Method for loading tunnel face of wind-blown sand stratum tunnel

Abstract

The invention discloses a method for tunnel face load of an aeolian sand stratum tunnel, belongs to the field of tunnel engineering supporting structure design, and solves the problem that a theoretical model of an existing method cannot fully consider mechanical behavior characteristics of special stratums such as aeolian sand and the like, so that the precision of a calculation result is insufficient. The method comprises the steps of establishing a slip mass calculation model considering an included angle between a fracture surface and a horizontal plane based on a Taisha theory, performing calculation to obtain a lateral pressure coefficient, and performing simplification solution on a vertical stress balance equation to obtain a tunnel face load value; according to the tunnel face load calculation method, the tunnel face load calculation method is improved, the calculation formula of the tunnel face load value is obtained by simplifying and solving the vertical stress balance equation, the actual stress state of the aeolian sand stratum can be reflected more accurately, and therefore the precision of the calculation result is improved, and finally more accurate load value can be provided for tunnel supporting structure design; therefore, the safety and stability of the structure are enhanced, and the risk of structure failure caused by inaccurate load calculation is reduced.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering support structure design, specifically relating to a method for handling the face load of tunnels in aeolian sand formations. Background Technology

[0002] In tunnel construction, aeolian sand formations pose a significant challenge due to their unique engineering geological characteristics. These formations are typically composed of poorly graded, loosely structured sand grains with extremely low cohesion, resulting in low overall shear strength and poor self-stability. During tunnel excavation in such formations, the tunnel face is highly susceptible to instability due to construction disturbances, leading to surrounding rock deformation and even collapse. Particularly when sand leakage occurs during construction, the load on the tunnel face dynamically changes, causing a sharp increase in pressure on the support structure and a rapid expansion of deformation, seriously threatening construction safety and progress. Therefore, accurately assessing and controlling the stability of the tunnel face is crucial for the safe construction of tunnels in aeolian sand formations. Currently, proactive measures such as pre-reinforcement are commonly used in engineering to control surrounding rock deformation and maintain tunnel face stability.

[0003] Quantitative calculation of tunnel face loads is fundamental for assessing stability and scientifically guiding the design of support structures (including pre-support). Currently, the calculation of tunnel face loads in the field of tunnel engineering largely follows the classic Terzaghi theory formula. However, this traditional method is mainly designed for general soils, and its theoretical model fails to fully consider the mechanical behavior characteristics of special strata such as aeolian sand. Specifically, the classic theory usually assumes that the slip surface is vertical and that the stress inside the slip body is uniformly distributed in the horizontal direction. These simplified assumptions deviate significantly from the actual stress state of aeolian sand strata, resulting in insufficient accuracy of the calculation results and difficulty in truly reflecting the load distribution at the tunnel face. This inaccuracy in calculation directly brings difficulties and uncertainties to the design of support structures and the optimization of construction parameters for tunnels in aeolian sand strata, potentially leading to insufficient support measures and risks. To address these issues, we propose a method for calculating tunnel face loads in aeolian sand strata tunnels. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for calculating tunnel face loads in aeolian sand formations. This method solves the problem that existing methods fail to fully consider the mechanical behavior characteristics of special formations such as aeolian sand in their theoretical models, resulting in significant deviations in the actual stress state of aeolian sand formations and thus insufficient accuracy in the calculation results.

[0005] Existing methods and theoretical models fail to fully consider the mechanical behavior characteristics of special strata such as aeolian sand. The actual stress state of aeolian sand strata has significant deviations, resulting in insufficient accuracy of calculation results. To address these issues, we propose a method for tunnel face load in aeolian sand strata. In short, the method first establishes a sliding body calculation model based on Terzaghi's theory, considering the angle between the fracture surface and the horizontal plane. The sliding body calculation model is then subjected to mechanical analysis to calculate the lateral pressure coefficient. By introducing a coefficient m that characterizes the degree of non-uniform stress distribution, the vertical force balance equation is simplified and solved to obtain the tunnel face load value. In this embodiment of the invention, based on Terzaghi's classical theory and combined with the characteristics of aeolian sand strata, considering the non-uniformity of the slip surface angle and the horizontal stress distribution within the slip body, the method for calculating the tunnel face load is improved. By simplifying and solving the vertical force balance equation, the calculation formula for the tunnel face load value is obtained. This process not only simplifies the calculation steps but also more accurately reflects the actual stress state of the aeolian sand strata, thereby improving the accuracy of the calculation results. Ultimately, it can provide more accurate load values ​​for the design of tunnel support structures, thereby enhancing the safety and stability of the structure and reducing the risk of structural failure due to inaccurate load calculations.

[0006] This invention is implemented as follows: a method for loading the tunnel face in aeolian sand formations, the method comprising:

[0007] S10: Obtain the angle between the fracture surface and the horizontal plane and the internal friction angle of the aeolian sand strata, and establish a sliding body calculation model considering the angle between the fracture surface and the horizontal plane based on Terzaghi's theory.

[0008] S20, Load the pre-built sliding body calculation model, perform mechanical analysis on the sliding body calculation model, and calculate the lateral pressure coefficient;

[0009] S30, obtain the lateral pressure coefficient. Using the lateral pressure coefficient as a priori condition, and considering the non-uniform trapezoidal distribution of vertical and horizontal stresses in the horizontal direction within the sliding body, establish the vertical force balance equation of the horizontal layer of the sliding body. By introducing a coefficient m that characterizes the degree of non-uniform stress distribution, simplify and solve the vertical force balance equation to obtain the face load value.

[0010] Preferably, the sliding body calculation model includes a limiting ellipsoid and an outflow ellipsoid set within the limiting ellipsoid. The outflow ellipsoid is an approximately ellipsoidal region composed of flowing aeolian sand particles. Outside the outflow ellipsoid region, all the aeolian sand particles that have undergone displacement form another ellipsoidal region, which is defined as the limiting ellipsoid. For a given surrounding rock, the eccentricity of the outflow ellipsoid is... It is a constant value;

[0011] Among them, the eccentricity of the outflow ellipsoid The calculation formula is:

[0012]

[0013] In the formula, , These are the major and minor semi-axes of the outflow ellipsoid.

[0014] Preferably, the volume V of the limiting ellipsoid N With respect to the volume V of the outflow ellipsoid G Using loosening coefficient To represent the loosening coefficient The calculation formula is:

[0015]

[0016] Among them, V G V represents the volume of the outflow from the ellipsoid. N Let be the volume of the limiting ellipsoid.

[0017] Preferably, when performing mechanical analysis on the sliding body calculation model, the vertical stress and horizontal stress of the surrounding rock are calculated based on the maximum principal stress and minimum principal stress of the surrounding rock, respectively.

[0018] The formulas for calculating the vertical stress and horizontal stress of the surrounding rock are as follows:

[0019]

[0020]

[0021] in, This is the maximum principal stress; It is the minimum principal stress; For the vertical stress of the surrounding rock; β represents the horizontal stress of the surrounding rock; β is the angle between the maximum principal stress and the vertical direction.

[0022] Preferably, the relationship between the vertical stress and horizontal stress of the surrounding rock and the lateral pressure coefficient is as follows:

[0023]

[0024]

[0025] In the formula, For the vertical stress of the surrounding rock; For the horizontal stress of the surrounding rock, Indicates the lateral pressure coefficient. Let be the radius of the Mohr circle.

[0026] Preferably, the formula for calculating the lateral pressure coefficient is expressed as follows:

[0027]

[0028]

[0029]

[0030] in, The normal stress on the slip surface, Let α be the shear stress on the slip surface, and α be the shear stress on the Mohr circle. and The included angle; It is the internal friction angle of the surrounding rock at the tunnel face.

[0031] Preferably, when establishing the vertical force equilibrium equation of the horizontal layer of the sliding body, the vertical force equilibrium equation of the horizontal layer of the sliding body is expressed as:

[0032]

[0033] Considering that the internal stress of the sliding body follows a trapezoidal distribution in the horizontal direction, and the vertical stress on the slip surface is m times the stress value on the central axis, the relationship between the vertical stress and the horizontal stress of the surrounding rock is as follows:

[0034]

[0035] in, For the vertical stress of the surrounding rock; This refers to the horizontal stress in the surrounding rock.

[0036] Preferably, when simplifying and solving the vertical force equilibrium equation to obtain the face load value, the calculation formula is expressed as follows:

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043] In the formula, B is half the width of the sliding body, γ is the unit weight of the surrounding rock at the tunnel face, h is the tunnel depth, and P0 is the ground surcharge. The vertical stress of the surrounding rock, i.e., the load value at the tunnel face, and These are the stress conversion coefficient, stress relationship coefficient, average stress distribution coefficient, and comprehensive stability coefficient, respectively.

[0044] Preferably, when the coefficient m characterizing the degree of non-uniform stress distribution is introduced, the value of m ranges from 3.256 to 3.745.

[0045] Compared with the prior art, the embodiments of this application have the following main advantages:

[0046] In this embodiment of the invention, based on Terzaghi's classical theory and combined with the characteristics of aeolian sand strata, considering the non-uniformity of the slip surface angle and the horizontal stress distribution within the slip body, the method for calculating the tunnel face load is improved. By simplifying and solving the vertical force balance equation, the calculation formula for the tunnel face load value is obtained. This process not only simplifies the calculation steps but also more accurately reflects the actual stress state of the aeolian sand strata, thereby improving the accuracy of the calculation results. Ultimately, it can provide more accurate load values ​​for the design of tunnel support structures, thereby enhancing the safety and stability of the structure and reducing the risk of structural failure due to inaccurate load calculations. Attached Figure Description

[0047] Figure 1 A schematic diagram of the outflow ellipsoid and the limiting ellipsoid in the sliding body calculation model of an embodiment of the present invention is shown.

[0048] Figure 2 The diagram shows the stress state of the aeolian sand surrounding rock after tunnel excavation in an embodiment of the present invention. Detailed Implementation

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0050] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0051] Existing methods and theoretical models fail to fully consider the mechanical behavior characteristics of special strata such as aeolian sand. The actual stress state of aeolian sand strata has significant deviations, resulting in insufficient accuracy of calculation results. To address these issues, we propose a method for tunnel face load in aeolian sand strata. In short, the method first establishes a sliding body calculation model based on Terzaghi's theory, considering the angle between the fracture surface and the horizontal plane. The sliding body calculation model is then subjected to mechanical analysis to calculate the lateral pressure coefficient. By introducing a coefficient m that characterizes the degree of non-uniform stress distribution, the vertical force balance equation is simplified and solved to obtain the tunnel face load value. In this embodiment of the invention, based on Terzaghi's classical theory and combined with the characteristics of aeolian sand strata, considering the non-uniformity of the slip surface angle and the horizontal stress distribution within the slip body, the method for calculating the tunnel face load is improved. By simplifying and solving the vertical force balance equation, the calculation formula for the tunnel face load value is obtained. This process not only simplifies the calculation steps but also more accurately reflects the actual stress state of the aeolian sand strata, thereby improving the accuracy of the calculation results. Ultimately, it can provide more accurate load values ​​for the design of tunnel support structures, thereby enhancing the safety and stability of the structure and reducing the risk of structural failure due to inaccurate load calculations.

[0052] This invention provides a method for loading the tunnel face of a wind-blown sand tunnel, the method specifically including:

[0053] S10: Obtain the angle between the fracture surface and the horizontal plane and the internal friction angle of the aeolian sand strata, and establish a sliding body calculation model considering the angle between the fracture surface and the horizontal plane based on Terzaghi's theory.

[0054] S20, Load the pre-built sliding body calculation model, perform mechanical analysis on the sliding body calculation model, and calculate the lateral pressure coefficient;

[0055] S30, obtain the lateral pressure coefficient. Using the lateral pressure coefficient as a priori condition, and considering the non-uniform trapezoidal distribution of vertical and horizontal stresses in the horizontal direction within the sliding body, establish the vertical force balance equation of the horizontal layer of the sliding body. By introducing a coefficient m that characterizes the degree of non-uniform stress distribution, simplify and solve the vertical force balance equation to obtain the face load value.

[0056] In this embodiment of the invention, based on Terzaghi's classical theory and combined with the characteristics of aeolian sand strata, considering the non-uniformity of the horizontal stress distribution within the slip surface angle and the slip body, the method for calculating the tunnel face load is improved. By simplifying and solving the vertical force balance equation, a formula for calculating the tunnel face load value is obtained. This process not only simplifies the calculation steps but also more accurately reflects the actual stress state of the aeolian sand strata, thereby improving the accuracy of the calculation results. Ultimately, it can provide more accurate load values ​​for the design of tunnel support structures, thereby enhancing the safety and stability of the structure and reducing the risk of structural failure due to inaccurate load calculations. In the simulation, aeolian sand particles are placed in an ideal large sealed container with a small opening at the bottom. Under the action of gravity, the aeolian sand particles will flow out, and the region formed by all the flowing aeolian sand particles, approximately ellipsoidal, is defined as the outflow ellipsoid. Outside the outflow ellipsoid region, all particles that have undergone displacement form another ellipsoidal region, which is defined as the limiting ellipsoid. Aeolian sand particles outside the limiting ellipsoid do not undergo any displacement and remain stationary.

[0057] It should be noted that as the support force at the tunnel face decreases and the deformation at the tunnel face increases, the aeolian sand particles surrounding the tunnel face begin to exert their shear strength. When the ultimate support force is reached, the displacement of the aeolian sand particles at the tunnel face will increase rapidly, flowing out into the tunnel. Outflow cavities will appear above the tunnel face. The aeolian sand particles above the tunnel face will reach equilibrium during the outflow process. If the burial depth is sufficient, the outflow and collapse of the aeolian sand particles will stop. The cavity area at this point is the ultimate loosening zone of the surrounding rock at the tunnel face of the aeolian sand tunnel.

[0058] In a further preferred embodiment of the present invention, Figure 1 This diagram illustrates the outflow ellipsoid and the limiting ellipsoid in the sliding body calculation model of this invention. The sliding body calculation model includes a limiting ellipsoid and an outflow ellipsoid set within the limiting ellipsoid. The outflow ellipsoid is an approximately ellipsoidal region composed of flowing aeolian sand particles. Outside the outflow ellipsoid region, all displaced aeolian sand particles form another ellipsoidal region, defined as the limiting ellipsoid. The size of the outflow ellipsoid depends only on the properties of the surrounding rock at the tunnel face, the excavation span, and the width. For a given surrounding rock, the eccentricity of the outflow ellipsoid is... It is a constant value.

[0059] Among them, the eccentricity of the outflow ellipsoid The calculation formula is:

[0060]

[0061] In the formula, , For the semi-major and semi-minor axes of the outflow ellipsoid, the eccentricity is... The value is 0.92-0.96. In this embodiment, the aeolian sand particle size is 0.92.

[0062] In this embodiment, the volume V of the limiting ellipsoid N With respect to the volume V of the outflow ellipsoid G Using loosening coefficient To represent the loosening coefficient The calculation formula is:

[0063]

[0064] Among them, V G V represents the volume of the outflow from the ellipsoid. N Let be the volume of the limiting ellipsoid, where is the loosening coefficient. The value range is 1.066-1.1, and in this embodiment, the aeolian sand particle value is 1.1.

[0065] The aforementioned ellipsoid refers to a three-dimensional structure. Tunnel excavation can be considered as an infinitely long structure in one direction and expandable in the other, which is a planar problem. In this case, the limit of loosening at the tunnel face is a limit ellipse, and the outflow ellipsoid is also an outflow ellipse.

[0066] Under adequate support conditions at the tunnel face in aeolian sand formations, aeolian sand particles in front of the tunnel face will not flow out or even shift. As the support pressure at the tunnel face gradually decreases to the ultimate support force, the area of ​​loosened aeolian sand particles in front of the tunnel face gradually expands and develops upwards to its maximum, eventually forming an ultimate elliptical loosening zone. When the support force is less than the ultimate support force, the aeolian sand particles in the ultimate loosening zone will gradually flow out. If the burial depth is sufficient and the tunnel interior space is infinitely large, an ultimate elliptical loosening zone will eventually form. In the unsupported state, it is equivalent to the aforementioned outlet. If the burial depth is sufficient and the tunnel interior space is infinitely large, an ultimate elliptical loosening zone will form.

[0067] To determine the extent of the ultimate elliptical loosening zone, it is assumed that the area of ​​the outflowing elliptical loosening zone under the ultimate support force is the same as the tunnel cross-section. For circular tunnels:

[0068]

[0069] In the formula: , The major and minor axes of the outflow ellipsoid are denoted by ; D is the diameter of the tunnel cross-section.

[0070] , The formulas for calculating the major and minor semi-axes of the outflow ellipsoid are as follows:

[0071]

[0072]

[0073] The area VG of the limiting elliptic loosened region is:

[0074]

[0075] In the formula, Let be the major and minor semi-axes of the limiting ellipse.

[0076] Since the limiting ellipse and the assumed outflow ellipse have the same eccentricity, we can obtain the following by combining the above equations:

[0077]

[0078]

[0079] In this embodiment of the invention, when establishing a sliding body calculation model considering the angle between the fracture surface and the horizontal plane based on Terzaghi's theory, Terzaghi assumed a slip angle of 90°, i.e., a vertical slip surface. The formula for loose earth pressure was derived from the sliding door test, and the expression for the loose earth pressure above the tunnel face is:

[0080]

[0081] in, denoted as , where is the unit weight of the surrounding rock at the tunnel face; c is the cohesion of the surrounding rock at the tunnel face. denoted as φ, where φ is the internal friction angle of the surrounding rock at the tunnel face; k is the lateral pressure coefficient on the slip surface, which can be taken as 1.0; z is the thickness of the overburden layer above the tunnel; q is the distributed load on the ground; B is half the width of the slip body, with the following values:

[0082]

[0083] As can be seen from the above formula, Terzaghi's classical theoretical calculation formula is simple to calculate, taking the lateral pressure coefficient on the slip surface as 1 and neglecting the internal stress of the slip body. Inhomogeneity in the horizontal direction.

[0084] Therefore, this embodiment makes some improvements to the pressure on loosened soil in Terzaghi using aeolian sand as a medium, and makes the following basic assumptions:

[0085] (1) The aeolian sand grain surrounding rock is an isotropic elastoplastic body, and its failure follows the Mohr-Coulomb criterion.

[0086] (2) After the tunnel is excavated in the aeolian sand stratum, the edge of the extreme elliptical zone is the slip surface, the angle between the slip surface and the horizontal direction is θ, the aeolian sand particles on the slip surface are in the extreme equilibrium state and have reached the shear strength, while the particles located between the extreme elliptical zone and the flow elliptical zone are the loose area.

[0087] (3) Internal stress of the sliding body The horizontal stress follows a trapezoidal distribution, and the vertical stress on the slip surface is m times that on the central axis.

[0088]

[0089] The value of m ranges from 3.256 to 3.745, and for ease of calculation, this embodiment uses 3.4.

[0090] In this embodiment of the invention, Figure 2 This invention illustrates the stress state of aeolian sand surrounding rock after tunnel excavation in an embodiment of the invention. Figure 2 This is a schematic diagram of the Mohr's circle of soil on the slip surface, where... This is the maximum principal stress; It is the minimum principal stress; For the vertical stress of the surrounding rock; β is the horizontal stress of the surrounding rock; β is the angle between the maximum principal stress and the vertical direction; and the normal stress on the slip surface is set as... The shear stress is set as The angle θ between the slip surface and the horizontal plane is assumed to be... and The included angle on the Mohr circle is α. When performing mechanical analysis on the sliding body calculation model, the vertical stress and horizontal stress of the surrounding rock are calculated based on the maximum principal stress and minimum principal stress of the surrounding rock, respectively.

[0091] The formulas for calculating the vertical stress and horizontal stress of the surrounding rock are as follows:

[0092]

[0093]

[0094] in, This is the maximum principal stress; It is the minimum principal stress; For the vertical stress of the surrounding rock; β represents the horizontal stress of the surrounding rock; β is the angle between the maximum principal stress and the vertical direction.

[0095] The relationship between the vertical stress and horizontal stress of the surrounding rock and the lateral pressure coefficient is as follows:

[0096]

[0097]

[0098] In the formula, For the vertical stress of the surrounding rock; For the horizontal stress of the surrounding rock, Indicates the lateral pressure coefficient. Let be the radius of the Mohr circle.

[0099] In this embodiment of the invention, the formula for calculating the lateral pressure coefficient is expressed as follows:

[0100]

[0101]

[0102]

[0103] in, The normal stress on the slip surface, Let α be the shear stress on the slip surface, and α be the shear stress on the Mohr circle. and The included angle; Let K be the internal friction angle of the surrounding rock at the tunnel face. It can be seen that for aeolian sand particles, the lateral earth pressure coefficient K is only related to the slip surface dip angle θ and the friction angle. related.

[0104] In this embodiment of the invention, when establishing the vertical force equilibrium equation of the horizontal layer of the sliding body, the vertical force equilibrium equation of the horizontal layer of the sliding body is expressed as:

[0105]

[0106] Considering that the internal stress of the sliding body follows a trapezoidal distribution in the horizontal direction, and the vertical stress on the slip surface is m times the stress value on the central axis, the relationship between the vertical stress and the horizontal stress of the surrounding rock is as follows:

[0107]

[0108] in, For the vertical stress of the surrounding rock; denoted as , where m ranges from 3.256 to 3.745.

[0109] When simplifying and solving the vertical force equilibrium equation to obtain the face load value, the calculation formula is expressed as follows:

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] In the formula, B is half the width of the sliding body, γ is the unit weight of the surrounding rock at the tunnel face, h is the tunnel depth, and P0 is the ground surcharge. The vertical stress of the surrounding rock, also known as the face load, is a term used in geotechnical and tunnel engineering. It's important to note that "pressure" and "load" are often used interchangeably to refer to the forces exerted by the soil or rock mass on a structure. In this embodiment, "vertical pressure of the surrounding rock" is a stress term used in mechanical analysis, while "face load" is a term used in engineering applications. Both refer to the same entity. These are the stress conversion coefficient, stress relationship coefficient, average stress distribution coefficient, and comprehensive stability coefficient, respectively.

[0117] The method for calculating the tunnel face load in aeolian sandy strata proposed in this invention can achieve accurate calculation of the tunnel face load, providing guidance for the scientific design of tunnel support structures and possessing strong applicability and economic value.

[0118] In summary, this invention provides a method for calculating tunnel face loads in aeolian sand formations. In this embodiment, based on Terzaghi's classical theory and considering the characteristics of aeolian sand formations, as well as the non-uniformity of the horizontal stress distribution within the slip surface angle and the slip body, the method for calculating tunnel face loads is improved. By simplifying and solving the vertical force balance equations, a formula for calculating the tunnel face load value is obtained. This process not only simplifies the calculation steps but also more accurately reflects the actual stress state of the aeolian sand formation, thereby improving the accuracy of the calculation results. Ultimately, it can provide more accurate load values ​​for the design of tunnel support structures, thereby enhancing the safety and stability of the structure and reducing the risk of structural failure due to inaccurate load calculations.

[0119] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0120] It should be understood that the disclosed apparatus can be implemented in other ways, given the several embodiments provided in this application. For example, the apparatus embodiments described above are merely illustrative; the division of units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or communication connections shown or discussed may be through some interfaces; the indirect coupling or communication connections between devices or units may be telecommunications or other forms.

[0121] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add, delete, or otherwise adjust the features of the various embodiments of the present invention according to the circumstances without conflict or creative effort, thereby obtaining different technical solutions that do not fundamentally depart from the concept of the present invention. These technical solutions also fall within the scope of protection of the present invention.

Claims

1. A method for applying face load to tunnels in aeolian sand formations, characterized in that, The method includes: S10: Obtain the angle between the fracture surface and the horizontal plane and the internal friction angle of the aeolian sand strata, and establish a sliding body calculation model considering the angle between the fracture surface and the horizontal plane based on Terzaghi's theory. S20, Load the pre-built sliding body calculation model, perform mechanical analysis on the sliding body calculation model, and calculate the lateral pressure coefficient; S30, obtain the lateral pressure coefficient. Using the lateral pressure coefficient as a priori condition, and considering the non-uniform trapezoidal distribution of vertical and horizontal stresses in the horizontal direction within the sliding body, establish the vertical force equilibrium equation of the horizontal layer of the sliding body. By introducing a coefficient m that characterizes the degree of non-uniform stress distribution, simplify and solve the vertical force equilibrium equation to obtain the face load value.

2. The method for loading the tunnel face in aeolian sand formation as described in claim 1, characterized in that: The sliding body calculation model includes a limiting ellipsoid and an outflow ellipsoid set within the limiting ellipsoid. The outflow ellipsoid is an approximately ellipsoidal region composed of flowing aeolian sand particles. Outside the outflow ellipsoid region, all the aeolian sand particles that have undergone displacement form another ellipsoidal region, which is defined as the limiting ellipsoid. For a given surrounding rock, the eccentricity of the outflow ellipsoid is... It is a constant value; Among them, the eccentricity of the outflow ellipsoid The calculation formula is: In the formula, , These are the major and minor semi-axes of the outflow ellipsoid.

3. The method for loading the tunnel face in aeolian sand formation as described in claim 2, characterized in that: The volume V of the limiting ellipsoid N With respect to the volume V of the outflow ellipsoid G Using loosening coefficient To represent the loosening coefficient The calculation formula is: Among them, V G V represents the volume of the outflow from the ellipsoid. N Let be the volume of the limiting ellipsoid.

4. The method for loading the tunnel face in aeolian sand formation as described in claim 3, characterized in that: When performing mechanical analysis on the sliding body calculation model, the vertical stress and horizontal stress of the surrounding rock are calculated based on the maximum principal stress and minimum principal stress of the surrounding rock, respectively. The formulas for calculating the vertical stress and horizontal stress of the surrounding rock are as follows: in, This is the maximum principal stress; It is the minimum principal stress; For the vertical stress of the surrounding rock; β represents the horizontal stress of the surrounding rock; β is the angle between the maximum principal stress and the vertical direction.

5. The method for loading the tunnel face in aeolian sand formation as described in claim 4, characterized in that: The relationship between the vertical stress and horizontal stress of the surrounding rock and the lateral pressure coefficient is as follows: In the formula, For the vertical stress of the surrounding rock; For the horizontal stress of the surrounding rock, Indicates the lateral pressure coefficient. Let be the radius of the Mohr circle.

6. The method for loading the tunnel face in aeolian sand formation as described in claim 5, characterized in that: The formula for calculating the lateral pressure coefficient is as follows: in, The normal stress on the slip surface, Let α be the shear stress on the slip surface, and α be the shear stress on the Mohr circle. and The included angle; It is the internal friction angle of the surrounding rock at the tunnel face.

7. The method for loading the tunnel face in aeolian sand formation as described in claim 6, characterized in that: When establishing the vertical force equilibrium equation for the horizontal layer of the sliding body, the vertical force equilibrium equation for the horizontal layer of the sliding body is expressed as follows: Considering that the internal stress of the sliding body follows a trapezoidal distribution in the horizontal direction, and the vertical stress on the slip surface is m times the stress value on the central axis, the relationship between the vertical stress and the horizontal stress of the surrounding rock is as follows: in, For the vertical stress of the surrounding rock; This refers to the horizontal stress in the surrounding rock.

8. The method for loading the tunnel face in aeolian sand formation as described in claim 7, characterized in that: When simplifying and solving the vertical force equilibrium equation to obtain the face load value, the calculation formula is expressed as follows: In the formula, B is half the width of the sliding body, γ is the unit weight of the surrounding rock at the tunnel face, h is the tunnel depth, and P0 is the ground surcharge. The vertical stress of the surrounding rock, i.e., the load value at the tunnel face, and These are the stress conversion coefficient, stress relationship coefficient, average stress distribution coefficient, and comprehensive stability coefficient, respectively.

9. The method for loading the tunnel face in aeolian sand formation as described in claim 7, characterized in that: When the coefficient m, which characterizes the degree of non-uniform stress distribution, is introduced, the value of m ranges from 3.256 to 3.745.

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