A method for calculating vertical surrounding rock pressure of tunnel arch support and surrounding rock debonding

Abstract

The present invention discloses a method for calculating the vertical surrounding rock pressure of tunnel vault support and surrounding rock de-hollowing, including detecting the cavity behind the lining of the tunnel vault area, obtaining the position and size information of the tunnel vault de-hollowing area, obtaining the standard value of the tunnel vault vertical pressure, determining the influence range of the tunnel vault de-hollowing area, calculating the maximum vertical surrounding rock pressure in the vault de-hollowing area along the tunnel axis, and calculating the maximum vertical surrounding rock pressure outside the vault de-hollowing area along the tunnel axis. The present invention fully considers the three-dimensional characteristics of the change in the distribution of surrounding rock pressure when de-hollowing or cavity exists, and introduces the influence range of the tunnel vault de-hollowing area into the calculation method, which can more comprehensively evaluate the safety of the lining structure when the support and surrounding rock are de-hollowed, so that the load-structure model is more comprehensive and reasonable in the calculation of the "cavity behind the lining structure or the support surrounding rock de-hollowing problem".

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a method for calculating vertical surrounding rock pressure of tunnel arch support and surrounding rock de-entrapment. Background Art

[0002] At present, the tunnel structure design and internal force calculation models include: empirical analogy model, load-structure model and stratum-structure model. Among them, the load-structure model assumes that the load on the lining structure is all from the stratum, and the lining generates internal force and deformation under the action of load. Different from the load-structure method, the stratum-structure method regards the lining and stratum as a whole, and uses numerical simulation to calculate the internal forces of the lining and stratum respectively on the premise of satisfying the deformation coordination conditions, and verifies the stability of the stratum and designs the cross-section of the components based on it. The structural internal force calculated by the load-structure model is usually greater than the calculation result of the stratum-structure model. In view of the fact that the large-scale three-dimensional numerical simulation based on the stratum-structure method is relatively complex and inconvenient for designers to use, the load-structure method, as a two-dimensional design method, is a calculation method recommended in the design specification due to its clear mechanical concept, simple modeling and convenient application. It is currently more commonly used.

[0003] However, during the tunnel construction process, due to the quality defects of lining construction, over-excavation and under-excavation, uneven initial support surface and other reasons, poor contact between the support and surrounding rock frequently occurs. "Contact problem" refers to the problem of voids due to poor bonding and solidification between the support and the surrounding rock. As the most common form of poor contact between the support and the surrounding rock, the voids behind the lining are prone to cause loosening of the surrounding rock, increased earth pressure, reduced lining strength, and cracking of the lining, thereby causing a series of hazards such as water leakage and landslides. The existence of poor contact between the support and the surrounding rock shortens the daily maintenance and repair time and service life of the tunnel, and seriously threatens the health and safety of tunnel operation. In recent years, with the gradual increase in the phenomenon of poor contact behind the tunnel lining, according to on-site inspection and investigation data, the loose area and void area behind the tunnel lining are the main problems in the later operation and maintenance of tunnel construction, and are common, accounting for about 10% of the inspected tunnels.

[0004] Regarding the problem of support and surrounding rock voids or cavities behind the lining, based on the load-structure model, some scholars have calculated the influence of voids on the internal force and deformation of the structure, and considered the concentrated effect of surrounding rock pressure load caused by voids, and proposed a modified load-structure model. However, voids have three-dimensional characteristics of length, width, and height, and their influence on the internal force of the lining structure has a certain range. Therefore, the influence of voids on the internal force of the lining structure along the longitudinal direction of the tunnel in the void area is also variable, and the internal force of the lining structure on both sides of the void outside the void area also has stress concentration. The existing method only analyzes the problem of support and surrounding rock voids or voids from a two-dimensional perspective, and cannot fully reflect the influence of voids on the lining structure. The calculation results only consider the changes in surrounding rock pressure on both sides of the void, and fail to consider the influence along the longitudinal direction of the tunnel. Only the surrounding rock pressure at the center of the void or void area is clarified, and it is only applicable to the calculation of the internal force of the lining structure at this position. Therefore, the current method has the problems of incomplete consideration, large calculation range limitations, and cannot comprehensively evaluate the safety of the lining structure. Summary of the invention

[0005] The present invention aims to provide a method for calculating the vertical surrounding rock pressure of tunnel vault support and surrounding rock de-bonding, so as to solve the technical problems described in the background technology.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A method for calculating the vertical surrounding rock pressure of tunnel vault support and surrounding rock de-bonding comprises the following steps:

[0008] Step 1: Detect the void behind the lining in the tunnel vault area to obtain the position and size information of the void area in the tunnel vault, wherein the size information includes the void length l and the void width d;

[0009] Step 2: According to the tunnel design data, calculate the standard value q of the vertical pressure on the tunnel crown.

[0010]

[0011] Where q is the standard value of the vertical pressure on the tunnel vault, in kN / m 2 , γ is the weight of surrounding rock, unit is kN / m 3 , h is the buried depth of the tunnel vault, in m, θ is the friction angle on both sides of the tunnel vault soil column, in °, D is the tunnel diameter span, in m, λ is the lateral pressure coefficient, and the calculation formula is as follows,

[0012]

[0013] Where β is the fracture angle of the surrounding rock, in degrees, is the friction angle of the surrounding rock, in degrees, θ is the friction angle on both sides of the tunnel vault soil column, in degrees, and the tangent value of the crushing angle β is calculated according to the following formula:

[0014]

[0015] Where β is the fracture angle of the surrounding rock, in degrees, is the friction angle calculated for the surrounding rock, in degrees, and θ is the friction angle on both sides of the soil column of the tunnel vault, in degrees;

[0016] Step 3, determine the impact range a of the tunnel vault void area;

[0017] Step 4: Calculate the maximum vertical surrounding rock pressure q in the arch void area along the tunnel axis. X ,

[0018]

[0019] Among them, q X The maximum value of the vertical surrounding rock pressure on the tunnel vault along the tunnel axis, in kN / m 2 , X is the coordinate value corresponding to the position of each tunnel cross section extending along the tunnel axis direction with the center point of the tunnel vault hollow area as the origin of the coordinate axis. Its physical meaning is the horizontal distance between the position of each cross section of the tunnel vault and the center position of the tunnel vault hollow area, in m, and its positive and negative signs are determined according to the depth direction of the tunnel. l is the tunnel vault hollow length, in m, d is the tunnel vault hollow width, in m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2 , a is the impact range of the tunnel vault void area, in m;

[0020] Step 5: Calculate the maximum vertical surrounding rock pressure q outside the arch void area along the tunnel axis direction X ,

[0021]

[0022] Among them, q X The maximum value of the vertical surrounding rock pressure on the tunnel vault along the tunnel axis, in kN / m 2 , X is the coordinate value corresponding to the position of each tunnel cross section extending along the tunnel axis direction with the center point of the tunnel vault hollow area as the origin of the coordinate axis. Its physical meaning is the horizontal distance between the position of each cross section of the tunnel vault and the center position of the tunnel vault hollow area, in m, and its positive and negative signs are determined according to the depth direction of the tunnel. l is the tunnel vault hollow length, in m, d is the tunnel vault hollow width, in m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2, a is the impact range of the tunnel vault void area, in m.

[0023] Preferably, the derivation process of formula (4) and formula (5) includes the following steps:

[0024] Step S1, establishing three-dimensional stratum-structure models in two cases where there is a void area and there is no void area on the back vault of the tunnel support, and obtaining the three-dimensional mechanical response law of the lining structure through finite element calculation and analysis;

[0025] Step S2, comparing and analyzing the three-dimensional mechanical response laws of the back arch of the tunnel support under two conditions: the presence of a void area and the absence of a void area;

[0026] Step S3: According to the comparative analysis results of step S2, the load in the empty area is in the shape of a cuboid, and the corresponding load expression is:

[0027] V c =l·d·q (6)

[0028] Among them, V c is the load value of the tunnel vault void area, in kN, l is the tunnel vault void length, in m, d is the tunnel vault void width, in m, q is the standard value of the tunnel vault vertical pressure, in kN / m 2 According to the stress concentration effect, the stress concentration load distribution around the void area is pyramid-shaped, and the corresponding load expression is:

[0029]

[0030]

[0031] Among them, V n is the sum of the stress concentration loads within the influence range around the tunnel vault void area, in kN, and S is the load bottom area, in m 2 ,h q is the load height, in kN / m 2 , l is the length of the tunnel vault void, in m, d is the width of the tunnel vault void, in m, a is the influence range of the tunnel vault void area, in m, k is the slope of the vertical pressure increase section in the longitudinal cross section at the center of the tunnel vault void area, in kN / m, q is the standard value of the tunnel vault vertical pressure, in kN / m 2 ,q max The maximum vertical pressure in the longitudinal cross section at the center of the tunnel vault void area, in kN / m 2 ;

[0032] Step S4, according to the equivalent load theory, the distributed stress corresponding to the hollow area is transferred to the surrounding of the hollow area, and it can be obtained that:

[0033] V c =V n (9)

[0034] Right now,

[0035]

[0036] From this we can get,

[0037]

[0038]

[0039] Step S5, according to formula (12), the calculation formula of the change slope k′ of the maximum vertical pressure in the tunnel vault void area along the tunnel axis direction is:

[0040]

[0041] Step S6, taking the center point of the tunnel vault hollow area as the origin of the coordinate axis, establish a one-dimensional coordinate along the tunnel axis direction, and the coordinate value of each point on the coordinate axis is represented by X. When X=0, q X Get the maximum value q max , when -0.5l<X<0.5l and X≠0, q X As k′ decreases toward both sides, the maximum vertical surrounding rock pressure q in the arch void area along the tunnel axis direction X The calculation formula is,

[0042]

[0043] When 0.5l<|X|<0.5l+a, q X As k decreases toward both sides, the maximum vertical surrounding rock pressure q outside the arch void area along the tunnel axis X The calculation formula is,

[0044]

[0045] Where, l is the length of the tunnel vault void, in m, d is the width of the tunnel vault void, in m, a is the influence range of the tunnel vault void area, in m, k is the slope of the vertical pressure increase section in the longitudinal cross section at the center of the tunnel vault void area, in kN / m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2 ,q max The maximum vertical pressure in the longitudinal cross section at the center of the tunnel vault void area, in kN / m 2 .

[0046] Preferably, the influence range a of the tunnel vault hollowing area is equal to the width of the tunnel vault hollowing area.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention fully considers the three-dimensional characteristics of the change in surrounding rock pressure distribution when voids or cavities exist, and introduces the influence range of the tunnel vault void area into the calculation method, which can more comprehensively evaluate the safety of the lining structure when the support and surrounding rock are voided, making the load-structure model more reasonable and more in line with the actual situation in the calculation of the "voids behind the lining structure or the voiding of the supporting surrounding rock". The calculation results of the model corrected by this calculation method can fully reflect the changing law of the force of the lining structure inside and outside the void area, and can provide stable and reliable assistance for the lining structure design, structural internal force calculation and quality and safety assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The above and / or other aspects and advantages of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings, which are only exemplary and do not limit the present invention, wherein:

[0049] Figure 1 A comparison diagram of the three-dimensional stratum-structure model in two cases where there is a void area and there is no void area in the back vault of the tunnel support involved in the present invention;

[0050] Figure 2 It is a schematic diagram of the surrounding rock pressure variation law and surrounding rock load distribution model in a three-dimensional stratum-structure model when there is a void area on the back arch of the tunnel support involved in the present invention;

[0051] Figure 3 for Figure 2 Schematic diagram of the variation of the maximum vertical surrounding rock pressure in the arch void area along the tunnel axis in the corresponding three-dimensional stratum-structure model;

[0052] Figure 4 for Figure 2 Schematic diagram of the variation of the maximum vertical surrounding rock pressure outside the arch void area along the tunnel axis in the corresponding three-dimensional stratum-structure model;

[0053] Figure 5 for Figure 2 Schematic diagram of the distribution of vertical pressure in the left half of the cross section at the center of the tunnel vault void area in the three-dimensional stratum-structure model;

[0054] Figure 6 for Figure 2 Schematic diagram of the distribution of vertical pressure on the front side of the longitudinal section at the center of the tunnel vault void area in the three-dimensional stratum-structure model. DETAILED DESCRIPTION

[0055] Hereinafter, an embodiment of a method for calculating vertical surrounding rock pressure of tunnel vault support and surrounding rock de-entrapment of the present invention will be described with reference to the accompanying drawings. The embodiments described herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention, are explanatory and exemplary, and should not be construed as limitations on the embodiments of the present invention and the scope of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims and specification of the present application, including technical solutions that adopt any obvious replacements and modifications to the embodiments described herein.

[0056] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by terms such as “longitudinal”, “horizontal”, “top”, “bottom”, “inside” and “outside” are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0057] The drawings of this specification are schematic diagrams, which assist in explaining the concept of the present invention and schematically show the shapes of various parts and their mutual relationships. Please note that in order to clearly show the structures of various components of the embodiments of the present invention, the drawings are not drawn according to the same scale. The same reference numerals are used to represent the same parts.

[0058] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The embodiments are only used to explain the present invention and are not used to limit the scope of the present invention. Figure 1-4 , the preferred embodiments of the present invention are further described in detail:

[0059] like Figure 1-4 As shown, a preferred method for calculating the vertical surrounding rock pressure of a tunnel vault support and surrounding rock de-bonding of the present invention comprises the following steps:

[0060] Step 1: Detect the void behind the lining in the tunnel vault area to obtain the position and size information of the void area in the tunnel vault, wherein the size information includes the void length l and the void width d;

[0061] Step 2: According to the tunnel design data, calculate the standard value q of the vertical pressure on the tunnel crown.

[0062]

[0063] Where q is the standard value of the vertical pressure on the tunnel vault, in kN / m 2 , γ is the weight of surrounding rock, unit is kN / m 3, h is the buried depth of the tunnel vault, in m, θ is the friction angle on both sides of the tunnel vault soil column, in °, D is the tunnel diameter span, in m, λ is the lateral pressure coefficient, and the calculation formula is as follows,

[0064]

[0065] Where β is the fracture angle of the surrounding rock, in degrees, is the friction angle of the surrounding rock, in degrees, θ is the friction angle on both sides of the tunnel vault soil column, in degrees, and the tangent value of the crushing angle β is calculated according to the following formula:

[0066]

[0067] Where β is the fracture angle of the surrounding rock, in degrees, is the friction angle calculated for the surrounding rock, in degrees, and θ is the friction angle on both sides of the soil column of the tunnel vault, in degrees;

[0068] Step 3, determine the impact range a of the tunnel vault void area;

[0069] Step 4: Calculate the maximum vertical surrounding rock pressure q in the arch void area along the tunnel axis. X ,

[0070]

[0071] Among them, q X The maximum value of the vertical surrounding rock pressure on the tunnel vault along the tunnel axis, in kN / m 2 , X is the coordinate value corresponding to the position of each tunnel cross section extending along the tunnel axis direction with the center point of the tunnel vault hollow area as the origin of the coordinate axis. Its physical meaning is the horizontal distance between the position of each cross section of the tunnel vault and the center position of the tunnel vault hollow area, in m, and its positive and negative signs are determined according to the depth direction of the tunnel. l is the tunnel vault hollow length, in m, d is the tunnel vault hollow width, in m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2 , a is the impact range of the tunnel vault void area, in m;

[0072] Step 5: Calculate the maximum vertical surrounding rock pressure q outside the arch void area along the tunnel axis direction X ,

[0073]

[0074] Among them, q X The maximum value of the vertical surrounding rock pressure on the tunnel vault along the tunnel axis, in kN / m 2, X is the coordinate value corresponding to the position of each tunnel cross section extending along the tunnel axis direction with the center point of the tunnel vault hollow area as the origin of the coordinate axis. Its physical meaning is the horizontal distance between the position of each cross section of the tunnel vault and the center position of the tunnel vault hollow area, in m, and its positive and negative signs are determined according to the depth direction of the tunnel. l is the tunnel vault hollow length, in m, d is the tunnel vault hollow width, in m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2 , a is the impact range of the tunnel vault void area, in m.

[0075] The derivation process of formula (4) and formula (5) includes the following steps:

[0076] Step S1, establishing three-dimensional stratum-structure models in two cases where there is a void area and there is no void area on the back vault of the tunnel support, and obtaining the three-dimensional mechanical response law of the lining structure through finite element calculation and analysis;

[0077] Step S2, comparing and analyzing the three-dimensional mechanical response laws of the back arch of the tunnel support under two conditions: the presence of a void area and the absence of a void area;

[0078] Step S3: According to the comparative analysis results of step S2, the load in the empty area is in the shape of a cuboid, and the corresponding load expression is:

[0079] V c =l·d·q (6)

[0080] Among them, V c is the load value of the tunnel vault void area, in kN, l is the tunnel vault void length, in m, d is the tunnel vault void width, in m, q is the standard value of the tunnel vault vertical pressure, in kN / m 2 According to the stress concentration effect, the stress concentration load distribution around the void area is pyramid-shaped, and the corresponding load expression is:

[0081]

[0082]

[0083] Among them, V n is the sum of the stress concentration loads within the influence range around the tunnel vault void area, in kN, and S is the load bottom area, in m 2 ,h q is the load height, in kN / m 2, l is the length of the tunnel vault void, in m, d is the width of the tunnel vault void, in m, a is the influence range of the tunnel vault void area, in m, k is the slope of the vertical pressure increase section in the longitudinal cross section at the center of the tunnel vault void area, in kN / m, q is the standard value of the tunnel vault vertical pressure, in kN / m 2 ,q max The maximum vertical pressure in the longitudinal cross section at the center of the tunnel vault void area, in kN / m 2 ;

[0084] Step S4, according to the equivalent load theory, the distributed stress corresponding to the hollow area is transferred to the surrounding of the hollow area, and it can be obtained that:

[0085] V c =V n (9)

[0086] Right now,

[0087]

[0088] From this we can get,

[0089]

[0090]

[0091] Step S5, according to formula (12), the calculation formula of the change slope k′ of the maximum vertical pressure in the tunnel vault void area along the tunnel axis direction is:

[0092]

[0093] Step S6, taking the center point of the tunnel vault hollow area as the origin of the coordinate axis, establish a one-dimensional coordinate along the tunnel axis direction, and the coordinate value of each point on the coordinate axis is represented by X. When X=0, q X Get the maximum value q max , when -0.5l<X<0.5l and X≠0, q X As k′ decreases toward both sides, the maximum vertical surrounding rock pressure q in the arch void area along the tunnel axis direction X The calculation formula is,

[0094]

[0095] When 0.5l<|X|<0.5l+a, q X As k decreases toward both sides, the maximum vertical surrounding rock pressure q outside the arch void area along the tunnel axis X The calculation formula is,

[0096]

[0097] Where, l is the length of the tunnel vault void, in m, d is the width of the tunnel vault void, in m, a is the influence range of the tunnel vault void area, in m, k is the slope of the vertical pressure increase section in the longitudinal cross section at the center of the tunnel vault void area, in kN / m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2 ,q max The maximum vertical pressure in the longitudinal cross section at the center of the tunnel vault void area, in kN / m 2 ;

[0098] The influence range a of the tunnel vault hollow area is equal to the width of the tunnel vault hollow area. When specifically obtaining it, it is necessary to establish multiple groups of calculation models in step S1 by gradually increasing the hollow area, and calculate through finite element analysis, and statistically summarize the relationship between the size of the influence range of the tunnel vault hollow area in each group of calculation models and the length and width of the hollow area to obtain it.

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

Claims

1. A method for calculating the vertical surrounding rock pressure of tunnel vault support and surrounding rock de-bonding, characterized in that: The steps include: Step 1: Detect the void behind the lining in the tunnel vault area to obtain the position and size information of the void area in the tunnel vault, wherein the size information includes the void length l and the void width d; Step 2: According to the tunnel design data, calculate the standard value q of the vertical pressure on the tunnel crown. Where q is the standard value of the vertical pressure on the tunnel vault, in kN / m 2 , γ is the weight of surrounding rock, unit is kN / m 3 , h is the buried depth of the tunnel vault, in m, θ is the friction angle on both sides of the tunnel vault soil column, in °, D is the tunnel diameter span, in m, λ is the lateral pressure coefficient, and the calculation formula is as follows, Where β is the fracture angle of the surrounding rock, in degrees, is the friction angle of the surrounding rock, in degrees, θ is the friction angle on both sides of the tunnel vault soil column, in degrees, and the tangent value of the crushing angle β is calculated according to the following formula: Where β is the fracture angle of the surrounding rock, in degrees, is the friction angle calculated for the surrounding rock, in degrees, and θ is the friction angle on both sides of the soil column of the tunnel vault, in degrees; Step 3, determine the impact range a of the tunnel vault void area; Step 4: Calculate the maximum vertical surrounding rock pressure q in the arch void area along the tunnel axis. X , Among them, q X The maximum value of the vertical surrounding rock pressure on the tunnel vault along the tunnel axis, in kN / m 2 , X is the coordinate value corresponding to the position of each tunnel cross section extending along the tunnel axis direction with the center point of the tunnel vault hollow area as the origin of the coordinate axis. Its physical meaning is the horizontal distance between the position of each cross section of the tunnel vault and the center position of the tunnel vault hollow area, in m, and its positive and negative signs are determined according to the depth direction of the tunnel. l is the tunnel vault hollow length, in m, d is the tunnel vault hollow width, in m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2 , a is the impact range of the tunnel vault void area, in m; Step 5: Calculate the maximum vertical surrounding rock pressure q outside the arch void area along the tunnel axis direction X , Among them, q X The maximum value of the vertical surrounding rock pressure on the tunnel vault along the tunnel axis, in kN / m 2 , X is the coordinate value corresponding to the position of each tunnel cross section extending along the tunnel axis direction with the center point of the tunnel vault hollow area as the origin of the coordinate axis. Its physical meaning is the horizontal distance between the position of each cross section of the tunnel vault and the center position of the tunnel vault hollow area, in m, and its positive and negative signs are determined according to the depth direction of the tunnel. l is the tunnel vault hollow length, in m, d is the tunnel vault hollow width, in m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2 , a is the impact range of the tunnel vault void area, in m.

2. The method for calculating the vertical surrounding rock pressure of tunnel vault support and surrounding rock de-entrapment according to claim 1 is characterized by: The derivation process of formula (4) and formula (5) includes the following steps: Step S1, establishing three-dimensional stratum-structure models in two cases where there is a void area and there is no void area on the back vault of the tunnel support, and obtaining the three-dimensional mechanical response law of the lining structure through finite element calculation and analysis; Step S2, comparing and analyzing the three-dimensional mechanical response laws of the back arch of the tunnel support under two conditions: the presence of a void area and the absence of a void area; Step S3: According to the comparative analysis results of step S2, the load in the empty area is in the shape of a cuboid, and the corresponding load expression is: V c =l·d·q (6) Among them, V c is the load value of the tunnel vault void area, in kN, l is the tunnel vault void length, in m, d is the tunnel vault void width, in m, q is the standard value of the tunnel vault vertical pressure, in kN / m 2 , According to the stress concentration effect, the stress concentration load distribution around the void area is pyramid-shaped, and the corresponding load expression is: h q =k·a=q max -q (8) Among them, V n is the sum of the stress concentration loads within the influence range around the tunnel vault void area, in kN, and S is the load bottom area, in m 2 ,h q is the load height, in kN / m 2 , l is the length of the tunnel vault void, in m, d is the width of the tunnel vault void, in m, a is the influence range of the tunnel vault void area, in m, k is the slope of the vertical pressure increase section in the longitudinal cross section at the center of the tunnel vault void area, in kN / m, q is the standard value of the tunnel vault vertical pressure, in kN / m 2 ,q max The maximum vertical pressure in the longitudinal cross section at the center of the tunnel vault void area, in kN / m 2 ; Step S4, according to the equivalent load theory, the distributed stress corresponding to the hollow area is transferred to the surrounding of the hollow area, and it can be obtained that: V c =V n (9) Right now, From this we can get, Step S5, according to formula (12), the calculation formula of the change slope k′ of the maximum vertical pressure in the tunnel vault void area along the tunnel axis direction is: Step S6, taking the center point of the tunnel vault hollow area as the origin of the coordinate axis, establish a one-dimensional coordinate along the tunnel axis direction, and the coordinate value of each point on the coordinate axis is represented by X. When X=0, q X Get the maximum value q max , when -0.5l<X<0.5l and X≠0, q X As k′ decreases toward both sides, the maximum vertical surrounding rock pressure q in the arch void area along the tunnel axis direction X The calculation formula is, When 0.5l<|X|<0.5l+a, q X As k decreases toward both sides, the maximum vertical surrounding rock pressure q outside the arch void area along the tunnel axis direction X The calculation formula is, Where, l is the length of the tunnel vault void, in m, d is the width of the tunnel vault void, in m, a is the influence range of the tunnel vault void area, in m, k is the slope of the vertical pressure increase section in the longitudinal cross section at the center of the tunnel vault void area, in kN / m, and q is the standard value of the tunnel vault vertical pressure, in kN / m 2 ,q max The maximum vertical pressure in the longitudinal cross section at the center of the tunnel vault void area, in kN / m 2 .

3. The method for calculating vertical surrounding rock pressure of tunnel vault support and surrounding rock de-entrapment according to claim 1, characterized in that: The influence range a of the tunnel vault hollowing area is equal to the width of the tunnel vault hollowing area.

Images