JPS6144166B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a pile loading test method in which a pile driven into the ground is loaded using a loading tester and the bearing capacity of each pile is measured.

In the conventional pile loading test method, a test pile is first driven into the ground, a load testing machine is placed above it to measure loads, etc., and a load is applied to the head of the pile.
By measuring the load, the bearing capacity of each pile is measured.

Therefore, the supporting force of a pile driven into the ground, that is, the ratio of the tip supporting force and the circumferential surface friction force, may be completely contradictory depending on the geology or the depth of the driven pile. In other words, in some locations, the peripheral surface friction force may be greater than the pile tip bearing capacity, and in other locations, the pile tip bearing capacity may be greater, so it is important to easily and accurately know the ratio of the two. It is.

However, in this method, the measured bearing capacity of a pile is the sum of the pile's tip bearing capacity and its circumferential surface friction force, and the ratio of the pile's tip bearing capacity to its circumferential surface friction force is completely unknown. .

Furthermore, when a pile is driven across two layers, for example, a diluvial layer and an alluvial layer, it is completely impossible to know the ratio of the pile's bearing capacity due to the diluvial layer to the pile bearing capacity due to the alluvial layer. .

In this way, in the conventional pile loading test method, the ratio of the pile tip bearing capacity to the bearing capacity due to circumferential friction,
When a pile is driven between two layers, it is impossible to easily measure the pile bearing capacity of each layer, and it is extremely difficult to accurately determine the mechanical properties of the geology.

Furthermore, if it is attempted to measure the ratio of the supporting force at the tip to the supporting force due to circumferential friction, a separate large-scale test work is required, which has the drawback of causing a significant increase in testing costs.

The present invention was devised in order to solve the above-mentioned problems, and involves driving a pile in the ground, in which the tip and main body are connected in a separable manner, and using a loading tester to determine whether the tip of the pile and the body are separated. By loading the main body of the pile separately and measuring the support force at the end of the pile and the friction force on the circumferential surface separately, it is possible to obtain more accurate geological mechanical properties easily and inexpensively. The purpose is to provide a test method that enables measurement.

Embodiments of the present invention will be described in detail below with reference to the drawings.

The pile 1 used in the present invention is made of concrete and is divided into two parts at an appropriate point in the longitudinal direction, that is, near the tip in this embodiment, into a tip 2 and a main body 3.

Specifically, the pile 1 includes a hollow cylindrical body part 3 having an appropriate length as shown in FIG. 1, and a conical tip part 2 attached in a straight line to one end of the main body part 3. , the main body part 3 and the tip part 2
A connecting device 4 is interposed between the body portion 3 and the distal end portion 2 to freely connect the body portion 3 and the distal end portion 2.

The connecting device 4 has a bottom wall 5 having a through hole 5a.
a cylindrical support tube 5 having a support tube 5; 7 and a connecting bolt 8 that is screwed together. A receiving part 9 is fixed to the connecting bolt 8, and a pin 10 is attached at a certain distance from the receiving part 9, and a locking plate 11 can be slid between the receiving part 9 and the pin 10. It is supported by inserting it into. Further, one end of the support cylinder 5, that is, the end opposite to the end provided with the bottom wall 5b, is fixed to one end 3b of the main body part 3 by welding 12. Note that 27 is a rubber gasket attached to the bottom wall 5b of the support tube 5.

When the connecting bolt 8 housed inside the support tube 5 is screwed into the threaded portion 7a of the receiver 7, the front end portion 2 comes into contact with the bottom wall 5b of the support tube 5 due to the tightening force of the bolt 8. That is, the tip portion 2 is connected to the pile main body portion 3 via the connecting device 4 (see FIG. 1).

Next, the load tester 13 that loads the pile 1 and measures the bearing capacity of the pile 1 will be explained.

As shown in FIG. 4, the loading tester 13 includes a loading oil jack 14, a contact plate 15 attached to the tip of the ram of the oil jack 14, an elastic ring type load meter 16, and a bottom end of the oil jack 14. At the same time, a load transfer tube 18 with a loading plate 17 fixed to the lowermost end thereof, and a head 19a inside the load transfer tube 18 penetrates through a slit 18a formed in the transfer tube 18 and protrudes outside the tube 18. It consists of a loosely fitted T-shaped settlement measuring tube 19. A dial gauge 20 for load measurement is arranged inside the ring of the elastic ring type load cell 16, and a reference beam 2 is fixed at an appropriate location so as to maintain a certain distance from the ground.
1 and 22 are provided between the head 19a of the settlement measuring tube 19 and the reference beam 21 and between the oil jack 14 and the reference beam 22, respectively, for measuring the amount of ground settlement and the amount of compression of the load transmission tube. 24 are installed.

In addition, in the above-mentioned example, the loading tester 13 that can measure the load and the amount of ground subsidence was used.
The present invention is not limited to this, but any type of load testing machine may be used as long as it can apply a load to a pile driven into the ground and measure the load.

Pile 1 and loading test machine 13 configured as above
To carry out the present invention using a pile driver, first, a pile 1 is driven into the ground A using a pile driver or the like (see FIG. 1). Thereafter, the bolt 8 of the connecting device 4 connecting the main body 3 and the tip 2 of the pile 1 is pulled out by the bolt pulling device 25 (details thereof are omitted) while rotating (as shown by the imaginary line in FIG. 1). Main body part 3 of pile 1
and the distal end 2 are disconnected.

Next, a loading test is performed on the tip portion 2 of the pile. That is, as shown in FIG. 4, a loading tester 13 is interposed between the support part 26 located a certain distance from the ground and the tip end part 2 of the pile. At this time, the readings of the dial gauges 20, 23, and 24 are adjusted to 0.

Then, push out the ram of the loading oil jack 14 and push up the support part 26 with the contact plate 15.
When the reaction force is applied to the tip 2 of the pile via the load transmission pipe 18 and the loading plate 17, only the tip 2 sinks (see FIG. 2). At this time, the load caused by the oil jack 14 and the amount of ground subsidence are measured from the dial gauges 20 and 23.

In this manner, a loading test is performed on the pile tip 2 to measure the supporting force of the pile tip 2.

After the loading test of the pile tip 2 is completed, the circumferential friction force of the pile 1 is next measured.

First, the loading tester 13 is interposed between the main body 3 and the support 26 of the pile 1.

Specifically, the loading plate 17 fixed to the tip of the transmission tube 18 of the testing machine 13 is attached to the head 3a of the main body 3, and
The contact plates 15 attached to the elastic ring type load cell 16 are brought into contact with the supporting parts 26 (not shown).

Next, the ram of the oil jack 14 is pushed out and the support part 26 is pushed up by the contact plate 15, and the reaction force is transferred to the main body part 3 through the transmission pipe 18 and the loading plate 17.
When a load is placed on the head 3a of the main body 3, the main body 3 sinks.
At this time, the load caused by the oil jack 14 and the amount of ground subsidence are measured from the dial gauges 20 and 23. In this way, the peripheral surface friction force of the pile main body 3 is measured.

When a loading test is performed using the pile 1 which is divided into two parts near the tip of the pile 1 in this way, the tip support force and the circumferential surface friction force of the pile 1 can be measured separately.

In the above example, the loading test was conducted using the pile 1 that was divided into two near the tip of the pile, but the present invention is not limited to this. Loading tests may be conducted using piles (not shown).

Furthermore, the pile, which can be divided into two, is placed underground so that it spans two layers, for example, a diluvial layer and an alluvial layer, and the connection point between the tip and the main body is located at the interface between the diluvial layer and the alluvial layer. The bearing capacity of the diluvial layer and the bearing capacity of the alluvial layer can be reliably measured by placing the load on the tip and then measuring the load using a load testing machine. be able to.

In the present invention, as described above, a pile is divided into two parts, the tip part and the main body part, and the tip part and the main part are configured to be freely connectable, and the pile is driven into the ground. Since the load is measured by loading the pile and the main body separately, it is possible to easily and accurately measure the tip support force and circumferential friction force of the pile without the need for special testing work, and at low cost. It can be measured.

In addition, when the pile is driven into the ground so that the connection point between the tip and the main body of the pile is located at the interface between the diluvial layer and the alluvial layer, and a loading test is conducted between the tip and the main body, it is determined that the pile is a diluvial layer. The bearing capacity of alluvium can be measured separately.

As described above, the present invention allows the mechanical properties of geology to be easily and accurately determined, and has extremely high practical utility.

[Brief explanation of the drawing]

Figure 1 is a longitudinal cross-sectional side view of a pile used in the present invention driven into the ground, and Figure 2 is a longitudinal cross-sectional view of a pile driven into the ground with a load loaded only on the tip of the pile. Figure 3 is a side view of the pile with a load loaded only on the main body of the pile, and Figure 4 is a partial side view of the pile with a loading tester interposed between the pile and the support. be. 1 is the pile, 2 is the tip of the pile, 3 is the main body of the pile, 4
13 is a connecting device, 13 is a loading test machine, and A is underground.

Claims (1)

[Claims] 1 Connecting device 4 interposed at an appropriate location in the longitudinal direction
After driving the pile 1 in the ground A in which the tip part 2 and the main body part 3 can be freely connected, the tip part 2 and the main body part 3 are uncoupled, and the tip part of the pile 1 is tested by a loading tester 13. 2 and measure the load,
A pile loading test method characterized in that a load is then applied to the main body 3 of the pile 1 and the load is measured, and the supporting capacities of the tip 2 and the main body 3 of the pile 1 are measured separately. .