JP7007054B2 - How to build foundation piles in the ground including contaminated soil layer - Google Patents

Description

The present invention relates to a method for constructing a foundation pile in a ground including a contaminated soil layer in which a pile hole is excavated from the ground and a structure such as a ready-made pile or a reinforcing bar cage is buried in the ground including the contaminated soil layer.

If there is a contaminated layer contaminated with oil, etc., construction work that does not emit pollutants different from the normal site is required. Excavated soil discharged from the plane of the contaminated area (regardless of depth) is regarded as contaminated soil, separated from ordinary industrial waste (excavated soil containing cement milk, etc.) and treated strictly. Is required.

In the construction of the contaminated area, for example, with the construction equipment, the cleaning material is poured into the ground to the vicinity of the bottom of the contaminated layer, excavated and stirred (cleaning material mixing step), and then from the vicinity of the bottom of the contaminated layer from the construction equipment. A construction method has been proposed in which water is discharged to raise oil on the ground surface (cleaning step) and the construction equipment is pulled up to create a solidified pile (Patent Document 1). In this case, the cleaning material can act on oil to form micelles that can be adsorbed, decomposed or dissolved insoluble oil, and is a builder of soaps, surfactants, alkaline materials, enzymes, and lye containing alkaline. Etc., and it is said that these can be used alone or in combination of two or more.

In addition, a pile construction method in which the casing is press-fitted to the stratum below the contaminated soil layer including the contaminated soil, the earth and sand in the casing are discharged, the casing is filled with a filler to construct a pile, and then the casing is pulled out. Has been proposed (Patent Document 2). In this case, the lower end of the casing should reach the silt layer below the contaminated soil layer, and the soil containing the contaminated soil in the casing should be discharged to the ground surface with a screw rod to be properly used as waste. It is processed.

JP-A-2002-192142 Japanese Unexamined Patent Publication No. 2012-112163

In the first technique, the oil content in the excavated hole can be treated, but the oil content oozing out from the hole wall into the hole cannot be considered. Further, in the second method, it takes time and ingenuity to completely remove the earth and sand including the contaminated soil in the casing to the ground. Further, when the silt layer is relatively deep, the device for pulling out the casing (rotating device, heavy machine for taking reaction force, etc.) becomes huge, which requires a cost.

In the present invention, the upper pile hole is once formed in the ground including the contaminated soil layer to a depth that penetrates the contaminated soil layer, the contaminated soil in the upper pile hole is discharged, and then the pile hole is formed following the upper pile hole. Since it is excavated, the above-mentioned problems have been solved.

That is, the present invention is a method for constructing a foundation pile in the ground including the contaminated soil layer, which is characterized by excavating as follows when constructing the foundation pile in the ground having the contaminated soil layer near the ground surface.
(1) From the ground, with an excavation rod equipped with a discharge port and an excavation blade at the excavation head at the lower end , water or excavation liquid is injected and excavated while kneading the pile hole wall of the contaminated soil layer to the contaminated soil . If the excavation blade of the excavation rod penetrates the contaminated soil layer, an upper pile hole is formed, the excavation is temporarily stopped, and the excavation rod is moved while preventing the water in the layer from seeping out . It is pulled up to the ground and the lower part of the excavation rod is cleaned or washed .
(2) Using the excavation rod, at the same time as the step of (1) above, or by using another means, the excavation surplus soil containing the contaminated soil in the upper pile hole is discharged to the ground.
(3) The tip end side of the excavation rod is inserted into the upper pile hole, and excavation liquid, water, etc. are injected into the pile hole to knead the pile hole wall of the contaminated soil layer and further downward. And excavate.
(4) The pile hole is constructed by excavating to the support layer with the excavation rod, and the pile hole bottom is injected with a water-hard material from the discharge port into the pile hole filled with water or excavated mud. Then , the excavation rod is pulled up to the ground.
(5) While pulling the excavation rod to the ground or after pulling the excavation rod to the ground , the structure is buried to construct a foundation pile.

Further, in the above, it is a method of constructing a foundation pile in the ground including a contaminated soil layer, which is characterized by excavating as follows.
(1) In the ground where the contaminated soil layer is formed on the impermeable soil layer, if the excavation blade of the excavation rod penetrates the contaminated soil layer and reaches the impermeable soil layer, the upper pile hole Is formed, excavation is temporarily stopped, the excavation rod is pulled up to the ground, and the excavated residual soil in the upper pile hole is discharged from the upper pile hole.

Further, in the above, the method for constructing a foundation pile in the ground including the contaminated soil layer according to claim 1, wherein the excavation is performed as follows.
(1) Form a Kamaba pit in advance on the site or in the vicinity.
(2) Once the upper pile hole is formed, the excavated soil in the upper pile hole is discharged to the ground and moved into the Kamaba pit.
(3) The insolubilizing material is put into the Kamaba pit, and the mud cake is discharged from the Kamaba pit as a mud cake by insolubilizing the excavated soil while confirming the elution of pollutants .

Further, in the above, the excavation rod is a method for constructing a foundation pile in the ground including a contaminated soil layer in which a kneaded drum is formed directly above the excavation head.

The contaminated soil layer in the above is, for example, a soil layer containing a certain amount of pollutants (heavy metals, organic solvents, pesticides, oils, and other substances that affect the natural environment and human health / life). say.

The impermeable stratum in the above means a stratum or a bedrock having a small gap in the rock / stratum and having poor permeability.

The hydraulic material in the above usually refers to cement milk or concrete having various concentrations, but also includes a material equivalent to cement milk.

In the present invention, after excavation of a pile hole penetrates a contaminated soil layer and reaches an impermeable layer, the excavation rod is once pulled up to the ground, the inside of the excavation hole is cleaned, excavation is continued again, and the excavation rod is kneaded. Since the penetrating part of the contaminated soil layer is kneaded by the attachment means, the excavation rod excavated from the contaminated soil layer can be washed on the ground, and the components of the contaminated soil can be prevented from entering the pile hole from the kneaded contaminated soil layer. can. Therefore, it is possible to construct a foundation pile by excavating a pile hole excluding the components of the contaminated soil layer by a simple method and surely.

(A)-(e) It is a vertical sectional view which shows the construction method of the foundation pile of this invention, and shows the process up to the construction of the upper pile hole. (A) to (f) are vertical cross-sectional views showing the method of constructing the foundation pile of the present invention, and show the process until the excavation of the pile hole is completed. (A)-(c) The vertical sectional view which shows the construction method of the foundation pile of this invention shows the process of burying a ready-made pile.

1. 1. Construction ground

(1) The ground on which the foundation pile is constructed has a contaminated soil layer 12 having a thickness of H0 from the ground (ground surface) 11, and a silt layer (impermeable layer) 12 is continuously formed under the contaminated soil layer 12. (Fig. 1 (a)). H0 is, for example, about 5.5 m, and the surrounding ground becomes the contaminated layer 12 due to the pollutants in the contaminated layer 12, and the silt layer 13 keeps the contamination further downward. Further below the silt layer 13, a hard support layer (supporting ground) 15 capable of supporting the tip support pile is formed through the intermediate layer 14.

(2) The contaminated layer 12 refers to the soil in which heavy metals and the like are contained in the soil as described above.
Preliminary surveys will be conducted according to the usual statutory content. For example, the site site is divided into grids of a predetermined range (for example, 8 m square), and a boring survey is conducted to obtain information on the plane and depth containing contaminants above the normal standard value. It is certified as a pollution range, and in particular, the amount of soil elution and soil content of lead (Pb), arsenic (As), cyanide (CN), fluorine (F), etc. are confirmed.

2. 2. Drilling rod 1

(1) The excavation rod 1 used for carrying out the present invention is configured by connecting unit rods having a predetermined length up and down and connecting an excavation head 5 at the lowermost end (FIG. 1A). The unit rod is provided with kneading drums 2, 2 and stirring bars 4, 4 according to the diameter of the excavation hole to be excavated. Further, the excavation head 5 is provided with fixed excavation blades 7 and 7 at the lower end of the head main body 6 having a connecting portion connected to the lower end of the unit rod, and the excavation arm 8 swinging around the swing axis on the head main body 6. The base end of 8 is attached. Further, moving excavation blades 9 and 9 are attached to the tips of the excavation arms 8 (FIG. 1 (a)).

(2) The kneading drum 2 is a kneading plate having a phase (convex outward) in which the pile hole wall can be kneaded along the shape of the pile hole wall to be excavated, or a vertical direction (vertical direction) kneading. It is also possible to have a divided barrel-shaped structure having a shape having the kneading means 3 and 3 such as a bar (a structure in which rods are vertically arranged).
Further, a discharge port is provided at the lower end (or upper end) of the head body 6 of the excavation head 5 (not shown). Water, excavation liquid (bentonite liquid), and the like can be supplied from the plant and the reservoir layer 11 above the ground to the liquid passage in the excavation rod (unit rod) 1 and injected into the pile hole 20 from the discharge port.
Further, the excavation head 5 operates the stopper in the same rotation direction of the excavation rod 1 (the excavation arm 8 has the same swing direction) to set the swing angle of the excavation arms 8 and 8 in the shaft excavation mode (swing). It is possible to switch between (small angle) and widened bottom excavation mode (large swing angle). Therefore, it is possible to excavate the shaft portion 22 (small diameter) and the bottom expansion portion 23 (large diameter) of the pile hole 20. It is also possible to switch the swing direction of the excavation arm 8 (rotational direction of the excavation rod 1) and change the swing angle depending on the swing direction (not shown). Further, although it is desirable to switch between the two types of excavation diameters, the excavation head 5 having another structure may be used (not shown).

3. 3. How to build foundation pile 40

(1) A hole is dug in the ground 11 at a position that does not hinder the construction of foundation piles in the site site or a site close to the site, and a Kamaba pit 36 for treating contaminated soil is formed (FIG. 1 (e)). The size of the Kamaba pit 36 is arbitrary, but it is desirable to secure at least the volume of the upper pile hole 21. Further, it is desirable that the Kamaba pit 36 is formed on the ground 11 having no contaminated soil layer or being relatively uncontaminated. If necessary, it is desirable to cover the inner surface of the Kamaba pit 37 with a waterproof sheet or the like. Further, it is desirable to form the Kamaba pits 36 at a plurality of places.

(2) Power information such as the excavation diameter of the pile hole for each depth in excavation of the pile hole, the number of rotations of the excavation rod 1, the current value required for the rotation of the excavation rod 1 and the load current value, water and excavation liquid, etc. Proceed with excavation while recording the injection amount. At this time, the power information of the pile driver such as the current value required for the rotation of the excavation rod 1 for each depth and the load current value has a high affinity with the N value for each depth calculated by the boring survey. Therefore, proceed with excavation while comparing.

(3) When the excavation rod 1 is attached to a pile driver (not shown) and the excavation rod 1 is rotated in the forward direction, the excavation arm 6 swings open in one direction, and the excavation blades 8 and 8 move. 9 and the fixed excavation blades 7 and 7 of the head body 6 start excavation from the ground 11 at the shaft portion diameter of the pile hole 20 (FIGS. 1A and 1B).
There is a contaminated soil layer 12 in the vicinity of the ground 11, and when the soil layer 12 is penetrated from the ground 11 (FIG. 1 (c)) and reaches the silt layer 13 and excavates the inside of the silt layer 13 to some extent (ground 11). From depth H0 + α), once the rotation of the excavation rod 1 is stopped (FIG. 1 (d)), the excavation rod 1 (also the excavation head 5) is pulled up onto the ground 11 to complete the excavation of the upper pile hole 21 (from to the depth H0 + α). FIG. 1 (e). That is, the bottom 21a of the lower pile hole 21 is located in the silt layer 13.
When excavating the upper pile hole 21, water is injected from the discharge port at the lower end of the head body 6 of the excavation head 5. As a result, mud is kneaded into the pile hole wall of the upper pile hole 21 with a kneading drum 2 or the like, and a film due to mud is formed on the pile hole wall (end surface 12a of the contaminated soil layer 12), and the pile hole wall (contamination). It is possible to prevent the moisture in the contaminated soil layer 12 from seeping into the upper pile hole 21 from the end surface 12a) of the soil layer 12.
Further, the portion of the lower part of the excavation rod 1 (excavation head 5 portion or the like) involved in the excavation of the contaminated soil layer can be cleaned or washed on the ground 11.

(4) Subsequently, the excavated soil 35 (including contaminated soil and some silt) in the upper pile hole 21 is discharged from the upper pile hole 21 onto the ground 11, and the excavated soil 35 is directly transferred to the Kamaba pit 36. Move (Fig. 1 (e)). Since the work of discharging the excavated soil 35 from the upper pile hole 21 is in a shallow part near the ground 11 (because the upper excavator hole 21 is shallow), it is done by heavy machinery (hydraulic excavator, power shovel, backhoe, etc.) or in a so-called place. It can be discharged by using the bucket used for the construction of the excavator. If necessary, water is subsequently poured into the upper pile hole 21 for cleaning.
In this state, the contaminated soil is almost discharged from the inside of the upper pile hole 21.

(5) At this time, the excavated soil (contaminated soil) 35 discharged from the upper pile hole 21 is insolubilized in the Kamaba pit 36 as follows (FIG. 1 (e)).
How much water should be injected and how much insolubilized cement should be injected into the excavated soil (contaminated soil) at this site to optimize the mud cake (specific gravity, hardness, cohesiveness and strength required for discharge, etc.) It is desirable to confirm in advance by a test whether it becomes (residual soil) or whether there is any elution of pollutants from the massed mud cake (insoluble residual soil).
The excavated soil is sufficiently agitated by the kneading drum of the excavation rod and the agitation bar, and the amount of injected water is controlled. Put in soil and stir to mix. Furthermore, a part of the actually formed mud cake (insolubilized residual soil) is taken out as a sample, and it is confirmed whether or not the contaminants are eluted.
In some cases, on-site construction may be carried out before the test results are obtained in advance. In this case, it is desirable to add a slightly larger amount of insolubilized cement until the test results are obtained.
Mud cakes (residual soil that has been confirmed to be safe) are treated as industrial waste containing contaminated soil by the usual method (by dumping, etc.).
For insolubilized cement, commercially available materials will be used in response to the pollutants contained, according to the conclusion of the preliminary survey.

(6) Subsequently, if the excavated soil 35 in the upper pile hole 21 is discharged (may be before the insolubilization treatment of (5) above is completed), the excavation rod 1 is again in the upper pile hole 21. (Excavation head 5) is inserted (FIG. 2A), the excavation rod 1 is rotated, and the excavation arms 8 and 8 of the excavation head 5 are similarly swung open to open the upper pile hole at the shaft diameter. From the bottom 21a (in the silt layer) of 21, the shaft portion 22 of the pile hole 20 is excavated in the silt layer 13 and the intermediate layer 14 (FIG. 2B). At this time, similarly, water is injected from the discharge port at the lower end of the excavation head 5 and excavated while kneading the mud with the kneading drums 2 and 2 on the pile hole wall in the same manner. Since the hole wall (end face 21a) is constantly kneaded with mud with the kneading drums 2 and 2, the film of the pile hole wall (end face 21a) is strengthened, and the contaminated soil layer is formed from the pile hole wall (end face 21a) of the upper pile hole 21. Moisture containing contaminants in 12 can be reliably prevented from entering the pile hole 20.

(7) When the shaft portion 22 of the pile hole 20 reaches the support layer 15 (depth H1), the excavation head 5 (excavation rod 1) is set to the expanded excavation mode, and the excavation arms 8 and 8 of the excavation head 5 are set. The excavating arms 8 and 8 maintain a large swing angle and excavate the expanded bottom portion 23 of the pile hole 20 having a larger diameter than the shaft portion 22 of the pile hole 20 by swinging the shaft portion of the pile hole larger than when excavating. (Fig. 2 (c)). If the expanded portion 23 of the pile hole 20 is excavated to a predetermined depth (depth H1 to depth H2) (FIG. 2 (d)), the bottom 24 of the pile hole 20 (bottom 24 of the expanded portion 23 of the pile hole 23). ), The excavation head 5 is positioned (FIG. 2 (d)).
Alternatively, if the shaft portion 22 of the pile hole 20 reaches the support layer 15 (depth H1), the inside of the support layer 15 is continuously excavated with the same shaft portion diameter, and the excavation is performed to a predetermined depth (H2). For example (not shown), when the excavation rod 1 is set to the enlarged excavation mode and the excavation arms 8 and 8 of the excavation head 5 are swung at a large swing angle, the excavation arms 8 and 8 maintain a large swing angle. Then, the diameter is larger than the shaft portion diameter, and the pile wall of the pile hole having the shaft portion diameter is enlarged so as to be scraped to form the expanded bottom portion 23 of the pile hole 20 at a predetermined depth (near H1 to H2) (FIG. 2). (D)). After excavating the bottom expansion portion 23 of the pile hole 20 to a predetermined depth, the excavation head 5 is similarly positioned at the bottom 24 of the pile hole 20 (bottom 24 of the bottom expansion portion 23 of the pile hole 20) (FIG. 2 (d)). ).

(8) With the excavation head 5 positioned at the bottom 24 of the pile hole 20 (bottom 24 of the expanded bottom portion 23 of the pile hole 20) (FIG. 2 (d)), the pile hole 20 (upper pile hole 21, shaft portion). 22. The inside of the expanded bottom portion 23) is filled with water (FIG. 2 (d)).
Cement milk is injected into the pile hole 20 (bottom expansion portion 23) from the bottom 24 of the pile hole 20 (bottom 24 of the bottom expansion portion 23 of the pile hole 20) from the discharge port of the excavation head 5. The cement used for this cement milk is insolubilized cement and is supplied from the ground (hereinafter the same). Normally, since cement milk has a higher specific density than water or excavated mud, the cement milk 28 collects from the bottom 24 of the pile hole 20 and is replaced with water or excavated mud, and the water or excavated mud rises upward to open the pile hole 20. Since it gradually overflows (on the ground 11), it is collected on the ground 11.
Subsequently, while injecting cement milk into the shaft portion 22 of the pile hole 20 from the discharge port of the excavation head 5 (FIG. 2 (e)), the excavation rod (excavation head) is pulled up to the ground (not shown). Therefore, water and excavation mud rise toward the ground 11 together with the excavation head 5. Similarly, the water and excavation mud that overflowed on the ground 11 are collected on the ground 11, the excavation rod 1 (excavation head 5) is pulled up on the ground 11, and the pile hole 20 is filled with cement milk 28. The excavation of the pile hole 20 is completed (FIG. 2 (f)). The upper pile hole 21 is included in the shaft portion 22 of the pile hole.
In this state, at the depth (height, near the upper pile hole 21) of the contaminated soil layer 12, the pile hole wall (end face 21a) of the contaminated soil layer 12 is kneaded as described above, and the contaminated soil layer 12 It is possible to prevent water containing contaminants from the contaminated soil layer from entering the inside of the pile hole 20 (inside the cement milk 28).
Further, in this case, the cement milk 28 to be injected can select and use the material used in the construction of a normal foundation pile according to the load (bearing capacity) required for the foundation pile (Fig.). Not shown).

(9) Subsequently, the ready-made pile 31 is lowered into the pile hole (filled with cement milk 28) 20 (FIG. 3A). At this time, the ready-made piles 31 are buried by connecting the ready-made piles having a predetermined length up and down and rotating them if necessary. Normally, the unit ready-made pile at the lowermost end uses so-called knot piles 32 having annular protrusions on the outer surface, and so-called straight piles 33 and 33 having no protrusions on the outer surface other than that (upper part) (FIG. 3). ((A) (b)).
Further, as the ready-made pile 31 (knot pile 32, straight pile 33, 33) descends, the cement milk 28 in the pile hole 20 overflows from the opening of the pile hole 20 (near the ground 11). The cement milk 28 overflowing with water is collected and processed.
The present invention is in a state where the tip of the ready-made pile 31 reaches the vicinity of the bottom 24 of the pile hole 20 (inside the expanded bottom portion 23), the entire ready-made pile 31 is held near the ground 11, and the cement milk 28 is solidified. A foundation pile 40 is constructed (FIG. 3 (c)).
In this state, the portion of the contaminated soil layer 12 penetrated by the pile hole 20 (upper pile hole 21) is covered with a columnar lid with solidified cement milk. Therefore, there is no possibility that water containing contaminants of the contaminated soil layer 12 will be mixed into the pile hole 20 (inside the solidified cement milk) from the contaminated soil layer 12.

(10) In the above, the water and cement milk (FIGS. 3A and 3B) overflowing from the inside of the pile hole 20 onto the ground 11 are transferred to the Kamaba pit 36 and insolubilized as in the case of the upper pile hole 21. Dispose of it, confirm its safety, and discharge it to the outside of the site. At this time, since the cement milk is formed from insoluble cement, it can be put together as it is, but it is also possible to add insoluble cement.
At the same time, it can be confirmed that the solidification strength of the cement milk 28 satisfies a predetermined condition.
Further, in the state where the excavation of the pile hole 20 is completed (FIG. 2 (d)), the water component in the pile hole 20 is collected (mainly near the ground 11 and near the depth of the contaminated soil layer 12). If this water is analyzed and no contaminants are mixed in, then the cement milk to be added can be the usual cement used in this method without using insolubilized cement. It is also possible to add a neutralizing agent for a specific contaminant.

4. Other embodiments

(1) In the above embodiment, the head body 6 of the excavation head 5 may be provided with a kneading surface having the same function as the kneading drum 2 (not shown). Further, the excavation arm 8 may be provided with a kneading surface having a function equivalent to that of the kneading drum 2 together with the moving excavation blade 9 (not shown). With such a structure, the excavation head 5 can reliably knead the end face 12a of the contaminated soil layer 12, the shaft portion 22 of the pile hole, and the bottom expansion portion 23.

(2) Further, in the above embodiment, water was injected into the pile hole 20 to excavate the pile hole 20 (upper pile hole 21, shaft portion 22, bottom expansion portion 23), but instead of water, excavation liquid was excavated. (Bentonite solution) can also be used.
In addition, if there is a risk of seepage into the pile hole from the end face of the contaminated soil layer, a component that can neutralize (for example, chemically) the pollutants of the contaminated soil layer 12 or an insolubilizer (for example) in water. It is also possible to use water mixed with water (which can make the whole semi-solid so that it is insoluble in water, including the contaminated components of contaminated soil).
(3) Further, in the above-described embodiment, the excavated soil (including contaminated soil) from the lower pile hole 21 is discharged by a heavy machine or the like and moved to the Kamaba pit, but the kneading function and the soil draining function (spiral, etc.) are discharged. If an excavation rod provided with () is used (not shown), all or part of the excavated soil can also be discharged onto the ground 1 using this excavation rod.

(4) Further, in the above embodiment, the excavation rod 1 used for excavating the lower pile hole 21 and the excavation rod 1 for excavating below the shaft pile hole 21 after being pulled up can be used properly. For example, the lower pile hole 21 is used as an excavation rod dedicated to excavation with an excavation rod 1 having a function of kneading and excavating soil, and there is a possibility that contaminants may adhere to the excavation head 5. Therefore, this excavation rod is always used as a lower pile hole. When used for excavation of 21, different pile holes can be excavated in parallel, and work efficiency can be improved (not shown).

(5) In the above embodiment, cement milk using insolubilized cement was injected into the pile hole 20 for which excavation was completed, and the ready-made pile 40 was buried as a structure. Can also be inserted to inject concrete using insolubilized cement as a water-hardening material to form so-called cast-in-place piles (not shown). In this case as well, cement other than insolubilized cement can be used as the concrete.

(6) In the above-described embodiment, the unit ready-made pile has the lowermost end as a knot pile 32 and the other as a straight pile 33, but the unit ready-made pile is arbitrary depending on the load (bearing capacity) borne by the foundation pile 40. Can be selected and implemented (not shown). Further, the structure of the pile hole 20 to be excavated is also arbitrary (not shown) such that the bottom expansion portion 23 is not formed according to the load (bearing force) borne by the foundation pile 40.

1 Excavation rod 2 Kneading drum (excavation rod)
3 Kneading means (kneading drum)
4 Stirring means (stirring bar)
5 Excavation head (excavation rod)
6 Head body (excavation head)
7 Fixed excavation blade (excavation head)
8 Excavation arm (excavation head)
9 Moving excavation blade (excavation head)
11 Ground 12 Contaminated soil layer 12a End face of contaminated soil layer (pile hole wall)
13 Silt layer 14 Intermediate layer 15 Support layer 20 Pile hole 21 Upper pile hole 21a Upper pile hole bottom 22 Pile hole shaft 23 Pile hole expansion 24 Pile hole bottom 28 Cement milk 31 Ready-made pile 32 Section pile (ready-made) Pile)
33 Straight pile (ready-made pile)
35 Excavated soil in the upper pile hole 36 Kamaba pit 40 Foundation pile

Claims (4)

A method for constructing a foundation pile in the ground including a contaminated soil layer, which is characterized by excavating as follows when constructing a foundation pile in the ground having a contaminated soil layer near the ground surface.
(1) From the ground, with an excavation rod equipped with a discharge port and an excavation blade at the excavation head at the lower end , water or excavation liquid is injected and excavated while kneading the pile hole wall of the contaminated soil layer to the contaminated soil . If the excavation blade of the excavation rod penetrates the contaminated soil layer, an upper pile hole is formed, the excavation is temporarily stopped, and the excavation rod is moved while preventing the water in the layer from seeping out . It is pulled up to the ground and the lower part of the excavation rod is cleaned or washed .
(2) Using the excavation rod, at the same time as the step of (1) above, or by using another means, the excavation surplus soil containing the contaminated soil in the upper pile hole is discharged to the ground.
(3) The tip end side of the excavation rod is inserted into the upper pile hole, and excavation liquid, water, etc. are injected into the pile hole to knead the pile hole wall of the contaminated soil layer and further downward. And excavate.
(4) The pile hole is constructed by excavating to the support layer with the excavation rod, and the pile hole bottom is injected with a water-hard material from the discharge port into the pile hole filled with water or excavated mud. Then , the excavation rod is pulled up to the ground.
(5) While pulling the excavation rod to the ground or after pulling the excavation rod to the ground , the structure is buried to construct a foundation pile. The method for constructing a foundation pile in the ground including a contaminated soil layer according to claim 1, wherein the foundation pile is excavated as follows.
(1) In the ground where the contaminated soil layer is formed on the impermeable soil layer, if the excavation blade of the excavation rod penetrates the contaminated soil layer and reaches the impermeable soil layer, the upper pile hole Is formed, excavation is temporarily stopped, the excavation rod is pulled up to the ground, and the excavated residual soil in the upper pile hole is discharged from the upper pile hole. The method for constructing a foundation pile in the ground including a contaminated soil layer according to claim 1, wherein the foundation pile is excavated as follows.
(1) Form a Kamaba pit in advance on the site or in the vicinity.
(2) Once the upper pile hole is formed, the excavated soil in the upper pile hole is discharged to the ground and moved into the Kamaba pit.
(3) The insolubilizing material is put into the Kamaba pit, and the mud cake is discharged from the Kamaba pit as a mud cake by insolubilizing the excavated soil while confirming the elution of pollutants . The method for constructing a foundation pile in the ground including a contaminated soil layer according to claim 1, wherein the excavation rod is a kneaded drum formed directly above the excavation head.

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