An open type TBM soft rock deformation tunnel section arch protection construction timing decision method and system

Abstract

This invention provides a method and system for determining the timing of arch reinforcement construction in soft rock deformation sections of open-face TBM tunnels. The method includes: obtaining a first deformation threshold for a typical steel arch within the tunnel section entering its ultimate bearing capacity; monitoring the deformation of the steel arch to be tested within the tunnel section; and determining whether arch reinforcement is needed at the steel arch based on the first deformation threshold and the monitored deformation values. This invention establishes a decision-making mechanism for arch reinforcement based on steel arch deformation monitoring values. It determines whether reinforcement is needed by analyzing the relationship between the steel support deformation monitoring values ​​and the deformation threshold, effectively balancing the conflict between TBM tunneling and support, and improving TBM tunneling efficiency. The decision criteria are simple and clear, allowing for precise determination of reinforcement timing and avoiding problems such as increased construction risks, increased investment, and extended construction periods caused by subsequent arch replacement.

Description

Technical Field

[0001] This invention relates to the field of open-face TBM tunnel support technology, and in particular to a method and system for determining the timing of arch support construction in soft rock deformation sections of open-face TBMs. Background Technology

[0002] Open-face TBMs (tunnel boring machines for hard rock) offer advantages such as efficient continuous tunneling, high-quality tunneling, and strong turning capabilities. However, when operating in soft rock formations, the conflict between tunneling and support becomes particularly pronounced. Insufficient support can easily lead to deformation and confinement of the surrounding rock, while excessive support severely reduces tunneling efficiency. Unlike drill-and-blast methods, open-face TBMs cannot accommodate sufficient deformation allowances, making them prone to deformation and confinement of the surrounding rock under high ground stress. This can result in extensive arch replacement work, impacting tunnel construction schedules and increasing construction costs.

[0003] After an open-face TBM tunnels through and initial support is applied, if the tunnel deformation rate is too rapid, reinforcement can be implemented by adding steel arch supports and installing additional anchor bolts to suppress further deformation and prevent the TBM from getting stuck. However, currently, the timing of arch support reinforcement mainly relies on the experience and judgment of on-site engineers, lacking scientific and quantitative decision-making basis. Two unfavorable situations often occur: first, arch support is applied when deformation and support load-bearing conditions are still within a controllable range, resulting in waste of materials and construction time; second, reinforcement is applied only when the initial support shotcrete shows obvious cracks, spalling, or even steel arch frame twisting and instability. At this point, the original initial support has already failed, the surrounding rock is excessively loose, the optimal reinforcement time has been missed, the reinforcement effect is much less effective, and the TBM is already at high risk of getting stuck.

[0004] While current technologies widely employ tunnel perimeter convergence monitoring, relying solely on total deformation for empirical judgment fails to reflect the inherent bearing capacity of the support structure. This is particularly problematic in geologically complex and anisotropic strata, where theoretical calculations deviate significantly from actual conditions, further complicating decision-making.

[0005] Therefore, there is an urgent need for a method and system for determining the timing of arch support construction in open-type TBM soft rock deformation tunnel sections, so as to accurately and efficiently determine the timing of arch support construction, thereby intervening in a timely manner at key nodes in the development of surrounding rock deformation and avoiding arch support construction too early or too late. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for determining the timing of arch support construction in open TBM soft rock deformation tunnel sections, in order to solve the problem of being unable to accurately and efficiently determine the timing of arch support construction, resulting in arch support construction being carried out too early or too late.

[0007] To address the aforementioned technical problems, this invention provides a method for determining the timing of arch support construction in open-type TBM soft rock deformation tunnel sections, comprising: obtaining a first deformation threshold for a typical steel arch frame entering its bearing limit state within the tunnel section; monitoring the deformation monitoring value of the steel arch frame to be tested within the tunnel section; and determining whether arch support construction is necessary at the steel arch frame to be tested based on the first deformation threshold and the monitored deformation monitoring value.

[0008] Optionally, it also includes: designating the steel arch frames to be tested that require arch protection as the first steel arch frame to be tested, and designating the steel arch frames that do not require arch protection as the second steel arch frame to be tested; determining whether the deformation in the tunnel section tends to converge after the first steel arch frame to be tested is protected; if it does not tend to converge, determining whether arch protection needs to be applied at the second steel arch frame to be tested based on the second deformation threshold and the monitored deformation value, wherein the second deformation threshold is the value after the first deformation threshold is reduced.

[0009] Optionally, obtaining the first deformation threshold of a typical steel arch frame entering the ultimate bearing state within a tunnel segment includes: determining the nature of the surrounding rock of the tunnel segment; if the surrounding rock is isotropic or approximately isotropic, then calculating the first deformation threshold of a typical steel arch frame entering the ultimate bearing state based on theoretical formulas; if the surrounding rock of the tunnel segment is anisotropic rock mass, then obtaining the first deformation threshold of a typical steel arch frame in a tunnel segment with the same lithology and stratigraphic structure by calibrating typical steel arch frames in the same lithology and stratigraphic structure.

[0010] Optionally, the threshold for the first deformation of a typical steel arch frame in a tunnel section to enter its ultimate bearing state includes: Obtain the material of the steel arch frame and the upper yield strain of the material ∈ ys and the yield plateau termination strain ∈ ye ; Calculate the circumferential perimeter L of the tunnel profile under uniform pressure as the steel arch gradually reaches the initial yield strain and the final yield plateau strain state. ys and L ye (In this state, the steel support is under pressure everywhere and the stress is evenly distributed.) Calculate the radial deformation δ of the steel arch frame under uniform pressure as it gradually reaches the initial yield strain and the final strain state of the yield plateau. ys and δ ye ; The radial deformation of the steel support caused by the joint sealing of the steel arch frame is calculated as δ. j ; Calculate the initial yield warning deformation of the steel arch frame U ew and critical early warning deformation of bearing capacity U sh ; The first deformation threshold includes the early warning deformation of the steel arch frame yielding initiation. Uew and critical early warning deformation of bearing capacity U sh .

[0011] Optional, L ys and L ye Calculated using the following formula: .

[0012] Optional, δ ys and δ ye Calculated using the following formula: .

[0013] Optionally, δj is calculated using the following formula: .

[0014] Optional, U ew and U sh Calculated using the following formula: .

[0015] Optionally, by calibrating typical steel arches of tunnel sections with similar lithology and stratigraphic structure, the first deformation threshold of typical steel arches of such tunnel sections with similar lithology and stratigraphic structure can be obtained, including: Multiple steel plate gauges were installed on a typical steel arch frame in a tunnel section with similar lithology and stratigraphic structure. Simultaneously, the tunnel perimeter convergence at the cross-section where the steel arch frame was located was monitored. When the strain data from the steel plate gauges showed that the upper yield point of the steel in the steel arch frame was reached, the corresponding tunnel perimeter convergence displacement value was recorded. This tunnel perimeter convergence displacement value was calibrated as the initial yield warning deformation of the steel support in a tunnel section with similar lithology and stratigraphic structure. U ew , will 6 U ew The critical early warning deformation of the steel support bearing capacity of the tunnel section with the same lithology and strata structure is calibrated. U sh The first deformation threshold includes the early warning deformation of the steel arch frame yielding initiation. U ew and critical early warning deformation of bearing capacity U sh .

[0016] Optionally, the decision-making mechanism for the initial support of the arch reinforcement based on the deformation threshold includes: Determination of steel arch frame deformation monitoring values U Is it greater than U ew :like U<Uew If so, there is no need to add protective arches; if U>U ew If so, proceed to the next step; Determine whether V has been present for 3 consecutive days during the monitoring process. U If the diameter is greater than 2mm / d, then construct a protective arch; otherwise, determine the appropriate action. U Is it greater than U sh ,like U>U sh Then construct protective arches, if U ≤ U sh Then there is no need to add protective arches, and the deformation monitoring values ​​of the steel arch frame are returned for judgment. U Is it greater than U ew This step.

[0017] The present invention also provides a system for determining the timing of arch support construction using the above-mentioned method for determining the timing of arch support construction in open-type TBM soft rock deformation tunnel sections, comprising: an acquisition module for acquiring a first deformation threshold value for a typical steel arch frame entering the bearing limit state within the tunnel section; a monitoring module for monitoring the deformation monitoring value of the steel arch frame to be tested within the tunnel section; and a judgment module for determining whether arch support construction is necessary at the steel arch frame to be tested based on the first deformation threshold value and the monitored deformation monitoring value.

[0018] The present invention provides a method and system for determining the timing of arch support construction in open-type TBM soft rock deformation tunnel sections, which has the following beneficial effects: First, a decision-making mechanism for arch reinforcement support based on steel arch deformation monitoring values ​​was established. This mechanism determines whether reinforcement is necessary by analyzing the relationship between steel support deformation monitoring values ​​and deformation thresholds, effectively balancing the conflict between TBM tunneling and support, and improving TBM tunneling efficiency. The decision-making criteria are simple and clear, allowing for precise determination of reinforcement timing and avoiding problems such as increased construction risks, higher investment, and extended construction periods caused by subsequent arch replacement.

[0019] Secondly, it avoids the efficiency loss and material waste caused by premature support, ensures the continuity of TBM tunneling, and effectively improves the overall construction efficiency.

[0020] Furthermore, by inferring the structural stress state from the macroscopic deformation of the steel arch frame, the inflection point (yield initiation) of the load-bearing capacity change can be accurately captured before the macroscopic deformation becomes uncontrollable, allowing for timely intervention and proactive control, thus avoiding the risk of arch frame instability and TBM jamming.

[0021] Then, the displacement monitoring values ​​that are readily available on site are used for early warning. Construction personnel do not need to understand complex mechanical principles; they can make decisions simply by comparing the monitoring data with the displacement warning values. This method is convenient to use and greatly improves the response speed. Attached Figure Description

[0022] Picture 1 This is a flowchart of the method for deciding the timing of arch support construction in open-type TBM soft rock deformation tunnel sections according to an embodiment of the present invention; Picture 2 This is the pull-out test curve of Q235 low carbon steel; Picture 3 This is a schematic diagram of the steel plate and displacement monitoring point layout in an embodiment of the present invention; Picture 4 This is a schematic diagram of deformation monitoring threshold calibration in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] refer to Picture 1 , Picture 1 This is a flowchart of a method for determining the timing of arch support construction in an open-face TBM soft rock deformation tunnel section according to an embodiment of the present invention. This embodiment provides a method for determining the timing of arch support construction in an open-face TBM soft rock deformation tunnel section, including: Obtain the first deformation threshold of a typical steel arch frame entering the ultimate bearing state within the tunnel section; The deformation monitoring values ​​of the steel arch frame to be tested within the monitoring tunnel section; and The determination of whether arch protection needs to be installed at the steel arch frame to be tested is based on the first deformation threshold and the monitored deformation value.

[0030] This embodiment establishes a decision-making mechanism for arch reinforcement support based on steel arch deformation monitoring values. It determines whether to reinforce the support by analyzing the relationship between the steel support deformation monitoring values ​​and deformation thresholds, effectively balancing the conflict between TBM tunneling and support, and improving TBM tunneling efficiency. The decision criteria are simple and clear, allowing for precise determination of reinforcement timing and avoiding problems such as increased construction risks, increased investment, and extended construction periods caused by subsequent arch replacement.

[0031] Among them, the threshold for obtaining the first deformation amount when a typical steel arch frame in the tunnel section enters the ultimate bearing state includes: To determine the properties of the surrounding rock of the tunnel section, if the surrounding rock is isotropic or nearly isotropic, the first deformation threshold of the typical steel arch frame of the tunnel section entering the ultimate bearing state is calculated based on theoretical formulas. If the surrounding rock of the tunnel section is anisotropic, the first deformation threshold of the typical steel arch frame of the tunnel section with the same lithology and stratum structure is obtained by calibrating the typical steel arch frames of the tunnel section with the same lithology and stratum structure.

[0032] The threshold for the first deformation of a typical steel arch frame entering its ultimate bearing capacity in a tunnel section includes: Obtain the material of the steel arch frame and the upper yield strain of the material ∈ ys and the yield plateau termination strain ∈ ye ; Calculate the circumferential perimeter L of the tunnel profile under uniform pressure as the steel arch gradually reaches the initial yield strain and the final yield plateau strain state. ys and Lye (In this state, the steel support is under pressure everywhere and the stress is evenly distributed.) Calculate the radial deformation δ of the steel arch frame under uniform pressure as it gradually reaches the initial yield strain and the final strain state of the yield plateau. ys and δ ye ; The radial deformation of the steel support caused by the joint sealing of the steel arch frame is calculated as δ. j ; Calculate the initial yield warning deformation of the steel arch frame U ew and critical early warning deformation of bearing capacity U sh ; The first deformation threshold includes the early warning deformation of the steel arch frame yielding initiation. U ew and critical early warning deformation of bearing capacity U sh .

[0033] refer to Picture 2 , Picture 2 These are the pull-out test curves for Q235 low-carbon steel. Q235 low-carbon steel is commonly used in engineering for steel arch frames. Picture 2 It can be seen that the main tensile deformation parameters of Q235 are: upper yield point strain ∈ ys =0.16%, yield plateau termination strain ∈ ye =1.26%, with an ultimate strain of 25%. Theoretically, steel components fail after reaching their ultimate strain, but engineering requirements dictate that the allowable strain should have a sufficient safety margin to control the load-bearing state of the steel component before it enters the strengthening stage. This embodiment uses the yield limit strain on the steel component as a yield initiation warning and the yield plateau termination strain as a critical load-bearing capacity warning. Based on this, a threshold and control standard for the deformation of the steel support are proposed.

[0034] Among them, L ys and L ye Calculated using the following formula: Where, ∈ ys For the upper yield point strain, ∈ ye For the yield plateau termination strain, L ys L is the circumferential perimeter of the tunnel profile at the initial yield strain state. ye The circumferential perimeter of the tunnel profile under the yielding plateau termination strain state.

[0035] δ ys and δ ye Calculated using the following formula: Where, δys δ represents the radial deformation of the steel arch as it gradually reaches its initial yield strain state under uniform pressure. ye This refers to the radial deformation of the steel arch frame as it gradually reaches the yield plateau termination strain state under uniform pressure load.

[0036] Where, δ j Calculated using the following formula: The steel arch frame is assembled in sections, with connecting plates and bolts used to connect the sections. Gaps exist between the connecting plates, and they do not provide stiffness before the joints close during the initial loading phase, resulting in additional deformation increments in the support. Assume the steel arch frame is assembled in n sections, with each joint width being B. j The radial deformation of the steel support caused by the joint sealing is δ. j .

[0037] U ew and U sh Calculated using the following formula: in, U ew This refers to the initial early warning deformation for the yielding of the steel support. U sh This is the critical early warning deformation amount for bearing capacity.

[0038] For anisotropic strata, by calibrating typical steel arches of tunnel sections with similar lithology and stratigraphic structure, the first deformation threshold of typical steel arches of tunnel sections with similar lithology and stratigraphic structure is obtained, including: Multiple steel plate gauges were installed on a typical steel arch frame in a tunnel section with similar lithology and stratigraphic structure. Simultaneously, the tunnel perimeter convergence at the cross-section where the steel arch frame was located was monitored. When the strain data from the steel plate gauges showed that the upper yield point of the steel in the steel arch frame was reached, the corresponding tunnel perimeter convergence displacement value was recorded. This tunnel perimeter convergence displacement value was calibrated as the initial yield warning deformation of the steel support in a tunnel section with similar lithology and stratigraphic structure. U ew , will 6 U ew The critical early warning deformation of the steel support bearing capacity of the tunnel section with the same lithology and strata structure is calibrated. U sh The first deformation threshold includes the early warning deformation of the steel arch frame yielding initiation. U ew and critical early warning deformation of bearing capacity U sh .

[0039] Preferably, the steel plate is arranged at the critical stress sections of the steel arch frame, such as the arch crown and arch waist.

[0040] Among them, a typical steel arch frame can be the first steel arch frame constructed in a tunnel section with the same lithology and strata structure.

[0041] In anisotropic strata, tunnel deformation is uneven, so the placement of steel plate gauges should vary in density. Increased monitoring density should be applied to key areas with significant deformation, such as the tunnel crown, fault outcrops, and locations perpendicular to the bedding plane. Two to three sets of steel plate gauges can be placed at these locations. For example, refer to... Picture 3 , Picture 3 This is a schematic diagram of the steel plate and displacement monitoring point layout in an embodiment of the present invention.

[0042] In the process of calibrating typical steel arch frames in tunnel sections with similar lithology and stratigraphic structure to obtain the first deformation threshold of typical steel arch frames in such tunnel sections with similar lithology and stratigraphic structure, synchronous data of steel arch frame strain ϵ and tunnel perimeter convergence displacement U are continuously collected. When the strain data shows that the upper yield point of the steel is reached, the corresponding tunnel perimeter convergence displacement value is recorded, and this value is directly defined as the measured "steel support yield initiation warning deformation" under the geological conditions. U ew For example, refer to Picture 4 , Picture 4 This is a schematic diagram of deformation monitoring threshold calibration in an embodiment of the present invention. Considering the limited measurement range of the steel plate (the measurement range of domestic steel plates is generally 3000με), it is impossible to capture the yield plateau termination strain (1.26%) of the steel. According to the characteristics of the steel, the yield plateau termination strain is generally about 7 to 8 times the upper yield point strain. Conservatively, the critical warning deformation of the bearing capacity is taken as 6 times the yield initiation warning deformation, that is: U sh =6 U ew This value is defined as the measured "critical early warning deformation of bearing capacity" under this geological condition. U sh ".

[0043] It should be noted that the deformation threshold calibrated on-site is only applicable to tunnel sections with the same lithology and stratigraphic structure. When the geological conditions to be revealed change, steel plate gauges need to be re-installed for calibration.

[0044] Among them, determining whether arch protection is needed based on the relationship between the calculated deformation threshold of the steel arch frame and the monitored deformation values ​​of the steel arch frame includes: a. Determine the deformation monitoring values ​​of the steel arch frame U Is it greater than U ew :like U<U ewIf the steel arch frame is in the elastic deformation range, the risk of deformation is small, and no additional protective arch is needed. U>U ew The system enters a yellow alert state, indicating that the steel arch frame has entered the yielding stage and poses a significant risk of deformation. However, the overall structural deformation is controllable and the structure still has load-bearing capacity. In this state, no additional protective arches are needed, but the frequency of monitoring the deformation rate of the steel arch frame should be increased.

[0045] b, in U>U ew Based on this, the deformation rate of the steel arch frame is continuously monitored, such as V for 3 consecutive days during the monitoring process. U If the deformation rate is greater than 2 mm / d, the red alert stage is entered. During this stage, the deformation of the steel supports continues and has not converged, requiring timely installation of arch protection. If the deformation rate V... U If the value is less than the limit, it proves that the deformation of the steel support is still controllable. Whether or not to install a protective arch needs to be determined in conjunction with the total deformation of the steel support.

[0046] c, in U>U ew And the deformation rate V U If the value is less than the limit, monitor the cumulative deformation of the steel support. U>U sh Then a red alert is issued, indicating that the plastic margin of the steel support has been exhausted and arch protection needs to be installed in a timely manner.

[0047] The method for determining the timing of arch support construction in open-face TBM soft rock deformation tunnel sections also includes: The steel arch frames to be tested that require arch protection are designated as the first steel arch frame to be tested, and those that do not require arch protection are designated as the second steel arch frame to be tested. After the first steel arch frame to be tested is protected, it is determined whether the deformation in the tunnel section tends to converge. If it does not converge, it is determined whether the second steel arch frame to be tested needs to be protected based on the second deformation threshold and the monitored deformation value. The second deformation threshold is the value after the first deformation threshold is reduced.

[0048] Since the second deformation threshold is the value after reducing the first deformation threshold, the timing of the arch support construction of the second steel arch frame to be tested is more stringent. The deformation threshold can be adjusted according to the actual situation to make the judgment of the timing of the arch frame construction more accurate.

[0049] The method for determining the timing of arch protection construction in open-type TBM soft rock deformation tunnel sections also includes: determining whether the deformation in the tunnel section tends to converge after the first steel arch frame to be tested is constructed; if it does not converge, then additional anchor bolts are installed at the first steel arch frame to be tested.

[0050] Specifically, based on whether the deformation rate within the tunnel section is greater than 0.2 mm / d, it is determined whether the deformation within the tunnel section tends to converge after the first steel arch frame to be tested is installed as a protective arch. If the deformation rate within the tunnel section is greater than 0.2 mm / d, it does not tend to converge; if the deformation rate within the tunnel section is less than or equal to 0.2 mm / d, it tends to converge.

[0051] The second deformation threshold is the value after reducing the first deformation threshold; that is, the second deformation threshold includes the reduced yield initiation warning deformation of the steel arch frame. U ew and critical early warning deformation of bearing capacity U sh .

[0052] For example, the early warning deformation of the yielding start of the steel arch frame. U ew The reduction is 15%, and the critical early warning deformation of the bearing capacity. U sh The reduction is 30%.

[0053] This embodiment also provides a system for determining the timing of construction using the open-type TBM soft rock deformation tunnel arch construction timing decision method described in the above embodiments, including: The acquisition module is used to acquire the first deformation threshold of a typical steel arch frame entering the ultimate bearing state within the tunnel section; The monitoring module is used to monitor the deformation values ​​of the steel arch frame under test within the tunnel section; and The judgment module is used to determine whether arch protection needs to be installed at the steel arch frame to be tested based on the first deformation threshold and the monitored deformation value.

[0054] The acquisition module includes: a lithology judgment module, a calculation module, and a calibration module; the lithology judgment module is used to judge the properties of the surrounding rock; the calculation module is used to calculate the first deformation threshold of a typical steel arch frame entering the bearing limit state of a tunnel section based on theoretical formulas when the lithology is isotropic or approximately isotropic; the calibration module is used to obtain the first deformation threshold of a typical steel arch frame of a tunnel section with the same lithology and stratigraphic structure by calibrating the typical steel arch frames of the tunnel section with the same lithology and stratigraphic structure when the lithology is anisotropic.

[0055] In the above embodiments, the steel arch frame can be an H-beam.

[0056] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. An open TBM soft rock deformation tunnel section arch protection construction timing decision method, characterized in that, The method comprises: obtaining a first deformation threshold of a typical steel arch entering a bearing limit state in a tunnel section; monitoring a deformation monitoring value of a steel arch to be tested in the tunnel section; and judging whether the steel arch to be tested needs to be protected according to the first deformation threshold and the monitored deformation monitoring value. The method further comprises:

2. The open TBM soft rock deformation tunnel segment arch protection construction timing decision method of claim 1, characterized in that, marking the steel arch to be tested needing protection as a first steel arch to be tested, and marking the steel arch not needing protection as a second steel arch to be tested; judging whether the deformation in the tunnel section tends to converge after the first steel arch to be tested is protected, and if not, judging whether the second steel arch to be tested needs to be protected according to a second deformation threshold and the monitored deformation monitoring value, wherein the second deformation threshold is a reduced value of the first deformation threshold. The method of obtaining the first deformation threshold of the typical steel arch entering the bearing limit state in the tunnel section comprises:

3. The open TBM soft rock deformation tunnel segment arch protection construction timing decision method of claim 1, wherein, judging the surrounding rock properties of the tunnel section, and if the surrounding rock is isotropic or approximately isotropic, calculating the first deformation threshold of the typical steel arch entering the bearing limit state in the tunnel section based on a theoretical formula, and if the surrounding rock of the tunnel section is anisotropic rock mass, calibrating the typical steel arch of the tunnel section with the same rock properties and stratum structure to obtain the first deformation threshold of the typical steel arch of the tunnel section with the same rock properties and stratum structure. The method of calculating the first deformation threshold of the typical steel arch entering the bearing limit state in the tunnel section comprises:

4. The open TBM soft rock deformation tunnel segment arch protection construction timing decision method of claim 3, characterized in that, 6. The method of claim 5, wherein Obtain the material of the steel arch and obtain the upper yield point strain ε ys and the yield plateau termination strain ε ye ; The tunnel contour circumferential length L under gradually reaching the initial yielding strain and the yielding platform termination strain state of the steel arch under the uniform pressure load is calculated ys and L ye (the steel support is compressed everywhere and the stress is uniformly distributed in this state); The radial deformation δ of the steel arch is calculated under the uniform pressure load gradually reaching the initial yield strain and the termination strain state of the yield platform ys and δ ye ; The radial deformation amount of the steel support caused by the joint closure of the steel arch is δ j ; Calculating the yield initiation pre-warning deformation of steel arches U ew and the critical pre-warning deformation of bearing capacity U sh ; The first deformation threshold value includes a steel arch support yield starting early warning deformation value U ew And a bearing capacity critical early warning deformation value U sh .

5. The open TBM soft rock deformation tunnel segment arch protection construction timing decision method of claim 4, characterized in that, L ys and L ye By the following formula: 。 is calculated by the following formula: delta ys and delta ye By the formula: 。 7. The open TBM soft rock deformation tunnel segment arch protection construction timing decision method of claim 6, wherein, The method of calibrating the typical steel arch of the tunnel section with the same rock properties and stratum structure to obtain the first deformation threshold of the typical steel arch of the tunnel section with the same rock properties and stratum structure comprises: 。 8. The open TBM soft rock deformation tunnel segment arch protection construction timing decision method of claim 7, wherein, U ew and U sh by the formula: 。 9. The open TBM soft rock deformation tunnel segment arch protection construction timing decision method of claim 3, wherein, The method of establishing a decision mechanism of initial support of arch protection reinforcement according to the deformation threshold comprises: The multiple steel plate gauges are arranged on a typical steel arch of a tunnel section with equal lithology and stratum structure, and the convergence of the tunnel section is monitored; when the strain data of the steel plate gauges reach the upper yield point of the steel material of the steel arch, the corresponding tunnel convergence displacement value at this time is recorded, and the tunnel convergence displacement value is calibrated as the steel support yield starting early warning deformation of the tunnel section with equal lithology and stratum structure U ew The 6 U ew The steel support bearing capacity critical early warning deformation of the tunnel section with equal lithology and stratum structure is calibrated U sh The first deformation threshold includes the steel arch yield starting early warning deformation U ew And the bearing capacity critical early warning deformation U sh .

10. The open TBM soft rock deformation tunnel segment arch protection construction timing decision method of claim 3 or 9, characterized in that, U < U Determination of steel arch frame deformation monitoring values U Is it greater than U ew :like U > U ew If so, there is no need to add protective arches; if U > U ew If so, proceed to the next step; whether V U > 2 mm / d for 3 consecutive days in the monitoring process, if yes, make arch protection; if no, judge U whether greater than U sh , if The method comprises: sh , make arch protection, if U ≤ U sh , no need to add arch protection, and return to judge steel arch deformation monitoring value U whether greater than U ew This step.

11. A system for making construction timing decisions using the open TBM soft rock deformation tunnel segment arch protection construction timing decision method according to any one of claims 1-10, characterized in that, an obtaining module configured to obtain a first deformation threshold of a typical steel arch entering a bearing limit state in a tunnel section; a monitoring module configured to monitor a deformation monitoring value of a steel arch to be tested in the tunnel section; and a judging module configured to judge whether the steel arch to be tested needs to be protected according to the first deformation threshold and the monitored deformation monitoring value. ​ ​

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