JPH11247178A - Structure of permeable improvement ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high permeable improvement ground excellent in execution by irregularly laying high permeable material agitated and mixed with ground between the soil particles of an improvement body and providing the improvement body with permeability through the high permeable material. SOLUTION: High permeable material 2 is agitated and mixed with jobsite soil and sand 1 to discontinuously (irregularly) form a group of improvement parts 3, so that a columnar improvement body 4 having permeability as a whole is obtained. In order to give permeability, continuity is not possessed in the high permeable material 2. The high permeable material 2 is preferably properly used by short and long periods for maintaining permeable function. Agitating wings 6, 7 and a jetting opening 8 are multistagedly formed on the edge of a hollow rod 5, and after the rod 5 is rotated, the ground is agitated down to a prescribed depth and loosed, the high permeable material 2 is pumped by air from the base end of the rod 5 when the rod 5 is pulled while being reversely rotated. Agitation is performed with the jobsite soil and sand 1, and mixing is irregularly performed between the soil particles of the jobsite soil and sand 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a ground with improved permeability, which can be applied to a drain method, a ridge method, a ground improvement method, a control of groundwater flow in various works, and the like.

[0002]

2. Description of the Related Art In a vertical drain construction method in which an artificial drainage channel (drain) is formed in the ground, and pore water in the ground is drained to improve the consolidation, the drain material constituting the drainage channel extends over the entire length. It is important to have continuity throughout and high water permeability.

[0003]

The above conventional drain technology has the following problems. <B> If the drain material breaks or becomes clogged and loses continuity, the function as the drain material is reduced by half or lost. Therefore, careful handling and construction are required, and the construction period tends to be prolonged. <B> There are various drain materials such as paper drain and plastic drain, but the cost increases in proportion to the water permeability of the drain material. <C> In the case of sand drains, gravel drains, etc., the problem of post-processing of excavated earth and sand generated in large quantities remains. <D> When used in the ground improvement method, it can be expected to enhance the bearing capacity of the ground, but it tends to hinder the groundwater flow,
It is technically difficult to satisfy both of these.

The present invention has been made in view of the above points, and an object of the present invention is to provide a technique for constructing a ground with improved permeability, which is capable of obtaining an improved ground having excellent workability and high water permeability. Is to do.

[0005]

The invention according to claim 1 is
A highly permeable material mixed and stirred into the ground to be improved is irregularly interposed between the soil particles of the improved body, and the improved body has water permeability through the highly permeable material. is there. The invention according to claim 2 is the structure of the ground with improved permeability according to claim 1, wherein the improved body is a columnar body or a columnar body. The invention according to claim 3 is the structure of the ground with improved permeability according to claim 1 or 2, wherein the highly permeable material is a porous carrier having strength. The invention according to claim 4 is the structure of the ground with improved permeability according to claim 1 or 2, wherein the highly permeable material is an ecologically degradable material. The invention according to claim 5 is the structure of the ground with improved permeability according to claim 1 or 2, wherein the improved body is formed at the groundwater position on the ground.

[0006]

Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

<A> Structure of the ground with improved permeability The basic idea of the drain construction method so far is that the drain material has continuous water permeability. On the other hand, the present invention imparts a constant water permeability throughout the improvement range while exhibiting a structure in which water permeability is discontinuous microscopically. That is, as shown in FIG. 1, a highly permeable material 2 is stirred and mixed with on-site earth and sand 1 to form a group of improved portions 3 discontinuously (irregularly), thereby forming a columnar improved body 4 having water permeability as a whole. This is different from the conventional drain technology in that the highly water-permeable material 2 is not provided with continuity in order to impart water permeability.

In FIG. 1, the improved body 4 is deformed and shown as a large lump to facilitate understanding of the invention. However, as shown in an enlarged view in FIG. The lumps of the highly permeable material 2 are only mixed irregularly, and the earth and sand do not become lumps.

<B> Highly water-permeable material As the highly water-permeable material 2, various materials having water permeability can be used. It is desirable to use differently according to the length of the period for maintaining the water permeability. When water permeability is expected for a long period of time, a porous carrier that has a small amount of clogging, such as pumice stone, cork material, and a porous material that can be artificially manufactured, and has sufficient strength to prevent deformation is suitable. If an increase in strong soil is not expected, low-strength materials can be used.

[0010] In addition, when water permeability is expected in the short term,
For example, an eco-friendly disintegrating material that does not matter the strength of shells, straws and the like can be used. The above materials are used as crushed granules by being crushed to about 4 to 30 mm in addition to being crushed into granules or powder.

As the other highly water-permeable material 2, a fibrous material such as glass fiber, zeolite, perlite (foam of glass), charcoal, vinyl fiber or the like which forcibly forms a water channel in the ground is used. Is also possible. The above-mentioned highly water-permeable material 2 may be used alone or in combination of two or more kinds, and the amount of the mixture differs depending on the properties of the local ground and the used highly-permeable material 2.

<C> Mixing means of high water permeable material The above high water permeable material 2 is mixed by mixing and mixing local soil and sand. The stirring and mixing device illustrated in FIGS. 1 and 2 will be described.
And forming the injection port 8, and after stirring the ground to a predetermined depth while rotating the rod 5 to loosen the ground, when pulling up the rod 5 while reversing it, from the base end of the rod 5 The highly permeable material 2 is sent by air pressure. The highly permeable material 2 is injected from the injection port 8 to be agitated with the on-site earth and sand 1 and mixed irregularly between the soil particles of the on-site earth and sand 1.

In FIG. 1, reference numeral 9 denotes a spout prevention cover which collects and exhausts air used for pressure-feeding the highly water-permeable material 2. In FIG. 2, reference numeral 10 denotes a short blade for air recovery protruding from the peripheral surface of the rod 5, and a space for discharging the air injected from the injection port 8 to the ground is a blade for pushing back the earth and sand around the rod 5. is there.

<D> Form of Improved Body The improved body 4 has a form in which it is constructed in a columnar form as shown in FIG. 4 with an interval, and a form in which it is formed in a column form as shown in FIG. Whether or not to use the form is determined in consideration of the purpose of improvement, the scope of improvement, and the like.

<E> Principle of Water Permeation The improved body 4 in which the highly permeable material 2 is mixed irregularly in the local soil 1 has good water permeability, and the strength and the supporting force of the improved body 4 are increased as follows. For reasons.

[Water Permeability Principle] It is clear that the high water permeability is high in this material by stirring and mixing the highly water permeable material in the ground. By arranging the highly permeable materials irregularly, the average permeable distance of the low permeable ground decreases. FIG. 6 shows a serial model of this. From the figure, if the water permeability distance before the improvement is L and the water permeability distance after the improvement is Li, the relationship of the following equation 1 is obtained, and therefore, it can be expected that the water permeability distance is reduced.

[0017]

(Equation 1)

Further, by using a highly water-permeable material having strength, soft earth and sand can be replaced with a good material, and the supporting force increases. In addition, it is possible to expect a compaction effect by mixing and an increase in strength due to a friction force between the ground and the permeable material being larger than a friction between the grounds, depending on the characteristics of the ground.

[Mechanism of Demonstrating Water Permeability] A mechanism of exhibiting high water permeability by improving the water permeable ground using the above-described principle of water permeability will be described. The model of FIG. 7 in which groundwater flows from left to right in the drawing will be described. In the case of no improvement, assuming that the head on the A side is PA, the head at point B is PB, the distance between points A and B is L, and the velocity of groundwater flowing through the ground is v, the permeability k is Equation 2

[0020]

(Equation 2)

Before the improvement, if the conditions at the boundary are the same, there is no change in the velocity of the groundwater in the ground. However, since the permeability kp is extremely large in the improved Kaseno improved body, the flow velocity vp is the average flow velocity. larger than v. That is, the average flow velocity in the improved ground is v <
_vave (average water flow velocity) <vp. Therefore, the average hydraulic conductivity is also improved as k <k _ave (average hydraulic conductivity) <kp. The water permeability depends on the arrangement of the improved body and the improvement ratio, but has been confirmed by the improvement effect described later (paragraph 0018).

[Reason for Increasing Ground Strength and Supporting Capacity] When a material having strength is used as the highly permeable material 2,
A strength corresponding to the amount of the highly permeable material 2 interposed between the soil particles is given to the ground. Also, as the strength of the ground increases, the supporting force naturally increases. The above is attributable to the strength of the highly permeable material 2. However, the excessive pore water between the soil grains is drained by the drainage effect of the porous highly permeable material 2, and the strength and support by promoting the compaction of the ground. We can expect the effect of increasing power.

<F> Improvement Effect Next, the improvement of water permeability is confirmed by numerical calculation using a simple model. The analysis used steady flow analysis (plaxis).

FIG. 8 shows an analysis model. Condition data is
The hydraulic conductivity (cm / s) of the ground is 1.0 × 10 ⁻⁶ , and the hydraulic conductivity (cm / s) of the improved body is 1.0 × 10 ⁻¹ . As the analysis cases, two cases were implemented: a state in which the improved ranges were randomly arranged in the horizontal direction (case 1) and a state in which the improved ranges were regularly arranged (case 2).

FIG. 9 shows an example of an analysis case in which the improvement rate (volume of improvement range / total volume) is 60%. ,

FIG. 10 shows the relationship between the improvement rate and the apparent hydraulic conductivity (the hydraulic conductivity obtained by calculating backward from the amount of emissions obtained from the analysis). According to FIG. 10, it can be expected that the apparent permeability increases by 3 to 4 orders at the improvement rate of 60%. In this analysis model, a ground of 1.0 × 10 ⁻⁶ cm / s was improved by 60%.
%, The hydraulic conductivity of a common drain (1.
0 × 10 ⁻³ cm / s).

FIG. 11 is a model diagram showing the change of the infiltrated surface when the highly permeable material 2 is mixed over a wide area in the ground near the slope 11, which is improved with respect to the infiltrated surface L1 before the improvement. The later infiltration surface L2 is greatly reduced, and the earth pressure acting on the slope 11 is reduced. The improvement effect at this time was confirmed by numerical analysis. Based on the analysis model of FIG. 12, the analysis result of the ground before improvement is shown in FIG. 13, and the analysis result after improvement is shown in FIG. This example can also be used as an auxiliary construction method for mountain stays.

[0028]

Second Embodiment FIGS. 15 and 16 show another embodiment in which the ground improvement position is adjusted to the groundwater level. FIG. 15 shows a case where the improved body 4 is constructed at a fixed distance, and FIG. 16 shows a case where the improved body 4 is constructed by joining.
In any case, it is important that the improvement range 4a of the improvement body 4 be located at the height of the groundwater. In the case of FIG. 15, the groundwater passes through the local soil and the improvement area 4a located between the adjacent improved bodies 4, and the presence of the improved body 4 does not obstruct the flow of the groundwater. In the case of FIG. 16, since the improved range 4a has continuity in the horizontal direction, the groundwater flows more easily than in FIG.

[0029]

Third Embodiment FIG. 17 shows an improved body 4 having high water permeability.
Another embodiment in which is applied to rainwater recharge is shown. In this example, the improved body 4 in which a highly permeable material is mixed over a wide range into the poorly permeable ground 12 is constructed, and the range of the improved body 4 imparted with high permeability promotes ground recharge of rainwater. In this example, there is an advantage that the load on the natural environment due to the development can be reduced by applying the invention to a direct foundation board of a sidewalk, a road, a railroad or the like having a porous structure.

[0030]

As described above, the present invention has the following effects. <A> An improved body having high water permeability (improved ground) can be obtained only by stirring and mixing the highly permeable material in the local ground. <B> If a material having strength is used for the highly permeable material,
It is possible to prevent the groundwater flow from being disturbed while securing an increase in ground strength. <C> Compared with the conventional drain technology that has a basic idea that water permeability is continuous, the present invention only needs to provide discontinuous water permeability, and it is possible to reduce the construction cost and significantly shorten the construction period . <D> The amount of earth removal can be reduced only by stirring and mixing the local ground. Therefore, the problem of post-processing of excavated earth and sand is reduced. <E> It can be used in many fields such as drain material method, mountain retaining method, groundwater control, and groundwater recharge, and is highly versatile.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a stirring and mixing device.

FIG. 3 is an enlarged model diagram of the ground constituting the improved body.

FIG. 4 is a cross-sectional view showing a form of forming an improved body.

FIG. 5 is a cross-sectional view showing another form of improvement.

FIG. 6 is a series model diagram for explaining the principle of water permeability.

FIG. 7 is a model diagram for explaining a mechanism of exhibiting water permeability.

FIG. 8 is an analysis model diagram for verifying the improvement effect.

FIG. 9 is an explanatory diagram of an analysis case with an improvement rate of 60%.

FIG. 10 is an explanatory diagram of a relationship between an improvement rate and an apparent hydraulic conductivity.

FIG. 11 is a model diagram showing a change in water head when the ground near the slope is improved.

FIG. 12 is an analysis model diagram of FIG. 11;

FIG. 13 is an explanatory diagram of an analysis result showing a head before the improvement.

FIG. 14 is an explanatory diagram of an analysis result showing a head after improvement.

FIG. 15 is an explanatory view of another embodiment in which the ground improvement position is adjusted to the position of the groundwater level.

FIG. 16 is an explanatory view of another embodiment in which the ground improvement position is adjusted to the position of the groundwater level.

FIG. 17 is an explanatory view of another embodiment applied to rainwater recharge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Local soil 2 High permeable material 3 Improvement part 4 Improvement body (improved permeability ground) 5 Rod 6,7 Stirrer blade 8 Injection port 9 Ejection prevention cover 10 Short blade 11 Slope 12 Impervious ground

Claims (5)

[Claims] 1. A highly permeable material, which is stirred and mixed with the ground to be improved, is irregularly interposed between the soil particles of the improved body, and the improved body has water permeability through the highly permeable material. Improved ground structure. 2. The improvement body is a columnar body or a columnar body.
The structure of the ground with improved permeability according to claim 1. 3. The structure of the ground with improved permeability according to claim 1, wherein the highly water-permeable material is a porous carrier having strength. 4. The structure of a ground with improved permeability according to claim 1, wherein the highly permeable material is an ecologically disintegrating material. 5. The structure of the ground with improved permeability according to claim 1, wherein the improved body is formed so as to be aligned with the groundwater position on the ground.