JPH0967572A - Backfilling method for buried item - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a backfilling method for a buried item which method uses a low-cost liquefied soil of a general formulation and enables the formation of an upper layer (e.g. a roadbed) within 2hr after the deposition of the liquefied soil. SOLUTION: In a method for backfilling a buried item 3 buried or constructed under the ground surface, a liquefied soil layer 1 is deposited so as to enclose the item 3; then a sand layer 2 comprising earth and sand contg. 3-20wt.% hydraulic material is formed on the layer 1; and an upper layer 4 (e.g. a roadbed) is formed on the layer 2.

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 objects such as gas pipes and communication cables.

[0002]

2. Description of the Related Art Conventionally, as a backfill material used when backfilling an underground buried object, in many cases, good quality sand or the like collected from another place is used. This is because excavated soil generated during the laying of underground buried objects is rarely suitable for backfill materials.

In recent years, from the viewpoints of depletion of high-quality mountain sand, which is a natural resource, environmental damage due to its extraction, traffic pollution due to its transportation, and disposal problems of excavated soil, excavated soil and construction unsuitable as backfill materials. There is a growing movement to effectively utilize sludge and other bad soil.

In the conventional backfilling method in which a backfill material such as high-quality sand is directly used, the backfill material is filled in a narrow portion such as a peripheral portion of the buried pipe without any gap in order to prevent depression after backfilling. Sufficient compaction with a rammer is required. However, in this conventional method, filling of the backfill material and compaction by a rammer are all manual work, and there is a problem that noise and vibration are caused.

Recently, instead of using a special backfill material such as the above-mentioned high quality mountain sand, excavated soil or cheap earth and sand generated when laying an embedded object is used, and the problems of the conventional method as described above. A fluidized backfilling method that can solve the problem has been developed and is partly in practical use. This method mixes water and solidified material with excavated soil and inexpensive earth and sand, gives the backfill material fluidity, fills narrow spaces around the buried pipe without gaps, and uses the effect of solidified material. It is intended to exhibit strength equal to or higher than that of the ground.

[0006] For example, Japanese Patent Laid-Open Nos. 63-233115, 1-312118, and 4-351.
No. 388 discloses a method in which water and a solidifying material are mixed with earth and sand, and the resulting soil is used for backfilling a buried pipe or the like as fluidized soil having fluidity.

Further, in Japanese Patent Laid-Open No. 3-287909, the excavated soil is mixed with a solidifying material in advance, and the treated soil is transported to the backfill site, and water is poured into the treated soil while backfilling and vibration is applied. A method of fluidizing and completely filling the backfilled portion is disclosed.

On the other hand, in the road occupancy work on the city streets, which occupies the majority of the gas burial piping work, it is inevitable that the work will be carried out under the condition that the traffic will be opened on the same day. Has become. In particular, when the fluidized backfilling method as described above is used, it is required that the upper layer portion such as the roadbed can be constructed within 2 hours after the fluidized soil layer is cast.

[0009]

However, with the fluidization backfilling method disclosed in the above-mentioned patent publication, the solidification time is as long as 4 to 5 hours, and it cannot be applied to the same day restoration work in urban areas.

If a special solidifying material is used in accordance with the fluidized soil, the solidifying time can be shortened, but the cost becomes high, and the solidification occurs too quickly, which makes the construction management difficult.

The present invention has been made in order to solve the above problems, and uses inexpensive general fluidized soil having a general composition, and moreover, within 2 hours after placing the fluidized soil layer, the upper layer of a roadbed or the like. It is an object of the present invention to provide a method for backfilling buried objects that enables construction of parts.

[0012]

[Means for Solving the Problems] The above-mentioned problems are, in a backfilling method for backfilling various buried objects buried or constructed below the ground surface, after placing a fluidized soil layer around the buried object, A buried object, characterized in that a sediment layer made of sediment containing 3 to 20% by weight of a water-curable material is provided on a fossil layer, and an upper layer portion such as a roadbed is constructed on the sediment layer. It is solved by the backfilling method.

When a sediment layer composed of sediment containing a water-curable material is provided on the fluidized soil layer, the water-curable material in the layer reacts with water absorbed from the upper portion of the fluidized soil layer by a capillary phenomenon and hardens. Therefore, the strength of the layer is increased. Also, at this time, the upper part of the fluidized soil layer is dehydrated and the density increases,
The strength of the upper part of the fluidized soil layer itself is also high. Therefore, it is possible to construct an upper layer portion such as a roadbed in a short time within 2 hours after placing the fluidized soil layer.

If the amount of the water-curable material contained in the earth and sand layer formed on the fluidized soil layer is too much, the long-term strength will be too high and re-drilling will be difficult, and the ratio will be small. If too much, the strength becomes insufficient and early construction of the upper layer portion such as the roadbed becomes difficult. Therefore, it is necessary to set the weight ratio to 3 to 20%.

When water is sprinkled on the earth and sand layer made of earth and sand containing a water-curable material, the upper layer of the earth and sand layer can be hardened in a short time, so that backfilling can be performed in a shorter time.

By providing a predetermined number of layers of the earth and sand layer containing the water-curable material on the earth and sand layer while sprinkling the water, it is not necessary to place a new subgrade, Since the upper layer part such as the roadbed can be directly constructed, it is possible to backfill in a shorter time. It is necessary to appropriately determine the number of layers of earth and sand depending on the installation conditions of the buried object, the type of earth and sand, and the water-curable material.

When gypsum, an early-strength cement or a solidifying material is used as the water-curable material, the strength develops quickly, so that backfilling can be performed in a shorter time. Further, if gypsum is used, its long-term strength is small, so that re-drilling becomes easy.

Further, when cement containing a quick-setting agent is used as the water-curable material, the solidification rate can be remarkably increased, so that the time can be remarkably shortened.

The water content of the sand containing the water-curable material is such that when the water-curable material is mixed, it reacts with the water-curable material to solidify the water-curable material or to condense the water-curable material into a lump. In order not to do so, it is desirable that the surface is in a dry state or lower.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a method for backfilling buried objects according to the present invention. In the figure, 1 is a fluidized soil layer, 2 is a layer made of earth and sand containing a water-curable material, 3 is a buried object such as a gas pipe, 4 is a roadbed, 5 is a roadbed, 6 is pavement, 7 is the ground surface, 8
Is a steel sheet pile for retaining soil.

As the earth and sand used for the layer 2 made of earth and sand containing a water-curable material, it is possible to use ordinary earth and sand that is inexpensive and easily available, for example, ordinary mountain sand. Further, as described above, it is desirable that the water content state is equal to or lower than the surface dry state in which water is not retained in the gaps between the particles, but in the case of ordinary earth and sand, the water content ratio is 3 to It corresponds to a state of 4%.

Various cements, solidifying materials, gypsum, quick lime, fly ash, granulated blast furnace slag and the like can be used as the water-curable material for the layer 2 made of earth and sand containing the water-curable material. Thus, it is preferable to use gypsum, an early-strength cement or a cement containing a solidifying material or a quick-setting agent.

When water is sprinkled onto the layer 2 made of earth and sand containing a water-curable material, the sprinkling amount is the short-term strength of this layer 2,
Although it needs to be determined from the viewpoint of long-term strength, the appropriate amount of water changes depending on the content of the water-curable material in the layer 2, the thickness of the layer 2, the water absorption speed of the layer 2, and the like. As a guideline, it is desirable that the amount of water permeates all the layers except the lower layer portion of the layer 2 (the portion that absorbs water from the fluidized soil layer 1 due to the capillary phenomenon). For example, when the layer 2 made of earth and sand mixed with early-strength cement at a weight ratio of about 10% is provided, the water content is required to be 15% at a water content ratio.

The thickness of the layer 2 made of earth and sand containing a water-curable material needs to be determined from the viewpoint of the short-term strength and long-term strength of the layer 2, but the content of the water-curable material in the layer 2 and The appropriate thickness changes depending on the amount of water sprayed.

[0025]

【Example】

(Example 1) After arranging a gas pipe below the surface of the earth, after placing a fluidized soil layer made of fluidized soil shown in Table 1 around the gas pipe, the strength of the fluidized soil layer was 0. At a pressure of 01 kgf / cm ² , a thickness of about 20% composed of air-dried mountain sand containing 8% by weight of ultra early-strength cement and a water content of 3%.
A layer of earth and sand containing 0 mm of hydraulic material was placed. After that, when the strength of the earth and sand layer containing this water-curable material reached 1.0 kgf / cm ^{2 in} terms of cone index, mountain sand, which is the roadbed material, was added, compacted with a rammer, and paved on top of it. Was built. At this time, the time from the completion of the pouring of the fluidized soil layer to the introduction of the roadbed material was 1 hour and 20 minutes, which was shorter than the conventional method by 3 hours or more. Moreover, the uniaxial compressive strength of the sediment layer containing the water-curable material after 3 months is 2.5 kgf / c.
It was m ² , and the strength was such that re-drilling with a scoop was possible. In addition, since the sand was left to dry in the air and the mixer for fluidized soil production was used when mixing the water-curable material, the production cost could be minimized.

(Example 2) After arranging a gas pipe under the ground surface,
A fluidized soil layer consisting of fluidized soil shown in Table 1 was placed around the gas pipe.
After pouring, the strength of the fluidized soil layer is 0.01 kg in terms of cone index.
f / cm²When it became, 20% by weight of hemihydrate
Thickness of air-dried mountain sand containing 5% of water
A layer of earth and sand containing approximately 200 mm of water-curable material was placed.
Then place this soil on top of the layer of sediment containing this water-curable material.
Water was sprinkled so that the water content of the sand layer was 15%. Water hardening
The strength of the soil layer containing the material is 1.0 kgf /
cm ²At that point, throw in the mountain sand that is the roadbed material,
It was compacted with a rammer and pavement was built on it.
At this time, from the completion of pouring the fluidized soil layer to the introduction of roadbed material
The time was 1 hour and 10 minutes. Water hardening after 3 months
Uniaxial compressive strength of soil layer containing elastic material is 2.0kgf / c
m²And the strength is such that it can be re-drilled with a scoop.
Was. It should be noted that mountain sand is left to dry in the air and a water-curable material is used.
A fluidized soil production mixer was used when mixing
Therefore, the manufacturing cost could be minimized.

(Example 3) After arranging a gas pipe below the ground surface,
After placing the fluidized soil layer consisting of fluidized soil shown in Table 1 around the gas pipe, the strength of the fluidized soil layer is 0.01 kg in terms of cone index.
When f / cm ² was reached, an earth and sand layer containing a water-curable material having a thickness of about 300 mm made of air-dried mountain sand containing 20% hemihydrate gypsum by weight and a water content of 3% was provided. .
Then, water was sprinkled onto the earth and sand layer containing the water-curable material so that the water content ratio of the earth and sand layer was 15%. The strength of the soil layer containing the water-curable material is 0.7 kgf in cone index
When it reached / cm ² , the mountain sand, which is the roadbed material, was put in, compacted with a rammer, and pavement was constructed on it. At this time, the time from the completion of the pouring of the fluidized soil layer to the introduction of the roadbed material was 1 hour and 10 minutes. Moreover, the uniaxial compressive strength of the earth and sand layer containing the water-curable material after 3 months is 2.0 kgf.
/ Cm ² , and the strength was such that re-drilling with a scoop was possible. It should be noted that the sand and gypsum were mixed when the sand was dried and carried into the site, so the work on site could be reduced.

(Embodiment 4) After disposing a gas pipe below the ground surface,
After placing the fluidized soil layer consisting of fluidized soil shown in Table 1 around the gas pipe, the strength of the fluidized soil layer is 0.01 kg in terms of cone index.
When f / cm ² was reached, it consisted of 5% by weight of ordinary Portland cement containing 10% by weight of a quick-setting agent (QP-55 made by Pozzolis) and 2% by weight of air-dried mountain sand. An earth and sand layer containing a water-curable material having a thickness of about 250 mm was arranged. Water was sprinkled so that the water content ratio of this sediment layer was 15%. When the strength of the soil layer containing the water-curable material reached a cone index of 1.5 kgf / cm ² , mountain sand, which is the roadbed material, was added, compacted with a rammer, and pavement was constructed on it. . At this time, the time from the completion of the pouring of the fluidized soil layer to the introduction of the roadbed material was 50 minutes. Also,
The uniaxial compressive strength of the earth and sand layer containing the water-curable material after 3 months was 1.5 kgf / cm ² , and the strength was such that re-excavation with a scoop was possible. It should be noted that the sand, the ordinary Portland cement and the quick-setting admixture were mixed when the sand was dried and carried into the site, so the work on the site could be reduced.

(Example 5) After arranging a gas pipe under the ground surface,
After placing the fluidized soil layer consisting of fluidized soil shown in Table 1 around the gas pipe, the strength of the fluidized soil layer is 0.01 kg in terms of cone index.
When f / cm ² was reached, a sand layer containing a water-curable material with a thickness of about 200 mm made of air-dried mountain sand containing 4% by weight of early-strength cement and a water content of 2% was provided. did. Water was sprinkled so that the water content ratio of this sediment layer was 15%. This earth and sand layer and watering were repeated to construct a subgrade, and the upper layer part such as the subbase was constructed. At this time, the time from the completion of placing the fluidized soil layer to the start of construction of the upper layer portion such as the roadbed was 1 hour and 30 minutes. In addition, the uniaxial compressive strength of the earth and sand layer containing the water-curable material after 3 months was 2.0 kgf / cm ² , and the strength was such that re-excavation with a scoop was possible. In addition, since the sand and the early-strength cement were mixed when the sand was dried and brought into the field, the work on the site could be reduced.

[0030]

[Table 1]

[0031]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, fluidized soil of an inexpensive general composition is used, and the upper layer portion of the roadbed or the like is used within 2 hours after the fluidized soil layer is cast. It is possible to provide a method of backfilling a buried object that can be constructed.

Further, by using the backfilling method of the present invention, the backfilling work can be completed before the entire fluidized soil layer is completely solidified, so that the steel sheet pile for retaining soil can be easily pulled out, and After drawing the steel sheet pile, there is no gap between the fluidized soil layer and the ground, so no ground deterioration occurs.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of a method for backfilling a buried object according to the present invention.

[Explanation of symbols]

 1 Fluidized soil layer 2 Sediment layer consisting of sediment containing water-curable material 3 Buried objects such as gas pipe 4 Roadbed 5 Roadbed 6 Pavement 7 Ground surface 8 Steel sheet pile for retaining soil

Claims (6)

[Claims] 1. In a backfilling method for backfilling various buried objects buried or constructed under the surface of the earth, a fluidized soil layer is cast around the buried object, and then a weight ratio is applied on the fluidized soil layer. In 3
A method for backfilling a buried object, comprising: providing a sediment layer made of sediment containing 20% of a water-curable material, and constructing an upper layer portion such as a roadbed on the sediment layer. 2. The backfilling method for the buried object according to claim 1, wherein after the earth and sand layer is provided, water is sprayed on the earth and sand layer. 3. A backfilling method for backfilling various buried objects buried or constructed under the surface of the earth, in which a fluidized soil layer is cast around the buried object and then a weight ratio is applied on the fluidized soil layer. In 3
A sediment layer consisting of sediment containing ~ 20% water-curable material,
A method for backfilling a buried object, wherein a predetermined number of layers are provided on the earth and sand layer while water is sprinkled, and an upper layer portion such as a roadbed is constructed. 4. The water-curable material is gypsum, a fast-setting cement or a solidifying material.
4. The method for backfilling the buried object according to any one of claims 3 to 4. 5. The method for backfilling a buried object according to claim 1, wherein the water-curable material is a cement containing a quick-setting agent. 6. The backfilling method for a buried object according to claim 1, wherein the water content of the sand containing the water-curable material is not more than the surface dry state.