JPH0723611B2 - Ground improvement method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ground improvement method for removing water from soft ground having a high water content to increase the compressive strength of the ground.

<Prior Art> Soft ground formed from silt or clay contains a large amount of water between soil particles, and the ground has a significantly low compressive strength.

Therefore, it is necessary to eliminate the water existing between the soil particles and improve the compressive strength of the ground.

As a conventional method for improving soft ground, a natural well that has a higher permeability than soft ground, or an artificial permeable layer formed by depositing gravel or sand, has a deep well and a higher permeability than soft ground. There is a technique in which water-permeable columns are brought into contact with each other and the water in the soft ground is discharged through the water-permeable columns and the water-permeable layer (Japanese Patent Laid-Open No. 52-113009).

<Problems to be Solved by the Present Invention> The conventional soft ground improvement method described above has the following problems.

<B> When using the natural permeable layer of the prior art, the way the natural permeable layer exists in the soft ground may be intermittent or smaller than the scale of ground improvement. It may be difficult to reliably improve the entire range of ground improvement.

<B> In addition, since the natural permeable layer has a different water permeability depending on the location, if the water permeability is not so large, it may cause a decrease in drainage capacity.

<C> Furthermore, when the natural permeable layer exists deep in the soft ground, it is necessary to excessively excavate wells and permeable columns to the extent where ground improvement is not necessary, resulting in an increase in construction period and cost. .

<D> Next, when the artificial permeable layer of the prior art is used, since the permeable layer is formed by depositing gravel, sand, etc. in the soft ground, the construction becomes large-scale and the construction period and cost increase. Will be invited.

<Purpose of the present invention> The present invention has been made to solve the above problems, the improvement of soft soil having a high water content, easy, quick,
An object of the present invention is to provide a method for improving soft ground that can be reliably and economically performed.

<Structure of the Present Invention> An embodiment of the present invention will be described below with reference to the drawings.

<A> Installation of water-permeable pipe The water-permeable pipe 2 is installed in the soft ground 1 in an arc shape from the ground surface.

The water permeable pipe 2 has a greater water permeability than the surrounding soft ground 1.

First, as shown in FIG. 2, the installation method of the water permeable pipe 2 is as follows.
A rod 22 formed with a predetermined bending rate using a drill machine 21 or the like.
While connecting, start piercing in the soft ground 1 downward from the ground surface.

The drilling direction of the rod 22 is such that when the drilling reaches the center of a predetermined arc, the direction is changed from downward to upward.
It is set in advance by using a known universal joint.

Then, the drilling work is continued until the tip of the rod 22 reaches the ground surface at a point opposite to the installation point of the drill machine 21.

When the tip of the piercing rod 22 is exposed on the opposite surface, the drill bit 23 at the tip of the rod 22 is removed.

Then, as shown in FIG. 3, the water-permeable pipe 2 having high water permeability is attached to the tip of the rod 22, and the water-permeable pipe 2 is pulled into the ground while retracting the rod 22, and the arc-shaped water-permeable pipe 2 is softened. Lay in 1.

<B> Excavation of a well It reaches the water permeable pipe 2 installed in the soft ground 1.

The well 3 is constructed by a deep well method or the like, and a steel pipe having water passage holes at predetermined positions, or a steel pipe having a filter wound around the peripheral surface thereof can be used.

A pump 4 is installed at a portion of the bottom of the well 3 that comes into contact with the water permeable pipe 2, and a drainage pipe 41 is piped from the pump 4 to the ground through the well 3.

<C> Placing of vertical water collecting columns The vertical water collecting columns 5 are composed of conventionally used sand columns, paper columns, etc., and their water permeability is larger than that of the soft ground 1 like the water permeable pipe 2. Must be one.

A predetermined number of the vertical water collecting columns 5 are driven vertically until they reach the water permeable pipe 2.

<D> Draining Work Next, the draining work of water in the soft ground 1 will be described.

As shown in FIG. 1, the water level in the soft ground 1 is the height of L1.

(1) Lowering of water level in well and vertical water collecting column First, the pump 4 is operated to discharge the water in the well 3 and the vertical water collecting column 5 to lower the water level to, for example, the height of L2.

At this time, since the water permeability of the well 3, the vertical water collecting column 5, and the water permeable pipe 2 is larger than that of the surrounding soft ground 1, the water levels in the well 3 and the vertical water collecting column 5 easily drop.

When the water level in the well 3 and the vertical water collecting column 5 decreases to L2, the water pressure in the vertical water collecting column 5 between L1 and L2 becomes lower than that of the surrounding soft ground 1.

(2) Drainage to the ground When the water pressure in the vertical water collecting column 5 decreases as described above, the water in the surrounding soft ground 1 moves toward the vertical water collecting column 5,
It is absorbed in the vertical water collecting column 5.

The water thus collected in the vertical water collecting column 5 is forcibly lowered in the direction of gravity by the suction force of the pump 4 transmitted through the water permeable pipe 2.

The dropped water passes through the water permeable pipe 2, is sucked by the pump 4, and is discharged to the ground through the drainage pipe 41.

The above work can be continuously repeated to remove the water in the soft ground 1 to surely achieve the ground improvement.

<Effects of the Present Invention> Since the present invention has been described above, the following effects can be expected.

<a> Since the water-permeable pipe can be installed continuously and at any scale, the entire range of ground improvement can be surely improved.

<B> Since the water permeability of the water permeable pipe can be arbitrarily selected, a constant high drainage force can be obtained and the construction rate can be improved.

<C> Since a water-permeable pipe can be installed from the ground surface to any depth, it is not necessary to excavate wells or water-permeable columns more than necessary, and the construction period and cost can be reduced.

<D> Since the water-permeable pipe can be installed easily and quickly by the method of propelling the rod, the construction period and cost can be significantly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1: Illustration of the overall construction of an embodiment of the present invention FIG. 2: Illustration of the installation method of a water-permeable pipe FIG. 3: Illustration of the installation method of a water-permeable pipe

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Claims (1)

[Claims] 1. A water-permeable pipe is installed in an arc shape from the ground surface to the soft ground, a well is excavated to reach the water-permeable pipe, and a vertical water collecting column having a higher permeability than the soft ground reaches the water-permeable pipe. The ground improvement method is constructed so that water in soft ground is collected in vertical water collecting columns to flow into the permeable pipe, and the water collected in the permeable pipe is pumped out of the well and discharged.