JP2005042392A - Dredging plant and dredging method for dam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dredging plant and a dredging method for a dam, which bring about efficient recovery from a decrease in function of the dam due to the progress of sedimentation, which prevent erosion of a downstream area and a coast near a river mouth, and which conserves an environment for maintaining water quality of a river. <P>SOLUTION: This dredging plant for the dam is equipped with dredging equipment 1 for dredging sediment on a bottom 7 of a dam lake, and a classifying plant 40 which separates the sediment with a large particle diameter from the sediment dredged by the dredging equipment and which separates an arbitrary fine-grained fraction. This enables the sediment with the large particle diameter to be separated from the sediment on the bottom 7 and used as a construction material etc., and enables the arbitrary fine-grained fraction to be separated and placed as a feed material for the river in the river so as to recover an eroded river bed in the downstream area of the dam and the coast near the river mouth. After floating matter removed from the dam lake is reduced in volume while being insolubilized and solidified, the bottom 7 is backfilled with the floating matter, so that a disposal field can be dispensed with. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dam dredge plant and a dam dredge method.

  Sustainable management of dams in a healthy state over a long period of time is important from the viewpoint of stable supply of water resources, flood control, etc. In order to do so, it is necessary to remove sediments that have accumulated sediment flowing into the dam. There is a need to. The progress of sedimentation in the dam will reduce the water storage procedures of the dam in the long term and reduce the dam's flood control and water utilization functions.

  Moreover, while the riverbed rises upstream of the dam due to the progress of sedimentation, problems such as the riverbed falling downstream of the dam and the coast eroding near the estuary have occurred. Recently, it has also been pointed out that the impact on environmental aspects such as depletion of nutrients due to a decrease in the supply of sediment to the downstream and changes in the habitat environment of fish and the like accompanying it.

  There are two methods for removing dam sedimentation: draining the dam lake and drilling directly, or dredging. In addition, a method has been implemented in which a sediment discharge port is provided in the dam and discharged downstream, and a sand storage dam is provided upstream of the existing dam, and a discharge tunnel is provided from the sand storage dam to the downstream of the existing dam to discharge downstream. Yes.

  As a method of dredging dam sedimentation, a general dredging using a pump ship, grab ship, bucket ship, dipper ship, etc., or after crushing hard ground difficult to construct with a general dredging using a rock breaking ship or explosives There is a method of performing general soot (see Non-Patent Document 1, for example).

  In general river construction, pump boats are often used. The dredging by the pump ship sucks the sediment at the bottom of the water and discharges it to the stockyard or landfill through the drainage pipe. The pump itself is intended for relatively soft soil such as sludge and sandy soil, and N value When dredging 10 or more earth and sand, a cutter device is often used together. Pump dredging has advantages such as continuous dredging and high work efficiency.

  The grab ship is a grab ship that excavates the earth and sand with a grab bucket and can dredge at a deep water depth and can cope with soil quality from soft mud to hard soil. For example, as shown in FIG. 5, the earth and sand dredged by the grab ship 1 is separated into gravel, clay, sediment, miscellaneous garbage, etc. by the processing plant ship 2, and then transported to the shore by the earth ship 3, and is tracked from the shore. It will be transported to the disposal site at 4 mag. The dredging method using the grab ship 1 can be used when the earth and sand are transported by the earth ship 3 and the distance for discharging the soil is very long and the pump ship cannot be applied.

As a method for treating dredged earth and sand, the earth and sand with relatively large particles were classified and used as construction materials, and other fine particles were dehydrated and treated as industrial waste. In addition, it has also been proposed to classify earth and sand with a cyclone or the like to return earth and sand or fine particles having a large particle size to a dam and to decompose and treat organic substances (for example, see Patent Document 1).
JP-A-10-118697 Civil Engineering Handbook II, 4th edition, Gihodo Publishing, November 18, 1989, p. 1626-1627, 1822

  However, when excavating or dredging directly in the dam lake, a disposal site is required to process fine particles that cannot be used as construction materials as industrial waste. There was a problem of cost.

  The method of providing a sediment discharge port in a dam, or a sand storage dam or a discharge tunnel has a problem that the construction cost is high. In addition, when the earth and sand are discharged downstream, there is a problem in that the river environment is adversely affected, for example, turbid water is generated downstream or earth and sand are accumulated. On the other hand, problems such as river bed degradation, coastal erosion, and nutrient depletion could not be solved if dredged soil was only treated and not discharged downstream.

  An object of the present invention is to efficiently recover from the deterioration of the dam due to the progress of sedimentation, prevent erosion of the coast near the downstream and estuary, and protect the water quality of the river.浚 渫 provide a way.

  In order to solve the above problems, the invention described in claim 1 is a dam dredging plant, for example, as shown in FIGS. 1 to 3, a dredging device (grab ship 1) for dredging sediment on the dam lake bottom 7; And a classification plant 40 that separates large-particle-size soil from the soil that has been dredged by the dredger, and separates fine particles having an arbitrary particle size.

  Here, as the fine particles having an arbitrary particle size, those having a particle size that does not cause excessive sedimentation or water pollution downstream are selected according to river conditions. According to the first aspect of the present invention, it is possible to separate large sediment from the sediment at the bottom of the dam lake 7 and use it for construction materials, etc. By laying in the river as a supply material, the eroded river bed downstream of the dam and the coast near the estuary can be restored.

  The invention according to claim 2 is the dam dredging plant according to claim 1, wherein, as shown in FIG. 2, the classification plant 40 dams a part of the dam lake water pumped up together with earth and sand from the dam lake bottom 7. In addition to having a water discharge route for discharging water downstream (route from B in FIG. 2 to B in FIG. 1), a water purification plant 60 for purifying the dam lake water pumped up together with earth and sand from the dam lake bottom 7 is provided.

  According to the invention described in claim 2, by discharging a part of the dam lake water pumped up with the earth and sand of the dam lake bottom 7 from the discharge channel to the dam downstream, the nutrients such as nitrogen and phosphorus contained in the dam lake water are It is possible to supply an appropriate amount to the river, and to prevent nutrient depletion in the river. Moreover, by purifying the remaining dam lake water at the water purification plant 60, it is possible to prevent the nutrients more than necessary from flowing downstream of the dam to cause eutrophication of the river and to protect the downstream ecosystem.

  Invention of Claim 3 is the dam dredging plant of Claim 2, Comprising: As shown in FIG. 3, the said water purification plant 60 adds an insolubilizing agent and a solidification agent to the floating substance removed from the dam lake water. A mixing tank 64 for mixing is provided.

  Here, the floating substance is fine particles such as silt and clay that cause turbid water. According to the invention described in claim 3, since the insoluble agent and the solidifying agent are mixed with the floating substance removed from the dam lake water, the floating substance can be insolubilized, solidified and reduced in volume. It is possible to prevent the nutrients such as nitrogen and phosphorus contained in the sexual substance from dissolving, and to refill the dam lake bottom 7 with the floating substance.

  Invention of Claim 4 is the dam dredging plant as described in any one of Claims 1-3, Comprising: As shown, for example in FIG. 4, the dredging apparatus is the grab bucket 10, and the grab bucket 10 inside. A sand pump 23 having a suction port and a mud feeding hose 22 having one end connected to the sand pump 23 and the other end provided on the water.

  According to the invention described in claim 4, since the earth and sand in the grab bucket 10 is sucked by the sand pump 23 and discharged onto the water by the mud hose 22, the excavation is continued without raising the grab bucket 10 to the water. In addition, when the grab bucket is moved up and down, the dam lake water is not stirred to cause water pollution. In addition, since the excavation is performed with the grab bucket 10, it is possible to excavate and dredge even hard soil with large N value. In addition, obstacles such as debris and driftwood contained in the sediment at the bottom of the dam lake 7 can be removed with a grab bucket.

  The invention according to claim 5 is a method for dredging a dam, dredging the sediment at the bottom of the dam lake 7, separating large sediment from the dredged sediment, and removing fine particles having an arbitrary grain size. It is classified and supplied to the river.

  According to the invention described in claim 5, it is possible to separate large sediment from the sediment at the bottom of the dam lake 7 and use it for construction materials, etc. By laying in the river as a supply material, the eroded river bed downstream of the dam and the coast near the estuary can be restored.

  The invention according to claim 6 is the method for dredging the dam according to claim 5, wherein an arbitrary amount of the dam lake water pumped up with the earth and sand of the dam lake bottom 7 is discharged downstream of the dam, and the remaining dam lake water It is characterized by purifying.

  According to the sixth aspect of the present invention, an appropriate amount of nutrients such as nitrogen and phosphorus contained in the dam lake water is appropriately distributed to the river by discharging an arbitrary amount of the dam lake water pumped together with the sediment of the dam lake bottom 7 to the downstream of the dam. Supplying it can prevent nutrient depletion in the river. Moreover, by purifying the remaining dam lake water, it is possible to prevent the eutrophication of the river due to excessive nutrients flowing downstream of the dam and to protect the downstream ecosystem.

  The invention according to claim 7 is the method for dredging the dam according to claim 5 or 6, wherein the suspended matter is removed from the dam lake water pumped together with the sediment on the bottom of the dam lake 7 and insolubilized in the suspended matter. After mixing and insolubilizing and solidifying the agent and the solidifying agent and reducing the volume, it is backfilled to the dam lake bottom 7.

  According to the seventh aspect of the present invention, the insoluble agent and the solidifying agent are mixed with the floating substance removed from the dam lake water so as to be insolubilized, solidified, and reduced in volume, and then backfilled to the bottom of the dam lake to dispose of the waste. A place is no longer required and transportation costs can be reduced.

  The invention according to claim 8 is the method of dredging the dam according to any one of claims 5 to 7, wherein the grab bucket 10 excavates the earth and sand of the dam lake bottom 7, and then the grab bucket 10 is closed. In this state, water is spouted into the grab bucket 10 to stir the earth and sand, and the earth and sand on the dam lake bottom 7 are dredged by repeatedly transporting the stirred earth and sand to the water by the sand pump 23 inside the grab bucket 10. And

  According to the eighth aspect of the present invention, since water is jetted into the grab bucket 10 and the earth and sand are stirred, a muddy water flow is formed in the grab bucket 10 and the suction port of the sand pump 23 is blocked. It is possible to prevent the soil in the grab bucket 10 from being discharged more efficiently. Moreover, by discharging water into the grab bucket 10 in a state where the grab bucket 10 is closed and stirring the earth and sand, the mud water can be adjusted to an optimum concentration for discharging with the sand pump 23 and stable soil discharging can be performed. In addition, since it is sucked by the sand pump 23 and discharged on the water by the mud hose 22, it is possible to continuously dig without raising the grab bucket 10 to the water, and in the case of deep water, the cycle time per digging is reduced. It can be shortened. In addition, since the excavation is performed with the grab bucket 10, it is possible to excavate and dredge even hard soil with large N value.

  According to the present invention, soil and sand at the bottom of a dam lake are dredged and classified, stones, gravel, sand, etc. are used as construction materials, etc., and fine particles of any particle size are discharged as river supply agents. Sediment can be used effectively, and erosion of the coast near the river mouth and downstream can be prevented. In addition to supplying an appropriate amount of nutrients such as nitrogen and phosphorus contained in the dam lake water to the river, it is possible to prevent river nutrient depletion and eutrophication by not supplying excessive amounts.

  In addition, suspended solids are insolubilized, solidified, reduced in volume, and backfilled in the dam lake, so no disposal site is required and transportation costs can be reduced.

    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The dam dredging plant of the present invention includes a dredging device shown in FIG. 1, a classification plant 40 shown in FIG. 2, and a water purification plant 60 shown in FIG. Here, FIGS. 1 to 3 are obtained by dividing one flow diagram showing a series of processes by the dam dredging plant of the present invention, from A in FIG. 1 to A in FIG. 2, and from B in FIG. 2C, FIG. 3C, FIG. 2D to FIG. 3D, FIG. 3E to FIG. 1E, FIG. 3F to FIG. ing.

  In addition, since the classification plant 40 and the water purification plant 60 are assembly types, the movement of the apparatus is relatively easy, and materials can be transported to each dam and assembled on site.

  As a dredging device, for example, as shown in FIG. 1, a grab ship 1 floating on a dam lake 6 dammed by a dam dam body 5 can be used. A grab bucket 10 is suspended from the grab ship 1. As the grab bucket 10, the thing of the form demonstrated below can be used, for example.

  As shown in FIG. 4, the grab bucket 10 includes a base portion 11 and a pair of buckets 12 and 12.

  The base 11 has a pair of parallel shafts 14 and 14 to which the buckets 12 and 12 are respectively attached, and a rotation (not shown) for simultaneously rotating the buckets 12 and 12 with respect to the shafts 14 and 14 in opposite directions. A mechanism is provided. A suspension member 15 is provided at the upper end of the base 11. The suspension member 15 suspends the grab bucket 10 from the crane provided in the grab ship 1 underwater.

  In the figure, the buckets 12 and 12 are closed with their blade edges 13 and 13 fitted to each other, but open and close by simultaneously rotating in opposite directions with respect to the shafts 14 and 14.

  The buckets 12 and 12 are provided with a stirring water hose 21, a mud feeding hose 22, and a sand pump 23, respectively.

  The agitation water hose 21 extends to the grab ship 1 above the water, water is supplied from a water pump (not shown) provided in the grab ship 1, and water is ejected from a spout provided at the tip. The spout is provided near the blade edge 13 of the bucket 12.

  One end of the mud feeding hose 22 is attached to the sand pump 23, and the other end extends to the grab ship 1 on the water, and further extends from the grab ship 1 to the receiving tank of the classification plant.

  The sand pump 23 sucks the earth and sand from the suction port provided in the bucket 12 and sends it to the water grab ship 1 through the mud feeding hose 22. A metal mesh is installed at the suction port, so that troubles caused by the sand pump 23 sucking obstacles can be avoided.

  The grab boat 1 is provided with a crane that moves the grab bucket 10 and a water supply pump that supplies water to the stirring water hose 21. Moreover, the winding device which winds up the stirring water hose 21 and the mud feeding hose 22, and the processing equipment of earth and sand are provided.

  A dredge method using the grab bucket 10 will be described. First, the grab bucket 10 with the buckets 12 and 12 opened is lowered to the dam lake bottom 7.

  Next, the buckets 12 and 12 are rotated, and the dam lake bottom 7 is excavated by the blade edges 13 and 13. Further, the buckets 12 and 12 are rotated and closed until the blade edges 13 and 13 are fitted.

  Next, water is spouted from the agitation water hose 21, the earth and sand inside the closed bucket 12 is agitated, and the agitated earth and sand is sucked by the sand pump 23 and is sent to the water grab ship 1 via the mud feeding hose 22. Excavate.

  When the amount of earth and sand coming out of the mud hose 22 is reduced, the water pump and sand pump 23 are stopped and the buckets 12 and 12 are opened again. Next, the grab bucket 10 is further lowered or moved in the horizontal direction to excavate the dam lake bottom 7, and the above operation is repeated.

  When an obstacle such as garbage or a large stone larger than the mesh of the wire mesh at the suction port is mixed in the bucket 12, the soil is first sucked and only the obstacle is left in the bucket 12. Next, the water pump and the sand pump 23 are stopped, the grab bucket 10 is lifted to the water with the bucket 12 closed, and the grab bucket 10 to remove obstacles is lifted to the water. .

  According to such a dredge apparatus, since the earth and sand excavated without lifting the grab bucket 10 to the surface of the water can be discharged, the pollution of the water quality accompanying the raising and lowering of the grab bucket 10 can be reduced. Further, since the grab bucket 10 can be continuously excavated without moving up and down, the work efficiency of the dredging does not decrease even at a large depth. In addition, since the excavation is performed with the grab bucket 10, it is possible to excavate and dredge even hard soil with large N value.

  The excavated earth and sand are conveyed to the classification plant 40 by the sand pump through the mud hose 22 together with water.

  For example, as shown in FIG. 2, the classification plant 40 includes a primary screen 41, a primary stock 42, a primary receiving tank 43, a secondary screen 44, a secondary stock 45, a secondary receiving tank 46, a primary cyclone 51, and a primary. It comprises a cyclone over water tank 52, a secondary cyclone 53, a secondary cyclone under water tank 54, a secondary cyclone over water tank 55, and the like.

  The earth and sand conveyed through the mud feeding hose 22 is first applied to the primary screen 41 to remove stones and gravel having a large particle size and are carried out to the primary stock 42. Here, for example, a 4 mm mesh screen is used to separate stones and gravel with a particle size of 4 mm or more.

  The mud containing sand that has passed through the primary screen 41 is stored in the primary receiving tank 43, pumped out by a pump, and applied to the secondary screen 44. The secondary screen 44 removes the sand and carries it out to the secondary stock 45. Here, for example, sand having a particle diameter of 1 to 4 mm is separated using a 1 mm mesh screen.

  The muddy water that has passed through the secondary screen 44 is stored in the secondary receiving tank 46, pumped out by the pump, and applied to the primary cyclone 51. In the primary cyclone 51, fine particles are discharged into the primary cyclone over water tank 52 together with the primary cyclone over water, and the primary cyclone under water containing the sand having a slightly larger particle diameter is passed through the secondary screen 44 again to the secondary. Apply to screen 44.

  The primary cyclone over water stored in the primary cyclone over water tank 52 is pumped out by the pump and applied to the secondary cyclone 53.

  In the secondary cyclone 53, fine particles of an arbitrary size or more contained in the primary cyclone over water are stored in the secondary cyclone under water tank 54 together with the secondary cyclone under water, and fine particles of an arbitrary size or less are stored. The secondary cyclone over water tank 55 is stored together with the cyclone over water. For example, fine particles having a particle diameter of 0.1 mm to 1.0 mm can be stored in the secondary cyclone under water tank 54, and fine particles having a particle diameter of 0.1 mm or less can be stored in the secondary cyclone over water tank 55.

  The fine particles of any particle size stored in the secondary cyclone underwater tank 54 are pumped out and discharged downstream of the dam as a river supply to restore the eroded riverbed and the shore near the estuary. The The particle size can be changed by the secondary screen 44, the primary cyclone 51, and the secondary cyclone 53. However, the particle size is appropriately changed depending on river conditions and set to a particle size that does not cause excessive sedimentation or water pollution downstream. The

  As for the secondary cyclone over water stored in the secondary cyclone over water tank 55, an arbitrary amount is pumped out through the water discharge route (from B in FIG. 2 to B in FIG. 1) and discharged downstream of the dam. The rest is sent to the water purification plant 60 through the water purification path (from C in FIG. 2 to C in FIG. 3). The secondary cyclone over water contains nutrients such as nitrogen and phosphorus, and it can prevent the nutrient depletion of the river by discharging an appropriate amount downstream, but if too much is discharged, turbid water will fall downstream. Since it occurs and eutrophication of the river occurs and adversely affects the ecosystem, the flow rate is adjusted appropriately according to the river situation. The remaining secondary cyclone over water is processed at the water purification plant 60.

  As shown in FIG. 3, the water purification plant 60 includes a coagulation tank 61, a mud storage tank 62, a dehydrator 63, a mixing tank 64, a filtrate tank 71, a coagulation reaction tank 72, a precipitation separation tank 73, an aeration tank 74, and a filtration source. It is composed of a water tank 75, a filtration tower 76, an activated carbon adsorption tower 77, a discharge tank 78, and chemical tanks 81, 82, 83, 84 such as a flocculant, an insolubilizing agent, and a solidifying agent.

  The secondary cyclone over water pumped out from the classification plant 40 is fed with a flocculant from the chemical tank 81 and is stirred and mixed in the coagulation tank 61. As the flocculant, for example, an inorganic flocculant such as polyaluminum chloride (PAC) can be used. The secondary cyclone over water mixed with the flocculant is stored in the mud storage tank 62, and fine particles such as silt and clay that become floating substances are precipitated.

  The sediment and supernatant of the mud storage tank 62 are applied to a dewatering device 63 and separated into a dewatered cake and filtered water. The dehydrated cake is put into the mixing tank 64, and an insolubilizing agent such as aluminum sulfate and a solidifying agent such as cement are mixed from the chemical tank 82. The insolubilizing agent prevents nitrogen and phosphorus in the dehydrated cake from dissolving in water. The solidifying agent granulates the dehydrated cake to reduce the volume, and prevents the substances in the dehydrated cake from dissolving in water.

  The reduced dehydrated cake is backfilled to the bottom 7 of the dam lake.

  The filtrate is stored in the filtrate tank 71 and pumped out to the agglomeration reaction tank 72 by a pump. In the agglomeration reaction tank 72, an inorganic flocculant such as PAC or a flocculant such as a polymer flocculant is charged from the chemical tanks 83 and 84 and stirred.

  The filtrate into which the flocculant is charged is stored in a precipitate separation layer and separated into a precipitate and a supernatant. The sediment is pumped out to the mud tank 62 by a pump. The supernatant is stored in the aeration tank 74, air is blown in by a blower, and organic substances in the water are decomposed by aerobic bacteria.

  The supernatant into which the air has been blown is stored in the raw filtration tank 75, impurities in the water are removed by the filtration tower 76 and the activated carbon adsorption tower 77, stored in the discharge tank 78, and then discharged to the dam lake 6 and downstream of the dam. Is done.

  According to the dam dredging plant mentioned above, dredged soil is classified, and stones, gravel, sand, etc. are used as construction materials, etc., and fine particles of any particle size are discharged as river supply agents. Can also be used for the environment of the coast near the estuary and downstream. In addition, the remaining silt and clay are insolubilized, volume-reduced, and solidified and returned to the dam lake bottom 7, eliminating the need for a disposal site and reducing transportation costs.

  In the dam dredging plant of the present invention, the dredging device provided with the sand pump 23 inside the grab bucket 10 is used, but the present invention is not limited to this, and any dredging device can be used.

  In the classification plant 40, two-stage filters are used, but the number of filters may be further increased. Also, the filter eye size can be arbitrarily changed. In addition, classification is performed using two-stage cyclones, but the cyclone stages may be further increased or decreased depending on the target soil quality.

  Of course, chemicals such as a flocculant, an insolubilizing agent and a solidifying agent used in the water purification plant 60, various treatment tanks and other specific detailed structures can be changed as appropriate.

It is a part of flowchart which shows the process by the dam dredging plant of this invention, and is a schematic diagram which shows the dredging apparatus of the dam vicinity. It is a flowchart which shows the process by a classification plant equally. It is a flowchart which shows the process by a water purification plant. It is a schematic diagram which shows the example of a dredge apparatus used with the dam dredge plant of this invention. It is a schematic diagram which shows the conventional scissors method.

Explanation of symbols

1 Dredge equipment (grab ship)
10 Grab bucket 22 Mud hose 23 Sand pump 40 Classification plant 60 Water purification plant 64 Mixing tank

Claims (8)

  It comprises a dredging device that dredged sediment at the bottom of a dam lake, and a classification plant that separates fine sand particles of arbitrary particle size from the dredged soil dredged by the dredging device. Dam plant.   The classification plant is provided with a water discharge route for discharging a part of the dam lake water pumped together with the earth and sand from the dam lake bottom to the dam downstream, and a water purification plant for purifying the dam lake water pumped together with the earth and sand from the dam lake bottom. Dam plant.   The said water purification plant is equipped with the mixing tank which mixes an insolubilizing agent and a solidification agent with the floating substance removed from the dam lake water, The dam dredging plant of Claim 2 characterized by the above-mentioned.   2. The dredging device includes a grab bucket, a sand pump having a suction port in the grab bucket, and a mud feeding hose having one end connected to the sand pump and the other end provided on the water. The dam dredging plant as described in any one of -3.   A method for dredging a dam characterized by dredging sediment at the bottom of a dam lake, separating sediment with a large particle size from the dredged sediment, and classifying fine particles with an arbitrary particle size and supplying them to a river.   6. The method for dredging a dam according to claim 5, wherein an arbitrary amount of the dam lake water pumped up together with the sediment at the bottom of the dam lake is discharged downstream of the dam and the remaining dam lake water is purified.   Remove floating substances from the dam lake water pumped up with the sediment at the bottom of the dam lake, mix insoluble and solidifying agents with this floating substance to insolubilize, solidify and reduce the volume, and then backfill to the dam lake bottom. The method for dredging a dam according to claim 5 or 6, characterized by the above.   Excavate the sediment at the bottom of the dam lake with the grab bucket, then spout water into the grab bucket with the grab bucket closed, stir the sediment, and transport the stirred sediment to the water with the sand pump inside the grab bucket. The method of dredging a dam according to any one of claims 5 to 7, wherein dredging the sediment on the bottom of the dam lake is repeated.

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