JP4098191B2 - Pile rapid loading test equipment - Google Patents

Description

The present invention relates to a rapid loading test apparatus for piles for investigating the settlement rigidity and supporting force of the piles placed.

A method well known and practiced as a pile loading test is a static loading test. According to this method, it is possible to obtain highly reliable data on the settlement rigidity and supporting force of the piles that have been laid, but there is also a disadvantage that a large loading device is required and the test takes time.
On the other hand, the dynamic loading test is a method that compensates for the shortcomings of the static loading test because the loading device is simple and the loading time is as short as 5 to 30 ms. Because it includes dynamic effects, it is hard to say that reliable data is always obtained.

Therefore, a rapid loading test was newly devised. According to this method, the loading time is set to about 50 to 200 ms, which is about 10 times that of the dynamic loading test, thereby eliminating the influence of propagation of elastic waves, and static loading test. A highly reliable test result close to the loading test can be obtained.
As a method for the rapid loading test, a test method called a static test and a pseudo static test is generally known. In the stunamic test, a reaction mass is launched by burning propellant, and a load is loaded on the pile head by the reaction force generated at that time. The pseudo static test is a method in which a hammer is dropped from above and loaded with a steel coil spring or a disc spring or the like installed on the pile head.
Furthermore, the inventors of the present application have developed and implemented a rapid loading test apparatus for piles using a polymer compound such as urethane elastomer as a cushioning material (see Patent Document 1).
JP 2002-303570 A

The conventional rapid loading test apparatus for piles has the following problems.
<1> In the method of installing a steel spring on the pile head, since the mass of the spring itself is increased, the force acting on the pile at the time of hitting is reduced. Therefore, the mass of the weight used for loading must be increased, and the shape and mass of the entire apparatus become large. In addition, when a steel spring is used, since material attenuation is small, a high-frequency weighting component that causes a decrease in test accuracy is generated.
<2> It is difficult to change the spring constant and length of the steel spring in order to set the maximum load and the loading time that meet the target of the rapid loading test.
<3> A stanamic test using jet fuel and a buffer material made of a polymer compound have a high material cost, so the test cost tends to be expensive.

In order to solve the above-described problems, a rapid loading test apparatus for a pile according to the present invention is an apparatus used for a rapid loading test of a pile that is performed by hitting a pile head with a weight. A cushioning material interposed between the weight and the pile head, wherein the cushioning material is formed in an outer shell shape having a hollow portion by an elastic material. Here, the hollow portion is preferably opened.
Further, in the above rapid loading test apparatus for piles, a donut-shaped rubber tire can be used as the cushioning material.
Furthermore, in the rapid loading test apparatus for a pile described above, a plurality of the cushioning materials can be stacked according to the weight of the weight. In addition, an annular member may be used for the cushioning material, and the cushioning material having an outer shape smaller than the inner shape of the cushioning material may be disposed inside.

The rapid loading test apparatus for piles according to the present invention can obtain at least one of the following effects by means for solving the above-described problems.
<1> The structure of the test apparatus is a simple structure, and the test method is only to hit the pile head with a weight via a cushioning material. For this reason, it can be implemented easily.
<2> Since old tires and the like can be used as a cushioning material, the material cost is very low. In addition, it is possible to actively utilize old tires for which disposal becomes a problem.
<3> Since the cushioning material has a hollow portion, it is lightweight, and the mass of the weight can be efficiently loaded as a load. As a result, the test apparatus can be made small, and the transportation cost and installation cost of the apparatus can be reduced, which is economical. In addition, the test can be performed in a narrow place.
<4> The loading time and the maximum load can be easily adjusted by stacking or using a plurality of cushioning materials.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1> Pile rapid loading test apparatus The rapid loading test apparatus 1 is an apparatus for performing a rapid loading test of a pile, and a weight 3 for applying a load, a pile head 4 and a weight 3 of a pile to be tested. Cushioning material 2 interposed between the two. Here, the weight 3 is moved up and down by a base machine 5 or a crane .

<2> Buffer Material The buffer material 2 is used to extend the loading time due to the impact of the weight 3. The shock-absorbing material 2 of the present invention is a member formed in an outer shell shape having a hollow portion by an elastic material. As the elastic material, rubber such as synthetic rubber and natural rubber, an elastic material having a laminated structure constituting a rubber tire, a known synthetic resin material having elastic performance, and the like can be used.
Further, since the cushioning material 2 has a hollow structure having the hollow portion 21, the weight is light and most of the impact force by the weight 3 can be applied to the pile head 4.

Moreover, it is preferable that the hollow portion 21 of the cushioning material 2 has a structure connected to the opening 22. By providing the opening 22, the force transmitted from the weight 3 to the outer shell of the cushioning material 2 is transmitted to the gas in the hollow portion 21, and the gas compressed by the force is discharged from the opening 22. When there is no opening 22, since the compressed gas becomes resistance, the function as a cushioning material for extending the loading time is reduced. That is, by providing the opening 22, a member having a large material attenuation can be configured. For example, since a steel spring that has been used conventionally has a small material damping, a high-frequency weighting component is generated when it is hit with the weight 3, which causes a decrease in test accuracy.
Therefore, it is preferable to use the buffer material 2 having a structure with a large material attenuation so as to suppress the generation of a high-frequency weighted component and obtain a highly accurate test result.

<3> Weight The weight 3 is a weight that strikes the pile head 4 to be loaded on the pile. The weight 3 is formed using a material having a large specific gravity such as a steel material.
When hitting the pile head 4 with the weight 3, the weight 3 is usually lifted by the base machine 5 or a crane and then dropped freely. It is also possible to hit the pile head 4 by connecting the weight 3 to the base machine 5 having a vertical drive device.

<4> Principle A force is applied to the pile head 4 via the cushioning material 2 by dropping the weight 3. When the weight 3 is dropped from the height H, the spring element of the cushioning material 2 is compressed and the material damping acts as a damper, so that the weight 3 is dropped directly on the pile head 4 compared to the case where the weight 3 is dropped directly on the pile head 4. It is possible to extend the loading time by 10 times or more. The acting force is transmitted as a loaded load to the pile via the cushioning material 2.

<1> Rubber Tire The cushioning material 2 of the present invention is not limited in shape and structure as long as it is formed in an outer shell shape having a hollow portion by an elastic material. For example, a rubber tire is used as the cushioning material 2. be able to.
The rubber tire has a hollow portion 21 inside an outer shell made of a laminated structure material, and a surface in contact with the inner wheel is an opening 22 (see FIG. 2). That is, the opening 22 is annularly formed inside.
Even if it is a used rubber tire, the role as the cushioning material 2 of the present invention can be sufficiently exerted. Rubber tires 2a is to use stacked plurality in accordance with the weight of the weight 3 (see FIG. 3).
Alternatively, a small-diameter tire 2c having an outer diameter smaller than the inner diameter of the large-diameter tire 2b can be fitted into the large-diameter tire 2b to form a cushioning material 2 having a multiple structure (see FIG. 4). The cushioning material of multiple structure (2b, 2c) to use multiple stacked in the.

<2> Method of Rapid Loading Test of Pile The cushioning material 2 is installed on the pile head 4. The cushioning material 2 is installed on the base 41 attached to the pile head 4. The number of buffer materials 2 stacked and whether or not to have a multiple structure can be adjusted according to the test conditions. Here, it adjusts according to the maximum load and loading time which are the targets of the rapid loading test .
The weight 3 is arranged so that the weight 3 attached to the base machine 5 is positioned directly above the cushioning material 2 installed on the pile head 4. The weight 3 can be changed in weight and drop height depending on test conditions.

Hereinafter, the results of tests using the rapid loading test apparatus of the present invention will be described.
In the test, the load P acting on the pile when the weight 3 was dropped on the pile head 4 via the cushioning material 2 and the subsidence amount S with respect to the load P were measured with time t, and the bearing capacity of the pile was verified.
FIG. 5 shows the relationship between the loading time t and the loading load P, and FIG. 6 shows the test results representing the relationship between the loading time t and the pile head settlement S. From this result, it can be said that by using the cushioning material 2, it was possible to obtain a loading time of a rapid loading test with a loading time of about 0.05 to 0.20 sec (50 to 200 ms).
Moreover, when the relationship between the load P and the settlement amount S is expressed from the test result, a curve similar to the result of the static load test as shown in FIG. 7 can be drawn. For this reason, the bearing capacity characteristic of a pile can be verified easily.

The perspective view of the Example of the rapid loading test apparatus of the pile of this invention. The perspective view which showed the cut | disconnection cross section of the Example of a shock absorbing material. Explanatory drawing of the Example of the rapid loading test apparatus which piled up the buffer material. Explanatory drawing of the Example of the buffer material of a multiple structure. The relationship diagram of loading time and loading load. The relationship diagram of loading time and the amount of settlement of a pile head. The relationship figure of a load load and the amount of settlement of a pile head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rapid loading test apparatus 2 ... Buffer material 2a ... Rubber tire 2b ... Large diameter tire 2c ... Small diameter tire 21 ... Hollow part 22 ... Opening 3 ... Weight 4 ... Pile Head

Claims (5)

A device used for a rapid loading test of a pile that is performed by hitting a pile head with a weight,
A weight,
A donut-shaped rubber tire interposed between the weight and the pile head,
A rapid loading test apparatus for piles, wherein a plurality of the rubber tires are stacked according to the weight of the weight . In the pile rapid loading test apparatus of Claim 1,
The rapid loading test apparatus for piles, wherein the rubber tire is formed in an outer shell shape having a hollow portion by an elastic material . In the rapid loading test apparatus of the pile according to claim 1 or 2,
The rapid loading test apparatus for piles, wherein the hollow portion is opened . In the pile rapid loading test apparatus of Claim 3 ,
The rapid loading test apparatus for piles, wherein the opening is formed in an annular shape inside the hollow portion . In the pile rapid loading test apparatus as described in any one of Claims 1 thru | or 4,
A rapid loading test apparatus for piles, wherein a rubber tire having an outer shape smaller than an inner shape of the rubber tire is disposed inside.

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