JP2717145B2 - Method and apparatus for collecting stable liquid in muddy water drilling method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for recovering a stable liquid (muddy water) in a muddy water excavation method or the like, and a recovery device suitable for use therein.

[Prior Art] Generally, in the underground continuous wall method or the cast-in-place pile method, various effective muddy water materials such as bentonite are provided in the excavation groove for the purpose of stabilizing the inner wall surface of the excavation groove when excavating the ground. The muddy water excavation method is performed while filling with a stable liquid mixed with water.

And, in such a muddy water excavation method, conventionally, in order to separate and collect the stable liquid from the earth and sand mixed muddy water discharged from the excavation ditch, a recovery device including a combination of a vibrating sieve, a cyclone, a sand basin and the like is used. Had been done.

However, this device has a low resolution,
It is difficult to sufficiently remove the fine soil particles mixed in the stabilizing solution. Particularly, when the excavated ground is a silt or clay layer, the specific gravity of the muddy water increases remarkably, and a large amount of excess muddy water is discarded. These waste muds are treated as sludge in industrial waste and must be disposed of at a designated place. However, it is becoming increasingly difficult to secure a disposal place every year, and the disposal cost is extremely high. In addition, due to the low sediment separation ability, the efficiency of circulating the mud collected by separation (diversion rate) was low.

Therefore, recently, in order to enhance sediment separation performance, a high-speed centrifuge (decanter) that can also remove fine soil particles mixed in muddy water has been added to improve the conversion efficiency of stable liquid. It has been done.

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

That is, the mixed muddy water discharged in the excavation step of S1 (step 1) is transported in S2 and is applied to the stable liquid recovery apparatus 1. The mixed muddy water is subjected to the processing of S3 to S6 in the recovery device 1 so that
The mud is separated into solids such as earth and sand, and the excess mud is further treated in S7. Then, the collected muddy water, that is, the stable liquid, is supplied with the muddy water material in S8, and is diverted again as the stable liquid in the excavation trench.

FIG. 4 schematically shows the recovery device 1.

According to this device 1, the mixed muddy water discharged from the excavation groove H excavated by the excavation groove D is subjected to the vibrating sieve 2a to remove the gravel, and the vibrating sieve 2a
And the muddy water mixed with soil once stored in the storage tank 3
It is supplied to a plurality of cyclones 4. Then, the sediment-mixed muddy water is passed through each of the cyclones 4..., And the underflow component (muddy water in which most of the sand and the like are removed from the sediment-mixed muddy water) and the underflow component ( And the overflow is temporarily stored in the first sand settling tank 5a, and the mixed slime S is settled and removed.

On the other hand, the underflow portion is disposed on the vibrating sieve 2a, and after sand and the like are removed by passing through the vibrating sieve 2b having a smaller size than the vibrating sieve 2a, the underflow portion passes through the vibrating sieve 2a. Are stored in the storage tank 3 and processed again by the cyclones 4.

A decanter (high-speed centrifugal separator) that separates fine soil particles by the earth and sand mixed muddy water that is the slime-removing muddy water for the overflow stored in the first sand settling tank 5a.
After being subjected to 6, the slime S is sequentially stored in the second and third settling tanks 5b and 5c, and the slime S is settled and removed.

Then, a predetermined amount of muddy material is supplied from the replenishing tank 7 to the slime-removed muddy water obtained by the third sedimentation tank 5c,
It is diverted into the above-mentioned excavation groove H as a final stable liquid.

In addition, 8 in the figure is a glove for removing solids settled in each of the sand setting tanks 5a to 5c.

Here, the structure of the cyclone 4 and the decanter 6 will be described. As shown in FIG. By vigorously enclosing the muddy water, a swirling flow is generated, and due to the centrifugal force action, solids contained in the sediment-mixed muddy water collide with the inner peripheral wall surface, reduce kinetic energy and drop from the lower outlet 9a, Upper tube 10
And discharged as overflow.

On the other hand, as shown in FIG. 6, the decanter 6 is provided with a hollow shaft 12 and a screw conveyor 13 rotating at a low speed in a rotating cylindrical casing 11 having one end slightly narrowed. Send it to the feed tube
A centrifugal force is applied to the mud mixed with earth and sand by being spouted out of the casing 11 into the casing 11 by a rotational force, and the solid matter that has collided with the inner peripheral wall of the casing 11 and deposited has a screw conveyor.
It is to be discharged at 13.

The range of the processing particle diameter in each step by the above-mentioned recovery apparatus 1 is as shown in FIG. That is, in the treatment in the vibrating sieve 2a in S3, sand and gravel having a diameter of about 1 mm or more are almost separated, and then in the cyclones 4 in S4, fine particles having a diameter of 74 μm or more are substantially separated. The passed solid matter having a diameter of about 1.0 mm or more is settled and separated in the sand settling tank 5a of S5.
m are substantially separated.

As described above, in the stable liquid recovery device 1 including the decanter 6 as the high-speed centrifuge, since it is possible to remove even fine soil particles, muddy water (stable liquid) passing through the decanter 6 is muddy water. By replenishing the material, it is diverted again as a stable liquid.

[Problems to be Solved by the Invention] In the above-described conventional method and apparatus for collecting a stable liquid, in order to recover the stable liquid from the underflow portion of the cyclones 4, the storage tank 3 and the cyclones 4 are circulated. Is gradually converted into an overflow portion, and then is processed by the decanter 6 and each of the sand setting tanks 5a to 5c. Therefore, it takes time and is not efficient.

In addition, although the overflow portion separates fine soil particles by being treated in the decanter 6, the conventional decanter 6 has a remarkably low processing capacity of 1/10 or less in most cases with respect to the previous step. Although a stable liquid having properties sufficient to be diverted can be obtained, the amount thereof is a part of the total muddy water and is extremely small, so that the recycle efficiency has not been significantly improved. In addition, since the centrifugal force is extremely high, ie, 1000 to 2000 G (G: gravitational acceleration) or more, even the effective components in the stabilizing solution are removed, which is uneconomical in terms of replenishing muddy water materials.

Therefore, as shown in Fig. 4 above, in order to solve the above problem, the sedimentation tank is installed in multiple stages (in this case, 5a to 5c) and the capacity is increased, thereby greatly improving the separation ability. However, a new problem such as an increase in the size of the equipment occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to effectively and at a high level recover a stable liquid in a muddy water excavation method or the like, and furthermore, a method and a method for recovering a stable liquid that does not require a large equipment space. It is intended to provide a device.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and the method is as follows. Obtain the removed sediment-mixed mud, and then pass this sediment-mixed mud through a cyclone to convert the mud containing a small amount of sand in the sediment-mixed mud into overflow, and to remove most of the sand in the mud Separating the underflow component into a settling tank and collecting the slime-removed mud fluid as a stable liquid, while separating the underflow component into a cylindrical rotating casing having one end slightly narrowed. Inside, a low-speed centrifuge having a hollow shaft rotating in the same direction as the rotating casing and a screw conveyor integrally provided around the hollow shaft, The solid is ejected from the hollow shaft into the rotating casing to give a low centrifugal force of 30 to 400 G, and solid matter such as earth and sand that has collided with the rotating casing and settled at the bottom is continuously discharged from one end of the rotating casing by a screw conveyor. In addition, the stable liquid is continuously discharged from the other end of the rotary casing to collect only the stable liquid. In addition, as a device, a sieve for removing gravel from mud mixed with sediment lifted from a digging trench, a mud mixed with mud removed from the mud by the sieve, and a trace amount of sand in the mixed muddy water. A cyclone for separating the mud containing the overflow as an overflow, separating the mud containing the most sand in the earth and sand mixed mud as an underflow, and a settling tank in which the overflow is supplied and the slime-removed mud is collected as a stable liquid. A cylindrical rotating casing having one end slightly narrowed, a hollow shaft rotating in the same direction as the rotating casing, and a screw conveyor provided integrally therearound, and the underflow component is removed from the hollow shaft. A low centrifugal force of 30 to 400 G is given to the underflow by jetting into the rotating casing, and the sediment that has settled to the lower part due to collision with the rotating casing The solid is characterized by comprising a low-speed centrifuge for continuously discharging the stabilizing solution while continuously discharged from one end of the rotating casing with a screw conveyor from the other end of the rotating casing.

[Function] According to the present invention, according to the method and apparatus for collecting a stable liquid in a muddy water excavation method or the like, the mixed muddy water from which the gravel is removed is obtained by sieving the mixed muddy water that is lifted from the excavation trench. After that, by passing the mixed muddy water through a cyclone, the muddy water containing a small amount of sand in the mixed muddy water is made into an overflow, and separated as a muddy water underflow containing most sandy matter in the mixed muddy water. . Next, the overflow is supplied to a sand settling tank, and the slime-removed muddy water is recovered as a stable liquid. On the other hand, the underflow is subjected to 30 to 400 G by a low-speed centrifuge.
A low centrifugal force is applied to recover the stable liquid.

According to this, the recovery of the stable liquid from the overflow separated by the cyclone can be performed by the treatment in one settling tank, so that the treatment time can be reduced and the installation space of the entire apparatus can be reduced. Since the recovery of the stable liquid from the flow is performed in a single step of processing using a low-speed centrifuge, the processing time is greatly reduced compared to the conventional method, and the method is very efficient.

In addition, the amount of underflow is 30
By applying a low centrifugal force of 400 G to 400 G, it is effectively separated into fine soil particles and a stable liquid, and most of the muddy material is recovered. Increase.

Moreover, in the present invention, instead of the conventional high-speed centrifuge, low-speed centrifugal separation is performed by applying a low centrifugal force of 30 to 400 G to the underflow, discharging solid matter such as sediment, and collecting only the stable liquid. Because the machine is used, there is little noise,
In addition, since the operation can be performed by the low-output driving device, the power consumption can be reduced. Therefore, it is very economical and greatly contributes to the development of the construction industry.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 19 denotes a stabilizer recovering apparatus according to the present invention, and H denotes a digging trench excavated by a digging machine D in a ground L for constructing an underground continuous wall.

The excavation groove H is excavated by injecting a stabilizing liquid F into the groove to stabilize the inner wall of the groove, and after being excavated to a desired depth, concrete is poured from the bottom of the excavation groove and ground. An inner wall is built. When the concrete is poured, the stabilizing liquid F is pushed up to the concrete, and is discharged as muddy water mixed with earth and sand.

On the ground L on the side of the excavation groove H, a vibrating sieve 20 for removing gravel in the mud mixed with muddy water is arranged. Below the vibrating sieve 20, muddy mud passing through the vibrating sieve 20 is supplied. A first storage tank 21 for storing is provided. Further, a plurality of cyclones 22 (five in this case) are installed above the vibrating sieve 20.

The vibrating sieve 20 has a function of removing sand and gravel having a particle size of 1 mm or more from the sediment mixed mud discharged from the excavation groove H. The sediment mixed mud passing therethrough is subjected to 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 mixed muddy water in the first storage tank 21 is pumped up by a pump 23 and supplied, and the overflow is settled in a sand settling tank 24.
In addition, after the underflow is once stored in the second storage tank 25, it is supplied to a pump 26 to a decanter 27 which is a low-speed centrifuge.

In the settling tank 24, the fine soil particles mixed into the overflow gradually settle to the bottom, and the slime-removed muddy water,
It is stored as an aqueous solution containing only muddy water materials such as bentonite, that is, a stable liquid. The stable liquid is pumped by a pump 28 and sent to a recovery line 29 provided in the excavation groove H.

The decanter 27 has the same configuration as that shown in FIG. 6, but the rotational force of the hollow shaft in the casing is G (centrifugal force) when the underflow is ejected to the inner wall of the casing. , 30 to 400G, and its capacity is also large. And
The underflow applied to the decanter 27 is separated into sand S and a stable liquid from which the sand S has been removed, and the stable liquid is sent to the recovery line 29.

A replenishing tank 30 in which replenishing mud material is stored is installed next to the sedimentation tank 24, and the mud material in the replenishing tank 30 is pumped up a replenishing line 32 by a pump 31 and is sent to the collecting line 29. It is being sent.

Next, a method of recovering the stable liquid from the mixed muddy water discharged from the excavation trench H using the stable liquid recovery apparatus 19 having the above-described configuration, and an operation associated therewith will be described.

The mixed muddy water discharged from the excavation trench H is
Conveyed over the vibrating sieve 20. As a result, the sand and gravel having a particle size of 1 mm or more contained in the mixed sediment remains on the vibrating sieve 20, and the mixed sediment that has passed through falls into the first storage tank 21 and is stored therein.

Then, the mixed muddy water in the first storage tank 21 is pumped.
The water is pumped by 23 and is branched and supplied to each cyclone 22..., And is separated into an overflow containing a small amount of sand and an underflow containing most sand.

The overflow is supplied to a sedimentation tank 24, and the underflow is temporarily stored in a second storage tank 25 and then decanted (low-speed centrifuge) 27 by a pump 26.
Supplied to

In the overflow portion supplied to the sedimentation tank 24, fine soil particles mixed therein gradually settle to the bottom. Then, the slime-removed mud in the upper layer becomes a stable liquid, and this stable liquid is pumped by a pump 28 and sent to a recovery line 29.

On the other hand, the underflow component supplied to the decanter 27 is effectively separated into fine soil particles and a stable liquid by applying a low centrifugal force of about 30 to 400 G. Then, this stable liquid is sent to the recovery line 29, and the separated fine soil particles are reused as sand S as appropriate.

Then, the muddy water material in the replenishing tank 30 is joined to the collecting line 29 via the replenishing line 32 by the pump 31 and mixed with the stable liquid passing through the collecting line 29. It is made into a stable liquid, and is again injected into the excavation groove H through the recovery line 29.

 FIG. 2 shows the flow of the above-mentioned processing steps.

As described above, according to the method for recovering the stable liquid using the stable liquid recovery apparatus 19, in recovering the stable liquid from the underflow of each cyclone 22,... Since the process is performed in a process, the processing time is greatly shortened as compared with the related art, and the process is very efficient.

The decanter 27 is 30
By applying a low centrifugal force of about 400 G to about 400 G, the underflow component is set to be effectively separated into fine soil particles and the stabilizing solution, and further, since its capacity is large, the underflow component is included in the underflow component. Most of the contained muddy water material can be recovered, and as a result, the recycling efficiency is extremely high,
The throughput per unit time also increases dramatically.

In addition, when the stable liquid is recovered from the overflow of each cyclone 22..., The processing can be performed by one sand settling tank 24, so that the installation space of the entire apparatus is reduced.

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

In the above-mentioned recovery device 19, when no excavation work is performed, the stable liquid in the sand settling tank 24 is repeatedly processed by a decanter (low-speed centrifuge) 27 using a circulation line 33 and a pump 34. Thus, the amount of the stabilizing liquid in the sedimentation tank 24 can be increased.

In the above embodiment, the low-speed centrifuge was described as the decanter 27. However, the low-speed centrifuge in the present invention is capable of continuously separating solids with the above-mentioned range (30 to 400 G) of centrifugal force. Said decanter 27
However, the present invention is not limited to those having the structure as described above.

[Effects of the Invention] As described above, according to the method and apparatus for recovering a stable liquid in the muddy water excavation method of the present invention, the method is as follows. Thus, the mixed muddy water from which the gravel is removed is obtained, and then the mixed muddy water is passed through a cyclone to overflow the cyclone (muddy water containing a small amount of sand in the mixed muddy water) and underflow. Fraction (mud containing most of the sand in the mud mixed with earth and sand), and the overflow is supplied to a sedimentation tank to collect the slime-removed mud as a stable liquid. It is characterized by recovering the stable liquid by applying a low centrifugal force of 30 to 400G. And a cyclone for separating the sediment-mixed muddy water from which the gravel was removed by the sieve into the overflow and the underflow, and a sediment where the overflow is supplied and the slime-removed mud is recovered as a stable liquid. A tank and a low-speed centrifugal separator that is supplied with the underflow component and applies a low centrifugal force of 30 to 400 G to the underflow component to obtain a stable liquid. It has a great effect.

The recovery of the stable liquid from the overflow separated by the cyclone can be performed by processing in one sand tank, so that the processing time can be reduced and the installation space of the entire apparatus can be reduced.

Since the recovery of the stable liquid from the underflow separated by the cyclone is performed in a single step of processing with a low-speed centrifuge, the processing time is greatly reduced as compared with the conventional method, which is very efficient. is there.

The low-speed centrifuge is set so that the underflow component is effectively separated into fine soil particles and a stable liquid by giving a low centrifugal force of about 30 to 400 G to the underflow component. Because of its large capacity, most of the muddy material contained in the underflow can be recovered, the circulating use efficiency is extremely high, the throughput per unit time increases, and the power consumption further decreases.
Moreover, unlike low-speed centrifuges, which are different from so-called badge-type separators, in which solids are accumulated inside, the separated solids and the stable liquid are each continuously discharged, so the apparatus is stopped to remove the solids. There is no need to increase the efficiency of the collection operation.

[Brief description of the drawings]

FIG. 1 is a view showing the overall configuration of a stable liquid recovery apparatus of the present invention,
FIG. 2 is a flowchart of a method for recovering a stable liquid using the apparatus shown in FIG. 1, FIG. 3 is a flowchart showing a conventional method for recovering a stable liquid, FIG. FIG. 6 is a sectional side view of a cyclone, FIG. 6 is a sectional side view of a decanter, and FIG. 19: Stable liquid recovery device, 20: Vibrating sieve, 22: Cyclone, 24: Sand settling tank, 27: Decanter (low-speed centrifuge), F: Stable liquid, H: Drilling groove.

Claims (2)

(57) [Claims] 1. A method for recovering a stable liquid containing only effective mud material such as bentonite as a stable liquid from a mixed muddy water lifted from a digging trench in a muddy water excavation method or the like, wherein the mixed muddy water is sieved. To obtain muddy water from which sediments have been removed, and then pass this muddy muddy water through a cyclone to convert the muddy water containing a small amount of sand in the muddy muddy water into an overflow, thereby increasing the amount of muddy water in the muddy muddy water. The muddy water containing a portion of sand is separated as an underflow, the overflow is supplied to a sand settling tank, and the slime-removed muddy water is collected as a stable liquid, while the underflow is slightly constricted at one end. A cylindrical rotating casing having a hollow shaft rotating in the same direction as the rotating casing and a screw conveyor integrally provided therearound. The centrifugal separator separates the underflow into the rotary casing from the hollow shaft to give a low centrifugal force of 30 to 400 G. A method for recovering a stable liquid in a muddy water excavation method or the like, comprising continuously discharging the stable liquid from one end of the rotary casing and continuously recovering the stable liquid from the other end of the rotary casing. 2. A device for recovering a stable liquid containing only effective mud material such as bentonite as a stable liquid from mud mixed with soil lifted from a digging trench in a mud drilling method or the like. The sediment-mixed mud with the gravel removed by this sieve, the mud containing a small amount of sand in the sediment-mixed mud is defined as the overflow, and most of the sand in the mud is mixed A cyclone for separating muddy water as an underflow, a sedimentation tank for supplying the overflow and recovering the slime-removed muddy water as a stabilizing solution, and a rotary casing in a cylindrical rotary casing having one end slightly narrowed. A hollow shaft rotating in the same direction as the above, and a screw conveyor integrally provided around the hollow shaft. A low centrifugal force of 30 to 400 G is applied to the underflow by ejecting the underflow, and solids such as earth and sand that have collided with the rotating casing and settled to the lower portion are continuously discharged from one end of the rotating casing by a screw conveyor. An apparatus for collecting a stable liquid in a muddy water excavation method or the like, comprising: a low-speed centrifuge that continuously discharges the stable liquid from the other end of the rotary casing.