JPH02266020A - Method of removing negative frictional force for cast-in-place pile - Google Patents

Abstract

PURPOSE:To simply place concrete and securely remove a frictional force, by applying direct current so as for the electric conductive member side to become anode between the electric conductive member attached to the external peripheral of an excavated hole filled with mud water and the steel frame. CONSTITUTION:A circular steel net 16 of an electric conductive member is arranged at the external periphery of an excavated hole 10 formed with suspended mud water 12 of bentonite or the like and a steel frame cage 14 is installed so that the steel frame of the external peripheral does not contact the steel net 16. And direct current is applied between the steel frame cage 14 and the steel net 16 so as for the steel frame 16 to become anode. Then solid particles of bentonite or the like suspended in mud water 12 transfer to the anode steel net 16 side to form a lubricating layer 18 by an electrophoresis phenomenon. When concrete 20 is placed into the excavated hole 10 to bury the steel nets 16, it removes a negative frictional force of a cast-in-place pile due to te lubricating layer 18 between the cast-in-place pile and the inner wall of the excavated hole 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for removing negative frictional force from cast-in-place piles.

(Prior art) It is known that negative frictional force acts on piles built in soft ground, which tends to pull the piles downward as the soft ground consolidates and settles. Measures are needed to prevent this. Failure to do so may cause damage to the building structure supported by the piles.

As a method for removing such negative frictional force on piles, there is a method of taking a removal means when constructing cast-in-place piles, as disclosed in Japanese Patent Publication No. 58-58495, and a method of removing the negative frictional force when constructing cast-in-place piles, as disclosed in Japanese Patent Publication No. 58-58495. As disclosed in the publication,
A method of taking removal measures after construction of cast-in-place piles has been proposed.

The former removal method involves preparing multiple plates coated with a friction force remover such as asphalt, movably attaching these plates to a reinforcing cage, and using the pressure of the poured concrete to move the plates to the inner wall of the excavation hole. This method removes negative frictional force by pressing against the surface.

In the latter method, after constructing a cast-in-place pile, a steel pipe is driven into the outer periphery of the pile, and the steel pipe is pulled up while injecting lubricant to form a permeable layer of lubricant around the outer periphery of the pile. .

However, all of these methods of removing frictional force have the following technical problems.

(Problems to be Solved by the Invention) In other words, in the former method, concrete may enter between the friction force remover of the plate material and the borehole wall, and the effect of reducing friction force may not be sufficiently exerted. Since the plate material is attached to the reinforcing bar cage, the diameter of the reinforcing bar cage becomes correspondingly smaller, and the strength against bending and shearing force of the pile decreases.

In addition, in the latter method, the diameter of the cast-in-place pile is large and
At great depths, it becomes difficult to drive or pull out the steel pipes, and the construction process takes time, prolonging the construction period.

The present invention was made in view of these conventional problems, and its purpose is to provide a method that is easy to implement and that can reliably remove negative frictional force. It's about doing.

(Means for Solving the Problem) In order to achieve the above object, the present invention forms an excavation hole while filling the ground with muddy water, inserts a reinforcing bar into the excavation hole, and then inserts a reinforcing bar into the excavation hole. In a method of constructing cast-in-place piles by placing concrete, before placing the concrete, a conductive member is installed at the outer periphery of the excavation hole, and a conductive member is installed between the reinforcing bar and the conductive member. The method is characterized in that a DC voltage is applied such that the conductive member side becomes a positive electrode.

(Function) According to the method for removing negative frictional force from a cast-in-place pile with the above configuration,
Before pouring concrete, a conductive member is installed at the outer periphery of the excavation hole, and when a DC voltage is applied between the reinforcing bar and the conductive member, with the conductive member being the positive electrode, the excavation hole Solid particles such as bentonite in the muddy water that fills the inside move toward the conductive member, which is the positive electrode, due to electrophoresis and accumulate in a layer.

Therefore, if concrete is poured into the borehole in this state, there will be a gap between the cast-in-place pile and the inner wall of the borehole.
A lubricating layer, such as bentonite, is interposed, which eliminates the negative frictional forces of cast-in-place piles.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the method for removing negative frictional force from a cast-in-place pile according to the present invention.

In the removal method shown in FIG. 1, first, an excavation hole 10 is formed to a predetermined depth in the soft ground E, as shown in FIG. 1(A).

The excavated hole 10 is formed while being filled with muddy water 12 in which bentonite or the like is suspended.

When the excavation hole 10 is formed, first, a wire mesh 6 as a conductive member assembled in an annular shape with both ends open is installed on the outer peripheral edge of the excavation hole 10 .

In this case, the length of the wire mesh 16 is set to be approximately the same as the excavation depth of the excavation hole 10.

Next, the reinforcing bar front 14 is erected. At that time, 14 in front of the reinforcing bar
Insulating spacers are provided around the reinforcing bars around the outer circumference of the reinforcing bars to prevent them from coming into contact with the wire mesh 16 as a conductive member.

Note that it is also possible to set a wire mesh in advance on the outer periphery of the front reinforcing bar 14 via an insulating spacer and install it in the excavated hole 10.

A DC voltage is applied between the reinforcing bar basket 14 and the wire mesh 16, with the wire mesh 6 side being the positive pole (see FIG.
See B).

When a DC voltage is applied, muddy water 1 due to electrophoresis phenomenon
Since the solid particles such as bentonite in 2 are negatively charged during boat fishing, they move to the wire mesh 16 side, which is the positive electrode, and are accumulated.

The accumulated solid particles fill the spaces between the meshes of the wire mesh 16, forming a layer to form a lubricating layer]8.

At this time, the thickness of the "a" slipping layer 18 is determined by the magnitude of the DC voltage,
It is adjusted as appropriate based on conditions such as the application time and solid content concentration in the muddy water 12, and the diameter of the cast-in-place pile to be formed.

Further, when the wire mesh 16 is used as the six holes of the lubricating layer 18, solid particles in the muddy water 12 enter between the wire meshes, and thereby the lubricating layer 18 maintains a predetermined shape over a long period of time. At the same time, the wire mesh] 6 also ensures flexibility, so the wire mesh] 6 is suitable as the conductive member on the positive electrode side.

When the lubricating layer 18 requires a considerable thickness, the wire mesh 16
It is preferable to form it into a three-dimensional net.

Further, the outer periphery of the wire mesh 16 may be coated with carbon fiber, which is also a conductive member, and a more flexible lubricating layer can be expected.

When the lubricating layer 18 has been formed to a desired thickness, it is shown in FIG.
), there is concrete 18 in the excavation hole]
When the concrete 18 is poured and the concrete 18 hardens, as shown in Fig. 1 (
As shown in D), a predetermined cast-in-place pile is constructed.

When the cast-in-place pile is constructed in this way, solid content in the muddy water 12 such as bentonite is present between the concrete 18 of the cast-in-place pile and the inner wall surface of the excavated hole 1o, that is, the surrounding ground. Since the lubricating layer 18 deposited around the wire mesh 16 is interposed, when the soft ground E sinks, only the ground E sinks while sliding due to this lubricating layer [8], which causes the cast-in-place pile to sink. Negative frictional forces are prevented from acting.

In this case, the thickness of the lubricating layer 18 only needs to be slightly larger than the thickness of the wire mesh 16, for example, so that it hardly affects the strength of the cast-in-place pile against bending and shearing forces.

In addition, in the above embodiment, the wire mesh 16 was exemplified as the conductive member on the positive electrode side to which a DC voltage is applied, but the implementation of the present invention is not limited to this, and for example, punching metal etc. may be used. .

(Effects of the Invention) As explained above in the embodiments, according to the method for removing negative friction force of cast-in-place piles according to the present invention, in the process of constructing cast-in-place piles, before pouring concrete, A simple method of installing a conductive member on the outer periphery of the pile and applying a DC voltage with the conductive member as the positive pole between the reinforcing bar and the conductive member increases the strength of the pile against bending and shearing forces. An excellent effect can be obtained in that negative frictional force can be reliably removed without reducing the frictional force.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the method of the present invention in the order of steps. ]O・・・・・・・・・Drilling hole】2・・・・・・・・・Muddy water 14・・・・・・・・・Rebar cage

Claims (1)

[Claims] In the method of constructing cast-in-place piles by forming an excavation hole in the ground while filling it with muddy water, inserting reinforcing bars into the excavation hole, and then pouring concrete into the excavation hole to construct cast-in-place piles, the concrete is poured. A location characterized in that, beforehand, a conductive member is installed on the outer peripheral edge of the excavation hole, and a DC voltage is applied between the reinforcing bar and the conductive member, with the conductive member side being the positive electrode. A method for removing negative frictional force from driven piles.