JP2024148783A - Ground determination support method, ground determination support system, and ground determination support program - Google Patents

Abstract

[Problem] To provide a ground judgment support method, a ground judgment support system, and a ground judgment support program for accurately judging whether the ground is firm or not using a specified threshold value. [Solution] A ground firmness judgment system 30 includes a construction index value storage unit 33 that stores construction index values based on excavation measurement values acquired when drilling a hole in the ground, and a control unit 31. The control unit 31 specifies a first identifier that judges whether the ground is firm or not based on the N value of the depth and the soil type. The control unit 31 specifies threshold value candidates for a target construction index used to judge the firmness of the ground, and, as a result of comparing each value of the target construction index with the threshold value candidates, specifies a second identifier that judges whether the ground is firm or not at the depth where each value of the target construction index was acquired. The control unit 31 calculates a capture rate and a false positive rate using the number of data of the target construction index classified based on the first identifier and the second identifier while changing the threshold value candidates, and uses these to determine a threshold value for the target construction index. [Selected Figure] Figure 2

Description

The present disclosure relates to a ground assessment support method, a ground assessment support system, and a ground assessment support program for identifying a threshold value for determining whether the ground is solid or not.

Conventionally, in order to support piles supporting buildings on solid ground, pile holes for forming piles are excavated down to the supporting layer of solid ground. Usually, the N value is used to indicate the hardness of the ground, but the hardness of this N value varies depending on the soil type even if the value is the same. Therefore, in order to evaluate the hardness of the ground regardless of the soil type, the shear wave velocity is sometimes used. Since it is difficult to measure the shear wave velocity, the hardness is determined using the converted shear wave velocity using the depth, N value, age coefficient according to the soil classification, and soil coefficient (see, for example, Patent Document 1). The control unit of the ground hardness estimation system described in this document acquires values measured by the drilling depth measuring instrument, flow measuring instrument, current measuring instrument, and vibration measuring instrument, and acquires multiple measurement values from these values. The control unit calculates a multiple regression equation by performing a multivariate analysis using the acquired measurement values and hardness index value as explanatory variables and objective variables, and records the multiple regression equation in the multiple regression equation storage unit. When the control unit acquires measurements of the excavation conditions of the hole to be evaluated, it uses these measurements and a multiple regression equation to estimate the hardness index value of the ground in which the hole to be evaluated was excavated.

JP 2021-080737 A

However, when using values such as reduced shear wave velocity, it was not possible to evaluate whether the threshold value for determining whether the ground is solid or not was appropriate. For this reason, it was difficult to accurately determine the solidity of the ground using the threshold value.

The ground assessment support method that solves the above problem is a ground assessment support method that identifies a threshold value for determining whether the ground is solid or not for a construction indicator based on an excavation measurement value obtained when drilling a hole in the ground, identifies a first identifier that determines whether the ground is solid or not based on the N value of the depth and soil type, identifies a threshold candidate for the target construction indicator used to determine the solidity of the ground, identifies a second identifier that determines whether the ground is solid or not at the depth at which each value of the target construction indicator was obtained by comparing each value of the target construction indicator with the threshold candidate, and calculates a verification index including at least one of a hit rate, a capture rate, and a false positive rate using the number of data points of the target construction indicator classified based on the first identifier and the second identifier while changing the threshold candidate, and determines the threshold value for the target construction indicator using the verification index.

According to the present invention, it is possible to accurately determine whether the ground is solid or not by using a specified threshold value.

FIG. 2 is a schematic front view of a drilling device for drilling a pile hole in the embodiment. 1 is a configuration diagram showing the configuration of a ground determination support system for determining the hardness of the ground in an embodiment. FIG. 2 is an explanatory diagram of a hardware configuration of the embodiment. 1A and 1B are diagrams illustrating the data configuration of a storage unit of a ground assessment support system according to an embodiment, in which FIG. 1A illustrates a geological survey information storage unit, and FIG. 11 is a flowchart illustrating a processing procedure of a threshold value determination process for determining the hardness of the ground in the embodiment. 11 is a table showing a relationship between the results of a geological survey and an actual solidity identifier in the embodiment. 10 is an explanatory diagram for explaining a process of calculating a predicted stiffness from a reduced shear wave velocity and a threshold candidate in an embodiment. FIG. 11 is an explanatory diagram for explaining a process of identifying a predicted actual situation identifier from a predicted firmness and an actual situation firmness identifier in an embodiment. FIG. FIG. 11 is an explanatory diagram illustrating a predicted actual situation identifier in the embodiment. 11 is an explanatory diagram illustrating a capture rate and a false detection rate when a threshold candidate is 500 in an embodiment. FIG. 11 is an explanatory diagram for explaining a curve of false detection rate-capture rate in reduced shear wave velocity and determination of a threshold value in an embodiment. Graphs showing the firmness of the ground corresponding to depth in a modified example, where (a) is a graph showing that the ground is actually firm at position "3" on the horizontal axis depending on the depth, (b) is a graph in which the firmness of the ground is determined using two types of construction indicators, and (c) and (d) are graphs in which the firmness of the ground is determined using one of the construction indicators in (b).

Below, an embodiment of a ground assessment support method, a ground assessment support system, and a ground assessment support program will be described with reference to Figures 1 to 11. In this embodiment, a threshold value is specified for the reduced shear wave velocity, which is a construction index, to determine whether the ground in which a pile hole is being excavated is solid or not.

Figure 1 shows an excavator 10 as an excavation device for excavating a pile hole h0. The excavator 10 includes a base machine 11, a mast 14, and an auger machine 16. The base machine 11 includes a lower traveling body including a crawler 12, and an upper rotating body including an operation room 13.

The mast 14 is erected on the base machine 11. Inside the mast 14, wires for measuring depth and speed are provided. An auger machine 16 is attached to the mast 14 so that it can be raised and lowered. The auger machine 16 is equipped with a drive motor housed in a box and a drilling rod 17 that is driven and rotated by the drive motor. A drilling head 18 is attached to the tip (lower end) of the drilling rod 17. The drilling head 18 has a pair (two) of swinging drilling arms with drilling blades at the tips. The elevation and lowering of the drilling head 18 is controlled by an operator in the operation room 13.

The excavator 10 is also connected to a drilling water supply device (not shown) that supplies drilling water to the drilling head 18. The amount of drilling water is adjusted by the operator in the control room 13 according to the drilling conditions.

As shown in FIG. 2, each measuring instrument (21-24) that measures the excavation status of the excavator 10 is connected to a ground firmness determination system 30, which serves as a ground determination support system. In this embodiment, they are connected to a drilling depth measuring instrument 21, a flow rate measuring instrument 22, a current measuring instrument 23, and a vibration measuring instrument 24. Each measuring instrument (21-24) constantly performs measurements and transmits the measured values to the ground firmness determination system 30.

The drilling depth measuring device 21 measures the amount of wire that is paid out inside the mast 14, and measures the drilling depth (depth) according to the position of the drilling head 18. In this case, the drilling depth measuring device 21 measures the drilling depth in relation to time.

The flow rate meter 22 measures the injection flow rate (injection amount) of drilling water supplied from the drilling water supply device. In this case, the flow rate meter 22 measures the injection amount in relation to time.
The current meter 23 measures the load current of the drive motor of the auger machine 16. In this case, the current meter 23 measures the current value in relation to time.

The vibration measuring device 24 measures vibrations at the installation location. In this embodiment, the vibration measuring device 24 is installed in the operation room 13 or the like, and measures vibration characteristics in three directions of the base machine 11: forward/backward, left/right, and up/down. In this case, the vibration measuring device 24 measures the vibration characteristics in relation to time.

(Hardware configuration)
3, the hardware configuration of the information processing device H10 constituting the ground firmness determination system 30 will be described. The information processing device H10 includes a communication device H11, an input device H12, a display device H13, a storage device H14, and a processor H15. Note that this hardware configuration is an example, and it is also possible to realize the system using other hardware.

The communication device H11 is an interface that establishes a communication path with other devices and transmits and receives data, such as a network interface or a wireless interface.

The input device H12 is a device that receives input from a worker or the like who specifies the ground firmness, and is, for example, a mouse, a keyboard, or the like.
The display device H13 is a display or the like that displays various information.
The storage device H14 is a storage device that stores data and various programs for executing various functions of the ground firmness determination system 30. Examples of the storage device H14 include a ROM, a RAM, and a hard disk.

The processor H15 uses the programs and data stored in the storage device H14 to control each process in the ground firmness determination system 30. Examples of the processor H15 include a CPU and an MPU. The processor H15 expands the programs stored in the ROM, etc., into the RAM and executes various processes for estimating ground firmness.

The processor H15 is not limited to performing software processing for all of the processes it executes. For example, the processor H15 may be equipped with a dedicated hardware circuit (e.g., an application specific integrated circuit: ASIC) that performs hardware processing for at least some of the processes it executes. That is, the processor H15 may be configured as a circuit including: [1] one or more processors that operate according to a computer program (software); [2] one or more dedicated hardware circuits that execute at least some of the various processes; or [3] a combination thereof. The processor includes a CPU and memory such as RAM and ROM, and the memory stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

(Ground Firmness Determination System 30)
The ground firmness determination system 30 shown in Fig. 2 is a computer system that determines the firmness of the ground using a construction index value. The ground firmness determination system 30 includes a control unit 31, a geological survey information storage unit 32, a construction index value storage unit 33, and a threshold value storage unit 34.

The control unit 31 performs the processes described below (measurement value management stage, threshold value specification stage, firmness determination stage, etc.). To this end, the control unit 31 functions as a measurement value management unit 311, a threshold value specification unit 312, and a firmness determination unit 313 by executing a ground firmness determination program.

The measurement value management unit 311 records the results of the geological survey obtained in the boring survey in the geological survey information storage unit 32. In this embodiment, the measurement value management unit 311 stores a table for identifying a soil identifier that is determined from the type of soil and the age of the soil.

Furthermore, the measurement value management unit 311 accumulates the measurement values acquired from each measuring device (21-24) for each time in memory, and records the measurement values for each depth in the construction index value storage unit 33. Specifically, the measurement value management unit 311 acquires the drilling depth, water injection amount, and current value during the time period during which drilling actually proceeded (drilling time period). In hard stratum, the drilling head 18 may be lifted once just before drilling. For this reason, the actual drilling depth of the drilling head 18 does not necessarily increase monotonically with the elapsed time. Therefore, the measurement value management unit 311 deletes the period during which the drilling head 18 is lifted or stopped from the total work time, and identifies the measurement value of the drilling time period that was actually used for drilling. The measurement value management unit 311 identifies the depth (start depth, end depth) and the drilling speed, water injection amount, and integral current value associated with this depth by associating the measurement values during the identified drilling time period.

Furthermore, the measurement value management unit 311 identifies the magnitude of vibration (amplitude value) for each analysis frequency by performing frequency analysis on the vibration characteristics in three directions measured by the vibration measuring device 24. In this embodiment, 20 intervals of frequencies in 1/3 octave band analysis (1 Hz to 80 Hz) are used as the analysis frequencies.

Furthermore, the measurement value management unit 311 stores a formula for calculating the reduced shear wave velocity. As the formula for calculating the reduced shear wave velocity, a multiple regression formula is used that uses the reduced shear wave velocity described in Cited Document 1 as the objective variable and calculates the regression coefficient of each explanatory variable. Here, the explanatory variables used are the logarithmic value of the integrated current value, the end depth, the excavation speed, the amount of water injected, and the vibration.

The threshold specifying unit 312 executes a process (threshold specifying process) for specifying a threshold for determining whether the ground is solid or not. In this case, the threshold specifying unit 312 sets a threshold candidate, and calculates a capture rate and a false positive rate using the number of data points of the determination result of whether the ground is solid or not using the set threshold candidate. Then, the threshold specifying unit 312 specifies a threshold candidate that satisfies a determination condition that the capture rate is large and the false positive rate is small as the threshold. Specifically, the threshold specifying unit 312 uses, as the threshold, the threshold candidate at the point that is the shortest distance from the coordinates (1, 0) when the false positive rate is plotted on the horizontal axis and the capture rate on the vertical axis.
The firmness determination unit 313 estimates the firmness of the excavated ground from the measurement values acquired when a new pile hole is excavated, using the thresholds stored in the threshold memory unit 34 .

As shown in FIG. 4(a), the geological survey information storage unit 32 records geological survey information obtained by boring survey results. The geological survey information includes data on the site identifier, boring identifier, survey location coordinates, N value associated with depth, soil type identifier, and actual hardness identifier.

The site identifier data area records data regarding an identifier for identifying the site where the drilling survey was conducted.
The survey location coordinate data area records data relating to the coordinates of the location where the boring survey was conducted at this site.

The depth data area records data on the depth that specifies the N value and soil type at this boring survey location. In this embodiment, for example, data is recorded in units of 0.1 m, and the depth range (end depth and start depth) is recorded.

In the N value data area, data regarding the N value measured at this depth is recorded.
The soil type identifier data field stores data on an identifier for identifying the type of soil at the depth. The soil type identifier is an identifier that is identified based on the soil type (clay, sand, etc.) and the age (new or old) of the soil.

The actual firmness identifier data area records an identifier (first identifier) for determining whether the ground at this depth is firm or not based on the N value and the soil type identifier. This actual firmness identifier is calculated and recorded during the determination process.

As shown in FIG. 4(b), the construction index value storage unit 33 records the construction index value in association with the site identifier, pile number, pile coordinates, and depth. Here, the construction index value is an index value used to determine the hardness of the ground. This construction index value includes the drilling measurement value and a value calculated using this drilling measurement value (e.g., reduced shear wave velocity, etc.). The drilling measurement value is a measurement value that can be obtained when drilling a pile hole. In this embodiment, values related to the integrated current value, drilling speed, injection amount, and vibration are used as the drilling measurement value.

The site identifier data area records data relating to an identifier for identifying the site where the pile hole was excavated.
The pile number data area and the pile coordinate data area store data on numbers for identifying the excavated piles and on the position coordinates of the piles. Using the pile coordinates and the survey position coordinates in the geological survey information storage unit 32, the construction index value can be associated with the geological survey information of the closest position where the boring survey was performed.

The depth data area records data on the depth of the measurements taken in this pile hole. In this embodiment, for example, data is recorded in units of 0.1 m, and the depth range (end depth and start depth) is recorded.

The integrated current value data area, drilling speed data area, and water injection amount data area each store data on the integrated current value (integrated current value) calculated from the measured current value, the speed of the drilling head 18 when drilling (drilling speed), and the injection amount of drilling water (water injection amount).

In the vibration data area, data on the vibration direction (three directions: front-back, left-right, and up-down) and the amplitude at the center frequency of each of 20 intervals is recorded.
The reduced shear wave velocity data area records data regarding the reduced shear wave velocity at this depth.

The threshold storage unit 34 shown in FIG. 2 records data related to the threshold for the construction index in association with the type of the construction index. In this embodiment, the threshold for the reduced shear wave velocity as the construction index is recorded.

(Threshold Identification Processing)
Next, a threshold value specification process for specifying a threshold value used to determine whether the ground is firm using the above-described ground firmness determination system 30 will be described with reference to FIGS.

Before performing this threshold determination process, the measurement value management unit 311 of the control unit 31 acquires, via the input device H12, a site identifier that identifies the site and the survey location coordinates where a boring survey was conducted at the site, and records these in the geological survey information storage unit 32. Furthermore, the measurement value management unit 311 acquires an N value corresponding to the depth in this boring survey, as well as information on the soil type and the age of the soil. The measurement value management unit 311 identifies a soil identifier from the acquired soil type and age information, and records this in the geological survey information storage unit 32 together with the depth and the N value corresponding to this depth.

Furthermore, the measurement value management unit 311 acquires the measurement values measured by each measuring device (21 to 24) when the pile hole is excavated and stores them in the memory. In this case, the measurement value management unit 311 identifies the time period (drilling time period) when the drilling was actually performed for each hour of drilling depth, and identifies the drilling depth, water injection amount, current value, and vibration characteristics for this time period. Then, the measurement value management unit 311 identifies the water injection amount according to the identified drilling depth (depth) and records the water injection amount in association with the depth in the construction index value storage unit 33. In addition, the measurement value management unit 311 calculates the drilling speed and integral current value based on the identified drilling depth in association with the drilling depth (depth), and records them in the construction index value storage unit 33. Furthermore, the measurement value management unit 311 identifies the vibration direction and the amplitude value at the analysis frequency by performing vibration analysis on the vibration based on the identified drilling depth, and records them in association with the drilling depth (depth) in the construction index value storage unit 33.

In the threshold identification process, first, the control unit 31 of the ground firmness assessment system 30 executes a process for calculating firmness in a boring survey (step S11). Specifically, first, the threshold identification unit 312 of the control unit 31 identifies the boring survey data closest to the pile hole from which the construction index (target construction index) used in this process was obtained. Here, the threshold identification unit 312 identifies the geological survey information having the survey position coordinates closest to the pile coordinates in the construction index value storage unit 33 from the geological survey information storage unit 32, and obtains the N value and soil type identifier corresponding to the depth of this construction index.

Then, as shown in FIG. 6, the control unit 31 displays the acquired N value and soil type identifier on the display device H13. The control unit 31 then acquires an actual firmness identifier indicating whether the ground was firm or not via the input device H12, and records it in the geological survey information storage unit 32. In FIG. 6, if the ground is firm, "3" is recorded as the actual firmness identifier, and if the ground is not firm, "-1" is recorded as the actual firmness identifier.

Next, the control unit 31 of the ground firmness determination system 30 executes a calculation process for the reduced shear wave velocity (step S12). Specifically, the measurement value management unit 311 of the control unit 31 calculates the reduced shear wave velocity Vs by substituting the construction index value recorded in the construction index value storage unit 33 into the stored reduced shear wave velocity calculation formula shown in Patent Document 1.

Next, the control unit 31 of the ground firmness determination system 30 executes a process of setting the range and interval of the threshold candidate (step S13). Specifically, the measurement value management unit 311 of the control unit 31 acquires the change range of the threshold candidate for the reduced shear wave velocity Vs and the change amount of the threshold candidate specified by the input device H12. Within this change range, the threshold candidate is changed sequentially by the change amount in the reduced shear wave velocity Vs, and an iterative calculation is performed to calculate the capture rate and false detection rate for each threshold candidate. Here, the change range of the threshold candidate for the reduced shear wave velocity Vs is set to "100 to 500", and the change amount is set to "1".

Next, the control unit 31 of the ground firmness determination system 30 repeatedly executes the following process for each threshold candidate.
First, the control unit 31 executes a process of identifying a threshold candidate (step S14). Specifically, the threshold identifying unit 312 of the control unit 31 identifies the maximum value in the change range as the threshold candidate. Then, each time the process of step S14 is repeatedly executed, a value obtained by subtracting the change amount "1" from the threshold candidate used in the preceding calculation is identified as the threshold candidate T1 to be used in the current calculation.

Next, the control unit 31 executes a process of specifying a prediction firmness identifier based on this threshold candidate (step S15).
Specifically, as shown in Fig. 7, the measurement value management unit 311 of the control unit 31 compares each value (construction index value) of the converted shear wave velocity associated with the depth with the candidate threshold value T1. If the converted shear wave velocity is equal to or greater than the candidate threshold value T1 as a result of the comparison, the measurement value management unit 311 assigns a predicted stiffness identifier (second identifier) of "3" to the converted shear wave velocity, and if the converted shear wave velocity is less than the candidate threshold value T1, the measurement value management unit 311 assigns a predicted stiffness identifier (second identifier) of "-1" to the converted shear wave velocity, and stores the identifier in memory.

Next, the control unit 31 executes a process of counting the true or false (step S16).
Specifically, as shown in FIG. 8, the measurement value management unit 311 of the control unit 31 identifies the predicted actual situation identifier by using the predicted firmness identifier and the actual situation firmness identifier.

Here, as shown in FIG. 9, if the actual situation firmness identifier is firm ("3") and the predicted firmness identifier is also firm ("3"), a "1" is assigned as the predicted actual situation identifier. If the actual situation firmness identifier is firm ("3") and the predicted firmness identifier is not firm ("-1"), a "3" is assigned as the predicted actual situation identifier.

In addition, if the actual situation firmness identifier is not firm ("-1") and the predicted firmness identifier is firm ("3"), a "2" is assigned as the predicted actual situation identifier. In the event that the actual situation firmness identifier is not firm ("-1") and the predicted firmness identifier is also not firm ("-1"), a "4" is assigned as the predicted actual situation identifier.

Next, the control unit 31 executes a process of calculating the capture rate and the false positive rate (step S17). Specifically, the measurement value management unit 311 of the control unit 31 calculates the number of data for each predicted actual situation identifier. Next, the measurement value management unit 311 calculates the capture rate by dividing the number of data for the predicted actual situation identifier "1" that is determined to be both actually solid and predicted to be solid by the number of data for the predicted actual situation identifiers "1" and "3" that indicate that the actual situation is solid. Furthermore, the measurement value management unit 311 calculates the false positive rate by dividing the number of data for the predicted actual situation identifier "2" that is determined to be not actually solid but predicted to be solid by the number of data for the predicted actual situation identifiers "2" and "4" that indicate that the actual situation is not solid.

For example, as shown in Figure 10, assume that the number of data items assigned the predicted actual situation identifier "1" is "3," the number of data items assigned the identifier "2" is "0," the number of data items assigned the identifier "3" is "4672," and the number of data items assigned the identifier "4" is "7137." In this case, the capture rate is 0.00064, and the false positive rate is 0.

The above process is repeated at set intervals within the range of threshold candidates set in step S13. As a result, the threshold identification unit 312 of the control unit 31 calculates the capture rate and false positive rate for each threshold candidate identified at set intervals within the set range.

Next, the control unit 31 executes a process of creating an ROC curve (step S18). Specifically, the threshold specification unit 312 of the control unit 31 plots positions corresponding to the capture rate and false positive rate of each threshold candidate in a two-dimensional coordinate graph with the horizontal axis representing the false positive rate and the vertical axis representing the capture rate. Then, a receiver operating characteristic curve (ROC curve) is generated by connecting the plotted positions with a curve. This ROC curve can evaluate the classification performance when classifying using the threshold candidate. The closer the shape of this ROC curve is to the upper left (1, 0), the higher the classification performance.
FIG. 11 shows an ROC curve C1 when the threshold value candidate for the reduced shear wave velocity is changed in increments of "1" within the range of "500 to 100."

Next, the control unit 31 executes a threshold determination process (step S19).
11, the threshold specifying unit 312 of the control unit 31 specifies, as a threshold, a candidate threshold corresponding to a point P1 where the distance R1 from the coordinates (1, 0) is the shortest in the generated ROC curve. The threshold corresponding to this point P1 is "233". Then, the threshold specifying unit 312 records the specified threshold in the threshold storage unit 34.

(Determining ground hardness using determined threshold value)
Thereafter, in the excavation process when drilling a pile hole, the threshold value recorded in the threshold value storage unit 34 is used to determine whether the ground where the pile hole arrives is firm or not. Specifically, the control unit 31 of the ground firmness determination system 30 executes an acquisition process of the excavation measurement values. Specifically, the measurement value management unit 311 of the control unit 31 acquires the excavation measurement values (water injection amount, drilling speed, integral current value, vibration direction, and amplitude value at analysis frequency) measured when a new pile hole is excavated using the excavator 10. Then, the firmness determination unit 313 records the excavation measurement values according to the drilling depth during the time period when the excavation actually proceeded in the construction index value storage unit 33 in association with the drilling depth (depth).
Furthermore, the measurement value management unit 311 calculates the reduced shear wave velocity by substituting the excavation measurement value into the stored equation for calculating the reduced shear wave velocity.

Then, the firmness determination unit 313 of the control unit 31 compares the calculated reduced shear wave velocity Vs with the threshold value recorded in the threshold value storage unit 34. If the result of the comparison shows that the reduced shear wave velocity Vs is equal to or greater than the threshold value, the firmness determination unit 313 determines that the ground is firm. In this case, the depth and a message indicating that the ground is firm are displayed on the display device H13.

(Action)
The capture rate and the false positive rate are calculated using the number of data for each predicted actual condition identifier, which is identified by comparing the converted shear wave velocity Vs calculated from the construction index value with a threshold candidate, and the actual condition identifier based on the N value and soil quality of the ground. Then, a threshold value with a high capture rate and a high false positive rate is identified.

According to this embodiment, the following effects can be obtained.
(1) In this embodiment, the control unit 31 of the ground firmness determination system 30 compares the converted shear wave velocity Vs calculated from the construction index value with a threshold candidate to identify a predicted firmness identifier. The control unit 31 calculates a capture rate and a false positive rate using the number of data for each predicted actual condition identifier identified by the predicted firmness identifier and the actual firmness identifier based on the N value and soil quality of the ground. The control unit 31 then identifies a threshold candidate that results in a large calculated capture rate and a small false positive rate as the threshold. This makes it possible to accurately set a threshold used to determine ground firmness using two parameters, the capture rate and the false positive rate.

(2) In this embodiment, in the ROC curve creation process (step S18), the control unit 31 of the ground firmness determination system 30 plots positions corresponding to the capture rate and false positive rate of each threshold candidate on a two-dimensional coordinate graph with the false positive rate on the horizontal axis and the capture rate on the vertical axis. The ROC curve is then generated by connecting the plotted positions with a curve. The control unit 31 then identifies the threshold candidate corresponding to point P1 on the generated ROC curve where the distance R1 from the coordinates (1,0) is the shortest. This makes it possible to efficiently identify a threshold where the calculated capture rate is large and the false positive rate is small.

(3) In this embodiment, the control unit 31 of the ground firmness determination system 30 determines the firmness of the ground using the converted shear wave velocity calculated based on the excavation measurement values. This makes it possible to evaluate the firmness of the ground from the excavation measurement values.

This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.
In the above embodiment, the control unit 31 of the ground firmness determination system 30 determined the threshold value of the converted shear wave velocity (step S19). The threshold value used to determine the ground firmness is not limited to the converted shear wave velocity, and may be another construction index, or multiple construction indexes may be used. When multiple construction indexes are used, the threshold value specification unit 312 of the control unit 31 executes the process of steps S13 to S19 for each construction index (target construction index) used for the determination. Then, the threshold value specification unit 312 records the determined threshold value in association with the construction index in the threshold value storage unit 34. In this case, the construction index may be not only the drilling measurement value (integral current value, end depth, drilling speed, water injection amount, vibration, etc.) that can be measured when forming the hole, but also a value calculated from them. For example, the start depth, instantaneous current value, drilling acceleration, etc. may be used.

For example, FIG. 12(a) shows that the ground is actually firm at the position "3" on the horizontal axis according to the depth. Furthermore, FIG. 12(c) and (d) show construction indicators 1 and 2 in which the ground is identified as firm using the threshold value identified by the threshold value identification process of the above embodiment. Here, construction indicator 1 indicates the change in converted shear wave velocity, and construction indicator 2 indicates the change in excavation speed. FIG. 12(b) shows a portion that is determined to be firm because the value of construction indicator 1 (construction indicator value 1) is equal to or greater than "threshold 1" and the value of construction indicator 2 (construction indicator value 2) is equal to or less than "threshold 2". As is clear from FIG. 12(b), at a depth of approximately 25 m, the ground is determined to be firm at a depth closer to the actual ground firmness shown in FIG. 12(a) than the threshold values for each construction indicator in FIG. 12(c) and (d).

- In the above embodiment, the control unit 31 of the ground firmness determination system 30 used the candidate threshold at the minimum distance from the coordinates (0, 1) in the created ROC curve as the threshold. The condition for determining the threshold is not limited to the minimum distance from the coordinates (0, 1). For example, the threshold may be a candidate threshold at which the capture rate is a predetermined value (e.g., a candidate threshold corresponding to a point that is 75% or more and has the minimum false positive rate).

- In the above embodiment, the threshold was determined using the capture rate and false positive rate. Not limited to this, the verification index for identifying the threshold from the threshold candidate may be either the capture rate or the false positive rate, or the threshold may be determined using the hit rate. This hit rate is calculated by dividing the total number of data items of the predicted actual situation identifier "1" that was determined to be actually solid and the prediction was also solid, and the total number of data items of the predicted actual situation identifier "4" that was determined to be not actually solid and the prediction was also not solid, by the total number of data items. Here, the threshold candidate with the highest hit rate may be used as the threshold. Furthermore, the threshold candidate with the highest hit rate among the threshold candidates with a high capture rate and a low false positive rate may be used as the threshold.

Next, the technical ideas that can be understood from the above embodiment and other examples will be described below.
(a) The ground judgment support method described in claim 3, characterized in that the control unit determines as the threshold the threshold candidate that is located at the position where the horizontal axis value is ``0'' and the horizontal axis value is ``1'' at the shortest distance from the coordinate in a graph with the false detection rate on the horizontal axis and the capture rate on the vertical axis.

C1...ROC curve, h0...pile hole, P1...point, R1...distance, T1...threshold candidate, Vs...reduced shear wave velocity, 10...drilling machine, 11...base machine, 12...crawler, 13...operation room, 14...mast, 16...auger machine, 17...drilling rod, 18...drilling head, 21...drilling depth meter, 22...flow meter, 23...current meter, 24...vibration meter, 30...ground firmness determination system as ground determination support system, 31...control unit, 32...geological survey information storage unit, 33...construction index value storage unit, 34...threshold value storage unit, 311...measurement value management unit, 312...threshold value identification unit, 313...firmness determination unit.

Claims (5)

A ground judgment support method for identifying a threshold value for determining whether the ground is solid or not for a construction index based on an excavation measurement value acquired when drilling a hole in the ground,
Identifying a first identifier that determines whether the ground is solid or not based on the N value of the depth and the soil type;
Identifying threshold candidates for a target construction index used to determine the hardness of the ground;
A second identifier is identified based on a result of comparing each value of the target construction index with the threshold candidate, the second identifier being used to determine whether or not the ground is solid at the depth at which each value of the target construction index is obtained;
While changing the threshold candidate, a verification index including at least one of a hit rate, a capture rate, and a false positive rate is calculated using the number of data of the target construction index classified based on the first identifier and the second identifier,
A ground judgment support method, characterized in that the threshold value for the target construction index is determined using the verification index. Calculating the capture rate by dividing the number of data items of the target construction indexes indicated as being firm by the number of data items of the target construction indexes indicated as being firm by the first identifier,
Calculating a false positive rate by dividing the number of data items of the target construction indexes indicated by the first identifier as not being firm and the second identifier as being firm by the number of data items of the target construction indexes indicated by the first identifier as not being firm;
Repeating the calculation of the capture rate and the false positive rate while sequentially changing the threshold candidate within a predetermined range;
The ground judgment support method according to claim 1, characterized in that the threshold candidate for the capture rate and the false detection rate corresponding to the threshold determination condition is determined as the threshold for the target construction index. A process of plotting the calculated capture rate and false positive rate on a graph having the capture rate and the false positive rate as axes of a two-dimensional coordinate system to create a curve;
3. The method for supporting ground determination according to claim 2, further comprising using the curve to determine the candidate threshold value for which the capture rate is large and the false positive rate is small as the threshold value. A ground judgment support system including a construction index value storage unit that stores values of construction indexes based on excavation measurement values acquired when drilling a hole in the ground, and a control unit that specifies a threshold value for determining whether the ground is solid or not,
The control unit is
Identifying a first identifier that determines whether the ground is solid or not based on the N value of the depth and the soil type;
Identifying threshold candidates for a target construction index used to determine the hardness of the ground;
A second identifier is identified by comparing each value of the target construction index stored in the construction index value storage unit with the threshold candidate, and determining whether or not the ground is solid at the depth at which each value of the target construction index is acquired;
While changing the threshold candidate, a verification index including at least one of a hit rate, a capture rate, and a false positive rate is calculated using the number of data of the target construction index classified based on the first identifier and the second identifier,
A ground judgment support system characterized by using the verification index to determine the threshold value for the target construction index. A ground judgment support program for identifying a threshold value for determining whether the ground is solid or not, using a ground judgment support system including a construction index value storage unit that stores values of construction indexes based on excavation measurement values acquired when drilling a hole in the ground, and a control unit,
The control unit,
Identifying a first identifier that determines whether the ground is solid or not based on the N value of the depth and the soil type;
Identifying threshold candidates for a target construction index used to determine the hardness of the ground;
A second identifier is identified by comparing each value of the target construction index stored in the construction index value storage unit with the threshold candidate, and determining whether or not the ground is solid at the depth at which each value of the target construction index is acquired;
While changing the threshold candidate, a verification index including at least one of a hit rate, a capture rate, and a false positive rate is calculated using the number of data of the target construction index classified based on the first identifier and the second identifier,
A ground assessment support program characterized by using the verification index to determine the threshold value for the target construction index.

Images