JP2020190117A - Loading tester - Google Patents

Abstract

To provide a loading tester that has a simple configuration and can improve the accuracy of test results.SOLUTION: A loading tester 1 for obtaining support force properties for a deep ground where the hole bottom of an underground hole 10 is located comprises: a long tubular load transmission member 2 that is inserted into the underground hole 10; a loading plate 3 that is provided on the lower end side of the load transmission member 2 and is positioned on the hole bottom; a stretchable/contractable device 4 that is provided on the upper end side of the load transmission member 2 and applies loads to the load transmission member 2; and a load measurement tool 5 that measures the magnitude of a load applied from the stretchable/contractable device 4 to the loading plate 3 via the load transmission member 2. The load measurement tool 5 is positioned between the loading plate 3 and the lower end of the load transmission member 2. The load measurement tool 5 is detachably joined to the loading plate 3 while the lower surface of the load measurement tool 5 contacts the upper surface of the loading plate 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a loading test device used when determining the bearing capacity characteristics of deep ground.

Conventionally, when determining the bearing capacity characteristics of deep ground, a loading plate is placed at the bottom of the underground hole provided in the survey area, and a load is applied stepwise from the ground, and the magnitude of the load and the amount of subsidence are obtained. A deep load test is being conducted to measure.

For example, in Patent Document 1, a long rod, a loading plate connected to the lower end of the rod, a load cell connected to the upper end of the rod, a hydraulic cylinder connected to the upper part of the load cell, and a hydraulic cylinder connected to the upper part of the load cell are arranged. A loading test device that is integrally formed with a heavy load mounting table is used to apply a load from a hydraulic cylinder to a loading plate placed at the bottom of the hole via a rod, and the magnitude of the load is measured with a load cell. At the same time, a method of measuring the amount of sinking with a displacement meter installed on the rod is disclosed.

Heisei 2-23241

According to Patent Document 1, since the parts constituting the loading test device are integrally formed, it is possible to easily carry out operations such as installation and transportation of the device when carrying out the deep loading test. However, at the test site, it is not possible to appropriately replace the loading plate connected to the rod with another loading plate having a different surface shape in contact with the hole bottom depending on the state of the hole bottom.

In addition, the rod arranged between the load cell and the loading plate may incline and come into contact with the hole wall or the protective pipe as the applied load increases, or may cause problems such as compression bending. Occurs. For this reason, when measuring the load with the load cell connected to the upper end of the rod, it is necessary to estimate in advance the measurement error due to the defect of the rod and correct it, which causes a problem in the accuracy of the measurement result. ..

The present invention has been made in view of such a problem, and a main object thereof is to provide a loading test apparatus capable of improving the accuracy of test results while having a simple structure.

In order to achieve such an object, the loading test device of the present invention is a loading test device for determining the bearing capacity characteristics of the deep ground where the hole bottom of the underground hole is located, and is a long length inserted into the underground hole. A tubular load transmitting member, a loading plate provided on the lower end side of the load transmitting member and arranged at the bottom of the hole, and a loading plate provided on the upper end side of the load transmitting member to apply a load to the load transmitting member. The expansion / contraction device and the load measuring tool for measuring the magnitude of the load applied to the load plate described above from the expansion / contraction device via the load transmission member are provided, and the load measuring tool includes the load plate described above and the load. It is characterized in that it is arranged between the lower end portion of the transmission member and is detachably joined to the loading plate in a state where the lower surface is in surface contact with the upper surface of the loading plate described above.

Further, the loading test apparatus of the present invention includes a plurality of pre-described mounting plates having different shapes of contact surfaces that abut on the hole bottom, and any one of the plurality of mounting plates is the load measuring tool. The feature is that they are detachably joined to each other.

Further, the loading test apparatus of the present invention is characterized in that the previously described loading plate is provided with a plurality of vertical grooves extending from the lower surface to the upper surface of the loading plate on the side peripheral surface.

According to the load test apparatus of the present invention, the load measuring tool is arranged between the load plate and the lower end portion of the load transmission member, and is brought into surface contact with the load plate. It is possible to directly measure the load applied to the loading plate via. Therefore, even if a defect such as bending occurs in the load transmitting member due to the compressive force applied by the expansion / contraction device, it is possible to obtain the measurement result with high accuracy without being affected by these defects. Become.

Further, since a plurality of loading plates having different shapes of contact surfaces that come into contact with the hole bottom are provided and the loading plates are detachably joined to the load measuring tool, the loading plates can be easily replaced at the test site. Work can be carried out. As a result, even when the hole bottom is disturbed or slime is settled, the test can be performed using a loading plate having a contact surface having a shape suitable for the current situation. It is possible to increase the reliability.

Further, since a plurality of vertical grooves are provided on the side peripheral surface of the loading plate, when the loading test device is inserted into the underground hole, slime is settled on the bottom of the underground hole. However, the slime can escape through the flutes so that the contact surface can be surely brought into close contact with the bottom of the underground hole, and a highly reliable test result can be obtained.

According to the present invention, the load measuring tool is arranged between the lower end of the load transmitting member and the loading plate, and the accuracy of the measurement result is improved by a simple configuration in which the load measuring tool and the loading plate are brought into surface contact with each other. Along with this, it becomes possible to obtain the bearing capacity characteristics of the ground on which the hole bottom is located with high accuracy.

It is a figure which shows the loading test apparatus in this embodiment. It is a figure which shows the detail of the loading test apparatus in this embodiment. It is a figure which shows the example of the loading plate which the shape of the contact surface is different in this embodiment. It is a figure which shows the state in which the loading plate which provided the vertical groove on the side peripheral surface in this embodiment was inserted into the underground hole.

The loading test device is used for a deep loading test, and in the present embodiment, a case where a deep loading test using the loading test device is performed using a boring hole provided in the ground is given as an example. , Explain the details.

In the deep loading test, a loading plate is installed at the bottom of the boring hole excavated to carry out the boring survey and at the bottom of the excavation groove formed to construct a continuous underground wall, and the loading plate is used. A load is applied stepwise from the above-ground part, the magnitude of the load and the amount of subsidence are measured, and the bearing capacity characteristics related to the ground at the bottom of the hole are obtained based on these measured values.

As shown in FIG. 1, the load test device 1 is provided with a load transmission member 2 inserted inward of a protective tube 12 previously inserted into the underground hole 10 and a load transmission member 2 on the lower end side of the load transmission member 2. A load measuring tool 5 that measures the magnitude of the load applied to the loading plate 3 via the loading plate 3, the telescopic device 4 provided on the upper end side of the load transmitting member 2, and the load transmitting member 2 from the telescopic device 4. And have.

The load transmitting member 2 is composed of a hollow pipe having a member length that reaches the bottom of the underground hole 10 from the ground, and is arranged at the uppermost portion with the plurality of hollow pipe members 21 as shown in FIG. It is configured by connecting the load receiver 22 in the length direction, and a load measuring tool 5 is installed at the lower end of the load transmitting member 2 so as to close the opening.

The load measuring tool 5 includes a hollow tubular strain-causing body 53 provided with an upper lid 51 and a bottom plate 52, and a strain gauge 54 installed on the inner peripheral surface of the strain-causing body 53. The load of the acting compressive force is sensed by the strain gauge 54 and converted into an electric signal. Therefore, the electric cable 55 connected to the strain gauge is connected to a measuring instrument (not shown) arranged on the ground by using the hollow portion of the load transmission member 2.

Further, the bottom plate 52 of the strain generating body 53 has a smooth lower surface, a recess formed inward of the strain generating body 53 at the center thereof, and a female screw 56 on the inner peripheral surface of the recess. It is formed.

The loading plate 3 is formed in a solid cylindrical body, has a contact surface 31 that abuts on the bottom of the underground hole 10 on the lower surface, and hits the bottom plate 52 of the load measuring tool 5 on the upper surface 32. A tangent smooth surface is formed. Further, a male screw 33 screwed into a female screw 56 provided on the bottom plate 52 of the load measuring tool 5 is provided at the center of the upper surface 32, and is detachable from the load measuring tool 5. Then, when the male screw 33 is screwed into the female screw 56 until the loading plate 3 abuts on the load measuring tool 5, the upper surface 32 of the loading plate 3 and the lower surface of the bottom plate 52 of the load measuring tool 5 are in surface contact with each other. It becomes.

The shape of the loading plate 3 may be any shape as long as it has the above function, but in the present embodiment, the contact surface 31 is formed as a conical surface having an apex angle of 120 ° C. as shown in FIG. In addition, the loading plate 3 having the shape shown in FIGS. 3A and 3B is provided. Specifically, in the loading plate 3 of FIG. 3A, the contact surface 31 is formed flat, and the diameter L of the columnar portion is larger than the diameter of the pipe of the load transmitting member 2. In the loading plate 3 of FIG. 3B, the contact surface 31 is formed on a conical surface having an apex angle of 150 ° C.

All of these are provided with a male screw 33 that can be screwed into the female screw 56 provided on the bottom plate 52 of the load measuring tool 5 on the upper surface 32, and can be replaced with respect to the load measuring tool 5 in the ground. It can be appropriately used depending on the state of the bottom of the hole 10. In particular, as shown in FIG. 3A, a loading plate 3 having a large contact surface 31 that abuts on the bottom of the underground hole 10 is provided on the loading test device 1 by increasing the diameter L of the cylindrical portion. When used, it is possible to improve the accuracy of the test result according to the expansion of the area.

Further, as shown in FIG. 4, when the diameter L of the columnar portion of the loading plate 3 is increased to the maximum, that is, to a diameter substantially smaller than the inner diameter of the protective tube 12 (to the extent that it does not contact the inner peripheral surface of the protective tube 12). It is preferable to provide a plurality of vertical grooves 34 extending from the contact surface 31 toward the upper surface 32 on the side peripheral surface thereof. That is, when the diameter L of the columnar portion is increased to about a diameter smaller than the inner diameter of the protective tube 12, the gap between the side peripheral surface of the loading plate 3 and the hole wall of the underground hole 10 becomes narrower, so that the loading plate 3 is hit. When the contact surface 31 is arranged at the bottom of the hole, it is not possible to secure ten spaces for the slime 11 to escape. Then, the slime 11 may be left between the contact surface 31 of the loading plate 3 and the bottom of the hole.

However, by providing the vertical groove 34 on the side peripheral surface, the slime 11 is loaded on the loading plate 3 by utilizing the space where the gap between the hole wall of the underground hole 10 and the loading plate 3 and the vertical groove 34 are added. It can escape outward from between the contact surface 31 and the bottom of the hole. As a result, even when the diameter L of the columnar portion of the loading plate 3 is increased to about a diameter smaller than the inner diameter of the protective tube 12, the contact surface 31 can be brought into close contact with the bottom of the underground hole 10 and tested. It is possible to further improve the accuracy of the result.

As shown in FIG. 1, the expansion / contraction device 4 applies a load to the load plate 3 via the load transmission member 2, and if a sufficient stroke is secured for applying the load, a hydraulic jack or a manual type Any of the jacks and the like may be adopted, and the load transmitting member 2 is mounted on the load receiving portion 22 located at the uppermost portion.

Further, as shown in FIG. 1, the loading test device 1 includes a reaction force receiving device 6 that functions as a reaction force receiving when the telescopic device 4 is extended, and a sinking amount when a load is applied to the loading plate 3. A subsidence amount measuring device 7 for measuring is provided. The reaction force receiving device 6 is composed of a weight 61 arranged above the telescopic device 4 and a gantry 62 on which the weight 61 is placed, and the telescopic device 4 directly or indirectly hits the lower surface side of the gantry 62. Be touched.

On the other hand, the settlement amount measuring device 7 includes a measuring rod 71 housed inside the load transmitting member 2, an immovable beam 73 arranged on the ground, and a displacement meter 74.

The measuring rod 71 has a member length that allows the upper end to reach the ground in a state where the lower end is in contact with the upper lid 51 of the load measuring tool 5, and as shown in FIG. 2, a plurality of rod-shaped members 711. Is configured by connecting in the length direction. Further, the cross-sectional diameter of the measuring rod 71 is formed so as not to come into contact with the inner peripheral surface of the load transmitting member 2, and an arm member 72 orthogonal to the measuring rod 71 is installed at the upper end.

The arm member 72 is provided so as to project horizontally to the outside of the load transmission member 2 through an elongated hole in the axial direction provided in the load transmission member 2, and above the arm member 72, as shown in FIG. The immovable beam 73 is arranged. The immovable beam 73 is a cantilever beam installed on a support plate 8 mounted on the ground surface via a non-land adjusting member 9 via a support column, and is a displacement meter 74 between the immovable beam 73 and the arm member 72. Is installed.

As the support plate 8 and the non-landing adjusting member 9, any of them may be adopted as long as the immovable beam 73 can be held horizontally.

As shown in FIG. 1, the displacement meter 74 measures the displacement of the distance between the immovable beam 73 and the arm member 72 of the measuring rod 71 as a sinking amount, and is an electric type or a dial gauge type. Any displacement meter may be used.

The deep load test using the load test device 1 having the above configuration is carried out by the following procedure.

First, the underground hole 10 is drilled and the protective pipe 12 is arranged to remove the slime 11 at the bottom of the hole. Further, the support plate 8 is installed on the ground surface via the non-land adjustment member 9, and the load transmission member 2 provided with the load plate 3 on the lower end side via the load measuring tool 5 is inserted into the underground hole 10. Then, the contact surface 31 of the loading plate 3 is brought into contact with the bottom of the hole. At the same time as or before and after these operations, the reaction force receiving device 6 is installed on the ground surface.

The load transmitting member 2 houses the measuring rod 71 in advance, and the inclination angle is adjusted so that both the load transmitting member 2 and the measuring rod 71 are vertically built in the underground hole 10. To do.

After that, the expansion / contraction device 4 is installed between the load transmitting member 2 and the gantry 62 constituting the reaction force receiving device 6, and the immovable beam 73 provided on the support plate 8 and the arm provided on the measuring rod 71. A displacement meter 74 is installed between the member 72 and the deep load test is started.

In the loading test, the expansion / contraction device 4 is extended stepwise to apply a load stepwise to the loading plate 3 via the load transmitting member 2, and the sinking amount of the loading plate 3 is intermittently measured by the displacement meter 74. To do. Then, when the amount of subsidence begins to increase significantly, the extension work of the expansion / contraction device 4 is interrupted, and the load at that time is sensed by the strain gauge 54 of the load measuring tool 5 and converted into an electric signal. The electrical signal is transmitted via the electrical cable 55 and can be read by a ground measuring instrument (not shown).

At this time, since the load measuring tool 5 is arranged between the lower end portion of the load transmitting member 2 and the loading plate 3, the load applied to the loading plate 3 is directly measured by the load measuring tool 5. Can be done. Therefore, even when the expansion / contraction device 4 is extended and a compressive force is applied to the load transmission member 2, the load transmission member 2 is tilted and comes into contact with the protective tube 12 or is bent. , The values measured by the load measuring tool 5 and the displacement meter 74 are not affected by these.

Further, since the lower surface of the bottom plate 52 of the load measuring tool 5 and the upper surface 32 of the loading plate 3 are brought into surface contact with each other, the load is smoothly transmitted between the load measuring tool 5 and the loading plate 3. Therefore, it becomes possible to measure the load and the amount of subsidence with higher accuracy, and accordingly, the ground to which the loading plate 3 is in contact, that is, the hole of the underground hole 10, which is obtained based on the read load and the amount of subsidence, is obtained. The bearing capacity characteristics of the ground on which the bottom is located can also be obtained with high accuracy.

By the way, as described above, the loading test device 1 includes three loading plates 3 having different shapes. Therefore, for example, if it is presumed that the hole bottom of the underground hole 10 is disturbed or the slime 11 is settled during the test, the contact having a shape suitable for the current situation is appropriately applied at the construction site. The loading plate 3 having the surface 31 can be selected and replaced and the test can be re-executed using it. In this way, it becomes possible to further improve the reliability of the measurement result.

The loading test apparatus of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the present embodiment, a case where a deep load test is performed by using a boring hole as an underground hole 10 has been given as an example, but the present invention is not limited to this, and is for constructing an underground continuous wall. It is possible to use the underground hole 10 formed in any of the excavation ditches and the like.

Further, as the protective pipe 12, a casing pipe that protects the hole wall of the underground hole 10 as shown in FIG. 1 was adopted, and this was also used to protect the load transmission member 2. However, the protective pipe 12 is used for load transmission. Any member may be used as long as it has an inner diameter that does not come into contact with the member 2 and can protect the load transmitting member 2.

Further, in the present embodiment, three types of replaceable loading plates 3 provided in the loading test device 1 are illustrated, but the quantity and shape thereof are not limited to these, and the vertical groove 34 is a loading plate. It may be provided regardless of the size of the diameter L in the columnar portion of 3.

1 Load test device 2 Load transmission member 21 Hollow tube member 22 Load receiver 3 Load plate 31 Contact surface 32 Top surface 33 Male screw 34 Vertical groove 4 Telescopic device 5 Load measuring tool 51 Top lid 52 Bottom plate 53 Strain gauge 54 Strain gauge 55 Electric cable 56 Female screw 6 Reaction force receiving device 61 Weight 62 Stand 7 Sinking amount measuring device 71 Measuring rod 72 Arm member 73 Immovable beam 74 Displacement gauge 8 Support plate 81 Handle member 82 Notch 9 Landing adjustment member 10 Ground Inner hole 11 Slime 12 Protective tube 13 Male screw side 14 Female screw side

Claims (3)

It is a loading test device for determining the bearing capacity characteristics of the deep ground where the bottom of the underground hole is located.
A long tubular load transmitting member inserted into the underground hole and
A load plate provided on the lower end side of the load transmitting member and arranged at the bottom of the hole,
An expansion / contraction device provided on the upper end side of the load transmitting member and applying a load to the load transmitting member,
A load measuring tool for measuring the magnitude of the load applied to the load plate described above from the telescopic device via the load transmitting member is provided.
The load measuring tool is arranged between the load plate described above and the lower end portion of the load transmitting member, and is detachably joined to the load plate with the lower surface in surface contact with the upper surface of the load plate described above. A loading test device characterized by this. In the loading test apparatus according to claim 1,
A plurality of the above-mentioned mounting plates having different shapes of contact surfaces that come into contact with the hole bottom are provided.
A loading test apparatus characterized in that any one of the plurality of mounting plates is detachably joined to the load measuring tool. In the loading test apparatus according to claim 1 or 2.
A loading test apparatus, wherein the above-mentioned loading plate is provided with a plurality of vertical grooves extending from the lower surface to the upper surface of the loading plate on the side peripheral surface.