in active tunnel support, and convert the safety factor of the shotcrete layer into the following formula:

[0125] ;

[0126] ;

[0127] in, is the safety factor when the spray layer is under pressure; is the calculation function of the compressive safety factor of shotcrete; is the longitudinal bending coefficient; is the eccentricity influence coefficient of the axial force; is the ultimate compressive strength of shotcrete, (Pa); is the ultimate tensile strength of shotcrete, (Pa); is the axial force of the spray layer, (N); is the longitudinal depth of the spray layer, (m); is the height of the spray layer, (m); is the radial safety factor of shotcrete under compression; is the calculation function of the tensile safety factor of shotcrete; is the bending moment of the spray layer (Nm).

[0128] S8. Determine the safety of the rock-anchor bearing arch and shotcrete layer based on the calculation results of the spatiotemporal calculation model of the rock-bolt-shotcrete synergy in active tunnel support;

[0129] S9. Determine the design parameters of prestressed anchor rods and shotcrete based on the calculation results of the spatiotemporal calculation model of the synergistic effect of rock-bolt-shotcrete in active tunnel support.

[0130] It is worth noting that the contents not elaborated in detail in the present invention are all prior art and are well known to those skilled in the art.

[0131] Therefore, the present invention provides a spatiotemporal design method for the synergistic effect of rock-anchor and shotcrete in active support for railway tunnels that considers spatiotemporal effects. By establishing a spatiotemporal calculation model for the synergistic effect of rock-anchor and shotcrete in active support for tunnels, and comprehensively considering active support spatiotemporal effects such as load time effect, material time effect, tunnel face spatial effect, and rock-anchor bearing arch spatial effect, the present invention provides a spatiotemporal design method for the synergistic effect of rock-anchor and shotcrete in active support for railway tunnels using a rock-anchor bearing arch and shotcrete safety evaluation method. This method can simply, quickly, and accurately calculate the internal force distribution and safety of the tunnel rock-anchor bearing arch and shotcrete layer under different time, geological conditions, and support design parameters. Ordinary designers can use this method to design tunnel projects using active support systems using prestressed anchors and shotcrete, thus demonstrating its excellent engineering value.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A temporal and spatial design method for the coordinated action of rock bolting and shotcrete in railway tunnel active support considering temporal and spatial effects, characterized in that: The specific steps are as follows: Step S1: clarify the characteristics of the temporal and spatial effects of active support, including load time effect, material time effect, tunnel face spatial effect, and rock anchor bearing arch spatial effect; Step S2: establishing a method for characterizing the temporal and spatial effects of active support based on the temporal and spatial effects of active support; Step S3: establishing a spatiotemporal calculation model for the coordinated effect of rock bolting and shotcrete in active tunnel support; Step S4, determining the calculation parameters of the rock anchor bearing arch according to the spatiotemporal calculation model of the rock anchor shotcrete synergistic effect of active tunnel support; Step S5, determining the calculation parameters of the shotcrete layer according to the spatiotemporal calculation model of the rock-bolt-shotcrete synergy in active tunnel support; Step S6: establishing a calculation method for tunnel surrounding rock pressure taking into account the effect of advance support; Step S7: establishing a safety evaluation method for tunnel active support rock anchor bearing arch and shotcrete layer; Step S8: judging the safety of the rock anchor bearing arch and the shotcrete layer according to the calculation results of the spatiotemporal calculation model of the rock anchor shotcrete synergy in the tunnel active support; Step S9: determining the design parameters of prestressed anchor rods and shotcrete according to the calculation results of the spatiotemporal calculation model of the rock-bolt-shotcrete synergy for active tunnel support; In step S3, the specific steps for establishing a spatiotemporal calculation model for the coordinated action of rock bolting and shotcrete in active tunnel support are as follows: Step S31: Based on the active support reinforcement mechanism, prestressed anchor rods are applied to improve the mechanical parameters of the surrounding rock to form a rock anchor bearing arch; Step S32: The shotcrete acts as a surface protector for the rock anchor bearing arch and bears the surrounding rock pressure together, thereby establishing a spatiotemporal calculation model for the active support rock-anchor-shotcrete synergistic effect; Step S33: In the active support rock-anchor-shotcrete synergistic spatiotemporal calculation model, both the rock anchor bearing arch and the shotcrete layer are simulated using beam units. The two structures are connected by radial compression-only springs and tangential springs. The rock anchor bearing arch and the surrounding rock are connected by radial compression-only springs. The rock anchor bearing arch and the bottom of the shotcrete layer are constrained and fixed by hinged supports, and a virtual support force is applied to the bottom of the rock anchor bearing arch.

2. A temporal and spatial design method for active support rock bolting and shotcrete in railway tunnels considering temporal and spatial effects according to claim 1, characterized in that: In step S2, the specific steps for establishing the characterization method of the temporal and spatial effects of active support are as follows: Step S21: The time effect of active support load is characterized by a deformation load calculation formula that considers time development. The formula is as follows: ； ； in, is the calculation function of the vertical pressure of deformation load changing with time, For time, and are the load reduction coefficient and lateral pressure coefficient reduction coefficient obtained by fitting the field measured data, is the vertical pressure value of deformation load, is the vertical pressure value of the surrounding rock calculated according to the railway tunnel design specifications, are the fitting parameters obtained based on the field measured data. is the calculation function of the deformation load horizontal pressure changing with time, is the horizontal pressure value of the deformation load, is the lateral pressure coefficient determined according to the railway tunnel design specifications; Step S22: The time effect of the active support material is characterized by the calculation formula of the elastic modulus, compressive strength and tensile strength of the shotcrete considering the time development. The formula is as follows: ； ； ； in, is the calculation function of the compressive strength of tunnel shotcrete changing with time, Shotcrete for tunnels The compressive strength of the moment, The compressive strength of the tunnel shotcrete at the final moment, is the calculation function of the change of tunnel shotcrete tensile strength over time, Shotcrete for tunnels The tensile strength at the moment, is the calculation function of the elastic modulus of tunnel shotcrete changing with time, Shotcrete for tunnels The elastic modulus at the moment, is the elastic modulus of the tunnel shotcrete at the final moment; Step S23: The spatial effect of the active support face is characterized by introducing a virtual support force calculation formula, which is as follows: ； ； ； in, is the calculation function of the virtual support force, is the virtual support force, is the surrounding rock friction angle, is the cohesion of surrounding rock, is the tunnel radius, is the maximum plastic zone radius of the tunnel, x is the distance from the tunnel face, is the distance from the tunnel face when the plastic zone just appears, is the calculation function of the maximum plastic zone radius of the tunnel, is the calculation function of the distance from the tunnel face when the plastic zone just appears; Step S24: The spatial effect of the active support rock anchor bearing arch is characterized by the equivalent elastic modulus, friction angle, and cohesion calculation formula of the rock anchor bearing arch formed by the prestressed anchor and the surrounding rock after the prestressed anchor is applied. The formula is as follows: ； ； ； in, is the calculation function of the equivalent friction angle of the rock anchor bearing arch, is the equivalent friction angle of the rock anchor bearing arch, is the anchor diameter, is the friction resistance coefficient between the anchor and the surrounding rock, is the longitudinal spacing of anchor rods, is the circumferential spacing of anchor rods, is the calculation function of the equivalent cohesion of the rock anchor bearing arch, is the equivalent cohesion of the rock anchor bearing arch, is the anchor rod prestress value, is the calculation function of the equivalent elastic modulus of the rock anchor bearing arch, is the equivalent elastic modulus of the rock anchor bearing arch, is the elastic modulus of the surrounding rock, is the elastic modulus of the anchor rod.

3. The temporal and spatial design method for active support rock bolting and shotcrete in railway tunnels considering temporal and spatial effects according to claim 1 is characterized in that: In step S4, the calculation parameters of the rock anchor bearing arch are determined. The specific steps are as follows: Step S41: Determine the rock anchor bearing arch thickness and set it as the anchor rod length L ; Step S42: Calculate the equivalent elastic modulus, friction angle, and cohesion of the rock anchor bearing arch according to the spatial effect characterization method of the active support rock anchor bearing arch; Step S43: Calculate the virtual support force borne by the rock anchor bearing arch according to the active support tunnel face spatial effect characterization method; Step S44: Determine the spring reaction coefficient between the rock anchor bearing arch and the surrounding rock.

4. The temporal and spatial design method for active support rock bolting and shotcrete in railway tunnels considering temporal and spatial effects according to claim 1 is characterized in that: In step S5, the calculation parameters of the shotcrete layer are determined, and the specific steps are as follows: Step S51, determine the thickness of the sprayed layer, and select it according to the thickness of the sprayed concrete; Step S52: Calculate the elastic modulus of shotcrete at different times according to the time effect characterization method of active support materials; Step S53: Determine the spring reaction coefficient between the spray layer and the rock anchor bearing arch.

5. The temporal and spatial design method for active support rock bolting and shotcrete in railway tunnels considering temporal and spatial effects according to claim 1 is characterized in that: In step S6, the effect of the advanced pipe-roof pre-support on reducing the overburden load on the surrounding rock is taken into account, and the calculation formula for the surrounding rock pressure borne on the outside of the rock anchor bearing arch is modified to be as follows: ； ； ； in, is the calculation function of the vertical surrounding rock pressure on the outer side of the rock anchor bearing arch; is the vertical surrounding rock pressure value borne by the outer side of the rock anchor bearing arch, It is the correction coefficient of surrounding rock pressure after the tunnel is constructed with advanced pipe roof. The surrounding rock is heavy. To calculate the height, is the calculation function for calculating the height, The surrounding rock level, is the width influence coefficient, is the calculation function of the horizontal surrounding rock pressure on the outside of the rock anchor bearing arch, is the horizontal surrounding rock pressure value borne by the outer side of the rock anchor bearing arch, is the lateral pressure coefficient.

6. The temporal and spatial design method for active support of railway tunnels by rock bolting and shotcrete in consideration of temporal and spatial effects according to claim 1 is characterized in that: In step S7, a safety evaluation method for the active support rock anchor bearing arch and shotcrete layer of the tunnel is established. The specific steps are as follows: Step S71: Calculate the bending moment and axial force of the rock anchor bearing arch based on the spatiotemporal calculation model of rock anchor shotcrete synergy for active tunnel support, and convert the safety factor of the rock anchor bearing arch into the following formula: ； ； in, is the calculation function of the rock anchor bearing arch safety factor, is the rock anchor bearing arch safety factor, The rock anchor bears the arch axial force. is the longitudinal bending coefficient of the section, is the axial force eccentricity influence coefficient, is the compressive strength of the rock anchor bearing arch, Calculate the width of the rock anchor bearing arch, is the thickness of the rock anchor bearing arch, is the calculation function of the compressive strength of the rock anchor bearing arch; Step S72: Calculate the bending moment and axial force of the shotcrete layer based on the spatiotemporal calculation model of the rock-bolt-shotcrete synergistic effect of active tunnel support, and convert the calculated safety factor of the shotcrete layer into the following formula: ； ； in, is the safety factor when the spray layer is under pressure, is the calculation function of the compressive safety factor of shotcrete, is the longitudinal bending coefficient, is the eccentricity influence coefficient of the axial force, is the ultimate compressive strength of shotcrete, is the ultimate tensile strength of shotcrete, is the axial force of the spray layer, is the longitudinal depth of the spray layer, is the height of the spray layer, is the radial safety factor of shotcrete under compression, is the calculation function of the tensile safety factor of shotcrete, is the bending moment of the spray layer.

Images