JPH0121286B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a foundation pile whose lower end is swollen in the shape of a knob and its construction method, and in particular, after a prestressed concrete pile is driven into the soil, a large conical concrete knob is formed at its lower end. This relates to a method of driving foundation piles that stabilizes the land by solidifying the surrounding soil and pouring mortar.

[Prior art]

Traditionally, problems with pile foundations have been the problem of the support piles penetrating into the ground and anchoring in the hard soil layer, which has troubled designers as well. Prior to designing this foundation, a soil survey was conducted using a combination of boring, sampling, and penetration tests to determine the anchorage point for the piles, but the problem was deciding on that location. In other words, a strong hard soil layer is most desirable in order to support the upper building and prevent subsidence, but depending on the location, these soil layers may be several tens of meters underground, or even 100 meters underground.
Because it is hidden at a depth of less than 100 meters, the number of piles is often increased and a sub-rigid soil layer close to the ground surface is adopted due to the difficulty of construction and the large construction cost, resulting in an extremely low bearing capacity (QA). The reality is that we are forced to choose a relatively small soft soil layer.

In addition, a supporting pile is one in which the lower end of the pile reaches the hard ground, and most of the load is supported by the tip of the pile. If you are forced to choose, consider the allowable bearing capacity (QA) of the soil on the support surface of the pile tip.
Efforts were being made to increase the number of piles and pile diameter in order to keep the value below. However, these efforts not only increased material costs and construction costs and were unprofitable, but also caused excessive pile impact and Vibrations disturb the soil structure around the piles, which can lead to foundation subsidence or even uneven subsidence.

When designing a pile foundation, the number and diameter of piles must be in accordance with the allowable bearing capacity of the soil on the support surface of the pile tip, and the number of piles must be within the range of allowable bearing capacity of the piles. In other words, the ideal was that the piles would be fully utilized to the extent of their permissible bearing capacity. However, in practice, it is extremely difficult to satisfy both requirements at the same time, and the reality is that the bearing capacity of the pile cannot be fully utilized due to the low qa of the pile bearing surface. This also results in wasted materials, and is a problem that awaits a solution in the future.

In addition, we offer prestressed concrete piles and steel piles that are driven directly into the soil with conventional pile drivers, and places where hollow pours are formed by boring with a rotating excavator and concrete is poured into them to form them. We will discuss cast concrete piles and pedestal piles, which are a type of cast-in-place construction method in which a steel pipe is driven into the soil, then removed and replaced, and the space is filled with concrete mortar and formed, focusing on their materials and driving method. If not, the following problems may arise. In other words, (a), the main purpose of foundation piles is to transmit the upper load to a certain depth in the ground. For this reason, the bearing capacity of the support surface becomes an issue, and as described above, the position of the support surface must be selected. If one is forced to choose a subhard soil layer close to the ground surface, the reason why prestressed concrete pile and steel pile foundations cannot necessarily be said to be superior to pier foundations in terms of foundation engineering is that the diameter of the piles is congenital. This is because the load is limited to the support surface and acts on the supporting surface at points, so it is more likely to cause settlement or uneven settlement than a pier foundation.

(b) Also, like the above-mentioned pedestal pile, the working surface is made into a planar shape by forming a concrete bulb. This seems to be due to the fact that the lower end of the pile was formed into a bulbous shape in order to accommodate the supporting soil layer with a small qa due to the limitation of the height of the pile.Also, there is a limit to the bearing capacity of the pile itself, so it cannot be used except for economic reasons. It is not suitable for supporting large loads.

[Purpose of the invention]

The present invention has been proposed to overcome the above-mentioned deficiencies and inconveniences. That is, the main object of the present invention is to provide a foundation pile driving method in which the lower end of the pile is formed into a large conical concrete hump and the support pressure on the support surface is reduced.

The next object of the present invention is to provide a method for increasing the bearing capacity and frictional force of the ground by injecting a soil stabilizer and mortar to consolidate the soil around the ground and bring the surrounding surface of the pile into close contact with the ground. It's about trying.

[Structure of the invention]

In order to achieve the above object, the present invention has a prestressed concrete pile with a hollow core and a removable hollow conical pile shoe at the lower end, which is driven into a predetermined ground, First, separate the pile shoe from the pile body and drive it down to approximately 2 meters below the pile. Next, insert a digging device (excavation device) through the hollow core of the pile, and insert it along the tip of its rotating shaft. The excavation member (excavation member), which has a large number of strong flexible cords connected to it, is centrifugally rotated near the top of the pile by high-speed rotation of the rotating shaft to cut and crush the surrounding wall, while water is injected. In addition to assisting the digging work (excavation work), the excavated soil is formed into a hydrated sol, which is sucked out of the pile by a suction pump, and the sand and gravel that does not become a sol sinks downward. forming an almost circular cavity,
A steel frame made of reinforcing bars or angles is inserted into the cavity, and after expansion and construction, the cavity is filled with concrete mortar using pressurized pulp, and after a predetermined curing time, the concrete mortar solidifies and forms a circular shape. When it is formed into a concrete hump, a soil stabilizer is poured from the pressurized pulp into the soil around the pile and the hump to solidify it, and immediately after that, it is poured upward from the lower end with mortar to fill the surrounding air. It is characterized by the fact that it can be buried to form a stable land industry.

The above foundation pile has a circular concrete hump shape,
Preferably, it is formed into a conical or bell shape with a wide end, and this is achieved by appropriately adjusting the length of the prong member on the rotating shaft.

〔Example〕

The above and other objects and features will become more apparent when the embodiments are described with reference to the accompanying drawings.

In Figures 1 and 2, P is a pile body with a hollow core, 10 is a hollow conical pile shoe removably attached to the lower end of P, and this pile is driven directly into the specified ground using a pile driver. After driving in, in order to release the pile shoe,
The pile shoe 10 is subsequently struck with a hammer via the core rod 11.

In FIG. 3, the hit pile shoe 10 separates from the pile body P and is fixed at a location about 2 meters below the pile. Reference numeral 12 is a round rod-shaped shank device having a rotating body at its tip and connected to a shank member 13 made of a wire rope group, and is inserted into the vicinity of the top of the pile shoe 10 from the hollow part of the pile. I is a stabilizer that holds the ramming device so that it can rotate.

In FIGS. 4 and 5, by high-speed rotation of the rotary shaft of the above-mentioned cutting device 12, the cutting member 13, whose cord is lengthened as it goes downward, is centrifugally rotated to crush its surrounding wall 14, while the water is injected to assist the cutting work and form the cut soil into a hydrated sol, which is then pumped into a suction pump (not shown).
While being sucked out of the pile, the sand and gravel that does not become a sol is allowed to sink to a lower part 15, forming a cavity 16 in the shape of a wide cone with a radius equal to the length of each wire rope.

In FIGS. 6 and 7, reference numeral 17 denotes an ultrasonic device, which is passed through the cavity 16 after the device is taken out and used to measure the volume and shape of the cavity.
Reference numeral 18 denotes a steel framework made up of a collapsible combination of reinforcing bars or angles that can be expanded by manipulating them from above through a pipe or the like, which is folded and inserted into the cavity 16 from the hollow part of the pile, where it is inserted into the cavity 16 as shown in the figure. Spread it out like an umbrella.

In Figures 8 and 9, H is a pressure pipe inserted vertically deep into the cavity 16. When filling concrete mortar, the pressure is balanced with water so that the pipe outlet 19 is not blocked. The cavity 16 is completely filled with concrete mortar from the hollow core on the outer periphery of the pressure pipe while maintaining the flow at the pipe outlet.

In Fig. 10 and Fig. 11, the hatching is the concrete part 2 filled to the full with the cavity 16.
After 4 to 5 hours, the concrete enters the setting process and is formed into a wide cone-shaped concrete lump. At this time, the soil stabilizer is poured from the pressure pipe H into the soil 21 around the pile and the concrete hump to solidify it, and immediately after that, it is pumped upward from the lower end with mortar as shown by the "X" symbol in 22. to fill surrounding voids.

〔Effect of the invention〕

In this way, according to the above construction method, the working surface of the pile tip becomes a large surface from a point, and the support pressure of the soil supporting surface is reduced, so that the foundation pile can be moved closer to the ground surface without increasing the number or diameter of the piles. It becomes possible to anchor it in hard soil layers and even soft soil layers, which greatly reduces the cost of building foundations and contributes to the stability of the land industry. In addition, the foundation piles created using this method combine the advantages of pre-cast piles and cast-in-place concrete piles; the high bearing capacity of the pre-cast piles themselves is maintained, and the wide end of the cast-in-place bulbous piles is further enlarged several times, resulting in a low-support pile. It becomes possible to support a relatively large load on the ground with a relatively small number of piles.

In addition, by combining the use of a peg member made of strong flexible cord with clever shaft rotation, walls can be easily cut, and unlike conventional bulbous piles, the pile is not restricted by the ground conditions at the bottom end of the pile. There is no.

In addition, since a frame consisting of reinforcing bars or angles can be directly inserted into the concrete hump at the bottom of the pile, the concrete hump is reinforced, creating a strong column base and improving the top load transmission function.

Furthermore, since the pressure pipe can be inserted deep into the cavity at the bottom of the pile and between the permeable sand and gravel, soil stabilizers and mortar can be easily injected and all the soil surrounding the land can be injected. Since it can consolidate and fill voids, the stability of the land industry is greatly enhanced.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the state in which the foundation piles have been driven.
Figure 2 is a cross-sectional view showing the state in which the pile shoe is further driven down by the core rod, Figures 3 to 5 are cross-sectional views showing the process of cutting the cavity between the pile tip and the pile shoe using a carving device; Figure 6 is a cross-sectional view showing the inside of the cavity being surveyed, Figure 7 is a schematic cross-sectional view of the frame construction, Figure 8 is a cross-sectional view showing the state in which pressurized pulp H is inserted, and Figure 9 is a cross-sectional view of the concrete. 10 and 11 are cross-sectional views showing the state in which a soil stabilizer and mortar are injected, respectively. P...Pile body, H...Pressure pipe, 10...Hollow conical pile shoe, 11...Core rod, 12...Drilling device, 13...Drilling member, 14...Peripheral wall, 15...
Gravel, 16... Cavity, 17... Ultrasonic device, 18... Frame, 19... Pipe outlet, 20... Concrete section, 21... Filling soil, 22... Mortar.

Claims (1)

[Claims] 1. A prestressed concrete pile with a hollow core and a removable hollow conical pile shoe at the lower end is driven into a predetermined ground, and the pile shoe is attached to the pile body along the hollow part through the core rod. Next, a screwdriver is inserted into the hollow core of the pile, and a screwdriver is connected to a large number of strong flexible cords along the tip of the rotating shaft. The tsugi member is centrifugally rotated near the top of the pile shoe by high-speed rotation of the rotary shaft to cut and crush the surrounding wall.Water is injected to assist the tsugi work, and the cut soil is transformed into a hydrated sol. formed into
By sucking these out of the pile with a suction pump and letting the sand and gravel that does not become a sol sink downward, a nearly circular cavity is formed at the bottom end of the pile, and a steel framework made of reinforcing bars or angles is inserted into the cavity. After the expansion and erection, the cavity is filled with concrete mortar using pressurized pulp, and after the specified curing time, when the concrete mortar solidifies and is formed into a circular concrete lump, the soil quality is more stable than the pressurized pulp. Pour the agent onto the fence around the pile and the hump to solidify it,
A foundation pile driving method characterized by immediately pouring mortar upward from the lower end to fill the surrounding void and form a stable foundation pile. 2. The cord of the rake member connected to the lower end of the rotating shaft of the former rake device is characterized by being made of a wire rope, and the wire rope is made longer than the radius of the pile according to the predetermined knob shape. A foundation pile driving method according to claim 1. 3. The steel framework formed by combining the reinforcing bars or angles is foldable and assembled into an umbrella shape, and is folded when inserted into the circular cavity, and after insertion is stretched and expanded into the original umbrella shape. A method for driving a foundation pile according to claim 1. 4. Claim 1 is characterized in that the length of the cord of the scooping member is appropriately adjusted so as to become longer as it goes downward, thereby forming a conical or bell-shaped cavity. The foundation pile driving method described.