JP5370732B2 - Good liquid production system and method used for mud construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable application even to hardly-applicable ground, and to rapidly produce a good liquid by shortening a waiting time until a fine-grained fraction of excavated soil amounts to a sufficient quantity. <P>SOLUTION: This system 1 for producing the good liquid includes: a sediment separation unit 4 which separates and removes a coarse-grained fraction of excavated sediment from pumped slurry pumped from an excavated ditch 2 excavated by a horizontal multi-spindle excavator 3; a circulation tank 13 for storing the slurry from which the coarse-grained fraction is removed; a decanter 5 for centrifugally separating the slurry in the circulation tank; storage tanks 6 and 7 in which a liquid chemical agent is to be stored; a freshwater tank 24 in which freshwater is to be stored; and a good liquid tank 23 in which the over quantity of slurry discharged from the decanter 5 is to be partially stored together with the liquid chemical agent and the freshwater. At least a part of decanter cake equivalent to the under quantity of slurry discharged from the decanter 5 is added to the slurry in the circulation tank 13. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a good liquid preparation system and method used for a muddy water method such as an underground continuous wall method and an in-situ concrete pouring method.

  In the underground continuous wall method, first, the ground is excavated in a trench shape while preventing the collapse of the groove wall with a mud for excavation called a stabilizing liquid, and then a reinforcing bar is built in the excavation groove. Then, a general procedure is to place concrete in the excavation groove through a tremy tube and replace the excavated mud with concrete.

  In order to stabilize the groove wall, the mud for excavation used in such an underground continuous wall method is basically required to have good wall-forming properties, and in terms of slurry transportation, It is desirable to maintain a low viscosity within a range where liquid escape is prevented. In addition, it is required to have cement resistance because of the concrete replacement in the subsequent process.

  In order to satisfy such a function, conventionally drilling mud using bentonite, CMC, a dispersant, a polymer agent and the like as a mud-making material has been widely used. Such a mud for excavation has a low viscosity maintained because bentonite and the like are well dispersed in the muddy water, and the dispersed bentonite and the like form a good mud cake on the face and the groove wall. Therefore, it becomes possible to secure the water-stopping property and the stability of the face and the groove wall.

  On the other hand, in the underground continuous wall method, fine particles of excavated soil suspend with the components in the excavating mud and settle to the bottom of the groove to form so-called slime, which reduces the quality of underwater concrete. Not only that, it is easily compressed by the load of the placed concrete, which causes a decrease in the bearing capacity and settlement of the underground continuous wall.

  Therefore, depending on the earthquake resistance required for the superstructure and the generation status of the slime, it may be necessary to remove the slime in advance before placing the concrete. However, when the excavation depth is deep, the slime sinks. Since it takes a long time, it is often the case that the mud for excavation in the excavation groove is replaced with newly mud mud.

  According to such a method, since the underwater concrete is cast using a muddy water containing no slime component as a stable liquid, it is possible to construct a high quality underground continuous wall. Such a stabilizing solution is called a good solution.

  Here, the good liquid for replacing the muddy water after completion of excavation is, of course, bentonite, CMC, polymer agent because it is necessary to prevent the groove wall from collapsing as a stabilizing liquid during the placement of underwater concrete. It is made in the same way as the mud for drilling using the mud making material.

  On the other hand, since all the mud-making materials such as bentonite are powders, a mud-planting plant consisting of a stockyard for storing them and a kneading mixer for dissolving them becomes indispensable. If sufficient space cannot be secured on the plant site, the plant configuration becomes complicated and hinders vehicle traffic on the site.

  In addition, since the above-mentioned mud-making material is inherently difficult to dissolve in water, even if a kneading mixer is used, it takes time and labor for the dissolving operation, and as a result, it takes time to produce good liquid.

  Under such circumstances, it is possible to ensure wall-forming by simply adding to the water containing fine particles of excavated soil, and for liquid drilling mud dispersants and drilling muds that do not require labor and time for stirring and mixing. Mud film forming agent was developed.

  According to such a chemical, it is possible to store the tank in a concentrated state because it is liquid, and not only a conventional mud production plant is unnecessary, but also kneading is not required. It is possible to quickly and easily produce a good liquid that can replace all the muddy water.

JP 2002-235073 A

  However, since the above-mentioned drilling mud dispersant and drilling mud film forming agent require a fine part of the excavated soil, when the fine part is not sufficient, for example, excavating ground with less viscous soil. In some cases, it becomes difficult to apply, and as before, there has been a problem that a good liquid must be prepared using a mud-making material such as bentonite, CMC, and polymer agent.

  In addition, when the excavated soil itself is small because it is immediately after the start of excavation, it is necessary to wait until sufficient fine particles are generated, resulting in a problem that the start of good liquid production is delayed.

  The present invention has been made in consideration of the above-described circumstances, and produces a good liquid using a liquid drilling mud dispersant or drilling mud film forming agent even on the ground, which has conventionally been difficult to apply. An object of the present invention is to provide a good liquid preparation system and method for use in a muddy water construction method capable of reducing the waiting time until a fine amount of excavated soil reaches a sufficient amount and quickly producing good liquid. To do.

In order to achieve the above object, the good liquid production system used in the mud construction method according to the present invention fills the excavation hole with the good liquid to be replaced by the concrete placed in the excavation hole. It is a good liquid production system for producing a muddy film forming agent for drilling mud, which exhibits the dispersibility and wall-forming property by adding the water and fine particles of the drilling earth and sand to the fine liquid. In a good liquid production system composed of a liquid chemical consisting of a dispersant for drilling mud,
Separation / removal means for separating and removing coarse particles of excavated sediment from the pumped muddy water pumped from the drilling hole, a circulation tank for storing the muddy water from which the coarse particles have been removed, and the mud water in the circulation tank are centrifuged. A centrifuge for separating, and a good liquid tank in which a portion of the excess of the muddy water discharged from the centrifuge is stored as a good liquid, and the remainder of the over is stored in the circulation tank. The muddy water in the circulation tank is circulated through the excavation hole as a circulating muddy water, and at least a part of the under portion of the muddy water discharged from the centrifugal separator is added to the muddy water in the circulation tank. It is a thing.

Moreover, the good liquid preparation system used for the mud construction method according to the present invention is such that the classification point in the centrifugal separator is about 10 μm.

  Further, the good liquid production system used in the mud construction method according to the present invention includes at least one of a storage tank in which the liquid chemical is stored and a fresh water tank in which fresh water is stored, and at least one of the liquid chemical and the fresh water. It is comprised so that can be thrown into the said good liquid tank.

Moreover, the good liquid preparation method used for the mud construction method according to the present invention is, as described in claim 4 , prepared from the muddy water filled in the excavation hole with the good liquid to be replaced with the concrete cast in the excavation hole. A method for producing good liquid, wherein the mud is finely divided into water and excavated earth and sand, and added to them, a dispersibility and a wall forming property are exhibited. In a method for producing a good liquid composed of a liquid drug comprising:
Separating and removing the coarse particles of excavated sediment from the pumped mud pumped from the drilling hole, storing the mud from which the coarse particles have been removed in a circulation tank, centrifuging the mud in the circulation tank, Among the muddy water discharged by centrifugation, a part of the excess is made a good liquid, while the remainder of the excess is stored in the circulation tank, and the muddy water in the circulation tank is circulated to the excavation hole as a circulation muddy water. In addition, at least a part of the under portion of the mud discharged from the centrifugal separator is added to the mud in the circulation tank.

Moreover, the good liquid preparation method used for the mud construction method according to the present invention is such that the classification point in the centrifugal separation means is about 10 μm.

  Moreover, the good liquid preparation method used for the mud construction method which concerns on this invention adds at least one of the said liquid chemical | medical agent and fresh water to a part of said over.

  Conventionally, it was composed of fine particles of water and excavated earth and sand, and a liquid agent made of a mud film forming agent for drilling mud or a dispersant for drilling mud that exhibits dispersibility and wall-forming properties when added to them. In order to prepare a good liquid from the mud, first, the coarse particles are removed from the pumped mud by separating the sediment from the pumped mud sent from the excavation hole, for example, with a classification point of 75 μm. The muddy water from which the particle content has been removed is centrifuged, for example, at a classification point of 10 μm, so that the muddy water containing only the fine particle content is separated as an over fraction, and this is used as a good solution.

  However, the fine particles contained in the muddy water from which the coarse particles have been removed may be present alone or in a state of adhering to the peripheral surface of soil particles of about several tens of μm. When classified with a size of about 10 μm, it is separated not as an over portion but as an under portion. Incidentally, about 30% of the under portion is occupied by fine particles of 10 μm or less.

  That is, when producing a good liquid using a liquid chemical, although the fine particle content of excavated earth and sand is indispensable, the fine particle content is not used for good liquid production for the reasons described above. It is discarded as part of the cake.

  The Applicant has advanced research and development focusing on whether it is possible to effectively use fine particles that are discarded without being used, and returns the under content generated in the centrifugation step to the drilling hole. Thus, a novel invention has been made in which the fine particles contained in the under portion can be used for producing a good liquid.

  That is, in the good liquid production system and method used in the mud construction method according to the present invention, the mud in the circulation tank is circulated to the excavation hole as the circulation mud, but is discharged from the centrifugal separation means into the mud in the circulation tank. Add at least a portion of the muddy water.

  In this way, even if the fine particles contained in the under part are attached to the soil particles of several tens of μm, they are pumped in the form of being entrained in the circulating mud and put into the excavation hole. In the middle of each process, such as mud from the drilling hole and earth and sand separation, it separates from the tens of μm soil particles and becomes a single fine particle.

  Therefore, for example, when subjected to centrifugation with a classification point of 10 μm, the fine particles are discharged in the form of being included in the over portion. Thus, the fine particles that have been discarded in the form of being included in the under cake are used. Granules can be collected without being discarded, and can be effectively used for producing a good liquid.

  The earth and sand separating means can be composed of a sand and sand separator having a classification point of, for example, about 75 μm, and the centrifugal separating means can be composed of, for example, a decanter having a classification point of 10 μm.

  As long as the liquid chemical is configured to exhibit predetermined dispersibility and wall-forming properties in combination with fine particles of excavated earth and sand, its components are optional, and emphasis is placed on the mud film forming action. Either a mud film forming agent for drilling mud or a dispersant for drilling mud with emphasis placed on the dispersing action may be used, or both of them may be used.

  Further, if the liquid chemical is sufficient when it is added at the time of producing the drilling mud, a part of the excess discharged by centrifugation can be used as a good liquid as it is, and a part of the excess is obtained. If it is necessary to adjust the components, at least one of the liquid chemical and fresh water may be added to a part of the excess.

The whole figure which showed the good liquid preparation system 1 used for the muddy water method concerning this embodiment. The whole figure which showed the good liquid preparation system concerning a modification.

  Embodiments of a good liquid production system and method used in the mud construction method according to the present invention will be described below with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.

  FIG. 1 is an overall view showing a good liquid production system used in the mud construction method according to the present embodiment. As can be seen from the figure, the good liquid production system 1 used in the mud construction method according to the present embodiment is an excavation groove as an excavation hole excavated by a horizontal multi-axis excavator 3 in order to construct an underground continuous wall. Sediment separator 4 as a sediment separating means for separating and removing coarse particles of excavated sediment from the pumped muddy water pumped from 2, a circulation tank 13 for storing mud water from which the coarse particles have been removed, and the circulation tank Among the decanter 5 as a centrifuge for centrifuging the mud in the tank, the storage tanks 6 and 7 for storing the liquid medicine, the fresh water tank 24 for storing fresh water, and the mud discharged from the decanter 5 And a good liquid tank 23 in which a part of the water is stored together with the liquid medicine and fresh water.

  The earth and sand separating device 4 drives coarse pumping mud pump 10 built in the horizontal multi-axis excavator 3 and coarse particles of excavated earth and sand from the pumped mud water pumped from the inside of the excavation groove 2 through the mud pipe 11. In addition to separating and removing the components in the sediment pit 12, the attached cyclone over mud water, for example, mud water from which soil particles of about 75 μm or more are generally removed is stored in the circulation tank 13. It has become.

  The decanter 5 is capable of centrifuging the muddy water stored in the circulation tank 13 and sent via the concentration tank 14 with a classification point of, for example, about 10 μm.

  A pipe 26 is connected to the over mud water discharge port of the decanter 5 and a pipe 28 is branched from the pipe, and the discharge side of the pipe is connected to the circulation tank 13 described above. Is returned to the excavation groove 2 for circulation, and the pipe 26 is connected to the good liquid tank 23 via the valve 27, and the mud containing fine particles of about 10 μm or less. Can be stored in the good liquid tank 23 as a part of the excess.

  The good liquid production system 1 used in the mud construction method according to the present embodiment is separately provided with a chemical dilution fresh water tank 8 and a mixing tank 9, and the storage tank 6 includes a drilling mud mud film forming agent that is a liquid chemical and excavation. Dispersing agent for muddy water is stored in the storage tank 7, and a sodium carbonate (sodium carbonate) aqueous solution, which is also a liquid drug, is stored in the storage tank 7. A pump 15 connected to the storage tank 6 and a pump 17 connected to the storage tank 7. By driving the pumps 19 connected to the chemical dilution fresh water tank 8 respectively, the drilling mud dispersant, the drill mud film forming agent, the sodium carbonate aqueous solution, and the chemical dilution fresh water are connected to the pipe 16, the pipe 18, and the pipe. The mixture is fed to the mixing tank 9 through 20 and mixed in the mixing tank 9 to prepare a mixed solution. The mixing tank 9 may be provided with a stirring mechanism (not shown) as necessary.

  Here, the pump 21 and the pipe 22 are connected to the mixing tank 9 and the tip of the pipe is branched in two directions. The pipe 31 is connected to the one through the valve 29 and the pipe 32 is connected to the other through the valve 30. They are connected to each other, and by opening the valve 29, the mixed liquid is pumped to the excavation groove 2, and by opening the valve 30, the mixed liquid can be added to the good liquid tank 23.

  A fresh water tank 24 is connected to the good liquid tank 23. When the mixed liquid from the mixing tank 9 is added to the over mud water from the decanter 5, it is diluted by adding fresh water to produce a good liquid. In addition, the produced good liquid is supplied into the excavation groove 2 where excavation has been completed through the pipe 34 by driving a pump 33 connected to the good liquid tank 23. .

  Here, the good liquid production system 1 according to the present embodiment adds at least a part of the decanter cake that is an under portion (decanter under) of the muddy water discharged from the decanter 5 to the muddy water in the circulation tank 13. It has become.

The mud film forming agent for drilling mud includes an unsaturated carboxylic acid and / or a salt thereof (a), an unsaturated carboxylic acid (b1) and the following general formula (1)
R (OA) _n OH (1)
R; hydrogen or a hydrocarbon group having 1 to 12 carbon atoms A; an alkylene group having 2 to 4 carbon atoms n; a monoester (b) of a hydroxyl group-containing compound (b2) represented by an integer of 1 to 100 It is comprised with the copolymer (x).

  The mass ratio of the monoester (b) to the copolymer (x) is preferably 1% to 40%. This is because when the mass% of the monoester (b) with respect to the copolymer (x) is less than 1%, the wall-forming property is lowered regardless of the amount of the mud film forming agent for drilling mud, and it exceeds 40%. This is because, when the amount of the mud film forming agent for drilling mud is low, agglomeration may occur and the wall-forming property may deteriorate.

  Further, the number average molecular weight of the copolymer (x) is preferably 5,000 to 100,000. If the number average molecular weight is less than 5000, the wall-forming property is lowered regardless of the amount of the mud film forming agent for drilling mud, and if it exceeds 100,000, the amount of the mud film forming agent for drilling mud is low. This is because agglomeration may occur and the wall-forming property may deteriorate. In addition, about a number average molecular weight, it shall measure with a gel permeation chromatograph.

As an example, a mud film forming agent 41 for drilling mud, in which the unsaturated carboxylic acid and / or its salt (a) is composed of sodium methacrylate salt 42 and the monoester (b) is composed of methoxypolyethylene glycol methacrylate 43, is shown below. .

  On the other hand, the dispersant for drilling mud used in this embodiment can be composed of polyacrylate, polymethacrylate, or a copolymer thereof having a weight average molecular weight Mw of 10,000 to 14,000. For example, it can be composed of a sodium salt of polyacrylic acid having a weight average molecular weight Mw of 10,000 to 14,000. Specifically, a dispersant for a polycarboxylic acid-based stabilizer (hereinafter simply referred to as SS-B) commercially available under the trade name SUPER SLRRY B (manufactured by Sanyo Chemical Industries, Ltd.) can be used.

  In the good liquid production system 1 used for the mud construction method according to the present embodiment, a horizontal multi-axis excavator 3 is used to excavate the excavation groove 2 for constructing an underground continuous wall, and into the excavation groove 2. The filled mud is pumped up from the excavation groove 2, and coarse particles of excavated sediment are separated and removed from the pumped mud by the sediment separator 4 and stored in the circulation tank 13, and the mud in the circulation tank is concentrated. Once stored in the tank 14, it is driven into the decanter 5 and centrifuged, and the excess mud is stored in the circulation tank 13 while the muddy water in the circulation tank 13 is circulated in the excavation groove 2 as the circulating mud. .

  Further, in parallel with the excavation work by such a mud circulation system, the valve 27 is opened as needed so that the excess mud water from the decanter 5 is stored in the good liquid tank 23 as a part of the excess, and the mud for excavation mud water A film forming agent and a drilling mud dispersing agent are mixed with a sodium carbonate aqueous solution and fresh water in the mixing tank 9 to prepare a mixed liquid, and the mixed liquid is added to the good liquid tank 23 so that the good liquid tank 23 Make a good solution.

  In producing the good liquid, by opening the valve 30, the mixed liquid in the mixing tank 9 is added to the over mud water from the decanter 5 stored in the good liquid tank 23, and the fresh water tank 24 is added to the good liquid tank. Dilute appropriately by adding fresh water.

  During excavation, the mud film forming agent for drilling mud, the dispersant for drilling mud, sodium carbonate solution and fresh water are appropriately stirred and mixed in the mixing tank 9, and the mixed liquid is opened in the drilling groove 2 to open the valve 29. By adding to the drilling mud, the drilling mud is replenished or the components are adjusted, and the groove wall of the drilling hole 2 is stabilized.

  After the good liquid is produced, the excavation groove is filled with the good liquid stored in the good liquid tank 23 while the muddy water in the excavation groove 2 is pumped up, for example, from the bottom near the completion of excavation. By supplying it into 2, the muddy water in the excavation groove 2 is replaced with a good liquid.

  In such a good liquid preparation, in the good liquid preparation system 1 used in the muddy water method according to the present embodiment, at least a part of the decanter cake that is an under portion (decanter under) of the muddy water discharged from the decanter 5 is used. It adds to the muddy water in the circulation tank 13.

  In this way, even if the fine particles contained in the decanter cake adhere to the soil particles of several tens of μm, they are pumped in the form of being entrained in the circulating mud, In the middle of each process such as charging, mud from the excavation hole 2 and earth and sand separation by the earth and sand separator 4, it is separated from several tens of μm of earth particles and becomes a single fine particle. Therefore, when the decanter 5 again undergoes centrifugation with a classification point of, for example, 10 μm, the fine particles are discharged in a form contained in the over mud water.

  That is, the fine granule originally contained in the decanter cake is recovered as an over fraction in the second or subsequent centrifugation, so that the over mud containing the fine granule is contained by opening the valve 27 as appropriate. Is stored in the good liquid tank 23, and then the good liquid is prepared by the procedure described above.

  As described above, according to the good liquid production system 1 and the method used in the mud construction method according to the present embodiment, the mud in the circulation tank 13 is circulated when the mud in the circulation tank 13 is circulated to the excavation hole 2 as the circulation mud. In addition, since at least a part of the decanter cake discharged from the decanter 5 is added, even if the fine particles contained in the decanter cake adhere to the soil particles of several tens of μm. Thus, when the decanter 5 is centrifuged again with a classification point of, for example, 10 μm, the fine particles are discharged in a form included in the decanter over. The good liquid tank 23 is stored.

  Therefore, it becomes possible to collect a larger amount of fine particles from the excavated soil and supply the collected fine particles to the good liquid tank 23. Thus, in the ground that is difficult to apply because there is little viscous soil. Even if there is, it is possible to reliably collect a small amount of viscous soil, so that the range of applicable ground can be expanded, and the waiting time from the start of excavation to the operation of the decanter 5 can be shortened. It becomes possible to produce it promptly.

  In addition, according to the good liquid production system 1 and method used in the mud construction method according to the present embodiment, the storage tanks 6 and 7 and the fresh water tank 24 are provided. The agent and the drilling mud dispersant can be replenished at a desired concentration, or the over mud can be diluted.

  In addition, as a secondary effect of recovering more fine particles from excavated soil and using them effectively for producing good liquid, it is possible to reduce the volume of the decanter cake that is discharged, making it more environmentally friendly. Corresponding excavation work can be performed.

  In the present embodiment, the mud film forming agent for drilling mud and the dispersant for drilling mud are stored in the storage tank 6, but if cement resistance can be secured only by the mud film forming agent for drilling mud, The dispersant for drilling mud may be omitted.

  In the present embodiment, the mud film forming agent for drilling mud and the dispersant for drilling mud are used in combination, and these are stored in the storage tank 6. Since it has dispersibility and wall-forming property, depending on the case, either one may be used alone. On the other hand, when the mud film forming agent for drilling mud and the dispersant for drilling mud are used in combination, they may be stored in the storage tank 6 in a mixed state. It doesn't matter. In this case, a total of two storage tanks 6 are provided.

  Moreover, in this embodiment, the diluting fresh water tank 8 and the mixing tank 9 are provided on the assumption that the mud film forming agent for drilling mud and the dispersant for drilling mud are diluted. The chemical dilution fresh water tank 8 and the mixing tank 9 may be omitted as long as the quality related to the added amount can be ensured even if added.

  Further, in this embodiment, the storage tank 7 is provided to store the sodium carbonate aqueous solution in the tank, but the dispersion of the cement mud is sufficiently suppressed by the drilling mud dispersant used in this embodiment. If it is possible, the storage tank 7 may be omitted.

  In the present embodiment, the excess mud from the decanter 5 is stored in the good liquid tank 23 as a part of the excess, and the mud film forming agent for drilling mud and the dispersant for drilling mud are added to the good liquid tank 23. However, the above-mentioned chemicals are added to stabilize the groove wall during excavation and are also included in the over mud water from the decanter 5.

  Therefore, if it is not necessary to adjust the components during preparation of the good liquid, it is possible to directly make the over mud from the decanter 5 a good liquid, and the above-mentioned chemicals can be added to the over mud from the decanter 5, There is no need to add fresh water to dilute the over mud.

  In such a modification, it is not necessary to connect the storage tanks 6 and 7, the chemical dilution fresh water tank 8 and the mixing tank 9 to the good liquid tank 23, and the fresh water tank 24 can be omitted.

  FIG. 2 shows an example in which the storage tanks 6 and 7, the chemical dilution fresh water tank 8 and the mixing tank 9 are connected only to the excavation hole 2, and the fresh water tank 24 is omitted, omitting the valve 30 and the pipe 32. Is.

  In the present embodiment, the concentration tank 14 is provided. However, in some cases, this may be omitted, and the muddy water in the circulation tank 13 may be directly driven into the decanter 5.

  The mud film forming agent for drilling mud and the dispersant for drilling mud according to the present invention are those that are configured to have a predetermined dispersibility and wall-forming property in combination with fine particles of the drilling mud. The component is arbitrary and things other than the above-mentioned embodiment can be employ | adopted suitably.

  For example, it comprises a single polymer as a (co) polymer (x ′) having an unsaturated carboxylic acid and / or salt (a) as a main constituent unit, and the weight average molecular weight Mw of the single polymer is 200,000 to The mud film forming agent for drilling mud can be used in an amount of 3 million, desirably 500,000 to 2.5 million, more desirably 500,000 to 1,000,000, and particularly desirably 600,000 to 800,000. The unsaturated carboxylic acid and / or its salt (a) may be composed of, for example, sodium acrylate.

An example of a mud film forming agent 51 for drilling mud, which is composed of an unsaturated carboxylic acid and / or its salt (a) with sodium acrylate 52, is shown below.

1 Good liquid production system used for mud construction method 2 Drilling groove (drilling hole)
4 earth and sand separator (earth and sand separating means)
5 Decanter (centrifugation means)
6 Storage tank 13 Circulation tank 23 Good liquid tank 24 Fresh water tank

Claims (6)

A good liquid production system for producing a good liquid to be replaced with concrete placed in a drilling hole from a muddy water filled in the drilling hole, wherein the muddy water is added to water, fine particles of excavated earth and sand, and added to them. In a good liquid production system composed of a mud film forming agent for drilling mud or a liquid agent comprising a dispersant for drilling mud, which exhibits dispersibility and wall-forming property,
Separation / removal means for separating and removing coarse particles of excavated sediment from the pumped muddy water pumped from the drilling hole, a circulation tank for storing the muddy water from which the coarse particles have been removed, and the mud water in the circulation tank are centrifuged. A centrifuge for separating, and a good liquid tank in which a portion of the excess of the muddy water discharged from the centrifuge is stored as a good liquid, and the remainder of the over is stored in the circulation tank. The muddy water in the circulation tank is circulated through the excavation hole as a circulating muddy water, and at least a part of the under portion of the muddy water discharged from the centrifugal separator is added to the muddy water in the circulation tank. A good liquid production system used in the muddy water construction method. The good liquid preparation system used for the mud construction method according to claim 1, wherein a classification point in the centrifugal separation means is about 10 μm. 2. A configuration comprising at least one of a storage tank in which the liquid medicine is stored and a fresh water tank in which fresh water is stored, and at least one of the liquid medicine and the fresh water can be charged into the good liquid tank. Or the good liquid preparation system used for the mud construction method of Claim 2 . A method for producing good liquid from muddy water filled in the excavation hole, wherein the good liquid to be replaced with concrete placed in the excavation hole is added to the fine particles of water and excavated earth and sand In the method for producing a good liquid composed of a mud film forming agent for drilling mud or a liquid agent comprising a dispersant for drilling mud, which exhibits dispersibility and wall-forming property,
Separating and removing the coarse particles of excavated sediment from the pumped mud pumped from the drilling hole, storing the mud from which the coarse particles have been removed in a circulation tank, centrifuging the mud in the circulation tank, Among the muddy water discharged by centrifugation, a part of the excess is made a good liquid, while the remainder of the excess is stored in the circulation tank, and the muddy water in the circulation tank is circulated to the excavation hole as a circulation muddy water. And a good liquid preparation method used in the muddy water method, wherein at least part of the underwater is added to the muddy water in the circulation tank among the muddy water discharged from the centrifugal separator. The method for preparing good liquid used in the muddy water method according to claim 4, wherein the classification point in the centrifugal separation means is about 10 µm. The method for producing a good liquid used in the mud construction method according to claim 4 or 5 , wherein at least one of the liquid chemical and fresh water is added to a part of the excess.

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