A method for identifying and controlling the field state of surrounding rock in tunnel construction

Abstract

The application discloses a tunnel construction surrounding rock field state identification method and control method, and specifically relates to the following steps: step S1, establishing the relationship between the tunnel surrounding rock radius r and the surrounding rock deformation Δu r ; step S2, the allowable surrounding rock deformation under the strength criterion: the safety factor of the reserved surrounding rock, then the allowable actual surrounding rock deformation Δu r satisfies the following: KΔu r < Δu r‑max ; the method establishes the deformation control standard of the surrounding rock after the tunnel excavation, proposes the calculation method of the evolution of the surrounding rock stress with the deformation under different support parameters and support time, and gives the control method.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering technology, specifically relating to a method for identifying and controlling the surrounding rock field conditions during tunnel construction. Background Technology

[0002] Currently, the theory of drill-and-blast tunnel construction is mainly based on the New Austrian Tunneling Method (NATM). Its core idea is that after tunnel excavation, under the premise of fully considering the bearing capacity of the surrounding rock itself, a reasonable support timing should be selected so that the bearing capacity of both the surrounding rock and the support structure can be fully utilized. However, in actual construction, there are many problems: (1) The NATM only focuses on the deformation of the tunnel profile and does not pay enough attention to the potential damage to the rock; (2) The traditional surrounding rock characteristic curve can only reflect the concept of the NATM. In actual construction, it is difficult to determine the reasonable support timing and support parameters; (3) The traditional surrounding rock characteristic curve can only reflect the support requirements and ignores the possible changes in the stress state of the surrounding rock after the support is implemented. Therefore, in order to select the best support parameters and support timing in tunnel design and construction, and to ensure the safety of the surrounding rock and structure during the entire deformation process from the excavation of the surrounding rock to the final equilibrium, it is necessary to establish a deformation control criterion that considers the failure of rock strength, and on this basis, to form a calculation method for the evolution of surrounding rock stress that considers the influence of support parameters and support timing. Summary of the Invention

[0003] The purpose of this invention is to provide a method for identifying and controlling the surrounding rock field conditions during tunnel construction, establish a standard for controlling the deformation of the surrounding rock after tunnel excavation, and propose a calculation method for the evolution of surrounding rock stress with deformation under different support parameters and support timing.

[0004] This invention adopts the following technical solution: a method for identifying the surrounding rock state during tunnel construction, the method being as follows:

[0005] Step S1: Establish the maximum diameter r of the surrounding rock and the deformation Δu of the surrounding rock in the tunnel. r Relationship:

[0006]

[0007] Establish the radial stress σ of the surrounding rock of the tunnel respectively r and tangential stress σ θ With the deformation of the surrounding rock Δu r Relationship:

[0008]

[0009] Where: a is the tunnel radius, σ0 is the initial in-situ stress, and c is the rock cohesion. Let G be the internal friction angle of the rock, and G be the shear modulus.

[0010] At the location on the tunnel outline, r = a, therefore Δur Represents Δu a ;

[0011] Step S2, Allowable deformation of surrounding rock under strength criteria:

[0012] The critical condition for rock failure is used as the strength criterion:

[0013]

[0014] Where: tangential stress σ θ The maximum principal stress σ1 and the radial stress σ r The minimum principal stress is σ3;

[0015] The deformation of the surrounding rock under the stress criterion is:

[0016]

[0017] If a safety factor is reserved for the surrounding rock, then the allowable actual deformation of the surrounding rock is Δu. r The following conditions must be met:

[0018] KΔu r <Δu r-max ;

[0019] Where: K is the safety factor.

[0020] This invention also discloses a method for controlling the surrounding rock state during tunnel construction. Using the aforementioned method for identifying the surrounding rock state during tunnel construction, the method further includes the following after step S2:

[0021] Step S31: Determine the stress state during the deformation process of the surrounding rock:

[0022] Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is:

[0023]

[0024] Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock;

[0025] Step S32: After constructing the steel arch frame and shotcrete support, the stress generated in the surrounding rock is:

[0026]

[0027] The support resistance p1 provided by the arch frame + shotcrete support is:

[0028] p1=K1(Δu a -Δua0 );

[0029]

[0030] Where: K1 is the radial compressive stiffness of the arch frame + shotcrete support structure, E1 and v1 are the elastic modulus and Poisson's ratio of the arch frame + shotcrete support structure, respectively, and b and m are the outer and inner radii of the ring of the support structure of the circular tunnel.

[0031] When p1 = σ r11 At any given time, the surrounding rock of the cave experiences radial stress from deeper rock layers. This radial stress increases with increasing deformation, and the stress is:

[0032]

[0033]

[0034] And in p1 = σ r12 When the surrounding rock reaches its final equilibrium state, deformation ceases, and the final deformation Δu of the surrounding rock is obtained. a ;

[0035] The final deformation amount Δu a Substituting into the formula KΔu in step S2 r <Δu r-max If Δu a If the formula is met, then the constructed steel arch frame + shotcrete support meets the safety requirements. If the formula is not met, then the specifications of the steel arch frame + shotcrete are increased until it is found that the constructed steel arch frame + shotcrete support meets the safety requirements.

[0036] This invention also discloses a method for controlling the surrounding rock state during tunnel construction. Using the aforementioned method for identifying the surrounding rock state during tunnel construction, the method further includes the following after step S2:

[0037] Step S41: Determine the stress state during the deformation process of the surrounding rock:

[0038] Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is:

[0039]

[0040] Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock;

[0041] Step S42: After the installation of the system anchor bolt support, the stress generated in the surrounding rock is:

[0042]

[0043] The support force p2 provided by the system anchor bolts is:

[0044]

[0045] Where: E2 is the elastic modulus of the anchor bolt, L1 is the length of the anchor bolt, and S... l2 S represents the vertical spacing. c2 ΔL1 represents the circumferential spacing and the anchor bolt elongation.

[0046] The final deformation of the surrounding rock at the anchor head location under unsupported conditions is:

[0047]

[0048] but

[0049] The elongation of the anchor bolt is:

[0050] Where: Δu a α1 represents the final deformation of the surrounding rock at different locations under unsupported conditions; α1 is the correction factor.

[0051] When p2 = σ r21 At this time, the surrounding rock of the cave needs to withstand radial stress from the deeper rock. The radial stress increases with the increase of deformation, and the stress is:

[0052]

[0053] And at p2 = σ r22 When the surrounding rock reaches its final equilibrium state, deformation ceases, and the final deformation Δu of the surrounding rock is obtained. a ;

[0054] The final deformation amount Δu a Substitute into the formula KΔu in step S2. r <Δu r-max If Δu a If the formula is satisfied, the surrounding rock will meet the safety requirements after the anchor bolts are installed. If the formula is not satisfied, the specifications of the anchor bolts will be increased until the surrounding rock meets the safety requirements after the anchor bolts are installed.

[0055] This invention also discloses a method for controlling the surrounding rock state during tunnel construction. Using the aforementioned method for identifying the surrounding rock state during tunnel construction, the method further includes the following after step S2:

[0056] Step S51: Determine the stress state during the deformation process of the surrounding rock:

[0057] Δu is generated in the surrounding rock before support.r0 If the displacement is such that the stress generated in the surrounding rock is:

[0058]

[0059] Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock;

[0060] Step S52: After the prestressed anchor cable support is installed, the stress generated in the surrounding rock is:

[0061]

[0062] The support force p3 provided by the prestressed anchor cable support is:

[0063]

[0064] Where: E3 is the elastic modulus of the prestressed anchor cable, L2 is the length of the prestressed anchor cable, and ΔL2 is the elongation of the prestressed anchor cable;

[0065] The final deformation of the surrounding rock at the anchor head location under unsupported conditions is:

[0066]

[0067] It can be known and Δu a The following relationship exists:

[0068]

[0069] After the prestressed anchor cables are installed, as the surrounding rock deforms Δu... a As the value increases, the elongation of the prestressed anchor cable is:

[0070]

[0071] The support effect of the system anchor bolts slows down the deformation rate of the surrounding rock when p3 = σ r31 At this time, the surrounding rock of the cave needs to withstand radial stress from the deeper rock, and the radial stress increases with the increase of deformation. The stress is:

[0072]

[0073] Where: α2 is the correction coefficient;

[0074] When p3 = σ r32 At this point, the surrounding rock reaches its final equilibrium state, and deformation ceases; at this time, Δu a This is the final deformation of the surrounding rock;

[0075] The final deformation amount Δu a Substituting into the formula KΔu in step S2 r <Δu r-max If Δu a If the formula is satisfied, then the surrounding rock meets the safety requirements after the prestressed anchor cable support is implemented. If the formula is not satisfied, the specifications of the prestressed anchor cable support are increased until it is found that the surrounding rock meets the safety requirements after the prestressed anchor cable support is implemented.

[0076] This invention also discloses a method for controlling the surrounding rock state during tunnel construction. Using the aforementioned method for identifying the surrounding rock state during tunnel construction, the method further includes the following after step S2:

[0077] Step S61: Determine the stress state during the deformation process of the surrounding rock:

[0078] Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is:

[0079]

[0080] Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock;

[0081] Step S62: When multiple support methods are used together, the stress in the surrounding rock at the final stage is:

[0082]

[0083] When p1+p2+p3=σ r42 When the surrounding rock reaches its final equilibrium state, deformation ceases, and the final deformation Δu of the surrounding rock is obtained. a ;

[0084] The final deformation amount Δu a Substituting into the formula KΔu in step S2 r <Δu r-max If Δu a If the formula is satisfied, then the surrounding rock meets the safety requirements after implementing multiple support methods. If the formula is not satisfied, then the specifications of multiple support methods are increased until it is found that the surrounding rock meets the safety requirements after implementing multiple support methods.

[0085] The beneficial effects of this invention are: it takes into account the strength failure of rock during the stress evolution process of surrounding rock after excavation and deformation, proposes a quantitative calculation method for surrounding rock stress considering support parameters and support timing, as well as a method for judging the final equilibrium state, and can quantitatively analyze the influence of support parameters such as steel arch frames, shotcrete, anchor bolts, and anchor cables on surrounding rock stress, thereby obtaining the optimal support parameters and support timing, and forming a systematic design and construction method. Detailed Implementation

[0086] The present invention will now be described in detail through specific embodiments.

[0087] According to the stress field calculation formula for the surrounding rock of a circular tunnel after excavation, where the vertical and horizontal ground stresses are equal in tunnel mechanics, the extreme diameter 'a' at the boundary between the elastic and plastic zones... p , which is:

[0088]

[0089] The radial and tangential stresses at different locations, with a radius of r, are:

[0090]

[0091] The deformation of the surrounding rock is:

[0092]

[0093] The deformation of the surrounding rock at the cave wall location is:

[0094]

[0095] Where: a is the tunnel radius, σ0 is the initial in-situ stress, and c is the rock cohesion. Let be the internal friction angle of the rock, ρ be the support reaction force, and G be the shear modulus, which can be calculated using the elastic modulus E and Poisson's ratio μ.

[0096] G = E / 3(1-2μ) (6);

[0097] This invention discloses a method for identifying the surrounding rock conditions during tunnel construction. The method includes the following:

[0098] Step S1: Establish the relationship between the extreme diameter r of the tunnel surrounding rock and the deformation Δu_r of the surrounding rock:

[0099] After the excavation of the surrounding rock of the circular tunnel, based on equation (4), the extreme diameter r and deformation Δu of the surrounding rock of the tunnel are established respectively. r Relationship:

[0100]

[0101] Establish the radial and tangential stresses of the tunnel surrounding rock in relation to the variable surrounding rock shape Δu. r Relationship:

[0102]

[0103] At the location on the tunnel outline, r = a, therefore Δu r Represented as Δu a .

[0104] Step S2, Allowable deformation of surrounding rock under strength criteria:

[0105] The critical condition for rock failure is used as the strength criterion:

[0106]

[0107] Where: tangential stress σ θ The maximum principal stress σ1 and the radial stress σ r The minimum principal stress is σ3;

[0108] The deformation of the surrounding rock under the stress criterion is:

[0109]

[0110] If a safety factor is reserved for the surrounding rock, then the allowable deformation of the surrounding rock is:

[0111] KΔu r <Δu r-max ;

[0112] Where: K is the safety factor, K = 2.

[0113] The present invention also discloses a method for controlling the surrounding rock field conditions during tunnel construction, which further includes the following after step S2:

[0114] Step S31: Determine the stress state during the deformation process of the surrounding rock:

[0115] Δu is generated in the surrounding rock before support. r0 The displacement has resulted in the following stress:

[0116]

[0117] Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock;

[0118] Step S32: After constructing the steel arch frame and shotcrete support, the resulting stress is:

[0119]

[0120] The support resistance p1 provided by the arch frame + shotcrete support is:

[0121] p1=K1(Δu a -Δu a0 ) (twenty three);

[0122]

[0123] Where: K1 is the radial compressive stiffness of the arch frame + shotcrete support structure, E1 and v1 are the elastic modulus and Poisson's ratio of the arch frame + shotcrete support structure, respectively, and b and m are the outer and inner radii of the ring, respectively.

[0124] When p1 = σ r11 At any given time, the surrounding rock of the cave experiences radial stress from deeper rock layers. This radial stress increases with increasing deformation, and the stress is:

[0125]

[0126] And in p1 = σ r12 When the surrounding rock reaches its final equilibrium state, deformation ceases, and the final deformation Δu of the surrounding rock is obtained. a ;

[0127] The final deformation amount Δu a Substituting into the formula KΔu in step S2 r <Δu r-max If Δu a If the formula is met, then the constructed steel arch frame + shotcrete support meets the safety requirements. If the formula is not met, then the specifications of the steel arch frame + shotcrete are increased until it is found that the constructed steel arch frame + shotcrete support meets the safety requirements.

[0128] While the surrounding rock undergoes the same amount of deformation, the radial stress σ r Reduce and tangential stress σ θ The magnitude of the increase has increased. This is because the arch frame and the surrounding rock are in contact, and during deformation, a radial support reaction force is generated to resist the deformation of the surrounding rock. When the arch frame deforms to a certain extent, the generated reaction force is sufficient to prevent the surrounding rock from deforming further. However, the surrounding rock at deeper levels will continue to deform along the tunnel direction, at which point the radial stress acting on the surrounding rock will begin to increase. After the surrounding rock fails, collapses and rockfalls will occur. The support structure can prevent rock collapse, but as the deformation increases, more rocks collapse, thus the stress acting on the support structure gradually increases. Throughout the entire process after the support is installed, the radial support reaction force provided by the arch frame to the surrounding rock gradually increases with the increase in deformation. After reaching an equilibrium state, the deformation stops. Otherwise, both the surrounding rock and the structure will fail, and deformation control will fail.

[0129] In one embodiment of a construction method for tunnel field variation control, the method further includes the following after step S2:

[0130] Step S41: Determine the stress state during the deformation process of the surrounding rock:

[0131] Δu had already been generated before the support was installed. r0 The displacement is then expressed by equations (13) and (14).

[0132] After the system anchor bolt support is installed, the stress is:

[0133]

[0134] Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock;

[0135] Step S42: After the installation of the system anchor bolt support, the stress generated in the surrounding rock is:

[0136]

[0137] The support force p2 provided by the system anchor bolts is:

[0138]

[0139] Where: E2 is the elastic modulus of the anchor bolt, L1 is the length of the anchor bolt, and S... l2 S represents the vertical spacing. c2 ΔL1 represents the circumferential spacing and the anchor bolt elongation.

[0140] The final deformation of the surrounding rock at the anchor head location under unsupported conditions is:

[0141]

[0142] but

[0143] The elongation of the anchor bolt is:

[0144]

[0145] Where: Δu a α1 represents the final deformation of the surrounding rock at different locations under unsupported conditions; α1 is a correction coefficient obtained through field measurements.

[0146] When p2 = σ r21 At this time, the surrounding rock of the cave needs to withstand radial stress from the deeper rock. The radial stress increases with the increase of deformation, and the stress is:

[0147]

[0148] And at p2 = σ r22 When the surrounding rock reaches its final equilibrium state, deformation ceases, and the final deformation Δu of the surrounding rock is obtained. a .

[0149] The final deformation amount Δu a Substitute into the formula KΔu in step S2. r <Δu r-max If Δu a If the formula is satisfied, the surrounding rock will meet the safety requirements after the anchor bolts are installed. If the formula is not satisfied, the specifications of the anchor bolts will be increased until the surrounding rock meets the safety requirements after the anchor bolts are installed.

[0150] In one embodiment of a construction method for tunnel field variation control, the method further includes the following after step S2:

[0151] Step S51: Determine the stress state during the deformation process of the surrounding rock:

[0152] Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is:

[0153]

[0154] Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock;

[0155] Step S52: After the prestressed anchor cable support is installed, the stress generated in the surrounding rock is:

[0156] Unlike passive support, the surrounding rock stress changes immediately after the application of prestressed anchor cable support. Let the diameter of the anchor cable be d2, the prestress be F, and the longitudinal spacing be S. l2 The circumferential spacing is S c2 Then the stress in the surrounding rock is:

[0157]

[0158] The support force p3 provided by the prestressed anchor cable support is:

[0159]

[0160] In the formula: E3 is the elastic modulus of the prestressed anchor cable, L2 is the length of the prestressed anchor cable, and ΔL2 is the elongation of the prestressed anchor cable.

[0161] Equation (4) can be used to calculate the final deformation of the surrounding rock at different locations under unsupported conditions, and Equation (5) can be used to calculate the final deformation of the surrounding rock at the tunnel wall location under unsupported conditions.

[0162] If the length of the prestressed anchor cable is L_2, then the final deformation of the surrounding rock at the anchor head location under unsupported conditions is:

[0163]

[0164] It can be known and Δu a The following relationship exists:

[0165]

[0166] After the prestressed anchor cables are installed, as the surrounding rock deforms Δu... a As the value increases, the elongation of the prestressed anchor cable is:

[0167]

[0168] The support effect of the system anchor bolts slows down the deformation rate of the surrounding rock when p3 = σ r31 At this time, the surrounding rock of the cave needs to withstand radial stress from the deeper rock, and the radial stress increases with the increase of deformation. The stress is:

[0169] Where α2 is the correction coefficient, which needs to be obtained through on-site measurement.

[0170] When p3 = σ r32 At this point, the surrounding rock reaches its final equilibrium state, and deformation ceases. The Δu at this point... a This is the final deformation of the surrounding rock.

[0171] The final deformation amount Δu a Substituting into the formula KΔu in step S2 r <Δu r-max If Δu a If the formula is satisfied, then the surrounding rock meets the safety requirements after the prestressed anchor cable support is implemented. If the formula is not satisfied, the specifications of the prestressed anchor cable support are increased until it is found that the surrounding rock meets the safety requirements after the prestressed anchor cable support is implemented.

[0172] Unlike arch frames and system anchors, which require deformation along with the surrounding rock to function, prestressed anchors function immediately after installation, instantly altering the stress state of the surrounding rock. Specifically, this manifests as radial stress σ r The linear increase and tangential stress σ θ The stress decreased linearly. Subsequently, the stress change curve showed a similar trend to that after the installation of the system anchor bolts.

[0173] Another method for tunnel field variation control construction is as follows:

[0174] The following is also included after step S2:

[0175] Step S61: Determine the stress state during the deformation process of the surrounding rock:

[0176] Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is:

[0177]

[0178] Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock;

[0179] Step S62: When multiple support methods are used together, the stress in the surrounding rock at the final stage is:

[0180] If multiple support methods are used in combination, the stress in the surrounding rock at the final stage will be:

[0181]

[0182]

[0183] When p1+p2+p3=σ r42 At this point, the surrounding rock reaches its final equilibrium state, and deformation ceases. The Δu at this point... a This is the final deformation of the surrounding rock. The final deformation Δu... a Substituting into the formula KΔu in the above steps r <Δu r-max The deformation control standard shown verifies the deformation at final stability to determine the effectiveness of the support method; if Δu a If the formula is satisfied, then the surrounding rock meets the safety requirements after implementing multiple support methods. If the formula is not satisfied, then the specifications of multiple support methods are increased until it is found that the surrounding rock meets the safety requirements after implementing multiple support methods.

Claims

1. A method for identifying the surrounding rock state during tunnel construction, characterized in that, The method is as follows: Step S1: Establish the maximum diameter r of the surrounding rock and the deformation Δu of the surrounding rock in the tunnel. r Relationship: Establish the radial stress σ of the surrounding rock of the tunnel respectively r and tangential stress σ θ With the deformation of the surrounding rock Δu r Relationship: Where: a is the tunnel radius, σ0 is the initial in-situ stress, and c is the rock cohesion. Let G be the internal friction angle of the rock, and G be the shear modulus. At the location on the tunnel outline, r = a, therefore Δu r Represents Δu a ,Δu a This represents the final deformation of the surrounding rock. Step S2, Allowable deformation of surrounding rock under strength criteria: The critical condition for rock failure is used as the strength criterion: Where: tangential stress σ θ The maximum principal stress σ1 and the radial stress σ r The minimum principal stress is σ3; The deformation of the surrounding rock under the stress criterion is: If a safety factor is reserved for the surrounding rock, then the allowable actual deformation of the surrounding rock is Δu. r The following conditions must be met: KΔu r <Δu r-max ; Where: K is the safety factor.

2. A method for controlling the surrounding rock state during tunnel construction, employing the method for identifying the surrounding rock state during tunnel construction as described in claim 1, characterized in that... The following is also included after step S2: Step S31: Determine the stress state during the deformation process of the surrounding rock: Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is: Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock; Step S32: After constructing the steel arch frame and shotcrete support, the stress generated in the surrounding rock is: The support resistance p1 provided by the arch frame + shotcrete support is: p1=K1(Δu a -Δu a0 ); Where: K1 is the radial compressive stiffness of the arch frame + shotcrete support structure, E1 and v1 are the elastic modulus and Poisson's ratio of the arch frame + shotcrete support structure, respectively, and b and m are the outer and inner radii of the ring of the support structure of the circular tunnel. When p1 = σ r11 At that time, the surrounding rock of the cave is subjected to radial stress from the deeper rock. The radial stress increases with the increase of deformation, and the stress is: And in p1 = σ r12 When the surrounding rock reaches its final equilibrium state, deformation ceases, and the final deformation Δu of the surrounding rock is obtained. a ; The final deformation amount Δu a Substituting into the formula KΔu in step S2 r <Δu r-max If Δu a If the formula is met, then the constructed steel arch frame + shotcrete support meets the safety requirements. If the formula is not met, then the specifications of the steel arch frame + shotcrete are increased until it is found that the constructed steel arch frame + shotcrete support meets the safety requirements.

3. A method for controlling the surrounding rock state during tunnel construction, employing the method for identifying the surrounding rock state during tunnel construction as described in claim 1, characterized in that... The following is also included after step S2: Step S41: Determine the stress state during the deformation process of the surrounding rock: Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is: Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock; Step S42: After the installation of the system anchor bolt support, the stress generated in the surrounding rock is: The support force p2 provided by the system anchor bolts is: Where: E2 is the elastic modulus of the anchor bolt, L1 is the length of the anchor bolt, and S... l1 S represents the vertical spacing. c1 The circumferential spacing is ΔL1, and the anchor bolt elongation is ΔL1. The final deformation of the surrounding rock at the anchor head location under unsupported conditions is: but The elongation of the anchor bolt is: Where: Δu a α1 represents the final deformation of the surrounding rock at different locations under unsupported conditions; α1 is the correction factor. When p2 = σ r21 At this time, the surrounding rock of the cave needs to withstand radial stress from the deeper rock. The radial stress increases with the increase of deformation, and the stress is: And at p2 = σ r22 When the surrounding rock reaches its final equilibrium state, deformation ceases, and the final deformation Δu of the surrounding rock is obtained. a ; The final deformation amount Δu a Substitute into the formula KΔu in step S2. r <Δu r-max If Δu a If the formula is satisfied, the surrounding rock will meet the safety requirements after the anchor bolts are installed. If the formula is not satisfied, the specifications of the anchor bolts will be increased until the surrounding rock meets the safety requirements after the anchor bolts are installed.

4. A method for controlling the surrounding rock state during tunnel construction, employing the method for identifying the surrounding rock state during tunnel construction as described in claim 1, characterized in that... The following is also included after step S2: Step S51: Determine the stress state during the deformation process of the surrounding rock: Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is: Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock; Step S52: After the prestressed anchor cable support is installed, the stress generated in the surrounding rock is: The support force p3 provided by the prestressed anchor cable support is: Where: E3 is the elastic modulus of the prestressed anchor cable, L2 is the length of the prestressed anchor cable, and ΔL2 is the elongation of the prestressed anchor cable; The final deformation of the surrounding rock at the anchor head location under unsupported conditions is: It can be known and Δu a The following relationship exists: After the prestressed anchor cables are installed, as the surrounding rock deforms Δu... a As the value increases, the elongation of the prestressed anchor cable is: The support effect of the system anchor bolts slows down the deformation rate of the surrounding rock when p3 = σ r31 At this time, the surrounding rock of the cave needs to withstand radial stress from the deeper rock. The radial stress increases with the increase of deformation, and the stress is: Where: α2 is the correction coefficient; When p3 = σ r32 At this point, the surrounding rock reaches its final equilibrium state, and deformation ceases; at this time, Δu a This is the final deformation of the surrounding rock; The final deformation amount Δu a Substituting into the formula KΔu in step S2 r <Δu r-max If Δu a If the formula is satisfied, then the surrounding rock meets the safety requirements after the prestressed anchor cable support is applied. If the formula is not satisfied, then the specifications of the prestressed anchor cable support are increased until it is found that the surrounding rock meets the safety requirements after the prestressed anchor cable support is applied.

5. A method for controlling the surrounding rock state during tunnel construction, employing the method for identifying the surrounding rock state during tunnel construction as described in claim 1, characterized in that... The following is also included after step S2: Step S61: Determine the stress state during the deformation process of the surrounding rock: Δu is generated in the surrounding rock before support. r0 If the displacement is such that the stress generated in the surrounding rock is: Where: σ r0 and σ θ0 These are the radial and tangential stresses of the surrounding rock after the stress changes due to the initial displacement of the surrounding rock; Step S62: When multiple support methods are used together, the stress in the surrounding rock at the final stage is: When p1+p2+p3=σ r42 When the surrounding rock reaches its final equilibrium state, deformation ceases, and the final deformation Δu of the surrounding rock is obtained. a ; p1 represents the support resistance provided by the arch frame + shotcrete support; p2 represents the support force provided by the system anchor bolts; p3 represents the support force provided by the prestressed anchor cable support. The final deformation amount Δu a Substituting into the formula KΔu in step S2 r <Δu r-max If Δu a If the formula is satisfied, then the surrounding rock meets the safety requirements after implementing multiple support methods. If the formula is not satisfied, then the specifications of multiple support methods are increased until it is found that the surrounding rock meets the safety requirements after implementing multiple support methods.

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