JPS6012492B2 - Root hardening method using ready-made piles - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to concrete, steel pipe concrete composite combs, hollow ready-made steel pipe combs, etc., and a method of hardening the tip of the foundation, that is, an underpinning method of the foundation. The purpose is to construct the comb using a vibration-free and noise-free construction method, and to create a bulbous body at the tip of the comb by injecting a soil hardening agent. In particular, it has the advantage of increasing resistance to the pulling force of the comb that occurs during earthquakes, and being able to deal with the occurrence of negative friction.

Ready-made combs have a more uniform material compared to place-made combs.
Although it is highly reliable and easy to manage on-site, the conventional hammer driving method is being regulated due to noise and vibration pollution problems.

For this reason, various noise-free and vibration-free construction methods have been proposed for using mottled combs, but the most popular method is the Nakahori construction method, in which hollow prefabricated combs are sunk into the ground by digging. By the way, the method of foot hardening in the medium construction method is roughly divided into a method of performing a final blow and inserting it into the ground, and a method of pouring or pouring cement milk or concrete.
However, although the final impact is for a short time, it generates vibration noise and may not provide sufficient supporting force. Also, for the latter such as cement milk injection, an auger is used.
Because the excavation diameter is not larger than the inner diameter of the comb,
The tip of the comb may be hardened only in the hollow part, and sufficient supporting force may not be obtained. Therefore, in recent years, a method of creating a large bulb at the lower end of a comb by applying the injection method using a high-pressure, high-speed jet developed has been disclosed in Tokusekki No. 51-8805 and Mochikai No. 50-42611. In both cases, the combs are laid over the bulbs, and the resistance to pull-out is low, as will be explained later. Other noise-free and vibration-free construction methods include those that apply the muddy water method and those that use the water jet method, but the former has difficulty in processing muddy water and slime, and the latter has the risk of damaging the ground. This method has the same problems as the medium excavation method. Furthermore, the vertical load of combs buried in soft ground increases due to the negative frictional force.

Also, if a positive frictional force is not expected to be very strong, all the load acting on the comb will be concentrated at the tip.
Therefore, any of the above-mentioned root hardening methods will make the hole hollow,
The blocking effect of the tip cannot be expected to be very strong, and the supporting force of the stake is proportional to the longitudinal cross-sectional area of the tip, and its absolute value is relatively small. In order to solve the above-mentioned conventional problems, this invention applies the injection method using high-pressure high-speed jet, and also performs root hardening by fixing the tip part in the middle part of the large bulb body. The details will be explained below with reference to illustrated embodiments. The comb 1 is, for example, a hollow ready-made comb made of reinforced concrete with a relatively large diameter, and the tip thereof has a larger diameter than the main body.

This is mainly used to improve workability during combing and burial in the Nakase construction method. An earth auger 3 having a wing bit 2 at the tip is inserted into the hollow part of the comb 1. In this case as well, the purpose is to increase the efficiency of embedding the comb using the Nakago method as described above, and to improve the efficiency of high-pressure injection. It is offered for the purpose of raising money. This earth auger 3 is rotated to perforate the ground, and the auger is sunk into the ground to a predetermined depth.
The material is inserted deeper into the ground than the tip of 1, and the high-pressure injection device is rotated and pulled up while injecting the ground hardening material, and water or air is also injected as necessary while excavating the ground. When the ground hardening material is injected and reaches the lower end of the ground hardening material, the state of the injection can be easily confirmed by observing the propagated sound generated by the collision of the ground hardening material. As the ground hardening material, cement milk, water glass, a mixture thereof, and other ground improvement chemicals are used.

The injection pressure is 50k9/clump or more, preferably 150~
Ground hardening material is injected at an ultra-high pressure of about 300k9/kg. Further, the rotational speed of the high-pressure injection device 4 is 1 to 1 ratio. p.
Normally, the pulling speed is 2 to 20 m/min. This high-pressure injection device may be attached to the earth auger 3, or the earth auger 3 may be pulled up and a separate high-pressure injection device may be inserted. The spraying range of the ground hardening material is approximately 0.5 to 2 depths deep, and may be greater if necessary. In addition, if the horizontal diameter is considerably wider than the diameter and the injection pressure is set to an ultra-high pressure, the soil hardening material can be injected at a distance of 5 m or more from the outer periphery.Next, the high-pressure injection device 4 is pulled up and the As shown in Figure 3, the soil hardening material is injected into the tip of the comb in an area that is considerably larger than the diameter of the comb.

At this time, the slime generated during the injection of the ground cleansing material 5 floats up and enters the hollow part of the turtle. Next &
As shown in the figure, while the injected hardening material 5 is not hardened, use a hydraulic jack and a vibrator to insert the tip of the Accordingly, the tip of the vine is located in the middle part of the ground hardening material 5 and is fixed.

Figures 5 to 7 show the test results of case A when the comb tip is positioned in the middle of the ground hardening agent as in the present invention and case B when it is not fixed. It is understood that there has been a significant increase in

Furthermore, Figure 5 is a diagram showing the soil condition, etc. of the test location. This invention has the above-mentioned structure, and ``a ground hardening material such as cement milk is injected under high pressure into the ground, excavated, mixed with excavated earth and sand to form a ready-made comb, and a bedestal, which is much larger than the conventional bedestal, is formed at the lower end. Since the comb is made from scratch, it is possible to reliably increase the supporting force of the tip of the ready-made comb.

Therefore, even if the comb could not have sufficient supporting force due to insufficient thickness of the intermediate layer, it can now be made to have sufficient supporting force. In addition, although it was necessary to sink the comb up to a strong support layer, it is now possible to sink the comb up to the middle layer and connect the tip of the comb to the support layer with a vedestal. Furthermore, it may cause slime etc.
It floats in the hollow part of the body and there is no problem in terms of strength. Most of the foundation combs constructed as described above are ready-made piles, and can have a high bending strength. In particular, the hardened material is combed while the hardened material is uncured, the tip is sunk, and the comb is positioned and fixed in the middle of the hardened ground hardening agent.
However, the connection between the tip and the bedestal part is secure, and the resistance when a pull-out force is applied to the pile is large, and the bedestal part acts effectively even against negative frictional force.

[Brief explanation of drawings]

Figure 1, Figure 2, Figure 3, and Figures 1 and 2 are longitudinal cross-sectional views showing the outline of the construction according to the construction order of this invention, Figure 5 is a diagram of the soil condition at the test site, and Figure 6 is a schematic diagram of the test specimen. , FIG. 7 is a diagram of the test results. 1... 2... Wing expansion bit, 3... Earth auger
4...High-pressure injection device 5...Curing material. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. ?

Claims (1)

[Claims] 1. A hollow ready-made pile is sunk into the ground to a predetermined depth, and then a soil hardening agent is injected into the soil at the tip of the pile at the required depth and in an area considerably wider than the diameter of the tip of the pile while rotating a high-pressure injection device. A ready-made pile root, which is floated into the ground, and is deposited while the soil hardening agent is not hardened, and the tip of the pile is positioned and fixed in the middle of the hardened soil hardening agent. Hardening method.