Tunnel face stability evaluation method

Abstract

Since the slip safety factor in consideration of the adhesive force can be evaluated and an appropriate physical property value can be set even if there is no previous measurement data, rational stability evaluation can be performed.SOLUTION: A step of setting a collapse region in front of a working face, a step of calculating a safety factor with respect to a slip of a clod in the set collapse region, and a step of determining stability of the working face on the basis of the calculated safety factor, wherein the step of calculating the safety factor includes estimating rock-bed strength of the working face by using a relational expression between drilling data of a rock drill obtained during blast drilling of the working face and the rock-bed strength converted from drilling volume specific energy obtained by using the drilling data, and estimating cohesion in the estimated rock-bed strength of the working face on the basis of a correlation between uniaxial compressive strength and cohesion of a rock, based on the correlation between the uniaxial compressive strength of the rock and the internal friction angle, the internal friction angle in the rock strength of the estimated working face is estimated.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating tunnel face stability. [Background technology]

[0002] Traditionally, the stability of a mountain tunnel's face has been greatly influenced by a variety of factors, including the geology, topography, geological structure, strength, weathering and alteration of the target ground, the state of cracks, and the amount of spring water. For this reason, due to the technical limitations of preliminary surveys and the difficulty of quantitatively assessing stability, it is often not possible to fully evaluate it at the preliminary design stage. Therefore, on-site engineers are required to comprehensively judge the stability of the face based on geological and topographical conditions, as well as the results of observations and measurements made during construction.

[0003] As a method for evaluating face stability near the excavation face, an evaluation method capable of quantitatively grasping face stability based on the state of strength reduction inside the ground ahead of the face, as shown in Patent Document 1, for example, is known. Patent Document 1 describes a method that includes the steps of setting a collapsed area ahead of the face, calculating a safety factor against the sliding of soil mass in the set collapsed area, and judging the stability of the face based on the calculated safety factor, and sets the collapsed area based on a low-energy section near the face of the drilling energy obtained when blasting holes at the face. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-44442 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional face stability evaluation method shown in Patent Document 1, when calculating the slide safety factor of a soil mass, only the friction of the ground is taken into account in calculating the resistance moment acting on the slide surface, and it is assumed that adhesion does not act. Therefore, when calculating the slide safety factor, if adhesion does not act, the resistance force against slide is estimated to be small, which could result in an evaluation result that takes into account too much safety. Furthermore, conventional face stability evaluation methods do not provide detailed methods for setting physical properties such as ground friction used in calculating safety factors. In other words, the physical properties of the ground vary depending on the geological conditions, and it is difficult to set appropriate physical properties when there is no previous measurement data corresponding to the geological conditions in question, so there is room for improvement in this regard.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a tunnel face stability evaluation method that can evaluate the slip safety factor taking into account adhesion and set appropriate physical property values ​​even without previous measurement data, thereby enabling rational stability evaluation. [Means for solving the problem]

[0007] (1) Aspect 1 of the tunnel face stability evaluation method according to the present invention is a tunnel face stability evaluation method for evaluating the stability of a tunnel face, comprising the steps of: setting a collapse area ahead of the face; calculating a safety factor against the sliding of soil mass in the set collapse area; and judging the stability of the face based on the calculated safety factor. The step of calculating the safety factor comprises the steps of: a rock strength estimation step of estimating the rock strength of the face using a relational expression between drilling data of a rock drill obtained during blasting drilling of the face and rock strength converted from the excavation volumetric specific energy obtained using the drilling data; an adhesion estimation step of estimating the adhesion in the rock strength of the face estimated in the rock strength estimation step based on the correlation between the uniaxial compressive strength and adhesion of the rock; and an internal friction angle estimation step of estimating the internal friction angle in the rock strength of the face estimated in the rock strength estimation step based on the correlation between the uniaxial compressive strength and adhesion of the rock.

[0008] The tunnel face stability evaluation method of the present invention allows for quantitative assessment of the stability of the tunnel face based on the deterioration of the natural ground strength ahead of the face. In particular, the safety factor calculation step includes a rock mass strength estimation step, a cohesion estimation step, and an internal friction angle estimation step. The cohesion and internal friction angle can be estimated based on the rock mass strength of the face, which is estimated using a relational equation between the drilling data obtained by a rock drill during blasting drilling at the face and the rock mass strength converted from the drilling volumetric specific energy calculated using the drilling data. The collapse area ahead of the face can be more quantitatively determined by taking these cohesion and internal friction angles into account. Therefore, the stability of the tunnel face can be quantitatively assessed based on the deterioration of the natural ground strength ahead of the face. Since the possibility of a face collapse can be quantitatively indicated, if the safety factor exceeds a predetermined value, workers can be notified of the danger. This allows for preventive measures and evacuation of workers to be implemented quickly before an accident due to a face collapse or other such accident occurs, thereby promoting safer tunnel construction. In this way, the present invention can evaluate the slip safety factor taking into account adhesion, and can set appropriate physical property values ​​even without previous measurement data, allowing for rational stability evaluation.

[0009] (2) Aspect 2 of the present invention is a tunnel face stability evaluation method according to aspect 1, in which, in the rock strength estimation step, formula (1) is used to determine the excavation volumetric specific energy, which is an evaluation index of rock characteristics based on the drilling data, and formula (2) is used to estimate the rock strength of the face from the excavation volumetric specific energy; in the adhesion estimation step, formula (3) is used to estimate the adhesion in the rock strength of the face; and in the internal friction angle estimation step, formulas (4) and (5) are used to estimate the internal friction angle in the rock strength of the face.

[0010]

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[0011]

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[0012]

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[0013] In this case, the rock strength can be efficiently estimated using equations (1) and (2) in the rock strength estimation step, the adhesion can be efficiently estimated using equation (3) in the cohesion estimation step, and the internal friction angle can be efficiently estimated using equations (4) and (5) in the internal friction angle estimation step.

[0014] (3) In aspect 3 of the present invention, in the tunnel face stability evaluation method of aspect 1 or aspect 2, it is preferable that the collapse area is set based on the low-energy section near the face among the drilling energy obtained during blasting drilling at the face.

[0015] In this case, by setting the collapse area from the low-energy section near the face of the drilling energy obtained during blasting and drilling at the face, it is possible to more quantitatively set the collapse area in front of the face based on the state of strength reduction inside the ground, which would be difficult to do by observing the face alone.

[0016] (4) In aspect 4 of the present invention, in the tunnel face stability evaluation method of aspect 1 or aspect 2, it is preferable to divide the soil mass in the collapsed area in the transverse direction of the face and calculate the safety factor against sliding for each divided soil mass.

[0017] In this case, the soil mass in the collapsed area is divided in the transverse direction of the face, and the safety factor against sliding is calculated for each divided soil mass, so that the distribution of the safety factor in the transverse direction can be obtained.

[0018] (5) A fifth aspect of the present invention is preferably the tunnel face stability evaluation method of the first or second aspect, further comprising a step of displaying the safety factor or stability for each location of the face as a distribution map.

[0019] In this case, a step of displaying the safety factor or stability for each location of the face as a distribution map is further provided, so that the safety factor or stability for each location of the face can be notified to workers, etc. [Effects of the Invention]

[0020] According to the tunnel face stability evaluation method of the present invention, it is possible to evaluate the slip safety factor taking into account adhesion, and it is possible to set appropriate physical property values ​​even without previous measurement data, so that a rational stability evaluation can be performed. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a flowchart illustrating a tunnel face stability assessment method according to an embodiment of the present invention. [Figure 2]This is an explanatory diagram of the depth distribution of drilling energy during blasting drilling, where (a) is a mirror view and (b) to (e) are depth distribution diagrams of drilling energy. [Figure 3] FIG. 1 is a vertical cross-sectional view showing an example of a collapsed shape of a tunnel face. [Figure 4] FIG. 1 is a perspective view showing the concept of collapsed soil mass. [Figure 5] FIG. 1 is an explanatory diagram of a method for calculating a slippage safety factor. [Figure 6] FIG. 10 is a flowchart for setting the physical properties of natural ground. [Figure 7] FIG. 1 is a diagram showing the relationship between uniaxial compressive strength and cohesion of rock. [Figure 8] FIG. 1 is a diagram showing the relationship between the uniaxial compressive strength of rock and the angle of internal friction. [Figure 9] FIG. 1 is a diagram showing the relationship between the uniaxial compressive strength of rock and the angle of internal friction. [Figure 10] FIG. 10 is a diagram illustrating an example of a safety factor distribution. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, a tunnel face stability evaluation method according to an embodiment of the present invention will be described with reference to the drawings.

[0023] As shown in FIG. 1, the tunnel face stability evaluation method of this embodiment is an evaluation method for evaluating the stability of a tunnel face.

[0024] The tunnel face stability evaluation method includes step S1 of setting a collapse area ahead of the face, step S2 of calculating the safety factor against the sliding of the soil mass in the set collapse area, step S3 of determining the stability of the face based on the calculated safety factor, and step S4 of displaying the safety factor or stability for each location of the face as a distribution map (see Figure 10).

[0025] In step S1, the collapse area is set based on the low energy section near the face among the drilling energy obtained during blasting drilling at the face.

[0026] The drilling energy is calculated using equation (6) from the mechanical data of the rock drill mounted on a hydraulic jumbo, and is used to evaluate the ground ahead of the tunnel face.

[0027]

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[0028] Figure 2 is an explanatory diagram of the depth distribution of drilling energy during blasting drilling. As shown in Figure 2, there is a common section with low energy values ​​near the wall. This section can be considered to be an area of ​​loosening caused by blasting. Therefore, the collapse area ahead of the face is set based on the low-energy section of drilling energy immediately adjacent to the face. By doing this, it is possible to set the collapse area ahead of the face more quantitatively based on the state of strength reduction inside the ground, which was previously difficult to do by face observation alone.

[0029] Here, the collapsed area refers to the area of ​​the collapsed soil mass that occurs when a sliding collapse of the tunnel face occurs during tunnel excavation. The longitudinal shape of this collapsed area at the center of the tunnel is approximated by a circular arc encompassing the low-energy section immediately adjacent to the tunnel face, as shown in Figure 3, based on previous research (e.g., Non-Patent Document 1 (Mashita Hideto, Suzuki Masahiko, Inokuma Akira: Proposal of a Simple Method for Evaluating Tunnel Face Stability, Transactions of the Japan Society of Civil Engineers, No. 638 / III-49, pp. 117-129, 1999). This arc has a radius R centered at the origin O, originates near the tunnel base, reaches a predetermined depth (e.g., approximately 0.2 to 0.3 times the tunnel diameter) ahead of the tunnel face at the height of the crown, and closes at the height of the crown. The collapsed soil mass is the area of ​​a body of revolution with its axis of rotation parallel to the y-axis, as shown in Figure 4. In addition, when multiple arcs can be set, the one that results in the smallest safety factor will be selected when calculating the slip safety factor described below.

[0030] Assuming that the collapsed shape is arc-shaped in the transverse direction of the tunnel, as shown in Figure 4, the collapsed soil mass in front of the face is separated by a horizontal plane passing through the tunnel crown, and the soil mass below it is set as the collapsed soil mass.

[0031] In step S2, the collapsed soil mass is sliced ​​on the xz plane and divided into multiple soil masses in the transverse direction of the face (see Figure 4), and the slide safety factor is calculated for each divided soil mass, ignoring the transmission of internal forces acting between these divided soil masses. This allows the distribution of safety factors in the transverse direction to be obtained.

[0032] Each divided soil mass is divided into multiple vertical strips (four in Figure 5) as shown in Figure 5. If the weight of vertical strip abcd is W, the angle between the base of vertical strip bc and the horizontal plane is θ, and the area of ​​the base of vertical strip bc is A, then the force attempting to cause sliding is W sinθ and the moment is RW sinθ. In contrast, the resistance moment acting on the slide surface is R(cA + W cosθ tan φ), where c is the adhesive force of the collapsed soil mass and φ is the internal friction angle of the collapsed soil mass. The safety factor Fs of this divided soil mass is calculated using equation (7).

[0033]

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[0034] Next, in step S3, the stability of each divided soil mass is determined based on the calculated safety factor Fs. For example, if the safety factor Fs is less than 1.0, it is determined to be unstable, if it is in the range of 1.0 to 1.2, it is determined to be stable but somewhat unstable, and if it is in the range of 1.3 to 1.4, it is determined to be stable.

[0035] Next, the method for calculating the safety factor Fs in step S2 will be described in more detail. Here, the physical properties of the natural ground required to calculate the safety factor Fs are adhesion and the angle of internal friction. In this embodiment, adhesion c and the angle of internal friction φ are set based on the drilling data of the rock drill mounted on the hydraulic jumbo. Figure 6 is a flowchart for setting the physical properties of the natural ground. As shown in Figure 6, the setting flow estimates the rock strength in step S10, and then, using the rock strength estimated in step S10, estimates adhesion in step S11 and the angle of internal friction in step S12.

[0036] First, we will explain the rock strength estimation method in step S10. Step S10 is a rock strength estimation step in which the rock strength at the face is estimated using a relational equation between drilling data from a rock drill machine obtained during blasting and drilling holes at the face and the rock strength converted from the drilling volumetric specific energy calculated using the drilling data.

[0037] The rock strength of the natural ground is estimated using the relationship between rock drill data and rock strength, based on Non-Patent Document 2 (Yamashita Masayuki, Ishiyama Koji, Kimura Satoshi, Fukui Katsunori, Okubo Seisuke: Study on the Relationship between Long-Distance Drilling Data and Rock Strength, 61st Annual Academic Conference of the Japan Society of Civil Engineers, III-333, pp. 661-662, 2006.). Rock drill data (impact pressure, rotational pressure, thrust, damping pressure, drilling depth, etc.) from the rock drill are measured during blasting at the face. The specific excavation volume energy Ed is calculated as an evaluation index of rock mass properties. The specific excavation volume energy Ed can be expressed by Equation (8).

[0038]

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[0039] In equation (8), Ei is the elastic wave energy generated in the rod by the impact of the piston of the rock drill, and T rod is the transmission coefficient of elastic wave energy in the rod (effect of drilling depth), bpm is the number of blows, and P R is the drilling speed, and A H is the cross-sectional area of ​​the hole.

[0040] Furthermore, the rock strength σc is converted from the excavation volume specific energy Ed using equation (9).

[0041]

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[0042] Here, in equation (9), C is a constant and b is a multiplier. The above-mentioned Non-Patent Document 2 reports that, based on the results of an analysis of measurement data at a tunnel site, b is 0.5 and C is in the range of 20 to 35, with 25 at the center. Based on this, if there is no measurement data on the previous rock strength σc and excavation volume specific energy Ed of the natural ground, σc is calculated using multiplier b = 0.5 and constant C = 25.

[0043] Next, a method for estimating cohesion in step S11 will be described. In step S11, cohesion is estimated based on the rock strength at the tunnel face estimated in the rock strength estimation step (step S10) based on the correlation between the uniaxial compressive strength of rock and cohesion. The cohesion of the ground is estimated using the equation relating the uniaxial compressive strength of rock and cohesion, based on non-patent document 3 on previous research and development of geological disposal (Sugita Yutaka and Yui Sanwa: Dataset of correlation between uniaxial compressive strength of rock and various physical properties, JNC TN8450 2001-010, 2002).

[0044] Figure 7 shows the relationship between uniaxial compressive strength and cohesion of rocks obtained from the basic data set of the hard rock group. In Figure 7, the horizontal axis is uniaxial compressive strength qu (MPa) and the vertical axis is cohesion c (MPa). A correlation equation (c = 0.229qu) was calculated from literature values, average values, and data from Kamaishi (Kurihashi granodiorite) and Tono (Toki granite). 0.868 Based on the correlation equation shown in Fig. 7, we introduce equation (10) as the relation between rock strength σc and cohesion c.

[0045]

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[0046] Here, in equation (10), k is the strength reduction rate in the loosened region. Non-patent document 4 on previous research and development into geological disposal (Goya Mitsuo, Hotta Masakuni, Tada Hiroyuki: Analysis of the impact of tunnel excavation using a crack tensor / virtual fracture model taking into account excavation damage areas (Japan Nuclear Cycle Development Institute contract work report), JNC TJ7400 2004-007, 2004.) summarizes previous investigation cases regarding excavation damage areas in surrounding rock masses caused by cavity excavation, and reports that in excavation impact tests at Kamaishi Mine and Tono Mine, the elastic wave velocity in the loosened areas of the blasting excavation section was about 50% of the elastic wave velocity in the sound part. In addition, in the classification of rock mass for road tunnels, the uniaxial compressive strength qu' of the rock mass, where the effects of cracks and other factors cannot be ignored, is evaluated using the relationship in equation (11) using the elastic wave velocity V1 of the rock mass, the elastic wave velocity V2 of the sample, and the uniaxial compressive strength qu of the sample. In this embodiment, the strength reduction rate k is calculated by referring to the formula (11) and is expressed as (V1 / V2) 2 When this is applied to the correlation equation shown in Figure 7, k = 0.52 = 0.25 is obtained. Therefore, if there is no measurement data on the decrease in elastic wave velocity near existing tunnels in the ground, k = 0.25 is used to find the adhesion force c.

[0047]

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[0048] Next, we will explain the method for estimating the internal friction angle in step S12. Step S12 is an internal friction angle estimation step, in which the internal friction angle at the rock mass strength at the working face estimated in the rock mass strength estimation step (step S10) is estimated based on the correlation between the uniaxial compressive strength of the rock and the internal friction angle. The internal friction angle of the natural ground is estimated using the relational expression between the uniaxial compressive strength of rock and the internal friction angle φ, based on the above-mentioned Non-Patent Document 3 regarding previous research and development on geological disposal.

[0049] Figure 8 shows the relationship between the uniaxial compressive strength and internal friction angle of rocks obtained from the basic data set of the soft rock group. In Figure 8, the horizontal axis is the uniaxial compressive strength qu (MPa) and the vertical axis is the internal friction angle φ (°). The correlation equation (φ = 20.6 + 6.465 log(qu)) was derived from literature values, average values, and data from Tono (Toki granite). Figure 9 shows the relationship between the uniaxial compressive strength and internal friction angle of rocks obtained from the basic data set of the hard rock group. In Figure 9, the horizontal axis represents the uniaxial compressive strength qu (MPa) and the vertical axis represents the internal friction angle φ (°). The correlation equation (φ = 41.3 + 3.733 log(qu)) was derived from literature values, average values, and data from Kamaishi (Kurihashi granodiorite) and Tono (Toki granite). Using the correlation equations shown in Figures 8 and 9 as references, we introduce equations (12) and (13) as the relationship between rock strength σc and the angle of internal friction φ. When rock strength σc is less than 100 MPa, equation (12), which is the correlation equation for the soft rock group, is used, and when σc is 100 MPa or more, equation (13), which is the correlation equation for the hard rock group, is used.

[0050]

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[0051] Next, in the fourth step S4, the safety factors obtained for each divided soil mass are displayed as a distribution map on the image representing the mirror surface. Figure 10 shows an example of a display of a safety factor distribution map, in which the safety factors for each area of ​​the face are color-coded according to their size. This distribution map is displayed in real time on mobile devices such as smartphones carried by construction machine operators and underground workers, and on the display screens of personal computers installed in the on-site station or field office. By looking at the distribution map, each person can quantitatively grasp the possibility of a face collapse. In this way, the safety factors for each area of ​​the face can be notified to workers, etc.

[0052] Next, the operation of the tunnel face stability evaluation method described above will be explained in detail with reference to FIGS. The tunnel face stability evaluation method according to this embodiment evaluates the stability of the tunnel face and includes the steps of step S1 of setting a collapse area ahead of the tunnel face, step S2 of calculating a safety factor Fs against the slide of the soil mass in the set collapse area, and step S3 of determining the stability of the tunnel face based on the calculated safety factor Fs. Step S2 of calculating the safety factor Fs includes a rock strength estimation step (step S10) of estimating the rock strength σc of the face using the relationship between the drilling data of the rock drill machine obtained during blasting and drilling of the face and the rock strength σc converted from the drilling volume specific energy Ed calculated using the drilling data; an adhesion estimation step (step S11) of estimating the adhesion c at the rock strength σc of the face estimated in the rock strength estimation step (step S10) based on the correlation between the uniaxial compressive strength of the rock and the adhesion c; and an internal friction angle estimation step (step S12) of estimating the internal friction angle φ at the rock strength σc of the face estimated in the rock strength estimation step (step S10) based on the correlation between the uniaxial compressive strength of the rock and the internal friction angle φ.

[0053] The tunnel face stability evaluation method according to this embodiment allows quantitative assessment of the stability of the tunnel face based on factors such as the deterioration of the natural ground strength ahead of the face. In particular, in step S2 of calculating the safety factor Fs, the present invention includes a rock mass strength estimation step (step S10), a cohesion estimation step (step S11), and an internal friction angle estimation step (step S12). Based on the rock mass strength σc at the face, which is estimated using a relational equation between the drilling data obtained by the rock drilling machine during blasting drilling at the face and the rock mass strength σc converted from the specific excavation volume energy Ed calculated using the drilling data, the cohesion c and internal friction angle φ can be estimated. Taking these cohesion c and internal friction angle φ into account, the collapse area ahead of the face can be more quantitatively determined. Therefore, the stability of the tunnel face can be quantitatively assessed based on factors such as the deterioration of the natural ground strength ahead of the face. Because the possibility of a face collapse can be quantitatively indicated, it is possible to notify workers and others of the danger when the safety factor Fs exceeds a predetermined value. This allows for preventative measures and evacuation of workers to be carried out quickly before an accident such as a face collapse occurs, allowing tunnel construction to proceed more safely. In this way, in this embodiment, the slippage safety factor Fs can be evaluated taking into account the adhesion force c, and appropriate physical property values ​​can be set even without previous measurement data, making it possible to perform a rational stability evaluation.

[0054] In addition, in this embodiment, in the rock strength estimation step (step S10), the drilling volume specific energy Ed, which is an evaluation index of rock characteristics based on drilling data, is calculated using formula (8), and the rock strength σc of the rock face is estimated from the drilling volume specific energy Ed using formula (9).In the adhesion estimation step (step S11), the adhesion c in the rock strength of the rock face is estimated using formula (10).In the internal friction angle estimation step (step S12), the internal friction angle φ in the rock strength σc of the rock face is estimated using formulas (12) and (13). By using this method, the rock strength σc can be efficiently estimated using equations (8) and (9) in the rock strength estimation step (step S10), the cohesion c can be efficiently estimated using equation (10) in the cohesion estimation step (step S11), and the internal friction angle φ can be efficiently estimated using equations (12) and (13) in the internal friction angle estimation step (step S12).

[0055] In addition, in this embodiment, the collapse area is set based on the low-energy section near the face among the drilling energy obtained during blasting drilling at the face. By configuring it in this way, the collapse area can be set from the low-energy section near the face of the drilling energy obtained during blasting and drilling at the face, making it possible to more quantitatively set the collapse area in front of the face based on the state of strength reduction inside the ground, which was difficult to do by observing the face alone.

[0056] In addition, in this embodiment, the soil mass in the collapsed area is divided in the transverse direction of the face, and the safety factor Fs against sliding is calculated for each divided soil mass. By configuring it in this way, the soil mass in the collapsed area is divided in the transverse direction of the face, and the safety factor Fs against sliding is calculated for each divided soil mass, so that the transverse distribution of the safety factor Fs can be obtained.

[0057] Moreover, this embodiment further includes step S4 of displaying the safety factor Fs or stability for each location of the face as a distribution map. By configuring in this manner, it is further provided with step S4 of displaying the safety factor Fs or stability for each location of the face as a distribution map, so that the safety factor or stability for each location of the face can be notified to workers, etc.

[0058] As described above, the tunnel face stability evaluation method according to this embodiment can evaluate the slip safety factor taking into account adhesion, and can set appropriate physical property values ​​even without previous measurement data, making it possible to perform a rational stability evaluation.

[0059] The above describes an embodiment of the tunnel face stability evaluation method according to the present invention, but the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the spirit of the present invention.

[0060] For example, in the above embodiment, the tunnel face stability evaluation method was explained using an example in which the shape of the collapsed area was approximated by a circular arc, but the present invention is not limited to this, and other shapes may be used for approximation. For example, depending on the occurrence of low-energy sections in drilling energy, approximation may be used by other curves such as a logarithmic spiral. This method can also achieve the same effects as those described above. Furthermore, while only frictional force was considered as the strength characteristic of the slide surface, the present invention is not limited to this, and effects such as adhesion force may also be considered depending on the mechanical characteristics of the ground. This method can also achieve the same effects as those described above.

[0061] The tunnel face stability evaluation method according to the above embodiment may be realized using a face stability evaluation device. That is, the face stability evaluation device may include a setting means for setting a collapse area ahead of the face, a calculation means for calculating a safety factor against the sliding of a soil mass in the set collapse area, a determination means for determining the stability of the face based on the calculated safety factor, and a display means for displaying a distribution map of the safety factors for each location of the face, and the calculation means may further include a rock strength estimation means for estimating the rock strength of the face using a relational expression between drilling data obtained by a rock drill machine during blasting drilling at the face and the rock strength converted from the drilling volumetric specific energy calculated using the drilling data, an adhesion estimation means for estimating the adhesion at the rock strength at the face estimated by the rock strength estimation means based on the correlation between the uniaxial compressive strength and adhesion of the rock, and an internal friction angle estimation means for estimating the internal friction angle at the rock strength at the face estimated by the rock strength estimation means based on the correlation between the uniaxial compressive strength and adhesion of the rock.

[0062] In this case, the setting means can be configured using an arithmetic device such as a computer that performs the processing of step S1 above, and a storage device that stores data on the depth distribution of drilling energy during blasting. The calculation means can be configured using an arithmetic device such as a computer that performs the processing of step S2 above. The determination means can be configured using an arithmetic device such as a computer that performs the processing of step S3 above. The display means can be configured using an arithmetic device such as a computer that performs the processing of step S4 above, and an output device such as a display.

[0063] In addition, the components in the above-described embodiments can be replaced with well-known components as appropriate, without departing from the spirit of the present invention.

Claims

1. A tunnel face stability evaluation method for evaluating face stability, comprising: setting a collapse area ahead of the face; A step of calculating a safety factor against sliding of the soil mass in the set collapse area; and determining the stability of the tunnel face based on the calculated safety factor; The step of calculating the safety factor includes: a rock strength estimation step of estimating the rock strength of the face using a relational equation between the drilling data of the rock drill machine obtained during blasting and drilling of the face and the rock strength converted from the drilling volume specific energy calculated using the drilling data; an adhesion strength estimation step of estimating adhesion strength at the rock mass strength of the face estimated in the rock mass strength estimation step based on a correlation between uniaxial compressive strength and adhesion strength of rock; an internal friction angle estimation step of estimating the internal friction angle at the rock mass strength of the face estimated in the rock mass strength estimation step based on the correlation between the uniaxial compressive strength of the rock and the internal friction angle; A method for evaluating the face stability of a tunnel equipped with a

2. In the rock strength estimation step, the drilling volume specific energy, which is an evaluation index of rock characteristics based on the drilling data, is calculated using formula (1), and the rock strength of the face is estimated from the drilling volume specific energy using formula (2); In the adhesion force estimation step, the adhesion force in the rock strength of the face is estimated using Equation (3), 2. The tunnel face stability evaluation method according to claim 1, wherein in the internal friction angle estimation step, the internal friction angle in the rock strength of the face is estimated using formulas (4) and (5). [Equation 1] [Equation 2] [Equation 3]

3. 3. A tunnel face stability evaluation method according to claim 1 or 2, wherein the collapse area is set based on a low-energy section near the face among the drilling energy obtained during blasting drilling at the face.

4. 3. The tunnel face stability evaluation method according to claim 1, wherein the soil mass in the collapsed area is divided in a transverse direction of the face, and the safety factor against sliding is calculated for each divided soil mass.

5. 3. A tunnel face stability evaluation method according to claim 1 or 2, further comprising a step of displaying the safety factor or stability for each face location as a distribution map.

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