JPS6055119A - Compressive foot protection work for bearing subsoil of ready-made pile - Google Patents

Abstract

PURPOSE:To compact the structure of bearing subsoil by a method in which excavation is made by the excavating blade of a rotary end plate, the soil raising part through which excavated soil is discharged upwards is closed on the downside of a pile, and cement mortar is sent under pressures to below the end plate. CONSTITUTION:During the excavation, rotation force of a drill pipe 5 is transmitted from a main driving metal 9 provided to the pipe 5 to a passive metal tool 11 projectionally provided to a ring 10 provided to an end plate 2. The end plate 2 is turned. Soil excavated by the excavating blade 4 fixed to the end plate 2 is raised through a soil raising port 3 to above the end plate 2, and part of the soil is housed in a spiral lift 6 and raised in the inner path 7 and the other part of the soil is raised in an outer path 8. After bearing subsoil is reached, a pile 1 is lowered, the soil raising port 3 is closed by a ringed plate 15 on the lower end of the pile, and cement mortar is sent under pressures to region below the end plate 2. A pressure is applied to the cement mortar 17 to compact the structure of the surrounding bearing layer.

Description

[Detailed Description of the Invention] This invention pumps mortar that has been managed and prepared on the ground below the existing pile that has reached a required depth, creates a highly pure mortar root at the tip of the existing pile, and Regarding the noiseless and vibrationless construction method for compacting the original ground that supports the mortar roots, the first purpose is to compact the structure of the supporting ground around the mortar roots using a special method that is performed noiselessly and without vibrations when creating the mortar roots. The second purpose is to improve the supporting performance of the original ground that supports the mortar roots, and the second purpose is to support the tip of the prefabricated pile with the mortar roots that can always have the required strength regardless of the soil quality at the construction site. We are sure to fully support you.

Currently, as a noise-free and vibration-free construction method that attempts to strengthen the tip-bearing capacity of existing piles, a construction method in which an expanded root is created at the tip of an existing pile that has reached the required depth is widely used.
In most cases, the ground near the bottom end of the pile is excavated slightly larger than the outer diameter of the pile, and cement milk or mortar is injected into this area, and this is mixed or mixed with excavated soil in the original ground to create soil cement or mortar. A method is used to create soil mortar and create an expanded root containing excavated soil from the original ground at the tip of a prefabricated pile. The problem with the current construction methods mentioned above is that once the ground is excavated with the excavation blade, not only the excavated surface but also the original ground in an area somewhat distant from the excavated surface is affected by the excavation. The tissue loosens,
This is a point where the inherent supporting performance of the supporting ground tends to deteriorate steadily. Another problem is that since the material used to create the expanded roots includes a large amount of soil from the construction site, is there any objective or technical guarantee that the expanded roots will always maintain the required pressure resistance? There's nothing. In other words, it cannot be denied that the compressive strength of the expanded roots varies depending on the soil properties at the construction site.

This invention essentially overcomes the unavoidable weaknesses of the current construction methods aimed at reinforcing the end bearing capacity of existing piles.This invention will be described below with reference to embodiments shown in the drawings.

Embodiment I shown in FIGS. 1, 2, 3 and 4
Now, the end plate 2, which can be attached to the tip of the hollow concrete pile 1 (hereinafter referred to as the pile), has two earth and sand risers installed at symmetrical positions on the end plate 2 directly facing the ring-shaped substantial part of the pile 1. The mouth 3 is sagging, and the diameter of the end plate 2 is larger than the outer diameter of the pile 1.

Figure 1 shows the state in which the end plate 2 and the pile 1 following it have reached the support layer.
In the excavation process, the earth and sand excavated by the drilling blade 4 fixed to the end plate 2 moves to the upper part of the end plate 2 through the earth and sand ascending port 3, and a part of this excavated earth and sand is transferred to the spiral spiral protruding from the drill pipe 5. It is accommodated in the lift 6 and ascends through the inner passage 7 of the hollow part of the pile.
The other part migrates upward through an already excavated outer passage 8 along the outer peripheral surface of the pile 1. The rotational force of the drill pipe 5 is transmitted from a driving metal fitting 9 protruding from the drill pipe 5 to a passive metal fitting 11 protruding from an annular ring 10 provided on the end plate 2, and the end plate 2 rotates. Below the end plate 2 in the support layer shown in FIG.
Since it is filled with coarse sand containing around 30% clay and silt, the end plate 2 is rotated while remaining at the depth shown in the figure, and the mortar pumped through the drill pipe 5 is penetrated through the center of the end plate 2. The injection tube 13 of the cylinder 12 is fixedly connected.
It is injected into the excavated earth and sand. As this mortar injection continues, the area below the end plate 2 gradually becomes soil mortar from the bottom upward, and this soil mortar sequentially moves from the earth and sand rising port 3 to the upper side of the end plate 2, and its size increases. The parts are accommodated in the spiral lift 6. Reference numeral 14 denotes an agitator for adding resistance to the flow motion of excavated earth and mortar and causing them to twist. In this way, when a larger amount of mortar is pumped than the amount of excavated soil below the end plate, the end plate 2
The area below is filled with highly pure mortar that contains almost no excavated soil. After that, when the pile 1 is lowered while rotating the drill pipe 5, the annular plate 15 at the tip of the pile comes into contact with the upper surface of the end plate 2, as shown by the two-dot chain line in FIG.
is fitted into the inner passage 7, and the end plate 2 is attached to the lower end of the pile 1. When the end plate 2 is attached, the earth and sand ascending port 3 provided in the end plate 2 is closed by the annular plate 15. Reference numeral 16 is annular plate 1
This is a side pipe connected to 5. In other words, the pile 1 itself equipped with the annular plate 15 becomes a closed body, and the soil ascending port 3 of the end plate 2 is closed.
, and at the same time both the outer passage 8 and the inner passage 7 to the lower region of the end plate 2 are closed. On the other hand, when the end plate 2 is attached to the pile 1 as described above, the downward force acting on the end plate 2 is due to the acting weight of the pile 1, the drill pipe 5, and the upper rotating device (for public use) that operates the drill pipe 5. (Explanation is omitted.) It is the sum total of the acting weight of the excavated earth and sand in the inner passage 7 and outer passage 8, the weight of the cap 16 that houses the pile head shown in Fig. 7, and the weight of the huge load body 17, etc. Depending on the case, it is also possible to apply a downward force of the weight of the working crane to the end plate 2. The feeding pressure of the grout pump used in this example was 50 kgf/cm2 or more, and when the mortar was continued to be fed under the sealed end plate 2, the mortar feeding pressure acting on the bottom surface of the end plate was increased. Therefore, the end plate 2 gradually moves the pile 1 against the sum of the above-mentioned various downward forces acting on the end plate 2 and the frictional force between the excavated earth and sand of the outer passage 8 and the earth and sand of the surrounding original ground. This rising phenomenon of pile 1 is clearly confirmed on the ground. After the rising dimension of the pile 1 reaches the required dimension, the pumping of mortar is stopped. During the above mortar pumping process, pressure from the mortar that is at least equivalent to that acting on the unit area of the lower surface of the end plate 2 acts on the unit area of the ground below the end plate 2 in all directions, and the pressure from the mortar acts on the excavation blade 4. It is expected that the structure of the support layer in the surrounding area, which has gradually loosened over time, will return to its original structure and be modified to an even tighter structure. In this example, since expanding cement was used as the mortar material, compressive force is applied to the original ground surrounding the mortar again when the mortar expands during the chemical change process of the cement, and the structure of the supporting ground becomes even denser. materialize. FIG. 2 shows the vicinity of the lower end of the pile 1 after the installation work is completed. Below the pile 1, an expanded root 17 made of mortar is constructed, the upper part of which is reinforced by casting various steel frames. The piles are supported by the mortar expanded roots 17, which are highly reliable in terms of strength, and without exception, all the piles are supported by the supporting ground that has been compacted through the above-mentioned supporting ground compaction process, which is similar to a rapid loading test. Since it is installed above, there is no risk of unforeseen situations such as uneven settlement when the structure is actually loaded.

Next, the end plate 2 used in Example II is provided with two earth and sand ascending ports 3 at its outer edge at symmetrical positions, and on the other hand, a closing plate 18 is protruded at symmetrical positions on the side of the tip of the pile. The closing plate 18 is fixed to the side tube 16 by a connecting plate 19. When the end plate 2 is brought into contact with the lower surface of the pile 1 and the end plate 2 is rotated in the direction of arrow a shown in FIG. 6, the right end of the closing plate 18 shown in FIG. It stops at the left end of the protruding piece 20 on the end plate shown in FIG.
8, and when the end plate 2 is rotated in the direction of arrow b, the left end of the closing plate 18 shown in FIG. It then stops, and the earth and sand ascending port 3 is opened. That is, depending on the direction of rotation of the end plate 2, the earth and sand ascending port 3 is opened or closed as necessary. Note that when excavating with the end plate 2 in advance of the pile 1, the earth and sand ascending port 3 is always in an open state. A pile to which the closure plates 18 described above are connected (the closure plates 18 and the like are parts attached to the pile and belong to the scope of the pile in the broad sense described in the claims) and the outer edge. Example I shows that, in combination with the end plate 2 having an earth and sand ascending opening 3 nearby, it is possible to create an expanded mortar root on the compacted supporting ground in the same way as shown in Example I. It will be clearly understood by those skilled in the art based on the explanation.

However, when rotating the end plate 2 in contact with the pile 1, the rotational force is transmitted from the engagement part between the protrusion piece 20 and the closing plate 18, and the pile 1
Since the piles 1 and 2 rotate at the same time, a large frictional force acts between the cap 22 carrying the huge load 21 shown in FIG. 7 and the head of the pile 1, and the rotation of the pile 1 is hindered. The internal device of the cap 22 shown in FIG. 7 is a device that eliminates the above friction problem between the rotating pile 1 and the non-rotatable cap 22, and is connected to the inside upper part of the cap housing pipe 23 that houses the pile head. A slush bearing 25 made of Kelmet is fixed to the cap with bolts 24, and its lower surface is in contact with a rotating metal fitting 26, and wall-like rings 27, 27 are protruded from the inside and outside of the upper part of the rotating metal fitting 26. Liquid lubricating oil or grease is stored between the inner and outer wall rings 27, 27 to reduce the rotational friction force between the slush bearing 25 and the rotating metal fitting 26. That is, the rotational motion of the pile 1 is transmitted to the rotating metal fitting 26 via the buffer plate 28 and rotating the rotating metal fitting 26, but the rotating movement of the rotating metal fitting 26 and the thrust bearing 25
Since the rotational frictional force between the pile 1 and the pile 1 is extremely small, even if the cap 22 is held by the leader 29 of the work crane by the guide clamp 30 and the cap 22 does not rotate, the pile 1 rotates independently and smoothly. The slush bearing 25 made of Kelmet used in the embodiment can be replaced with a bearing made of phosphor bronze, gun metal, or the like. Note that several guide bolts 31 are screwed into the housing pipe 23 to prevent the rotating metal fitting 26 from swinging laterally.

Next, Embodiment III shown in FIGS. 8 and 9 will be explained. The diameter of the end plate 2 used in Example III is smaller than the outer diameter of the pile 1, and the outer half of the digging blade 4 is fixed to the end plate 2 with its outer half inclined backward with respect to the rotational direction of the arrow. When excavating soft ground, even if the inner passage 7 of the hollow part of the pile is closed with the end plate 2, the highly compressible excavated soil is subjected to large outward pressure from the inclined part 32 of the excavation blade 4, causing damage. Similar to the construction method, the pile is forcibly inserted into the surrounding ground, and the pile 1 penetrates into the ground without any congestion. When cement milk or mortar is injected from the injection tube 13 during the above process, the effect of particularly increasing the peripheral surface friction force of the pile 1 after the cement has hardened can be obtained. Since hard ground has poor compressibility, the end plate 2 is placed in advance of the pile 1, and the excavated soil is excavated upward through the inner passage 7 of the pile as the excavation progresses. Even in this case, a large pressure from the slope portion 32 acts on the original ground outside the pile. Embodiment I is similar to embodiment I, in which mortar is pumped below the pile 1 that reaches the required support layer and is in contact with the end plate 2, and the mortar layer is created on the support ground while pushing up the end plate 2 and the pile 1. The same is true.

In Embodiment III, the injection pipe 13 is extended and arranged near the outer diameter position of the pile along the stirring blade 33 connected to the end plate 2, and high-pressure mortar is injected from the injection pipe 13 while rotating the end plate 2. Therefore, during the process of pushing up pile 1, injection pipe 13
The original ground in the side wall near the tip of the pile was dislodged by the violent jetting force of the high-pressure mortar, and the outer diameter of the mortar layer tended to be somewhat larger than the outer diameter of Pile 1. By performing the above operation several times on the support layer, the diameter of the mortar layer will further expand. In addition, a vertical shaft is provided protruding from the bottom surface near the outer edge of the end plate 2,
A reamer that can rotate by a predetermined angle around this vertical axis is attached to the vertical axis, and when the end plate 2 rotates in the opposite direction, this reamer gradually opens outward, expanding and scraping off the original ground of the side wall. Then, by the above mechanical means, it is possible to reliably obtain an expanded mortar root having the required diameter.

On the other hand, in this embodiment III, the earth and sand surrounding the outer periphery of the pile is subjected to compressive force by the inclined part 32 of the excavation blade 4 over the entire length.
As a result of the repulsion, it is pressed against the outer circumferential surface of the pile, resulting in a feature that the circumferential friction force of the pile 1 is significantly improved.

In this construction method, which was explained in the above example, mortar prepared to have the required strength is pumped under the prefabricated piles that have reached the required depth. Create a high mortar root, and when creating this mortar root,
This is done by compacting the surrounding ground surrounding the mortar roots to make the supporting ground denser and strengthen the supporting capacity at the tip of the pile. Especially for long piles with deep depths, when the pile is pushed up, the support that acts as a reaction force is used. The ability to compact the ground will naturally increase, and it is expected that a bearing capacity comparable to the tip bearing capacity of piles installed using the percussion method will be obtained.

The earth and sand ascending passage in the present invention refers to the earth and sand ascending port 3, the inner passage 7 formed by the hollow part of the pile, and the outer passage 8 along the outer peripheral surface of the pile, and means a single passage or a plurality of passages. In addition, for example, the soil ascending opening 3 shown in Figs. 3 and 4 protrudes somewhat from the outer surface of the pile when the end plate 2 and the pile 1 come into contact, and some mortar leaks from this part and rises. However, as long as the phenomenon of pushing up the pile 1 is confirmed, the compaction of the original ground will be performed as required, and therefore, a state similar to such a closure also falls within the scope of the present invention.

Firstly, the support ground compression foot hardening method of the present invention described above creates a mortar root by pumping mortar that has been managed and prepared on the ground below the existing pile, so it can be used regardless of the soil quality at the construction site. The strength of the mortar roots can be made to the required strength.Secondly, by using a special method when creating the mortar roots, appropriate pressure is applied to the supporting ground in advance, compacting the supporting ground of all the piles, and It has unique characteristics in the two important points mentioned above: it can minimize the amount of pile settlement when actually loaded with a structure, and it can prevent uneven settlement of the structure. have applicable utility,
In particular, it will contribute to technological progress regarding the tip support of prefabricated piles in noiseless and vibrationless construction methods.

[Brief explanation of drawings]

Figure 1 is a partial longitudinal sectional view of the lower end of the pile that has reached the support layer, showing the main parts of the excavation equipment, and Figure 2 is the vicinity of the lower end of the pile in Figure 1 after installation has been completed in the support layer. Figure 3 is a top view of the end plate shown in Figure 1, Figure 4 is a bottom view of the end plate shown in Figure 1, and Figure 5 is a partial longitudinal sectional view of the end plate shown in Figure 1. The front view, Figure 6 is a top view of the end plate attached to the pile in Figure 5, Figure 7 is a partial longitudinal sectional view of the upper device showing the smooth rotation mechanism of the pile, and Figure 8 is a diagram of the pile and excavation device. The bottom view and FIG. 9 are front views showing the vicinity of the lower end of the pile in FIG. 8 after installation is completed. In the symbols, 1...Pile, 2...End plate, 3...Earth ascending port, 4...Drilling blade, 5...Drill pipe, 7...Inner passage for removing earth and sand,
8... Outer passage for removing earth and sand, 13... Injection pipe, 17... Expanded base made of mortar, 21... Load body, 22... Cap. Patent applicant Yukio Matsumoto

Claims (1)

[Claims] When the lower end plate of the pile reaches the required depth, the excavated earth and sand are removed upward by the excavating blade protruding from the lower part of the rotating end plate while the pile is digging. It is closed by a complementary structure at the contact surface between the pile and the end plate, and mortar is pumped under this end plate, and the pressure of this mortar pushes up the end plate and the pile, and the supporting ground and the end plate are closed. A method of compressing and foot hardening the support ground for existing piles, which is characterized by creating a mortar layer between the plates and the piles.