JP2564587B2 - Artificial ground creation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an artificial ground such as soil cement that uses an ice mass instead of a part or all of the water to be added in the preparation of an artificial ground material obtained by adding a cement-based material to earth and sand or rock. It relates to the method of creation, ground improvement, land reclamation,
It is used to construct subgrades and subgrades, or to construct artificial ground for re-excavation.

Background Art Excavated grounds that have built structures are usually backfilled,
It is required to have the same strength as the natural ground strength.
The ground such as roads and runways is generally required to have a higher ground strength than the ground strength. Conventionally, in order to meet such demands, the treated soil in which cement-based materials such as cement, lime and gypsum are mixed in the excavated earth and sand is backfilled in the excavated ground, and this is compacted by spreading pressure etc. Waiting for the material to harden, a stabilizing treatment is carried out to develop the desired strength.

In such stabilization treatment, the ratio of cementitious material to excavated soil is usually less than 10%, which is relatively small. Further, in order to increase the strength of the treated soil mixed with the cement-based material, it is necessary to set the optimum moisture content corresponding to the mixed amount and compact it. However, it is often difficult to mix the cement-based material and water uniformly, because the particle size and the consistency of the soil are limited, and it is not easy to mix a small proportion of the cement-based material and water uniformly.

Examples of related technology relating to ground improvement include Japanese Patent Publication (B2) Sho 51-33662 and Japanese Patent Publication (B2) Sho 6
There are 1-8212 etc. The former relates to the method of adding cement and mountain soil to soft sludge substances such as sludge, stirring and mixing in a container installed at the site, and creating artificial ground of the required strength with the treated soil. Improvements are made at the same time. In the latter, the excavated soil separating device, the weighing device, and the mixing device are installed on the ground of the ground to be improved, the holes are excavated in the ground, and the excavated soil discharged on the ground is converted into muddy water and mud by the excavating soil separating device. Separate, add reinforcement to this mud and perform test kneading to calculate predetermined ground strength and unit volume weight.Measure mud and reinforcement with this measuring device so as to have this predetermined ground strength and unit volume weight, and then mix. This is to mix uniformly in the device, and to fill the generated ground reinforcement material uniformly in the previously drilled holes with a pressure pump.

However, in any of the methods, it is difficult to uniformly mix the earth and sand, the cement-based material, and water, and the strength of the hardened ground tends to vary. In addition, in the ground where gravel and rocks are contained, these are likely to separate, and a phenomenon such as aggregate separation in concrete is likely to occur. Further, particularly in the case of soft cohesive soil, it is not easy to uniformly disperse a small amount of water or cement-based material.

Further, regarding the preparation method and the manufacturing method of the mortars, the present inventor uses a small ice block instead of water, and gradually melts the small ice block in the process of mixing with the cement and the aggregate, so that the aggregate is homogeneous. It enables the construction of high-quality mortar and concrete that are difficult to separate and have excellent workability (see International Publication WO86 / 00884 and WO87 / 00163). Further, Japanese Patent Publication (B2) Sho 53-005694 discloses that powdered hydraulic binder and crushed ice or snowy water are mixed in a substantially dry state with water having a melting point or lower to a predetermined thickness. A method for manufacturing an architectural board that is cured at a temperature equal to or higher than the melting point of water after being compressed into a compact size is disclosed, and it is also suggested that a porous board is manufactured by adjusting the melting of ice during the curing process. Has been done.

The present invention is to add soil water such as soil cement used for soil improvement and landfill to the treated soil mixed with cementitious material in the form of ice cubes, and the solid phase or surface melts to form a pseudo-solid phase. Utilizing the characteristics of ice blocks in the state,
The treated soil with high homogeneity is efficiently produced, and the highly reliable artificial ground with desired strength can be constructed at low cost.

DISCLOSURE OF THE INVENTION In the method of the present invention, when mixing a cement-based material with excavated soil or rock using a mixing device, water necessary for the water content of the treated soil to reach a desired value is added in small ice blocks. To do. In the initial stage of mixing, the added small ice blocks behave as a solid phase or as a pseudo-solid phase in which a part of the small ice blocks melts and the soil or cement component adheres to the surface of the solid ice, the cement-based material and the small ice blocks. Can be easily mixed into a macroscopically homogeneous system by a short-time stirring means. Subsequently, the small ice block gradually melts, wets the surrounding earth and sand or cement components, and shifts to a homogeneous mixing system. Compared with the case where water is added directly, the treated soil can be made more homogeneous by stirring for a short time. This treatment method is not limited to the method in which all of the added small ice blocks are melted to form a homogeneous treated soil and then backfilled and compacted. The above-mentioned treated soil in a macroscopically homogeneously dispersed state may be backfilled. After backfilling, the small ice blocks gradually melt and move to a homogeneous mixed system. Further, by doing so, the mixing process can be shortened and the mixed soil can be backfilled in a state close to dryness, so that the work efficiency can be further enhanced.

If the earth and sand or rock is excavated at the site and after processing, it is backfilled in the excavated ground, so there is no problem of soil removal. Of course, in the case of land reclamation, the earth and sand collected at another place may be transported and used.

In addition, for earth and sand with a low natural water content, cement-based materials and small ice blocks can be added as they are, but if earth and sand with a high water content or muddy water is used during excavation, some amount of water will be added by a separator. Separate and add a small block of ice during stirring and mixing with the cementitious material.

A wide range of hydraulic compositions can be used as the cement-based material, and as the most common cements such as Portland cement, gypsum, coal, water glass, etc. can be used.
The soil particles can be combined to increase the strength of the treated soil after hardening.

A small ice block has a particle size of about 30 mm or less. When the soil and the temperature are high, a relatively large diameter is used, and when the temperature is low, a relatively small diameter is used. The amount of addition of small ice blocks is set by subtracting the natural water content of earth and sand from the optimum water content, and adjusting the water content if necessary, for example, depending on the degree of compaction. Incidentally, the treated soil after backfilling and compaction is appropriately treated as necessary in order to prevent the soil from drying.

Further, in the method of the present invention, a mixture of a cement-based material such as Portland cement and a relatively large-diameter ice block is mixed with an excavated material mainly composed of gravel and rock, and solidification is started to increase the Even with a mixture having a water-cement ratio, the ice blocks behave as solids, have low fluidity during pouring, and can be sparsely filled in the pouring space. As the solidification of the mixture progresses, the ice block gradually melts, moves into the surrounding mixture, and a void is formed after the ice block melts. As a result, a sparse cured product having a large number of voids, that is, a cured product having a low strength can be produced from a mixture having a high water cement ratio.

For example, if you inject and pour treated soil mixed with relatively large ice blocks into a vertical shaft that became an abandoned mine with a depth of several hundred meters,
The ice blocks gradually melt, and a cured product that remains as voids after melting is formed. In addition, since the ice blocks behave as solids, even if the water-cement ratio is relatively high, the fluidity is low and they can be loosely packed in the mine, so along with the voids after melting the ice blocks
It contributes to the formation of a relatively low strength cured product. The voids of the cured product to be produced are determined by the amount and size of ice blocks, the fluidity of the treated soil, the filling means, and other conditions. Therefore, by adjusting the water cement ratio and the ratio of voids, it is possible to prevent destruction of an abandoned mine, for example, and to perform re-drilling easily to produce a cured product having a certain adjusted strength.

In this case, the ice mass used has a relatively large diameter, and 10 mm to 100 mm is a suitable range for the specific numerical value. If the surrounding environment temperature is high, the larger diameter side,
If it is low, it is better to shift to the smaller diameter side.

In addition, if a substance having a thickening effect such as methyl cellulose is mixed in the mixture, or is dissolved and mixed in an ice block,
It is advantageous in that the fluidity of the mixture is lowered and the mixture is sparsely cast.

BEST MODE FOR CARRYING OUT THE INVENTION Regarding the soft ground (assuming that the uniaxial compressive strength is, for example, about 1.0 kg / cm ² or less in the cohesive soil) of the large structure foundation, Portland cement is added to the excavated soil at the site. hand,
The case of constructing improved ground by soil cement having a uniaxial compressive strength of about 10.0 kg / cm ² will be described.

A conventionally known method can be applied as it is to the compounding design of soil cement, and for example, it is performed as follows.

i) Examine the sample of excavated sediment for water content, particle size distribution and consistency.

ii) Add cement to the target soil at a rate of 2,4,6,8,10%, and obtain the optimum water content and maximum dry density by compaction, penetration test, etc.

iii) A uniaxial compression test is conducted after hardening for each cement amount compacted at the optimum water content ratio, and the relationship between the cement amount and strength is shown in a graph.

iv) From the graph, determine the amount of cement that produces a uniaxial compressive strength of 10.0 kg / cm ² .

If muddy water is used in the excavation, or if the natural water content is very high, the muddy water should be separated before the test. In addition, in the test kneading, the water to be added is replaced by a small ice block, so that the test can be performed under conditions closer to those of the method of the present invention.

Generally, the strength of soil cement mixed in the field is lower than that mixed in the laboratory, 60-80%.
It is considered to be degree. However, according to the method of the present invention using an ice block, the separation of sediment components having a relatively large particle size is suppressed, and the ice block itself does not have fluidity like water,
Regardless of cohesive soil or sandy soil, uniform mixing can be achieved,
It is considered that the tendency for the strength to decrease is small.

Next, the on-site construction after determining the ratio of the added cement amount and the optimum water content ratio as described above will be described.

First, the soft ground is excavated to a predetermined depth by a large-diameter excavator or a shovel, and excess water contained in the mud for excavation or earth and sand is separated on the ground. Sediment after separation is weighed and sent to a mixing device, where a predetermined amount of cement,
Stir mix with ice cubes.

The size of the ice block should be appropriately selected according to the construction scale, the time required for construction, the outside temperature, etc.When the construction scale is relatively small and the temperature is low, the ice with a diameter of about several mm, depending on the case, It is conceivable to use ice blocks with a grain size of up to about 30 mm when snow is used, the scale is large, and the temperature is high.

The treated soil mixed by the mixing device is transferred to a tank and pumped back into the excavated ground for backfilling.

The treated soil hardened by the hydration reaction of the cement component in the backfilled treated soil exerts its strength and the ground improvement is completed.

Claims (13)

(57) [Claims] 1. A method for constructing artificial ground, in which a predetermined amount of water is added to excavated earth or sand and rocks and a cement-based material, and the treated soil is stirred and mixed, and then backfilled and cured.
A method for constructing an artificial ground, characterized in that a part or all of water that needs to be added is replaced with a small ice block and agitated and mixed with the treated soil. 2. The method for constructing an artificial ground according to claim 1, wherein the earth or sand or rock is excavated at an artificial ground constructing site. 3. The method for constructing artificial ground according to claim 1, wherein the earth and sand or rock have been excavated and transported elsewhere. 4. The method for constructing an artificial ground according to claim 1, wherein the earth or sand or rock is used in an excavated state. 5. The method for constructing an artificial ground according to claim 1, wherein as the earth and sand to which the cement-based material is added, a part of the amount of water contained in the earth and sand or muddy water used during excavation is separated and used. 6. The method for constructing artificial ground according to claim 1, wherein the cement-based material is Portland cement. 7. Portland cement is 2 to 10% by weight.
The method for constructing artificial ground according to claim 6, wherein the artificial ground is added. 8. The artificial ground construction method according to claim 1, wherein the cement-based material is gypsum. 9. The method for constructing artificial ground according to claim 1, wherein the cementitious material is lime. 10. The artificial ground construction method according to claim 1, wherein the cement-based material is water glass. 11. The method for constructing artificial ground according to claim 1, wherein the small ice blocks have a particle size of 30 mm or less. 12. A method for constructing artificial ground, in which a predetermined amount of water is added to excavated earth or sand and rocks and cement-based material and stirred and mixed to backfill and harden the treated soil. An artificial ground characterized by forming a hardened ground with a high porosity by replacing the whole with an ice mass with a particle size of 10 mm to 100 mm and mixing with stirring, backfilling the treated soil in the presence of the ice mass, and causing solidification to start. Creation method. 13. The method for constructing artificial ground according to claim 12, wherein the cement-based material is Portland cement.