JP2001194112A - Alarm method and apparatus for displacement of tunnel working face - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow workers to safely make refuge by quantitatively and surely determining the condition of displacement of a tunnel working face, and issuing an alarm based on an objective criterion. SOLUTION: A control part 13 is connected to a laser range finder 12 to obtain displacement data D1 showing the amount of displacement at each of observation points 1 to 5 set at the working face 22 of the tunnel 21. Based on the displacement data D1, a determining part 14 determines whether or not there is a sign indicative of the danger of collapse of the natural ground. When any sign indicative of the danger is determined to arise, a determination output signal S1 is output to actuate a red rotating lamp device 15A to thereby output an alarm to the workers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for alerting a worker to a displacement of a tunnel face when a displacement amount generated in the tunnel face during excavation of the tunnel exceeds a dangerous level.

[0002]

2. Description of the Related Art In order to ensure the safety of workers in tunnel face work, the displacement state of the tunnel face is grasped during the work, and when there is a sign indicating a danger such as collapse, the worker is notified of the sign and evacuation etc. Appropriate measures need to be taken.
For this reason, in the related art, for example, an experienced worker visually observes the tunnel face and the surrounding ground conditions and makes a fall prediction from his own experience, based on a visual prediction of an experienced person, or based on a mirror. Evacuation alerts were issued to workers based on qualitative observations by observing the occurrence of cracks and the progress of cracks in shotcrete.

[0003]

However, since the above-mentioned conventional method relies on human experience and intuition in any case, the judgment of collapse prediction differs from person to person, and the safety of the worker is ensured. There was a problem in terms of reliability to achieve. Another problem is that in a large-section tunnel, the visual distance of the ground to be observed is long, making it difficult to visually detect minute displacements at the tunnel face, making it difficult to accurately predict collapse. Also have.

SUMMARY OF THE INVENTION It is an object of the present invention to quantitatively and reliably grasp the displacement state of a tunnel face, determine the occurrence of a displacement of the tunnel face indicating a danger such as collapse by an objective criterion, and issue an alarm, It is an object of the present invention to provide a tunnel face displacement alarm method and apparatus capable of safely evacuating a worker.

[0005]

In order to solve the above-mentioned problems, in the present invention, the displacement of the tunnel face is detected by laser distance measurement using a laser distance meter or the like, and the detection result indicates the occurrence of danger such as collapse. When a sign is obtained, an alarm is issued, thereby making it possible to ensure the safety of the worker.

In order to solve the above problems, according to the present invention, there is provided a tunnel face displacement warning method for issuing a warning when a sign of danger such as collapse of the ground occurs on the tunnel face. A step of obtaining each displacement amount at a plurality of set observation points by laser ranging; a discrimination step of discriminating whether or not a sign indicating occurrence of danger such as collapse of the ground has appeared based on the displacement amount; Outputting a warning to an operator when it is determined in response to the step that the sign indicating occurrence of the danger has appeared.

[0007] The displacement obtained by the laser distance measurement is compared with a predetermined reference value, and it is possible to determine the presence or absence of a sign of danger such as collapse of the ground based on the comparison result. The determination may be made by a method.

According to the present invention, there is also provided a tunnel face displacement warning method for issuing a warning when a sign of danger such as collapse of the ground or the like occurs on the tunnel face, wherein a plurality of tunnel faces are set. A setting step of obtaining a distance to an observation point by laser ranging and setting an initial value for each of the plurality of observation points, and obtaining each distance to the plurality of observation points by laser ranging, and considering the initial value. Calculating the amount of displacement for each of the plurality of observation points, and comparing the amount of displacement with a predetermined reference value to determine the presence or absence of a sign indicating a danger such as collapse of the ground at the plurality of observation points. A tunnel face displacement warning method is proposed, comprising: a discriminating step; and a step of issuing a warning when it is determined in the discriminating step that the sign indicating the danger is present.

[0009] The calculation step and the determination step may be repeatedly executed until it is determined in the determination step that the sign of danger is present.

The method may further include a step of determining whether each of the displacement amounts is less than a predetermined error limit value. If the displacement amount is equal to or greater than the predetermined error limit value, the determination step indicates that the danger occurs. Even if it is determined, it may be configured to ignore this determination.

In the determining step, it is configured to determine the presence or absence of the danger sign at the plurality of observation points by comparing a displacement amount corresponding to each of the plurality of observation points with a predetermined reference value. You can also. Here, the predetermined reference value may be separately set for each of the plurality of observation points.

According to the present invention, there is further provided a tunnel face displacement warning method for issuing a warning when a sign of danger such as collapse of the ground occurs on the tunnel face, wherein a plurality of tunnel faces are set. A setting step of obtaining each distance to an observation point by laser ranging and setting an initial value for each of the plurality of observation points, and obtaining a distance to any one of the plurality of observation points by laser ranging. A step of sequentially executing processing for determining the presence or absence of a sign of danger occurrence at the observation point by comparing the distance with a corresponding value of the initial value for all of the plurality of observation points; and Issuing a warning when it is determined that there is a sign of occurrence of the danger in any one of the tunnel face displacement alarm methods.

According to the present invention, there is also provided a tunnel face displacement alarm device for issuing a warning when a sign of danger such as collapse of the ground or the like occurs on the tunnel face, comprising: a laser range finder; a tunnel face; Control means connected to the laser range finder to obtain displacement amount data indicating each displacement amount at the plurality of observation points set in the laser range finder, based on the displacement amount data Discriminating means for discriminating whether a sign indicating a danger of collapse has appeared, and an alarm for outputting an alarm to an operator in response to the discriminating means when it is determined that the sign indicating the danger has appeared. A device comprising the device is proposed.

The laser distance measuring method for obtaining the displacement of the tunnel face may be arbitrary. However, if a method capable of measuring the distance without using a target such as a reflector is adopted, the work approaching the face is minimized. It is preferable because the advantage that it can be obtained can be obtained.

As the laser range finder, a commercially available laser range finder having a known configuration can be used, and the control means is provided to a personal computer connected to the laser range finder having such a known configuration to obtain required change amount data. It is also possible to adopt a configuration in which a program for automatically and continuously performing the measurement operation is set. Further, the function of the determination means may be incorporated as software in the personal computer. in this case,
The displacement amount data obtained by laser ranging can be compared with predetermined reference data, and based on the comparison result, it can be determined whether there is any sign of danger of land collapse, but it can be determined by another appropriate method. May be performed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic structural view showing an example of an embodiment of a tunnel face displacement alarm device according to the present invention. A tunnel face displacement alarm device 11 is configured to displace a tunnel face at a predetermined observation point by laser distance measurement. The system is configured such that the situation is grasped, and if it is determined that a sign indicating danger such as collapse has occurred based on the displacement state, a warning is issued to the worker and the worker is evacuated.

The tunnel face displacement warning device 11 includes a laser range finder 12 and a laser range finder for obtaining the displacement of each tunnel face at a plurality of observation points set on the tunnel face using the laser range finder 12. A control unit 13 for controlling the meter 12 and processing the distance measurement output from the laser distance meter 12 to output displacement data D1 indicating the state of displacement of the face.
And a discriminating unit 14 for discriminating, based on the displacement amount data D1 output from the control unit 13, whether or not a sign indicating a danger of collapse of the ground has appeared. When it is determined that a sign indicating danger has appeared, a determination output signal S1 is output from the determination unit 14 and input to the alarm device 15.

The alarm device 15 comprises a red rotating light device 15A. When the discrimination output signal S1 is inputted, the red rotating light device 15A is activated, and a warning can be given to an operator by light. I have. However, the alarm device 1
The configuration of No. 5 is not limited to this, and may be an appropriate configuration such as adding a siren device.

In the illustrated embodiment, the control section 13 and the discriminating section 14 are housed together in a control box 16, and the alarm device 15 connected to the control box 16 by a cable is located at an appropriate position where it is easy to see. It can be installed (see FIG. 2). The control box 16 and the laser range finder 12 can be connected to each other by a cable 17 as needed, so that they are easy to carry and set.

FIG. 2 is a diagram showing a schematic configuration in a case where the tunnel face displacement alarm device 11 shown in FIG. 1 is set in the tunnel 21 during excavation and a displacement alarm of the face 22 of the tunnel 21 is issued. FIG. 3 is a view when the face 22 shown in FIG. 2 is viewed from behind the tunnel face displacement alarm device 11.

Referring to FIGS. 2 and 3, a description will be given of an example of a case where the displacement warning of the face 22 is performed by the tunnel face displacement warning device 11. FIG.

First, primary spraying in the tunnel 21 is performed,
After setting the support erector truck, the tunnel face displacement alarm device 11 is installed on the board surface 21A of the tunnel 21 at an appropriate distance from the face 22.

Here, the laser beam LA from the laser range finder 12 is firmly used by using the tripod 12A of the laser range finder 12 so that the laser beam LA from the laser range finder 12 can be irradiated on a plurality of predetermined observation points 1 to 5 on the face 22. The range finder 12 is installed on the board surface 21A. At this time, the control box 16 is placed near the laser range finder 12, and the laser range finder 12 and the concrete box 16 are electrically connected by the cable 17. Then, the control box 16 and the alarm device 1
5 and the alarm device 15 is installed at a position where the worker can easily notice. The tunnel face displacement alarm device 11 includes:
The required DC power is supplied from a battery (not shown).

Here, the observation points 1 to 5 can be selected at appropriate points such as a top, a shoulder, or a bad mountain position, and the number of observation points is not limited to the five shown in FIG. can do.

Thereafter, the laser beam LA is sequentially emitted from the laser range finder 12 to the observation points 1 to 5 by the control operation of the control unit 13, whereby the displacements at the observation points 1 to 5 are continuously measured. I do. This displacement measurement can be easily obtained from the temporal change of the distance to each of the observation points 1 to 5 measured by the laser range finder 12. In this way, the control unit 13 calculates the displacement data D1 indicating the displacement at each of the observation points 1 to 5, and the displacement data D1 is calculated by the determination unit 14
Is input to

The determination section 14 determines whether or not the displacement amount at each of the observation points 1 to 5 exceeds a predetermined level based on the displacement amount data D1. When it is determined that the displacement amount exceeds the predetermined level at at least one of the observation points 1 to 5, the determination unit 14 outputs a determination output signal S1 indicating that there is a high risk of the tunnel 21 collapsing. Is done.

In this case, the predetermined level is determined at each of the observation points 1 to
A unique value is set every five. This makes it possible to perform a risk determination suitable for the characteristics of each observation point, and thereby to perform a risk prediction of the collapse of the face 22 with high accuracy. Of course, the same predetermined level can be set for each of the observation points 1 to 5.

In this manner, each of the observation points 1 to
5 is calculated as the amount of displacement in any one of the cases 5, but when the displacement exceeds the allowable value, the discrimination output signal S1 is output, and the alarm device 15 responds to this, the red rotating light device 5A operates, and the worker in the tunnel 11 Can be surely notified of the danger of the face 22 collapsed, and promptly evacuating from the tunnel 21 by light.

When the heavy equipment is operated in the tunnel 21, the displacement of each of the observation points 1 to 5 of the face 22 may be greatly changed. Therefore, the determination unit 14 can be configured to ignore a large displacement amount (a value exceeding the error limit value) caused by the operation of the heavy equipment. Also,
Since the same situation occurs when the lock bolt is applied, the same measures can be taken in this case.

As described above, according to the tunnel face displacement alarm device 1, the displacement amounts of the plurality of observation points 1 to 5 of the face 22 are measured using the laser light from a place far from the face 22; Since the risk of collapse is determined from this measurement result and an alarm is output, the ground displacement state of the face 22 can be grasped more accurately than in an empirical method such as visual inspection, and evacuation is performed because the state judgment is quick. Such instructions can be issued early, and the safety of the worker can be ensured. In addition, even when the distance to the tunnel face is long, such as a large-section tunnel, the laser beam is used, so it is possible to reliably capture even small displacements that cannot be detected by visual observation at the tunnel face. This makes it possible to predict the collapse with higher accuracy, which can significantly contribute to ensuring work safety.

Further, since a commercially available existing product can be used as the laser range finder 12, the cost is relatively low and replacement at the time of repair is easy. Further, since the power uses a portable battery, it can be used alone even in a place where facilities are not provided.

The control unit 16 shown in FIG.
For example, the above-described functions can be realized by setting and executing a required program on a personal computer or the like.

FIG. 4 is a flowchart showing an example of such a program. The operation according to this program will be described with reference to FIG. First, step 31
Then, setting data indicating each set value of the measurement time interval, the allowable value K of the displacement amount at each observation point of the face 22, and the error limit value E are input. This setting data can be input from an input device (not shown) of the personal computer.

In the next step 32, the initial values L1 to L5 of the observation points 1 to 5 are set.

FIG. 5 is a flowchart showing the details of the process in step 32. First, in step 41, the value of the data N indicating the observation point is set to 1, and in step 42, the distance to the observation point N (= 1) is
And at step 43 this observation point N (=
The measurement distance up to 1) is set as an initial value LN (= L1).

In step 44, it is determined whether or not N ≧ 5. Here, since N = 1, the result of the determination in step 44 is NO, and the value of N is increased by 1 in step 45, and the process returns to step 42 with N = 2. Then, the processing in steps 42 and 43 is executed for N = 2, and an initial value L2 for observation point 2 is set.

Thereafter, if the initial values L3, L4, and L5 for the observation points 3, 4, and 5 are set by the same repetition, N = 5. Therefore, the determination result in the step 44 becomes YES, and the step 32 becomes YES. Is completed.

Returning to FIG. 4, when the process of step 32 is completed, the process proceeds to step 33, where the displacement amounts of the observation points 1 to 5 are calculated.

The calculation of the displacement of each of the observation points 1 to 5 in step 33 will be described with reference to FIG. 6. First, in step 51, the value of the data N indicating the observation point is set to 1, and in step 52, the observation point is set. The distance to N (= 1) is measured by the laser range finder 12. In step 53, the measurement distance DN to this observation point N (= 1) and its initial value L
1 is calculated as a displacement amount ΔDN (= ΔD1), and the displacement amount ΔD1 is stored in a memory (not shown) as the current displacement amount at the observation point 1 (step 54).

In step 55, it is determined whether or not N ≧ 5. Here, since N = 1, the result of the determination in step 55 is NO, the value of N is increased by 1 in step 56, and the process returns to step 52 with N = 2. Then, the processing in steps 52, 53, and 54 is executed for N = 2, and the displacement amount ΔD2 for observation point 2 is obtained and stored in the memory.

Thereafter, similarly, when the displacement amounts D3, D4, D5 for the observation points 3, 4, 5 are calculated and stored in the memory, N = f.
Is YES, the process of step 33 ends, and the process proceeds to step 34.

Returning to FIG. 4, at step 34, at least one of the displacement amounts ΔD1 to D5 stored at step 54 is set.
It is determined whether or not one of them is equal to or more than the allowable value K. Displacement Δ
If all of D1 to D5 are smaller than the allowable value K, step 3
The determination result of No. 4 is NO, and it is determined that there is no danger sign of collapse of the face 22, and the process returns to Step 33, and the calculation of the displacement amount of the face 22 is executed again.

In this way, the time elapses and the displacement Δ
When at least one of D1 to D5 is equal to or more than the allowable value K,
The determination result in the step 34 is YES, and the step 35
to go into.

In step 35, it is determined whether or not the displacement determined to be equal to or larger than the allowable value in step 34 is smaller than the error limit value E. If the displacement amount is equal to or greater than the error limit value E, the displacement amount is determined to be a displacement amount that is not a sign of face collapse caused by the influence of the operation of the heavy equipment and the construction of the lock bolt. The determination result is NO and the process returns to step 33. In other words, for a displacement amount equal to or larger than the error limit value E, even if it is determined in step 34 that there is a sign of danger such as collapse of the ground, this determination is ignored. On the other hand, if it is determined in step 35 that the displacement amount is less than the error limit value E, it is determined that the displacement amount indicates a sign of face collapse, the determination result in step 35 becomes YES, and step 36 , Where the discrimination output signal S1 is output.

In the above description, the determination in step 34 is such that all the displacement amounts ΔD1 to D5 are compared with the allowable value K to determine whether or not there is a sign of collapse of the face 22. However, the determination is different for each observation point. It is also possible to set the allowable values K1 to K5 and determine the sign of face collapse at each observation point with an allowable value suitable for the observation point, so that a more accurate alarm can be issued.

As described above, referring to FIGS.
Although an example of the specific configuration of the determination unit 14 has been described, the present invention is not limited to this specific configuration.

FIG. 7 is a flowchart showing a specific configuration example of another program for realizing the functions achieved by the control unit 13 and the determination unit 14 shown in FIG. 1 using a personal computer. I have. In the flowchart shown in FIG. 7, Steps 61 and 62 are the same as Steps 31 and 32 shown in FIG. 4, and the details of the processing of Step 62 are as shown in FIG. Therefore, detailed description of steps 61 and 62 will be omitted.

In step 63, referring to the initial values L1 to L5 set in step 62, the observation points 1 to 5
Are calculated, and the sign of the face collapse is determined based on these.

FIG. 8 shows a detailed flowchart of step 63. The processing in step 63 will be described with reference to FIG. 8. First, in step 71, the value of the data N indicating the observation point is set to 1, and in step 72, the distance to the observation point N (= 1) is measured by laser ranging. It is measured by a total 12. In step 73, the measurement distance DN (= D1) to this observation point N (= 1) and its initial value LN (= L
1) is calculated, and the difference ΔDN (= ΔD1) is calculated.
(= L1−D1) is obtained as the current displacement amount at the observation point 1.

In step 74, it is determined whether or not the value of the displacement amount ΔD1 obtained in step 73 is equal to or larger than the allowable value K. Here, if the value of the displacement amount ΔD1 is smaller than the allowable value K, the determination result of step 34 is NO, and
It is determined that there is no sign of collapse at observation point 1 of 2, and the process proceeds to step 75.

At step 75, a process for increasing the value of N by 1 is performed. At step 76, it is determined whether or not N> 5. If N> 5, the decision result in the step 76 is NO.
Then, the process returns to step 72, and the calculation of the displacement amount ΔD2 at the observation point 2 and the presence or absence of a sign of collapse at the observation point 2 are determined in the same manner as in the previous case.

In this manner, the presence or absence of a sign of collapse at the observation points 3, 4, and 5 is sequentially determined. Then, after it is determined whether or not the observation point 5 has a sign of collapse, step 7 is performed.
5 and N = 6, the result of the determination in step 76 is YE
S, and N = 1 in step 77, and then step 7
Return to 2. As a result, the presence or absence of a sign of collapse at the observation points 1 to 5 is sequentially determined again.

When the time has elapsed in this way and the displacement Di at any one of the observation points i is equal to or larger than K, the determination result in the step 74 becomes YES and the process proceeds to a step 78.

In step 78, it is determined whether the displacement ΔDi is less than the error limit value E. If the displacement amount ΔDi is equal to or larger than the error limit value E, the displacement amount ΔDi is determined to be a displacement amount that does not become a sign of face collapse caused by the operation of the heavy equipment or the construction of the lock bolt, and the process proceeds to step 78. The determination result is NO and the process proceeds to step 78, in which the next observation point collapse sign determination is performed.

On the other hand, if it is determined in step 78 that the displacement amount ΔDi is less than the error limit value E, the displacement amount ΔD
It is determined that i indicates a sign of face collapse, and the result of the determination in the step 78 is YES, the process proceeds to a step 79, where a determination output signal S1 is output.

In the above description, the determination in step 74 is such that the displacement amounts ΔD1 to D5 are all compared with the permissible value K to determine the exemption of face collapse. However, the permissible value K1 that differs for each observation point is determined. ＫK5 may be set, and a sign of face collapse may be determined for each observation point at an allowable value suitable for the observation point, so that a more accurate warning may be issued.

[0058]

According to the present invention, the displacement of a predetermined observation point of a face is measured using a laser beam from a place far away from the face, the risk of collapse is determined from the measurement result, and an alarm is issued. Since the output is made, compared to the conventional method that relies on experience by visual observation, etc., it is possible to accurately grasp the ground displacement state of the face, and the situation judgment is fast, so that instructions such as evacuation can be issued earlier, Can ensure the safety of people. In addition, even when the distance to the tunnel face is long, such as a large-section tunnel, the laser beam is used, so it is possible to reliably capture even small displacements that cannot be detected by visual observation at the tunnel face. This makes it possible to predict the collapse with higher accuracy, which can significantly contribute to ensuring work safety. In addition, existing products on the market can be used for laser ranging, so it is relatively inexpensive and easy to replace for repair, and the power is not fully equipped because a portable battery can be used It has the advantage that it can be used alone in a place.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of an embodiment of a tunnel face displacement alarm device according to the present invention.

FIG. 2 is a schematic configuration diagram showing a schematic configuration in a case where a tunnel face displacement alarm device is installed in a tunnel to perform a tunnel face displacement alarm using the tunnel face displacement alarm device shown in FIG. 1;

3 is an elevation view of the tunnel face when the face shown in FIG. 2 is viewed from the rear of the tunnel face displacement alarm device.

FIG. 4 is a flowchart showing an example of a program for configuring the control unit shown in FIG. 1 using a computer.

FIG. 5 is a detailed flowchart of an initial value setting step in FIG. 4;

FIG. 6 is a detailed flowchart of a displacement calculating step in FIG. 1;

7 is a flowchart showing an example of another program for configuring the control unit shown in FIG. 1 using a computer.

FIG. 8 is a detailed flowchart of a displacement amount calculation and collapse sign determination step in FIG. 7;

[Description of Signs] 11 Tunnel face displacement alarm device 12 Laser range finder 13 Control unit 14 Discrimination unit 15 Alarm device 15A Red rotating light device 21 Tunnel 22 Face D1 Displacement amount data LA Laser light S1 Discrimination output signal

Claims (8)

[Claims] 1. A tunnel face displacement warning method for issuing a warning when a sign of danger such as collapse of the ground occurs on a tunnel face, wherein each displacement amount at a plurality of observation points set on the tunnel face. Obtaining by laser distance measurement, determining whether or not a sign indicating occurrence of danger such as collapse of the ground has appeared based on the displacement amount; and indicating the occurrence of danger in response to the determination step. Outputting a warning to the worker when it is determined that the tunnel face has appeared. 2. A tunnel face displacement warning method for issuing a warning when a sign of danger such as collapse of the ground occurs on the tunnel face, wherein a distance to a plurality of observation points set on the tunnel face is determined. Setting step of setting an initial value for each of the plurality of observation points obtained by laser ranging, obtaining each distance to the plurality of observation points by laser ranging, and taking the initial values into account, for the plurality of observation points A calculating step of calculating an amount of displacement for each; a determining step of comparing the amount of displacement with a predetermined reference value to determine whether or not there is a sign indicating occurrence of danger such as collapse of the ground at the plurality of observation points; Issuing a warning when it is determined that there is a sign indicating the occurrence of danger in the step. 3. The method according to claim 2, wherein the calculating step and the determining step are repeatedly performed until it is determined in the determining step that the sign of danger is present.
Tunnel face displacement alarm method described. 4. The method according to claim 1, further comprising the step of determining whether each of the displacement amounts is less than a predetermined error limit value. 3. The tunnel face displacement warning method according to claim 2, wherein even if it is determined that there is, the determination is ignored. 5. In the determining step, the presence or absence of the sign of danger occurrence at the plurality of observation points is determined by comparing a displacement amount corresponding to each of the plurality of observation points with a predetermined reference value. 3. The method for alarming displacement of a tunnel face according to claim 2. 6. The tunnel face displacement warning method according to claim 5, wherein the predetermined reference value is set separately for each of the plurality of observation points. 7. A tunnel face displacement warning method for issuing a warning when a sign of danger such as collapse of the ground occurs on the tunnel face, wherein each distance to a plurality of observation points set on the tunnel face is provided. Setting the initial value for each of the plurality of observation points by laser ranging, obtaining the distance to any one of the plurality of observation points by laser ranging, and setting the initial value to the distance. Sequentially executing, for all of the plurality of observation points, a process of determining the presence or absence of a sign of danger occurrence at the observation point by comparing with the corresponding value of the danger occurrence point. Issuing a warning when it is determined that there is a sign of the tunnel face displacement alarm method. 8. A tunnel face displacement warning device for issuing a warning when a sign of danger such as collapse of the ground occurs on the tunnel face, comprising: a laser range finder; Control means connected to the laser range finder to obtain displacement amount data indicating each displacement amount at the observation point using the laser range finder; and occurrence of danger such as collapse of the ground based on the displacement amount data. Determining means for determining whether a sign indicating the occurrence of a danger is provided, and an alarm device for responding to the determining means and outputting an alarm to an operator when it is determined that the sign indicating occurrence of the danger has appeared. A tunnel face displacement alarm device, characterized in that: