JPS6344891B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the tip bearing capacity of a cast-in-place pile produced in an excavated underground hole.

In order to accurately measure the ground bearing capacity of the lower end of a cast-in-place pile, it is of course necessary to eliminate the frictional force of the ground against the surrounding surface of the pile. A steel pipe is embedded, a cast-in-place pile is created inside the steel pipe, and a load is applied to the top end of the pile in the direction of the pile axis to measure the support force at the end of the pile.

According to the above method, since the inner steel pipe circumferential surface is completely separated from the ground, the frictional force on the pile circumferential surface can be reliably cut, and the tip supporting force can be accurately determined.

However, this is an expensive measurement method that requires steel pipes of different diameters.Furthermore, the weld build-up creates resistance, making it impossible to use a welded inner steel pipe. Therefore, it is difficult to measure the bearing capacity of deep ground.

Furthermore, constructing a double structure using long steel pipes that reach the supporting ground is extremely troublesome.

For this reason, in reality, even though it is a double pipe system,
Only the surface layer of the ground is constructed as a double pipe to cut off the circumferential frictional force, and in the lower strata, the bearing capacity is tested by adding up the supporting capacity of the circumferential surface and the tip, and the load is considerably large. was needed.

The present invention has been made in view of these circumstances, and provides an economical and practically useful method that can accurately measure the tip bearing capacity of cast-in-place piles even in deep ground. The purpose is to provide
Accordingly, the method of the present invention involves embedding a steel pipe with a slip material on the inner surface in an excavated underground hole, creating a cast-in-place pile inside the steel pipe, and at the same time, attaching a groove to the upper end of the cast-in-place pile in the direction of the pile axis. It is characterized by applying a load and measuring the support capacity at the end of the pile.

Hereinafter, embodiments of the present invention will be explained based on the drawings. First, as shown in FIG. Form underground hole A.

Next, as shown in FIG.
is buried in the underground hole A.

If the depth of the hole A is deeper than the length of the regular-length steel pipe, the steel pipe 2 may be made by welding regular-length steel pipes to each other on their outer peripheral surfaces, or by using a laminated steel pipe used for joining casings using the Benoto construction method. A bit joint or the like may be used.

Next, as shown in FIG. 3, a reinforcing bar cage 3 is inserted into the steel pipe 2, and a concrete
A cast-in-place pile B is prepared by pouring the molten metal, and after a predetermined curing period, a test load W in the direction of the pile axis is applied to the upper end of the pile to measure the ground bearing capacity at the lower end of the pile.

One means for loading is as follows. That is, as shown in Fig. 4, ready-made reaction piles C made of shaped steel etc. were driven on both sides of the test pile B.
A hydraulic jack E is interposed between the horizontal member D fixed between the upper ends of these reaction piles C and the upper surface of the pile B inside the steel pipe 2.

When a load W is applied by the hydraulic jack E, since the slip material a is attached to the inner peripheral surface of the steel pipe 2, the cast-in-place pile B is in a state of cutting edge with the steel pipe 2, and the cast-in-place pile B The peripheral surface friction force is extremely weak. Therefore, the ground bearing capacity at the lower end of the pile can be measured extremely accurately.

The slip material a may be made of a synthetic resin such as Teflon (trade name), or a combination of a synthetic resin and an asphalt material.

As described above, the present invention uses a slip material attached to the inner circumferential surface of the steel pipe to form a border between the steel pipe and the cast-in-place pile, which is different from the conventional measurement using the double pipe structure. It is not an exaggeration to say that there is no or better than that, it is possible to measure the tip bearing capacity of a pile with such accuracy, and since only one steel pipe is used for measurement, construction is easy and economical. Since it is possible to weld together steel pipes without affecting the structure, the length of the steel pipes can be freely selected, and the bearing capacity of deep ground can therefore be measured. Overall, this is a simple improvement. While
After successfully solving the drawbacks of the conventional method, we were able to accurately measure the bearing capacity at the tip of a pile.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a cross-sectional view showing how an underground hole is excavated, FIG. 2 is a cross-sectional view showing how a steel pipe is buried, and FIG. 3 is a schematic cross-sectional view of a cast-in-place pile. , FIG. 4 is a schematic cross-sectional view illustrating means for applying a load. 2...Steel pipe, a...Slip material, A...Underground hole, B...
Cast-in-place pile, W...Load.

Claims (1)

[Claims] 1. Insert a steel pipe with a slip material on the inner circumferential surface into an excavated underground hole, create a cast-in-place pile inside the steel pipe, and apply a load in the direction of the pile axis to the upper end of the cast-in-place pile, A method for measuring the tip bearing capacity of a cast-in-place pile, the method comprising measuring the tip bearing capacity of the pile.