JPH0931962A - Back-filling work of buried material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct the upper bed such as a subgrade in an extremely short period, even if the back-filling soil is superplasticized earth having a general mixing ratio, by laying a powdery bed having a specified water-absorbing property and color difference on the upper face thereof after a superplasticized earth layer has been disposed around a buried material. SOLUTION: The periphery of a gas pipe 4 buried in the ground is filled back with superplasticized earth 6 to lay a superplasticized bed. After a specified strength of the superplasticized bed has been confirmed, a powdery layer 8 constituted of powdered materials having 4.2 or more in pF value and different from the existing earth by 1.5 or more in color difference is laid on the upper face of the superplasticized bed. Then, a subgrade 10, a base 12, and pavements 14 are laid on the upper face of the powdery layer one by one. Accordingly, the upper layer of the superplasticized bed is forcibly dehydrated and the density is increased and further, the strength is intensified. And at the same time, since the distance between particles of the superplasticized earth 6 is made close, the strength is quickly devrlred. And as the water in the lower part of the powdery layer 8 or the whole powdery layer is dehydrated, it is compacted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for backfilling underground buried objects such as gas pipes and communication cables.

[0002]

2. Description of the Related Art Conventionally, in the method of backfilling buried materials, excavated soil can be used as it is as a backfill material only when the excavated soil is good quality soil, and in many cases it is possible to use high quality piles from another location. Sand was brought in and used as backfill material.

However, due to various factors such as depletion of natural resources, environmental damage due to extraction, traffic pollution, and disposal site problem of excavated soil in recent years, there has been an active movement to effectively utilize excavated soil and other bad soil. It is becoming more common. For example, the method of stabilizing the excavated soil with an improved material and using it as a backfill material as an improved soil, or the method of using it as a backfill material with a solidifying property by mixing it with a solidifying material are gradually spreading. I'm doing it.

On the other hand, there are problems such as vibration and noise at the time of compaction in backfilling work, and road collapse due to insufficient compaction. Therefore, in place of the method of compacting and backfilling good quality soil and improved soil, a method of mixing earth and sand with water and solidifying material and filling and backfilling in a fluid state has begun to be studied. It has been put to practical use.

[0005] For example, Japanese Patent Laid-Open No. 63-233115 discloses that a reciprocating rotary stirring mixer mixes water and a solidifying material with earth and sand and stirs them to obtain a high degree of homogeneity dispersibility and fluidity, as well as material separation. We propose a backfilling method for earth and sand, which is characterized by producing and supplying fluidized soil with strength development equivalent to the ground strength in a short time.

Further, in Japanese Patent Laid-Open No. 3-287909, solidification material is mixed and mixed in advance with the excavated soil, the treated soil is transported to a backfill site, and water is poured into the treated soil while backfilling and flowed with vibration. Has been proposed, and a method of completely filling the backfilled part is proposed.

Further, Japanese Patent Laid-Open No. 1-312118, and
Japanese Unexamined Patent Publication (Kokai) No. 4-351388 similarly proposes a construction method in which water and a solidifying material are mixed with earth and sand to be used as backfill for a buried pipe or the like as treated soil having fluidity.

[0008] In any of these, due to the fluidity of the backfilling material, compaction work at the time of backfilling is unnecessary, and it is possible to fill narrow spaces such as the peripheral portion of the buried pipe. Further, due to the action of the solidifying material, it is possible to develop a strength equal to or higher than that of the natural ground after a certain period of time after backfilling.

Further, excavated soil and earth and sand which are not suitable as a backfill material in the normal state, such as construction sludge, can be effectively utilized as a backfill material. In addition, the gas pipe,
Alternatively, various buried objects buried or constructed under the surface of the road such as communication cables and the like are dug up and backfilled many times for the purpose of repair and maintenance.

However, it is difficult to know exactly where these buried objects are buried, and accidentally damages the gas pipe and causes an accident during excavation work, for example, work for digging up and repairing the gas pipe. The case that it ends up does not follow.

In order to prevent such an accident, as shown in FIG. 2, a display tape 3 indicating the presence of the buried object is arranged on the upper surface of the buried object such as the gas pipe 4 or the buried object is damaged. The protection plate 5 for preventing the above is arranged. The layout of the display tape 3 is specified for medium- and low-pressure pipes (less than 10 kgf / cm ² ) of city gas.

The display tape 3 is a green polyethylene sheet having a thickness of 0.15 mm and a width of 400 mm, for example. Further, the protective plate 5 has, for example, a thickness of 6 to 1
It is an iron plate having a width of 2 mm and a width of 600 to 1000 mm. At high pressure (internal pressure of 10 kgf / cm ² or more), the arrangement of the display tape 3 and the protective plate 5 is specified. In the figure, 6 is fluidized soil, 10 is a roadbed, 12 is a roadbed, and 14 is pavement.

[0013]

However, most of the road occupancy work on city streets, such as gas burial piping work, is often done under the condition of traffic release on the same day, and the time required for backfilling itself is two. It is forced to work for a short time of about an hour.

For this reason, when the backfilling method using fluidized soil is applied, it is required to solidify the fluidized soil in 30 minutes to 2 hours to a strength at which the upper layer portion such as the roadbed can be constructed. ing. However, in order to solidify the fluidized soil within the above time, a special solidifying material is required for each target soil, so the cost is high, and at the same time the compounding technology is complicated and the burden of quality control accompanying this is large. Become.

Therefore, when fluidized soil having a general composition is used, it usually takes at least 2 hours or more to enable the construction of the upper layer such as the roadbed.

Further, when a material that solidifies in a short time is used, it is necessary to promptly deal with mechanical troubles during construction, which causes an increase in the burden of construction management. Furthermore, since the fluidized soil has solidified when pulling out sheet piles for retaining soil after backfilling the roadbed,
There is also a problem that a gap is created between the sheet pile and the ground, causing the road to collapse and becoming a waterway for rainwater.

Therefore, the present invention is affected by the initial strength of the fluidized soil itself, even if the fluidized soil has a general composition in which the solidification time exceeds 2 hours until the upper layer can be worked. It is necessary to provide a method for backfilling buried objects in which the upper layer can be constructed within 2 hours, more preferably within 1 hour, and the above problems do not occur even when the sheet pile is pulled out. The purpose of 1.

Further, as described above, the placement of the display tape 3 and the protective plate 5 requires the placement work by the operator in the excavated groove and the placement work by the heavy equipment. Further, since beams are installed everywhere in the excavated trench, the protection plate 5 and the like must be arranged avoiding these beams, which is time-consuming, time-consuming, and dangerous.

Therefore, the present invention is a backfilling method using fluidized soil, which enables construction of the upper layer within the above two hours, and does not require the conventional arrangement of a display tape or a protective plate and is safe. The second purpose is to provide a method for backfilling a buried object that makes it easy to recognize the existence of the buried object.

[0020]

Means for Solving the Problems The inventors of the present invention have laid a powder layer having a water absorption capacity of a predetermined value or more on the upper surface of the fluidized soil layer even if the fluidized soil has the above-mentioned general composition, It was found that the upper part of the fluidized soil layer can be forcibly dehydrated to increase the density and increase the strength within 2 hours.

At the same time, at this time, by making the powder layer a powder layer having a certain color difference with respect to the soil at the present position, various buried objects are dug up or buried when they are backfilled. Since the existence can be recognized in advance, the knowledge that these damages can be prevented was obtained, and the following inventions were achieved.

(1) According to the invention of claim 1, when backfilling various buried objects buried or constructed below the ground surface, a fluidized soil layer is disposed around the buried object, and then the fluidized A powder layer composed of powder having a pF value of 4.2 or more and a color difference from the soil at the present position of 1.5 or more is laid on the upper surface of the soil layer, and the upper surface of the powder layer is further provided. There is provided a backfilling method for a buried object, which is characterized by disposing a roadbed or a roadbed layer.

(2) In the invention of claim 2, after laying the powder layer, water is sprinkled on the upper surface of the powder layer so that the upper layer of the powder layer is appropriately compacted and solidified, The roadbed or roadbed layer is provided on the upper surface of the powder layer.
The method for backfilling the buried object described in 1. is provided.

(3) According to the invention of claim 3, the color difference of the powder layer is set to 3.0 or more with respect to the soil at the present position, and the filling of the buried object according to claim 1 or 2. Provides a return method.

(4) The invention according to claim 4 is characterized in that all or a part of the powder is colored with a pigment, and the embedding according to any one of claims 1, 2 and 3. Providing backfilling method for products.

(5) The invention of claim 5 is characterized in that the powder layer is laid at a temperature of the powder of 25 ° C to 50 ° C. The method for backfilling the buried object described in 1. is provided.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION According to the invention of claim 1, the surroundings of the buried object are backfilled with fluidized soil, and after confirming the development of a predetermined strength, a powder having a high water absorption with a pF value of 4.2 or more is prepared. By laying, the upper layer of the fluidized soil layer can be forcibly dehydrated, the density can be increased and the strength can be physically increased, and
At the same time, since the distance between the particles of the fluidized soil is close, the strength development is accelerated and the initial strength can be increased.

At the same time, the lower layer or the entire layer of the laid powder layer is compacted by absorbing water, and the strength is synergistically increased together with the upper layer of the fluidized soil layer. The load can be supported by the board effect due to these strength increasing actions, and the upper layer portion can be constructed early.

The pF value of the powder is set to 4.2 or more because the above powder does not sufficiently absorb moisture from the upper part of the fluidized soil layer when the pF value is less than 4.2. This is because you cannot get Further, since this powder layer has a certain color difference, it is possible to inform the existence of the buried object when the buried object is dug up, and prevent the buried object from being accidentally damaged.

Here, the pF value is an index that represents the suction force when the powder absorbs water against gravity against the concept of energy, and the energy of water (capillary potential) that rises the capillaries in the powder. The height of the water column (Hcm) is defined by pF = log ₁₀ H.

That is, the pF value is an index of the water absorption capacity. For example, pF = 3.0 is the plastic limit and pF = 4.2.
Is shrinkage limit, pF = 5.5 is air dry, pF = 7.
0 is the oven dry state. The water retention function of the powder has a pF value of 3.
When it is 0 or less, it is the water-retaining state of the pores, when it is 4.2 or more, it is the water-retaining state on the surface, and 3.0 to 4.2 is the mixed state of both.

Therefore, if pF = 4.2 or more, the powder retains only surface water, and there is no moisture in the interstices of the particles, and the powder has a sufficient water absorption capacity. Further, the water absorption of the powder here is mainly due to the capillary phenomenon between the powder particles, but the water absorption by the pores of the particles themselves may be included.

In the invention of claim 2, after laying the powder layer, water is sprinkled on the upper surface portion of the powder layer so that the upper layer portion of the powder layer is appropriately compacted. The compaction strength is obtained also from the upper layer portion of the powder layer. Thereby, due to the synergistic effect with the compaction strength of the fluidized soil layer upper layer portion and the powder layer lower layer portion, the construction time can be further shortened.

According to the third aspect of the present invention, by setting the color difference of the powder layer to the soil at the present position to be 3.0 or more, the presence of the buried object can be more reliably notified when the buried object is dug up, and the buried object is buried. It is possible to prevent accidental damage.

According to the fourth aspect of the invention, the color difference and the color tone can be freely secured by making all or part of the powder colored with a pigment.

According to a fifth aspect of the invention, the temperature of the powder is 25 to 5
By setting the temperature to 0 ° C., the curing atmosphere temperature can be increased and the solidification rate can be further increased. Especially in winter, the effect is great. If the temperature exceeds 50 ° C, the solidified material in the fluidized soil may be abnormally condensed and the human body may be difficult to handle such as burns. If the temperature is lower than 25 ° C, the above effect cannot be obtained.

In any case, the fluidized soil layer is not completely solidified yet and is still solidifying. Therefore, when the sheet pile or the like is pulled out, no gap is formed between the fluidized soil layer and the ground. It will not cause road collapse or become a waterway.

The thickness of the powder layer in the present invention is a thickness suitable for the upper layer of the fluidized soil layer and the lower layer of the powder layer to be appropriately hardened within 2 hours, and at the time of re-excavation. The thickness is such that the embedded object can be easily recognized, and it depends on the type of powder, particle size, etc., and is not particularly limited. However, it is usually preferably 100 to 300 mm.

That is, as the thickness of the powder layer becomes smaller than 100 mm, it becomes difficult to easily recognize the buried object when re-excavating. Also, if the thickness of the powder layer exceeds 300 mm, the strength of the powder layer itself as a roadbed tends to gradually become insufficient.

The fluidized soil as referred to in the present invention means that soil and sand are mixed with water and cement-based, lime-based and slag-based solidifying materials and, if necessary, limestone powder, crushed stone powder, fly ash and other particle size adjusting materials. In addition, it is a material having fluidity and curability, in which bubbles due to a foaming agent or a foaming agent are mixed.

Examples of the earth and sand include improved earth and sand obtained by stabilizing the earth and sand with lime and the like, a mixture of the earth and sand and the improved earth and sand, and the case where the earth and sand and the earth and sand are lightweight earth and sand containing a lightweight material such as expanded polystyrene.

The powders are those existing in nature such as sand, cohesive soil and shirasu, those obtained by artificially treating natural raw materials such as lime, limestone powder and crushed stone powder, and by-products such as blast furnace slag and the like. It is a processed product or the like in which the particle size is adjusted or dried, and any material that satisfies the specified pF value may be used.

It is also necessary that it is stable for a long period of time and will not cause road subsidence in the future due to corrosion or the like. Furthermore, it must not adversely affect the surrounding environment such as soil pollution.

Next, the powder having a certain color difference with respect to the soil at the present position is a powder having a color difference of 1.5 or more, preferably 3.0 or more, and even if the powder is colored with a pigment. Alternatively, it may be obtained by mixing already colored earth and sand or the like.

The above-mentioned pigments are not limited to inorganic and organic pigments, but are preferably excellent in alkali resistance, light resistance, weather resistance, heat resistance, etc., and are resistant to alkali, light, weather, heat, etc. Inorganic pigments that show as little color fading as possible are preferable.

The pigment is selected by comprehensively judging the following conditions. (1) It is necessary to obtain a color difference that can be distinguished from the current position soil. That is, the color difference at which the powder layer can be identified as being present in the soil at the current position is 1.5 or more, and the color difference at which the powder layer is conspicuous is 3.0 or more, which is a large color difference. It is 6.0 or more that is felt to be present, and 12.0 or more is felt to have a large color difference.

(2) Further, it is desirable that the color of the powder is complementary to or close to that of the soil at the present position. (3) The powder color can be determined in advance depending on the type of the buried object. For example, green is used when the buried object is a gas pipe, blue is used when the buried object is a water pipe, and red is used when the buried object is a communication cable such as a telephone line.

It is also possible to use a binder to ensure coloring. That is, when the powder is colored with an inorganic pigment by stirring with a mixer or the like, the pigment is not easily fixed to the powder without the binder.

As the binder, cement or a cement-based, lime-based or slag-based solidifying material is easily available,
It is relatively inexpensive and it is possible to reliably fix the pigment to the powder. In addition, as the binder, acrylic acid ester-based, cyanoacrylate-based, epoxy-based, nitrile-based resins, and the like can be considered.

Regarding the above-mentioned cement or solidifying material which is a binder, it is possible to mix only the binder with the powder or mix the binder and water together with the powder. This mixing amount is determined by the type and amount of pigment, the type of powder, the required color difference, and the strength required for the finished powder.

It is also possible to carry out firing in a simple furnace without using a binder. Further, coloring may be performed by spray-adding a liquid in which a pigment is dissolved and reducing the water content by drying. Examples of pigments include inorganic pigments manufactured by Bayer Co., Ltd., and the pigment colors include red, yellow, and green. The above pigment,
When selecting the binder, the water absorption described above is naturally taken into consideration.

As various buried objects buried or constructed under the surface of the earth, gas pipes, water pipes, communication cables, and various other things can be considered. The term "under the ground surface" as used herein is generally under the road, but is not limited to this and includes all places where buried objects may exist.

[0053]

Embodiments will be described below. Table 1 shows an example of the composition of fluidized soil used in the following examples.

[0054]

[Table 1]

Comparative Example FIG. 2 shows a conventional general backfilling method using the ordinary fluidized soil 6 and the display tape 3. The color difference of the fluidized soil 6 is usually not taken into consideration with respect to the current location soil. In FIG. 2, the fluidized soil 6 was arranged around the gas pipe 4, which is an underground buried object.

Approximately 5 hours after the completion of casting the fluidized soil layer, it was confirmed that the strength of the fluidized soil layer reached a cone index q _c = 1.5 kgf / cm ^2, and then a road was placed on the upper surface of the fluidized soil layer. Flooring 10
As a result, add sand and compact it. At this time, the protective plate 5 is provided on the upper layer of the fluidized soil layer, and the display tape (width 4
(00 mm, thickness 0.15 mm, color green) was laid and compacted with a rammer.

After the earth retaining sheet pile 16 is pulled out, the roadbed 12 and the pavement 14 are further constructed above it. As described above, when the conventional general backfilling method using ordinary fluidized soil was used, it took about 5 hours to start the upper layer construction.

Therefore, the conventional construction method cannot be applied to the construction requiring a short time construction such as the same day restoration construction. Moreover, after pulling out the earth retaining sheet pile, a gap was confirmed between the fluidized soil and the ground.

Example 1 An example of the present invention will be described with reference to FIG. In FIG. 1, fluidized soil 6 was arranged around the gas pipe 4 which is an underground buried object. The strength of the fluidized soil layer has a cone index q _c = 0.1 kgf / cm
^{When the value} reached ² , the air-dried sand colored with a green pigment on the upper surface of the fluidized soil layer (10 tons of sand was mixed with 10 kg of chrome green GM manufactured by Bayer Co., Ltd. as a pigment) (pF value 5.5) ) Powder layer 3 (layer thickness 3
(00 mm) was put in with a scoop and laid.

Next, mountain sand, which is a roadbed material, was placed on the upper surface of the powder layer and compacted with a rammer. Furthermore, the roadbed and pavement were constructed above it. The pigment and the sand were mixed with the mixer used for producing the fluidized soil. In this case, the time from the completion of pouring the fluidized soil layer to the introduction of the roadbed material was about 1 hour and 30 minutes.

As described above, by using mountain sand, which is a general roadbed material, as the powder, and leaving it in the air and using it as a powder layer with a pF value of 4.2 or more, construction is carried out. The time has been shortened by 3 hours or more, and it has become a construction method applicable to restoration work on the same day.

Further, it is possible to minimize the production cost of the colored powder by using a general-purpose civil engineering building material, leaving it to dry in the air, and further mixing it with the pigment in the fluidized soil production mixer. Became.

Since the laying of the powder is also incorporated in one step of the roadbed construction, a new step does not occur and the labor for laying the display tape can be omitted. Furthermore, when pulling out the sheet pile for retaining soil, the fluidized soil layer is at a strength level that cannot be self-sustaining except the surface layer, so that no void is formed between the fluidized soil layer and the ground. Therefore, there is no risk of land subsidence after the completion of construction.

Example 2 A fluidized soil layer having the composition shown in Table 1 was arranged around a water pipe which was a buried object. The strength of the fluidized soil layer is 0.0 in the cone index
After confirming that it became 5 kgf / cm ² , a powder layer (layer thickness 150 mm) composed of limestone powder (color difference from the original ground, pF value 6.5) was formed on the upper surface of the fluidized soil layer. Laid

Mountain sand, which is a roadbed material, was placed on the upper surface of the powder layer and compacted with a rammer. After pulling out the earth retaining sheet pile, the roadbed and pavement were constructed above it. In this case, the time from the completion of pouring the fluidized soil layer to the introduction of the roadbed material was about 1 hour.

As described above, by using limestone powder which has a large color difference from the original ground and can be clearly judged as white, it is possible to omit the trouble and equipment for mixing the powder and the pigment. Further, since the drying process is unnecessary, the labor and equipment required for the process can be omitted.

Example 3 A fluidized soil layer having the composition shown in Table 1 was arranged around a communication cable (4 pieces) which is a buried object. After confirming that the strength of the fluidized soil layer was 0.05 kgf / cm ^{2 in} terms of cone index, it was dried to an absolutely dry state on the upper surface of the fluidized soil layer with a simple furnace installed at the site. Powder sand (pF value 7.0) was mixed with red pigment by a mixer for fluidized soil production (5 kg of Bayerox Bayferrox as a pigment was mixed with 1 ton of sand) in a scoop. Was put into a 100 mm thick and laid.

Mountain sand, which is a roadbed material, was placed on the upper surface of the powder layer and compacted with a rammer. In this case, the time from the completion of fluidized soil pouring to the introduction of roadbed material was about 50 minutes. After pulling out the earth retaining sheet pile, the roadbed and pavement were constructed above it.

As in Example 2, by using a powder having a high water absorption property and further raising the temperature of the curing atmosphere of the fluidized soil by setting the powder temperature to about 40 ° C., the solidification rate can be further increased. It was Further, the solidified material did not cause abnormal condensation due to the above temperature conditions.

Example 4 A fluidized soil layer 2 having the composition shown in Table 1 was arranged around a gas pipe 1 which was a buried object. After confirming that the strength of the fluidized soil layer 2 was 0.1 kgf / cm ^{2 as a} cone index, a green pigment (chromium green GM manufactured by Bayer Co., Ltd. on 1 ton of sand was used as a pigment on the upper surface of the fluidized soil layer. Powder layer 3 (layer thickness 200 mm) made of air-dried sand (pF value 5.5) colored with 10 kg (mixed with 10 kg) was put in a scoop,
Laid

Immediately after laying, 40 kg / m ² of water was sprinkled with a sprayer so that the water content of the powder layer would be the optimum water content of 15% for compaction. Mountain sand, which is a roadbed material, was placed on the upper surface of the powder layer and compacted by a rammer. Furthermore, the roadbed and pavement were constructed above it.

The pigment and the sand were mixed with the mixer used for producing the fluidized soil. In this case, the time from the completion of the fluidized soil pouring to the compaction of the roadbed material was 1 hour.

As described above, by spraying water corresponding to the optimum water content ratio for compaction, the entire powder layer was in a water-tightened state, and the work time could be shortened by about 4 hours due to the dispersion of the load due to the board effect. .

[0074]

EFFECTS OF THE INVENTION According to the present invention, the upper surface of the fluidized soil layer disposed around the buried object has a large water absorption (pF value 4.
(2 or more) By laying the powder, the strength of the upper layer of the fluidized soil layer is increased, and at the same time, the lower layer of the powder layer itself or the entire layer is compacted, and the load from the upper layer is dispersed by the disc effect, Enables construction of upper layers at an early stage.

In the present invention, since fluidized soil having a general composition can be used, no special solidifying material is required. Therefore, it can be expected to reduce the cost of solidifying material, eliminate the need for special compounding technology, and reduce quality control.

Since the solidification time of the fluidized soil is so slow that it does not solidify during the mixing and setting of the fluidized soil, there is a time margin for mechanical troubles such as mixing and pumping, and construction management Can be greatly reduced. Furthermore, since there is no gap between the fluidized soil and the ground even when the sheet pile is pulled out, there is no risk of the roads, etc., sinking after the construction, and the quality of the entire construction is improved.

Further, in the present invention, since the powder layer has a certain color difference from the surrounding earth and sand and has the same function as the display tape, the presence of the buried object is known when the buried object is dug up and the buried object is buried. This has the effect of preventing accidental damage to objects. Further, since the powder layer is arranged as one step of loading the roadbed material, there is an effect that no new cost is required for construction.

[Brief description of drawings]

FIG. 1 is a diagram showing an underground structure backfilled by applying the construction method of the present invention.

FIG. 2 is a diagram showing an underground structure by a backfilling method using fluidized soil and a conventional display tape or a protective plate.

[Explanation of symbols]

 2 Ground surface 3 Indication tape 4 Underground buried object 5 Protective plate 6 Fluidized soil 8 Powder layer 10 Roadbed 12 Roadbed 14 Pavement 16 Earth retaining sheet pile

Claims (5)

[Claims] 1. When backfilling various buried objects buried or constructed below the ground surface, a pF value is provided on an upper surface of the fluidized soil layer after disposing a fluidized soil layer around the buried object. At 4.2
Above, and laying a powder layer composed of powder having a color difference of 1.5 or more different from the soil at the current position, and further disposing a roadbed or roadbed layer on the upper surface portion of the powder layer. The characteristic method for backfilling buried objects. 2. After laying the powder layer, water is sprinkled on the upper surface of the powder layer so that the upper layer of the powder layer is appropriately compacted, and the upper surface of the powder layer is sprayed with water. The method for backfilling a buried object according to claim 1, wherein a floor or roadbed layer is provided. 3. The buried material backfilling method according to claim 1 or 2, wherein the color difference of the powder layer is 3.0 or more with respect to the current position soil. 4. The backfilling method for the buried object according to claim 1, wherein all or part of the powder is colored with a pigment. 5. The powder layer is laid at a temperature of the powder of 25 ° C. to 50 ° C.
The method for backfilling the buried object described in 2, 3, or 4.