Tunnel prestressed anchoring layer design method considering advanced support effect

Abstract

The invention discloses a tunnel prestressed anchoring layer design method considering an advanced support effect, which comprises the following steps of: firstly, constructing a prestressed anchoring layer load-structure calculation model, and secondly, deducing a compressive strength calculation method of a prestressed anchoring layer in a limit equilibrium state by adopting a Mohr-Coulomb strength theory; a surrounding rock loosening pressure correction calculation method considering an advance support load reduction mechanism is provided, a prestressed anchoring layer support design method of the tunnel based on the surrounding rock loosening pressure is finally formed, and a calculation basis is provided for accurate design of tunnel anchoring and shotcreting support; according to the technical scheme, the method comprises the following steps that S1, a prestress anchoring layer load-structure calculation model is constructed; s2, deducing a compressive strength calculation method of the prestressed anchoring layer in a limit equilibrium state; s3, proposing a surrounding rock loosening pressure correction calculation method considering an advance support load reduction mechanism; and S4, on the basis of a correction load calculation method, the load-structure model is adopted, and the design parameters of the prestressed anchoring layer are calculated.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and in particular relates to a tunnel prestressed anchoring layer design method taking into account the effect of advance support. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In the existing research, there has been preliminary research on the design method of prestressed anchor layer support. For example, CN110210069B discloses a tunnel advance support system design method and a tunnel advance support design method, which aims to improve the stability of the heading face and realize mechanized full-section construction of the tunnel under soft surrounding rock conditions. However, the influence of the prestressed anchor layer is not considered in the calculation model during the design of the tunnel advance support system.

[0004] In the existing anchor layer support design method, the influence of prestress on the mechanical properties of the anchor layer is ignored, and the load borne by the anchor layer is not combined with the loosening pressure in the existing "Railway Tunnel Design Code" (TB 10003-2016). This loosening pressure calculation method combines the advantages of the full soil column theory, Xie Jiawei formula and the empirical formula based on sample statistics and surrounding rock classification, but does not consider the influence of advance support on the load borne by the anchor layer. Summary of the invention

[0005] In view of the above problems, the present invention provides a tunnel prestressed anchor layer design method considering the effect of advance support. First, a prestressed anchor layer load-structure calculation model is constructed. Secondly, the Mohr-Cou l omb strength theory is adopted to derive the calculation method of the compressive strength of the prestressed anchor layer under the limit equilibrium state. A correction calculation method for the surrounding rock loosening pressure considering the advance support load reduction mechanism is proposed. Finally, a tunnel prestressed anchor layer support design method based on the surrounding rock loosening pressure is formed, which provides a calculation basis for the precise design of tunnel anchor spraying support.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] The present invention provides a tunnel prestressed anchor layer design method considering the effect of advance support. The anchor rods in the advance support are inserted into the rock layer, and the ends of the anchor rods are grouting to form a prestressed anchor layer. The design method includes the following steps:

[0008] S1. Construct the load-structure calculation model of the prestressed anchor layer;

[0009] S2. Using Mohr-Cou l omb strength theory, derive a method for calculating the compressive strength of the prestressed anchor layer under the limit equilibrium state;

[0010] S3. Propose a calculation method for the correction of the surrounding rock loosening pressure taking into account the load reduction mechanism of the advanced support;

[0011] S4. Based on the surrounding rock loosening pressure correction calculation method, the load-structure calculation model is used to calculate the design parameters of the prestressed anchoring layer.

[0012] Furthermore, in the process of establishing the load-structure calculation model of the prestressed anchor layer in S1, the prestressed anchor layer structure is simulated by beam units, the interaction between the prestressed anchor layer and the stratum is simulated by radial tension-free springs, and the wall foot is fixed by fixed end constraints.

[0013] Furthermore, in the process of constructing the load-structure calculation model of the prestressed anchor layer, the length of the prestressed anchor rod, the width of the pad and the annular spacing of the anchor rod need to be considered in the calculation of the thickness of the prestressed anchor layer; the calculation formula of the thickness of the prestressed anchor layer is as follows:

[0014]

[0015] Where L is the thickness of the prestressed anchor layer; R is the tunnel radius; S Tb L is the circumferential spacing of anchor rods; fb is the free section length of the prestressed anchor rod; b is the width of the anchor rod gasket; α is the pressure diffusion angle.

[0016] Furthermore, the equivalent elastic modulus of the surrounding rock after bolt reinforcement is affected by the elastic modulus of the bolt and the surrounding rock. According to the area equivalence principle, the expression of the equivalent elastic modulus E* is obtained as follows:

[0017]

[0018] Among them, E b is the elastic modulus of the anchor rod; E is the elastic modulus of the surrounding rock; S Lb is the axial spacing of the anchor rods; d is the diameter of the anchor rods.

[0019] Furthermore, the equivalent cohesion of surrounding rock c * and the equivalent internal friction angle The expression is:

[0020]

[0021] Among them, λ is the friction coefficient between the anchor and the surrounding rock; in the threaded steel anchor support system, c is the original cohesion of surrounding rock; is the internal friction angle.

[0022] Furthermore, the safety factor calculation formula is as follows:

[0023] k b N b ≤μασ b B L

[0024] Among them, k b is the safety factor of the prestressed anchor layer; N b is the axial force of the cross section; μ is the longitudinal bending coefficient of the cross section; α is the eccentricity influence coefficient of the axial force; b is the calculated width of the bearing arch; L is the calculated height of the prestressed anchor layer; σ b is the ultimate compressive strength of the prestressed anchor layer.

[0025] Furthermore, according to the Mohr-Cou l omb strength theory in S2, the original compressive strength expression of the surrounding rock is:

[0026]

[0027] Among them, σ3 is the minimum principal stress after the surrounding rock stress is readjusted before the anchor bolt is applied after tunnel excavation.

[0028] Furthermore, the calculation formula for the compressive strength of the prestressed anchoring layer after the prestressed anchor rod is applied is:

[0029]

[0030] Where c* is the equivalent cohesion of surrounding rock; is the equivalent internal friction angle; F a The preload applied to the anchor rod.

[0031] Furthermore, if the tunnel adopts advanced pipe shed for pre-support, the surrounding rock pressure calculation formula should be corrected, and the corrected surrounding rock vertical uniform pressure calculation formula is:

[0032] q l =ξγh a

[0033] h a =0.45×2 s-1 ×

[0034] Among them, q l is the vertical uniform pressure of the surrounding rock; γ is the weight of the surrounding rock; h a is the height of surrounding rock; w is the width influence coefficient; B is the tunnel width; ξ is the surrounding rock pressure reduction coefficient.

[0035] Furthermore, the corrected calculation formula for the surrounding rock horizontal pressure is obtained as follows:

[0036] e=λq l

[0037] Where, e is the horizontal pressure; λ is the ratio of the lateral pressure to the vertical pressure.

[0038] Compared with the prior art, the present invention has the following advantages and positive effects:

[0039] The present invention constructs a load-structure calculation model of the prestressed anchor layer, and then adopts the Mohr-Cou l omb strength theory to derive the calculation method of the compressive strength of the prestressed anchor layer under the limit equilibrium state, and proposes a correction calculation method for the loosening pressure of the surrounding rock considering the load reduction mechanism of the advance support, and finally forms a tunnel prestressed anchor layer design method considering the effect of the advance support, which provides a calculation basis for the precise design of the tunnel anchor spraying support. The problem that the influence of the prestress on the mechanical properties of the prestressed anchor layer is not considered in the existing prestressed anchor layer design method is solved, and a more reliable loosening pressure of the surrounding rock is used as the calculation load for calculation, which overcomes the defect that the prestress is not involved in the design of the tunnel engineering support structure, and enriches the relevant theory of the refined design of the tunnel engineering support structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0041] Figure 1 This is a flow chart of the tunnel prestressed anchor layer design method of the present invention;

[0042] Figure 2 This is a load-structure calculation model diagram of the prestressed anchoring layer of the present invention;

[0043] Figure 3 This is an analysis diagram of the reinforcement effect of the prestressed anchor rod of the present invention;

[0044] Figure 4 It is a graph showing the change in the compressive strength improvement ratio of the prestressed anchoring layer under different anchor rod spacings of the present invention;

[0045] Figure 5 This is a graph showing the change in the compressive strength improvement ratio of the prestressed anchoring layer under different anchor rod parameters of the present invention. DETAILED DESCRIPTION

[0046] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0047] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0048] This embodiment discloses a conveyor belt device that is easy to maintain, such as Figure 1-Figure 2 As shown in the figure, the design method of tunnel prestressed anchor layer considering the effect of advance support mainly includes four steps:

[0049] S1. Construct a load-structure calculation model for the prestressed anchor layer; according to the bearing characteristics of the prestressed anchor layer, a corresponding structural calculation model is proposed, namely, the load-structure calculation model for the prestressed anchor layer. After the prestressed anchor rods are installed, a support structure layer with certain bearing performance can be actively formed around the tunnel, avoiding the possibility of collapse within a certain range around the tunnel due to the loosening of the surrounding rock after tunnel excavation. For this purpose, a load-structure calculation model for the prestressed anchor layer is established, such as Figure 2 As shown. The prestressed anchor layer structure is simulated by beam elements, the interaction between the prestressed anchor layer and the stratum is simulated by radial tension-free springs, and the foot of the wall is fixed by fixed end constraints; among them, the initial sprayed concrete is not reflected in the load-structure model of the prestressed anchor layer. There are two reasons: first, the thickness of the initial sprayed concrete is smaller than that of the prestressed anchor layer, and for safety reasons, its contribution to the thickness of the prestressed anchor layer can be ignored in the calculation; second, it is believed that after the prestressed anchor rod is supported, a complete prestressed anchor layer structure can be formed under the action of the initial sprayed concrete surface protection, that is, the effect of the initial sprayed concrete on the structural performance of the prestressed anchor layer has been taken into account by default.

[0050] The thickness calculation process of the prestressed anchor layer needs to consider the length of the prestressed anchor rod, the width of the pad and the annular spacing of the anchor rod; the thickness calculation formula of the prestressed anchor layer is as follows:

[0051]

[0052] Where, L is the thickness of the prestressed anchor layer, m; R is the tunnel radius, m; S Tb is the circumferential spacing of anchor rods, m; L fb is the free section length of the prestressed anchor, m; b is the width of the anchor gasket, m; α is the pressure diffusion angle (usually θ=45° for calculation).

[0053] The equivalent elastic modulus of the surrounding rock after anchor reinforcement is affected by the elastic modulus of the anchor and the elastic modulus of the surrounding rock. According to the area equivalence principle, the equivalent elastic modulus E is obtained. *The expression is:

[0054]

[0055] In the formula, E b is the elastic modulus of the anchor (MPa); E is the elastic modulus of the surrounding rock (MPa); S Lb is the axial spacing of anchor rods (m); d is the diameter of anchor rods, m.

[0056] The calculation formula for the compressive strength of the prestressed anchor layer in the model is:

[0057]

[0058] In the formula, c * , is the equivalent cohesion of surrounding rock (MPa) and equivalent internal friction angle (°); F a is the preload applied to the anchor (kN).

[0059] Equivalent cohesion of surrounding rock under anchor support c * and the equivalent internal friction angle The expression is:

[0060]

[0061] Where λ is the friction coefficient between the anchor and the surrounding rock. c. is the original cohesion (MPa) and internal friction angle (°) of the surrounding rock.

[0062] The radial spring stiffness parameters between the prestressed anchor layer and the surrounding rock can be selected according to the elastic reaction coefficient specified in the "Railway Tunnel Design Code" (TB10003-2016).

[0063] Safety evaluation method: The safety factor of the prestressed anchor layer can be calculated according to the damage stage method in the current "Railway Tunnel Design Code" (TB10003-2016). Since the thickness of the prestressed anchor layer is generally large and its stress state is generally small eccentricity, the following formula can be used for calculation according to the code.

[0064] k b N b ≤μασ b B L

[0065] Among them, k b N is the safety factor of the prestressed anchor layer, which can be evaluated according to the safety factor determination criteria for plain concrete structure strength in the Railway Tunnel Design Code (TB10003-2016); bis the axial force of the cross section, N; μ is the longitudinal bending coefficient of the cross section; α is the axial force eccentricity influence coefficient; b is the calculated width of the bearing arch; L is the calculated height of the prestressed anchor layer, m; σ b is the ultimate compressive strength of the prestressed anchor layer, MPa, and is calculated according to the calculation formula for the compressive strength of the prestressed anchor layer in the model.

[0066] S2. Mohr-Cou l omb strength theory is used to derive a calculation method for the compressive strength of the prestressed anchor layer under the limit equilibrium state. Since the compressive strength of the prestressed anchor layer has a great influence on the structural support performance and stability of the prestressed anchor layer in the load-structure calculation model of the prestressed anchor layer, the present invention analyzes the calculation method for the compressive strength of the prestressed anchor layer of the tunnel.

[0067] After the prestressed anchor rods support the surrounding rock, on the one hand, the anchor rods and the surrounding rock in the anchoring area form a prestressed anchoring layer, and on the other hand, the pre-tightening force of the anchor rods causes the surrounding rock in the anchoring area to be subjected to confining pressure. Figure 3 As shown in the figure, no matter what kind of effect, the mechanical properties of the surrounding rock in the anchoring area are improved.

[0068] Therefore, according to the Mohr-Coulomb strength theory, the original compressive strength expression of the surrounding rock is:

[0069]

[0070] Among them, σ3 is the minimum principal stress after the surrounding rock stress is readjusted before the anchor bolt is applied after tunnel excavation, MPa.

[0071] After the prestressed anchor bolt is installed, the original compressive strength of the surrounding rock is effectively improved, mainly in terms of providing confining pressure and forming an anchor-rock complex. Therefore, the calculation formula for the compressive strength of the prestressed anchoring layer after the prestressed anchor bolt is:

[0072]

[0073] It is worth noting that the original compressive strength of the surrounding rock mentioned in the present invention refers to the compressive strength value of the surrounding rock before the support after tunnel excavation. Since the state of the surrounding rock at this time is highly correlated with the surrounding rock's own properties, construction technology (blasting, etc.), the stability of the face, and the application of advanced pre-support, it is conservatively considered that the original rock mechanical parameters in the prestressed anchor layer are calculated based on their residual strength.

[0074] According to the calculation formula of the compressive strength of the prestressed anchor layer after the prestressed anchor is installed, the compressive strength of the prestressed anchor layer is related to the design parameters of the prestressed anchor, such as the anchor preload, anchor spacing, length and diameter. Therefore, 5 gradients are selected for each variable for analysis. The specific parameters are as follows:

[0075] The parameters of prestressed anchor rods are:

[0076] SLb: 0.8, 1.0, 1.2, 1.4, 1.6(m);

[0077] STb: 0.8, 1.0, 1.2, 1.4, 1.6(m);

[0078] Lfb: 3.5(m);

[0079] Fa: 30, 50, 70, 90, 110 (kN);

[0080] d: 0.022(m);

[0081] Surrounding rock parameter c: 0.05 (MPa);

[0082] φ: 20(°);

[0083] E: 1.0 (GPa);

[0084] v: 0.3;

[0085] Tunnel size R: 7.5 (m);

[0086] like Figure 3 As shown in the figure, it is a graph showing the change in the compressive strength improvement rate of the prestressed anchor layer under different anchor spacings. From the analysis of the reinforcement effect of prestressed anchors, it can be seen that the compressive strength of the prestressed anchor layer can be divided into three categories, namely, the compressive strength of the anchor-rock complex type σ b1 , confining pressure compressive strength σ b2 and anchor rock composite + confining pressure compressive strength σ b .

[0087] Depend on Figure 3 It can be seen that the three types of compressive strength improvement rates of the prestressed anchor layer all decrease with the increase of the anchor spacing, but the overall performance is σb>σb2>σb1. For example, when the anchor spacing is 0.8m, 1.0m, 1.2m, 1.4m, and 1.6m, σ b1 are 29%, 19%, 13%, 10%, and 7% respectively. b2 They are 101%, 65%, 46%, 34%, and 26% respectively. b They are 160%, 96%, 65%, 47% and 36% respectively. Among them, the compressive strength of the anchor rock composite σ b1 It can be roughly considered as the compressive strength of the prestressed anchor layer after traditional mortar anchor support. The calculation results show that its effect on improving the compressive strength of the original rock is small (7% to 29%). However, the prestressed anchor layer formed after the prestressed anchor support has a significant increase in the compressive strength of the prestressed anchor layer (36% to 160%) due to the effect of the confining pressure Δσ3, and σb Greater than σ b2 and σ b1 The stability of the prestressed anchor layer is significantly improved, which can play an effective and stable control role on the stability of the surrounding rock.

[0088] In addition, with the increase of the prestressed anchor rod preload, the compressive strength of the prestressed anchor layer gradually increases. For example, when the anchor rod preload is 30kN, 50kN, 70kN, 90kN, and 110kN, the compressive strength of the prestressed anchor layer increases by 44%, 65%, 86%, 106%, and 127%, respectively. Figure 4 In summary, when prestressed anchor rods are used to support tunnels, a high-strength prestressed anchor layer can be formed, thereby improving the stability of the tunnel surrounding rock.

[0089] S3. A correction calculation method for loosening pressure of surrounding rock considering the load reduction mechanism of advance support is proposed; a correction calculation method for loosening pressure of surrounding rock of tunnel is proposed; surrounding rock pressure is determined according to the collapse height of surrounding rock, so the determination of surrounding rock pressure in the load-structure calculation model of prestressed anchoring layer is approximately considered as the calculated value of surrounding rock pressure of deep buried tunnel. In addition, based on the existing analysis of the reinforcement mechanism of advance pipe shed, it can be known that the overburden load of surrounding rock can be reduced when the advance pipe shed is used for pre-support. Therefore, if the tunnel adopts the advance pipe shed for pre-support, the calculation formula of surrounding rock pressure should be corrected, that is, the corrected surrounding rock pressure calculation expression is obtained as follows:

[0090] q l =ξγh a

[0091] h a =0.45×2 s-1 ×

[0092] e=λq l

[0093] In the formula, q l is the vertical uniform pressure of the surrounding rock (kPa); e is the horizontal pressure (kPa); γ is the weight of the surrounding rock (kN / m 3 );h a is the height of the surrounding rock (m); λ is the ratio of the lateral pressure to the vertical pressure; w is the width influence coefficient, w=1+i(B-5), i is the rate of increase or decrease of the surrounding rock pressure when B increases or decreases by 1m, when B<5m, i=0.2, when B>5m, i=0.1; B is the tunnel width.

[0094] Among them, ξ is the surrounding rock pressure reduction coefficient, 0<ξ<1, and the existing advance support calculation method can be used for calculation, and the final reduction coefficient can be selected. When the advance pipe-roof is not used for pre-support, ξ=1.

[0095] S4. Based on the modified load calculation method, the load-structure model is used to calculate the relevant design parameters of the prestressed anchor layer.

[0096] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A design method for a tunnel prestressed anchor layer taking into account the effect of advance support, wherein the anchor rods in the advance support are inserted into the rock layer, and the ends of the anchor rods are grouting to form a prestressed anchor layer, characterized in that: The design methodology includes the following steps: S1. Construct the load-structure calculation model of the prestressed anchor layer; S2. Using Mohr-Coulomb strength theory, a method for calculating the compressive strength of the prestressed anchor layer under the limit equilibrium state is derived; S3. Propose a calculation method for the correction of the surrounding rock loosening pressure taking into account the load reduction mechanism of the advanced support; S4. Based on the surrounding rock loosening pressure correction calculation method, the load-structure calculation model is used to calculate the design parameters of the prestressed anchoring layer.

2. A method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 1, characterized in that: In the process of establishing the load-structure calculation model of the prestressed anchor layer in S1, the prestressed anchor layer structure is simulated by beam units, the interaction between the prestressed anchor layer and the stratum is simulated by radial tension-free springs, and the wall foot is fixed by fixed end constraints.

3. A method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 1, characterized in that: The thickness of the prestressed anchor layer needs to be calculated by considering the length of the prestressed anchor rod, the width of the pad and the annular spacing of the anchor rod; the thickness calculation formula of the prestressed anchor layer is as follows: Where L is the thickness of the prestressed anchor layer; R is the tunnel radius; S Tb L is the circumferential spacing of anchor rods; fb is the free section length of the prestressed anchor rod; b is the width of the anchor rod gasket; α is the pressure diffusion angle.

4. A method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 3, characterized in that: The equivalent elastic modulus of the surrounding rock after bolt reinforcement is affected by the elastic modulus of the bolt and the surrounding rock. According to the area equivalence principle, the expression of the equivalent elastic modulus E* is: Among them, E b is the elastic modulus of the anchor rod; E is the elastic modulus of the surrounding rock; S Lb is the axial spacing of the anchor rods; d is the diameter of the anchor rods.

5. A method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 4, characterized in that: Equivalent cohesion of surrounding rock c * and the equivalent internal friction angle The expression is: Among them, λ is the friction coefficient between the anchor and the surrounding rock; in the threaded steel anchor support system, c is the original cohesion of surrounding rock; is the internal friction angle.

6. A method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 5, characterized in that: The ultimate compressive strength safety factor calculation formula of the prestressed anchor layer is as follows: k b N b ≤μασ b bL Among them, k b is the safety factor of the prestressed anchor layer; N b is the axial force of the cross section; μ is the longitudinal bending coefficient of the cross section; α is the eccentricity influence coefficient of the axial force; b is the calculated width of the bearing arch; L is the calculated height of the prestressed anchor layer; σ b is the ultimate compressive strength of the prestressed anchor layer.

7. A method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 1, characterized in that: In S2, according to the Mohr-Coulomb strength theory, the original compressive strength of the surrounding rock is expressed as: Among them, σ3 is the minimum principal stress after the surrounding rock stress is readjusted before the anchor bolt is applied after tunnel excavation.

8. A method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 7, characterized in that: The calculation formula of the compressive strength of the prestressed anchoring layer after the prestressed anchor rod is applied is: Where c* is the equivalent cohesion of surrounding rock; is the equivalent internal friction angle; F a The preload applied to the anchor rod.

9. The method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 1, characterized in that: If the tunnel is pre-supported with an advanced pipe shed, the surrounding rock pressure calculation formula should be corrected, and the corrected surrounding rock vertical uniform pressure calculation formula is: q l =ξγh a h a =0.45×2 s-1 ×w Among them, q l is the vertical uniform pressure of the surrounding rock; γ is the weight of the surrounding rock; h a is used to calculate the surrounding rock height; w is the width influence coefficient, w=1+i(B-5), i is the rate of increase or decrease of surrounding rock pressure when B increases or decreases by 1m; B is the tunnel width; ξ is the surrounding rock pressure reduction coefficient.

10. A method for designing a tunnel prestressed anchoring layer taking into account the effect of advance support as claimed in claim 9, characterized in that: The corrected calculation formula for the surrounding rock horizontal pressure is: e=λq l Where, e is the horizontal pressure; λ is the ratio of the lateral pressure to the vertical pressure.

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