JPS6034648B2 - Pile driving method into bedrock - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for driving piles into bedrock, and more specifically, when driving a pile into bedrock, the pile is driven while expelling crushed stone crushed by the impact to others. This relates to the method of driving piles into bedrock.

In the conventional pile driving method, the tip of a water guide pipe is fixed to the tip of piles such as H-shaped steel, Type 1 steel, steel sheet piles, and steel pipe piles, and a large amount of high-pressure water is injected from this water guide pipe to drive the pile to the driving position. There is a method of softening or fluidizing the soil and driving piles using a vibrating pile driver.

This construction method attempts to reduce the resistance force at the tip of the pile and the frictional resistance around the pile by fluidizing the earth and sand near the impact point at the tip of the pile using water jets, compared to the case where the earth and sand are not fluidized. Although it has the advantage of increasing the effectiveness, this construction method originally had an N value (standard penetration test value) of 50 or less, that is,
Since it was designed for general sand, the N value is 50.
It was said that it was impossible to drive into bedrock.
Therefore, we researched the use of the above method for driving piles into bedrock, for example, by firmly fixing the water guide pipe to the pile, increasing the amount of water injected, and increasing the water pressure to encourage the crushing of the bedrock by high-pressure, large-volume jetting. I tried as hard as I could, but it didn't work on the bedrock at all. Therefore, until now,
Common sense dictates that it is impossible to drive piles directly into bedrock, and when it is unavoidable, the work is done by drilling a hole with a boring machine and then driving the pile.

This work is complicated, and even more so when driving into underwater rock. Therefore, the present inventors investigated the reason why the above-mentioned construction method was not applicable to piling in bedrock, and found that if a large amount of high-pressure water is injected into hard ground, a reverse jet force will always work and the water guide pipe will be damaged. It was discovered that this was done to reduce the energy of the piles that were trying to strike the bedrock by exerting the reverse jet force on the fixed piles.

In other words, the present invention, which was achieved as a result of intensive research based on this knowledge, allows piles to be easily driven into bedrock, which was previously thought to be impossible. The jet water that prevents cushioning can remove crushed rock in the best position when it is most efficient, and also prevents the jet water from affecting the pile when the pile hits the bedrock, thereby preventing the pile from hitting the bedrock. The purpose is to provide a pile driving method with improved strength.

Next, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a vibratory pile driver, such as a pipe hammer A, is suspended from a crane C. This pipe hammer A has a pipe main body 1 to be driven into the bedrock D.
It is installed so that the vibrations oscillated from C are transmitted. This pile body 1 preferably has a number of water guide pipes 2 along the inner green part of the pile body 1 according to the size of the pile, that is, the amount of crushed rock to be removed. It is located near the point of impact. The water guide pipe 2 is disposed so as to be freely movable relative to the pile body 1, for example, in the vertical direction and, if necessary, in the horizontal direction. This water guide pipe 2 uses a nozzle 4 at its tip to apply pressure and water volume that can remove crushed rock from the impact point of the pile body 1.
For example, it is connected to a high water pressure pump B so that the water is injected from the water. To explain the relationship between the water guide pipe 2 and the pile main body 1 mentioned above, in Figs. Place hardware 3 on both flanges b and l, respectively.
b'' is fixed, and the water guide pipe 2 is inserted into the gap formed between the steady rest hardware 3 and the web la.

As shown in FIG. 5 above, this water guide pipe 2 is connected to the pile body 1 with a certain amount of clearance, for example, by a hanging hardware 5 such as a wire or a chain. In addition, when placing the water guide pipe 2 on the pile body 1, if the pile body 1 is a steel pipe, as shown in FIG. The steady rest hardware 3 may be attached to two opposite locations along the line, and the water guide pipe 2 may be moved into the respective gaps formed by the inner edge of the steel pipe and the steady rest hardware 3.

Now, when driving the pile body 1 into the bedrock, the bedrock P on the seabed is sloped and uneven, and is affected by ocean currents, so the pile body 1 cannot stand on its own, so a temporary work scaffold is erected, and high-pressure water is introduced to the pile body 1 on board the ship. Attach pipe 2 with hanging hardware. Next, after starting the high water pressure pump B and inspecting the nozzle 4,
The pile body 1 is erected and a pipero hammer (vibrating pile driver) A is attached to the end of the pile body 1. From this state, the high water pressure pump B is started, the pipe hammer A is started, and the pile body 1 is driven. During this driving, the vibrations caused by the pipe hammer A are transmitted to the pile body 1, so that the tip of the pile body 1 hits the rock D. This impact causes the tip of the pile body 1 to crush the struck portion of the rock D, and the pile body 1 separates from the rock D due to the reaction force. At this time, the nozzle 4 of the water guide pipe 2 is tensed as the hanging hardware 5 separates from the bedrock D of the pile body 1, and remains near the bedrock D until the water guide pipe 2 is pulled up, during which time it is crushed at the point of impact. Remove rocks with water flow. Therefore, since the nozzle 4 removes the crushed rock at the closest position to the crushed rock, it can be removed efficiently, and at the time of this removal, the pile body 1 is in the direction away from the rock D, so there is nothing on the pile body 1. No impact. In other words, the good exclusion effect means that it is economical because the pressure and amount of water to be injected can be reduced. In this way, water conveyance pipe 2 with crushed rocks eliminated
, due to the separation of the pile body 1 from the bedrock D, the hanging hardware 5
However, at this time, the pile body 1
has started moving towards bedrock D for the blow, so
When the pile body 1 hits the bedrock D, the water guide pipe 2 is located away from the bedrock D.

Therefore, the action of the jetted water on the bedrock D is weakened, and during this time the pile body 1 hits the bedrock D, so that the jetted water does not reduce the energy of the pile body 1 when the pile body 1 is hit. As a result, the impact effect can be enhanced. In addition, since the nozzle 4 also hits the rock D to make a hole and bites into the rock D together with the pile main body 1, even if the pile main body 1 is driven into the rock D, the same effect as described above is achieved. The method of driving piles into bedrock D in this manner can be applied not only to land but also to bedrock underwater.

As described above, according to the present invention, the water guide pipe 2 is suspended in the gap formed by the steady rest hardware 3 and the pile body 1,
In addition, the water guide pipe 2 is suspended from the pile body 1 above the steadying hardware 3, and when the pile body 1 fractures the rock and jumps up due to the repulsive force, the water jetted from the water guide pipe 2 displaces the crushed rock. When the pile body 1 jumps up due to the reverse jetting force of the water jetted from the water guide pipe 2, the pile body 1 falls and hits the rock again to break it.
In this way, the pile main body 1 and the water guide pipe 2 repeat the vertical movement alternately. Therefore, the reverse jetting force caused by the water jetted from the water guide pipe 2 does not directly act on the pile body, and the impact energy of the pile body 1 is not reduced.

In addition, since the pile body 1 and the water guide pipe 2 alternately move up and down, crushed rocks can be reliably removed, and no crushed rocks remain at the tip of the pile body 1 during impact.

As a result, a so-called sand cushion, in which the impact force of the pile body 1 is weakened by the remaining crushed rock, does not occur. Therefore, according to the present invention, it is possible to easily drive a pile into rock with an N value of 50 or more, which was previously considered impossible.

Furthermore, the water jet only needs to have enough water pressure and flow to remove the crushed rocks, and there is no need to soften the ground or crush the rocks with the jet water as in the past, so the water pressure and amount can be kept to a minimum. It is possible to drive piles into bedrock efficiently.

Furthermore, since the water guide pipe 2 is in a suspended state, horizontal shaking of the water guide pipe 2 during water injection is prevented as much as possible, and the removal efficiency of crushed coal is increased.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of this invention, Fig. 2, Fig. 3
The figures are cross-sectional views showing embodiments of the pile main body used in this invention, FIG. 4 is a perspective view showing the nozzle 4 provided at the tip of the water guide pipe 2 used in this invention, and FIG. FIG. 1... Pile body, 2... Water guide pipe, A...
...Vibration pile driver, D...Bedrock. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A pile body 1 consisting of a water guide pipe 2 supported so as to be able to rise and fall via a steady rest hardware 3 is erected on a bedrock D, and from this state, a high water pressure pump B connected to the water guide pipe 2 is started. While supplying high-pressure water, the vibrohammer A attached to the pile body 1 is started to drive the pile body 1 into the bedrock D to crush the bedrock 4, and the pile body 1 and the water guide pipe 2 are alternately connected. A method for driving piles into bedrock, which is characterized by sequentially driving the pile body 1 into bedrock D while removing crushed rocks by lifting and lowering operations.