Method and system for calculating critical depth of tunnels with deep or shallow burial depth

Abstract

The present application relates to a method and system for calculating the critical depth of tunnel depth and shallowness, the calculation method comprising the following steps: obtaining surrounding rock parameter values ​​and presetting the surface load; constructing a tunnel top surrounding rock pressure calculation model based on the surface load, surrounding rock parameters, and tunnel depth; obtaining the limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model, obtaining a tunnel depth calculation formula when the tunnel top surrounding rock pressure limit value is reached, substituting the obtained surrounding rock parameter values ​​and the preset surface load into the tunnel depth calculation formula to obtain the tunnel depth, which is the critical depth; distinguishing shallow buried tunnels and deep buried tunnels based on the critical depth. The present application makes the calculated critical depth of tunnel depth and shallow buried more consistent with the actual situation of the tunnel, and can be applied to the calculation of critical depth of tunnel depth and shallow buried in layered soil or soft and hard interlayers, has wide applicability, and is of great significance to the safety and economy of tunnel structure design and engineering construction.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel surrounding rock, and in particular to a method and system for calculating the critical depth of a tunnel. Background Art

[0002] The tunnel structure design mainly adopts the stratum structure method and the load structure method. Among them, when calculating the load structure method, it is necessary to first determine the stratum pressure. The stratum pressure and structural form are closely related to the buried depth of the tunnel. How to reasonably and accurately determine the surrounding rock pressure type tunnel and other underground geotechnical engineering fields is a very important research square. The current mainstream surrounding rock pressure calculation methods mainly include the full soil column theory, Puget theory, Terzaghi theory, Bill Bowman formula, Xie Jiawu formula (method in railway and highway design specifications), and the Kako formula and Fenner formula that consider the surrounding rock deformation pressure.

[0003] The full soil column theory is applicable to open-cut backfill projects or tunnels with shallow burial depth and poor geological conditions. The full soil column pressure theory believes that the vertical pressure of the overlying surrounding rock is only related to the tunnel burial depth. When the burial depth is small, the calculated value is consistent with the actual value. However, since the surrounding rock will produce an arch effect when the burial depth is large, the full soil column pressure theory does not consider the stress transfer of the arch effect in the surrounding rock. Therefore, when the burial depth is large, the calculated value is larger than the actual value, and the calculation accuracy is poor.

[0004] The establishment of the Pu theory is based on the natural equilibrium arch theory. It believes that the surrounding rock is a loose body. In addition to the internal friction effect, it also has a certain viscosity. That is, it is assumed that the top of the tunnel can naturally form an arch after the rock and soil are excavated. Therefore, it is only applicable to deep buried tunnels with a certain self-bearing capacity. The pressure acting on the lining structure is only the mass of the loose rock and soil between the pressure arch and the lining structure, and has nothing to do with the rock layer outside the arch and the burial depth of the cavern.

[0005] The Terzaghi theory is mainly applicable to shallow buried tunnels. The Terzaghi theory regards the surrounding rock as a loose body, but with a certain cohesion. It is believed that tunnel excavation causes displacement of the surrounding rock, and the overlying surrounding rock moves downward due to gravity, and a shear surface appears within the influence range of the tunnel. The displacement of surrounding rock particles causes stress transfer between surrounding rock particles, resulting in a certain obstruction of the surrounding rock around the tunnel to the downward moving surrounding rock, so that its minimum support pressure is much smaller than the original stress of the surrounding rock.

[0006] The existing surrounding rock pressure calculation methods are all based on the tunnel surrounding rock pressure in homogeneous strata, which have their own applicability and limitations. At present, a universal tunnel critical depth calculation method has not been proposed to calculate the tunnel critical depth. This method should be applicable to the calculation of tunnel critical depth in layered soil or soft and hard interlayers to provide an effective solution. Summary of the invention

[0007] The present application provides a method and system for calculating the critical depth of tunnel depth and shallow burial, so that the calculated critical depth of tunnel depth and shallow burial is more in line with the actual situation of the tunnel, and can be applied to the calculation of the critical depth of tunnel depth and shallow burial in layered soil or soft and hard interlayers. It has wide applicability and is of great significance to the safety and economy of tunnel structure design and engineering construction.

[0008] In a first aspect, the present application provides a method for calculating the critical depth of a tunnel, including the following steps:

[0009] Data acquisition steps: obtain surrounding rock parameter values ​​and preset surface loads;

[0010] Model construction steps: Construct a calculation model for the surrounding rock pressure at the top of the tunnel based on the surface load, surrounding rock parameters, and tunnel burial depth;

[0011] The critical depth calculation steps are as follows: the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model is calculated to determine the limit value, and the tunnel depth calculation formula at the tunnel top surrounding rock pressure limit value is obtained. The tunnel depth calculated by substituting the obtained surrounding rock parameter value and the preset surface load into the tunnel depth calculation formula is the critical depth;

[0012] Discrimination steps: Distinguish shallow buried tunnels and deep buried tunnels according to the critical depth of deep and shallow buried tunnels.

[0013] In some of the embodiments, in the data acquisition step, the surrounding rock parameters include soil cohesion, soil internal friction angle, soil external friction angle and soil weight.

[0014] In some embodiments, the surrounding rock parameters are obtained from a survey report of the tunnel construction site or measured at the tunnel construction site.

[0015] In some embodiments, the tunnel top surrounding rock pressure calculation model is expressed as:

[0016] (1)

[0017] in:

[0018] (2)

[0019] (3)

[0020] (4)

[0021] (5)

[0022] (6)

[0023] (7)

[0024] (8)

[0025] (9)

[0026] In the formula, is the surrounding rock pressure at the top of the tunnel, is the soil weight, The tunnel depth, is the soil cohesion, is the internal friction angle of soil, is the external friction angle of soil, is the surface load, is half of the equivalent span of the tunnel, is the tunnel height, is the load earth pressure coefficient, is the cohesive earth pressure coefficient, is the heavy earth pressure coefficient, , , , and It is a temporary parameter.

[0027] In some of the embodiments, in the step of calculating the critical depth of deep and shallow burial, the method for obtaining the tunnel burial depth calculation formula when the surrounding rock pressure limit value at the tunnel top is:

[0028] Given the soil weight, soil cohesion, soil internal friction angle, soil external friction angle, and surface load, the tunnel top surrounding rock pressure is only related to the tunnel burial depth. The limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model is calculated and expressed as:

[0029] (10)

[0030] Substituting formula (1) into formula (10), we get:

[0031] (11)

[0032] The calculation formula for the tunnel depth when the surrounding rock pressure limit value at the tunnel top is obtained from formula (11) is expressed as:

[0033] (12)

[0034] In the formula, H max It is the critical depth of shallow burial.

[0035] In some of the embodiments, in the discrimination step, the specific method for discriminating between shallow buried tunnels and deep buried tunnels is: when the tunnel burial depth ≥ the critical depth of shallow buried tunnels, it is a shallow buried tunnel; when the tunnel burial depth < the critical depth of shallow buried tunnels, it is a deep buried tunnel.

[0036] In a second aspect, the present application provides a tunnel depth critical depth calculation system, which is used to implement the tunnel depth critical depth calculation method described in the first aspect of the present application, including:

[0037] Data acquisition module, used to obtain surrounding rock parameter values,

[0038] Setting module, used to preset the surface load;

[0039] Model building module, which builds a calculation model for the surrounding rock pressure at the top of the tunnel based on the surface load, surrounding rock parameters, and tunnel burial depth;

[0040] The critical depth calculation module for deep and shallow burial is used to calculate the limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model, and obtain the tunnel burial depth calculation formula when the tunnel top surrounding rock pressure reaches the limit value. The tunnel burial depth obtained by substituting the obtained surrounding rock parameter value and the preset surface load into the tunnel burial depth calculation formula is the critical depth of deep and shallow burial.

[0041] The discrimination module discriminates shallow buried tunnels and deep buried tunnels according to the critical depth of deep and shallow buried tunnels.

[0042] In some embodiments, the deep and shallow burial critical depth calculation module includes:

[0043] The tunnel depth calculation formula obtaining module calculates the limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model, and obtains the tunnel depth calculation formula when the tunnel top surrounding rock pressure reaches the limit value;

[0044] The deep and shallow burial critical depth calculation module is used to calculate the deep and shallow burial critical depth through the tunnel burial depth calculation formula according to the surrounding rock parameter value and the preset surface load.

[0045] Compared with the prior art, the method and system for calculating the critical depth of tunnel deep and shallow burial provided by the present application comprehensively consider the surface load and surrounding rock parameters, and construct a tunnel top surrounding rock pressure calculation model based on the surface load, surrounding rock parameters and tunnel burial depth. The tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model is extreme, and the tunnel burial depth calculation formula at the tunnel top surrounding rock pressure limit value is obtained. Then, the critical depth of deep and shallow burial is obtained through the tunnel burial depth calculation formula according to the surrounding rock parameter value and the preset surface load. It is suitable for the surrounding rock pressure of layered soil or soft and hard interlayers, has wide applicability, and is of great significance to the safety and economy of tunnel structure design and engineering construction.

[0046] The present application provides a method and system for calculating the critical depth of tunnels with shallow or deep burials. The calculation model expression of the surrounding rock pressure at the top of the tunnel is a continuous function. The surrounding rock pressure at the top of the tunnel changes continuously with the depth without sudden changes, which greatly improves the calculation accuracy and applicability of the model. It is not necessary to process the surrounding rock parameters to obtain parameters such as the equivalent friction angle in order to calculate the critical depth of tunnels with shallow or deep burials, which reduces the complexity of parameter processing during the calculation process and saves time and cost.

[0047] The method and system for calculating the critical depth of tunnels provided by the present application simplifies the calculation process of the critical depth of tunnels, and directly uses the surrounding rock parameters and surface loads for calculation, avoiding cumbersome parameter conversion steps and improving the calculation efficiency. In addition, the continuous tunnel top surrounding rock pressure calculation model makes the calculation results more coherent, reduces the uncertainty and complexity in the calculation process, and improves the overall efficiency.

[0048] The method and system for calculating the critical depth of tunnel depth and shallowness provided in this application are based on the rigorous generalized limit equilibrium theory, and the calculation results are highly reliable and stable. By accurately predicting the critical depth of tunnel depth and shallowness, the uncertainty in tunnel construction can be effectively reduced, and the durability and service life of the tunnel structure can be improved.

[0049] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0051] Figure 1 This is a flow chart of a method for calculating the critical depth of a tunnel according to an embodiment of the present application;

[0052] Figure 2 A flowchart of a method for calculating the critical depth of a tunnel according to another embodiment of the present application

[0053] Figure 3 A schematic diagram of a tunnel top surrounding rock pressure calculation model according to an embodiment of the present application;

[0054] Figure 4 This is a structural block diagram of the tunnel critical depth calculation system described in the embodiment of the present application;

[0055] Figure 5 This is a simplified diagram of the existing Xie Jiawei formula calculation;

[0056] Figure 6This is a comparison chart of the change in tunnel surrounding rock top pressure with depth calculated using the tunnel surrounding rock top pressure calculation model, Terzaghi formula, Xie Jiawei formula, and Bill Bowman formula in the tunnel deep and shallow critical depth calculation method described in the embodiment of the present application.

[0057] In the figure, 1. data acquisition module, 2. setting module, 3. model building module, 4. deep and shallow burial critical depth calculation module, 401. tunnel burial depth calculation formula obtaining module, 402. deep and shallow burial critical depth obtaining module, 5. judgment module. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0059] Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be complicated and lengthy, for ordinary technicians in this field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as insufficient content disclosed in this application.

[0060] Reference to "embodiments" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those of ordinary skill in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0061] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0062] The method and system for calculating the critical depth of tunnel depth and shallowness described in the present application can be used to calculate the critical depth of tunnel depth and shallowness in layered soil or soft and hard interlayers.

[0063] See also Figure 1 , a method for calculating the critical depth of a tunnel provided by an embodiment of the present invention comprises the following steps:

[0064] S1. Data acquisition step: obtain surrounding rock parameter values ​​and preset surface loads.

[0065] Specifically, the surrounding rock parameters include soil cohesion, soil internal friction angle, soil external friction angle and soil weight.

[0066] S2. Model construction steps: Construct a calculation model for the surrounding rock pressure at the top of the tunnel based on the surface load, surrounding rock parameters, and tunnel depth. Figure 3 The tunnel top surrounding rock structure includes soil blocks E'CF', soil blocks CBF', soil blocks ABCD, soil blocks EDF and soil blocks DFA, and W is the vertical pressure at the top of the tunnel. The calculation model of the tunnel top surrounding rock pressure is expressed as:

[0067] (1)

[0068] in:

[0069] (2)

[0070] (3)

[0071] (4)

[0072] (5)

[0073] (6)

[0074] (7)

[0075] (8)

[0076] (9)

[0077] In the formula, is the surrounding rock pressure at the top of the tunnel, is the soil weight, The tunnel depth, is the soil cohesion, is the internal friction angle of soil, is the external friction angle of soil, is the surface load, is half of the equivalent span of the tunnel, is the tunnel height, is the load earth pressure coefficient, is the cohesive earth pressure coefficient, is the heavy earth pressure coefficient, , , , and It is a temporary parameter.

[0078] The tunnel top surrounding rock pressure calculation model constructed above is used to calculate the tunnel top surrounding rock pressure, and its magnitude is related to the tunnel burial depth, surface load and surrounding rock parameters.

[0079] It should be noted that when constructing the calculation model of the surrounding rock pressure at the top of the tunnel, the surface load and surrounding rock parameters are comprehensively considered. The calculation model of the surrounding rock pressure at the top of the tunnel is constructed based on the surface load, surrounding rock parameters, and tunnel burial depth. The expression of the constructed calculation model of the surrounding rock pressure at the top of the tunnel is a continuous function. The surrounding rock pressure at the top of the tunnel changes continuously with depth without mutation, which greatly improves the calculation accuracy and applicability of the model. There is no need to process the surrounding rock parameters to obtain parameters such as the equivalent friction angle in order to calculate the surrounding rock pressure at the top of the tunnel, which reduces the complexity of parameter processing during the calculation process and saves time and cost.

[0080] S3. Calculation steps for critical depth of deep and shallow burial: find the limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model, obtain the tunnel burial depth calculation formula when the tunnel top surrounding rock pressure reaches the limit value, substitute the obtained surrounding rock parameter values ​​and the preset surface load into the tunnel burial depth calculation formula, and the tunnel burial depth obtained is the critical depth of deep and shallow burial.

[0081] Specifically, the method for calculating the tunnel depth when the surrounding rock pressure limit value at the tunnel top is obtained is:

[0082] Given the soil weight, soil cohesion, soil internal friction angle, soil external friction angle, and surface load, the tunnel top surrounding rock pressure is only related to the tunnel burial depth. The limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model is calculated and expressed as:

[0083] (10)

[0084] Substituting formula (1) into formula (10), we get:

[0085] (11)

[0086] The calculation formula for the tunnel depth when the surrounding rock pressure limit value at the tunnel top is obtained from formula (11) is expressed as:

[0087] (12)

[0088] In the formula, H max It is the critical depth of shallow burial.

[0089] It should be noted that the critical depth of deep and shallow burial obtained by formula (12) is obtained by taking the extreme value of the tunnel top rock pressure calculation model expression, that is, formula (1). The tunnel top rock pressure calculation model shown in formula (1) can be applied to the calculation of rock pressure in layered soil or soft and hard interlayers. Existing rock pressure calculation formulas (such as Terzaghi formula, Pugh formula, etc.) are mostly used to calculate the rock pressure in homogeneous strata. The formula (1) of this application comprehensively considers the surface load, the soil cohesion of the surrounding rock, the internal friction angle of the surrounding rock, the external friction angle of the surrounding rock, and the weight of the surrounding rock. It is not necessary to use the method in the railway and highway design specifications to further process the surrounding rock parameters to obtain parameters similar to the equivalent friction angle for calculation, and the calculation of the equivalent friction angle is affected by the experience and theoretical deficiencies of the calculator. However, the formula (1) of this application is a continuous expression, and the surrounding rock pressure changes continuously with depth without sudden changes.

[0090] It should be noted that the surrounding rock pressure calculation formula in the "Railway Tunnel Design Code" is divided into three cases according to the different tunnel burial depths: ultra-shallow, shallow and deep. The full soil column theory is used for ultra-shallow, Xie Jiawei's formula is used for shallow, and the empirical formula based on sample statistics and surrounding rock classification is used for deep. For engineering and technical personnel, this method is convenient for practical application and has a relatively wide range of applications. Xie Jiawei believes that the friction resistance in the tunnel body is smaller than the friction resistance above the top of the tunnel, and the friction angle between the lining and the soil is different from the friction angle between the soil, so only the friction resistance above the top of the tunnel is counted. This simplification is essentially that the clamping force T generated by the wedge A'EG replaces the clamping force F generated by the wedge AEC, and the clamping force T generated by the wedge B'FH replaces the clamping force F generated by the wedge BFD, see Figure 5 , the inclined plane A'G and the inclined plane B'H become oblique sliding surfaces, and the changed model does not consider the sliding of the soil in the tunnel body. If the friction resistance in the tunnel body is considered (the friction resistance in the tunnel body of the New Austrian Tunneling Method is relatively large), due to the friction resistance of the tunnel body acting on the structure, the calculation result is the vertical pressure at the bottom of the tunnel rather than the vertical pressure W at the top of the tunnel. Therefore, whether the theory is strict in the selection of the research object is still worth discussing. When calculating the critical depth of deep burial and shallow burial of the tunnel according to the above theory, the results are quite different. The reason is that the basic assumptions of each theory are inconsistent, and according to the calculation method in the "Highway Tunnel Design Code" and the "Railway Tunnel Design Code", the surrounding rock pressure at the boundary between deep burial and shallow burial will produce discontinuous jumps, which is inconsistent with the actual situation. The tunnel top surrounding rock pressure calculation model constructed by this application is used to calculate the tunnel top surrounding rock pressure. Since the expression of the tunnel top surrounding rock pressure calculation model is a continuous function, the tunnel top surrounding rock pressure changes continuously with depth, and there will be no sudden changes. The surrounding rock pressure at the boundary between deep burial and shallow burial will produce discontinuous jumps, which is consistent with the actual situation.

[0091] S4, discrimination step: discriminate shallow buried tunnels and deep buried tunnels according to the critical depth of deep and shallow buried tunnels.

[0092] Specifically, the specific method for distinguishing shallow buried tunnels and deep buried tunnels is: when the tunnel burial depth ≥ the critical depth of deep and shallow buried, it is a shallow buried tunnel; when the tunnel burial depth < the critical depth of deep and shallow buried, it is a deep buried tunnel.

[0093] In some embodiments, the surrounding rock parameters are obtained from a survey report of the tunnel construction site or measured at the tunnel construction site.

[0094] It should be noted that the steps shown in the above process or the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that here. For example, see Figure 2 , S1. Model construction step: Construct a tunnel top rock pressure calculation model based on surface load, surrounding rock parameters, and tunnel burial depth. S2. Data acquisition step: Obtain surrounding rock parameter values ​​and preset surface loads. S3. Shallow and deep critical depth calculation step: Calculate the limit value of the tunnel top rock pressure in the tunnel top rock pressure calculation model, and obtain the tunnel burial depth calculation formula when the tunnel top rock pressure reaches the limit value. Substitute the obtained surrounding rock parameters and preset surface loads into the tunnel burial depth calculation formula to obtain the tunnel burial depth, which is the shallow and deep critical depth. S4. Discrimination step: Discriminate shallow and deep tunnels based on the shallow and deep critical depths.

[0095] This embodiment also provides a tunnel depth and shallow burial critical depth calculation system, which is used to implement the tunnel depth and shallow burial critical depth calculation method described in the above embodiment. As used below, the terms "module", "unit", "subunit", etc. can implement a combination of software and / or hardware for a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0096] Figure 4 : is a structural block diagram of a tunnel depth critical depth calculation system according to an embodiment of the present application. Figure 6 As shown, the system includes:

[0097] Data acquisition module 1, used to obtain surrounding rock parameter values,

[0098] Setting module 2, used for presetting the surface load;

[0099] Model building module 3, building a calculation model for surrounding rock pressure at the top of the tunnel according to surface load, surrounding rock parameters, and tunnel burial depth;

[0100] The critical depth calculation module 4 calculates the limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model, obtains the tunnel burial depth calculation formula when the tunnel top surrounding rock pressure reaches the limit value, and substitutes the obtained surrounding rock parameter value and the preset surface load into the tunnel burial depth calculation formula to obtain the tunnel burial depth, which is the critical depth;

[0101] The distinguishing module 5 distinguishes shallow buried tunnels and deep buried tunnels according to the critical depth of deep and shallow buried tunnels.

[0102] In some embodiments, the deep-shallow-buried critical depth calculation module 4 includes:

[0103] The tunnel depth calculation formula obtaining module 401 obtains the limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model, and obtains the tunnel depth calculation formula when the tunnel top surrounding rock pressure reaches the limit value;

[0104] The deep and shallow burial critical depth obtaining module 402 is used to calculate the deep and shallow burial critical depth according to the surrounding rock parameter value and the preset surface load through the tunnel burial depth calculation formula.

[0105] It should be noted that the above modules can be functional modules or program modules, and can be implemented by software or hardware. For modules implemented by hardware, the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0106] The following is a specific example to verify the accuracy of the surrounding rock pressure calculated by the tunnel top surrounding rock pressure calculation model constructed by the above-mentioned tunnel deep and shallow burial critical depth calculation method and system of this application.

[0107] Example: Weight of surrounding rock and soil of a tunnel 22kN / m 3 , half of the equivalent span of excavation =7.35m, soil cohesion =100kPa, internal friction angle The external friction angle of soil is 33°. is 33°, surface load The actual value of the tunnel surrounding rock top pressure is 75m. The above calculation method of this application is used to calculate the tunnel surrounding rock top pressure. At the same time, the Terzaghi, Xie Jiayu and Bill Bowman formulas are used to calculate the surrounding rock top pressure respectively. Figure 6 The critical depth of deep and shallow burial calculated by the calculation method of this application is 74m, the critical depth of deep and shallow burial calculated by the Terzaghi formula is 66m, the critical depth of deep and shallow burial calculated by the Bill Bowman formula is 77m, and the critical depth of deep and shallow burial calculated by the Xie Jiayu formula is 50m.

[0108] Depend on Figure 6 It can be seen that the pressure at the top of the tunnel surrounding rock changes with depth. The above calculation method of the present application is consistent with the law of Xie Jiayu and Bill Bowman's formula. As the depth increases, the surrounding rock pressure at the top of the tunnel first increases and then decreases. At the same time, the surrounding rock pressure value of the calculation method of the present invention is continuous, and there is no "mutation" and "inflection point" at the boundary between deep and shallow burial, which is more in line with the actual situation. However, the calculation result of the Terzaghi formula is that the surrounding rock pressure at the top of the tunnel first increases to a certain value and then remains basically unchanged. There are differences in the calculation results of different methods, which are specifically manifested in the different critical depths.

[0109] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for calculating the critical depth of a tunnel, characterized in that: The following steps are involved: Data acquisition step: obtaining surrounding rock parameter values ​​and presetting the surface load; the surrounding rock parameters include soil cohesion, soil internal friction angle, soil external friction angle and soil weight; Model construction steps: construct a tunnel top surrounding rock pressure calculation model based on surface load, surrounding rock parameters, and tunnel burial depth; the tunnel top surrounding rock pressure calculation model is expressed as: （1） in: （2） （3） （4） （5） （6） （7） （8） （9） In the formula, is the surrounding rock pressure at the top of the tunnel, is the soil weight, The tunnel depth, is the soil cohesion, is the internal friction angle of soil, is the external friction angle of soil, is the surface load, is half of the equivalent span of the tunnel, is the tunnel height, is the load earth pressure coefficient, is the cohesive earth pressure coefficient, is the heavy earth pressure coefficient, , , , and It is a temporary parameter; The critical depth calculation steps are as follows: the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model is calculated to determine the limit value, and the tunnel depth calculation formula at the tunnel top surrounding rock pressure limit value is obtained. The tunnel depth calculated by substituting the obtained surrounding rock parameter value and the preset surface load into the tunnel depth calculation formula is the critical depth; Discrimination steps: Distinguish shallow buried tunnels and deep buried tunnels according to the critical depth of deep and shallow buried tunnels.

2. The method for calculating the critical depth of a tunnel according to claim 1, characterized in that: The surrounding rock parameters are obtained from a survey report of the tunnel construction site or measured at the tunnel construction site.

3. The method for calculating the critical depth of a tunnel according to claim 1, characterized in that: In the step of calculating the critical depth of deep and shallow burial, the method for calculating the tunnel burial depth when the surrounding rock pressure limit value at the top of the tunnel is: Given the soil weight, soil cohesion, soil internal friction angle, soil external friction angle, and surface load, the tunnel top surrounding rock pressure is only related to the tunnel burial depth. The limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model is calculated and expressed as: （10） Substituting formula (1) into formula (10), we get: （11） The calculation formula for the tunnel depth when the surrounding rock pressure limit value at the tunnel top is obtained from formula (11) is expressed as: （12） In the formula, It is the critical depth of shallow burial.

4. The method for calculating the critical depth of a tunnel according to claim 1, characterized in that: In the discrimination step, the specific method for discriminating between shallow buried tunnels and deep buried tunnels is: when the tunnel burial depth ≥ the critical depth of shallow buried tunnels, it is a shallow buried tunnel; when the tunnel burial depth < the critical depth of shallow buried tunnels, it is a deep buried tunnel.

5. A tunnel depth critical depth calculation system, used to implement the tunnel depth critical depth calculation method according to any one of claims 1 to 4, characterized in that: include: Data acquisition module, used to obtain surrounding rock parameter values, A setting module for presetting the surface load; Model building module, which builds a calculation model for the surrounding rock pressure at the top of the tunnel based on the surface load, surrounding rock parameters, and tunnel burial depth; The critical depth calculation module for deep and shallow burial is used to calculate the limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model, and obtain the tunnel burial depth calculation formula when the tunnel top surrounding rock pressure reaches the limit value. The tunnel burial depth obtained by substituting the obtained surrounding rock parameter value and the preset surface load into the tunnel burial depth calculation formula is the critical depth of deep and shallow burial. The discrimination module discriminates shallow buried tunnels and deep buried tunnels according to the critical depth of deep and shallow buried tunnels.

6. The tunnel depth critical depth calculation system according to claim 5 is characterized in that: The deep and shallow burial critical depth calculation module includes: The tunnel depth calculation formula obtaining module calculates the limit value of the tunnel top surrounding rock pressure in the tunnel top surrounding rock pressure calculation model, and obtains the tunnel depth calculation formula when the tunnel top surrounding rock pressure reaches the limit value; The deep and shallow burial critical depth calculation module is used to calculate the deep and shallow burial critical depth through the tunnel burial depth calculation formula according to the surrounding rock parameter value and the preset surface load.

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