JP6618328B2 - Method of dewatering mud - Google Patents

Description

  The present invention relates to a method for dewatering a mud, and more particularly to a method for dewatering a mud that can be easily dewatered with a small number of man-hours.

  A large amount of dredged soil from construction sites such as civil engineering is transported to disposal sites and disposed of. When dredged soil contains a large amount of moisture, handling during transportation is difficult, and the number of acceptable disposal sites is limited. Moreover, since the weight and volume of the clay increase according to the water content, the cost required for disposal increases. In order to solve such a problem, a method of dewatering mud has been proposed (for example, Patent Document 1). In the invention described in Patent Document 1, mud soil containing a large amount of water is sealed in a specially-designed dewatering device, and the dewatering device is set on the bottom of the water. Accordingly, the dewatering efficiency is increased by reducing the pressure in the dewatering device (in the tubular member) in water. However, in this dewatering method, when a large amount of mud is dewatered, it is necessary to prepare many dewatering devices with special specifications. In addition, since it is necessary to set the dewatering device to the bottom of the water after sealing the mud in the dewatering device, the number of work steps increases, and the cost for dewatering increases accordingly.

  A modifier may be used to facilitate handling during the transport of the mud. This modifier absorbs moisture in the soil by mixing with the mud. As a result, the fluidity of the mud is reduced and reformed to such an extent that it becomes independent. However, the moisture content in the soil does not change substantially before and after the modification because the modifier contains moisture in the soil. Therefore, the effect of reducing the cost required for disposal of mud cannot be expected.

JP 2006-88101 A

  An object of the present invention is to provide a method for dewatering mud that can be easily dewatered with less man-hours.

In order to achieve the above object, the method for dewatering a mud according to the present invention comprises mixing a predetermined proportion of water-absorbing modifier in the mud to reform it into a plastic soil, and then converting the plastic soil into a rod-like or comb-like instrument. A dehydration promoting portion consisting of holes or cuts is formed in the plastic soil by drawing out, and moisture contained in the plastic soil is removed from the surface and the dehydration promotion portion by the action of its own weight. It is characterized by discharging from the surface to the outside of the plastic soil.
Another method of dewatering a mud according to the present invention is to mix a mud with a predetermined proportion of water-absorbing modifier and reform it into a plastic soil, and the bottom surface and side surfaces of the plastic soil have water permeability. possible to accommodate in contact with the flexible permeable container, being exposed directly to the outside air without covering the outer peripheral surface of the permeable container with the coating material, the water contained in the plastic-like soil, this The plastic soil is discharged from the surface thereof to the outside of the plastic soil and the water permeable container through the lower surface or the side surface of the water permeable container by the action of its own weight.

  According to the present invention, by mixing the absorptive modifier in an appropriate predetermined ratio with the mud, the plasticity having a viscosity that allows the mud to become independent by temporarily retaining moisture in the soil between the soil particles. Reform into a soil. Since moisture is held weakly between the particles in this plastic-like soil, this moisture is discharged from the surface of the plastic-like soil by the action of the weight of the plastic-like soil. Therefore, more moisture in the soil can be discharged to the outside and the dehydration time can be shortened as compared with mud when no modifier is mixed. In addition, mud soil can be dehydrated easily and with a small number of steps without requiring a large-scale device such as a specially-designed dewatering device or a press machine, so that labor and cost can be reduced. Since the weight and volume can be reduced as compared with those before dehydration, the cost required for disposal can also be reduced.

  With respect to the mud to be treated, the predetermined ratio that is modified to plastic-like soil when the modifier is mixed and that allows moisture contained therein to be discharged to the outside by the action of the weight of the plastic-like soil. It can also be grasped in advance. Thus, the mud dewatering process can be performed more efficiently by preliminarily grasping the mixing ratio of the water-absorbing modifier suitable for dewatering the mud to be treated.

  It is also possible to form a dehydration promoting part consisting of holes or cuts in the plastic soil, and to discharge the moisture from the surface of the dehydration promoting part to the outside of the plastic soil. By forming the dehydration promoting portion, the drainage distance from the inside to the surface of the plastic soil is shortened, and the dewatering time can be shortened.

  The dehydration promoting portion may be formed by vertically cutting at least the plastic soil. If the dewatering promotion part is formed so as to run vertically above and below the plastic soil, even if the plastic soil is deformed by its own weight, it is easy to maintain holes and cuts, and it is advantageous to ensure the function as the dehydration promotion part. become.

  In a state where the plastic soil is accommodated in a water-permeable container, the moisture can be discharged to the outside of the plastic soil. When the plastic soil is accommodated in the water-permeable container, the self-supporting state of the plastic soil can be stably maintained even in a state where the plastic soil is highly elevated. Therefore, compared with the case where a water-permeable container is not used, it is possible to further increase the action of the weight of the plastic soil, which is advantageous for shortening the dewatering time of the mud.

It is explanatory drawing which illustrates a mixing process by a longitudinal cross-sectional view. It is explanatory drawing which illustrates a spin-drying | dehydration process by a longitudinal cross-sectional view. It is a graph which illustrates the relationship data of elapsed time and the amount of drainage. It is explanatory drawing which illustrates the condition where the plastic soil in which the dehydration promotion part was formed is dehydrated in the longitudinal cross-sectional view. It is explanatory drawing which illustrates the condition which forms a spin-drying | dehydration promotion part in plastic-like soil by a longitudinal cross-sectional view. It is a graph which shows the relationship data of the elapsed time and the amount of drainage in an Example.

  Hereinafter, the mud dehydration method of the present invention will be described based on the embodiments shown in the drawings.

  In the present invention, the mud is dehydrated using a water absorption modifier (hereinafter referred to as a modifier). A modifier is comprised from the organic polymer etc. which have water absorption, for example, and absorbs the water | moisture content in mud by mixing with mud. Conventionally, the modifier has been used to hold the moisture in the soil firmly between the soil particles and reduce the fluidity of the mud to make a soil mass. In the present invention, the modifying agent is used for performing the dewatering treatment of the mud, unlike the conventional method of use by changing the idea.

  The present invention is roughly divided into two steps, a mixing step and a dehydrating step. Details of each step will be described below. In this embodiment, the case where the mud is contaminated soil is illustrated, but the present invention is not limited to the case where the mud is contaminated soil, and can also be applied to mud such as dredged soil.

  In the mixing step illustrated in FIG. 1, a predetermined ratio of the modifier K is mixed with the mud D. Then, the mud D is reformed into a plastic soil S having a viscosity that allows the mud D to stand on its own. Specifically, in order to prevent the contaminant contained in the mud D from flowing out to the external soil, the mud D is accommodated in the tank 1 or the like, and the mud D is isolated from the external soil. Then, the mud D is reformed into the plastic soil S by mixing the modifier K with the mud D contained in the tank 1 at a predetermined ratio. Mixing of the mud D and the modifier K is performed by, for example, the backhoe 2 having a mixing bucket. In addition, it can mix using various agitators.

  As described above, in the present invention, by mixing a predetermined ratio of the modifier K with the mud D, free water in the soil is held between the soil particles by the hydrophilic group of the modifier K. And by this effect | action, the fluidity | liquidity of the mud D is reduced. That is, in the mixing step, the moisture W contained in the soil is kept in the plastic soil S by the modifier K.

  Here, what is important in the present invention is the predetermined ratio of the modifier K to be mixed with the mud D. The predetermined ratio is a ratio at which the moisture W held between the soil particles is discharged from the surface of the plastic soil S to the outside by the action of the weight of the plastic soil S.

  In the dehydration step, the plastic soil S modified by the mixing step is left in a well-drained state, and the moisture W contained in the plastic soil S is plasticized by the action of its own weight (self-weight consolidation). The soil S is discharged to the outside.

  In this embodiment, as shown in FIG. 2, the plastic soil S is accommodated in a water permeable container 3 having water permeability, and the water permeable container 3 in which the plastic soil S is accommodated is formed by crushing crushed stones. It is placed on the crushed stone stand 4. Examples of the water permeable container 3 include a flexible container bag used in civil engineering work. In this embodiment, the water-impervious sheet 5 is laid on the ground so that the pollutants contained in the plastic soil S do not flow out to the outside soil, and are discharged from the outer surface of the plastic soil S and ooze out from the water permeable container 3. Moisture water W flows on the water-impervious sheet 5 and accumulates in the water reservoir 6.

  In this way, by leaving the plastic soil S modified by the mixing step in a state in which the action of its own weight acts, the moisture W held between the soil particles by the modifier K is reduced by the weight of the plastic soil S. It is pushed out between the soil particles by the action, and is discharged to the outside from the surface of the plastic soil S. More specifically, since a relatively large weight acts on the lower part of the plastic soil S in a stationary state, a relatively large amount of water W is discharged from the lower part. When the lower moisture W is discharged to the outside, the upper moisture W moves to the lower portion where the moisture W decreases. And the water | moisture content W which moved to the lower part from the upper part is discharged | emitted outside the plastic soil S by the effect | action of dead weight. In this manner, not only the lower moisture W but also the upper moisture W is discharged to the outside of the plastic soil S.

  That is, in the present invention, the predetermined ratio of the modifier K mixed with the mud D is to temporarily hold the moisture W in the soil, but the weight of the plastic soil S acts on the The moisture W can be released from between the soil particles and discharged to the outside of the plastic soil S.

  This predetermined ratio differs depending on conditions such as the modifier K, the type of mud D, the moisture content of the mud D, and the like. Therefore, the mixing ratio with high dewatering efficiency in the mud D to be treated is grasped in advance by a test or the like.

  Specifically, for example, a plurality of types of samples in which the modifier K is mixed with the mud D to be treated at different ratios are measured, and the amount of wastewater per elapsed time due to the weight of each sample (self-weight compaction) is measured. To do. When comparing the dehydration efficiencies of the respective samples, for example, a graph as shown in FIG. 3 is created. The vertical axis of the graph in FIG. 3 indicates the amount of drainage (cc), and the horizontal axis indicates the elapsed time (days). And the mixing ratio with the highest dehydration effect is selected. In this embodiment, when the modifier of n% (weight ratio) is mixed with the mud, the dehydration effect is the highest, so the predetermined ratio is n%.

  As shown in FIG. 3, when the mixing ratio of the modifier K to the mud D is excessive (mixing amount n × 2%), the viscosity of the mud D increases, but the moisture W in the soil is strongly between the soil particles. Therefore, even if the action of its own weight works, it becomes difficult for moisture W to be released between the soil particles. Therefore, the moisture W in the soil is difficult to be discharged to the outside of the plastic soil S, and the dewatering effect is reduced.

  Conversely, if the mixing ratio of the modifier K with respect to the mud D is too small (mixing amount n / 2%), the moisture W in the soil cannot be sufficiently retained between the soil particles, so that it can stand on its own. The fluidity of the mud D cannot be reduced. When the viscosity of the mud D is low, the action of its own weight cannot be sufficiently performed. Therefore, the moisture W in the soil is difficult to be discharged to the outside of the mud D, and the dewatering effect is lowered.

  Thus, according to the present invention, by mixing the mud D and the modifier K at a special mixing ratio (predetermined ratio: mixing amount n%) different from the conventional method of using the modifier K, The moisture W in the soil is temporarily held between the soil particles, and the mud D is reformed into a plastic soil S having a viscosity enough to be self-supporting. Since the moisture W is held weakly between the particles in the plastic soil S, the moisture W is discharged from the surface of the plastic soil S to the outside by the action of the weight of the plastic soil S.

  Therefore, when the modifier K is not mixed (raw mud), when the modifier K is mixed too small (mixing amount n / 2%), or when the modifier K is excessive (mixing amount n × 2%). ), It is possible to discharge more moisture W in the soil to the outside, and the dehydration time can be shortened.

  In detail, in the state of the mud D containing a large amount of water W, the soil particles are separated (single grain structure), but by mixing the modifier K, the respective soil particles are collected. The aggregate structure is formed. Since the aggregate structure is formed, a large gap is formed between the aggregates, so that an effect of facilitating discharge due to its own weight due to easy passage of moisture W can be obtained. Furthermore, the surface area in contact with the outside air is increased as compared with the case of the mud D due to the plastic soil S. Therefore, the effect of dehydrating by natural drying at the upper part of the plastic soil S is also obtained.

  Further, since the mud D can be dehydrated easily and with a small number of processes without requiring a large-scale apparatus such as a dehydrating apparatus or a press machine with special specifications, labor and cost can be reduced. This is particularly useful when a large amount of mud D is dewatered.

  Furthermore, since the weight and volume can be reduced by performing the dehydration process as compared to before dehydration, the cost required for disposal can be reduced. This is particularly beneficial when the mud D is contaminated soil. Since the contaminated soil has a high moisture content, the acceptable contaminated soil treatment facilities are limited. Therefore, disposal of the contaminated soil requires a great deal of cost. Can increase the choice of acceptable contaminated soil treatment facilities. Therefore, the cost of disposing contaminated soil can be greatly reduced. The dehydrated plastic soil S is transported to the disposal facility in a manner designated by the disposal facility (contaminated soil treatment facility or the like). Specifically, for example, the plastic soil S is refilled and transported from the water-permeable container 3 to a double flexible container bag, a drum can, or the like.

  Moreover, the dehydration process of the mud D can be efficiently performed by grasping | ascertaining previously the predetermined ratio of the modifier K mixed with the mud D suitable for dehydrating the mud D to be processed by a test or the like.

  When the plastic soil S is accommodated in the water permeable container 3 as in this embodiment, the self-supporting state of the plastic soil S can be stably maintained even when the plastic soil S is raised. Therefore, compared with the case where the water permeable container 3 is not used, it is possible to further increase the action of the weight of the plastic soil S, which is advantageous for shortening the dehydration time. Further, by storing the plastic soil S in the water permeable container 3 and subdividing it, the drainage from the inside of the plastic soil S to the surface is possible compared to the case where the plastic soil S is not subdivided and filled. The distance can be shortened. Therefore, compared with the case where the water-permeable container 3 is not used, it is advantageous to shorten the dehydration time.

  In the dewatering step shown in FIG. 3, the plastic soil S is accommodated in the water permeable container 3 and is left as it is. However, as shown in FIG. 4, dehydration promoting parts such as holes and cuts are formed in the plastic soil S. By forming H, moisture W in the soil can be discharged from the surface of the dehydration promoting portion H to the outside of the plastic soil S.

  The dehydration promoting portion H can be formed, for example, by inserting a rod-like or comb-like instrument into the plastic soil S and pulling it out. In addition, for example, a rod-like or comb-like instrument is installed in a place where the plastic soil S is placed, and after the plastic soil S is transferred to the place, the dehydration promoting part is removed. H can also be formed.

  When the amount of the plastic soil S is large, for example, as shown in FIG. 5, the dehydration promoting portion H can be formed using the backhoe 2. Specifically, a dehydration promoting portion forming attachment 7 constituted by a connecting portion 7b that can be attached to and detached from the arm 2a of the backhoe 2 and a plurality of rod-like portions 7a projecting from the connecting portion 7b is provided. Attached to the arm 2a of the backhoe 2. Then, by operating the arm 2a of the backhoe 2, the rod-like portion 7a of the attachment 7 for forming the dehydration promoting portion is inserted into the plastic soil S and pulled out, thereby forming the dehydration promoting portion H. As shown in FIG. 4, the dehydration promoting portion H may be formed so as to vertically cut the plastic soil S.

  In this way, by forming the dehydration promoting portion H in the plastic soil S, the drainage distance from the inside to the surface of the plastic soil H is shortened, and the moisture W exuded from the surface of the dehydration promoting portion H promotes dehydration. It is quickly discharged to the outside of the plastic soil S through the portion H. Therefore, the dehydration time can be shortened as compared with the case where the dehydration promoting portion H is not formed on the plastic soil S.

  Furthermore, if the dehydration promoting part H is formed so as to be vertically cut off the plastic soil S, even if the plastic soil S is deformed by its own weight, it is easy to maintain holes and cuts, and the function as the dehydration promoting part H is achieved. It will be advantageous to ensure. In addition, although it is desirable to form the dehydration promotion part H so that it may cut longitudinally up and down of the plastic-like soil S, it can also be formed in the diagonal direction and the horizontal direction of the plastic-like soil S, and the middle of the plastic-like soil S It is also possible to form up to the position.

  In the dehydration process of the embodiment described above, dehydration is performed by placing the plastic soil S accommodated in the water permeable container 3 on the crushed stone table 4. For example, the plastic soil S is It can also dehydrate in the state which suspended the water-permeable container 3 accommodated with the crane etc. Further, for example, the plastic soil S can be dewatered in a state where the plastic soil S is filled without embedding the plastic soil S in the water-permeable container 3.

Four types of plastic soil samples (samples A, B, C, and D) were prepared by mixing the same mud with the water content of 221% and different proportions of the same modifier. 500 g of raw mud not mixed with each other was stored in a compacting container, and the amount of drainage per elapsed time due to self-weight compaction at atmospheric pressure was measured. The mixing ratio of the modifier in each sample was 2 kg / m ³ (sample A), 3 kg / m ³ (sample B), 4 kg / m ³ (sample C), 6 kg / m ³ (per unit volume of mud, respectively). Sample D). The measurement results are as shown in the graph of FIG.

  In this test, it can be seen that Sample B has the highest dehydration efficiency. Specifically, 95 g of drainage was confirmed by self-weight consolidation for 6 hours. This is a 19% drainage with respect to a total weight of 500 g, and 27.6% of the retained water has been dehydrated.

It can be seen that Sample B is dehydrated at a rate approximately 2.7 times that of the raw mud. From the viewpoint of dehydration efficiency, it can be seen that the mixing ratio of the modifier is excessive in sample D (6 kg / m ³ ) and excessive in sample A (2 kg / m ³ ).

1 Tank 2 Backhoe 2a Arm 3 Permeable container 4 Crushed stone stand
5 Water-impervious sheet 6 Water storage part 7 Attachment 7a for dehydration promotion part Rod-like part 7b Connection part D Mud K Water absorption modifier S Plastic-like soil H Dehydration promotion part W Water

Claims (5)

A mud soil is mixed with a water absorbing modifier at a predetermined ratio to be modified into a plastic soil, and a rod-like or comb-like instrument is pulled out from the plastic soil to provide a dehydration promoting portion consisting of holes or cuts in the plastic soil. It is formed, and moisture contained in the plastic-like soil is discharged from the surface and the surface of the dehydration promoting portion to the outside of the plastic-like soil by the action of its own weight. A method for dewatering mud. A mud soil is mixed with a water-absorbing modifier at a predetermined ratio to be modified into a plastic soil, and the plastic soil is stored in contact with a flexible and water-permeable container whose bottom and side surfaces are permeable. In the state where the outer peripheral surface of the water-permeable container is directly exposed to the outside air without being covered with a covering , the moisture contained in the plastic-like soil is removed from the surface by the action of the weight of the plastic-like soil. A method for dewatering mud soil, characterized in that the soil is discharged to the outside of the plastic soil and the water permeable container through a lower surface or a side surface of the water permeable container.   The method for dewatering mud according to claim 2, wherein a dehydration promoting part including holes or cuts is formed in the plastic soil, and the water is discharged from the surface of the dehydration promoting part to the outside of the plastic soil. .   The method for dewatering mud according to claim 1 or 3, wherein the dewatering promoting portion is formed by vertically cutting at least the plastic soil.   With respect to the mud to be treated, the predetermined ratio that is modified to plastic-like soil when the modifier is mixed and that allows moisture contained therein to be discharged to the outside by the action of the weight of the plastic-like soil. The method for dewatering mud according to any one of claims 1 to 4, which is grasped in advance.

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