JP3462701B2 - Method of forming underground structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground columnar body or an underground continuum by stirring and mixing a liquid for consolidation such as cement milk and earth and sand in situ. The present invention relates to a method for forming an underground structure for forming a wall or the like. 2. Description of the Related Art Conventionally, a ground has been excavated while a liquid for consolidation such as cement milk is being injected, and the liquid for consolidation and the excavated in-situ earth and sand have been stirred and mixed. Forming a mid-wall structure has been performed. On the other hand, the soil classification of the ground can be roughly divided into cohesive soil and sandy soil such as sand, gravel and gravel (that is, non-cohesive soil). What they do is common. As described above, when the in-situ earth and sand and the liquid for consolidation are stirred and mixed, the viscous soil layer is often difficult to stir because the viscous soil has an adhesive force. Is more difficult to agitate and mix with the consolidation liquid than the non-cohesive soil layer. The composition and injection amount of the resulting liquid were determined. Thus, in the past, the mixing and injection amount of the consolidation liquid was determined by the viscous soil layer that was difficult to mix, so the water-cement ratio increased,
Injection amount of the consolidating liquid material per soil 1 m ³ also increases, as a result, in the cohesive soil layer, also becomes just good mixed state, in the non-cohesive soil layer, and the amount of water is too much, soil cement However, there is a problem that the material is easily separated from the liquid material for consolidation, and the amount of water and the amount of injection are increased in the whole soil layer, so that the quality is lowered and the amount of generated mud is increased. [0003] The present invention has been made in view of the above-mentioned problems of the prior art, and reduces the amount of water and the amount of injection, reduces the amount of mud generated, and further reduces the quality. It is an object of the present invention to provide a method of forming an underground structure having a uniform quality and a high quality underground structure over the entire length in the vertical direction without inducing. [0004] In order to solve the above-mentioned problems, a method of forming an underground structure according to the present invention provides a method of forming a liquid material for consolidation by excavating the ground while injecting the liquid material for consolidation. In order to form the underground structure 1 by stirring and mixing the excavated in-situ sediment with the excavated in-situ sediment, in the viscous soil layer 2, a consolidation liquid material to which a dispersant is added is injected to mix with the in-situ sediment. Mixing is performed, and in a layer other than the viscous soil layer 2, a liquid for consolidation to which a dispersant is not added is injected and stirred and mixed with in-situ earth and sand. By adopting such a method, even if the mixing and the injection amount of the consolidation liquid are determined by the non-viscous soil layer 3, the viscous soil layer 2
The dispersing effect of the added dispersing agent improves the mixing property between the consolidating liquid and the in-situ earth and sand, thereby improving the quality of the viscous soil layer 2. Since the injection amount can be determined by the non-cohesive soil layer 3,
Since the amount of water can be reduced, the quality of the non-cohesive soil layer 3 is improved, and the injection amount per soil layer can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a first embodiment of the present invention. In forming the underground structure 1 such as an underground pillar or an underground continuous wall in the ground, a liquid for consolidation such as cement milk is injected into the ground using a single-screw or multi-screw excavator. While excavating, the excavated in-situ earth and sand and the injected liquid for consolidation are stirred and mixed, whereby an underground structure 1 such as a so-called soil cement underground structure is formed. Here, in the present invention, when forming the underground structure 1 as described above, when determining the mixing and injection amount of the liquid for consolidation such as cement milk, sand or gravel is used. It is determined based on the non-cohesive soil layer 3 made of sand mixed with gravel or the like. Then, when the non-cohesive soil layer 3 is excavated, the consolidation liquid material having the composition determined based on the non-cohesive soil layer 3 is injected at the injection amount determined as described above. The viscous soil layer 2 is obtained by adding a dispersing agent to the liquid for consolidation having a composition determined based on the non-viscous soil layer 3 as described above. The mixture is injected at the injection amount determined as described above, and is stirred and mixed with the in-situ earth and sand. As an example, the liquid for consolidation in the present invention determined on the basis of the non-cohesive soil layer 3 is, for example,
When the non-cohesive soil is sand mixed with gravel, it is a mixture of 300 kg of cement, 5 kg of bentonite and 600 liters of water (water-cement ratio is 200%).
It is about 550-750 liters / m ³ per m ³ . The liquid material for consolidation having such a composition is injected when the non-viscous soil layer 3 is excavated and stirred and mixed with the in-situ earth and sand.
Further, when the viscous soil layer 2 is excavated and stirred and mixed with the in-situ earth and sand, a dispersant is further added to the liquid for consolidation having the above composition.
The addition of 5 to 6.0 kg is injected when the viscous soil layer 2 is excavated and stirred and mixed with the in-situ earth and sand. The injection amount is the same for both the cohesive soil layer 2 and the non-cohesive soil layer 3. [0008] For comparison, when determining the blending and injection amount of the consolidating liquid based on the clay layer 2 (eg, clay mixed with gravel), 300 kg of cement, 5 kg of bentonite, and 750 liters of water are mixed for comparison. It is necessary to use a liquid for consolidation (water cement ratio is 250%) and inject it at an injection rate of about 850 liters / m ³ per 1 m ³ of the target soil. Therefore, the liquid material for consolidation according to the present invention having the composition and injection amount determined based on the non-cohesive soil layer 3 is better than the composition and injection amount determined based on the cohesive soil layer 2 in the comparative example. The water-cement ratio is smaller than that of the liquid for consolidation, and the injection amount per 1 m ^{3 of} the target soil is smaller. For this reason, in the non-cohesive soil layer 2, the amount of water of the cement milk is reduced and the quality is improved. In addition, in the viscous soil layer 2, the dispersant is added, and as described above, the mixing and injection amount of the liquid for consolidation is determined based on the non-viscous soil layer 3, but the viscous soil layer is determined. In the layer 2, the dispersing action of the added dispersant and the fluidity increasing action improve the mixing property between the consolidating liquid and the in-situ earth and sand, thereby improving the quality of the viscous soil layer 2. In addition, in the whole soil layer, the injection amount per 1 m ³ of the target soil is small, and the generation amount of the mud overflowing on the ground is reduced. In addition, as a dispersing agent, for example, “Geospar K (trade name, manufactured by FPC Inc.)” can be used. [0010] Here, the dispersing agent will be described. The adhesive force of the cohesive soil (that is, the bonding force between the particles of the cohesive soil) is weakened by the dispersing agent to break the binding between the cohesive soil particles, and the cohesive soil layer 2
In order to increase the liquidity. FIG. 1 shows an example of a working example of a method for forming an underground structure according to the present invention. First, prior to construction, a geological survey of the ground where the underground structure is to be formed is performed. The result of this geological survey is generally represented by what is called a "columnar map". As one example is shown in FIG. 2, "column diagram", "geological name", and "N value" are described corresponding to "depth". Now, FIG.
An embodiment in which an underground structure 1 having a depth L is formed in a “columnar diagram” as shown in FIG. L above
In the range, the range in the figure L ₁ is a cohesive soil layer 2 a "layer of gravel-mixed clay", and the scope of drawing L ₂ is a "layer of gravel-mixed sand" non cohesive soil Layer 3. Therefore, first, the blending and the injection amount of the consolidation liquid are determined based on the non-cohesive soil layer 3 (“sand layer mixed with gravel” in the attached drawings). [0011] Then, upon mixing and stirring the sediment and the consolidating liquid material in situ by excavating the ground by the excavator while injecting the consolidating liquid material, as described above in the range of drawing L ₁ Injecting a liquid obtained by adding an appropriate amount of a dispersing agent to the liquid for consolidation determined as described above, and mixing the in-situ soil and liquid for consolidation with stirring (see FIG. 1 (a)). ), and in the range of drawing L _2, injected consolidating liquid material formulation were determined as described above (the one with no added dispersant) situ sediment and consolidating liquid This is to stir and mix the material (see FIG. 1 (b)). In the figure, A is a stirring mixture of the consolidating liquid material to which the dispersing agent is added and the in-situ earth and sand (clay mixed with gravel in the embodiment), and B is the consolidating liquid material to which the dispersing agent is not added. And a stirred mixture of the in-situ earth and sand (sand mixed with gravel in the embodiment). In this case, the injection amount per 1 m ³ of the target soil in the range of L _{1 and} the range of L ₂ is the same. Here, two types of injection ports are provided in the excavator, and one obtained by adding a dispersant to the liquid for consolidation in the viscous soil layer 2 from one injection port is injected into the ground, and the other injection port is used. In the non-cohesive soil layer 3, only the consolidation solution without adding a dispersant may be injected into the ground, and an injection port to be injected into the ground may be selected according to the state of the formation, or Depending on the formation, a dispersant is added to the liquid for consolidation according to the formation, and only the consolidation liquid without adding the dispersant is selectively supplied to the common injection port. It is also possible to select and inject only a consolidation liquid material to which a dispersant is added or a consolidation liquid material to which no dispersant is added. As described above, the excavated earth and sand and the liquid for consolidation are stirred and mixed over the range of the depth L, but the dispersant is added to the viscous soil layer 2 even though the stirring and mixing are difficult. Therefore, the fluidity in the range of L ₁ can be made substantially the same as the fluidity in the range of L ₂ , the stirring and mixing state can be made almost the same, and the underground structure 1 having almost the same strength over the entire length can be formed. is there. By continuously forming the underground structure 1 thus formed, an underground continuous wall can be formed. Not only the cohesive soil layer 2 but also the non-cohesive soil layer 3
It is also conceivable to inject a liquid in which an additive has been added to the liquid for consolidation, but in the non-cohesive soil layer 3, that is, sandy soil, the bond between the soil particles is not originally strong, and it is necessary to add a dispersant. On the contrary, when mixing and stirring with the liquid for consolidation, there is a possibility that the material may be separated, which is difficult to employ. According to the present invention, as described above, the ground is excavated while discharging the consolidation liquid, and the consolidation liquid and the excavated in-situ sediment are stirred. In forming the underground structure by mixing, in the viscous soil layer, a liquid for consolidation to which a dispersant is added is injected and mixed with the in-situ earth and sand,
In layers other than the viscous soil layer, the liquid for consolidation without adding a dispersant is injected and mixed with the earth and sand in situ. In the viscous soil layer, the dispersing action and the fluidity increasing action of the added dispersant improve the mixing property between the consolidating liquid and the in-situ earth and sand, thereby improving the quality of the viscous soil layer. In this way, the composition and injection amount of the liquid for consolidation can be determined by the non-cohesive soil layer, so the amount of water can be reduced, the quality of the non-cohesive soil layer is improved, and It can reduce the amount of injection,
As a result, an underground structure having uniform quality and strength over the entire length in the vertical direction can be formed by a simple method, the amount of mud overflowing on the ground can be reduced, and the disposal cost of mud can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) and 1 (b) are explanatory diagrams showing a construction order of an underground structure according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing an example of the column diagram of the above. [Description of Signs] 1 Underground structure 2 Cohesive soil layer 3 Non-cohesive soil layer

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Claims (1)

(57) [Claims] [Claim 1] Underground structure by excavating the ground while discharging the consolidation liquid, and agitating and mixing the consolidation liquid and the excavated in-situ earth and sand In forming the body, in the viscous soil layer, the liquid for consolidation with the addition of a dispersing agent is injected and mixed with the in-situ earth and sand. A method for forming an underground structure, comprising injecting an object and stirring and mixing with in situ earth and sand.