Method for correcting wind-blown sand stratum tunnel load

Abstract

The invention discloses a method for correcting a tunnel load of an aeolian sand stratum, belongs to the technical field of tunnel engineering support, and solves the problems that an existing calculation method is difficult to accurately reflect a real load distribution rule of the aeolian sand stratum and the calculation result is relatively large in deviation. The method comprises the steps of establishing a vertical stress calculation model considering the incomplete soil arching effect in an aeolian sand stratum, establishing a calculation formula of a span influence coefficient, establishing a calculation formula of a surrounding rock level influence coefficient, comprehensively considering the influence of the surrounding rock level and the tunnel span, and calculating the surrounding rock level influence coefficient based on multiple linear regression analysis. Establishing a final calculation formula of the wind-blown sand stratum tunnel surrounding rock load; according to the method, the wind-blown sand stratum tunnel load correction calculation method considering the surrounding rock level and span is established on the basis of the novel method theory, quantitative load solving based on the special physical characteristics of the wind-blown sand stratum is achieved, and a key technical support is provided for promoting scientific design and risk prevention and control of a wind-blown sand tunnel supporting structure.

Description

Technical Field

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

[0002] Tunnel engineering, as a crucial component of infrastructure construction such as transportation and water conservancy, directly impacts the safety and economy of the project through the rationality of its support structure design. The surrounding rock load is a core parameter in support structure design, referring to the force exerted on the support structure by the surrounding rock after tunnel excavation, reflecting the interaction between the rock and the support structure. Its magnitude and distribution have a decisive influence on the strength design, stability verification, and overall safety of the support structure. In practical engineering, accurate calculation of the surrounding rock load is key to ensuring the safety and economy of the tunnel support structure.

[0003] Currently, the calculation of tunnel surrounding rock loads largely relies on empirical analogy methods or simplified theoretical models based on Protodyakonov's theory and Terzaghi's formula. These methods are suitable for strata with homogeneous lithology and relatively stable structures. However, in aeolian sand strata, the surrounding rock exhibits unique engineering characteristics such as poor cohesion, poor particle size distribution, loose structure, and susceptibility to collapse, making it difficult for traditional calculation methods to accurately reflect the true load distribution. Empirical analogy methods often result in significant deviations due to a lack of systematic data support for aeolian sand strata; while simplified formulas do not fully consider key mechanical behaviors in such strata, such as incomplete soil arching and complex stress paths. Directly applying these formulas can easily lead to dangerous or conservative support structure designs, posing safety hazards or causing unnecessary waste in the project. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for load correction in tunnels in aeolian sand formations. This method solves the problem that existing calculation methods are unable to accurately reflect the true load distribution patterns in aeolian sand formations, resulting in significant deviations in calculation results.

[0005] To address the problem that existing calculation methods struggle to accurately reflect the true load distribution in aeolian sandy strata, resulting in significant deviations in calculation results, we propose a method for load correction in tunnels within aeolian sandy strata. In short, this method first establishes a vertical stress calculation model for aeolian sandy strata considering the incomplete soil arching effect based on the new ST method theory. Then, it establishes calculation formulas for the span influence coefficient and the surrounding rock grade influence coefficient. Finally, considering the combined effects of surrounding rock grade and tunnel span, and based on multiple linear regression analysis, it establishes a final calculation formula for the surrounding rock load of tunnels in aeolian sandy strata, and uses this formula for tunnel support structure design. This invention, based on the new ST method theory, considers the incomplete soil arching effect, analyzes the influence of surrounding rock grade and span on the load, and establishes a load correction calculation method for tunnels in aeolian sandy strata considering both surrounding rock grade and span. It achieves quantitative load solutions based on the unique physical characteristics of aeolian sandy strata, providing key technical support for advancing the scientific design and risk control of aeolian sandy tunnel support structures, and possesses significant engineering practical value.

[0006] This invention is implemented as follows: a method for load correction in tunnels in aeolian sand formations, the method comprising:

[0007] S10. Based on the new ST-method theory, a vertical stress calculation model considering the incomplete soil arching effect is established in aeolian sand strata, and the expression of vertical stress in sandy soil under the vertical stress calculation model is obtained.

[0008] S20. Based on the statistical analysis of the surrounding rock pressure at the monitoring section of the existing aeolian sand stratum tunnel, the influence law of tunnel span on surrounding rock load is determined, and the calculation formula of the span influence coefficient is established.

[0009] S30. Based on the statistical analysis of the surrounding rock pressure at the monitoring section of the existing aeolian sand stratum tunnel, the influence law of the surrounding rock grade on the surrounding rock load is determined, and the calculation formula of the surrounding rock grade influence coefficient is established.

[0010] S40, taking into account the influence of surrounding rock grade and tunnel span, based on multiple linear regression analysis, the final calculation formula for the surrounding rock load of tunnels in aeolian sandy strata is established, and the formula is used for the design of tunnel support structure.

[0011] Preferably, when establishing the vertical stress calculation model for aeolian sand strata considering the incomplete soil arching effect, the equilibrium condition is used. The vertical and tangential stresses are obtained, and the formulas for calculating the vertical and tangential stresses are as follows:

[0012]

[0013]

[0014] In the formula, Indicates vertical stress. For tangential stress, Let d be the internal friction angle of the surrounding rock, dh be the unit length perpendicular to the plane of the paper, and B be the internal friction angle of the surrounding rock. h Let h be the width of the infinitesimal element at any depth h, and K be the lateral pressure coefficient.

[0015] Preferably, the expression for the vertical stress in sandy soil under the vertical stress calculation model is as follows:

[0016]

[0017] In the formula, B R The width of the horizontal line of the arch within the potential fracture surface. It is the unit weight of the surrounding rock.

[0018] Preferably, the calculation formula for the span influence coefficient of the Class V and Class IV surrounding rock is expressed as follows:

[0019]

[0020] In the formula, This refers to the tunnel span.

[0021] Preferably, when determining the influence law of surrounding rock grade on surrounding rock load and establishing the calculation formula for the influence coefficient of surrounding rock grade, the calculation formula for the influence coefficient of surrounding rock grade is expressed as follows:

[0022]

[0023] in, The influence coefficient of the surrounding rock grade. This is the span influence coefficient. The surrounding rock level, The correlation coefficient between the surrounding rock grade and the span is denoted as .

[0024] Preferably, when establishing the final calculation formula for the surrounding rock load of tunnels in aeolian sand formations, the calculation formula is expressed as follows:

[0025]

[0026] in, For tunnel surrounding rock load in aeolian sandy strata, The width of the tunnel. The tunnel span is for aeolian sandy strata.

[0027] Compared with the prior art, the embodiments of this application have the following main advantages:

[0028] Based on the new ST-method theory, this invention considers the incomplete soil arching effect, analyzes the influence of surrounding rock grade and span on the load, and establishes a load correction calculation method for aeolian sand tunnels considering surrounding rock grade and span. It realizes the quantitative solution of load based on the special physical characteristics of aeolian sand strata, and provides key technical support for promoting the scientific design and risk prevention of aeolian sand tunnel support structures, which has significant engineering practical value. Attached Figure Description

[0029] Figure 1 A schematic diagram of the tunnel arch effect is shown.

[0030] Figure 2 A schematic diagram of the vertical stress calculation model for the incomplete soil arching effect in an embodiment of the present invention is shown.

[0031] Figure 3 The measured average value of the surrounding rock contact pressure for each span of Class IV surrounding rock is shown, along with the curves illustrating the variation of the measured value with the span.

[0032] Figure 4 The curves showing the variation of measured values ​​of surrounding rock contact pressure with span for each span of Class V surrounding rock are presented. Detailed Implementation

[0033] 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.

[0034] 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.

[0035] To address the problem that existing calculation methods struggle to accurately reflect the true load distribution in aeolian sandy strata, resulting in significant deviations in calculation results, we propose a method for load correction in tunnels within aeolian sandy strata. In short, this method first establishes a vertical stress calculation model for aeolian sandy strata considering the incomplete soil arching effect based on the new ST method theory. Then, it establishes calculation formulas for the span influence coefficient and the surrounding rock grade influence coefficient. Finally, considering the combined effects of surrounding rock grade and tunnel span, and based on multiple linear regression analysis, it establishes a final calculation formula for the surrounding rock load of tunnels in aeolian sandy strata, and uses this formula for tunnel support structure design. This invention, based on the new ST method theory, considers the incomplete soil arching effect, analyzes the influence of surrounding rock grade and span on the load, and establishes a load correction calculation method for tunnels in aeolian sandy strata considering both surrounding rock grade and span. It achieves quantitative load solutions based on the unique physical characteristics of aeolian sandy strata, providing key technical support for advancing the scientific design and risk control of aeolian sandy tunnel support structures, and possesses significant engineering practical value.

[0036] This invention provides a method for load correction in tunnels located in aeolian sand formations. The method specifically includes:

[0037] S10. Based on the new ST-method theory, a vertical stress calculation model considering the incomplete soil arching effect is established in aeolian sand strata, and the expression of vertical stress in sandy soil under the vertical stress calculation model is obtained.

[0038] S20. Based on the statistical analysis of the surrounding rock pressure at the monitoring section of the existing aeolian sand stratum tunnel, the influence law of tunnel span on surrounding rock load is determined, and the calculation formula of the span influence coefficient is established.

[0039] S30. Based on the statistical analysis of the surrounding rock pressure at the monitoring section of the existing aeolian sand stratum tunnel, the influence law of the surrounding rock grade on the surrounding rock load is determined, and the calculation formula of the surrounding rock grade influence coefficient is established.

[0040] S40, taking into account the influence of surrounding rock grade and tunnel span, based on multiple linear regression analysis, the final calculation formula for the surrounding rock load of tunnels in aeolian sandy strata is established, and the formula is used for the design of tunnel support structure.

[0041] This invention, based on the new ST-method, considers the incomplete soil arching effect and analyzes the influence of surrounding rock grade and span on load. It establishes a load correction calculation method for tunnels in aeolian sand formations that considers both surrounding rock grade and span, achieving quantitative load solutions based on the unique physical characteristics of aeolian sand formations. This effectively overcomes the adaptability problems of traditional empirical analogy methods and simplified formulas when dealing with aeolian sand formations with poor cohesion and loose structure. Through multiple regression analysis based on a large amount of measured data, the accuracy and reliability of load prediction results are significantly improved. This provides a scientific basis for the parameter design of support structures, especially prestressed anchors, reducing the risk of insufficient support strength or over-design due to load estimation errors. Thus, while ensuring project safety, it optimizes material usage, demonstrating significant economic and safety value. Ultimately, it provides key technical support for advancing the scientific design and risk control of aeolian sand tunnel support structures, possessing significant engineering practical value.

[0042] In this embodiment of the invention, when establishing a vertical stress calculation model considering the incomplete arching effect in aeolian sand strata based on STMicroelectronics theory, according to STMicroelectronics theory, in tunnels with weak surrounding rock, the arching effect of the surrounding rock forms far from the tunnel outline, while under extreme geological conditions, there is no arching effect at all in the surrounding rock. In this case, various pre-constraint and pre-reinforcement measures become the guarantee for safe tunnel excavation. Among them, before reaching the tunnel face, the strength of the tunnel face-advanced core soil is protected and enhanced by pre-constraint and pre-reinforcement measures, thereby promoting the formation of the arching effect in the region close to the theoretical tunnel outline. The presence of pre-constraint and pre-reinforcement measures causes the stress flow in the surrounding rock to develop towards the tunnel wall, thereby reducing the plastic zone around the tunnel. However, since these measures also restrict the radial displacement of the surrounding rock, although the soil around the tunnel has relaxed, its shear stress has not reached its shear strength, and the arching effect cannot be fully utilized. The surrounding rock pressure in this case is between the loosening pressure and the Terzaghi loosened soil pressure, which is called the surrounding rock pressure under the incomplete arching effect. Figure 1 A schematic diagram of the tunnel arching effect is shown. Specifically, in this embodiment of the invention, when establishing a vertical stress calculation model considering the incomplete soil arching effect in aeolian sand strata, Figure 2 This diagram illustrates a vertical stress calculation model for the incomplete soil arching effect in an embodiment of the present invention. It assumes that the directions of the shear stress and normal stress acting on the soil strip do not deflect with the deflection of the principal stress direction, based on the equilibrium condition. The vertical and tangential stresses are obtained, and the formulas for calculating the vertical and tangential stresses are as follows:

[0043]

[0044]

[0045] In the formula, Indicates vertical stress. For tangential stress, Let d be the internal friction angle of the surrounding rock, dh be the unit length perpendicular to the plane of the paper, and B be the internal friction angle of the surrounding rock. h Let h be the width of the infinitesimal element at any depth h, and K be the lateral pressure coefficient.

[0046] The expression for the vertical stress in sandy soil under the vertical stress calculation model is as follows:

[0047]

[0048] In the formula, B R The width of the horizontal line of the arch within the potential fracture surface. It is the unit weight of the surrounding rock.

[0049] In this embodiment of the invention, based on the statistical analysis of the surrounding rock pressure at the monitoring section of an existing aeolian sand tunnel, the influence of tunnel span on the surrounding rock load is determined. The tunnels are classified according to span as small span (5.0-8.5m), medium span (8.5-12.0m), and large span (12.0-15.0m). To eliminate the influence of span, h0 = h 实测 / ω 修正 The influence coefficient of the surrounding rock grade is used as the ordinate, and the surrounding rock grade is used as the abscissa to analyze h. 实测 / ω 修正 The variation law of surrounding rock grade is followed. In this embodiment, the measured value of surrounding rock contact pressure is compared with the theoretical calculation value of tunnel code according to the difference of surrounding rock grade based on statistical data, and numerical fitting is performed to obtain the influence coefficient of span on surrounding rock contact pressure. The formula of influence coefficient of tunnel width in aeolian sand strata is also corrected. In order to perform numerical fitting, a typical span is selected in each span according to the distribution law of measured data. The specific values ​​are shown in Table 1 below.

[0050] To eliminate the influence of surrounding rock grade and unit weight on the value of surrounding rock contact pressure, the ratio of the surrounding rock contact pressure to a specific benchmark surrounding rock contact pressure is used as the degree of influence of span on the surrounding rock contact pressure. This is used to analyze the numerical relationship between span and contact pressure. Specifically, the surrounding rock contact pressure corresponding to an 8.5m span is set as F0, and the surrounding rock contact pressure corresponding to other spans is set as F... n Then F n Using / F0 as the ordinate, analyze F n The variation of / F0 with span.

[0051] Among them, the correction of the influence coefficient of the surrounding rock width for Class IV surrounding rock is as follows: Figure 3Table 2 shows the measured average value of the surrounding rock contact pressure for each span of Class IV surrounding rock and the curve of the measured value changing with the span;

[0052] Assume the fitting function is

[0053]

[0054] The final fitting formula is:

[0055]

[0056] The correlation coefficient is .

[0057] Correction for the influence coefficient of the width of Class V surrounding rock: Table 3 shows the measured average value of the contact pressure of the surrounding rock for each span of Class V surrounding rock. Figure 4 The curves showing the variation of measured values ​​of surrounding rock contact pressure with span for each span of Class V surrounding rock are presented.

[0058] The final fitting formula is:

[0059]

[0060] The correlation coefficient is .

[0061] Therefore, the calculation formula for the span influence coefficient of the Class V and Class IV surrounding rock is expressed as follows:

[0062]

[0063] In the formula, This refers to the tunnel span.

[0064] Considering the significant impact of the nature, magnitude, and distribution of surrounding rock pressure on the structural design of tunnel lining, and the importance of choosing the construction method, different lateral pressure coefficients under the same vertical stress result in significantly different calculated results depending on the stress conditions of the lining structure. Many factors influence surrounding rock pressure, such as the properties of the rock mass itself, the time effect of surrounding rock pressure, the dimensions of the excavation cross-section, the tunnel depth, construction methods, and support types. In the tunnel structural design process, rationally determining the earth pressure load acting on the support structure is crucial. In the design of mountain railway tunnels, Class I surrounding rock is generally rare. If this type of surrounding rock is encountered, the structural design and construction methods should generally be specially handled. Class V and above surrounding rock generally do not pose significant problems for tunnel stability due to their better integrity. Therefore, the three types of surrounding rock that have a greater impact on tunnel stability and tunnel support structures are Class II, Class III, and Class IV. In this embodiment of the invention, when determining the influence law of surrounding rock level on surrounding rock load and establishing the calculation formula for the influence coefficient of surrounding rock level, the calculation formula for the influence coefficient of surrounding rock level is expressed as:

[0065]

[0066] in, The influence coefficient of the surrounding rock grade. This is the span influence coefficient. The surrounding rock level, The correlation coefficient between the surrounding rock grade and the span is denoted as .

[0067] Currently, tunnel lining structure calculations generally employ a load-structure model. First, the depth of burial is determined. Then, the magnitude of the load acting on the lining structure is calculated using appropriate formulas. Finally, the internal forces of the lining are checked using structural mechanics methods to ensure the safety of the lining structure. Generally, the load on the lining is mainly affected by the following factors: tunnel shape, tunnel span L, surrounding rock grade S, tunnel burial depth H, and support effects. This application uses SPSS multivariate regression analysis software to perform regression analysis on the load calculation method for tunnels in aeolian sandy strata based on field-measured surrounding rock contact pressure data. This application assumes that the tunnel span L, surrounding rock grade S, and tunnel burial depth H are independent of each other. In this embodiment, the final calculation formula for the surrounding rock load of tunnels in aeolian sandy strata is expressed as follows:

[0068]

[0069] in, For tunnel surrounding rock load in aeolian sandy strata, The width of the tunnel. For tunnel spans in aeolian sandy strata, It can be used for vertical surrounding rock loads.

[0070] In summary, this invention provides a method for load correction in aeolian sand tunnels. Based on the new ST-method, this invention considers the incomplete soil arching effect, analyzes the influence of surrounding rock grade and span on the load, and establishes a load correction calculation method for aeolian sand tunnels considering surrounding rock grade and span. It achieves quantitative load solution based on the special physical characteristics of aeolian sand strata, effectively overcoming the adaptability problems of traditional empirical analogy methods and simplified formulas when dealing with aeolian sand strata with poor cohesion and loose structure. Through multiple regression analysis based on a large amount of measured data, the accuracy and reliability of load prediction results are significantly improved. This provides a scientific basis for the parameter design of support structures, especially prestressed anchors, reducing the risk of insufficient support strength or over-design due to load estimation errors. Thus, while ensuring project safety, it optimizes material usage, exhibiting significant economic and safety value. Ultimately, it provides key technical support for promoting the scientific design and risk control of aeolian sand tunnel support structures, demonstrating significant engineering practical value.

[0071] 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.

[0072] 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.

[0073] 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 load correction in tunnels located in aeolian sand formations, characterized in that, The method includes: S10. Based on the new ST-method theory, a vertical stress calculation model considering the incomplete soil arching effect is established in aeolian sand strata, and the expression of vertical stress in sandy soil under the vertical stress calculation model is obtained. S20. Based on the statistical analysis of the surrounding rock pressure at the monitoring section of the existing aeolian sand stratum tunnel, the influence law of tunnel span on surrounding rock load is determined, and the calculation formula of the span influence coefficient is established. S30. Based on the statistical analysis of the surrounding rock pressure at the monitoring section of the existing aeolian sand stratum tunnel, the influence law of the surrounding rock grade on the surrounding rock load is determined, and the calculation formula of the surrounding rock grade influence coefficient is established. S40, taking into account the influence of surrounding rock grade and tunnel span, based on multiple linear regression analysis, the final calculation formula for the surrounding rock load of tunnels in aeolian sandy strata is established, and the formula is used for the design of tunnel support structure.

2. The method for load correction in tunnels in aeolian sand formations as described in claim 1, characterized in that: When establishing the vertical stress calculation model for aeolian sand strata considering the incomplete soil arching effect, the equilibrium condition is used. The vertical and tangential stresses are obtained, and the formulas for calculating the vertical and tangential stresses are as follows: In the formula, Indicates vertical stress. For tangential stress, Let d be the internal friction angle of the surrounding rock, dh be the unit length perpendicular to the plane of the paper, and B be the internal friction angle of the surrounding rock. h Let h be the width of the infinitesimal element at any depth h, and K be the lateral pressure coefficient.

3. The method for load correction in tunnels in aeolian sand formations as described in claim 2, characterized in that: The expression for the vertical stress in sandy soil under the vertical stress calculation model is as follows: In the formula, B R The width of the horizontal line of the arch within the potential fracture surface. It is the unit weight of the surrounding rock.

4. The method for load correction in tunnels in aeolian sand formations as described in claim 1, characterized in that: The calculation formula for the span influence coefficient of the Class V and Class IV surrounding rock is expressed as follows: In the formula, This refers to the tunnel span.

5. The method for load correction in tunnels in aeolian sand formations as described in claim 4, characterized in that: When determining the influence law of surrounding rock grade on surrounding rock load and establishing the calculation formula for the influence coefficient of surrounding rock grade, the calculation formula for the influence coefficient of surrounding rock grade is expressed as follows: in, The influence coefficient of the surrounding rock grade. This is the span influence coefficient. The surrounding rock level, The correlation coefficient between the surrounding rock grade and the span is denoted as .

6. The method for load correction in tunnels in aeolian sand formations as described in claim 5, characterized in that: When establishing the final calculation formula for the surrounding rock load of tunnels in aeolian sand formations, the calculation formula is expressed as follows: in, For tunnel surrounding rock load in aeolian sandy strata, The width of the tunnel. The tunnel span is for aeolian sandy strata.

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