Method for calculating and measuring stress parameters of initial support structure of tunnel

Abstract

The application provides a calculation and measurement monitoring method for stress parameters of a tunnel initial support structure. The application is based on stress characteristics and arrangement features of the tunnel support structure, and utilizes a single strain gauge to measure the ring axial force, surrounding rock pressure and indirect contact pressure between the lining of the tunnel initial support, thereby saving components, manpower and material resources, and avoiding the situation that soil pressure cells are difficult to arrange and are easy to be damaged when measuring the surrounding rock pressure and the indirect contact pressure between the lining in the prior monitoring scheme.

Description

Technical Field

[0001] This invention belongs to the field of monitoring and measurement technology in the New Austrian Tunneling Method (NATM) for tunnel construction, specifically involving a method for calculating and measuring the stress parameters of the initial support structure of a tunnel. Background Technology

[0002] With the rapid development of my country's transportation industry, tunnels have become an indispensable part of transportation networks such as railways, highways, and subways. The ever-increasing scale of highway construction in my country has propelled the rapid development of highway tunnel construction, leading to the widespread application of the New Austrian Tunneling Method (NATM) in my country's highway tunnel construction. NATM is the most commonly used method in tunnel construction, and monitoring and measurement are crucial aspects of NATM construction. As the main load-bearing structure of the tunnel support structure, the safety and stability of the initial support are particularly important. Simultaneously, understanding the surrounding rock pressure and the contact pressure between the support and the lining helps to promptly relay the stress characteristics of the tunnel support structure to the construction personnel, thereby guiding construction, improving the tunnel support structure, and further ensuring the safety and stability of the tunnel structure during construction and operation. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for calculating and measuring the stress parameters of the initial support structure of a tunnel. Based on the stress characteristics and layout features of the tunnel support structure, this invention utilizes a single strain gauge to measure the circumferential axial force, surrounding rock pressure, and inter-lining contact pressure of the initial support structure. This method saves on components, manpower, and materials, and avoids the difficulties in arranging and the easy damage of earth pressure cells when measuring surrounding rock pressure and inter-lining contact pressure in existing monitoring schemes.

[0004] The present invention is achieved through the following technical solution.

[0005] A method for calculating and measuring the stress parameters of the initial support structure of a tunnel, characterized by the following steps:

[0006] S1. After the tunnel excavation and frame erection and before the shotcrete, several measuring points are set on the web of the steel arch frame. Two strain gauges are arranged axially and laterally on both sides of the axial area of ​​the web of the steel arch frame at each measuring point.

[0007] S2. Zero the initial difference of the strain gauges and record the initial readings of the two strain gauges arranged axially and laterally at each measurement point, denoted as U. x0 U y0 Subsequently, during the initial tunnel support period, the real-time readings of the axially arranged strain gauges at each measuring point were monitored at different times, denoted as U. x The real-time readings of the transversely arranged strain gauges at each measurement point were monitored at different times before the secondary lining was constructed, and denoted as U'. yThe real-time readings of the transversely arranged strain gauges at each measurement point were monitored at different times after the secondary lining was installed, and denoted as U". y When the interaction between the surrounding rock pressure and the steel arch frame reaches equilibrium, the real-time readings of the strain gauges arranged laterally at each measuring point are denoted as U. y1 ;

[0008] S3, Based on the data U measured in step S2 x and U x0 The axial strain value ε of the steel arch frame was calculated. gx Using data ε gx Calculate the initial support circumferential axial force N at each measurement point at different times. x ;

[0009] Based on the data U' obtained in step S2 y and U y0 The transverse strain ε of the steel arch frame under the action of surrounding rock pressure before the secondary lining is constructed is calculated. gy1 Using data ε gy1 Calculate the surrounding rock pressure σ at each measurement point at different times. w :

[0010] Based on the data U obtained in step S2 y and U y1 The transverse strain ε of the steel arch frame under the contact pressure between the linings after the secondary lining is constructed is calculated. gy2 Using data ε gy2 Calculate the interlining contact pressure σ at each measurement point at different times. c :

[0011] S4. Using the time of tunnel secondary lining construction as the dividing line, the initial support circumferential axial force N at each measurement point at different times is measured. x and surrounding rock pressure σ w Contact pressure σ between the lining and the lining c We monitor the values ​​and trends of these values.

[0012] Preferably, in step S1, the number of measurement points is set to 5, which are located on the left arch waist, left arch shoulder, arch top, right arch waist and right arch shoulder of the steel arch frame web.

[0013] Preferably, in step S1, a protective shell is provided on the strain gauge to separate the strain gauge from the subsequent shotcrete.

[0014] Preferably, several of the measurement points are installed on the web of the steel arch frame by a fixing device, which includes a base, a locking device with bolts, and a steel pipe with the same diameter as both ends of the strain gauge.

[0015] Preferably, both the fixing device and the protective shell are made of austenitic stainless steel, and the fixing device and the protective shell are rapidly water-cooled after welding.

[0016] Preferably, the strain gauge used is a surface-type intelligent string strain gauge.

[0017] Specifically, in step S3, the initial support circumferential axial force N x The calculation method is as follows:

[0018] U based on step S2 x and U x0 Because of ε gx =U x -U x0 Calculate ε gx Based on the plane strain assumption and the deformation compatibility principle, the axial strain value ε of the steel arch frame is... gx The strain value ε of the initial support concrete along the axis hx They are approximately equal, i.e., ε gx =ε hx ; will ε hx ε gx Substitute the initial support axial internal force N x The calculation formula is used to calculate the stress parameters of the initial support structure of the tunnel, specifically the axial stress N of the initial support. x .

[0019] Specifically, in step S3, the initial support axial internal force N x The calculation formula is:

[0020] N x =E hx ×ε hx ×S hx +E gx ×ε gx ×S gx ;

[0021] In the above formula, E hx E represents the elastic modulus of the initial support concrete. gx ε is the elastic modulus of the steel arch frame; gx ε represents the axial strain value of the steel arch frame. hx S represents the axial strain value of the initial support concrete; h S is the transverse cross-sectional area of ​​the initial support concrete. g This represents the transverse cross-sectional area of ​​the steel arch frame.

[0022] Specifically, in step S3, the surrounding rock pressure σ w Contact pressure σ between masonry and brickwork c The specific calculation method is as follows:

[0023] Based on the data U' obtained in step S2 y and U y0 The transverse strain ε of the steel arch frame under the action of surrounding rock pressure before the secondary lining is constructed is calculated. gy1 Based on the data U obtained from step S2 y and U y1 The transverse strain ε of the steel arch frame under the contact pressure between the linings after the secondary lining is constructed is calculated. gy2 ; where ε gy1 =U' y -U y0 , ε gy2 =U” y -U y1 ;

[0024] The ε calculated above gy1 ε gy2 Substitute the initial support lateral stress σ into the values ​​respectively. y The calculation formula allows us to calculate the initial lateral stress σ of the secondary lining before its construction. y1 And the initial lateral stress σ after the secondary lining is constructed y 2;

[0025] In the transverse direction of the steel arch frame, due to the complex cross-sectional composition, the strength of the steel arch frame is distributed into the concrete using the equivalent elastic modulus method, treating the initial support as a whole. Before the secondary lining is constructed, the transverse stress σ of the initial support is... y The change is due to the surrounding rock pressure σ w This causes the surrounding rock pressure σ w It can be approximated as equal to the initial support lateral stress σ y Take σ y1 As σ w The final result is the calculation of the surrounding rock pressure σ before the secondary lining is constructed. w After the secondary lining is installed, the contact pressure σ between the linings c It can be approximated as equal to the initial support lateral stress σ y Take σ y2 As σ c The final result is the calculated contact pressure σ between the linings after the secondary lining is installed. c .

[0026] Specifically, the initial support lateral stress σ y The calculation formula is:

[0027] σ y =(E hy +E gy ×A gy / A hy )×ε y ;

[0028] In the above formula, E hy E represents the elastic modulus of the initial support concrete in the transverse direction. gy A represents the transverse elastic modulus of the steel arch frame; gy Let A be the axial cross-sectional area of ​​the steel arch frame. hy ε is the axial cross-sectional area of ​​the initial support concrete; y The initial support lateral strain value; where ε y The value of is ε gy1 At that time, the initial lateral stress σ of the secondary lining before its construction can be calculated. y1 ; where ε y The value of is ε gy2 At that time, the initial lateral stress σ of the secondary lining can be calculated. y2 .

[0029] The beneficial effects of the present invention are: (1) Based on the deformation coordination principle and the equivalence principle, and taking into account the characteristics of the construction and support of the New Austrian Tunneling Method (NATM), during the initial support of the tunnel, two surface-type intelligent string strain gauges are arranged laterally and axially in the web axis area on both sides of the steel arch frame. The axial strain gauge is used to record the axial deformation of the steel arch frame, and the data processing method of the present invention is used to convert it into the axial force of the entire initial support of the tunnel. The transverse strain gauge is used to record the transverse strain of the steel arch frame. Because the contact pressure between the surrounding rock and the initial support has basically reached a stable state before the secondary lining is constructed, the construction of the secondary lining is taken as a dividing line. Before the construction of the secondary lining, the change in the transverse strain gauge reading on the steel arch frame is caused by the surrounding rock pressure. After the construction of the secondary lining, the change in the transverse strain gauge reading on the steel arch frame is caused by the contact pressure between the linings. The data processing method of the present invention is used to convert it into the surrounding rock pressure and the contact pressure between the linings, thereby realizing the measurement of the stress parameters of the initial support structure of the tunnel, such as the circumferential axial force, the surrounding rock pressure and the contact pressure between the linings, using only a single component, namely the strain gauge. (2) This invention separates the components from the concrete, ensuring that the strain gauges are not affected by the concrete and guaranteeing the accuracy of the measurement results. (3) Traditional methods for measuring the surrounding rock pressure and the contact pressure between the lining and the surrounding rock generally involve placing earth pressure cells between the initial support and the surrounding rock, and between the initial support and the secondary lining. This often faces problems such as difficulty in placement, significant impact from concrete, easy damage, and inaccurate measurement data. This invention uses strain gauges on steel arch frames to obtain the surrounding rock pressure and the contact pressure between the lining and the surrounding rock pressure through certain conversions and data processing. The protective shell not only avoids the impact of concrete on the components but also protects the components and the connection points between the components and the wires, greatly improving the survival rate of the components. (4) Using a single strain gauge for measurement makes data processing more convenient and greatly reduces the use of earth pressure cells, effectively saving costs and manpower. Attached Figure Description

[0030] Figure 1Detailed diagram of the fixing device in the method of the present invention;

[0031] Figure 2 Arrangement diagram of the fixing device in the method of the present invention;

[0032] Figure 3 Detailed diagram and arrangement diagram of the strain gauge in the method of this invention;

[0033] Figure 4 The final arrangement diagram of the strain gauges in the method of this invention;

[0034] Figure 5 A schematic diagram of the basic unit for calculation and measurement in the method of this invention, where a represents the initial axial stress N of the support. x The basic unit for calculation and measurement, where b represents the initial support lateral stress σ. y The basic unit of computational measurement;

[0035] Figure 6 A diagram showing the arrangement of measurement points in the method of this invention;

[0036] Figure 7 This is a trend diagram of surrounding rock pressure and contact pressure between linings obtained by measuring using the present invention.

[0037] Figure 8 A trend diagram of surrounding rock pressure and contact pressure between linings measured by earth pressure cells for similar tunnels.

[0038] The meanings of the markings in the above figure are as follows: base 1, locking device 2, bolt 3, steel arch frame 4, steel pipe 5, axially arranged strain gauge 6, transversely arranged strain gauge 7, strain gauge 8, wire 9, protective shell 10, fixing device 11, initial support concrete 12. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. It should be noted that the following embodiments are merely illustrative examples of the present invention, and all equivalent substitutions made by those skilled in the art in accordance with the spirit of the present invention fall within the protection scope of the present invention.

[0040] Example

[0041] For methods of calculating and measuring the stress parameters of the initial support structure of a tunnel, please refer to [link / reference needed]. Figures 1 to 7 It includes the following steps:

[0042] S1. After tunnel excavation and frame erection, and before shotcreting, several measuring points are set on the web of the steel arch frame; such as... Figure 6As shown, five measurement points are set, located on the left arch waist, left arch shoulder, arch crown, right arch waist, and right arch shoulder of the steel arch frame web. Two strain gauges are arranged axially and laterally on both sides of the steel arch frame web at each measurement point. In this invention, the axial and lateral directions refer to the steel arch frame as the positioning object. The axially arranged strain gauge 6 and the laterally arranged strain gauge 7 are as follows: Figure 2 and Figure 3 As shown, the axially arranged strain gauge 6 is along the axial direction of the steel arch frame, while the transversely arranged strain gauge 7 is along the transverse direction of the steel arch frame. A protective shell needs to be installed on the strain gauge to isolate the strain gauge from the subsequent shotcrete. This avoids the influence of concrete on the strain gauge, thereby ensuring that the strain value measured by the strain gauge 8 changes to the axial or transverse strain of the steel arch frame 4 as much as possible.

[0043] The installation arrangement of the strain gauge is as follows: preparation of relevant components and auxiliary materials, including fixing device 11, protective shell 10, and integrated testing instrument; wherein, the raw materials of fixing device 11 and protective shell 10 are both austenitic stainless steel, which can be quickly water-cooled after welding. Water cooling can enhance the nucleation of austenitic structure and prevent chromium sensitization in the structure of fixing device 11 and protective shell 10, and avoid its formation of brittle phase; fixing device 11 includes two grooved bases 1, a bolted locking device 2, and steel pipes 5 with the same diameter as both ends of strain gauge 8;

[0044] Before the tunnel excavation and frame erection, the fixing device 11 needs to be assembled. The two ends of the steel pipe 5 are placed into the grooves of the two bases 1, ensuring that the two bases are as parallel as possible. Then, the locking device 2 is fastened and the bolts on the locking device 2 are tightened to fix the steel pipe 5. After the tunnel excavation and frame erection, and before spraying concrete, the two sets of installed fixing devices 11 are welded axially and laterally along the axis of the web of the steel arch to the axial area on both sides of the web of the steel arch. The welding quality is ensured so that the fixing device 11 is tightly connected to the steel arch and will not cause relative displacement or detachment. After welding, water is sprayed in time to cool down.

[0045] The strain gauge 8 used is a surface-type intelligent string strain gauge. After the fixing device cools down, loosen the bolts 3 of the locking device 2 on the bases 1 at both ends, take out the steel pipe 5, fix the strain gauge 8 laterally 10 and axially 11 on the fixing device 11 that has been welded to the steel arch frame, that is, fix both ends of the strain gauge in the grooves on the bases 1 at both ends, fasten the locking device 2, and tighten the bolts 3; and use strong adhesive to wrap the wire 9 on the strain gauge around and glue it to the side of the base. If the wire is not wrapped on the fixing device, the impact of the sprayed concrete or the gravity after spraying will pull on the wire, which can easily damage the connection between the wire and the strain gauge; after the other end of the wire 9 is passed out from the reserved hole of the protective shell 10, the protective shell 10 is wrapped around the strain gauge 8 and the wire 9 inside, and then the protective shell 10 is welded to the steel arch frame to ensure the welding quality, so that the protective shell 10 is tightly connected to the steel arch frame 4, and there will be no relative displacement or falling off. Water is sprayed in time to cool down and prevent the high temperature generated by welding from adversely affecting the strain gauge or damaging the wire.

[0046] S2. After guiding the conductor to the appropriate position, use the integrated testing instrument to zero the initial difference of the strain gauges, and record the initial readings of the two strain gauges arranged axially and laterally at each measurement point, denoted as U. x0 U y0 Subsequently, during the initial tunnel support period, the real-time readings of the axially arranged strain gauges at each measuring point were monitored at different times, denoted as U. x The real-time readings of the transversely arranged strain gauges at each measurement point were monitored at different times before the secondary lining was constructed, and denoted as U'. y The real-time readings of the transversely arranged strain gauges at each measurement point were monitored at different times after the secondary lining was installed, and denoted as U". y When the interaction between the surrounding rock pressure and the steel arch frame reaches equilibrium, the real-time readings of the strain gauges arranged laterally at each measuring point are denoted as U. y1 ;

[0047] S3. For specific actual tunnel projects, the types and models of various materials, the initial support thickness, the spacing of steel arch frames, and the elastic modulus of concrete and steel arch frames have all been determined; the axial stress N of the initial support is taken as the transverse cross-sectional area of ​​the initial support structure (steel arch frame spacing L × initial support thickness H). x The basic unit for calculation and measurement is the axial cross-sectional area of ​​the initial support structure (spacing of steel arches L × length B of the calculation unit) as the initial support transverse stress σ. y The basic unit for calculation and measurement is selected, with length B as the strain gauge length; it is assumed that the concrete spraying is uniform and the influence of other factors is ignored.

[0048] U based on step S2 x U x0 Data, due to ε gx =Ux -U x0 ε can be calculated gx Based on the principle of deformation compatibility, the axial strain value ε of the steel arch frame gx The strain value ε of the initial support concrete along the axis hx Approximately equal, take ε gx As ε hx The final result is used to calculate ε. hx ; will ε hx ε gx Substitute the initial support axial internal force N x The calculation formula is used to calculate the stress parameters of the initial support structure of the tunnel, specifically the axial internal force N of the initial support. x ;

[0049] Since σ=E×ε and N=σ×S, the internal force relationship along the initial support axis is N x =N hx +N gx Then N x =σ hx ×S hx +σ gx ×S gx =E hx ×ε hx ×S hx +E gx ×ε gx ×S gx That is, the initial support axial stress N x The calculation formula is:

[0050] N x =E hx ×ε hx ×S hx +E gx ×ε gx ×S gx

[0051] In the above formula, σ is stress, E is elastic modulus, ε is strain, S is area, and N is axial force; N hx For the initial support concrete axial force, N gx ε is the axial force of the steel arch frame; gx ε represents the axial strain value of the steel arch frame. hx σ represents the axial strain value of the initial support concrete. h For the internal forces of the initial support concrete, σ g E represents the internal forces within the steel arch frame. hx E represents the elastic modulus of the initial support concrete. gx The elastic modulus of the steel arch frame; such as Figure 5 As shown in (a), S h S is the transverse cross-sectional area of ​​the initial support concrete. gThis represents the transverse cross-sectional area of ​​the steel arch frame;

[0052] Based on the data U' obtained in step S2 y and U y0 The transverse strain ε of the steel arch frame under the action of surrounding rock pressure before the secondary lining is constructed is calculated. gy1 Based on the data U obtained from step S2 y and U y1 The transverse strain ε of the steel arch frame under the contact pressure between the linings after the secondary lining is constructed is calculated. gy2 ; where ε gy1 =U' y -U y0 , ε gy2 =U” y -U y1 ;

[0053] The ε calculated above gy1 ε gy2 Substitute the initial support lateral stress σ into the values ​​respectively. y The calculation formula allows us to calculate the initial lateral stress σ of the secondary lining before its construction. y1 And the initial lateral stress σ after the secondary lining is constructed y2 In the transverse direction of the steel arch, the equivalent formula for the modulus of elasticity is E. y =E hy +E gy ×A gy / A hy Based on the principle of deformation compatibility, then σ y =E y ×ε y Then the initial support lateral stress σ y The calculation formula is as follows:

[0054] σ y =(E hy +E gy ×A gy / A hy )×ε y ;

[0055] In the above formula, E y E is the equivalent elastic modulus. hy E represents the elastic modulus of the initial support concrete in the transverse direction. gy The modulus of elasticity in the transverse direction of the steel arch frame; such as Figure 5 (b), A gy Let A be the axial cross-sectional area of ​​the steel arch frame. hy ε is the axial cross-sectional area of ​​the initial support concrete; y The initial support lateral strain value; where ε y The value of is ε gy1At that time, the initial lateral stress σ of the secondary lining before its construction can be calculated. y1 ; where ε y The value of is ε gy2 At that time, the initial lateral stress σ of the secondary lining can be calculated. y2 .

[0056] In the transverse direction of the steel arch frame, due to its complex cross-sectional composition, the strength of the steel arch frame is distributed into the concrete using the equivalent elastic modulus method, effectively treating the initial support as a whole. Due to the special nature of tunnel support application, the secondary lining is often only constructed after the arch crown settlement has stabilized (i.e., when the contact pressure between the initial support and the surrounding rock has stabilized). Since there are materials such as waterproof membrane and woven fabric between the initial support and the secondary lining, only radial (i.e., transverse) contact pressure is transmitted between the linings within the tunnel. That is, before the secondary lining is constructed, the change in the transverse value of the initial support is mainly caused by the surrounding rock pressure; after the secondary lining is constructed, the change in the transverse value of the initial support is mainly caused by the contact pressure between the linings. In other words, the transverse axial force of the initial support originates from the pressure of the surrounding rock and the contact pressure of the secondary lining. Before the secondary lining is constructed, the transverse stress σ of the initial support... y The change is due to the surrounding rock pressure σ w This causes the surrounding rock pressure σ w It can be approximated as equal to the initial support lateral stress σ y Take σ y1 As σ w The final result is the calculation of the surrounding rock pressure σ before the secondary lining is constructed. w Then σ w =(E hy +E gy ×A gy / A hy )×ε gy1 After the secondary lining is installed, the contact pressure σ between the linings c It can be approximated as equal to the initial support lateral stress σ y Take σ y2 As σ c The final result is the calculated contact pressure σ between the linings after the secondary lining is installed. c Then σ c =(E hy +E gy ×A gy / A hy )×ε gy2 ;

[0057] S4. Using the time of tunnel secondary lining construction as the dividing line, the initial support circumferential axial force σ at each measurement point at different times is measured. x and surrounding rock pressure σ w Contact pressure σ between the lining and the lining c Monitor the values ​​and trends of change; such as Figure 7 As shown, the trends of the surrounding rock pressure and the contact pressure between the lining sections measured using this invention are respectively consistent with... Figure 8 Similar to the trend of changes in surrounding rock pressure and lining contact pressure monitored by setting up earth pressure cells in tunnel studies, it can be seen that the method of the present invention is accurate and feasible for calculating and measuring the stress parameters of the initial support structure of the tunnel, namely surrounding rock pressure and lining contact pressure.

Claims

1. A method for calculating and measuring the stress parameters of the initial support structure of a tunnel, characterized in that... Includes the following steps: S1. After the tunnel excavation and frame erection and before the shotcrete, several measuring points are set on the web of the steel arch frame. Two strain gauges are arranged axially and laterally on both sides of the axial area of ​​the web of the steel arch frame at each measuring point. S2. Zero the initial difference of the strain gauges and record the initial readings of the two strain gauges arranged axially and laterally at each measurement point, respectively denoted as: U x0 , U y0 ; Subsequently, during the initial tunnel support phase, real-time readings of two strain gauges arranged axially and laterally at each measurement point were monitored at different times, and recorded as follows: U x The real-time readings of the transversely arranged strain gauges at each measurement point were monitored at different times before the secondary lining was constructed, and recorded as follows: U’ y Monitor the real-time readings of the transversely arranged strain gauges at each measurement point at different times after the secondary lining is constructed, and record them as follows: U’’ y When the interaction between the surrounding rock pressure and the steel arch frame reaches equilibrium, the real-time readings of the strain gauges arranged laterally at each measuring point are recorded as follows: U y1 ; S3. Based on the data measured in step S2 U x and U x0 Calculate the axial strain value of the steel arch frame. ɛ gx Using data ɛ gx Calculate the initial circumferential axial force of the support at each measurement point at different times. N x ; Initial support circumferential axial force N x The calculation method is as follows: Based on the measurement in step S2 U x and U x0 ,because ɛ gx = U x - U x0 Calculate ɛ gx ;based on Deformation compatibility principle, axial strain value of steel arch frame ɛ gx The strain value of the initial support concrete along the axis ɛ hx Approximately equal, take ɛ gx As ɛ hx The final result is then calculated. ɛ hx The above calculation results ɛ hx ɛ gx Substitute the initial support circumferential axial force N x The calculation formula is used to calculate the initial support circumferential axial force. N x ; Initial support circumferential axial force N x The calculation formula is: N x = E hx ×ɛ hx × S hx + E gx ×ɛ gx × S gx ; In the above formula, ɛ gx This represents the axial strain value of the steel arch frame. ɛ hx This represents the axial strain value of the initial support concrete. E hx The elastic modulus of the initial support concrete. E gx The elastic modulus of the steel arch frame; S h Let be the transverse cross-sectional area of ​​the initial support concrete. S g This represents the transverse cross-sectional area of ​​the steel arch frame; Based on the data obtained from step S2 U’ y and U y0 The transverse strain value of the steel arch frame under the action of surrounding rock pressure before the secondary lining is constructed is calculated. ɛ gy1 Using data ɛ gy1 Calculate the surrounding rock pressure at each measurement point at different times. σ w : Based on the data obtained from step S2 U’’ y and U y1 The transverse strain value of the steel arch frame under the contact pressure between the linings after the secondary lining is constructed is calculated. ɛ gy2 ， Using data ɛ gy2 Calculate the interlining contact pressure at each measurement point at different times. σ c : S4. Using the time of tunnel secondary lining construction as the dividing line, the initial support circumferential axial force at each measurement point at different times was measured. N x and surrounding rock pressure σ w Contact pressure between lining σ c We monitor the values ​​and trends of these values.

2. The method for calculating and measuring the stress parameters of the initial support structure of a tunnel as described in claim 1, characterized in that, In step S1, the number of measurement points is set to 5, which are located on the left arch waist, left arch shoulder, arch top, right arch waist and right arch shoulder of the steel arch frame web.

3. The method for calculating and measuring the stress parameters of the initial support structure of a tunnel as described in claim 1, characterized in that, In step S1, a protective shell is installed on the strain gauge to separate the strain gauge from the subsequent shotcrete.

4. The method for calculating and measuring the stress parameters of the initial support structure of a tunnel as described in claim 3, characterized in that, Several of the measurement points are installed on the web of the steel arch frame by a fixing device, which includes a base, a locking device with bolts, and a steel pipe with the same diameter as both ends of the strain gauge.

5. The method for calculating and measuring the stress parameters of the initial support structure of a tunnel as described in claim 4, characterized in that, Both the fixing device and the protective shell are made of austenitic stainless steel, and the fixing device and the protective shell are quickly water-cooled after welding.

6. The method for calculating and measuring the stress parameters of the initial support structure of a tunnel as described in claim 1, characterized in that, The strain gauge used is a surface-type intelligent string strain gauge.

7. The method for calculating and measuring the stress parameters of the initial support structure of a tunnel as described in claim 1, characterized in that, In step S3, the surrounding rock pressure σ w Contact pressure between masonry and brickwork σ c The specific calculation method is as follows: Based on the data obtained from step S2 U’ y and U y0 The transverse strain value of the steel arch frame under the action of surrounding rock pressure before the secondary lining is constructed is calculated. ɛ gy1 Based on the data obtained from step S2 U’’ y and U y1 The transverse strain value of the steel arch frame under the contact pressure between the linings after the secondary lining is constructed is calculated. ɛ gy2 ;in ɛ gy1 =U’ y - U y0 , ɛ gy2 =U’’ y - U y1 ; The above calculations ɛ gy1 , ɛ gy2 Substitute the initial support lateral stress respectively σ y The calculation formula allows us to calculate the initial lateral stress of the secondary lining before its construction. σ y1 Lateral stress in the initial support after secondary lining construction σ y2 ; In the transverse direction of the steel arch frame, due to the complex cross-sectional composition, the strength of the steel arch frame is distributed into the concrete using the equivalent elastic modulus method, treating the initial support as a whole. Before the secondary lining is constructed, the transverse stress of the initial support is... σ y Changes due to surrounding rock pressure σ w Caused by surrounding rock pressure σ w Approximately equal to the initial support lateral stress σ y ,Pick σ y1 As σ w The final result is the calculation of the surrounding rock pressure before the secondary lining is constructed. σ w After the secondary lining is installed, the contact pressure between the linings... σ c Approximately equal to the initial support lateral stress σ y ,Pick σ y2 As σ c The final result is the calculation of the contact pressure between the linings after the secondary lining is installed. σ c .

8. The method for calculating and measuring the stress parameters of the initial support structure of a tunnel as described in claim 7, characterized in that, The initial support lateral stress σ y The calculation formula is: σ y =（ E hy + E gy × A gy / A hy ）× ɛ y ； In the above formula, E hy The elastic modulus of the initial support concrete in the transverse direction. E gy The modulus of elasticity in the transverse direction of the steel arch frame; A gy Let be the axial cross-sectional area of ​​the steel arch frame. A hy This represents the axial cross-sectional area of ​​the initial support concrete. ɛ y The initial support lateral strain value; where when ɛ y The value is ɛ gy1 At that time, the initial transverse stress of the support before the secondary lining can be calculated. σ y1 ; among them when ɛ y The value is ɛ gy2 At that time, the initial transverse stress of the secondary lining can be calculated. σ y2 .

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