JPH0224478A - Method and apparatus for recovering stabilizer liquid in mud-water excavation work - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for recovering a stabilizing liquid 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 types of muddy water such as pentonite are poured into the excavated trench in order to stabilize the inner wall surface of the excavated trench when excavating the ground. A mud water excavation method is used in which the excavation is carried out while being filled with a stabilizing liquid mixed with materials.

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 muddy waters are treated as sludge in industrial waste and must be disposed of in a designated location, but it is becoming increasingly difficult to secure a disposal location 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 a muddy water treatment process 70- that includes a conventional decanter.

That is, the muddy water mixed with earth and sand discharged in the excavation process of S1 (step 1) is transported in S2 and applied to the stable liquid recovery device 1. The muddy water mixed with earth and sand is collected using a recovery device.
By performing the processing in steps 53 to S6, the muddy water is separated into solid matter such as sand and gravel, and the muddy water is further processed in step S7 to remove excess muddy water. 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 of each cyclone 4 (the muddy water from which most of the sand has been removed from the muddy mixed mud) and the underflow. 70-min (muddy water containing most of the sand in the mixed mud), and the overflow part is
Once stored in the first sand settling tank 5a, the mixed slime S is sedimented and removed.

On the other hand, the under 70-min. is placed on the vibrating sieve 2a, and after passing through the vibrating sieve 2b which is finer than the vibrating sieve 2a to remove sand and the like,
passes through the vibrating sieve 2a and is stored in the storage tank 3;
It is processed again in each cyclone 4.e.

Then, the slime removal slurry for 70 minutes stored in the first sand settling tank 5a is applied to a decanter 6 for separating fine soil particles, and then transferred to the second and third sand settling tanks 5b.
, 5c, and the slime S is further sedimented and removed.

Next, a predetermined amount of mud water material is replenished from the replenishment tank 7 to the Sufim-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, as shown in FIG. By forcefully enclosing the muddy water, a swirling flow is generated, and due to the centrifugal force, the solids contained in the mixed muddy water collide with the inner peripheral wall surface, reduce their kinetic energy, and fall from the lower discharge port 9a. upper tube
It is discharged from O as an overflow.

On the other hand, as shown in FIG. 6, the decanter 6 has a hollow shaft 12,
and a screw conveyor 13 rotating at low speed,
The mixed mud is fed into the hollow shaft 12 and is ejected from the feed tube 14 into the casing 11 by rotational force, thereby applying centrifugal force to the mixed mud, which collides with the inner circumferential wall of the casing 11 and deposits solids. is discharged by a screw conveyor 13.

The range of particle diameters treated in each process by the recovery device 11 is as shown in FIG. That is, in the process using the vibrating sieve in S3, most of the sand and gravel with a diameter of about 1 square inch or more are separated, and then in the cyclone in S4, fine particles with a diameter of 74 #1 or more are almost separated, and furthermore, the particles that have passed through the cyclone are separated. Solids having a diameter of about 1.0 mm or more are sedimented and separated in the sand settling tank 4 at 55, and most of the solids up to several servings are separated in the decanter 5 at S6.

In this way, in a device equipped with a high-speed decanter, it is possible to remove even the finest soil particles, so the muddy water that has passed through the decanter is reused as a stabilizing liquid by replenishing the muddy water material.

[Problems to be Solved by the Invention] Incidentally, in the conventional stable liquid recovery method and device described above, although the overflow obtained by the cyclone 5 is passed through the decanter 6 to separate fine soil particles, Compared to the previous process, this conventional decanter 6 has a significantly lower processing capacity of 1710 or less in most cases, and although a stable liquid with sufficient properties to be reused is obtained, the amount is only a part of the total amount of muddy water. Since the amount is extremely small, it has not been possible to significantly improve the recycling efficiency. Moreover, the centrifugal force is 1000 ~! 0OOG (G: gravitational acceleration)
As the above is extremely high, 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 using 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 soil mixed mud, then add a dispersant for dispersing the effective mud material and other solids to the mud mixed mud, stir and mix, and then apply a low centrifugal force of 30 to 400 G. The device is characterized by recovering the stabilized liquid through this, and the device includes a sieve that removes gravel from the mixed mud water lifted from the excavation trench, and a sieve that removes the gravel from the sieve. A mixer stirs and mixes the mixed mud and the dispersant, and this mixer supplies the mud mixed mud after the dispersant has been added, and stabilizes the mud mixed mud by applying a low centrifugal force of 30 to 400 G to the mud mixed mud. It is characterized by being equipped with a low-speed centrifuge for obtaining liquid.

[Function] According to the method and recovery device for stable liquid in the mud excavation method, etc. of the present invention, the mixed mud water lifted from the excavation trench is sieved to obtain the mixed mud water from which gravel has been removed. Next, a dispersant for dispersing the effective mud material and other solids is added to this mixed mud, and the mixture is stirred and mixed using a mixer, and then a low centrifugal force of 30 to 400 G is applied using a low-speed centrifuge. and thereby recover the stabilizing solution.

According to this, when recovering a stable liquid from mixed muddy water, the muddy material and sand contained in this mixed muddy water are mixed and stirred together with a dispersant by a mixer to form a dispersed state, and then they are passed through a low-speed centrifuge to form a dispersed state. By processing, the separation ability is extremely high, the processing time is significantly shortened, and there is no need to provide a settling tank for settling the sand, so the overall size of the apparatus can be reduced.

In addition, the low-speed centrifugal separator is designed to apply a low centrifugal force of about 30 to 400 G to the mixed muddy water, thereby effectively separating the mixed muddy water into fine soil particles and a stable liquid. By using it in conjunction with the action of the dispersant mentioned above, it is possible to recover most of the muddy water materials, resulting in extremely high recycling efficiency and a dramatic increase in the throughput per unit time. The separator itself can be made smaller.

Compared to conventional high-speed centrifuges, the above-mentioned low-speed centrifugal separators generate less noise and can be operated with a low-output drive device, so they consume less power and are extremely economical, making them extremely economical and useful in the construction industry. Contributes greatly to development.

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

Reference numeral 19 in FIG. 1 indicates a stabilizing liquid recovery device according to the present invention, and H is an excavation trench excavated by an excavation machine in the ground for constructing 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 and discharged to the outside.

Upper and lower vibrating screens 20 a and 20 b are arranged on the ground on the side of the excavated trench H, and these vibrating screens 2
A first storage tank 21 is installed at the bottom of 0a and 20b to collect muddy water mixed with earth and sand that has passed through them. Furthermore, a plurality of cyclones 22 (five in this case) are installed above each vibrating screen 20a120b.

Among the vibrating sieves 20a and 20b, the lower vibrating sieve 20b has the function of removing sand and gravel with relatively large particle sizes from the mixed mud water discharged from the excavation trench H; The vibrating sieve 20a has a function of removing sand and gravel with small particle diameters contained in the underflow of each cyclone 22 (the muddy water containing most of the sand in the mixed muddy water).

The cyclones 22 have the same configuration as that shown in FIG. After over 70 minutes (the muddy water from which most of the sand has been removed from the mixed muddy water) is passed through the static mixer 24, it is once transferred to the second storage tank 2.
5, the pump 26 supplies the decanter (low-speed centrifuge) 27, and
20a and 20b, and are returned to the first storage tank 21 again.

In the static mixer 24, the fluid passes through a stirrer, such as a spiral blade, provided in a conduit, whereby turbulence is generated in the fluid itself and the fluid is stirred. Then, an appropriate amount of dispersant is added to each cyclone 22.
By stirring for over 70 minutes, the sand and effective mud materials as a stabilizer such as bentonite contained in the overflow are effectively dispersed by the action of the dispersant.

As the dispersant, sodium tripolyphosphate, sodium hexametaphosphate, sodium polyacrylate,
Examples include aqueous solutions or salaried materials such as polycarboxylic acids and amino acids, which also function to prevent deterioration of muddy water materials.

The decanter 27 has a similar structure to that shown in FIG. 6, but the centrifugal force of the hollow shaft inside the casing is G (centrifugal force) when the under 70-min is ejected against the inner wall of the casing. is set to be about 30 to 400G. The under 70 minutes 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 temporarily stored in a circulation tank 28 and then recovered by a pump 29. It is designed to be sent to line 30.

Further, a replenishment tank 31 in which replenishment muddy material is stored is installed next to the circulation tank 28 , and the muddy material in this replenishment tank 31 is pumped over the replenishment line 33 by a pump 32 to the recovery line 30 . 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 earth and sand mixed mud discharged from the excavation trench H is conveyed onto the lower vibrating sieve 2Ob, and is first passed through the vibrating sieve 20b.
Relatively large pieces of sand and gravel are removed by applying this method. Then, the mixed mud water that has passed through the vibrating sieve 20b and is temporarily stored in the first storage tank 21 is pumped up by the pump 23 and branched and supplied to each cyclone 22.

Next, by passing through each of these cyclones 22...
・It is separated into an overflow portion (muddy water from which most of the sand has been removed from the muddy water mixed with earth and sand) and an underflow portion (muddy water which contains most of the sand from the muddy water mixed with earth and sand).

Then, for under 70 minutes, use the upper vibrating sieve 20a.
Small gravel and the like are removed by passing through the lower vibrating sieve 20b and stored in the first storage tank 21, and then processed again in each cyclone 22...

On the other hand, the overflow is supplied into the static mixer 24. Here, in the static mixer 24,
An appropriate amount of the above-mentioned dispersant is added, and the dispersant and the overflow are mixed by stirring. As a result, the effective slurry material as a stable liquid such as bentonite contained in the overflow and the sand are effectively dispersed.

Next, the overflow in which muddy water material and sand are dispersed in the static mixer 24 is stored in a second storage tank 25 and then supplied to a decanter 27 by a pump 26.

The overflow amount supplied to the decanter 27 is 3
By applying centrifugal force at a low acceleration of about 0 to 400 G, it is separated into fine soil particles and a stable liquid. Here, the muddy water material and sand contained in the overflow are:
Since it is mixed and stirred together with a dispersant in the static mixer 24 in advance and is in a dispersed state, the separation ability is extremely high and it can be effectively separated. Then, this stable liquid is pumped up by the pump 29 and collected in the recovery line 3.
0, and the separated fine soil particles are reused as sand S for appropriate purposes.

Next, the slurry material in the replenishment tank 31 is transferred to the recovery line 30 by the pump 32 via the replenishment line 33 into the recovery line 30, and is mixed with the stabilizing liquid passing through the recovery line 30 to form the final material. The stabilized liquid is injected into the excavated trench H again through the recovery line 30.

Incidentally, FIG. 2 shows step 70- of the above-mentioned processing step.

As described above, according to the method of recovering the stable liquid using the stabilizer liquid recovery device 19, when recovering the stable liquid from the over 70-minute portion, which is the treated water of each cyclone 22, the amount contained in the overflow amount is The muddy water material and sand are mixed and stirred together with a dispersant in the static mixer 24 in advance, so that they are in a dispersed state.
It has extremely high separation power, significantly reduces processing time compared to conventional methods, and is extremely efficient.

In addition, the decanter 27 has a capacity of 3
By applying a centrifugal force with a low acceleration of about 0 to 400 G, the overflow is set to be effectively separated into fine soil particles and a stabilizing liquid, and is used in conjunction with the action of the dispersant described above. As a result, most of the muddy water material can be recovered, and therefore the recycling efficiency is extremely high, the throughput per unit time is dramatically increased, and the decanter 27 itself can be made smaller.

Furthermore, since a stable liquid can be obtained by the decanter 27, there is no need to provide a settling tank for settling sand in the subsequent process, so 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 the above embodiment, a process using a cyclone 22 is provided between the vibrating sieve 20b and the static mixer 24. As shown in , the low-speed centrifugal mixed mud water obtained by adding a low centrifugal force of the earth and sand OG that has passed through the vibrating sieve 20b to obtain a stable liquid is sent to the static mixer 24 without passing through the cyclone 22 to obtain a stable liquid. You may also do so.

[Effects of the Invention] As explained above, according to the method and device for recovering the stable liquid in the muddy water excavation method, etc. of the present invention, the method includes sieving the muddy water mixed with earth and sand discharged from the excavation trench. Obtain mud mixed mud from which gravel has been removed.
Next, a dispersant for dispersing the effective mud material and other solids is added to this muddy mixed mud, and after stirring and mixing, a low centrifugal force of 30 to 400 G is applied, thereby recovering a stable liquid. The device includes a sieve for removing gravel from the mixed mud water pumped from the excavation trench, and a sieve that stirs the mixed mud water from which the gravel has been removed by the sieve and the dispersant. It is characterized by being equipped with a mixer for mixing, and a 30 to 40 separator for the mixed mud, which is supplied with the mixed mud after the dispersant has been mixed with the mixer, and for this mixed mud.
It has the following effects.

■When recovering a stable liquid from mixed muddy water, the muddy material and sand contained in this mixed muddy water are mixed and stirred together with a dispersant by a mixer to form a dispersed state.
It is then processed in a low-speed centrifuge, resulting in extremely high separation performance and significantly shortened processing time, making it extremely efficient.

■Low speed centrifugal separator is 30 to 4
By applying a low centrifugal force of about 00G, it is designed to effectively separate muddy water mixed with earth and sand into fine soil particles and a stabilizing liquid. Most of the muddy water material can be recovered, and as a result, the recycling efficiency is extremely high, and the amount of processing per unit time is dramatically increased.Furthermore, the centrifugal separator itself can be made smaller, which reduces power consumption. This will be reduced.

■Since a stable liquid can be obtained using a low-speed centrifuge, there is no need to install a settling tank to settle sand in the subsequent process.
The entire device can be downsized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of the stable liquid recovery device of the present invention,
FIG. 2 is a flow diagram of a method for recovering a stable liquid using the apparatus shown in FIG. 1, and FIG. 3 shows a conventional method for recovering a stable liquid.
Figure 4 is a conventional stable liquid recovery device, Figure 5 is a side sectional view of a cyclone, Figure 6 is a side sectional view of a decanter, and Figure 7 is a diagram showing the particle size range for each soil separation method. be. 19... Stable liquid recovery device, 24... Mixer (static mixer), 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 materials 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. Then, a dispersant for dispersing the effective mud material and other solids is added to this mixed mud and mixed with stirring, followed by 30 to 400 G. A method for recovering a stable liquid in a mud excavation method, etc., which is characterized by applying a low centrifugal force of 1, and recovering the stable liquid thereby. (2) A device 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., which removes gravel from the mud mixed mud. A sieve to be removed, a mixer that stirs and mixes the dispersant and the muddy mud from which gravel has been removed by the sieve, and the mixer supplies the muddy muddy water into which the dispersant has been mixed, and the muddy mud is mixed with the dispersant. 30 to 40 for muddy water
A recovery device for stable liquid in a mud excavation method, etc., comprising a low-speed centrifugal separator that obtains a stable liquid by applying a low centrifugal force of 0G.