Ground estimation method and ground estimation system

Abstract

To efficiently acquire ground information on a drilled point based on drilling data at the time of drilling with high accuracy.SOLUTION: A ground estimation method for estimating ground information on a drilled point based on rotational torque at the time of drilling estimates ground strength in the ground information using a previously acquired N value estimation formula. The N value estimation formula is calculated by: a drilling information acquisition step of drilling a reference point set in the vicinity of an investigation point where an actually measured N value is known for each actually measured depth, and acquiring the rotational torque; a soil determination step of giving an arbitrary soil determination value to soil for each depth of the reference point, and acquiring a soil determination result of the reference point; an analysis preparation step of performing speed correction to make speed in a depth direction constant on the rotational torque of the reference point, then calculating a representative value corresponding to the actually measured depth as rotational torque for analysis, and calculating a representative value corresponding to the actually measured depth from the soil determination result of the reference point as a soil determination value for analysis; and an estimation formula acquisition step of performing regression analysis using the actually measured N value as a target variable and the rotational torque for analysis and the soil determination value for analysis as explanatory variables.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a ground estimation method and a ground estimation system for acquiring ground information at a drilling site. [Background technology]

[0002] Conventionally, the most widely used ground improvement methods are those that can be carried out without subjecting the ground to vibration or shock, such as the chemical injection method, jet grouting method, and static pressurization compaction method. All of these methods aim to strengthen the ground by inserting rods into invisible parts of the ground to supply ground improvement materials and create an improved body. For ground improvement work that employs these methods, a ground survey of the construction site is conducted in advance to estimate the ground composition and strength and to determine the improvement specifications.

[0003] As a preliminary investigation, a ground survey is often carried out using a survey boring machine. Specifically, the construction area is divided into several work sections, a ground survey is carried out for each work section, and a specialist company estimates the ground composition and N value of the work section or the entire construction area based on the obtained soil data.

[0004] However, due to various constraints such as survey time, the number of drillings required for preliminary surveys using boring machines is often limited to one or two drillings per work area. This can easily lead to discrepancies between the estimated survey results and the actual ground conditions, which can lead to problems such as insufficient completed ground improvement bodies. For this reason, there is a demand for a method that can accurately obtain the surface ground structure and ground information for the entire construction area, especially in ground improvement work.

[0005] In this situation, several soil investigation methods using drilling parameters have been proposed to be used in combination with general geological investigation methods to determine the classification and relative strength of the ground. For example, the Empathol system disclosed in Patent Document 1 is a system in which various sensors are attached to a drilling machine, these sensors measure data during drilling, and the data is analyzed and processed by a computer to obtain ground information such as the classification of the ground and its hardness and softness.

[0006] Specifically, the stratum is identified by combining the parameters of water pressure (the pressure required to remove slime during drilling) and drilling speed. In addition, rotational energy is obtained from four parameters: rotational speed, excavation speed, bit thrust, and rotational torque, and the strength of the ground is evaluated. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 9-242459 Summary of the Invention [Problem to be solved by the invention]

[0008] The Empathol system disclosed in Patent Document 1 uses drilling machines with excellent drilling capabilities, such as rotary percussion drills and drilling machines, so the investigation speed is fast and various injection works can be performed using the investigation holes. Therefore, if it is adopted for ground improvement work, it is possible to perform layer discrimination and evaluation of ground strength at the construction position set in the construction target range, and then use the investigation holes to inject ground improvement liquid. However, the work of bringing in an investigation drilling machine to the construction site of the ground improvement work, discriminating the layer and evaluating the ground strength, and then repeatedly replacing it with the ground improvement machine for each construction position is cumbersome and requires a lot of work and effort.

[0009] On the other hand, it is also possible to combine the Empasol system with a drilling machine used in ground improvement work. However, since the purpose of the drilling machine is to form guide holes in the ground to insert rods used for injecting ground improvement fluid, it is often designed with a ring bit on the casing. The ring bit has a small contact surface with the ground and does not generate a large rotational torque.

[0010] In this light, combining it with the Empathol system, which evaluates ground strength by obtaining rotational energy from four parameters - rotational speed, drilling speed, bit thrust, and rotational torque - is not necessarily appropriate, and issues arise in the method of estimating ground strength.

[0011] The present invention has been made in consideration of such problems, and its main object is to obtain ground information at a drilling site efficiently with high accuracy based on drilling data obtained during drilling. [Means for solving the problem]

[0012] In order to achieve this object, the ground estimation method of the present invention is a ground estimation method that estimates ground information at a drilling point based on the rotational torque during drilling, and estimates the ground strength from the ground information using a previously acquired N-value estimation formula. The N-value estimation formula is calculated by the following steps: a drilling information acquisition process in which a reference point is drilled at a reference point set in the vicinity of a survey point where the actual measured N value for each actual measured depth is known, and a rotational torque is acquired; a soil quality judgment process in which an arbitrary soil quality judgment value is assigned to the soil quality for each depth at the reference point to acquire a soil quality judgment result for the reference point; an analysis preparation process in which a speed correction is performed on the rotational torque at the reference point to make the speed in the depth direction constant, and then a representative value corresponding to the actual measured depth is calculated as the analysis rotational torque, and from the soil quality judgment result at the reference point, a representative value corresponding to the actual measured depth is calculated as the analysis soil judgment value; and an estimation formula acquisition process in which a regression analysis is performed with the actual measured N value as the response variable, and the analysis rotational torque and the analysis soil judgment value as explanatory variables.

[0013] In the ground estimation method of the present invention, in the analysis preparation step, the analysis rotation torque is The representative value corresponding to the actual measured depth after velocity correction is subjected to a change range correction to make the change range in the depth direction equal to the change range of the actual measured N value.

[0014] The ground estimation method of the present invention is characterized in that, in the soil quality determination process, the soil quality for each depth of the reference point is determined based on a soil quality determination threshold for rotational torque set by comparing the known soil quality classification of the survey point with the rotational torque of the reference point, and on the rotational torque of the reference point.

[0015] The ground estimation method of the present invention is characterized in that the soil type judgment threshold for the rotational torque includes an average threshold and a variance threshold, and the average threshold is set based on the average calculated for each statistical processing section set in the depth direction from the rotational torque at the reference point and the known soil type classification of the survey point, and the variance threshold is set based on the variance calculated for each statistical processing section from the rotational torque at the reference point and the known soil type classification of the survey point.

[0016] The ground estimation method of the present invention is characterized in that the soil type classification of the ground information at the drilling point is determined based on the rotational torque at the drilling point and the soil type determination threshold value.

[0017] The ground estimation system of the present invention is a ground estimation system adopted in the ground estimation method of the present invention, and comprises a ground drilling machine that drills the drilling point and the reference point, and a ground estimation device that calculates at least the N-value estimation formula, and the ground estimation device comprises a drilling information acquisition unit that acquires the rotational torque output from the ground drilling machine, a soil quality judgment unit that assigns an arbitrary soil quality judgment value to the soil quality for each depth at the reference point to acquire a soil quality judgment result for the reference point, an analysis preparation unit that calculates the analysis rotational torque from the rotational torque of the reference point acquired by the drilling information acquisition unit and calculates the analysis soil judgment value from the soil quality judgment result of the reference point acquired by the soil quality judgment unit, and an estimation formula acquisition unit that performs a regression analysis using the analysis rotational torque and the analysis soil judgment value calculated by the analysis preparation unit as explanatory variables and the measured N-value as a response variable, and calculates the N-value estimation formula.

[0018] The ground estimation system of the present invention is characterized in that the ground drilling machine is a ground improvement drilling machine.

[0019] According to the ground estimation method and ground estimation system of the present invention, a reference point is set near a survey point where the ground strength and soil type classification are known, and an N-value estimation formula is calculated based on the rotational torque obtained by drilling a hole at this reference point and the known ground strength and soil type classification, and a soil type judgment threshold is also set.

[0020] As a result, if the ground drilling machine used to drill the reference point is used, the estimated N-value of the drilling point can be calculated based on the rotational torque obtained during the drilling work at the drilling point and the N-value estimation formula. Also, the soil type of the drilling point can be determined based on the rotational torque obtained during the drilling work and the soil type judgment threshold. Therefore, regardless of which ground drilling machine is used, it is possible to efficiently obtain ground information at the drilling point with high accuracy based on the drilling data at the time of drilling.

[0021] As such, there are no restrictions on ground drilling machines and they are highly versatile, so they can be used in a variety of construction projects involving drilling work, such as using a drilling machine that uses a ring bit, which has a small contact area with the ground. This makes it possible to reflect the obtained ground information in the construction work to be carried out.

[0022] For example, when a ground improvement drilling machine is used as a ground drilling machine, the soil type and ground strength of the construction site where the drilling is to be performed can be estimated at the same time as the drilling work. As a result, when used in ground improvement work such as chemical injection method, jet grouting method, and static pressurization compaction method, ground improvement materials can be supplied to the ground according to improvement specifications according to the actual ground at the construction site, and an improved body can be created. This makes it difficult for defects such as insufficient finished shape to occur, and contributes to improving the quality of the improved body.

[0023] In addition, because the soil type and ground strength can be estimated for each construction point set in the ground improvement range, it is possible to grasp the ground information of the entire ground improvement range based on the estimation results. This makes it possible to identify at an early stage any areas where problems such as runoff of ground improvement liquid may occur when carrying out construction work of an improvement body at any construction point. This makes it possible to quickly implement effective measures and improve the workability of ground improvement work. Effect of the Invention

[0024] According to the present invention, ground drilling is performed at a reference point set near a survey point where ground information is known, and an N-value estimation formula used to estimate ground strength and a soil judgment threshold value for determining the soil type classification are obtained.By using the ground drilling machine used at the reference point, it is possible to obtain ground information at the drilling point with high accuracy and efficiency based on the drilling data obtained at the time of drilling. [Brief description of the drawings]

[0025] [Figure 1] 1 is a diagram showing a ground estimation system according to an embodiment of the present invention. [Diagram 2] FIG. 13 is a diagram showing the relationship between a columnar diagram and a rotational torque according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a diagram showing the mean and variance of rotational torque and the results of soil type determination based on a soil type determination threshold value in the embodiment of the present invention. [Figure 4] FIG. 11 is a diagram showing a regression analysis result according to an embodiment of the present invention. [Diagram 5] FIG. 13 is a graph showing speed correction and change range correction of rotational torque in the embodiment of the present invention. [Figure 6] 1 is a diagram showing a ground estimation device according to an embodiment of the present invention. [Figure 7] FIG. 1 is a diagram showing a construction site of a ground improvement work according to an embodiment of the present invention. [Figure 8] FIG. 2 is a diagram showing a flow of a ground estimation method according to an embodiment of the present invention. [Figure 9]FIG. 4 is a diagram showing a procedure for acquiring analytical rotation torque and analytical soil quality judgment value in the embodiment of the present invention. [Figure 10] FIG. 1 is a diagram showing a list of N values ​​(actually measured N values), analytical rotation torques TX, and analytical soil quality judgment values ​​D at survey points used in regression analysis in an embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing the calculation results of the estimated N value of a construction site in an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The present invention aims to estimate the soil type and ground strength in the depth direction from drilling data that can be continuously acquired when drilling the ground. This method and system can be applied to any mechanical drilling method, but is particularly effective for casing drilling with a ring bit that has a small contact surface with the ground.

[0027] Below, the case of estimating ground information at the construction site of a ground improvement body will be taken as an example, and the details of the ground estimation method and the ground estimation system will be described with reference to Figures 1 to 11. Prior to this, the ground improvement drilling machine used in the ground improvement work will be described.

[0028] <<Ground improvement drilling machine>> In ground improvement works such as chemical injection, jet grouting, and static pressurization compaction, a ground improvement material is supplied through an injection rod inserted into the ground to create an improved body 40 as shown in Fig. 1. For this reason, a guide hole 41 for inserting the injection rod is drilled in advance using a ground improvement drilling machine 20.

[0029] The ground improvement drilling machine 20 comprises a drilling casing 27 to which rotational force and propulsive force are applied from the drilling machine main body 21, and a ring bit 271 attached to the tip of the casing 27. The drilling machine main body 21 also comprises a displacement sensor 24 for measuring the underground depth of the ring bit 271, and a pressure sensor 25 for measuring the rotational torque, feed pressure, chuck pressure, etc. of the drilling casing 27.

[0030] Furthermore, a water pump 22 for sending drilling water into a drilling casing 27 to discharge slime generated during drilling, a pressure sensor 23 for measuring water pressure, and a data logger 26 for reading information acquired by each of the various sensors (23, 24, 25) are installed. The data logger 26 collects and organizes the read information by time, and outputs this as drilling data to a ground estimation device 30 described later. The drilling data output from the data logger 26 includes at least the drilling depth, drilling time, feed speed, rotational torque, and feed pressure.

[0031] <<Outline of ground estimation method>> When the above-mentioned ground improvement drilling machine 20 was used to drill holes near the investigation holes where investigation boring was performed, it was found that even when casing drilling was performed with a ring bit 271 that has a small contact surface with the ground, the change in soil quality along the depth direction is reflected in the change in rotation torque. Figure 2 shows the columnar diagram obtained by performing investigation boring and the rotation torque data obtained when drilling holes near the investigation holes.

[0032] Figure 2 shows that the ground near the investigation hole has a soil composition in which sandy soil and clayey soil form multiple layers in the depth direction, and that the N value increases in the depth direction. When comparing this soil composition with the rotational torque obtained by drilling a hole near the investigation hole, it can be seen that the rotational torque increases in the sandy soil and decreases in the clayey soil. When comparing the N value and rotational torque, it can be seen that the rotational torque also increases in response to the N value.

[0033] Therefore, in the ground estimation method, the position where the drilling casing 27 as shown in Figure 1 is inserted, i.e., the soil classification and ground strength (N value) of the construction point G of the improvement body 40, are estimated using the rotational torque obtained when drilling the construction point G.

[0034] The soil type classification is determined based on a soil type judgment threshold obtained in advance and the rotational torque at construction site G. In addition, an N-value estimation formula is obtained in advance, and ground strength (N-value) is determined based on this N-value estimation formula, the rotational torque at construction site G, and the soil type judgment results. These soil type judgment threshold and N-value estimation formula are obtained by setting a reference point C near survey site R and performing calibration using the rotational torque obtained by drilling a hole at reference point C.

[0035] To obtain the soil quality judgment threshold, first, as shown in Fig. 1, a reference point C is set near a survey point R. Survey point R is a point where survey boring was conducted in the past and the soil type classification and ground strength (N value) are known. A hole is drilled using a soil improvement drilling machine 20 at the reference point C set near the survey point R, and drilling data is obtained.

[0036] Next, the continuous rotation torque in the depth direction obtained by drilling the hole at reference point C is appropriately organized and statistically processed as shown in Figure 3 (a) and (b). This statistically processed rotation torque is compared with the soil type classification of the survey point, and a soil type judgment threshold value that can accurately distinguish between sandy soil and clayey soil is determined from the statistically processed rotation torque.

[0037] On the other hand, the N-value estimation formula shown in Fig. 4 has the objective variable being the measured N-value, and the explanatory variables being the soil quality judgment value D for analysis and the rotational torque T for analysis. X The soil quality judgment value D and the rotation torque T X and get.

[0038] The work of acquiring the soil quality judgment value D for analysis involves judging the soil quality for each prescribed depth at reference point C using the above-mentioned soil quality judgment threshold, and then assigning an arbitrary soil quality judgment value to each soil quality as shown in Figure 3(c), and acquiring this as the soil quality judgment result for reference point C. From this soil quality judgment result, a representative value (e.g., average, median, mode, etc.) corresponding to the actual measurement depth at which the N value (actual measurement N value) of investigation point R was acquired is calculated, and the soil quality judgment value D for analysis is acquired.

[0039] Analysis torque TX The acquisition work is to carry out speed correction and ratio correction for the continuous rotation torque in the depth direction acquired by drilling the reference point C, and then calculate a representative value corresponding to the actual measured depth. Next, this representative value is corrected for the change range to obtain the rotation torque for analysis T X The speed correction, ratio correction, change range correction, and other correction methods used here will be described in detail later, but the speed correction and change range correction are performed based on the following findings.

[0040] Speed ​​correction is a correction that aims to evaluate the continuous rotation torque in the depth direction under the condition of a constant speed. As a characteristic of ground drilling, for example, it can be predicted that the drilling speed will decrease when drilling a gravel layer with a large N value. In this sense, even if the rotation torque is continuously obtained in the depth direction, the change cannot be accurately captured if the drilling speed is different.

[0041] For this reason, when estimating the soil type classification and ground strength (N value), the ground is drilled while controlling the drilling speed on the ground improvement drilling machine 20 side to keep it constant, and a rotational torque with a constant speed in the depth direction is obtained. However, even if drilling is performed at a constant speed based on the drilling speed set on the ground improvement drilling machine 20 side, a speed drop may occur when looking at the actual measured value of the drilling speed, as shown in Figure 5 (a). For this reason, speed correction, etc. is performed when estimating ground strength (N value), which requires full consideration of changes in the drilling speed.

[0042] Moreover, the change range correction is a correction performed so that the change range in the depth direction of the representative value corresponding to the actual measured depth calculated after the speed correction and the ratio correction (hereinafter referred to as the "average value T of the ratio-corrected rotational torque") has a 1:1 relationship with the change range in the depth direction of the N value (actual measured N value) at the survey point R. Fig. 5(b) shows a graph showing the correlation between the average value T of the ratio-corrected rotational torque and the N value (actual measured N value) at the survey point R with and without the change range correction.

[0043] In Fig. 5(b), an example is shown in which the N value (actual measured N value) at survey point R varies from 1 to 100 in the depth direction, and the average value T of the ratio-corrected rotational torque varies from 1 to 10 in the depth direction. 2 Looking at the average value T of the ratio-corrected rotational torque, the change range correction T 2 In the case of , the value is 0.8037, which is much higher than the case without the change range correction, and it is clear that the fit is good. Therefore, the change range correction is performed on the average value T of the ratio-corrected rotating torque, and the analytical rotating torque T X Get the.

[0044] As described above, in the ground estimation method, a reference point C is set near survey point R, where the ground strength (N-value) and soil type classification are known, and an N-value estimation formula is calculated based on the rotational torque obtained by drilling a hole at this reference point C and the known ground strength and soil type classification, and a soil type judgment threshold is also set.

[0045] As a result, by adopting the ground improvement drilling machine 20 used for drilling the reference point C, it is possible to calculate the estimated N-value of the construction point G based on the rotational torque obtained during the drilling work at the construction point G and the N-value estimation formula. Also, it is possible to determine the soil type classification of the construction point G based on the rotational torque obtained during the drilling work and the soil type determination threshold value.

[0046] Therefore, when used in ground improvement work such as chemical injection, jet grouting, and static pressurization, the ground improvement material can be supplied to the ground according to improvement specifications that correspond to the actual ground conditions at the construction site G, and an improved body 40 can be constructed. This makes it possible to prevent defects such as insufficient finished shape from occurring, and contribute to improving the quality of the improved body.

[0047] In addition, it is possible to use a casing drilling machine that employs a ring bit 271 with a small contact area, such as the ground improvement drilling machine 20, and there is no restriction on the ground drilling machine, making it highly versatile. Therefore, it can be used in various construction works involving drilling work, and the obtained ground information can be reflected in the construction work to be carried out. It will be possible to carry out ground surveys.

[0048] <<<<Ground Estimation System>>>> The above-mentioned soil estimation method for estimating the soil type and soil strength (N value) may be carried out using a soil estimation system 10 shown in Fig. 1. The soil estimation system 10 includes the soil improvement drilling machine 20 and the soil estimation device 30 described above.

[0049] ≪≪Ground estimation device≫≫ As shown in Figures 1 and 6, the ground estimation device 30 is connected to the data logger 26 of the above-mentioned ground improvement drilling machine 20 by any means such as wired or wireless, and is equipped with an input device 31, an output device 32, a central processing unit 33, a file device 34, and a main memory 35.

[0050] Examples of the input device 31 include a keyboard, a scanner, a touch panel, etc., and examples of the output device 32 include a display, a printer, etc. Furthermore, the central processing unit 33 is a computer having a CPU, a GPU, a ROM, a RAM, a hardware interface, etc.

[0051] The file device 34 is a storage device consisting of a semiconductor memory or a hard disk drive, etc. Details will be described later, but it is provided with at least an investigation data file 341 in which ground information etc. of the investigation point R is stored, a drilling data file 342 in which data etc. related to the reference point C are stored, an analysis data file 343 in which data used for multiple regression analysis is stored, a regression analysis result file 344, and an estimation data file 345 in which data etc. related to the construction point G are stored.

[0052] The main memory 35 temporarily stores programs and data that can be executed by the central processing unit 33. The details will be described later, but it is equipped with at least an investigation information acquisition unit 351, a drilling information acquisition unit 352, a soil quality determination unit 353, an analysis preparation unit 354, an estimation formula acquisition unit 355, and an N-value estimation unit 356.

[0053] <<<<<Ground Estimation Method Procedure>>>>> The procedure of the above-mentioned ground estimation method using the ground estimation system 10 will be described with reference to Fig. 6 and Fig. 8, along with details of the ground estimation system 10, using an example in which the procedure is carried out at a construction site of a ground improvement work as shown in Fig. 7. Fig. 8 shows the flow of the ground estimation method and the data flow.

[0054] Figure 7 shows one of several blocks into which the wide-area target area for ground improvement work has been divided. Within that area, construction of improvement bodies 40 is planned at several points (A1 to A11). This block is also divided into two smaller blocks (A-1BL, A-2BL), and at the investigation point R set up in each, there are investigation borehole remnants (A-1, A-2) where ground investigations were carried out.

[0055] In this embodiment, of the multiple locations (A1 to A11) where the improvement body 40 is planned to be constructed, location A1 is set as the construction location G where the soil type classification and ground strength are estimated, and the details of the procedure of the ground estimation method and the ground estimation system are described below.

[0056] <<Preparation>> First, as shown in FIG. 7, a reference point C is set at a desired point close to the survey point R where the survey borehole trace (A-1) is present. In addition, ground information obtained from the survey boring carried out at the survey point R is obtained. Note that if known ground information is available, such as a history of a soil survey having been carried out in the past near the soil improvement block A, this information may be used and the reference point C may be set near the survey point R. Furthermore, if the survey point R is nearby, the reference point C may also be used in conjunction with any of the multiple points (A1 to A11) where the improvement body 40 is planned to be constructed.

[0057] <<<Investigation information acquisition process>>> Upon obtaining the ground information for the survey location R, the central processing unit 33 of the ground estimation device 30 receives instructions from the survey information acquisition unit 351, acquires the obtained ground information via the input device 31, and stores it in the survey data file 341 of the file device 34.

[0058] <Acquisition of ground information> As shown in FIG. 8, at least "depth (measured depth), soil properties, N value (measured N value), and columnar diagram" are acquired as ground information. The depth is the "measured depth" obtained by a standard penetration test, the N value is the "measured N value" of the measured depth obtained by the standard penetration test, and the columnar diagram (including soil classification) can be acquired by importing image data. In addition to this ground information, the borehole mouth elevation of the investigation borehole trace (A-1) can be acquired and the elevation value can be assigned to the measured depth. This ground information, etc. is associated with the borehole name (A-1) and stored in the investigation data file 341 of the filing device 34.

[0059] <Setting estimation conditions> Also, before or after the storage of the ground information, the estimation conditions are set and input via the input device 31 of the ground estimation device 30, and stored in the survey data file 341. The estimation conditions that need to be set and input include "averaging processing setting," "rotational torque correction setting," "soil quality judgment value setting," and "soil quality judgment threshold setting," as shown in Fig. 8.

[0060] The "averaging processing setting" is a setting for averaging data in a specified section in order to grasp the rough ground condition in the depth direction from the drilling data continuously obtained by the data logger 26 of the ground improvement drilling machine 20. There are "moving average setting" and "estimated depth comparison average setting". The "moving average setting" sets the distance of the previous and next sections for which data is collected, with an arbitrary reference depth (elevation value) as the median. Note that the reference depth should be set at intervals narrower than the actual measured depth. The "estimated depth comparison average setting" is a data section for comparing the rotational torque obtained at the reference point C or the construction point G with the actual measured N value and soil type classification at the survey point R, and sets the distance of the previous and next sections for which data is collected, with the actual measured depth as the median.

[0061] The "rotation torque correction setting" is a setting for performing rotation torque correction according to the speed change ratio of the actual drilling speed to the drilling speed set on the soil improvement drilling machine 20. Details will be described later, but the set drilling speed (on the soil improvement drilling machine 20), the torque during idling, and the ratio correction value are set.

[0062] The "soil quality judgment value setting" is a setting that assigns an arbitrary numerical value (soil quality judgment value) to the soil quality determined by soil quality judgment, and the "soil quality judgment threshold setting" is a setting of the threshold value of the rotational torque used when determining the soil quality in the depth direction based on the results of organizing and statistically processing the rotational torque obtained continuously in the depth direction, and sets an average threshold value and a variance threshold value.

[0063] ≪≪Drilling information acquisition process≫≫ The ground improvement drilling machine 20 is installed at a reference point C adjacent to the investigation point R shown in Fig. 7, and drilling is performed by inserting the drilling casing 27. During ground drilling at the reference point C, drilling data continuously acquired in the depth direction is input from the data logger 26 to the ground estimation device 30 via the input device 31.

[0064] Then, the central processing unit 33 receives a command from the drilling information acquisition unit 352 and calculates the instantaneous drilling speed for each predetermined time (Δt) based on the drilling time and depth. Then, the rotational torque, depth (depth of bottom end of excavation), and instantaneous drilling speed organized for each predetermined time (Δt) are stored in the drilling data file 342 of the filing device 34. After this, if there is any unnecessary data, such as missing data, it is deleted as appropriate.

[0065] As described above, considering that changes in the drilling speed affect the estimation of ground strength (N value), the speed is controlled so that the ground is drilled at a constant speed on the ground improvement drilling machine 20 side. The speed controlled on the ground improvement drilling machine 20 side is set and input as the "set drilling speed" in the rotation torque correction setting in the above estimation conditions.

[0066] ≪≪Soil quality determination process≫≫ When the drilling data is acquired, the central processing unit 33 receives a command from the soil quality determination unit 353 and determines the soil quality in the depth direction at the reference point C. The reference depth at which the soil quality has been determined is assigned a "soil quality determination value" corresponding to clayey soil or sandy soil as shown in FIG. 3(c), and these are associated with the reference depth and stored in the drilling data file 342.

[0067] <Procedure for determining soil quality> The soil quality is determined based on the rotational torque for each predetermined time (Δt) stored in the drilling data file 342 and the "soil quality determination threshold" stored in the survey data file 341. As shown in Fig. 9, the procedure is as follows: first, a statistical processing section is set based on multiple reference depths set in the "moving average setting" stored in the survey data file 341 and the distances before and after the reference depths as the median.

[0068] Next, the moving average of the rotating torque is calculated for each statistical processing section to average out the variation in the rotating torque. The variance of the rotating torque is also calculated to show the variation in the rotating torque. The average of the rotating torque serves as a reference value for the soil type classification, and the variance of the rotating torque can be used to evaluate the change and homogeneity of the soil layer from the degree of variation in the rotating torque.

[0069] The average and variance of the rotational torque for each statistical processing section are compared with the average and variance thresholds set in the "soil quality judgment threshold setting" stored in the survey data file 341. For example, Figures 3(a) and (b) show an example in which the average threshold is set to 1.25 and the variance threshold is set to 0.01. The average and variance thresholds may use the initial values ​​previously set in the "soil quality judgment threshold setting" in the survey data file 341, or may be appropriately adjusted and reset.

[0070] The adjustment can be performed by outputting a graph of the average and variance of the rotational torque and a columnar diagram of the survey point R stored in the survey data file 341 to an output device 32 such as a display, and the construction manager can visually compare the two. In this case, information on the adjusted threshold value is input to the ground estimation device 30 via an input device 31 such as a mouse or keyboard, and the initial value set in the "soil quality judgment threshold setting" may be corrected, or an additional threshold value may be stored.

[0071] After the thresholds are set in this way, as shown in Figures 3(a) and (b), first, for each of the average and variance of the rotational torque, it is assumed that the reference depth that does not exceed the threshold is clayey soil, and that the reference depth that exceeds the threshold is sandy soil. Then, it is determined that the reference depth where both the average and variance of the rotational torque do not exceed the threshold is clayey soil, and the other reference depths are sandy soil. This is based on the knowledge that the rotational torque is large in sandy soil and small in clayey soil, and that the variation (amount of change) of the rotational torque is small in clayey soil and large in sandy soil, as mentioned above.

[0072] <Assignment of soil quality judgment value> The reference depth at which the soil type has been determined in this way is assigned a "soil type determination value" corresponding to clayey soil or sandy soil, following the "soil type determination value" set in the "soil type determination value setting" stored in the survey data file 341. In Fig. 3(c), "0" is assigned to clayey soil and "2" is assigned to sandy soil. The "soil type determination value" may use a preset initial value, or may be adjusted appropriately and reset.

[0073] ≪≪Analysis preparation process≫≫ When the soil quality assessment process is completed, the central processing unit 33 receives instructions from the analysis preparation unit 354 and extracts the actual measured N value of survey point R, which is used as the objective variable when obtaining the N value estimation equation, as shown in Figure 9, together with the actual measured depth from the survey data file 341 and stores them in the analysis data file 343 of the filing device 34.

[0074] In addition, the analytical soil quality judgment value D and analytical rotation torque T used as explanatory variables when obtaining the N value estimation formula X The calculation results are stored in the analysis data file 343 of the file device 34. X The procedure for calculating will now be described with reference to FIGS.

[0075] <Calculation of analytical soil quality judgment value D> 9, the procedure for calculating the analytical soil quality judgment value D is as follows: first, a comparison section is set based on the "estimated depth comparison average setting" stored in the survey data file 341. The comparison section is set based on the actually measured depth and the distance in the depth direction from the actually measured depth set in the "estimated depth comparison average setting".

[0076] Next, for each comparison section, the average value of the soil quality judgment values ​​for each reference depth calculated in the soil quality judgment step is calculated and set as the analytical soil quality judgment value D. The calculated analytical soil quality judgment value D is associated with the actual measured depth and stored in the analytical data file 343. The soil quality judgment values ​​for each reference depth are stored in the drilling data file 342, and the actual measured depth is stored in the survey data file 341 as ground information.

[0077] << Rotational torque for analysis T X Calculation of Analysis torque T X 9, the calculation procedure is as follows: first, speed correction is performed on the rotational torque for each predetermined time (Δt) stored in the drilling data file 342. Then, ratio correction is performed to calculate the ratio-corrected rotational torque for each predetermined time (Δt).

[0078] 5(a), the speed correction is performed when the instantaneous drilling speed (actual measured value of the drilling speed) for each predetermined time (Δt) is lower than the set drilling speed on the ground improvement drilling machine 20 side. The speed correction rotational torque is calculated by multiplying the rotational torque for each predetermined time (Δt) by the ratio of the set drilling speed set on the ground improvement drilling machine 20 to the instantaneous drilling speed, and the calculation result is stored in the drilling data file 342 of the filing device 34.

[0079] The ratio correction is calculated by multiplying the speed-corrected rotational torque by the rotational torque increase value and the ratio correction value. The ratio correction value is set in the "rotational torque correction setting" stored in the survey data file 341, and the rotational torque increase value is calculated by subtracting the "idling torque" from the rotational torque for each predetermined time (Δt). The "idling torque" is set in the "rotational torque correction setting" stored in the survey data file 341. The ratio-corrected rotational torque calculated in this way is stored in the drilling data file 342 of the filing device 34.

[0080] Thereafter, for the ratio-corrected rotational torque for each predetermined time (Δt), the average value is calculated for each comparison section as the average value T of the ratio-corrected rotational torque. The calculated average value T of the ratio-corrected rotational torque is associated with the actual measured depth of the survey point R and stored in the analysis data file 343. The comparison section is as explained in the calculation of the soil quality judgment value D for analysis.

[0081] After calculating the average value T of the ratio-corrected rotating torque corresponding to the actual measured depth in this way, a change range correction is performed to set the change range in the depth direction of the average value T of the ratio-corrected rotating torque and the change range in the depth direction of the N value (actual measured N value) at the survey point R to 1:1. The change range correction is performed by applying an exponential function of X with the average value T of the ratio-corrected rotating torque as the base to the analytical rotating torque T. X Then, calculate X using the following formula (1). The calculated rotational torque for analysis T X is associated with the actually measured depth and stored in the analysis data file 343.

[0082] TIFF0007647447000001.tif28170

[0083] <<N-value estimation formula acquisition process>> As a result of the above-mentioned analysis preparation process, as shown in FIG. 10, the analysis data file 343 of the file device 34 contains the actual measured N value at the survey point R as the objective variable when obtaining the N value estimation formula, the analysis soil judgment value D and the analysis rotation torque T as explanatory variables. XThe above data is stored in the storage unit 354. The central processing unit 33 then receives a command from the estimation equation acquisition unit 355 and performs multiple regression analysis using the above data. Figure 4 shows an example of the multiple regression analysis results and the soil quality judgment results being output to the output device 32 such as a display.

[0084] After going through the above steps, an N-value estimation formula such as the following equation (2) is obtained, and then the ground improvement drilling machine 20 used when drilling the reference point C is installed at the development point G where the soil classification and ground strength are to be estimated, as shown in Figure 1, and drilling work is performed.

[0085] TIFF0007647447000002.tif20170

[0086] <<<Estimated N value acquisition process for development site G>> After acquiring the drilling data for the construction site G, first, the rotational torque acquired as the drilling data is used to acquire the soil quality judgment result through a drilling information acquisition process and a soil quality judgment process. The procedure is the same as the procedure for acquiring the soil quality judgment result for the reference starting point C described above, and the average and variance of the rotational torque are calculated for each statistical processing section. After this, the soil quality for each reference depth is judged based on the soil quality judgment thresholds (average and variance thresholds) used in the soil quality judgment for the reference starting point C, and a soil quality judgment value is assigned to the reference depth for which the soil quality was judged.

[0087] Next, an analysis preparation step is carried out to obtain the estimated soil quality judgment value D' and the estimated rotation torque T X The procedure is to obtain the soil quality judgment value D and the rotation torque T X The procedure for obtaining the estimated soil quality judgment value D' and the estimated rotation torque T X The information acquired by carrying out the process from the hole drilling information acquisition process to the analysis preparation process, including ``'', is stored in the estimation data file 345 of the filing device 34.

[0088] Estimation soil quality judgment value D' and estimation rotation torque T XWhen the N-value estimation unit 356 receives a command from the central processing unit 33, the estimation soil judgment value D' and the estimation rotation torque T are input to the N-value estimation formula stored in the regression analysis result file 344. X ' to calculate the estimated N value of the construction site G. The estimation result is stored in the estimation data file 345 of the filing device 34 in association with the site number (A1) that sets the construction site G.

[0089] As an example, Fig. 11 shows the calculation result of the estimated N-value at development site G outputted on an output device 32 such as a display. In this way, it is possible to estimate the soil type and ground strength of development site G at the same time as drilling work to provide guide holes 41 at development site G using the ground improvement drilling machine 20. The N-value shown in Fig. 11 is the actually measured N-value at investigation site R.

[0090] This makes it possible to inject ground improvement materials into the ground according to improvement specifications that correspond to the actual ground conditions at the construction site G, and to construct the improved body 40, which makes it less likely that defects such as insufficient finished shape will occur, and contributes to improving the quality of the improved body.

[0091] <<Area-wide ground estimation for ground improvement block A>> For example, when the improvement range is divided into small blocks (A-1BL, A-2BL) such as ground improvement block A shown in Figure 7, and each block has survey borehole traces, the N-value estimation formulas (A-1, A-2) may be obtained for each small block (A-1BL, A-2BL).

[0092] After that, at each of the sites (A1 to A11) where the improvement body 40 is planned to be constructed, drilling work is carried out using the soil improvement drilling machine 20, and the soil type and soil strength are estimated while appropriately selecting the above N-value estimation formulas (A-1, A-2). In this way, it becomes possible to obtain the estimated results of soil type and soil strength over the entire soil improvement block as shown in Figure 7.

[0093] This makes it possible to identify at an early stage any locations where problems such as runoff of ground improvement liquid may occur when construction work is carried out at the sites (A1 to A11) where the improvement body 40 is planned to be constructed. This makes it possible to quickly implement effective measures and improve the ease of construction of ground improvement work.

[0094] In addition, when selecting the N-value estimation formula (A-1, A-2) at points (A1 to A11), if the points are located in small block (A-1BL), N-value estimation formula (A-1) may be used, and if the points are located in small block (A-2BL), N-value estimation formula (A-2) may be used. Either of the more suitable estimation formulas may be selected after appropriate verification.

[0095] The ground estimation method and ground estimation system 10 of the present invention are not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0096] In this embodiment, the case where there is only one reference point C for the survey point R has been exemplified, but a plurality of reference points C may be provided for the survey point R.

[0097] In this embodiment, the rotational torque for each predetermined time (Δt) is corrected for speed and ratio to calculate the ratio-corrected rotational torque for each predetermined time (Δt). After this, the average value T of the ratio-corrected rotational torque corresponding to the actual measured depth is calculated, and the change range correction is performed to obtain the rotational torque for analysis T X The following is calculated. [Explanation of symbols]

[0098] 10. Ground Estimation System 20 Ground improvement drilling machine 21 Drilling machine body 22 Water Pump 23 Pressure Sensor 24 Displacement sensor 25 Pressure Sensor 26 Data Logger 27 Drilling Casing 271 Ring Bit 30 Ground estimation device 31 Input Devices 32 Output Device 33 Central Processing Unit 34 File Device 341 Survey Data File 342 Drilling Data File 343 Data files for analysis 344 Regression analysis result file 345 Estimation Data File 35 Main memory 351 Investigation Information Acquisition Division 352 Drilling Information Acquisition Unit 353 Soil quality determination department 354 Analysis Preparation Department 355 Estimated formula acquisition part 356 N-value estimation section 40 Improved body 41 Guide hole G Creation point (drilling point) R Survey location C Reference point

Claims

1. A ground estimation method for estimating ground information at a drilling point based on a rotational torque during drilling, comprising: The ground strength among the ground information is estimated using a previously acquired N-value estimation formula; The N value estimation formula is A drilling information acquisition process of drilling a reference point set near a survey point where the actual measured N value for each actual measured depth is known, and acquiring a rotation torque; a soil quality determination step of assigning an arbitrary soil quality determination value to the soil quality at each depth of the reference point to obtain a soil quality determination result for the reference point; The rotational torque at the reference point is corrected to make the speed in the depth direction constant, and then a representative value corresponding to the actual measured depth is calculated as the rotational torque for analysis; an analysis preparation step of calculating a representative value corresponding to the actual measured depth from the soil quality judgment result of the reference point as a soil quality judgment value for analysis; An estimation equation acquisition process for performing a regression analysis using the measured N value as a response variable and the analytical rotation torque and the analytical soil quality judgment value as explanatory variables; A ground estimation method characterized by being calculated as follows.

2. The ground estimation method according to claim 1, In the analysis preparation step, the rotation torque for analysis is A ground estimation method characterized in that a representative value corresponding to the actual measured depth after velocity correction is obtained by performing a variation range correction to make the variation range in the depth direction equal to the variation range of the actual measured N value.

3. The method for estimating ground conditions according to claim 1 or 2, In the soil quality determination step, the soil quality for each depth of the reference point is determined as follows: A ground estimation method characterized in that a soil quality judgment threshold for rotational torque is set by comparing the known soil quality classification of the survey site with the rotational torque of the reference site, and a judgment is made based on the rotational torque of the reference site.

4. The ground estimation method according to claim 3, The soil type determination threshold value of the rotational torque includes an average threshold value and a variance threshold value, The average threshold is set based on an average calculated for each statistical processing section set in the depth direction from the rotation torque at the reference point and a known soil type classification at the survey point; A ground estimation method characterized in that the variance threshold is set based on the variance calculated for each statistical processing section from the rotational torque of the reference point and the known soil type classification of the survey point.

5. The ground estimation method according to claim 3 or 4, A ground estimation method, characterized in that the soil type classification of the ground information at the drilling point is determined based on the rotational torque at the drilling point and the soil type determination threshold.

6. A ground estimation system using the ground estimation method according to any one of claims 1 to 5, A ground drilling machine that drills the drilling point and the reference point; A ground estimation device that calculates at least the N-value estimation formula, The ground estimation device includes: A drilling information acquisition unit that acquires a rotational torque output from the ground drilling machine; a soil quality determination unit that assigns an arbitrary soil quality determination value to the soil quality at each depth at the reference point to obtain a soil quality determination result for the reference point; an analysis preparation unit that calculates the analysis rotation torque from the rotation torque of the reference point acquired by the drilling information acquisition unit, and calculates the analysis soil judgment value from the soil judgment result of the reference point acquired by the soil judgment unit; an estimation equation acquisition unit that performs a regression analysis using the rotational torque for analysis and the soil quality judgment value for analysis calculated by the analysis preparation unit as explanatory variables and the measured N value as a response variable to calculate the N value estimation equation; A ground estimation system comprising:

7. The ground estimation system according to claim 6, A ground estimation system, characterized in that the ground drilling machine is a ground improvement drilling machine.

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