JP4883405B2 - Correlation curve creation method, drilling speed correction method, ground mountain division evaluation table creation method and face front prediction method - Google Patents

Description

  The present invention mainly relates to a correlation curve creation method, a drilling speed correction method, a creation method of a natural ground segment evaluation table, and a forward face prediction method employed when excavating a natural ground of a mountain tunnel.

  When excavating a mountain tunnel, grasping the nature of the natural ground spreading ahead of the face with appropriate and high accuracy is very important for efficiently and safely proceeding with the entire excavation work including supporting works and auxiliary works. Drilling exploration by non-core drilling is widely known as a technique for conducting forward exploration of the tunnel face.

In drilling exploration, when drilling in front of the tunnel face, the drilling speed, impact pressure, rotational pressure, feed pressure, damping pressure, etc. are acquired as drilling data, and the drilling energy is obtained from the drilling data by the following equation:
Drilling energy = {blow energy × number of hits / (drilling speed × hole cross-sectional area)}

X It is a method of calculating the natural condition (rock mass grade) by calculating the loss factor and using the magnitude of the drilling energy.

  In such a method, since the drilling speed depends on the feed pressure, that is, the pressure that presses the rock drill rod against the natural ground, the feed pressure is made constant in order to objectively evaluate the natural ground from the drilling energy. There is a need.

Japanese Patent No. 3380795

  However, depending on the natural ground, it is difficult to maintain the feed pressure constant, and the natural ground cannot be objectively evaluated from the drilling energy.

  In order to solve this problem, a method has been proposed to remove the influence of fluctuations in feed pressure on drilling energy in the form of feed pressure correction, and then evaluate the natural ground, but it has not yet gone out of research. .

  In any case, the forward exploration technology using non-core drilling uses physical data from a rock drill, but the results obtained from data processing are not reliable in terms of accuracy, and empirical judgments are made. It is the current situation that remains only the above materials.

  The present invention has been made in consideration of the above-described circumstances, and a correlation curve creation method capable of reflecting the fluctuation of the feed pressure on the drilling speed, a drilling speed correction method using the same, and the same were used. It is an object of the present invention to provide a face front prediction method capable of accurately predicting a natural ground ahead of a face using a method for creating a natural ground section evaluation table, a modified drilling speed, and a natural ground section evaluation table.

In order to achieve the above object, according to the correlation curve creating method of the present invention, as described in claim 1, a natural ground is drilled with a drilling means such as a rock drill or the like at the first drilling site. It measures the feed pressure F ₁ and the drilling speed V ₁ of the time, and a variation amount [Delta] V ₁ of the boring speed V ₁ by regression analysis corresponding to the variation amount and the variation amount [Delta] F ₁ of the feed pressure F ₁ Thus, a correlation curve is created.

Moreover, the drilling speed correcting method according to the present invention, as described in claim 2, drills a natural ground with a drilling means such as a rock drill at the second drilling site and feed pressure at the time of drilling. Measure F ₂ and drilling speed V ₂ ,

By applying said difference [Delta] F ₂ calculates the difference [Delta] F ₂ from a reference feed pressure of the feed pressure F ₂ in the correlation curve of claim 1, wherein calculating the variation amount [Delta] V ₂ of the boring speed V ₂ ,

The modified drilling speed V _R is calculated by adding or subtracting the fluctuation amount ΔV ₂ to or from the drilling speed V ₂ .

In addition, the method for creating the natural ground section evaluation table according to the present invention normalizes the modified drilling speed V _{R according} to claim 2 so that their values are 0 to 1, as described in claim 3. To calculate the normalized drilling speed ratio V _N ,

The ground drilling section evaluation table is created by associating the normalized drilling speed ratio V _N and the variation thereof with the ground drilling section at the second drilling site.

Further, according to the method for predicting the face ahead according to the present invention, the ground pressure is drilled by a drilling means such as a rock drill at the third drilling site and the feed pressure F at the time of drilling is set forth. ₃ and the drilling speed V ₃

It calculates the difference [Delta] F ₃ from the reference feed pressure of the feed pressure F _3,

The difference [Delta] F _3, by applying the correlation curve of claim 1, wherein calculating the variation amount [Delta] V ₃ of the drilling speed V _3,

A corrected drilling speed V _R is calculated by adding or subtracting the fluctuation amount ΔV ₃ to the drilling speed V ₃ ;

The corrected drilling speed V _R is normalized so that their values are 0 to 1, and a normalized drilling speed ratio V _N is calculated,

By applying the normalized drilling speed ratio V _N and the variation thereof to the ground level evaluation table according to claim 3, the ground level classification at the third drilling site is estimated.

  In conducting forward exploration using physical data obtained by non-core drilling, the applicant has a correlation between the fluctuation amount ΔF of the feed pressure F and the fluctuation amount ΔV of the drilling speed V, and R & D focusing on the fact that this correlation does not depend on the feed pressure F and the drilling speed V, and that a new forward exploration method could be established based on this correlation. As a result, regression analysis was performed from the above-described correlation to create a correlation curve, and the fluctuation amount ΔV of the drilling speed V was calculated by applying the feed pressure fluctuation amount ΔF to the correlation curve. The drilling speed was successfully corrected in consideration of the fluctuation of the feed pressure.

That is, in the correlation curve generating method according to claim 1, first, the ground is drilled by a drilling means such as a rock drill at the first drilling site, and the feed pressure F ₁ and the drilling at the time of drilling are drilled. to measure the speed V _1.

  For example, a rock drill widely used under the name of a hydraulic jumbo can be used as the hole drilling means. In such a case, if measurement is performed using a measurement system of a drifter mounted on the hydraulic jumbo. Good.

Then, calculates the variation amount [Delta] V ₁ of drilling speed V ₁ corresponding to the variation [Delta] F ₁ and the variation amount of the feed pressure F ₁ using the measured data.

Variation [Delta] F ₁ of feed pressure F ₁ are, for example, determine the respective average feed pressure in the case where drilling the same section i (i = 1,2,3 ··· n) in two different settings feed pressure to each other, The difference between them may be taken as ΔF _i (i = 1, 2, 3... N).

On the other hand, the variation [Delta] V ₁ of drilling speed V ₁ was, respective average drilling rate in case of boring the same section i (i = 1,2,3 ··· n) in the two settings feed pressure mentioned above And the difference between them may be taken as ΔV _i (i = 1, 2, 3... N).

Next, regression analysis is performed on ΔF _i (i = 1, 2, 3... N) and ΔV _i (i = 1, 2, 3... N) to create a correlation curve.

  The set feed pressure is set as a guide for the feed pressure when driving the drilling means, and is different from the actually measured feed pressure.

  As a result of a large amount of data verification by the present applicant, even if the feed pressure is different, if the difference in the feed pressure is the same, the new knowledge that the difference in the corresponding drilling speed will be the same. Obtained.

  In addition, since fluctuations in feed pressure are mainly due to differences in rock mass properties of the natural ground, the above-mentioned findings suggest that if the difference in the feed pressure is the same even if the natural ground to be drilled is different, the corresponding cutting will be performed. In other words, the difference in the hole speed is the same.

In order to correct the drilling speed using the correlation curve described above, first, the ground is drilled by a drilling means such as a rock drilling machine at the second drilling site, and the feed pressure F ₂ at the time of drilling and The drilling speed V ₂ is measured.

Then, by applying the said difference [Delta] F ₂ calculates the difference [Delta] F ₂ from a reference feed pressure of the feed pressure F ₂ to the correlation curve described above, calculates the variation amount [Delta] V ₂ of drilling speed V _2.

Next, the modified drilling speed V _R is calculated by adding or subtracting the fluctuation amount ΔV ₂ to or from the drilling speed V ₂ .

  By executing the above procedure, it becomes possible to correct the drilling speed in consideration of fluctuations in the feed pressure. By using such drilling speed in the conventional drilling theory, more appropriate ground evaluation Can be performed.

Thus, although it may be evaluated for natural ground by applying a modified drilling speed V _R in a conventional drilling theory, conventional drilling theory, necessary parameters such evaluation is difficult loss factor Therefore, it is not always easy to evaluate the drilling energy accurately and accurately.

Applicants Under such circumstances, as a result of repeated studies of a method of evaluating the natural ground in a new point of view, by using the modified drilling speed V _R as described above without the conventional drilling theory, tunnel face forward It has succeeded in predicting the natural ground with higher accuracy.

That is, in the method for creating the natural ground section evaluation table according to claim 3, first, the corrected drilling speed V _R obtained by the above-described drilling speed correcting method is set so that the value thereof becomes 0 to 1. Normalization is performed to calculate a normalized drilling speed ratio V _N.

Next, the ground drill section evaluation table is created by associating the normalized drilling speed ratio V _N and the variation thereof with the ground section of the second drilling spot.

If the natural ground division evaluation table is created in this way, the natural ground division can be appropriately predicted at the third drilling site by the following procedure. That is, first, a natural ground is drilled by a drilling means such as a rock drill at the third drilling site, and the feed pressure F ₃ and the drilling speed V ₃ at the time of drilling are measured.

Then, to calculate the difference [Delta] F ₃ from the reference feed pressure of the feed pressure F _3.

Then, the difference [Delta] F _3, by applying the correlation curve obtained by boring speed modification method according to claim 1, wherein calculating the variation amount [Delta] V ₃ of drilling speed V _3.

Next, the modified drilling speed V _R is calculated by adding or subtracting the fluctuation amount ΔV ₃ to or from the drilling speed V ₃ .

Next, normalized drilling speed ratio V _N is calculated by normalizing the corrected drilling speed V _{R so} that the values thereof become 0 to 1.

Next, by applying the normalized drilling speed ratio V _N and the variation thereof to the ground section evaluation table obtained by the method for creating the ground section evaluation table according to claim 2, the third drilling site Guess the natural ground division.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a correlation curve creation method, a drilling speed correction method, a natural ground segment evaluation table creation method and a face front prediction method according to the present invention will be described below with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.

(First embodiment)

FIG. 1 is a flowchart showing a correlation curve creating method according to the present embodiment. As can be seen from the figure, in the correlation curve creation method according to the present embodiment, first, at the first drilling site, a natural ground is drilled with a drilling means, for example, a hydraulic jumbo, and feed at the time of drilling is performed. The pressure F ₁ and the drilling speed V ₁ are measured (step 101).

  Here, for example, an actual tunnel excavation site can be used as the first drilling site, but the purpose of the first drilling site is to regress the fluctuation amount of the feed pressure and the fluctuation amount of the drilling speed. Because it is to create a correlation curve between them and to obtain basic data necessary for that purpose, the forward prediction of the natural ground is possible at the third drilling site described later.

  When drilling, for example, the set feed pressure is adjusted so that the set feed pressure of the drifter mounted on the hydraulic jumbo has a different value each time. For example, it can be considered that the pressure is set to 4.90 MPa, 3.92 MPa, and 2.94 MPa.

Then, calculates the variation amount [Delta] V ₁ of drilling speed V ₁ corresponding to the variation [Delta] F ₁ and the variation amount of the feed pressure F ₁ using the measured data (step 102).

The fluctuation amount ΔF ₁ of the feed pressure F ₁ is obtained by calculating respective average feed pressures when the same section i (i = 1, 2, 3,... N) is drilled with two different set feed pressures. Is taken as ΔF _{1, i} (i = 1, 2, 3... N).

On the other hand, the variation [Delta] V ₁ of drilling speed V ₁ was, respective average drilling rate in case of boring the same section i (i = 1,2,3 ··· n) in the two settings feed pressure mentioned above And taking the difference between them, ΔV _{1, i} (i = 1, 2, 3... N). Hereinafter, represents the numerical value group of ΔF ₁ ΔF _1, i and (i = 1,2,3 ··· n), the numerical value group of _{ΔV 1 ΔV 1, i (i} = 1,2,3 ·· -It represents as n).

  FIG. 2 is a graph depicting the drilling speed and the average value when the average feed pressure is 4.90 MPa, 3.92 MPa, and 2.94 MPa at a certain drilling site. It can be seen that the drilling speed corresponding to is 230 cm / min, the drilling speed corresponding to 3.92 MPa is 180 cm / min, and the drilling speed corresponding to 2.94 MPa is 130 cm / min.

Of these, taking the difference between 4.90 MPa and 3.92 MPa,
ΔF _1,1 = 0.98MPa
The difference between 3.92 MPa and 2.94 MPa is expressed as ΔF _1,2 = 0.98 MPa
And At this time, the fluctuation amount of the corresponding drilling speed is
ΔV _1,1 = 50cm / min
ΔV _1,2 = 50cm / min
It becomes.

  3 to 5 are graphs showing the relationship between the feed pressure and the drilling speed at different drilling sites with the distance on the horizontal axis, and the fluctuation amount of the feed pressure and the corresponding drilling speed. The fluctuation amount is also described.

Among these, the fluctuation amount of the feed pressure in the section where the distance is 900 m to 930 m is
ΔF _1,3 = 0.245 MPa
It becomes. Also. The variation in drilling speed corresponding to this is
ΔV _1,3 = 15cm / min
It becomes.

Similarly, the fluctuation amount of the feed pressure and the fluctuation amount of the drilling speed corresponding to this in the section where the distance is 1300 m to 1320 m are
ΔF _1,4 = 0.49 MPa
ΔV _1,4 = 40cm / min
The feed pressure fluctuation amount and the corresponding drilling speed fluctuation amount in the section where the distance is around 1340 m are:
ΔF _1,5 = 1.715 MPa
ΔV _1,5 = 80cm / min
The amount of fluctuation in the feed pressure and the amount of fluctuation in the drilling speed corresponding thereto in the section where the distance is 2020 m to 2030 m are
ΔF _1,6 = 0.49 MPa
ΔV _1,6 = 30cm / min
The feed pressure fluctuation amount and the corresponding drilling speed fluctuation amount in the section where the distance is about 2040 m are
ΔF _1,7 = 0.49 MPa
ΔV _1,7 = 50cm / min
It becomes.

Next, the origin, ie
ΔF _1,0 ≒ 0
ΔV _1,0 ≒ 0
A total of 8 sets including ΔF _{1, i} (i = 0 _{, 1,} 2, 3,... 7) and ΔV _{1, i} (i = 0 _{, 1,} 2, 3,... 7) are subjected to regression analysis. A correlation curve is created (step 103). Here, ΔF _1,0 and ΔV _1,0 are set to 0.1 for convenience of regression analysis.

The eight sets of values mentioned above have the following cubic polynomial:
ΔV = c1 × (ΔF) ³
+ C2 × (ΔF) ²
+ C3 × (ΔF) ¹
The third order polynomial is shown in FIG. 6 as a correlation curve.

As can be seen from FIGS. 2 and 6, ΔV ₁ and ΔV ₂ are different in magnitude of the feed pressure, but ΔF ₁ and ΔF ₂ are both 50 cm / min.

  In addition to this, as a result of the applicant's extensive data verification, there are many examples showing similar properties, and therefore, even if the feed pressure is different, the difference in feed pressure is the same. For example, the new knowledge that the difference in the corresponding drilling speed is the same. When the difference in feed pressure was 0.49 MPa, three cases of 30 cm / min, 40 cm / min, and 50 cm / min were placed as the difference in drilling speed. It is shown that variation occurs in.

  In addition, since fluctuations in feed pressure are mainly due to differences in rock mass properties of the natural ground, the above-mentioned findings suggest that if the difference in the feed pressure is the same even if the natural ground to be drilled is different, the corresponding cutting will be performed. In other words, the difference in the hole speed is the same.

  That is, it can be said that the correlation curve shown in FIG. 6 is highly versatile and can be applied to any ground as long as the number of plots used for regression analysis is appropriate.

  As described above, according to the correlation curve creating method according to the present embodiment, even if the feed pressure is different, if the difference in the feed pressure is the same, the corresponding difference in the drilling speed is the same. Based on this new knowledge, it is possible to create a correlation curve that can calculate the corrected drilling speed from the measured feed pressure and drilling speed for any ground.

(Second Embodiment)

  Next, a drilling speed correction method according to this embodiment will be described.

FIG. 7 is a flowchart showing the procedure of the drilling speed correcting method according to the present embodiment. As shown in the figure, in the drilling speed correcting method according to the present embodiment, first, the feed pressure F ₂ and the drilling speed V ₂ at the time of drilling are set in advance while measuring at the second drilling site. A difference ΔF ₂ of the feed pressure F ₂ from the reference feed pressure F ₀ , for example, 4.9 MPa is calculated (step 111). That is,
ΔF ₂ = F ₂ -F ₀

Then, by applying the correlation curve difference [Delta] F ₂ of the (absolute value) described in the first embodiment, calculates the variation amount [Delta] V ₂ of drilling speed V ₂ (step 112).

Next, the modified drilling speed V _R is calculated by adding or subtracting the fluctuation amount ΔV ₂ to or from the drilling speed V ₂ (step 113).
Here, when the measured feed pressure F ₂ is larger than the reference feed pressure F ₀ , the drilling speed V ₂ is considered to decrease under the reference feed pressure F ₀ , and the following equation:
Corrected drilling speed V _R = Drilling speed V ₂ −ΔV ₂
To calculate the corrected drilling speed V _R.

On the other hand, when the measured feed pressure F ₂ is smaller than the reference feed pressure F ₀ , the drilling speed V ₂ is considered to increase under the reference feed pressure F ₀ , and the following equation:
Corrected drilling speed V _R = Drilling speed V ₂ + ΔV ₂
To calculate the corrected drilling speed V _R.

Figure 8 is a diagram showing a modified drilling speed V _R for measurement as described above.

As described above, according to the drilling speed correction method according to the present embodiment, modifications drilling speed V _R is, which has been modified as a predictive value when the feed pressure was standard feed pressure, The fluctuation of the feed pressure is appropriately taken into consideration.

Therefore, applying such modifications drilling speed V _R in a conventional drilling theory, become the drilling energy is calculated in the drilling speed in consideration of the feed pressure, thus, while using a conventional drilling theory, It becomes possible to perform forward prediction of the face with high accuracy.

(Third embodiment)

Next, a method for creating a natural ground division evaluation table according to the third embodiment will be described. FIG. 9 is a flowchart showing a procedure of a method for creating a natural ground division evaluation table according to the present embodiment. As shown in the figure, in creating a natural ground segment evaluation table according to the present embodiment, first, the maximum and minimum values from the correction drilling speed V _R obtained in drilling speed correction method described above extracted Then, the upper threshold and the lower threshold are set with reference to these values (step 121).

Next, the normalized drilling speed ratio V _N defined below is obtained for the corrected drilling speed V _R falling within the set threshold range (step 122).
V _N = (corrected drilling speed V _R -lower threshold) / (upper threshold-lower threshold)
For example, if the upper threshold is 2,000 cm / min and the lower threshold is -1,000 cm / min,
V _N = (corrected drilling speed V _R +1000) / 3000
It becomes.

Incidentally, if normalization is performed according to the procedure described above, each value of the normalized drilling speed ratio V _N falls within the range of 0 to 1.

FIG. 10 is a normalized drilling speed ratio V _N calculated for the above-described drilling data.

Next, the normalized drilling speed ratio V _N and its variation (the magnitude of noise. When the variation is small, the property of the rock is relatively homogeneous, and when the variation is large, the variation is relatively heterogeneous) A natural ground section evaluation table is created by associating with the natural ground section of the second drilling site (step 123).

For example, the variation in the normalized drilling speed ratio V _N is determined to be small (Noiseless) when the value for each predetermined section is within a fluctuation range of 0.05, and large when the value is not within the range (Noisey). be able to.

  Table 1 shows the created natural ground classification evaluation table.

As described above, according to the method for creating the natural ground section evaluation table according to the present embodiment, the normalized drilling speed ratio V according to the above-described procedure from the feed pressure and drilling speed measured at an arbitrary drilling site. By calculating _N and evaluating the magnitude of the noise, and comparing it with the natural ground section evaluation table, it is possible to estimate the natural ground section at any drilling site.

(Fourth embodiment)

  Next, a face front prediction method according to the fourth embodiment will be described.

FIG. 11 is a flowchart showing the procedure of the face forward prediction method according to the present embodiment. As shown in the figure, in the face forward prediction method according to the present embodiment, first, while measuring the feed pressure F ₃ and the drilling speed V ₃ at the time of drilling, preset in advance at the third drilling site. A difference ΔF ₃ of the feed pressure F ₃ from the calculated reference feed pressure F ₀ , for example, 4.9 MPa is calculated (step 131). That is,
ΔF ₃ = F ₃ -F ₀

Then, by applying the correlation curve described difference [Delta] F ₃ (absolute value) in the first embodiment, calculates the variation amount [Delta] V ₃ of drilling speed V ₃ (step 132).

Next, the modified drilling speed V _R3 is calculated by adding or subtracting the fluctuation amount ΔV ₃ to the drilling speed V ₃ (step 133).
Here, when the measured feed pressure F ₃ is larger than the reference feed pressure F ₀ , the drilling speed V ₃ is considered to decrease under the reference feed pressure F ₀ , and the following equation:
Corrected drilling speed V _R3 = Drilling speed V ₃ -ΔV ₃
Is calculated to obtain a corrected drilling speed V _R3 .

On the other hand, when the measured feed pressure F ₃ is smaller than the reference feed pressure F ₀ , the drilling speed V ₃ is considered to increase under the reference feed pressure F ₀ , and the following equation:
Corrected drilling speed V _R3 = Drilling speed V ₃ + ΔV ₃
Is calculated to obtain a corrected drilling speed V _R3 .

Next, a maximum value and a minimum value are extracted from the corrected drilling speed V _R3 , and an upper limit threshold and a lower limit threshold are set with reference to these values (step 134).

Next, the normalized drilling speed ratio V _N3 defined below is obtained for the corrected drilling speed V _R3 falling within the set threshold range (step 135).
V _N3 = (corrected drilling speed V _R3 -lower threshold) / (upper threshold-lower threshold)
For example, if the upper threshold is 2,000 cm / min and the lower threshold is -1,000 cm / min,
V _N3 = (corrected drilling speed V _R3 +1000) / 3000

It becomes. Incidentally, if normalization is performed according to the above-described procedure, each value of the normalized drilling speed ratio V _N3 falls within the range of 0 to 1.

Next, whether the variation in the normalized drilling speed ratio V _N3 is small (Noiseless) or large (Noisey) is determined in the same manner as in the third embodiment (step 136).

Next, the obtained normalized drilling speed ratio V _N3 is collated with the natural ground section evaluation table created by the procedure of the third embodiment, and the natural ground section at the third drilling site is evaluated. (Step 137).

  As described above, according to the face forward prediction method according to the present embodiment, by using a correlation curve and a natural ground section evaluation table prepared in advance, the site where the front of the face is to be predicted, which is It is possible to predict the rock properties of the natural ground spreading in front of the face at the site of No. 3.

The flowchart which showed the procedure of the correlation curve preparation method which concerns on 1st Embodiment. The graph which shows the drilling speed with respect to the average feed pressure used when creating a correlation curve. This graph shows the relationship between the feed pressure and the drilling speed with the distance on the horizontal axis, and shows the amount of fluctuation in feed pressure and the corresponding amount of drilling speed. Similarly, a graph showing the relationship between the feed pressure and the drilling speed with the distance on the horizontal axis. Similarly, a graph showing the relationship between the feed pressure and the drilling speed with the distance on the horizontal axis. The graph which showed the correlation with the fluctuation | variation amount of feed pressure, and the fluctuation | variation amount of drilling speed corresponding to them. The flowchart which showed the procedure of the drilling speed correction method which concerns on 2nd Embodiment. Graph showing the modified drilling speed V _R. The flowchart which showed the procedure of the preparation method of the natural ground division evaluation table which concerns on 3rd Embodiment. Graph showing the normalized drilling speed ratio V _N. The flowchart which showed the procedure of the face front prediction method which concerns on 4th Embodiment.

Claims (4)

At the first drilling site, a natural ground is drilled by a drilling means such as a rock drill and the feed pressure F ₁ and the drilling speed V ₁ at the time of drilling are measured, and the fluctuation amount of the feed pressure F ₁ is measured. A correlation curve creating method, wherein a correlation curve is created by performing regression analysis on ΔF ₁ and the fluctuation amount ΔV ₁ of the drilling speed V ₁ corresponding to the fluctuation amount. In the second drilling site, drilling a natural ground with a drilling means such as a rock drill, and measuring the feed pressure F ₂ and the drilling speed V _{2 during} drilling,
By applying said difference [Delta] F ₂ calculates the difference [Delta] F ₂ from a reference feed pressure of the feed pressure F ₂ in the correlation curve of claim 1, wherein calculating the variation amount [Delta] V ₂ of the boring speed V ₂ ,
A drilling speed correction method, wherein a corrected drilling speed V _R is calculated by adding or subtracting the fluctuation amount ΔV ₂ to or from the drilling speed V ₂ . The corrected drilling speed V _{R according} to claim 2 is normalized so that their values are 0 to 1, and a normalized drilling speed ratio V _N is calculated,
A method for creating a natural ground division evaluation table, wherein a natural ground division evaluation table is created by associating the normalized drilling speed ratio V _N and variations thereof with a natural ground division at the second drilling site. At the third drilling site, drill a natural ground with a drilling means such as a rock drill and measure the feed pressure F ₃ and the drilling speed V _{3 during} drilling.
It calculates the difference [Delta] F ₃ from the reference feed pressure of the feed pressure F _3,
The difference [Delta] F _3, by applying the correlation curve of claim 1, wherein calculating the variation amount [Delta] V ₃ of the drilling speed V _3,
A corrected drilling speed V _R is calculated by adding or subtracting the fluctuation amount ΔV ₃ to the drilling speed V ₃ ,
The corrected drilling speed V _R is normalized so that their values are 0 to 1, and a normalized drilling speed ratio V _N is calculated,
A face according to claim 3, wherein the normalized drilling speed ratio V _N and the variation thereof are applied to the ground drill section evaluation table according to claim 3 to estimate a ground section at the third drilling spot. Forward prediction method.