JP2789239B2 - Partially covered sand pile construction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a partially covered sand pile in which a part of the sand pile is covered with a water-permeable cylinder when forming the sand pile in soft ground. .

[Prior Art] This kind of partially covered sand pile construction method is employed particularly for an improvement method for a ground in which a layer having a weak binding force to sand piles and a relatively strong layer are mixed.

In this method, the water-permeable cylinder must be set at a predetermined position in the hollow pipe according to the position of the layer of soft clay or silt in the ground (hereinafter referred to as the ultra-soft layer) and the thickness of the ultra-soft layer. Conventionally, the following steps have been adopted.

After stopping so that the lower end of the hollow tube is near the ground surface, lower the guide tube movably suspended in the hollow tube, and detachably connect the upper end of the water-permeable tube to the lower end of the guide tube. Hold. Thereafter, the guide tube is pulled up to hold the water permeable tube at a predetermined position in the hollow tube in a suspended state.

Next, the hollow pipe is penetrated into the ground, sand is injected and filled in the hollow pipe during or after the penetration, and then the hollow pipe is penetrated to the pile formation depth while applying vibration to the hollow pipe. The pipe is drawn from the ground, and a partially covered sand pile is formed in the ground during the drawing process.

Here, the water-permeable cylinder is released from connection with the guide tube immediately before, for example, during the drawing process of the hollow tube, during the drawing process or after the drawing, and is left at a predetermined position in the ground. In this case, if the release action is not performed properly,
The water-permeable cylinder is displaced and does not cover the outer periphery of the sand pile corresponding to the target ultra-soft layer in the ground, so that the designed improvement effect cannot be obtained.

[Problems to be Solved by the Invention] By the way, the connection and holding of the water permeable tube to the guide tube are pulled downward by the impact of the sand injected into the hollow tube or the like, so that the water permeable tube can sufficiently withstand these external forces. It must be a strong connection holding means, and it is necessary to reliably release the holding of the water-permeable cylinder during the construction process.

From this point of view, various attachment / detachment means have been developed as exemplified in Japanese Patent Application Laid-Open No. 60-242213 to satisfy the above conflicting requirements at the same time.

However, since the conventional connection and holding are premised on having both the attaching and detaching means, the structure becomes complicated as a whole and the cost is increased. Further, when the connection supporting force is set to be large, there is a possibility that the detachment operation may not be performed as designed.

The present applicant has made improvements and studies on conventional attachment / detachment means.As a result, the connection / holding means of the water-permeable cylinder can be simplified by being configured to be detachable regardless of the holding force for attaching the water-permeable cylinder, and It has been found that the connection and holding can be released easily and reliably, and the present invention has been achieved.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a hollow pipe for sand pile formation, a guide pipe provided in the hollow pipe and provided movably in a longitudinal direction, A water permeable cylinder connected to and held by the guide pipe in a suspended state, wherein the hollow pipe penetrates into the ground, sand is charged into the inside, and then the hollow pipe is pulled out, so that the outer periphery is formed by the water permeable cylinder. In the method of forming a partially covered sand pile for partially covering a sand pile, a cutting means attached to the hollow pipe or the guide pipe is provided, and a vicinity of a mounting base of a water-permeable cylinder connected and held to the guide pipe is provided. In addition, it is characterized in that the guide tube is cut by the action of the cutting means irrespective of the holding force for connecting and holding the water permeable tube to release the holding of the water permeable tube.

[Operation] According to the above configuration, the vicinity of the mounting base of the water-permeable cylinder is cut by the cutting means, and the connection and holding thereof are released.

Thus, in the present invention, by the cutting means provided independently of the connection and holding means of the water-permeable cylinder to the guide tube,
Since the connection base is released by cutting the vicinity of the mounting base of the water-permeable cylinder, the connection holding means can be simplified and the holding strength can be easily enhanced, and at the same time, the connection-maintenance of the water-permeable cylinder can be reliably released as necessary. .

Here, as the cutting means of the present invention, in addition to cutting with a blade, a method of cutting by burning with electric heat, burning gasoline or the like, a method of melting only a predetermined portion and cutting, and the like are also included.

Example An example of the present invention will be described below with reference to the drawings.

1 (a) to 1 (d) are schematic views showing construction steps in a partially covered sand pile forming method to which the present invention is applied. In addition, this embodiment assumes that the seabed ground is improved.

The seafloor ground shown in the figure shows the depths and thicknesses of the ultra-soft layer B with weak binding force, such as silt, facing the seawater A and the soft layer C located below the ultra-soft layer B by the preliminary survey. Etc. are known. At the time of implementation, for example, the driving depth of the hollow tube 1, the holding position of the guide tube 2 movably provided in the hollow tube 1, the length of the water-permeable tube 3, the hopper in the hollow tube 1 Construction design such as the total amount of sand input from 4 is performed.

In the partially covered sand pile forming method, first, as shown in FIG. 3A, a water-permeable cylinder 3 formed longer by a predetermined dimension than the thickness of the ultra-soft layer B is drawn out from the lower end of the hollow tube 1 so as to be freely rolled up. It is firmly attached to the guide tube 2 by the connection holding means 5.

Then, by driving the winding device 6 to lift the guide tube 2 via the wire 7, the water-permeable tube 3 is held in a predetermined position in the hollow tube 1 in a suspended state.

Next, as shown in FIG. 2B, the hollow pipe 1 is lowered into the seawater A and penetrates into the super soft layer B and the soft layer C. In this state, the water permeable cylinder 3 is located substantially at the corresponding portion of the super soft layer B.

The sand is usually charged in a process in which the hollow tube 1 penetrates to the pile bottom depth, and is filled in the hollow tube 1 and the water-permeable tube 3. (In practice, it is conceivable that, due to the introduction of the sand, the water-permeable cylinder 3 may be pulled downward and slightly moved in position. Then, the hollow tube 1 is pulled out from the soft layer C and the super soft layer B as shown in FIGS. 3 (c) and 3 (d), but immediately before shifting to this drawing operation, during the drawing process, or for a predetermined length. At the time of pulling out, the connection holding of the water permeable cylinder 3 is released by the cutting means 8.

Therefore, a partially covered sand pile 9 partially covered with the water-permeable cylinder 3 is formed in the ground. In this case, the water-permeable cylinder 3 is located at a position corresponding to a pile portion penetrating the ultra-soft layer B, and reinforces the holding force of this pile portion.

FIGS. 2 (a) and 2 (b) show the vicinity of the mounting base of the water permeable tube 3 to the guide tube 2, which will be described below with reference to FIG.

The permeable tube 3 is formed of a woven fabric, a non-woven fabric, a porous plastic, a net, or the like in a tubular shape.
3a is attached to the guide tube 2 by the connection holding means 5.

The connection holding means 5 is formed of a substantially ring-shaped fixture 17 whose diameter is reduced against the urging force.

The fixing bracket 17 winds the upper end portion 3a of the water-permeable tube 3 inserted into the guide tube 2 and pushes it into the lower inner wall of the guide tube 2 against the urging force, thereby guiding as shown in FIG. Permeable cylinder 3 between the lower inner wall of pipe 2
The upper end portion 3a is tightly tightly attached to connect the water permeable tube 3 to the guide tube 2.

The connection holding of the water-permeable cylinder 3 is released by the cutting means 8 before the hollow tube 1 penetrated to the predetermined depth is drawn out or in the drawing process as described above. The cutting means 8 comprises a heating unit 10 integrally connected to the lower part of the guide tube 2 and heats and cuts the vicinity of the mounting base of the water-permeable tube 3.

That is, the guide tube 2 is made of a non-conductive material, and includes a plurality of brackets 2a provided on the inner peripheral wall and a heating unit 10 provided below the guide tube 2.

The bracket 2 a is joined to a connector 11 provided at the lower end of the wire 7 via a rope 12, and suspends the guide tube 2 at the lower end of the wire 7.

The heating section 10 has an outer wall covered with an insulating layer, and has a built-in heating element (not shown). As shown in FIG. In this case, the power source can be that of the winding device 6, and the lead wire 13 is the wire 7 and the rope 12
Along the lower side of the guide tube 2 and is connected to the heating element through the wall of the guide tube 2. The power of the power source is set according to the material of the water-permeable cylinder 3 to be used and the like, and power can be supplied to the heating element via the switch operation unit.

Thus, in the present invention, by providing the cutting means 8 independently of the connection and holding means 5, the connection and holding of the water permeable cylinder 3 can be easily and reliably released as needed. Moreover, since the connecting and holding means 5 does not need to be a detachable means as in the related art, the selection range is widened, and simplification and holding strength can be easily enhanced.

FIGS. 3A and 3B schematically show modified examples of the cutting means and the connection holding means.

The cutting means 18 shown in the figure has a cutting blade 18a internally provided so as to be able to protrude and retract from a cylindrical body provided at the lower end of the hollow tube 1, and the cutting blade 18a is protruded and retracted by a suitable driving means such as a cylinder. Then, it is configured to cut the vicinity of the mounting base of the water-permeable cylinder 3.

In this case, the cutting blade 18a is protruded in the process of (d) of FIG. 1, for example, and cuts a part near the mounting base of the water-permeable cylinder 3 as shown in (a) of FIG.

Then, by further pulling up the hollow pipe 1 from this state, the water-permeable cylinder 3 receives resistance such as earth pressure of the super soft layer B, and is forced from the cut portion to the entire circumference as shown in FIG. Is severely dissected.

Further, the connection holding means 15 in the figure comprises a substantially ring-shaped fixing bracket 16 whose diameter is freely reduced.

The fixing bracket 16 is fitted into a guide groove provided on the outer periphery of the lower part of the guide tube 2 via the upper end 3a of the water-permeable tube 3, and joins the ring-shaped both ends while pulling them. This allows
The water permeable tube 3 is located in the guide groove and is fastened to the guide tube 2 by a fixing bracket 16 to be connected and held.

Thus, the connection holding means 5, 15 of the present invention and the cutting means 8,
18 can be variously deformed, and the cutting means 8 is connected to the guide tube 2.
In addition to being disposed in the hollow tube 1, it can be disposed.

In addition, the partially covered sand pile formation method of the present invention is not limited to seabed ground improvement as in the embodiment, but can be similarly applied to land ground improvement.

[Effects of the Invention] As described above, in the partially covered sand pile forming method according to the present invention, cutting means is provided independently of the connecting and holding means of the water permeable cylinder to the guide pipe, and the vicinity of the mounting base of the water permeable cylinder is cut. Therefore, the connection holding means can be simplified and the holding strength can be easily enhanced. At the same time, the connection holding of the water-permeable cylinder can be easily and reliably released as required.

Therefore, the method of the present invention does not impair the economy as a whole, the release action for the connection and holding of the water-permeable cylinder is performed accurately, and there is no danger that the water-permeable cylinder is displaced. The reliability of the construction method can be further improved.

[Brief description of the drawings]

FIGS. 1 (a) to 1 (d) are schematic views showing construction steps in a partially covered sand pile forming method to which the present invention is applied, and FIGS. 2 (a) and 2 (b) are views showing a vicinity of a base of a water-permeable cylinder. FIG. 3 is a sectional view of a main part showing another example of a connecting and holding and cutting means for the water-permeable cylinder. DESCRIPTION OF SYMBOLS 1 ... Hollow pipe 2 ... Guide pipe 3 ... Permeable cylinder 5,15 ... Connection holding means 8,18 ... Cutting means B ... Super soft layer C ... Soft ground layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-226915 (JP, A) JP-A-63-97709 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E02D 3/10 104

Claims (1)

(57) [Claims] 1. A hollow pipe for forming a sand pile, a guide pipe provided in the hollow pipe so as to be movable in a longitudinal direction, and a water-permeable cylinder connected to and held by the guide pipe in a suspended state. In the partially covered sand pile forming method, the hollow pipe is penetrated into the ground and sand is charged into the ground, and then the hollow pipe is pulled out. A cutting means attached to the hollow tube or the guide tube, and a vicinity of a mounting base of the water permeable tube connected and held to the guide tube, and a holding force for connecting and holding the water permeable tube to the guide tube. Irrespective of the above, the cutting means is cut by the action of the cutting means to release the holding of the water permeable cylinder, and the partially covered sand pile forming method is provided.