JPS6112053B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a method for burying ready-made hollow piles, and the purpose of the invention is to enable foundation piles with a large bearing capacity to be erected without vibration or noise, and to be able to be applied to a wide range of ground types. To make it possible to reliably form a stable and large-shaped support root at the tip of a ready-made hollow pile.

Embodiments of the present invention and their effects will be described below with reference to the drawings.

First, a hollow ready-made pile 1 is inserted up to a predetermined support layer using the hollow digging method. That is, the auger 2 is inserted through the hollow part of the pile 1, and while the auger excavates in advance, a hydraulic load P is applied from the rear of the pile 1.
Add pile 1 and sink it to a specified depth underground. It is preferable that the auger 2 used at this time has a rotational diameter as close as possible to the diameter of the pile 1, for example, an auger 2 having a rotational diameter smaller than the diameter of the pile 1 by about 20 to 40 mm. Auger 2 is 80~ higher than the tip of pile 1 when sinking pile 1.
When insertion is completed to a predetermined depth of 100 cm, a layer of loosened soil is formed in front of the tip of pile 1, but this range is at most the diameter of the auger or the depth of the predetermined depth. That's about it.
(See Figures 1 and 2) It is not necessary to form this loosened soil layer.
It is necessary to increase workability and reliability when pressing in by applying a load from the rear when sinking, and if the area of the soil layer to be loosened is too small, install a spreading blade on the auger 2 and enlarge it as appropriate. I am dealing with it. After this, the auger 2 is pulled out, and the first stage of sinking is completed.
However, as it is, the bearing capacity cannot be exerted as it is, so the normal medium excavation method uses a diesel hammer or a weight to strike the pile head and drive it deeper than the loosened soil layer to increase the bearing capacity. I'm making the most of it. However, in this case, noise and vibration occur, albeit for a short time. This construction method aims to completely eliminate this final noise and vibration.

That is, a hardening agent is applied to the loosened soft soil layer below the tip of a pile that has been sunk to a predetermined depth using a high-pressure jet to form a thick hardened material in a wide range below and along the bottom of the tip of the pile. Therefore, the curing agent supply injection rod 3 with the tip of the injection nozzle 5 opened as close to the inner wall of the pile as possible is inserted into the hollow part, and after the rod 3 reaches the vicinity of the tip of the pile, the rod 3 is rotated. Start high pressure water injection and continue insertion. Thereafter, the injection nozzle 5 of the rod 3 reaches the tip of the pile, passes through the tip and is inserted into the soil layer, when it begins to excavate the soil layer. The final purpose of this method is to form a hardened material over a wide area at the bottom of the pile, but even if the hardening agent is injected directly into the soil layer, it can be easily injected into the soil layer that has been loosened by the auger. In a wider area than that, there is usually a very compact soil layer, so it cannot be easily injected. For this purpose, the soil layer of the supporting ground is preliminarily excavated to a diameter larger than the pile diameter using the aforementioned water injection. Since water injection is only a preliminary measure and an auxiliary means for the curing agent that will be injected later, it must be done as efficiently and for a short period of time as possible, and disturbance of the soil layer must be prevented.

Normally, this high-pressure water jet has a pressure of 100 to 250 kg/cm ² , and excavation is performed while descending, and depending on the hardness of the soil layer, only rotation is given during insertion, and the descent is temporarily stopped. After that, after the curing agent supply injection rod 3 reaches the scheduled injection depth, the water is switched to the curing agent (the second
(See Figures 4 to 4). There are various types of hardening agents, both organic and inorganic, but cement milk is preferred as it avoids organic materials that are harmful to humans and animals, and is economical. The compressive strength of the injected hardening agent is 50, considering the strength required for the hardened product to exhibit supporting capacity.
Kg/ ^cm2 or more is required. Therefore, in the case of cement milk, the water to cement weight ratio is 1:1.
A range of 1:2 is preferred.

In this invention, the pressure required for injecting the hardening agent is
It is 150-300Kg/ ^cm2 . For this reason, the diameter of the injection nozzle 5 mentioned above needs to be 2.6 mm to 3.0 mmφ,
Since it is necessary to change the nozzle diameter depending on the ground, it is necessary to have a removable shape.

The pressure at the time of injection of water and the pressure at the time of injection of cement milk can be determined by a gauge provided near the outlet of a conventionally used pump, which is a commonly practiced method.

In this way, hardening agent injection starts from the lower level of the soil layer that has been pre-excavated, and by pulling up and rotating the injection rod, the jet opening is rotated around the longitudinal axis of the pile, and the jet is evenly impinged on the ground in front of the pile tip. By injecting cement milk, pile 1
It is possible to form a supporting root portion 4 having a large downward area and depth, having a generally cylindrical shape, and having a large supporting force.

The structure of this invention is as described above, in which preliminary excavation is performed with high-pressure water at a gauge pressure of 100 to 250 kg/cm ² , and then a gauge pressure of 150 to 250 kg/cm 2 is applied at a gauge pressure higher than the water injection pressure.
Since the cement milk is injected directly at a high pressure of 300 kg/cm ² , the cement milk is spread widely in the sand or gravel ground and directly on the ground wall. Therefore, the diameter of the enlarged bulb is significantly larger than that of the conventional example, and it is possible to reliably produce a high-quality bulb that does not contain slime or the like. The dimensions of the cylindrical shape of the bulb are 100 to 150 cm in diameter and a support root of about 100 cm in height can be created, but the height is determined by the insertion length of the rod, so if necessary, the insertion length can be made extremely long. It is also possible to form a cylinder. The main problem is the diameter, but if you directly inject the hardening agent without using the high-pressure water jet mentioned above, you can only get a diameter of about 50 to 70 cm, and the result is unstable, making it difficult to adopt as a construction method. . There is also a method of inserting a pile after digging with an auger, and then inserting an injection rod using the hollow part of the pile, and then injecting hardening agent, but in this case, digging with an auger will prevent the ground from collapsing. It is impossible to simply insert the pile into the ground without getting stuck. In particular, this method requires an open-end shape in order to insert the rod, and even if it were possible to insert the rod, the consolidated earth and sand would completely flow into the hollow part of the pile, and then It is not possible to insert the rod easily. In order to prevent the ground from collapsing during auger excavation, there is a method of filling the auger excavation well with bentonite solution, but there was a problem in disposing of the overflowing bentonite solution, so this method was newly developed. This is a medium excavation method. In addition, preliminary excavation using water during injection may seem unreasonable at first glance as it protrudes into the ground, but the underground part is usually saturated with groundwater.
Unlike when using new water, there is no problem. Further, since the water can be injected later and is injected at a higher speed than the preliminarily excavated area, the water treatment area can be completely replaced with hardening agent-containing ground, and a strong support hardening agent can be formed. (See FIG. 7) Examples will be shown below.

This invention was carried out under the following conditions, and the experiment to determine its ability was as follows.

(1) Location Sand ground with a pile length of 15 m (2) Injection conditions Nozzle used 28φ Preliminary excavation with water Rotation 5 rpm Descending speed 5 cm/min (no stop on the way) Injection amount 60/min Gauge pressure during injection 190 Kg/
cm ² Cement milk injection Injectant formulation Water to cement weight ratio 1:1.5 Rotation 5rpm Rising speed 5cm/min Injection amount 60/min Gauge pressure during injection 220
Kg/cm ² (3) Finished bulb diameter Average in X direction 125cm Average in Y direction 115cm Height 101cm

[Brief explanation of the drawing]

1, 2, 3, 4, 5, 6, and 7 are cross-sectional views showing an outline of the construction of the present invention in the order of construction. 1... Ready-made hollow pile, 2... Auger, 3...
Hardening agent supply squirting rod, 4...Support root, 5...
injection nozzle.

Claims (1)

[Claims] 1 Insert the auger into the hollow part of the ready-made hollow pile,
sinking the pile to a predetermined depth by rotating an auger to excavate in advance toward the tip of the hollow pile and applying hydraulic pressure to the rear of the hollow pile;
After pulling out the auger, a curing agent supply injection rod having an injection nozzle is inserted into the hollow part of the pile, and when the injection nozzle passes through the tip of the pile, a high pressure of 100 to 250 kg/cm ² is applied while rotating the rod. Inject water, continue inserting the rod, pre-drill the supporting ground to a size larger than the pile diameter, insert the rod to the specified depth, switch the high pressure water of the rod to cement milk, and use it to generate 150 to 300 kg/ A method for burying ready-made hollow piles, which is characterized by forming a support root with a larger diameter at the tip of the pile than when water is sprayed by injecting cm ² of high-pressure cement milk and pulling up the rod while pressuring it to rotate.