Dynamic cone penetration test rod and dynamic cone penetration test method using the same

Abstract

To prevent a cone from being left underground, and to concentrate an impact force at a cone tip without deforming or bending a rod.SOLUTION: A rod 10 for dynamic cone penetration test that is used in a test investigating a ground comprises: a tip rod 1 attached to be disposed at a tip of the rod 10 for dynamic cone penetration test; and a cone 6 attached to the tip rod 1. The tip rod 1 includes: a main body 1a having the same diameter φ1 as that of the rod 10 for dynamic cone penetration test; and a stopper portion 1b integrally formed at a tip side of the main body 1a and having a diameter φ2 larger than the diameter φ1 of the main body 1a. The cone 6 has: an upper cone 2 rotatably engaged with the tip rod 1 and fitted to the stopper portion 1b; and a lower cone 3 attached to a lower part of the upper cone 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a dynamic cone penetration test rod used in ground survey tests, and in particular to a dynamic cone penetration test performed so that the cone does not affect the rotation of the rod, for example, a large- or medium-sized dynamic cone penetration test. [Background technology]

[0002] In recent years, large-scale dynamic cone penetration tests, which enable soil investigations with a higher penetration force than Swedish sounding tests, have rapidly become popular as a method of soil investigation for the construction of houses and civil engineering structures.

[0003] In this large-scale dynamic cone penetration test, a rod is extended vertically, a cone is attached to the lower end of the rod, and the rod is continuously penetrated by an automatic continuous penetration device, the rod is rotated every specified distance to measure the torque, and this measurement is used to correct the number of strikes to calculate the Nd value. The Nd value is then used to determine the hardness of the ground, determine the depth distribution, and understand the soil composition of the survey target. There are also self-propelled geological survey machines that fully automate this large-scale dynamic cone penetration test.

[0004] Conventionally, the rods and cones used in large-scale dynamic cone penetration tests, medium-scale dynamic cone penetration tests, etc. are penetrated into the ground with the cone simply fitted onto the rod. Therefore, when the rod is removed after the test, the cone is left in the ground, and many cones that are still usable for each test are left in the ground and discarded.

[0005] To solve this problem, a rod 1 and a cone 6 are disclosed in Patent Document 1 (hereinafter, for the symbols, refer to the drawings in Patent Document 1). In this rod 1 and cone 6, a stopper member 4 is attached to the tip of the rod 1, and an upper cone 2 and a lower cone 3 are attached with the stopper member 4 sandwiched between them, so that the cone 6 is rotatable around the axis of the rod 1 following the up and down movement of the rod 1. Since the cone 6 is provided so as to follow the up and down movement of the rod 1, the cone 6 can be pulled out together with the rod 1 when the rod 1 is pulled out after the test, and the cone 6 can be used any number of times without being left in the ground.

[0006] Incidentally, this rod 1 is made of metal and is long (1000 mm) (see paragraph 0013 of Patent Document 1), and since the rod 1 is long and heavy and very difficult to handle in order to fit the upper cone 2 from the base end side opposite the tip of the rod 1, the stopper member 4 is configured to be detachable from the rod 1 so that the upper cone 2 can be fitted from the tip side of the rod 1. Then, the upper cone 2 is fitted from the tip of the rod 1 from which the stopper member 4 has been removed, and then the stopper member 4 is attached to the rod 1.

[0007] Also, based on the JIS standard for large-scale dynamic cone penetration testing, the diameter of the rod 1 must be 32 mm and the diameter of the cone 6 must be 45 mm (see paragraph 0013 of Patent Document 1). Furthermore, in order to ensure the strength of the stopper member 4, the thickness of the stopper member 4 must be at least a certain value. As a result, it is necessary to provide a step portion 1b on the tip side of the rod 1 to reduce the diameter, and the upper cone 2 is configured to abut against the step portion 1b.

[0008] The rod 1 is then struck by the hammer device 22 to penetrate into the ground, but because the diameter of the tip of the rod 1 is small, the tip of the rod 1 may be deformed or bent by the force of the impact, which may cause the rod 1 to not rotate or come out. As a result, appropriate test results cannot be obtained, and the test must be repeated, and the rod 1 must be replaced more frequently, which reduces the efficiency of the test.

[0009] In addition, when the rod 1 is struck by the hammer device 22, the step portion 1b of the rod 1 hits the upper end of the upper cone 2, so that the striking force is also transmitted to the step portion 1b and is not concentrated at the tip of the cone 6. As a result, the number of strikes required to penetrate the cone 6 to a specified position in the ground is increased, resulting in a problem of a lack of accuracy in the test. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2005-350873 A Summary of the Invention [Problem to be solved by the invention]

[0011] Therefore, the problem that the present invention aims to solve is to provide a dynamic cone penetration test rod that is configured so that the cone is not left in the ground, the rod does not deform or bend, and the impact force can be concentrated at the tip of the cone. [Means for solving the problem]

[0012] In order to solve the above problems, the dynamic cone penetration test rod according to the present invention is a dynamic cone penetration test rod (10) used in a test for investigating ground, and includes a tip rod (1) attached so as to be disposed at the tip of the dynamic cone penetration test rod (10), and a cone (6) attached to the tip rod (1). The tip rod (1) comprises a main body portion (1a) having the same diameter (φ1) as the dynamic cone penetration test rod (10), and a stopper portion (1b) formed integrally with the tip side of the main body portion (1a) and having a diameter (φ2) larger than the diameter (φ1) of the main body portion (1a). The cone (6) comprises an upper cone (2) rotatably fitted into the tip rod (1) and engaged with the stopper portion (1b), and a lower cone (3) attached to the lower portion of the upper cone (2).

[0013] Preferably, the length (L2) of the tip rod (1) is 200 to 300 mm.

[0014] In addition, the dynamic cone penetration test method according to the present invention performs a dynamic cone penetration test using a dynamic cone penetration test rod (10) having the tip rod (1) and the cone (6) described above. Effect of the Invention

[0015] The dynamic cone penetration test rod of the present invention prevents the cone from being left in the ground, prevents the rod from deforming or bending, and concentrates the impact force at the tip of the cone. [Brief description of the drawings]

[0016] [Figure 1] 1A and 1B are cross-sectional views showing the tip rod and the cone, in which FIG. [Diagram 2] FIG. 4 is a perspective view showing a state in which the tip rod and the cone are disassembled. [Diagram 3] FIG. 1 is a side view illustrating the procedure for a large dynamic cone penetration test. [Figure 4]FIG. 11 is a side view illustrating a procedure for pulling out the test rod. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The dynamic cone penetration test rod according to the present invention will be described in detail below with reference to the accompanying drawings.

[0018] Fig. 1 is a cross-sectional view showing the tip rod 1 and the cone 6, (a) showing the disassembled state and (b) showing the assembled state. Fig. 2 is an exploded perspective view showing the tip rod 1 and the cone 6. As will be described later, when performing a large-scale dynamic cone penetration test or the like, a cylindrical dynamic cone penetration test rod 10 is used. The tip rod 1 is attached so as to be disposed at the tip of the dynamic cone penetration test rod 10.

[0019] The tip rod 1 is composed of a cylindrical main body 1a having the same diameter φ1 as the dynamic cone penetration test rod 10, and a cylindrical stopper portion 1b formed integrally with the tip side of the main body 1a. The stopper portion 1b has a diameter φ2 larger than the diameter φ1 of the main body 1a. Therefore, the cross section of the main body 1a of the tip rod 1 is configured to have a continuous circle shape of diameter φ1, the same as the cross section of the dynamic cone penetration test rod 1. The cross section of the stopper portion 1b of the tip rod 1 is configured to have a continuous circle shape of diameter φ2 larger than the diameter φ1 different from the cross section of the main body 1a. The tip rod 1 is made of a metal such as an aluminum alloy or stainless steel, and the main body 1a and the stopper portion 1b are configured to be integral with each other.

[0020] The cone 6 is attached to the tip rod 1. The cone 6 includes an upper cone 2 that is rotatably fitted into the tip rod 1 and engaged with the stopper portion 1b. The cone 6 also includes a lower cone 3 that is attached to the lower part of the upper cone 2. The upper cone 2 and the lower cone 3 are made of metal such as aluminum alloy or stainless steel.

[0021] The upper cone 2 has a through hole 2a into which the tip rod 1 can be inserted, and the upper side 2b is tapered downward. Furthermore, a connecting part 2c is provided at the lower part of the upper cone 2, and a male screw is provided on the outer circumferential surface.

[0022] The lower cone 3 has a sharpened portion 3b at its lower portion, and a recess 3a at its upper portion, which is formed to receive the connecting portion 2c and stopper portion 1b of the upper cone 2. The inner peripheral surface of the recess 3a of the lower cone 3 is provided with a female screw, and the connecting portion 2c of the upper cone 2 and the recess 3a of the lower cone 3 are screwed together with each screw. Therefore, the diameters of the connecting portion 2c of the upper cone 2 and the recess 3a of the lower cone 3 are the same as the diameter φ2 of the stopper portion 1b.

[0023] When assembling the tip rod 1 and the cone 6, first, the upper cone 2 is inserted into the tip rod 1 from the base end side opposite the tip side of the tip rod 1 through the through hole 2a, loosely fitted, and the lower end is abutted against the upper end of the stopper part 1b. Then, the connecting part 2c of the upper cone 2 and the recessed part 3a of the lower cone 3 are screwed together to connect the upper cone 2 and the lower cone 3, forming the cone 6 connected to the rod 1.

[0024] By assembling in this manner, the cone 6 cannot move in the axial direction of the tip rod 1 due to the stopper portion 1b, but is freely rotatable around the axis of the tip rod 1 (see FIG. 1(b)). Note that, since the rod 1 is rotated clockwise in the test, right-handed threads are preferable to prevent loosening of each thread.

[0025] The dimensions of the shape of the tip rod 1, the upper cone 2, and the lower cone 3 are determined by the standard for the large-scale dynamic cone penetration test. Therefore, the outer diameter φ1 of the tip rod 1 is 32 mm, the outer diameter φ3 of the upper cone 2 and the lower cone 3 is 45 mm, the tip angle A of the pointed part 3b of the lower cone 3 is 90 degrees, and the length L1 of the cone 6 formed by integrating the upper cone 2 and the lower cone 3 is 90 mm. The length L2 of the tip rod 1 is 180 mm. A coupling screw 1c is provided at the upper end of the tip rod 1, and a standard type rod is connected to the tip rod 1 by this coupling screw 1c to form a dynamic cone penetration test rod 10. The length of the dynamic cone penetration test rod 10 is 1000 mm. Since the tip rod 1 is made of metal and is heavy, it is desirable that the length L2 of the tip rod 1 is 200 to 300 mm so that the operator can easily hold the tip rod 1 and the cone 6 to attach and remove them.

[0026] Next, we will explain the method of the dynamic cone penetration test (large dynamic cone penetration test) using the tip rod 1 and the cone 6. Figures 3 and 4 are side views for explaining the procedure of the large dynamic cone penetration test.

[0027] In this embodiment, a tip rod 1 having a cone 6 is attached to the tip of a dynamic cone penetration test rod 10. A large dynamic cone penetration test is performed by attaching the dynamic cone penetration test rod 10 having the tip rod 1 to a self-propelled geological survey machine 20. This self-propelled geological survey machine 20 is a survey machine for a large dynamic cone penetration test, and is basically composed of a self-propelled machine 21 capable of self-propelling and a hammer device 22 mounted on this self-propelled machine 21. Furthermore, this self-propelled machine 21 is equipped with a leader 23 for guiding the hammer device 22 and the like to ascend and descend. The hammer device 22 has a built-in ram (not shown) for penetrating the rod and the cone into the ground, and a hydraulic chuck 24 capable of gripping and rotating the rod and moving up and down is provided at the bottom of the leader 23.

[0028] As shown in Fig. 3(a), first, the leader 23 is installed vertically at the survey point, and the hammer device 22 is retracted upward. In this state, a standard type extension rod 11 is connected to the top of the dynamic cone penetration test rod 10, and the top end of this rod 11 is attached to the bottom end of the hammer device 22. At this time, the hydraulic chuck 24 is open, and the lower cone 3 attached to the bottom end of the dynamic cone penetration test rod 10 is grounded on the ground surface. Then, as shown in Fig. 3(b), the ram in the hammer device 22 is repeatedly dropped to penetrate the rods 10 and 11 into the ground, and the number of blows is measured. At this time, the hammer device 22 is configured to descend as the rod penetrates.

[0029] According to the standard for the large-scale dynamic cone penetration test, the ram weighs 63.5 kg and has a drop height of 50 cm. The rod is driven into the cone by free fall, and the number of strikes is counted for every 20 cm of penetration length. After each strike, the rod is gripped and rotated by the hydraulic chuck 24, and the rotational torque of the rod is measured to evaluate the Nd value by correcting the number of strikes (see Equation 1 described later). The torque measurement for peripheral correction is performed every 20 cm if the number of strikes exceeds five, but if it is five or less, the rod is rotated clockwise twice when connected (every 1 m).

[0030] According to the dynamic cone penetration test rod 10 of the present invention, the cone 6 is configured to be rotatable relative to the tip rod 1, and therefore does not affect the rotational torque of the rod. The survey data obtained by the operation of the hammer device 22 and the like is stored in the computer 25 mounted on the self-propelled machine 21 and processed therein.

[0031] Nd=Ndm-Nmantle =Ndm-0.040Mv (Formula 1) Where: Nd: Corrected number of hits (Nd value) Ndm: Number of hits measured Nmantle: Number of impacts equivalent to surface friction Mv: Rotational torque (N m)

[0032] Then, after the hammer device 22 has driven the rods 10 and 11 until it has descended to the lowest end, as shown in Fig. 3(c), the hammer device 22 is lifted upward along the leader 23 and withdrawn, and in this state, another extension rod 11' is added to the coupling screw at the head of the rod 11. Then, the lower end of the hammer device 22 is attached to the upper end of this rod 11', and the above-mentioned operation is repeated to a predetermined depth (for example, 20 to 30 m) to perform the test.

[0033] Next, the operation of pulling out the rod after the test is completed will be described with reference to Fig. 4. As shown in Fig. 4(a), first, the hammer device 22 is retracted to the top of the leader 23 and fixed so as not to fall. In this state, the test rod is gripped by the hydraulic chuck 24. Then, as shown in Fig. 4(b), the hydraulic chuck 24 is moved upward using the drive source (not shown) of the self-propelled machine 21 to pull out the rod penetrated into the ground. Then, the hydraulic chuck 24 and the coupling screw are released, and the extension rods 11, 11'... and the dynamic cone penetration test rod 10 are sequentially removed from the self-propelled geological survey machine 20.

[0034] The cone 6 is connected to the tip rod 1 so that it moves up and down following the up and down movement of the tip rod 1, so that when the dynamic cone penetration test rod 10 is pulled out, the cone can be pulled out together with the rod 1 without being left in the ground as in the conventional method. In addition, a downwardly sloping taper 2b is formed on the upper side of the cone, so that the pulling resistance is small and the cone can be easily pulled out.

[0035] Although the preferred embodiments of the present invention have been described above, the configuration of the present invention is not limited to these embodiments. The stopper portion 1b of the distal end rod 1 may have a diameter larger than that of the main body portion 1a and may be in the shape of a disk with a diamond-shaped cross section, for example, as long as the cone 6 can rotate.

[0036] The effects of the present invention will now be described.

[0037] The dynamic cone penetration test rod 10 according to the present invention is used in a test for investigating ground. The dynamic cone penetration test rod 10 includes a tip rod 1 attached to the tip of the dynamic cone penetration test rod 10, and a cone 6 attached to the tip rod 1. The tip rod 1 includes a main body 1a having the same diameter φ1 as the dynamic cone penetration test rod 10, and a stopper portion 1b formed integrally with the tip side of the main body 1a and having a diameter φ2 larger than the diameter φ1 of the main body 1a. The cone 6 includes an upper cone 2 rotatably fitted into the tip rod 1 and engaged with the stopper portion 1b, and a lower cone 3 attached to the lower portion of the upper cone 2.

[0038] In this tip rod 1 and cone 6, a stopper portion 1b is provided at the tip of tip rod 1 so that the cone 6 can rotate freely around the axis of tip rod 1 in response to the up and down movement of tip rod 1, and an upper cone 2 and a lower cone 3 are attached across the stopper portion 1b. Because the cone 6 is provided so as to follow the up and down movement of tip rod 1, when tip rod 1 is pulled out after testing, the cone 6 can be pulled out together with tip rod 1, and the cone 6 can be used any number of times without being left in the ground. Therefore, since a new cone is not required for each test, the test can be performed economically, and since the cone is not left in the ground, the impact on the environment is small. Furthermore, since the trouble of attaching and detaching the cone is not required, the test time can be shortened.

[0039] Furthermore, the length of the tip rod 1 is shortened and configured to be attached to the dynamic cone penetration test rod 10. This allows the upper cone 2 to be easily fitted from the base end side opposite to the tip of the tip rod 1. Therefore, the stopper portion 1b can be integrally formed at the tip of the tip rod 1, and the diameter φ1 of the main body portion 1a of the tip rod 1 can be made the same as the diameter of the dynamic cone penetration test rod 10. As a result, the tip side of the tip rod 1 does not become small in diameter, so the strength of the tip rod 1 is high, and when the rod 10 is struck by the hammer device 22, the tip rod 1 is not deformed or bent by the impact force, and therefore the tip rod 1 does not rotate or come out. As a result, an appropriate test can be performed, the rod is not replaced frequently, and the accuracy of the test is increased.

[0040] Furthermore, since no step is formed in the tip rod 1, the upper cone 2 does not strike the step of the rod when the rod 1 is struck by the hammer device 22, and as a result, the striking force can be concentrated on the tip of the cone 6. This reduces the number of strikes required to penetrate the cone 6 into the ground at a specified position, shortens the test period, and increases the accuracy of the test.

[0041] Furthermore, since the tip rod 1 is made of metal and is heavy, it is preferable that the length L2 of the tip rod 1 is 200 to 300 mm so that an operator can easily hold the tip rod 1 and the cone 6 and attach and detach them.

[0042] Furthermore, by performing a dynamic cone penetration test using the dynamic cone penetration test rod 1 having the above-mentioned tip rod 1 and cone 6, the cone 6 can be easily attached to the tip rod 1, and by attaching the tip rod 1 with the cone 6 attached to it to the dynamic cone penetration test rod 1, the strength of the entire rod is high and it is not prone to deformation, etc., and the impact force can be concentrated at the tip of the cone 6, thereby improving the accuracy of the test. [Explanation of symbols]

[0043] 1 Tip rod 1a Main body 1b Stopper part 2 Upper cone 3 Lower Cone 6. Cone 10 Dynamic cone penetration test rod

Claims

1. A dynamic cone penetration test rod (10) for use in soil investigation testing, comprising: A tip rod (1) attached to the tip of the dynamic cone penetration test rod (10); A cone (6) attached to the distal end rod (1), The tip rod (1) is A main body portion (1a) having an outer diameter of a first diameter (φ1); a stopper portion (1b) formed integrally with the tip side of the main body portion (1a) and having an outer diameter of a second diameter (φ2) larger than the first diameter (φ1); The cone (6) is An upper cone (2); A lower cone (3), The upper cone (2) has a through hole (2a) having an inner diameter of the first diameter (φ1) and a threaded portion provided around the lower periphery of the upper cone (2), and the outer diameter of the threaded portion is the second diameter (φ2); the lower cone (3) has a recess (3a) having an inner diameter of the second diameter (φ2) for receiving the lower part of the upper cone (2) and the stopper part (1b), and a threaded part is provided on an upper part of the recess (3a); The upper cone (2) and the lower cone (3) are connected to each other by screwing a threaded portion of the upper cone (2) and a threaded portion of the lower cone (3) together, and The dynamic cone penetration test rod (10) does not include a cylinder surrounding the body portion (1a); The upper cone (2) is configured adjacent to and surrounding the main body portion (1a).

2. The dynamic cone penetration test rod according to claim 1, wherein the length (L2) of the tip rod (1) is 200 to 300 mm.

3. A dynamic cone penetration test method, comprising: performing a dynamic cone penetration test using the dynamic cone penetration test rod (10) having the tip rod (1) and the cone (6) according to claim 1 or 2.

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