Penetration testing apparatus

Abstract

To provide a penetration testing device applicable even to a low-strength improved ground.SOLUTION: A penetration test device 4 for performing a penetration test on a hole wall 21 of a measurement hole 2 in the measurement hole 2 includes a penetration body holding means 44 for holding a penetration body, a slide mechanism 46 for moving the penetration body holding means 44 toward and away from the hole wall 21 of the measurement hole 2, and a measuring means 45 for measuring a penetration resistance force when the penetration body penetrates the hole wall 21.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a penetration testing device. [Background technology]

[0002] Quality evaluation tests are sometimes conducted on improved ground, which is made by mixing soft ground with a solidifying material, to ensure that the desired quality is achieved. Methods for quality evaluation tests on improved ground include conducting strength tests on samples collected during construction and then curing them indoors at a specified age, or conducting strength tests on samples collected in situ after construction. Strength tests must be conducted at specified depths to measure the strength at the specified age for strength evaluation (e.g., 3 days, 7 days, and 14 days). Non-Patent Document 1 discloses a needle penetration test, which can easily confirm the strength of ground, as a method for measuring the uniaxial compressive strength of test specimens. The needle penetration test involves penetrating a needle into the ground, measuring the penetration length L and the load P at the time of needle penetration, and calculating the penetration gradient Np (= P / L), which is the ratio of the load P to the penetration length L. The uniaxial compressive strength is then estimated from this penetration resistance (penetration gradient) Np.

[0003] When conducting strength tests on samples cured indoors, it is necessary to consider that differences in curing conditions will result in differences in quality compared to in-situ improved specimens. Furthermore, when collecting specimens in-situ, specimens must be collected from a specified depth at each specified age, which is time-consuming, and also requires time and effort for transporting and handling the specimens.

[0004] For this reason, the applicant has disclosed in Patent Document 1 a method for conducting in-situ strength tests on improved ground, in which a test device is inserted into a measurement hole formed in the improved ground and a penetration needle is inserted from the test device toward the hole wall to measure the strength of the improved ground from the penetration resistance and penetration amount. The test device in Patent Document 1 moves up and down within the measurement hole and rotates around a vertical axis (an axis extending in the depth direction of the measurement hole), making it possible to measure multiple locations circumferentially and in multiple stages in the depth direction of the measurement hole. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Geotechnical Society Standard, Standard Number: JGS3431-2012, Standard / Standard Name: Needle Penetration Test Method [Patent documents]

[0006] [Patent Document 1] Patent No. 7476135 Summary of the Invention [Problem to be solved by the invention]

[0007] In ground improvement work, multiple ground improvement piles (ground improvement bodies) may be installed in a series with overlapping surfaces for various construction purposes. If the strength of the ground improvement piles installed first is high, the mixing blades may not be able to rotate fully in the overlapping area, which may reduce the workability or even make the subsequent ground improvement piles impossible to install. Therefore, it is important to understand the strength development trends at an early age after the construction of the improvement body. When conducting a needle penetration test, the penetration load is less affected by tip resistance due to the small cross-sectional area of ​​the needle and more by surface friction. However, surface friction is less likely to occur in low-strength improved ground, which may prevent the penetration load from being detected and may make measurement impossible.

[0008] An object of the present invention is to propose a penetration test device that can be applied to improved ground with low strength. [Means for solving the problem]

[0009] To solve the above problem, the present invention provides a penetration test device that performs a penetration test on the hole wall of a measurement hole within the measurement hole, and includes a penetrating body holding means that holds a penetrating body, a sliding mechanism that moves the penetrating body holding means back and forth toward the hole wall of the measurement hole, and a measuring means that measures the penetration resistance force when the penetrating body penetrates the hole wall, and a mechanism that replaces the penetrating body with a replacement penetrating body having a larger diameter than the penetrating body when the measured value of the penetration resistance force is equal to or less than a threshold value.

[0010] With this penetration test device, if it is determined that the ground to be measured is low in strength and that measurement using the first penetrator is difficult, a penetration test can be performed by replacing the first penetrator with a second penetrator (a replacement penetrator) with a larger diameter than the first penetrator. In other words, the penetration test device of the present invention can collect and evaluate measurement data even for low-strength improved ground. Therefore, for example, in ground improvement work that includes overlapping sections, by determining the estimated strength of the completed ground improvement body early and judging the condition of the completed ground improvement body based on this estimated strength, reliable construction can be achieved, and ultimately, poor construction in the overlapping sections and damage to the construction machine can be avoided.

[0011] The penetration test device preferably further includes a refill case for storing the replacement penetrator, and a determination means for transmitting a signal to the penetrator holding means when the measured value of the penetration resistance force is equal to or less than a threshold value. The refill case is disposed above the penetrator holding means when retracting, and upon receiving the signal, the penetrator holding means releases the penetrator used to measure the needle penetration resistance force and holds the replacement penetrator ejected from the refill case. In this way, the penetrator can be automatically replaced within the measurement hole.

[0012] If the refill case contains a plurality of replacement penetrators with different cross-sectional areas, it will be possible to perform measurements using penetrators with diameters that correspond to the strength of the improved ground. The replacement penetrator may be a round bar having a constant diameter in the longitudinal direction or a round bar having a conical tip. [Effects of the Invention]

[0013] According to the penetration test device of the present invention, it is possible to collect measurement data in situ and perform evaluation even on improved ground with low strength. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a plan view showing an example of ground improvement work according to an embodiment of the present invention. [Figure 2] This is a perspective view showing an overview of the test situation for the improved ground quality evaluation method. [Figure 3] 1 is a flowchart of a method for evaluating the quality of improved ground. [Figure 4] 1A and 1B are conceptual diagrams showing an example of the hole-making process, where (a) shows the pipe insertion and (b) shows the pipe removal. [Figure 5] FIG. 1 is a cross-sectional view showing an outline of a penetration test device. [Figure 6] 1A and 1B are diagrams showing a part of a penetration test device, in which (a) is a cross-sectional view and (b) is a cross-sectional view taken along the line AA of (a). [Figure 7] This is a conceptual diagram of the correlation equation between penetration gradient and unconfined compressive strength. DETAILED DESCRIPTION OF THE INVENTION

[0015] In this embodiment, we will explain a case where a penetration test device is used to conduct a penetration test in situ to evaluate the quality of the improved ground in a ground improvement work in which multiple ground improvement bodies 1, 1, ... are installed in a mutually overlapping state, as shown in Figure 1. Figure 1 is a plan view showing an example of ground improvement work.

[0016] In a penetration test, a penetration needle (penetrator) is penetrated into the object, and the penetration load and penetration length are measured. The penetration load is composed of the tip resistance force of the tip of the penetration needle and the circumferential friction force of the penetration needle. On the other hand, since the cross-sectional area of ​​the tip of the penetration needle is extremely small, the tip resistance force has little effect on the penetration load, and the circumferential friction force has a large effect. However, when the measurement object has low strength, such as improved ground at a young age, circumferential friction force is unlikely to occur when the penetration needle penetrates. Therefore, in this embodiment, when the penetration load cannot be measured with a penetration needle, a penetration body with a large cross-sectional area is used to perform the penetration test.

[0017] Figure 2 shows an overview of the test conditions using the penetration test device of this embodiment. As shown in Figure 2, in this embodiment, the age change and strength characteristics are verified in situ in the area where a ground improvement body 1b to be constructed later overlaps a part of the constructed ground improvement body 1a. Figure 3 shows the improved ground quality evaluation method of this embodiment. As shown in Figure 3, the improved ground quality evaluation method of this embodiment includes a hole drilling step S1, a penetration test step S2, a strength estimation step S3, and a strength comparison step S4.

[0018] The drilling step S1 is a step of forming a measurement hole 2 in the constructed ground improvement body 1a. As shown in FIG. 2, the measurement hole 2 is preferably formed in a portion of the constructed ground improvement body 1a that will overlap with the ground improvement body 1b to be constructed later. FIG. 4 is a conceptual diagram of the drilling step S1. In this embodiment, as shown in FIGS. 4(a) and 4(b), a pipe 3 is inserted into the constructed ground improvement body 1a and then the pipe 3 is pulled out to form the measurement hole 2. Note that when a penetration test is conducted on the constructed ground improvement body 1a after the overlap construction date, the measurement hole 2 may be formed in a portion of the constructed ground improvement body 1a that will not overlap with the ground improvement body 1b to be constructed later.

[0019] The penetration test process S2 is a process of conducting a penetration test on the hole wall of the measurement hole 2. Figure 5 shows the construction status of the penetration test process S2. In this embodiment, the penetration test device 4 inserted into the measurement hole 2 is rotated around the vertical axis (i.e., the central axis of the measurement hole 2) within the measurement hole 2 and moved up and down, thereby performing measurements at multiple locations circumferentially and in multiple stages in the depth direction of the measurement hole 2. In this embodiment, the penetration test is performed every day from the material age of 1 day until the day before the overlap construction day (for example, material age of 4 days).

[0020] In the penetration test process S2, a first penetration test is first performed using a penetration needle 41 (penetrator). If the measured value of the penetration resistance force from the penetration test exceeds a threshold (in this embodiment, if a load is detected), the process proceeds to the strength estimation process S3. On the other hand, if the measured value of the penetration resistance force is equal to or less than the threshold (in this embodiment, if a load is not detected), a second penetration test is performed using a penetration rod 42 (penetrator) with a larger diameter than the penetration needle 41. The same penetration test device 4 is used for the first and second penetration tests. Here, the penetration needle 41 is a needle (a cotton needle No. 2, a large needle (φ0.84 mm or 0.89 mm, length 54.5 ± 1.4 mm)) specified in the "Geotechnical Society Standards, Standard Number: JGS3431-2012, Standard / Standard Name: Needle Penetration Test Method" (Geotechnical Society Standards, Standard Number: JGS3431-2012, Standard / Standard Name: Needle Penetration Test Method). The penetration rod 42 is a round rod that is thicker than the penetration needle 41, has a large cross-sectional resistance, and has a constant diameter in the longitudinal direction (for example, a diameter of 3 mm to 5 mm), or has a conical tip.

[0021] The penetration test device 4 is housed in a housing 5 that is inserted into the measurement hole 2. The penetration test device 4 is equipped with a refill case 43, a penetrator holding means 44 disposed below the refill case 43, a slide mechanism 46 that moves the penetrator holding means 44 toward and away from the hole wall 21 of the measurement hole 2, a measurement means 45 that measures the penetration resistance force when the penetrator penetrates the hole wall 21, and a determination means (not shown) that compares the measurement result by the measurement means 45 with a threshold value.

[0022] The housing 5 is made of a hollow cylindrical member with closed upper and lower ends. The housing 5 is provided with a reaction arm 51 that can move forward and backward or rotate relative to the housing 5. A plurality of rotating wheels 52, 52, ... are provided on the upper part of the housing 5. Furthermore, openings 53 that penetrate from the inside to the outside are formed in two locations in the housing 5, corresponding to the positions of the penetrator holding means 44 (penetrator) and the reaction arm 51. The number and arrangement of the openings 53 in the housing 5 may be determined as appropriate.

[0023] The reaction arm 51 is provided above the penetrator holding means 44. The reaction arm 51 moves back and forth or rotates due to the power of an arm motor (not shown), causing it to protrude from the opening 53 to the outside of the housing 5 and come into contact with the hole wall 21. The housing 5 is fixed to the measurement hole 2 by pressing the reaction arm 51 against the hole wall 21. The arm motor is driven by power (electricity) supplied from a power source.

[0024] The rotating wheel 52 protrudes outward from the outer surface of the housing 5, or is provided so as to be able to move laterally back and forth relative to the housing 5 and can abut against the hole wall 21. The rotating wheel 52 rotates horizontally around its vertical axis due to the rotational force of a wheel motor (not shown). The wheel motor rotates using power (electricity) supplied from a power source (not shown). The rotating wheel 52 travels on the surface of the hole wall 21 of the measurement hole 2, causing the housing 5 to rotate around its vertical axis.

[0025] The housing 5 is suspended by a suspension means 54 disposed at the opening of the measurement hole 2 . The suspension means 54 is composed of, for example, a wire 54a attached to the housing 5, a reel 54b around which the wire 54a is wound, a motor 54c that applies a rotational force to the reel 54b, and a stand 54d that supports the reel 54b and the motor 54c. The wire 54a wound around the reel 54b is wound up and let out by rotating the reel 54b with the power of the motor 54c, and the housing 5 moves up and down within the measurement hole 2 accordingly.

[0026] FIG. 6 shows the refill case 43 and the penetrating body holding means 44. As shown in FIGS. 6(a) and (b), the refill case 43 is a container that stores replacement penetrating bodies (penetrating rods 42) and is disposed above the retracted penetrating body holding means 44. A plurality of replacement penetrating rods 42 with different cross-sectional areas are stored in the refill case 43. The refill case 43 is a hollow box-shaped container, and is provided with a pushing means 431 inside. The pushing means 431 is provided in the ceiling of the refill case 43 and applies a force that presses the penetrating rods 42 (fasteners 47) downward.

[0027] The bottom end of the refill case 43 can be opened and closed by a plate-shaped slide mechanism 46. The slide mechanism 46 moves in a direction (front and rear) perpendicular to the housing 5 (hole wall 21) at the bottom end of the refill case 43 by power from a power source (not shown). The front and rear width of the refill case 43 (the width along the movement direction of the slide mechanism 46) is equal to or greater than the front and rear width of the refill case 43 plus the size of the gap between the front surface of the refill case 43 and the inner surface of the housing 5. Therefore, even when the slide mechanism 46 is advanced until it abuts against the inner surface of the housing 5, the slide mechanism 46 keeps the bottom end of the refill case 43 closed. On the other hand, when the slide mechanism 46 is retracted until the leading end of the slide mechanism 46 is positioned near the rear end of the refill case 43, the bottom end of the refill case 43 opens.

[0028] As shown in FIGS. 6( a) and 6(b), the penetration bodies (penetration needles 41 and penetration rods 42) of this embodiment are held by fasteners 47. Of the multiple penetration rods 42, at least one has a larger diameter than the penetration needles 41. The diameters of the multiple penetration rods 42 may all be the same or different. Of the upper and lower penetration rods 42, 42, the diameter of the upper penetration rod 42 is preferably larger than the diameter of the lower penetration rod 42. Multiple fasteners 47 are stored in a vertically stacked state within the refill case 43. As shown in FIGS. 6( a) and 6(b), the fasteners 47 are stacked vertically within the refill case 43, and the fastener 47 arranged in the uppermost row abuts against the extrusion means 431. When the bottom end of the refill case 43 opens, the pressing force of the extrusion means 431 ejects the fastener 47 arranged in the lowermost row from the refill case 43.

[0029] The penetrating body holding means 44 is provided at a position facing the opening 53 and spaced a predetermined distance from the bottom of the housing 5. As shown in FIGS. 6(a) and 6(b), the penetrating body holding means 44 includes a catcher 441 and a load cell case 442.

[0030] Catcher 441 detachably holds fastener 47 (penetrating body) ejected from refill case 43. Catcher 441 is formed with a bottomed slit 443 that can engage with fastener 47. Fastener 47 is held in catcher 441 by being engaged with slit 443.

[0031] As shown in FIG. 6(b), the catcher 441 is supported by a load cell case 442 fixed to the underside of the slide mechanism 46 and is rotatable around a horizontal axis (an extension of the penetration needle). The catcher 441 protrudes forward beyond the tip of the slide mechanism 46. The catcher 441, together with the slide mechanism 46 and the load cell case 442, advances and retreats toward the hole wall 21 of the measurement hole 2. In other words, the penetration body held by the catcher 441 can advance and retreat in a direction perpendicular to the hole wall 21. As shown in FIG. 1, the penetration body (penetration needle 41 and penetration rod 42) advances via the slide mechanism 46 in a direction perpendicular to the central axis of the housing 5 (i.e., in the radial direction of the measurement hole 2), thereby protruding from the opening 53 toward the hole wall 21.

[0032] The measuring means 45 is a load cell that measures the penetration resistance force when the penetrator held by the catcher 441 penetrates the hole wall 21. As shown in FIG. 6(b), the measuring means 45 is housed in a load cell case 442 behind the catcher 441 (near the penetration needle 41). The measuring means 45 is connected to a determining means (not shown) by wire or wirelessly and transmits the measurement results to the determining means as an electrical signal. The determining means records the measurement results (penetration depth of the penetrator, penetration resistance load, etc.) transmitted from the measuring means 45. The determining means also compares the measured value of the penetration resistance force with a preset threshold value and transmits a signal to the penetrator holding means if the measured value of the penetration resistance force is equal to or less than the threshold value.

[0033] In addition, the housing 5 houses a camera 6, a direction sensor (not shown), and the like. 1, camera 6 captures an image of the penetrating object held by catcher 441. Image data captured by camera 6 is sent to a terminal (for example, a tablet terminal, a smartphone, or a personal computer) at the user's hand.

[0034] The orientation sensor measures the orientation of the housing 5 (penetrator). In this embodiment, the rotating wheel 52 is controlled based on the measurement result of the orientation sensor, thereby rotating the housing 5 around the vertical axis within the measurement hole 2.

[0035] In the penetration test process S2, the housing 5 is inserted into the measurement hole 2 and lowered to a predetermined depth within the measurement hole 2 using the hanging means 54. Once the housing 5 reaches the predetermined depth, the orientation of the housing 5 is adjusted using the rotating wheel 52 so that the penetrator is positioned at an azimuth of 0 degrees. Once the orientation adjustment of the housing 5 is complete, the reaction arm 51 is pressed against the hole wall 21 to fix the housing 5 within the measurement hole 2. When the reaction arm 51 is pressed against the hole wall 21, the side of the housing 5 opposite the reaction arm 51 abuts against the hole wall 21. Once the housing 5 is fixed, the penetrator is protruded toward the hole wall 21 and a penetration test (measurement of the penetration force, penetration amount, etc.) is performed.

[0036] Once the penetration test has been carried out, the determination means is activated and compares the measured value of the penetration resistance force with a preset threshold value. If the measured value of the penetration resistance force is equal to or less than the threshold value, the determination means sends a signal to the penetrator holding means 44. Upon receiving the signal sent from the determination means, the penetrator holding means 44 releases the hold of the penetrator used to measure the penetration resistance force. When the hold of the penetrator is released, the penetrator rod 42 is ejected from the refill case 43 disposed above. The ejected penetrator rod 42 is held by the penetrator holding means 44 (catcher 441). In other words, the penetration test device 4 has a mechanism that replaces the penetrator needle 41 with the penetrator rod 42 when the measured value of the penetration resistance force by the penetrator needle 41 is equal to or less than the threshold value.

[0037] After the penetrator is replaced with the penetrator rod 42, a second penetration test is performed with the penetrator rod 42. The measurement data in the penetration test process S2 is transmitted to a terminal (such as a personal computer, a tablet terminal, or a smartphone) provided outside the measurement hole 2.

[0038] The strength estimation step S3 is a step of determining the estimated strength of the constructed ground improvement body 1a based on the data of the penetration test. In a penetration test, the penetration length L of the penetration needle 41 and the load P at the time of penetration of the penetration needle 41 are measured. Then, to estimate strength, a correlation equation is calculated from the relationship between the penetration gradient Np=P / L, which is the ratio of the load P to the penetration length L, and the unconfined compressive strength qu, and this correlation equation is used to estimate the strength of the object. Even when a penetration rod 42 is used, a correlation equation is calculated (see Figure 7) by linking the penetration gradient Np calculated from the penetration length L and load P at the time of penetration of the penetration rod with the unconfined compressive strength qu, and the strength of the improved ground is estimated. Figure 7 shows a conceptual diagram of the correlation equation.

[0039] The strength comparison step S4 is a step in which the estimated strength is compared with a preset allowable strength for overlap construction. As a result of the comparison, it is confirmed that the allowable strength for overlap construction is not exceeded. In this embodiment, the penetration test step S2, strength estimation step S3, and strength comparison step S4 are repeated for each material age, and the overlap construction date is set based on a strength estimation curve created using the estimated strength for each material age. The allowable strength for overlap construction uses a strength estimated from past construction records.

[0040] According to the penetration test apparatus 4 of this embodiment, if it is determined that the ground to be measured is low in strength and that measurement using the penetration needle 41 is difficult, the penetration test can be performed by replacing the penetration needle 41 with a penetration rod 42 having a larger diameter than the penetration needle 41. In other words, the penetration test apparatus 4 can collect and evaluate measurement data even for low-strength improved ground. Therefore, in ground improvement work that includes overlapping areas, the estimated strength of the completed ground improvement body can be determined early and the condition of the completed ground improvement body can be judged based on this estimated strength, thereby realizing reliable construction and ultimately avoiding poor construction in the overlapping areas and damage to construction machinery.

[0041] Furthermore, the penetration test device 4 can automatically replace the penetration body within the measurement hole 2, eliminating the need to remove the penetration test device 4 from the measurement hole 2, resulting in excellent workability. Furthermore, the refill case 43 stores a number of replacement penetration rods 42 with different cross-sectional areas, making it possible to perform measurements using penetration rods 42 with diameters that correspond to the strength of the improved ground.

[0042] By rotating the penetration test device 4 within the measurement hole 2, multiple penetration tests can be performed at the same depth. Furthermore, by rotating the penetration test device 4 while checking with a direction sensor, the penetration position of the penetrator can be adjusted at a predetermined angle and interval. Therefore, penetration tests of different material ages can be performed using the same measurement hole 2, which is more efficient than conventional measurement methods that required the use of multiple test specimens. Furthermore, using the same measurement hole 2 allows for more accurate verification of material age changes and strength variations. Furthermore, since it is not necessary to create a measurement hole 2 for each specified material age, this method is also more efficient. Furthermore, by rotating the penetration test device 4, measurements can be performed at different circumferential positions around the measurement hole 2 from positions measured at other material ages. Furthermore, even when the specified strength age is reached, in-situ testing can be performed to determine the strength, and quality evaluation can be performed based on test data from before the specified strength age was reached.

[0043] In addition, since the penetration test device 4 can move up and down within the measurement hole 2, it is also possible to carry out penetration tests at different depths. Therefore, it is possible to carry out multiple penetration tests using the same measurement hole 2. Furthermore, since the measurements are performed in situ, the strength of the constructed ground improvement body 1a can be directly grasped.

[0044] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-described components can be appropriately modified within the scope of the present invention. There is no limitation on the configuration of the penetration test device 4. For example, the penetrator may be one that advances and retreats along a guide rail.

[0045] In the above embodiment, a case where multiple penetrating bodies are stored in the refill case 43 is described, but the number of penetrating bodies stored in the refill case 43 is not limited, and may be one. The mechanism for replacing the penetrator is not limited to that shown in the above embodiment.

[0046] In addition, in the above embodiment, the measurement hole 2 is formed using a pipe 3 in the drilling process, but the method of forming the measurement hole 2 is not limited, and for example, the hole may be drilled using an earth drill or the like. In addition, the cement-improved soil 11 inside the pipe 3 that is pulled up together with the pipe 3 during the drilling process may be used as a specimen for a strength test.

[0047] Furthermore, although the housing 5 is configured to rotate around the vertical axis by the rotating wheel 52, an endless strip-shaped member may be used instead of the rotating wheel 52. Furthermore, the number of rotating wheels 52 is not limited, and may be, for example, one or more. The reaction arm 51 does not necessarily have to be rotatable, and may be made of, for example, a cylindrical member and configured to be extendable and contractible. The configuration of the hanging means 54 is not limited, and may be configured appropriately. The penetration test device 4 may be automatically controlled, or may be operated by an operator while checking the data transmitted from the penetration test device 4 and the images captured by the camera 6. [Explanation of symbols]

[0048] 1 Ground improvement body 1a Completed ground improvement body 1b Ground improvement body to be constructed later 11 Cement-improved soil 2 Measuring hole 21 Hole wall 3 Pipe 4 Penetration testing equipment 41 Penetrating Needle (Penetrating Body) 42 Penetration rod (penetration body) 43 Refill Case 44 Penetrator holding means 45 Measurement means 46 Slide mechanism 5. Cabinet 51 Reaction arm 52 Spinning Wheel 53 Opening 54 Hanging means

Claims

1. A penetration test device for performing a penetration test on a hole wall of a measurement hole in the measurement hole, a penetrating body holding means for holding the penetrating body; a slide mechanism that moves the penetrator holding means toward and away from the hole wall of the measurement hole; a measuring means for measuring a penetration resistance force when the penetrator penetrates the hole wall, A penetration test device characterized in that it is provided with a mechanism for replacing the penetration body with a replacement penetration body having a larger diameter than the penetration body when the measured value of the penetration resistance force is below a threshold value.

2. a refill case in which the replacement penetrating body is stored; A determination means for transmitting a signal to the penetrating body holding means when the measured value of the penetration resistance force is equal to or less than a threshold value, The refill case is disposed above the penetrating body holding means when retracted, 2. The penetration test device according to claim 1, wherein the penetration body holding means, upon receiving the signal, releases the holding of the penetration body used to measure the penetration resistance force and holds the replacement penetration body discharged from the refill case.

3. 3. The penetration test device according to claim 2, wherein the refill case contains a plurality of replacement penetration bodies having different cross-sectional areas.

4. The penetration test device according to any one of claims 1 to 3, characterized in that the replacement penetration body is a round bar having a constant diameter in the longitudinal direction or a round bar having a conical tip.

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