Tunnel construction management method and construction management system

Abstract

To provide a tunnel construction management method and construction management system based on management reference values that can evaluate the soundness of shoring.SOLUTION: A tunnel construction management method that performs construction management based on the amount of displacement of a shoring when constructing a tunnel by repeatedly excavating the tunnel and installing the shoring comprises a step A of setting the allowable strain at the time of damage to the shoring from multiple tunnel construction examples where damage to the shoring has been confirmed, a step B of setting the control standard value for the shoring by multiplying the allowable strain by the excavation radius of the tunnel to be controlled, a step C of measuring a displacement value regarding a displacement amount as the tunnel is excavated, and a step D of determining the suitability of the shoring by comparing control standard values and measured values.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to a tunnel construction management method and a construction management system. [Background technology]

[0002] In the construction of mountain tunnels, it is common to carry out underground measurements to grasp the characteristics (or condition, behavior, etc.) of the ground, such as visually observing the tunnel face and measuring the deformation or stress state of the supports and ground. Control standards for underground displacement (or support displacement) are set in advance, and the measured values ​​are compared with the control standards to determine whether the rigidity and strength of the current support is adequate and whether additional measures are necessary. Here, the conventional method for setting control standard values ​​is generally to use the direct strain method (or limit strain method). This method determines the limit strain based on the deformation modulus and uniaxial compressive strength of the natural ground, and sets the control standard value based on this limit strain. The limit strain is the strain that corresponds to the slope of the initial elastic modulus of the stress-strain curve obtained from the uniaxial compressive strength test of a rock core, and the uniaxial compressive strength. Therefore, the limit strain is defined as the strain that corresponds to the fracture stress of the natural ground, that is, the strain when the natural ground changes from a stable state to an unstable state. However, there are various issues with the method for setting control standard values ​​using the direct strain method.

[0003] First, the relationship between the uniaxial compressive strength (deformation coefficient) of the rock core and the limit strain is obtained using a regression equation, but the properties of the rock core and the actual ground are not necessarily the same. Since the actual ground contains a number of discontinuous surfaces such as cracks and fissures, the properties are significantly different from those of the rock core, and the "limit strain of the rock core" and the "limit strain of the ground" are not equal. Secondly, the uniaxial compressive strength and deformation coefficient of the natural ground cannot always be evaluated appropriately on-site. Currently, the limit strain is calculated based on the uniaxial compressive strength (deformation coefficient) recorded in the results of a prior geological survey, so there is a high possibility that the assumed uniaxial compressive strength (deformation coefficient) will differ from the actual natural ground, which may lead to a decrease in the reliability of the set management standard values. Next, the control standard values ​​set using the direct strain method are intended to ensure the stability of the ground based on limit strain, and therefore are not intended to evaluate the soundness of the supports supporting the tunnel. Next, the control standard values ​​are generally set in three stages, control levels I to III, with the control standard value for control level III being the displacement equivalent to the limit strain (sometimes a predicted value from FEM (Finite Element Method) analysis, etc.), and the control standard values ​​for levels I and II being 50% and 75% of level III, respectively, being widely adopted, but with this control system, when the displacement exceeds the control standard value, countermeasures are taken according to each control level, making it necessary to take emergency measures. Therefore, in reality, construction is carried out while monitoring the increase in displacement, and emergency measures are taken when control level III is exceeded, and it is difficult to say that this is a construction management method that fully guarantees construction safety.

[0004] For these reasons, a construction management method based on control standard values ​​that can evaluate the soundness of support structures is desirable, instead of a construction management method based on control standard values ​​set by the direct strain method.

[0005] Here, Patent Document 1 proposes a tunnel construction management method in which drilling exploration is performed ahead of the excavation direction of the tunnel face to evaluate the ground in the area where supports will be constructed, a support structure suitable for the surveyed section surveyed by drilling exploration is set, and suitable supports are constructed. Specifically, the method includes a support structure setting process for setting a support structure according to an initial ground stress based on the ground elastic modulus corresponding to the drilling energy measured by performing a drilling survey of the ground ahead of the excavation direction of the tunnel face and the displacement after construction of the support installed behind the tunnel face; a support construction process for constructing supports of the support structure set by the support structure setting process on the excavation wall surface excavated through the ground in the survey section where the drilling survey was performed; a judgment process for measuring the displacement of the support installed by the support construction process and predicting the amount of displacement of the support over time based on the measurement results to judge whether the support structure of the support was appropriate; and a support structure correction process for reviewing the correspondence between the drilling energy and the ground elastic modulus in the support structure setting process if it is judged by the judgment process that the support structure was not appropriate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-52373 A Summary of the Invention [Problem to be solved by the invention]

[0007] The tunnel construction management method described in Patent Document 1 is not a construction management method based on management standard values ​​that use the presence or absence of deformation of the support structure as an indicator, but rather sets the support structure based on the results of drilling exploration of the natural ground, and is therefore not significantly different from conventional construction management methods that are based on management standard values ​​set using the above-mentioned direct strain method.

[0008] The present invention aims to provide a tunnel construction management method and construction management system based on management reference values ​​that can evaluate the soundness of the support structure. [Means for solving the problem]

[0009] To achieve the above object, one aspect of the tunnel construction management method according to the present invention is a tunnel construction management method for constructing a tunnel while repeating tunneling and installation of support work, and performing construction management based on the displacement amount of the support work, an A step of setting an allowable strain at the time of damage to the support work from a plurality of tunnel construction cases in which damage to the support work has been confirmed; a B step of setting a management reference value for the support work by multiplying the excavation radius of the tunnel to be managed by the allowable strain; a C step of measuring a measured value related to the displacement amount as the tunnel is excavated; and a D step of comparing the management reference value with the measured value and determining the suitability of the support work.

[0010] According to this aspect, by setting the allowable strain at the time of damage to the support work from a plurality of tunnel construction cases in which damage to the support work has been confirmed, and multiplying the allowable strain by the excavation radius of the tunnel to be managed to set the management reference value for the support work, it is possible to set a management reference value that reflects the strain at the time of damage to the support work and the scale (excavation radius) of the tunnel to be managed, and that can be used to evaluate the soundness of the support work. Then, by comparing this management reference value with the measured value related to the displacement amount of the support work as the tunnel is excavated and determining the suitability of the support work, it is possible to appropriately evaluate the soundness of the support work.

[0011] Here, the "plurality of tunnel construction cases" includes tunnel construction cases in which damage to the support work has been confirmed and that have been published by the Japan Tunneling Technology Association, the Civil Engineering Society, etc., in addition to the past tunnel construction records held by construction companies. In addition, the "support work" includes shotcrete, steel support work, rock bolts, etc., and the "damage to the support work" includes cracks and peeling of shotcrete, deformation and buckling of steel support work, deformation of washer plates of rock bolts, and breakage of rock bolts.

[0012] In another aspect of the tunnel construction management method according to the present invention, In the step A, the amount of displacement when the support is damaged is divided by the excavation radius of the tunnel, and then corrected by a predetermined safety factor to obtain the allowable strain.

[0013] According to this aspect, when setting the allowable strain that serves as the basis for the control standard value, the amount of displacement when the support is damaged is divided by the excavation radius of the tunnel to be managed, and then corrected by a predetermined safety factor to obtain the allowable strain, thereby making it possible to set a safe control standard value.

[0014] In another aspect of the tunnel construction management method according to the present invention, The step A is characterized in that the strain of the support when damaged is set to 2% or less.

[0015] According to this embodiment, by setting the strain when the shoring is damaged (displacement of the shoring (or tunnel wall) / tunnel excavation radius) to 2% or less, a highly accurate management standard value based on tunnel construction examples can be set. According to the inventors, as a result of examining many past tunnel construction examples, it has been determined that the strain when deformation occurs in the shoring is about 1 to 2%. Based on the results of this verification, a dangerous control standard value based on tunnel construction examples can be set by setting the allowable strain at 2%, and a safe control standard value based on tunnel construction examples can be set by setting the allowable strain at 1%, and a safer control standard value can be set by taking into account a further safety factor for a strain of, for example, 1%. Here, the safety factor can be set to about 1.1 to 1.5, and for example, when a safety factor of 1.25 is taken into account for a strain of 1%, the allowable strain is set to 0.8%.

[0016] In another aspect of the tunnel construction management method according to the present invention, In the step A, based on the tunnel construction examples, each initial displacement amount measured for each of a plurality of excavation stages from a reference position is set as the displacement amount, and based on the final displacement amount converged at the reference position as the tunnel is excavated and the initial displacement amount for each of the plurality of excavation stages, a relation coefficient between the final displacement amount and the initial displacement amount is set for each of the plurality of excavation stages; In the step B, the allowable strain is multiplied by the excavation radius of the tunnel for each of a plurality of excavation stages, and then corrected by the relation coefficient to set the control reference value for each of a plurality of excavation stages; In the step C, a measurement value related to the displacement is measured for each of a plurality of excavation stages, The step D is characterized in that the control standard values ​​and the measured values ​​are compared for each of a plurality of excavation stages to determine whether the support is adequate.

[0017] According to this aspect, based on tunnel construction examples, a relationship coefficient is set between the initial displacement amount from the reference position for each of the multiple excavation stages and the final displacement amount at the reference position, and for each excavation stage, the value obtained by multiplying the allowable strain by the excavation radius of the tunnel is corrected with the relationship coefficient to set a control standard value for each of the multiple excavation stages, and construction management for each excavation stage is performed based on this control standard value, thereby making it possible to realize construction management with even higher construction safety. Here, "correction using a relationship coefficient" includes a form of correction by multiplication by the relationship coefficient and a form of correction by division by the relationship coefficient. Furthermore, "multiple excavation stages" refers to the first 1m or so of excavation (1 excavation), 0.5D excavation, 1D excavation, 2D excavation, etc., when the excavation diameter is D. Since it is generally specified that the displacement of the tunnel wall (or the displacement of the support) at the reference position converges at about 2D excavation from the reference position, it is advisable to set multiple excavation stages (excavation stages) up to about 2D excavation. In more detail, it is specified that at the stage when the face is constructed at the reference position, about 40% of the total stress is released at the reference position, and therefore, at the stage of excavation of about 2D from the reference position, a displacement equivalent to 60% of the total stress occurs.

[0018] In another aspect of the tunnel construction management method according to the present invention, In the step A, the relationship coefficient is obtained by regression analysis.

[0019] According to this aspect, by determining the relationship coefficient by regression analysis, it is possible to set the relationship coefficient based on a plurality of tunnel construction cases and the control standard value for each excavation stage based thereon with high accuracy.

[0020] In addition, one aspect of the tunnel construction management system according to the present invention is A tunnel construction management system that performs construction management based on the displacement of a support structure when constructing a tunnel by repeatedly excavating the tunnel and installing a support structure, comprising: A setting evaluation device; a measuring device that measures the amount of displacement as the tunnel is excavated to obtain a measurement value; The setting evaluation device includes: A storage unit that stores at least a plurality of tunnel construction examples in which damage to shoring has been confirmed and a shoring table in which the plurality of shorings are classified according to their rigidity; an allowable strain setting unit that sets an allowable strain when the support is damaged based on a plurality of tunnel construction examples in the storage unit; a control standard value setting unit that sets a control standard value of the support by multiplying the allowable strain by an excavation radius of a tunnel to be managed; The present invention is characterized by having a support evaluation unit that compares the management standard value with the measurement value, extracts the currently set support from the support table, and determines whether the support is appropriate.

[0021] According to this aspect, the allowable strain setting unit sets the allowable strain when the shoring is damaged based on multiple tunnel construction cases, and the control reference value setting unit sets the control reference value for the shoring by multiplying the allowable strain by the excavation radius of the tunnel to be managed, thereby making it possible to set a control reference value that reflects the strain when the shoring is damaged and the scale of the tunnel to be managed and that can evaluate the soundness of the shoring.The soundness of the shoring can be properly evaluated by comparing this control reference value with the measured value related to the amount of displacement of the shoring associated with the excavation of the tunnel to determine whether the currently set shoring is appropriate. Here, in the "support table classifying multiple supports according to their rigidity", support patterns such as B, CI, CII, DI, DII, etc. corresponding to the ground grade are set, and for each support pattern, the thickness of the sprayed concrete, the specifications and erection intervals of the steel support, the length and number of rock bolts, the circumferential spacing, the extension spacing, etc. are set.

[0022] In another aspect of the tunnel construction management system according to the present invention, In the allowable strain setting unit, based on the tunnel construction examples, each initial displacement amount measured for each of a plurality of excavation stages from a reference position is set as the displacement amount, and based on the final displacement amount that converges at the reference position as the tunnel is excavated and the initial displacement amount for each of the plurality of excavation stages, a relation coefficient between the final displacement amount and the initial displacement amount is set for each of the plurality of excavation stages; the control reference value setting unit sets the control reference value by correcting a value obtained by multiplying the allowable strain by the excavation radius of the tunnel with the relation coefficient for each of a plurality of excavation stages; The storage unit stores the measurement values ​​regarding the displacement amount for each of a plurality of excavation stages, The support evaluation unit is characterized in that the control standard values ​​and the measured values ​​are compared for each of a plurality of excavation stages to determine whether the support is adequate.

[0023] According to this aspect, the allowable strain setting unit sets a relationship coefficient between the initial displacement amount from the reference position for each of the multiple excavation stages and the final displacement amount at the reference position based on tunnel construction examples, the control standard value setting unit corrects the value obtained by multiplying the allowable strain by the excavation radius of the tunnel for each excavation stage with the relationship coefficient to set the control standard value for each of the multiple excavation stages, and the support evaluation unit performs construction management for each excavation stage based on the control standard value for each excavation stage, thereby achieving construction management with even higher construction safety. Effect of the Invention

[0024] According to the tunnel construction management method and construction management system of the present invention, the soundness of the support can be properly evaluated based on the management reference value with which the soundness of the support can be evaluated. [Brief description of the drawings]

[0025] [Figure 1] 1 is an overall configuration diagram showing an example of a tunnel construction management system according to an embodiment. FIG. [Diagram 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a computer constituting a construction management system. [Diagram 3] FIG. 2 is a diagram illustrating an example of a functional configuration of a setting evaluation device constituting the construction management system. [Figure 4] This is an example of a tunnel construction example, and is a table summarizing construction examples based on past construction results. [Diagram 5] 13 is another example of tunnel construction examples, which is a table summarizing construction examples described in publicly known documents. [Figure 6A] This is a frequency distribution diagram of strain related to the settlement of the tunnel top based on a tunnel construction example. [Figure 6B] This is a frequency distribution diagram of strain related to 1 / 2 the internal displacement of a tunnel based on a tunnel construction example. [Figure 6C] FIG. 6C is a frequency distribution diagram of the average values ​​of FIG. 6A and FIG. 6B. [Figure 7A]FIG. 1 is a distribution diagram showing the relationship between circumferential strain and tunnel radius based on tunnel construction examples. [Figure 7B] This is a distribution diagram showing the relationship between circumferential strain and sprayed concrete thickness based on a tunnel construction example. [Figure 7C] 7A and 7B, this is a distribution diagram showing the relationship between circumferential strain and the equivalent thickness of the shotcrete based on a tunnel radius of 5 m. [Figure 7D] This is a distribution diagram showing the relationship between circumferential strain and earth covering based on a tunnel construction example. [Figure 8] This is a graph explaining a method for determining the support yield stress based on a ground characteristic curve using a circular hole theoretical solution and a support characteristic curve based on the support specifications at the time of deformation. [Figure 9] 9 is a diagram showing an example in which the graph shown in FIG. 8 is applied to the No. 1 A tunnel in the table of FIG. [Figure 10] 11 is a graph illustrating the relationship between the initial displacement and the final displacement at the reference position. [Figure 11] FIG. 13 is a diagram showing regression lines determined by simple regression analysis from the relationship between initial strain and final strain for each of a number of excavation stages. [Figure 12A] FIG. 13 is an example of a control graph in which control reference values ​​and measurement values ​​set for multiple excavation stages are plotted, showing a case in which all measurement values ​​are below the control reference values. [Figure 12B] FIG. 13 is an example of a control graph in which control reference values ​​and measurement values ​​set for multiple excavation stages are plotted, showing a case in which the measurement value exceeds the control reference value. [Figure 13] 1 is a flowchart of an example of a tunnel construction management method according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, a tunnel construction management system and a construction management method according to an embodiment will be described with reference to the accompanying drawings. In this specification and the drawings, substantially identical components are designated by the same reference numerals, and duplicated explanations may be omitted.

[0027] [Embodiment] <Tunnel construction management system> First, an example of a tunnel construction management system according to an embodiment will be described with reference to Fig. 1 to Fig. 12. Here, Fig. 1 is an overall configuration diagram showing an example of a tunnel construction management system according to an embodiment. Fig. 2 is a diagram showing an example of a hardware configuration of a computer constituting the construction management system, and Fig. 3 is a diagram showing an example of a functional configuration of a setting evaluation device constituting the construction management system.

[0028] The tunnel construction management system 100 is a construction management system that performs construction management based on the amount of displacement of supports when constructing a tunnel by repeatedly excavating the tunnel and installing supports.

[0029] The construction management system 100 has a measuring device 10 and a setting evaluation device 20 that measure the amount of displacement of the support as the tunnel is excavated and obtains measurement values. The construction management system 100 in the illustrated example is configured such that the measuring device 10 and the setting evaluation device 20 are connected so as to be able to transmit and receive measurement data via a network 30. Here, the measuring device 10 and the setting evaluation device 20 may not be connected via the network 30 and may transmit and receive data via a wired connection.

[0030] Examples of the measuring device 10 include measuring instruments such as a three-dimensional laser measuring device and a total station, as well as a digital camera with a strobe. When using a digital camera, a digital photo measurement method is applied in which a reflector or the like is attached to the side of the support and displacement measurement is performed based on the captured image data.

[0031] The setting evaluation device 20 has various functions as shown in Fig. 3, which will be described in detail below. Both the measurement device 10 and the setting evaluation device 20 are configured by computers, but in the following explanation with reference to Fig. 2, the setting evaluation device 20 will be described.

[0032] The personal computer constituting the setting evaluation device 20 includes a CPU (Central Processing Unit) 21, a main memory device 22, an auxiliary memory device 23, a communication IF 24, and an input / output IF (interface) 25, which are interconnected by a connection bus 26. The main memory device 22 and the auxiliary memory device 23 are computer-readable recording media. The above components may be provided separately, or some of the components may not be provided.

[0033] The CPU 21 is also called an MPU (Microprocessor) or a processor, and may be a single processor or a multiprocessor. The CPU 21 is a central processing unit that performs overall control of the setting evaluation device 20. For example, the CPU 21 develops a program stored in the auxiliary storage device 23 in an executable manner in a working area of ​​the main storage device 22, and controls peripheral devices through the execution of the program, thereby providing a function that meets a predetermined purpose.

[0034] The main storage device 22 stores computer programs executed by the CPU 21, data processed by the CPU 21, etc. The main storage device 22 includes, for example, a flash memory, a RAM (Random Access Memory), and a ROM (Read Only Memory). The auxiliary storage device 23 stores various programs and various data in a readable and writable recording medium, and is also called an external storage device. The auxiliary storage device 23 stores, for example, an OS (Operating System), various programs, various tables, etc. The OS includes, for example, a communication interface program that transfers data to and from external devices connected via the communication IF 24. The external devices for the setting evaluation device 20 include the measurement device 10, a host computer in the department to which the measurer belongs, and smartphones and tablets carried by other measurers, etc.

[0035] The auxiliary storage device 23 is used, for example, as a storage area that assists the main storage device 22, and stores computer programs executed by the CPU 21, data processed by the CPU 21, etc. The auxiliary storage device 23 is a silicon disk including a non-volatile semiconductor memory (flash memory, EPROM (Erasable Programmable ROM)), a hard disk drive (HDD: Hard Disk Drive) device, a solid state drive device, etc. Examples of the auxiliary storage device 23 include a drive device for a removable recording medium such as a CD drive device, a DVD drive device, and a BD drive device, and examples of the removable recording medium include a CD, a DVD, a BD, a USB (Universal Serial Bus) memory, and an SD (Secure Digital) memory card, etc.

[0036] The input / output IF25 is an interface for inputting and outputting data between devices connected to the setting evaluation device 20. For example, input devices such as a keyboard, a touch panel, a mouse, or the like, and a microphone are connected to the input / output IF25. The setting evaluation device 20 receives operation instructions and the like from an operator who operates an input device via the input / output IF25.

[0037] In addition, for example, a display device such as a liquid crystal panel (LCD: Liquid Crystal Display) or an organic EL panel (EL: Electroluminescence) and an output device such as a printer and a speaker are connected to the input / output IF 25. The setting evaluation device 20 is configured to continuously display the management reference values ​​for each of a plurality of excavation stages and the measured values ​​related to the displacement amount of the support.

[0038] The communication IF 24 is an interface with a network to which the setting evaluation device 20 is connected. The communication IF 24 receives the measurement value by the measurement device 10 via various networks such as a public network such as the Internet, a wireless network such as a mobile phone network, a dedicated network such as a Virtual Private Network (VPN), a Local Area Network (LAN), etc., and transmits management data indicating the management reference value and the measurement value to a host computer, etc. Here, an LPWA wireless communication module and a communication antenna, etc. may be connected to the communication IF 24. The LPWA wireless communication module is a device that realizes LPWA wireless communication (wireless transmission), and is, for example, an electronic component in which a wireless chip and a peripheral circuit are mounted on a small board. The main communication methods (communication protocols) of LPWA include Sigfox, LoRaWAN (Long Range Wide Area Network), NB-IoT, etc., but it is preferable to apply LoRaWAN, which does not require a license, can install a self-operated base station in a mine even in mountainous areas where mobile phone communication waves are difficult to reach, and can build a low-cost communication system. LoRaWAN is a communication method that uses the 920 MHz ISM band and adopts LoRa modulation, enabling long-distance communication even with low output of 13 dBm or less.

[0039] 3, the setting evaluation device 20 provides various functions, such as at least a communication unit 202, an allowable strain setting unit 204, a management reference value setting unit 206, a support evaluation unit 208, a display unit 210, and a storage unit 212, by executing a program by a CPU 21. Here, at least a part of the above processing functions may be provided by a DSP (Digital Signal Processor), a GPU (Graphics Processing Unit), or the like, and similarly, at least a part of the above processing functions may be a dedicated LSI (large scale integration) such as an FPGA (Field-Programmable Gate Array), a numerical calculation processor, an image processing processor, or other digital circuits, or the like.

[0040] The communication unit 202 receives the displacement measurement data (measurement values) of the support transmitted from the measuring device 10 at any time, and stores the data in the storage unit 212 at any time.

[0041] A plurality of tunnel construction examples in which damage to shoring has been confirmed are stored in the storage unit 212. The storage unit 212 further stores a shoring table in which a plurality of shorings are classified according to their rigidity.

[0042] Here, Figures 4 and 5 show examples of tunnel construction examples. More specifically, Figure 4 is a table summarizing construction examples based on past construction results, and Figure 5 is a table summarizing construction examples described in publicly known documents.

[0043] FIG. 4 shows the earth covering, geology, deformation position of support members (shoring), face separation, tunnel conversion radius (for example, the radius when a horseshoe-shaped tunnel is simulated as a circle), support pattern (shoring pattern) at the time of deformation, and measured displacement for 26 cases from A tunnel to Z tunnel, and the "circumferential strain" in the right column is calculated from the tunnel conversion radius and the measured displacement. In this specification, "circumferential strain" refers to the radial strain at multiple points (top, inner space, wall surface) in the circumferential direction of the tunnel. In addition to the examples shown in FIG. 4, there are other construction examples based on construction results compiled by the inventors, and FIG. 4 shows one example.

[0044] Here, the circumferential strain: εt (%) is calculated by dividing the measured displacement of the tunnel (radial displacement): Ur (m) by the tunnel excavation radius (or equivalent radius, in m): R, and multiplying it by 100.

[0045] On the other hand, FIG. 5 shows 15 examples from the literature, Tunnels and Underground, Japan Tunneling Association, January 2000 issue to December 2017 issue (total 216 volumes), and in principle shows the same information as FIG. 4 (information other than circumferential strain). Here, in addition to the examples shown in FIG. 5, construction examples described in publicly available literature compiled by the present inventors include construction examples described in the Japan Society of Civil Engineers: Tunnel Engineering Research Presentations, Papers and Reports, 1991 to 2020 (total 20 volumes), Japan Tunneling Association: Construction Experience Presentations, 2000 to 2019 (total 20 volumes), etc.

[0046] The inventors have obtained the frequency distribution of strain related to the displacement of tunnel supports, including the construction examples shown in Figures 4 and 5 and other construction examples not shown, and the contents are shown in Figures 6A to 6C. Here, Figure 6A is a frequency distribution diagram of strain related to the amount of settlement of the top end of the tunnel based on the tunnel construction examples, Figure 6B is a frequency distribution diagram of strain related to the amount of internal displacement of the tunnel × 1 / 2, and Figure 6C is a frequency distribution diagram of the average value of Figures 6A and 6B.

[0047] The percentages in each figure indicate the frequency of each strain range relative to the total number of surveys. As shown in Figures 6A and 6B, the strain due to crown settlement or internal displacement x 1 / 2 is mostly distributed in the range of 2.0% or less, accounting for 87.5% of the total number of surveys in the former and 91.1% in the latter. Therefore, regardless of the difference in deformation mode, such as when crown settlement or internal displacement is predominant, it is presumed that deformation of the support occurs at a strain level of 2% or less. In addition, since the average values ​​of strains in the range of 2% or less in Figures 6A to 6C are 0.81%, 1.02%, and 0.97%, respectively, it can be evaluated that deformation of the support occurs at a strain of approximately 1%.

[0048] Next, the analysis results of the relationship between the strain when deformation of supports occurs and three items, (1) tunnel radius, (2) thickness of shotcrete, and (3) earth covering, are shown in Figures 7A to 7D. Here, Figure 7A is a distribution diagram showing the relationship between circumferential strain and tunnel radius based on a tunnel construction example, Figure 7B is a distribution diagram showing the relationship between circumferential strain and thickness of shotcrete, and Figure 7C is a distribution diagram showing the relationship between circumferential strain and equivalent thickness of shotcrete based on a tunnel radius of 5 m based on Figures 7A and 7B. Also, Figure 7D is a distribution diagram showing the relationship between circumferential strain and earth covering based on a tunnel construction example.

[0049] From FIG. 7A, it can be seen that for any tunnel radius, the strain caused by deformation of the support is mostly distributed in the range of around 1% to 2%.

[0050] Furthermore, from FIG. 7B, it can be seen that the thickness of the shotcrete was in the range of 100 mm to 300 mm, and that the strain caused by deformation of the support was mostly distributed in the range of around 1% to 2%, regardless of the thickness of the shotcrete.

[0051] Here, since the results in Figure 7B include the effect of the tunnel radius, this effect is removed using the following method, and the relationship between the shotcrete thickness and strain is rearranged. Specifically, the shotcrete thickness for all deformation cases is calculated as a converted thickness based on a tunnel radius of 5m. Theoretically, the ring stiffness Kc (MPa) of the shotcrete is expressed as Kc = Ectc / (1-νc 2 ) / R (Ec: elastic modulus of shotcrete (MPa), tc: thickness of shotcrete (m), νc: Poisson's ratio of shotcrete, R: tunnel excavation radius (m)), where Kc is proportional to the thickness of the shotcrete and inversely proportional to the tunnel radius. The equivalent thickness based on a tunnel radius of 5m is calculated by dividing the shotcrete thickness tc for all deformation cases by the tunnel radius R and then multiplying it by a radius of 5m. Figure 7C shows the relationship between strain and this equivalent thickness.

[0052] From Fig. 7C, it can be seen that the strain caused by deformation of the support is mostly distributed in the range of 100mm to 250mm of equivalent thickness, and is about 1% to 2% regardless of the equivalent thickness. Since a shotcrete thickness of 100mm to 250mm corresponds to the thickness generally set as the standard support pattern, it is inferred that some kind of deformation will occur in the support member when a strain of about 1% to 2% occurs, regardless of the rank of the standard support pattern (or the size of the shotcrete thickness). Therefore, a strain value of about 1% to 2% can be used as a suitable index range for evaluating the stability of a support structure.

[0053] Finally, from Figure 7D, the strain caused by deformation of the support is mostly distributed in the range of about 1% to 2%, and no bias in distribution due to the amount of soil cover is observed. Therefore, regardless of the amount of soil cover, if the strain occurs at about 1% to 2%, some kind of deformation will occur in the support member.

[0054] Here, we will verify examples of support deformation by theoretical calculation with reference to Fig. 8. Fig. 8 is a graph that explains a method for identifying the support yield stress based on the natural ground characteristic curve using the circular hole theoretical solution and the support characteristic curve based on the support specifications at the time of deformation.

[0055] Factors influencing tunnel deformation include earth covering (initial earth pressure) and the physical properties of the ground related to the geology and ground characteristics (deformation coefficient, strength constant, etc.), but as discussed with reference to Fig. 7D, in actual construction records, deformations have been observed in support members regardless of the amount of earth covering. Therefore, focusing on the deformation coefficient, one of the physical properties of the ground, we estimate the stress generated in the support based on the circular hole theory solution that represents tunnel excavation for tunnels where examples of support deformation have been investigated.

[0056] The deformation coefficient of the natural ground is set to an arbitrary value, and the natural ground characteristic curve is drawn using the circular hole theory solution. Here, the natural ground characteristic curve is determined by the following parameters, which include the tunnel excavation radius, earth covering, unit volume weight of the natural ground, deformation coefficient, and Poisson's ratio.

[0057] Next, a support characteristic curve is drawn based on the specifications of the support components at the time deformation occurred. The slope of the support characteristic curve and the stress value at yield are determined by the following parameters. Specifically, these parameters include: shotcrete: tunnel excavation radius, elastic modulus, thickness, and design strength; steel support: tunnel excavation radius, elastic modulus, cross-sectional area, pitch, and yield strength. Rock bolts are not taken into consideration because they do not contribute to deformation suppression more than shotcrete and steel support.

[0058] Next, since the amount of displacement that occurs from when the support characteristic curve is drawn to when it intersects with the ground characteristic curve (the point where the "stress and displacement" of the "ground and support" are balanced) corresponds to the measured displacement amount, the ground deformation coefficient (ground characteristic curve) is repeatedly changed until this displacement amount becomes equal to the displacement amount at the time the deformation occurred, thereby estimating the ground deformation coefficient.

[0059] Next, the intersection point (the balance point of stress and displacement) between the natural ground characteristic curve and the support characteristic curve is determined, and the stress generated in the support at the balance point is compared with the strength of the support structure.

[0060] FIG. 9 shows the results of verifying examples of support deformation by theoretical calculation for the No. 1 A tunnel in the table of FIG.

[0061] From FIG. 9, it can be confirmed that the stresses generated in the shotcrete and the steel support exceeded the design standard strength or yield strength, respectively, and that the stresses were equivalent to or greater than the stresses that would cause deformation in the support. Although not shown, the inventors performed similar verifications in the other tunnels shown in FIG. 4 and obtained similar results. Therefore, the post-verification using the theoretical solution provides evidence that deformation occurred in the support, as in the case of the investigation. It was also confirmed that the estimated deformation coefficient of the ground varied from tunnel to tunnel. From this, it can be inferred that some deformation will occur in the support members when a strain of about 1% to 2% occurs, regardless of the magnitude of the deformation coefficient.

[0062] Returning to Fig. 3, based on the various considerations described above, the allowable strain setting unit 204 sets the allowable strain when the support is damaged in the range of 1% to 2%. Here, by setting the allowable strain to 2%, a dangerous management reference value based on tunnel construction examples can be set, and by setting the allowable strain to 1%, a safe management reference value based on tunnel construction examples can be set. The allowable strain setting unit 204 may automatically set an appropriate allowable strain for the tunnel to be managed in the range of about 1% to 2%, or an allowable strain set by a construction manager or the like in the range of about 1% to 2% may be input to the allowable strain setting unit 204.

[0063] In addition, for example, a safety factor may be set for a strain of 1%, and a safer control standard value can be set by setting a safety factor. Here, the safety factor can be set to about 1.1 to 1.5, and for example, when a safety factor of 1.25 is set for a strain of 1%, the allowable strain is set to 0.8%.

[0064] The control standard value setting unit 206 sets the control standard value of the support by multiplying the allowable strain set in the allowable strain setting unit 204 by the excavation radius of the tunnel to be managed.

[0065] Regarding the setting of the control standard values ​​for shoring, setting control standard values ​​for each of the multiple excavation stages can lead to an even more reliable evaluation of the soundness of the shoring. Here, with reference to Figs. 10 and 11, the displacement of the ground at the shoring (or tunnel wall) according to the excavation stage will be considered. Fig. 10 is a graph explaining the relationship between the initial displacement and the final displacement at the reference position, and is a conceptual diagram showing the state of displacement occurring during the tunnel excavation process. Also, Fig. 11 is a diagram showing the regression line identified by simple regression analysis from the relationship between the initial strain and the final strain for each of the multiple excavation stages.

[0066] In predicting the final displacement (amount) from the initial displacement (amount) at any reference position according to the tunnel excavation, the relationship between the initial displacement and the final displacement is estimated by regression analysis. Here, "initial displacement (amount)" is defined as the displacement (amount) that occurs from the time the initial measurement value is obtained until the face advances to about 2D (D is the tunnel excavation diameter), and "final displacement (amount)" is defined as the displacement (amount) at the point when the tunnel deformation converges.

[0067] The displacement from the initial measurement at the face to 1D of excavation (approximately 1m of excavation), 0.5D of excavation, 1D of excavation, and 2D of excavation are defined as the initial displacement, and then a regression analysis is performed to determine the relationship between the measurement data and the final displacement. Here, the strain based on the initial displacement is called the initial strain, and the strain based on the final displacement is called the final strain.

[0068] The inventors performed regression analysis on 950 tunnels from past construction records (construction examples). The relationship between initial strain and final strain is calculated by simple regression analysis as final strain / initial strain (=relationship coefficient A). An example of the results is shown in Figure 11.

[0069] As can be seen from Figure 11, the later the initial strain is obtained (the longer the separation from the face), the closer the relationship coefficient A is to 1, and the correlation between the initial strain and the final strain (the reliability of the relationship coefficient A) tends to be higher. Also, from Figure 11, the final strain is generally about 3 to 3.4 times, 1.5 to 1.7 times, 1.2 to 1.4 times, and 1.1 to 1.2 times the initial strain at 1D excavation, 0.5D excavation, 1D excavation, and 2D excavation, respectively, after the initial measurement value is obtained.

[0070] As an example, the allowable strain is set to 0.8%, and the control standard values ​​for each excavation stage are set as shown in Table 1 below.

[0071] [Table 1]

[0072] The display unit 210 displays the control standard values ​​for each excavation stage and the measurement values ​​related to the displacement of the support in the excavation stage. Here, Fig. 12A and Fig. 12B show an example of a control graph in which the control standard values ​​and the measurement values ​​set for a plurality of excavation stages are plotted, and more specifically, Fig. 12A shows a case in which all the measurement values ​​are below the control standard values, and Fig. 12B shows a case in which the measurement values ​​exceed the control standard values.

[0073] Returning to Fig. 3, the shoring evaluation unit 208 compares the control standard values ​​and the measured values ​​for each excavation stage. Then, the currently set shoring is extracted from the shoring table stored in the storage unit 212, and the suitability of the shoring is judged.

[0074] Here, the support table is not shown in the figure, but support patterns such as B, CI, CII, DI, DII, etc. are set corresponding to the ground grade, and for each support pattern, the thickness of the sprayed concrete, the specifications and erection intervals of the steel support, the length and number of rock bolts, the circumferential spacing, the extension spacing, etc. are set.

[0075] In Figure 12B, the measurement value exceeds the control standard value at 0.5D of excavation, and the subsequent measurement values ​​also exceed the control standard value, eventually causing a deformation in the support. The illustrated example shows that some kind of countermeasure work needs to be implemented early at 0.5D of excavation, but by managing the construction based on the control standard value for each excavation stage, early countermeasure work can be planned and implemented, resulting in tunnel construction with high construction safety.

[0076] According to the construction management system 100, the allowable strain setting unit 204 sets the allowable strain when the shoring is damaged based on multiple tunnel construction cases, and the control standard value setting unit 206 sets the control standard value for the shoring by multiplying the allowable strain by the excavation radius of the tunnel to be managed, making it possible to set a control standard value that can evaluate the soundness of the shoring, reflecting the strain when the shoring is damaged and the scale of the tunnel to be managed.

[0077] The soundness of the support can be properly evaluated by comparing this control standard value with the measured value of the amount of displacement of the support associated with the excavation of the tunnel to determine the suitability of the currently set support.

[0078] Furthermore, by managing construction based on the control standard values ​​for each excavation stage, early countermeasure work can be planned and implemented, resulting in tunnel construction with high construction safety.

[0079] <Tunnel construction management method> Next, an example of a tunnel construction management method according to the embodiment will be described with reference to Fig. 13. Here, Fig. 13 is a flowchart of an example of a tunnel construction management method according to the embodiment.

[0080] This construction management method is a construction management method in which construction management is performed based on the amount of displacement of the supports when constructing a tunnel by repeatedly excavating the tunnel and installing supports.

[0081] First, the allowable strain when the support is damaged is set based on several tunnel construction examples where damage to the support has been confirmed. Here, an example of several tunnel construction examples is described with reference to Figs. 4 and 5.

[0082] The allowable strain is preferably set in the range of about 1% to 2%, and when a further safety factor is taken into account, a safer allowable strain is set (Step S10, Process A).

[0083] Next, the control standard value for the support is set by multiplying the allowable strain by the excavation radius of the tunnel to be managed.

[0084] In setting these control standard values, setting control standard values ​​for each of the multiple excavation stages leads to early planning and implementation of countermeasure work, leading to the realization of tunnel construction with high construction safety (Step S12, Process B).

[0085] Next, as the tunnel advances, measurements are taken of the amount of displacement of the support structure.

[0086] In construction management based on management reference values ​​for a plurality of excavation stages, measurement values ​​are taken for each excavation stage (step S14, process C).

[0087] Next, the measurement values ​​are compared with the control standard values ​​to determine whether the support structure is adequate.

[0088] In construction management based on the control standard values ​​for each of a plurality of excavation stages, the suitability of support work is judged for each excavation stage (Step S16, Process D).

[0089] If the shoring is judged to be inappropriate in this suitability assessment, countermeasures are considered and implemented (step S18).

[0090] According to the tunnel construction management method of the embodiment, the allowable strain when the shoring is damaged is set from a number of tunnel construction cases where damage to the shoring has been confirmed, and the allowable strain is multiplied by the excavation radius of the tunnel to be managed to set the management reference value for the shoring, thereby allowing the management reference value that reflects the strain when the shoring is damaged and the size of the tunnel to be managed to be set and allows the soundness of the shoring to be evaluated. Then, the soundness of the shoring can be properly evaluated by comparing this management reference value with the measured value of the displacement of the shoring associated with the excavation of the tunnel to determine whether the shoring is suitable or not. Furthermore, by performing construction management based on the management reference value for each excavation stage, early countermeasure work can be planned and implemented, and tunnel construction with high construction safety can be realized.

[0091] In addition, the present invention is not limited to the configuration shown here, and may be implemented in other embodiments in which other components are combined with the configurations and the like of the above-mentioned embodiment. In this regard, the present invention may be modified within the scope of the gist of the present invention, and may be appropriately determined according to the application form. [Explanation of symbols]

[0092] 10: Measurement equipment 20: Setting evaluation device 30: Network 100: Tunnel construction management system (construction management system) 202: Communications Department 204: Allowable strain setting section 206: Control standard value setting section 208: Shoring Evaluation Department 210: Display section 212: Storage area

Claims

1. A tunnel construction management method for performing construction management based on the displacement of a support structure when constructing a tunnel by repeatedly excavating the tunnel and installing a support structure, comprising: Step A is to set the allowable strain when the support is damaged based on a number of tunnel construction cases in which damage to the support has been confirmed; A process B of multiplying the allowable strain by the excavation radius of the tunnel to be managed to set a management reference value for the support; A step C of measuring the displacement amount as the tunnel is excavated; A tunnel construction management method, comprising a step D of comparing the management standard value with the measured value to determine whether the support work is suitable.

2. 2. The tunnel construction management method according to claim 1, characterized in that in step A, the amount of displacement when the support is damaged is divided by the excavation radius of the tunnel, and then corrected by a predetermined safety factor to obtain the allowable strain.

3. 3. A tunnel construction management method as described in claim 1 or 2, characterized in that in the step A, the strain of the support when damaged is set to 2% or less.

4. In the step A, based on the tunnel construction examples, each initial displacement amount measured for each of a plurality of excavation stages from a reference position is set as the displacement amount, and based on the final displacement amount converged at the reference position as the tunnel is excavated and the initial displacement amount for each of the plurality of excavation stages, a relation coefficient between the final displacement amount and the initial displacement amount is set for each of the plurality of excavation stages; In the step B, the allowable strain is multiplied by the excavation radius of the tunnel for each of a plurality of excavation stages, and then corrected by the relation coefficient to set the control reference value for each of a plurality of excavation stages; In the C step, a measurement value related to the displacement is measured for each of a plurality of excavation stages, 4. A tunnel construction management method according to claim 1, wherein in step D, the management standard value is compared with the measured value for each of a plurality of excavation stages to determine whether the support work is appropriate.

5. 5. The tunnel construction management method according to claim 4, wherein in the step A, the relationship coefficient is determined by regression analysis.

6. A tunnel construction management system that performs construction management based on the displacement of a support structure when constructing a tunnel by repeatedly excavating the tunnel and installing a support structure, comprising: A setting evaluation device; a measuring device that measures the amount of displacement as the tunnel is excavated to obtain a measurement value; The setting evaluation device includes: A storage unit that stores at least a plurality of tunnel construction examples in which damage to shoring has been confirmed and a shoring table in which the plurality of shorings are classified according to their rigidity; an allowable strain setting unit that sets an allowable strain when the support is damaged based on a plurality of tunnel construction examples in the storage unit; a control standard value setting unit that sets a control standard value of the support by multiplying the allowable strain by an excavation radius of a tunnel to be managed; A tunnel construction management system characterized by having a support evaluation unit that compares the management standard value with the measured value, extracts the currently set support from the support table, and determines whether the support is appropriate.

7. In the allowable strain setting unit, based on the tunnel construction examples, each initial displacement amount measured for each of a plurality of excavation stages from a reference position is set as the displacement amount, and based on the final displacement amount that converges at the reference position as the tunnel is excavated and the initial displacement amount for each of the plurality of excavation stages, a relation coefficient between the final displacement amount and the initial displacement amount is set for each of the plurality of excavation stages; In the control standard value setting unit, the control standard value is set by correcting a value obtained by multiplying the allowable strain by the excavation radius of the tunnel for each of a plurality of excavation stages using the relationship coefficient; The storage unit stores the measurement values ​​regarding the displacement amount for each of a plurality of excavation stages, The tunnel construction management system according to claim 6, characterized in that in the support evaluation unit, the control standard value and the measured value are compared for each of a plurality of excavation stages to determine whether the support is appropriate.

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