Drilling rod system

Abstract

In columnar ground improvement methods, unexpected influences such as groundwater during and immediately after cement grout injection and mixing often lead to "deformation of the columnar ground improvement body." Current construction management systems make it difficult to grasp the influence of groundwater during construction. This poses a quality control challenge for columnar ground improvement methods. [Solution] By managing and monitoring the solidification status of the columnar ground improvement body at the tip of the drilling rod after cement milk injection and mixing using pH values, the quality control issues of the columnar ground improvement method can be resolved.

Description

Technical Field

[0001] The present invention relates to a method for improving columnar ground by injecting cement milk.

Background Art

[0002] The columnar ground improvement method is a method of creating a columnar ground improvement body 13 having a predetermined strength by injecting, stirring, and mixing cement milk (a slurry-like mixture of cement and water) while excavating the ground to be improved with a ground improvement construction machine 1 as shown in FIG. 1. And the construction management of the columnar ground improvement method is carried out by a construction management device composed of various sensors and the like linked to a recording device to check and record ground improvement construction data such as depth, stirring rotation speed, and cement milk injection volume.

[0003] However, when affected by unexpected groundwater or the like (increase in groundwater volume, high permeability, confined water) during and immediately after the injection and stirring of cement milk, there are many cases where the columnar ground improvement body (cement solidified body) fails to obtain a predetermined shape and strength, resulting in "deformation of the columnar ground improvement body". Quality control and quality confirmation of the completed columnar ground improvement body (degree of completion of the columnar ground improvement body) must wait for the results of uniaxial compression tests of specimens collected by mold cores or boring cores about 7 days or 28 days after the material age. As a result, if a predetermined shape and strength of the columnar ground improvement body cannot be obtained, it is necessary to select a construction method change.

[0004] However, during that time, construction often proceeds or is completed, and dealing with such "deformation of the columnar ground improvement body (especially poor solidification)" is a backwork, which causes major problems such as construction method change, construction period extension, and cost increase. In addition, it is difficult to grasp the influence of groundwater during construction by the current construction management device. This has become an issue in the quality control of the columnar ground improvement method.

[0005] In other words, if unexpected groundwater or other factors are present during or immediately after the injection and mixing of cement grout, the cement grout will be washed away (the amount of cement grout injected and mixed into the columnar ground improvement body will decrease), inevitably causing the pH (hydrogen ion concentration) value in the columnar ground improvement body to drop unexpectedly, which is the background to the aforementioned problem (it is known that the solidification status of cement is correlated with the pH value).

[0006] In other words, if the solidification status of the columnar ground improvement body at the tip of the drilling rod after cement grout injection and mixing can be managed and understood by its pH value, one of the quality control challenges of the columnar ground improvement method will be solved. The drilling rod system is a management method that manages and understands the pH value of this columnar ground improvement body as a characteristic value. Incidentally, methods for managing and understanding the pH value of columnar ground improvement bodies (cement-improved bodies) are disclosed in Patent Document 1 "JP-A-5-239826" and Patent Document 2 "Patent 4721268," and their outlines are described below. Patent Document 1: "Japanese Patent Publication No. 5-239826" "Method for process management of ground improvement work using a jet stream" • Insert a sensor rod equipped with a pH sensor into the ground surrounding the improved liquid jet injection pipe. The system measures the pH value in the soil that has changed due to the improved liquid jet, and detects the location where the improved liquid jet reached based on the position of the pH sensor that detected the change in pH value. This is a process management method for ground improvement work using jet streams.

[0007] Patent Document 2: "Patent 4721268" "Measurement device for improved diameter and method for measuring improved diameter" A rod-shaped member is inserted into the casing that penetrates the ground, with its lower end extending horizontally from inside the casing to the interface between the improved ground and the unimproved ground. A detection sensor is installed at the tip of the rod-shaped member. The interface is identified by a detection sensor that detects at least one of the following: load changes, temperature changes, or pH value changes at the interface. Based on the amount of horizontal penetration of the rod-shaped member into the improved body, the diameter of the improved body is measured by a device for measuring the improved body diameter. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 5-239826 [Patent Document 2] Patent No. 4721268 [Overview of the project] [Problems that the invention aims to solve]

[0009] In current evaluations of cement grout solidification, real-time evaluation is not performed. Instead, evaluations are based on test results approximately 7 or 28 days after cement grout injection and mixing. This necessitates the aforementioned evaluation period, inevitably leading to longer construction periods and higher construction costs. Therefore, the problem that this invention aims to solve is to enable real-time evaluation of the solidification status of columnar ground improvement bodies, and the objective is to develop an apparatus and evaluation method for this purpose. [Means for solving the problem]

[0010] The inventors of this invention have diligently pursued development to solve the above problems. As a result, the following means are provided. As method 1, A drilling rod system is provided, which includes a transport path 15 inside the drilling rod for dispensing cement grout for columnar ground improvement, and a drilling head drill 11 at the tip of the drilling rod, The drilling rod system is characterized by comprising the drilling head drill 11, a discharge port 17 for discharging cement grout, a stirring blade 10 for advancing the excavation of the ground to be improved and stirring and mixing the cement grout with the ground soil to be improved, a leading tip plate 19 for leading the excavation of the ground to be improved and preventing the center of the columnar improved body from shifting, and a pH sensor 18. To provide.

[0011] As method 2, The drilling rod system according to means 1, characterized in that it is equipped with a protective on / off valve 23 for protecting the pH sensor 18, To provide.

[0012] As method 3, A drilling rod system according to either means 1 or means 2, characterized by having an opening 20 that serves as a pH sensor protection space and a pH sensor detection space. To provide.

[0013] As method 4, A control method for measuring the pH value of a mixture of cement grout and soil to be improved when the drilling head drill 11 rises after it has drilled through the ground to be improved using the drilling rod system described in any of means 1 to 2. To provide.

[0014] As method 5, A method for measuring the pH value, When the pH value during the preliminary mix design test is defined as pH value A, and the pH value during drilling, stirring, and mixing is defined as pH value B, The management method according to method 4, characterized in that it includes a means for increasing the amount of cement milk when the value obtained by subtracting pH value B from pH value A is 0.5 or more. To provide.

[0015] By the way, the opening of means 3 is a notch on the rod side of the tip guide plate, and the space into which the pH sensor discharges is located. This space can be of any shape, but preferably it is roughly rectangular as shown in Figure 5. By the way, method 4 is a method for managing the drilling head drill 11 when it is "rising". The reason for this is that when it is descending, drilling is taking place, so there is a possibility that the pH sensor may be damaged, and when it is descending, only cement grout is being discharged, so there is no need to measure the pH. On the other hand, when it is rising, drilling is finished and the cement grout and soil are mixed, so the pH is measured when it rises.

[0016] Incidentally, the ascent and descent are as shown in Fig. 1. Incidentally, the pH sensor refers to the sensing part of a device that measures the degree of acidity and alkalinity of an object. The sensing part has various applications (aqueous solutions, individuals, soil, etc.), and the pH sensor used in the present invention may be any type as long as it can measure the degree of acidity and alkalinity. However, a rod-shaped one protected by a metal case that can measure the inside of the soil is preferred. In addition, the place indicating numerical values such as the degree of acidity and alkalinity So-called display management device may be in a place different from the sensing part. Effects

[0017] In the present invention, the quality control of the columnar ground improvement body 13 can be objectively grasped in real time. Therefore, the occurrence of "abnormalities in the columnar ground improvement body (columnar ground improvement bodies with poor solidification)" can be suppressed. Also, even when "abnormalities in the columnar ground improvement body" occur, it is possible to quickly respond to them, and it is possible to suppress changes in the construction method, extension of the construction period, and increase in costs due to rework, etc.

Brief Explanation of Drawings

[0018] [Figure 1] It is an overall view of the construction of the columnar ground improvement method. [Figure 2] It is an overall view of the ground improvement device. [Figure 3] It is a related diagram of the tip of the drilling rod and the pH sensor. (If the above figure is taken as the bottom view, the following figure is its front view) [Figure 4] It is a cross-sectional view of the drilling rod. [Figure 5] It is a related diagram of the tip guide plate. [Figure 6] It is a related diagram of the detection part of the pH sensor. (If the above figure is taken as the front view, the following figure is its bottom view)

Embodiments for Carrying Out the Invention

[0019] Hereinafter, an example of an embodiment for carrying out the invention will be described, but it is only an example and is not limited to this embodiment. Figure 1 is an overall diagram of the construction of the columnar ground improvement method. Specifically, cement milk, which is a mixture of cement and water in the mixing plant 2, is pumped into the drilling rod 8 by the cement milk pumping machine 4 through the cement milk transport pipe 5 and then into the drilling rod 8 by the cement milk filling device 6. The ground improvement construction machine 1 then injects, agitates, and mixes the cement milk while drilling the ground to be improved with the drilling rod 8 and the rotating blades 10 of the drilling head drill 11 to create a columnar ground improvement body 13 with a predetermined strength. The drilling rod 8 and drilling head drill 11 perform drilling, stirring, and mixing while discharging cement grout from the cement grout discharge port 17 at the tip of the drilling rod as they descend. Once they have descended to a predetermined depth, they ascend while continuing to stir and mix. Furthermore, during drilling, stirring, and mixing, the drilling rod 8 and the drilling head drill 11 may rotate together, so a co-rotation prevention wing 12 is provided.

[0020] Figure 2 is an overall view of the ground improvement device. The cement grout filled in the transport channel 15 inside the drilling rod is discharged from the cement grout discharge port 17 of the drilling head drill 11, and the rotation of the stirring blade 10 mixes the cement grout with the soil to be improved. To guide the excavation of the ground to be improved and prevent the columnar ground improvement body 13 from shifting its center, a leading plate 19 is provided at the center of the leading plate, and a leading plate opening (pH sensor detection space) 20 is provided at that location to measure the pH. The pH sensor cord 27 is installed inside the pH sensor protective tube 25. A pH sensor detection data transmission device 14 is attached to the head of the drilling rod, and the detection data is transmitted to a PC recording device 16. Regarding the increased injection of cement grout, if the value obtained by subtracting the pH value B during excavation, stirring, and mixing from the pH value A during the pre-mix test is 0.5 or higher, it is considered an abnormal condition and the amount of cement grout should be increased. Preferably, the amount of cement grout should be increased when it is 1.0 or higher, and more preferably when it is 1.5 or higher. The reason for this is that if the subtracted value becomes large, solidification failure will occur.

[0021] Figure 3 is a diagram showing the drilling rod tip and the pH sensor. The drilling rod tip 22 has a pH sensor protection valve 23 to protect the pH sensor 18 during descent (A) when drilling, stirring, and mixing is performed, and is closed during descent while drilling and stirring. During the stirring and rising phase (B) 31, the pH sensor 18 and pH sensor protection tube 25 protrude below the lowest end position 30 of the drilling rod, causing the pH sensor protection valve 23 to be pushed out and open. The protective on / off valve 23 can be made of any material, but urethane resin is preferred.

[0022] Figure 4 is a cross-sectional view of the drilling rod. Inside the drilling rod 8 is a pH sensor protection tube 25 with a pH sensor cord 27 built into the center, and a drilling rod transport path 15 filled with cement grout is located around its outer circumference.

[0023] Figure 5 is a diagram showing the leading plate at the tip. The leading plate 19 at the tip, which guides the excavation of the ground to be improved and prevents the center of the columnar ground improvement body from shifting, is inserted into the tip of the excavation rod and fixed in place by welding 28. The leading plate 19 at the tip is provided with an opening 20 between the lowest end position 30 of the drilling rod tip and the tip 21 of the leading plate at the tip, which serves as a space for protecting the pH sensor and detecting the pH sensor. The leading plate 19 at the tip can be made of any material, but high-tensile steel, wear-resistant steel, or hardened steel is preferred.

[0024] Figure 6 is a diagram showing the pH sensor detection unit. An opening 26 is provided at the tip of the pH sensor protective tube 25 to widen the pH sensor detection range. [Explanation of Symbols]

[0025] 1 Ground improvement construction machinery 2. Mixing plant (equipment for mixing cement and water) 3 Generators 4. Cement milk pump 5. Cement milk transport pipe 6. Cement mill filling device 7. Pumping cement milk 8 drilling rods 9 Leader (Drilling Rod Support) 10 Rotor blades 11 Drill head drill 12 Anti-rotation wings 13 Column-shaped ground improvement body 14 pH sensor detection data transmission device (drilling rod head) 15. Internal transport path for drilling rod (filled with cement grout) 16. Send detection data to the PC recording device. 17. Cement milk dispenser 18 pH sensors 19 Tip guide plate 20. Leading plate opening at the tip (pH sensor detection space) 21 Tip of leading plate 22. Tip of the drilling rod 23 pH sensor protection valve (closed during agitation and excavation descent, open during agitation and excavation descent) 24 pH sensor protective on / off valve mounting bracket 25 pH sensor protective tube (installed inside the drilling rod) 26 pH sensor protective tube tip opening 27 pH sensor code 28 Insertion and welding fixation of the tip of the drilling rod. 29 Center of columnar improved pile 30. Lowermost position of the tip of the drilling rod 31. Configuration of pH sensor during rising and falling G Ground surface

Claims

1. A drilling rod system is provided, which includes a transport path 15 inside the drilling rod for dispensing cement grout for columnar ground improvement, and a drilling head drill 11 at the tip of the drilling rod, The drilling rod system is characterized in that the drilling head drill 11 is equipped with a discharge port 17 for discharging cement grout, a stirring blade 10 for advancing the excavation of the ground to be improved and stirring and mixing the cement grout with the ground soil to be improved, a leading tip plate 19 for leading the excavation of the ground to be improved and preventing the center of the columnar improved body from shifting, and a pH sensor 18.

2. The drilling rod system according to claim 1, characterized in that it is provided with a protective on / off valve 23 for protecting the pH sensor 18.

3. The drilling rod system according to claim 1 or claim 2, characterized in that it is provided with an opening 20 which serves as a pH sensor detection space.

4. A control method for measuring the pH value of a mixture of cement grout and soil to be improved when the drilling head drill 11 rises after it has drilled through the ground to be improved using the drilling rod system according to claim 1 or 2.

5. A method for measuring the pH value, When the pH value during the preliminary mix design test is defined as pH value A, and the pH value during excavation, stirring, and mixing is defined as pH value B, The management method according to method 4, characterized in that it includes a means for increasing the amount of cement milk when the value obtained by subtracting pH value B from pH value A is 0.5 or more.

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