JPH0224477A - Method and apparatus for recovering stabilizer liquid in mud-water excavation work - Google Patents

Abstract

PURPOSE:To raise the efficiency of treatment as well as shorten treating time by a method in which soil-mixed mud water is screened and passed through a cyclone, and the overflow portion is treated in a sedimentation tank and the underflow portion is treated by a low-speed centrifugal separator. CONSTITUTION:Soil-mixed mud water is screened through a vibrative sieve 20 to remove gravel portion and passed through a cyclone 22 to separate it into an overflow portion and an underflow portion. The overflow portion is sent to a sedimentation tank 24 to remove slime and also to recover mud water as stabilizer liquid. The underflow portion is put into a low-speed centrifugal separator 27 to be operated with 30-400G low-centrifugal forces to recover stabilizer liquid containing only effective mud-water material such as bentonite.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for recovering stable fluid (muddy water) in muddy water excavation methods, etc., and a recovery device suitable for use therein.

[Prior art] In general, in the underground continuous wall construction method or the cast-in-place pile construction method, various muddy water-effective materials such as bentonite are placed in the excavated trench for the purpose of stabilizing the inner wall surface of the excavated trench when excavating the ground. A mud excavation method is used in which the excavation is carried out while being filled with a stabilizing liquid mixed with.

In such a muddy water excavation method, conventionally, in order to separate and recover the stable liquid from the mixed muddy water discharged from the excavation trench, a collection device consisting of a combination of a vibrating sieve, a cyclone, a sand settling tank, etc. has been used. It was being treated as such.

However, due to the low separation ability of this device, it is difficult to sufficiently remove fine soil particles mixed into the stabilizing liquid.Especially, when the excavated ground is a silt or clay layer, the specific gravity of the muddy water increases significantly. This results in a large amount of waste being disposed of as surplus mud. These waste slurries are treated as sludge in industrial waste and must be separated into gravel in a designated location, but it is becoming increasingly difficult to secure a gravel disposal site year by year, and the cost of disposal is extremely high. In addition, since the soil separation ability is low, the recycling efficiency of mud water recovered by separation (
The diversion rate) was also low.

Recently, in order to improve the soil separation ability, a high-speed centrifugal separator (decanter) that can also remove fine soil particles mixed in the muddy water has been added to improve the diversion efficiency of the stable liquid. being done.

FIG. 3 shows an example of the flow of a muddy water treatment process configured using the conventional decanter.

That is, the mixed mud water discharged in the excavation process of Sl (step l) is transported in S2 and applied to the stabilizing liquid recovery device 1. The mixed muddy water is subjected to the processes 83 to S6 in the recovery device 1 to be separated into muddy water and solids such as sand and gravel, and the surplus muddy water is further processed at -37. Then, the collected muddy water, that is, the stabilizing liquid, is replenished with muddy water material in S8, and then is again used as the stabilizing liquid for the excavated trench.

Further, FIG. 4 schematically shows the recovery device 1. As shown in FIG.

According to this device 1, the mixed mud water discharged from the excavation trench H excavated by the excavator is passed through the vibrating sieve 2a to remove sand and gravel.
The mixed mud water that has passed through a and is temporarily stored in the storage tank 3 is supplied to the plurality of cyclones 4. Next, by passing through each of these cyclones 4, the muddy mixed mud is divided into the overflow portion of each cyclone 4 (muddy water from which most of the sand, etc. has been removed from the muddy mixed mud), The overflow is separated into an underflow (muddy water containing most of the sand in the mixed mud), and the overflow is temporarily stored in the first settling tank 5a, where the mixed slime S is sedimented and removed.

On the other hand, the underflow is placed on the vibrating sieve 2a, and passes through the vibrating sieve 2b which is finer than the vibrating sieve 2a to remove sand and the like, and then passes through the vibrating sieve 2a. The liquid is stored in the storage tank 3 and processed again in the cyclone 4.

Then, the overflow muddy water, which is the slime removal muddy water stored in the first sand settling tank 5a, is transferred to a decanter (high-speed centrifuge) that separates fine soil particles.
6, the slime S is sequentially stored in second and third settling tanks 5b and 5c, and the slime S is further sedimented and removed.

Next, a predetermined amount of mud material is replenished from the supply tank 7 to the slime-removed mud water obtained by the third sand settling tank 5c,
It is diverted into the excavated groove H as the final stabilizing liquid.

In addition, 8 in the figure is a grab for removing the solid matter settled in each of the sand settling tanks 5a to 5c.

Here, to explain the structure of the cyclone 4 and decanter 6, the cyclone 4, as shown in FIG. By enclosing the muddy mixture vigorously, a swirling flow is generated, and due to the centrifugal force, the solids contained in the muddy muddy water collide with the inner peripheral wall surface, reduce their kinetic energy, and drop them from the lower discharge port 9a, etc. is the upper tube 1
Discharge from 0 as overflow.

On the other hand, as shown in FIG. 6, the decanter 6 is equipped with a hollow shaft 12 and a screw conveyor 13 that rotates at low speed in a rotating cylindrical casing 11 that is slightly narrowed at the end, and the earth and sand are mixed inside the hollow shaft 12. By sending muddy water and ejecting it from the feed tube 14 into the casing 11 by rotational force, a centrifugal force is applied to the mixed muddy water, and the solids that collide with the inner circumferential wall of the casing 11 and accumulate are discharged by the screw conveyor 13. It is something to do.

The range of particle diameters treated in each process by the recovery device 1 is as shown in FIG. That is, in the process in the vibrating sieve 2a in S3, gravel with a diameter of approximately n+m or more is almost separated, and then in the cyclone 4 in S4,
Fine particles with a diameter of 74 μm or more are almost separated, and solid matter with a diameter of about 1.0 mm or more that has passed through the cyclone 4 is sedimented and separated in the sand settling tank 5a of S5.
In the decanter 6 of No. 6, solid matter up to several μm is almost separated.

In this way, the stable liquid recovery device 1 equipped with the decanter 6, which is a high-speed centrifugal separator, is capable of removing even fine soil particles. It is being reused as a stabilizing liquid by replenishing materials.

[Problems to be Solved by the Invention] By the way, in the above-mentioned conventional stable liquid recovery method and apparatus, in order to recover the stable liquid from the under 70 minute portion of the cyclone 4..., the storage tank 3 and the cyclone 4... . is gradually converted into an overflow by circulating it, and then processed in the decanter 6 and each of the sand settling tanks 5a to 5C, which is time consuming and inefficient.

In addition, although the overflow is treated in the decanter 6 to separate fine soil particles, the conventional decanter 6 has a significantly lower processing capacity of 1/10 or less compared to the previous process in most cases. Although a stabilized liquid with sufficient properties to be reused can be obtained, the amount is extremely small and is only a part of the total amount of muddy water, so it has not been possible to significantly improve the recycling efficiency. Moreover, the centrifugal force is 1000~200
Since it is extremely high, exceeding 0G (G: gravitational acceleration), even the effective ingredients in the stabilizing liquid are removed, making it uneconomical in terms of replenishing muddy water materials.

Therefore, in order to solve the above problem, as shown in Figure 4 above, the separation capacity can be greatly improved by increasing the capacity of the sand settling tanks by installing them in multiple stages (5a to 5C in this case). However, new problems such as increasing the size of the equipment will arise.

The present invention has been made in view of the above-mentioned circumstances, and is a method and method for recovering stabilized liquid that can be effectively and at a high level recovered in muddy water excavation methods, etc., and does not require a large equipment space. The purpose is to provide equipment.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and its method includes removing gravel by sieving muddy water mixed with earth and sand lifted up from an excavation trench. Obtain the removed muddy mixed muddy water, and then pass this mixed muddy water through a cyclone to separate an overflow portion (muddy water containing a small amount of sand in the mixed muddy water) and an underflow portion (muddy mixed muddy water containing a small amount of sand) of the cyclone. The overflow is supplied to a sand settling tank and the slime-removed mud is recovered as a stable liquid.
The method is characterized in that a low centrifugal force of 30 to 400 G is applied to the underflow portion to recover the stable liquid. The device also includes a sieve that removes sand and gravel from the mixed mud that is lifted up from the excavation trench, and a sieve that separates the mixed mud from which the gravel has been removed into the overflow and underflow. A cyclone for separation, a settling tank to which the overflow is supplied and the slime-removed slurry is recovered as a stable liquid, and a sand settling tank to which the underflow is supplied and the underflow is divided into three parts.
It is characterized by being equipped with a low-speed centrifugal separator that applies a low centrifugal force of 0 to 400 G to obtain a stable liquid.

[Function] According to the method and recovery device for stable liquid in the muddy water excavation method and the like of the present invention, mixed muddy water from which gravel has been removed is obtained by sieving the mixed muddy water lifted from the excavation trench. After that, by passing this upper sand i = muddy water through a cyclone, the overflow portion of this cyclone (including a small amount of sand in the mixed muddy water) and the underflow portion (most of the sand in the mixed muddy water) are removed. (including 20%).

Next, the overflow is supplied to a sand settling tank and the slime-removed slurry is recovered as a stable liquid, while a low centrifugal force of 30 to 400 G is applied to the underflow by a low-speed centrifuge. Collect the stabilizing solution.

According to this, the recovery of the stable liquid from the half-flow fraction separated by the cyclone can be done by processing in one sand settling tank, so it is possible to shorten the processing time and reduce the installation space of the entire device. Since the recovery of the stable liquid from the underflow is done in one process using a low-speed centrifuge, the processing time is significantly shortened compared to the conventional method, and the process is very efficient.

In addition, the underflow is removed by a low-speed centrifugal separator.
By applying a low centrifugal force of 400G to 400G, most of the muddy water material is effectively separated into fine particles and stable liquid, and therefore, the recycling efficiency is extremely high, and the processing amount per unit time is also low. increase

Moreover, since the present invention uses a low-speed centrifuge instead of the conventional high-speed centrifuge, it produces less noise and can be operated with a low-output drive, reducing power consumption, making it extremely economical. This will greatly contribute to the development of the construction industry.

[Example code] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 19 indicates a stabilizing liquid recovery device according to the present invention, and reference numeral 11 indicates an excavation trench excavated in the ground by an excavation machine in order to construct an underground continuous wall.

This excavated trench H is excavated while stabilizing the inner wall of the trench by injecting a stabilizing liquid F into the trench. After being excavated to the desired depth, concrete is poured from the bottom of the trench to ground it. The middle wall is constructed. Once the concrete is poured,
The stabilizing liquid F is pushed up against the concrete, becomes muddy water mixed with earth and sand, and is discharged to the outside.

A vibrating sieve 20 is placed on the ground on the side of the excavation trench H to remove sand and gravel from the muddy mixed mud, and the lower part of the vibrating sieve 20 is used to remove the muddy mixed mud that has passed through the vibrating sieve 20. A first storage tank 21 for storing water is installed. Further, above the vibrating sieve 20, several cyclones 22 (in this case, 5 cyclones) are installed.

The vibrating sieve 20 has a function of removing sand and gravel with a particle size of 1 mm or more from the muddy muddy water discharged from the excavation trench H, and the muddy muddy water that has passed through it is stored in the first storage. It falls into the tank 21 and is temporarily stored.

Each of the cyclones 22... has the same configuration as that shown in FIG.
..., the earth and sand mixed mud in the first storage tank 21 is
Water is pumped up and supplied by a pump 23, and the overflow is stored in a sand settling tank 24, and the underflow is stored in a second storage tank 25.Then, the pump 26 stores the water in a decanter 27, which is a low-speed centrifuge. is being supplied to.

In the sand settling tank 24, the fine soil particles mixed in the overflow gradually settle to the bottom, and the slime removal muddy water is
It is stored as an aqueous solution containing only muddy materials such as bentonite, that is, as a stable liquid. This stabilizing liquid is then pumped up by a pump 28 and sent to a recovery line 29 piped to the excavated groove H.

The decanter 27 has the same structure as that shown in FIG. 6, but the rotational force of the hollow shaft inside the casing is G (centrifugal force) when the underflow is spouted against the inner wall of the casing. , 3o to 400G IJF, and its capacity is also large. The underflow portion applied to the decanter 27 is separated into a sand portion S and a stable liquid from which the sand portion S has been removed, and the stable liquid is sent to the recovery line 29.

Also, a replenishment tank 30 in which replenishment muddy material is stored is installed next to the sand settling tank 24 , and the muddy material in this replenishment tank 30 is pumped through a replenishment line 32 by a pump 31 and sent to the recovery line 29 . It is ready to be sent.

Next, a method for recovering a stable liquid from mud mixed with earth and sand discharged from the excavated trench H using the stabilized liquid recovery device 19 having the above configuration, and the effects thereof will be explained.

The mixed mud water discharged from the excavation trench H is passed through a vibrating sieve 2.
0 and passed through this vibrating sieve 20. As a result, the gravel containing the mixed mud with a particle size of 1 mm or more remains on the vibrating sieve 20, and the mixed mud that has passed through this sieve falls into the first storage tank 21 and is stored there.

Next, the mixed muddy water in the first storage tank 21 is pumped up by the pump 23 and branched to each cyclone 22, and is divided into an overflow containing a small amount of sand and an underflow containing most of the sand. It is separated into two parts.

The overflow is supplied to the sand settling tank 24, and the underflow is stored in the second storage tank 25 and then sent to a decanter (low-speed centrifuge) by the pump 26.
27.

In the overflow supplied to the sand settling tank 24, fine soil particles mixed therein gradually settle to the bottom. The slime removal mud in the upper layer becomes a stable liquid, and this stable liquid is pumped up by a pump 28 and sent to a recovery line 29.

On the other hand, the underflow portion supplied to the decanter 27 is effectively separated into fine soil particles and a stabilizing liquid by applying a low centrifugal force of about 30 to 400 G.

Then, this stabilizing liquid is sent to the recovery line 29, and the separated fine soil particles are reused as sand S for an appropriate purpose.

Then, the slurry material in the replenishment tank 30 is brought into the recovery line 29 by the pump 31 via the replenishment line 32 and mixed with the stabilizing liquid passing through the recovery line 29 to form the final product. The stabilized liquid is injected into the excavated trench H again through the recovery line 29.

Note that FIG. 2 shows the flow of the above processing steps.

As described above, according to the method for recovering the stable liquid using the stable liquid recovery device 19, when recovering the stable liquid from the underflow of each cyclone 22, the underflow is treated with the decanter 27. Since the process is performed in one step, the processing time is significantly shortened compared to conventional methods, making it extremely efficient.

In addition, the decanter 27 has 3 parts for the underflow.
By applying a low centrifugal force of about 0 to 400G,
The setting is such that the underflow is effectively separated into fine soil particles and stabilizing liquid, and its capacity is large, making it possible to recover most of the muddy water material contained in the underflow bones. , the recycling efficiency is extremely high, and the throughput per unit time increases dramatically.

Further, since the stabilizing liquid can be recovered from the overflow of each cyclone 22 by processing in one sand settling tank 24, the installation space of the entire apparatus is reduced.

Further, when the underflow is processed by the decanter 27, sand S, which is fine soil particles, can be recovered, and resources can be recycled.

In addition, in the recovery device 19, when excavation work is not being carried out, the stabilizing liquid in the sand settling tank 24 is transferred to the circulation line 33.
and a decanter (low speed centrifuge) using pump 34
27, the amount of stabilizing liquid in the sand settling tank 24 can be increased.

Furthermore, in the above embodiment, the low speed centrifugal separator was explained as the decanter 27, but the low speed centrifuge in the present invention continuously separates solids with a centrifugal force in the above range (30 to 400 G). It is not limited to those having a groove structure like the decanter 27 described above.

[Effects of the Invention] As explained above, according to the method and device for recovering the stabilized liquid in the muddy water excavation method, etc. of the present invention, the method includes sieving the muddy water mixed with earth and sand lifted up from the excavation trench. By applying this method, a muddy water mixture with gravel from which gravel has been removed is obtained.
Next, this mixed muddy water is passed through a cyclone to separate the cyclone overflow portion (muddy water containing a small amount of sand in the mixed muddy water) and underflow portion (muddy water containing most of the sand content in the mixed muddy water). muddy water) and
The overflow is supplied to a sand settling tank and the slime-removed slurry is recovered as a stable liquid, while the stable liquid is recovered by applying a centrifugal force of 30 to 400 G (11) to the underflow. In addition, the device includes a sieve for removing sand and gravel from the mixed mud that is lifted up from the excavation trench, and a sieve that separates the mixed mud from which gravel has been removed by the sieve into the overflow and underflow. a cyclone that separates the overflow, a sand settling tank to which the overflow is supplied and the slime-removed slurry is recovered as a stable liquid, and a sand settling tank to which the underflow is supplied and applies a low centrifugal force of 30 to 400 G to the underflow. Since it is characterized by being equipped with a low-speed centrifuge for additionally obtaining a stable liquid, it has the following effects.

(2) Recovering the stable liquid from the overflow separated by the cyclone can be done by processing in one sand settling tank, thereby reducing the processing time and the installation space of the entire device.

■Recovering the stable liquid from the underflow separated by the cyclone is done in a single process using a low-speed centrifuge, so the processing time is significantly shortened compared to conventional methods, making it extremely efficient. It is.

■The low-speed centrifuge is designed to effectively separate the underflow into fine soil particles and stable liquid by applying a low centrifugal force of about 30 to 400 G to the underflow. Furthermore, since its capacity is large, most of the muddy water materials contained in the underflow bones can be recovered, the recycling efficiency is extremely high, the amount of processing per unit time is increased, and the power consumption is reduced.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of the stable liquid recovery device of the present invention,
Figure 2 is a flow diagram of a method for recovering stable liquid using the apparatus shown in Figure 1, Figure 3 is a flow diagram showing a conventional stable liquid recovery method, Figure 4 is a conventional stabilized liquid recovery apparatus, FIG. 6 is a side sectional view of a cyclone, FIG. 6 is a side sectional view of a decanter, and FIG. 7 is a diagram showing particle diameter ranges for each soil separation method. 19... Stable liquid recovery device, 2o... Vibrating sieve, 22... Cyclone, 24...
... Sand settling tank, 27 ... Decanter (low speed centrifuge), F ... Stabilizing liquid, H ... Excavation groove.

Claims (2)

[Claims] (1) A method for recovering a stable liquid containing only effective mud material such as bentonite as a stabilizing liquid from mud mixed mud lifted from an excavation trench in a mud excavation method, etc., in which the mud mixed mud is sieved. By doing this, mixed mud with gravel is obtained, and then this mixed mud is passed through a cyclone to separate the overflow of the cyclone (the mud containing a small amount of sand in the mixed mud) and the underflow. The overflow is supplied to a settling tank and the slime-removed mud is recovered as a stable liquid, while the underflow is collected as a stable liquid. A method for recovering a stable liquid in a mud excavation method, etc., characterized by recovering the stable liquid by applying a low centrifugal force of 30 to 400G. (2) A device for recovering a stable liquid containing only effective mud materials such as bentonite as a stabilizing liquid from mud mixed mud lifted from an excavation trench in a mud excavation method, etc., which removes gravel from the mud mixed mud. A sieve for removal, a cyclone for separating the mixed mud from which gravel has been removed by the sieve into the overflow portion and the underflow portion, and the overflow portion is supplied and the slime-removed mud is recovered as a stable liquid. A mud water excavation method comprising: a sand settling tank; and a low-speed centrifuge to which the underflow is supplied and which applies a low centrifugal force of 30 to 400 G to obtain a stable liquid. Recovery device for stabilized liquid in etc.