A foundation pit excavation sandy soil washing and filtering purification separation system and method

Abstract

The present application relates to the technical field of foundation pit construction, in particular to a kind of foundation pit excavation sandy soil washing filtration purification separation system and method, it includes feeding device, separation device, sand washing device and dehydration device;The feeding device includes cleaning pool and chain bucket conveyor for transporting residual mud and slag soil in the cleaning pool to the separation device in one end in the cleaning pool, the separation device includes cylinder screen for screening and separating the particle size of residual mud and slag soil conveyed by chain bucket conveyor, the sand washing device is used to clean fine material screened by cylinder screen, and the dehydration device includes dehydration screen for vibration dehydration of fine sand cleaned by sand washing device, can separate mud and sand in the sandy soil excavated near foundation pit construction site, separated product sand can be reused, with significant economic benefits;And the waste mud and slag generated has high degree of reduction compared to transportation construction residual mud, and low water content, convenient transportation, greatly saves transportation cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit construction, in particular to a kind of sandy soil washing filter purification separation system and method for foundation pit excavation. BACKGROUND

[0002] With the rapid development of urban construction, a large number of high-rise buildings are built in various places, and more and more deep foundation pits appear in people's vision, which is accompanied by a large amount of residual mud and slag soil produced in the excavation process.

[0003] The traditional residual mud and slag soil treatment is transported to the government designated residual mud and slag soil receiving field for backfilling. The setting of the residual mud and slag soil receiving field will occupy a large amount of land resources, and the receiving field will produce a large amount of environmental and safety problems in the operation process. For example, due to the increasing shortage of urban land resources, the number of residual mud and slag soil receiving fields is limited, which is usually set in remote locations, and the residual mud and slag soil needs to be transported for a long distance, which consumes a lot of time and energy, occupies the valuable road resources of the city, and causes the city municipal pipe network to be blocked and the environment to be polluted due to the insufficient receiving field. At the same time, due to the high body and large blind area of the mud truck, traffic accidents caused by the mud truck often occur. In addition, with the government's regulation of the environment and water environment, the exploitation of river sand has been curbed, and the price of building materials market is rising. The residual mud and slag soil contains part of the available sand, which can be used for construction, municipal engineering, etc. after effective treatment, and the separated finished sand can effectively alleviate the current shortage of sand supply on the market, which has great social and economic benefits. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application provides a kind of sandy soil washing filter purification separation system and method for foundation pit excavation, which can separate the excavated sandy soil into mud and sand near the foundation pit construction site, the separated finished sand can be reused, which has significant economic benefits. The waste mud and slag produced has a high degree of reduction compared to the transportation of construction residual mud, and has a low water content, which is convenient to transport and greatly saves the transportation cost.

[0005] The technical solution adopted by the present application to solve its technical problems is:

[0006] A kind of sandy soil washing filter purification separation system for foundation pit excavation, which includes feeding device, separation device, sand washing device and dewatering device. The feeding device includes a cleaning pool and a chain bucket conveyor arranged in the cleaning pool for conveying the residual mud and slag soil in the cleaning pool to the separation device. The separation device includes a drum screen for screening and separating the particle size of the residual mud and slag soil conveyed by the chain bucket conveyor. The sand washing device is used for cleaning the fine material screened by the drum screen. The dewatering device includes a dewatering screen for vibrating dewatering of the fine sand cleaned by the sand washing device.

[0007] The separating device further comprises a crusher for crushing the coarse material screened out by the drum screen, and a first conveying belt assembly arranged between the coarse material outlet of the drum screen and the feeding port of the crusher, the crusher is arranged above the cleaning pool, and the discharging port of the crusher is directed towards the cleaning pool.

[0008] The sand washing device comprises a first water wheel sand washer, a second water wheel sand washer and a third water wheel sand washer arranged in sequence, the first water wheel sand washer is arranged near one side of the drum screen, the third water wheel sand washer is arranged near one side of the dehydration screen, and the fine material outlet of the drum screen is directed towards the feeding port of the first water wheel sand washer.

[0009] The sand washing device further comprises a slurry pool, and the slurry discharge ports of the first water wheel sand washer, the second water wheel sand washer and the third water wheel sand washer are communicated with the slurry pool through pipelines.

[0010] The sand washing device further comprises a first cyclone, the first cyclone is used for separating fine sand in the slurry and feeding the fine sand into the third water wheel sand washer, the feeding port of the first cyclone is communicated with the slurry pool through a pipeline, and the residue discharge port of the first cyclone is directed towards the third water wheel sand washer.

[0011] The application further discloses a sand washing, filtering, purifying and separating method for excavated sandy soil of a foundation pit, which comprises the following steps:

[0012] Step one: delivering residual slurry waste of the foundation pit into the cleaning pool for dilution;

[0013] Step two: delivering the diluted residual slurry waste into the drum screen through the chain bucket conveyor for screening, and feeding fine material with a diameter less than 4 mm screened out by the drum screen into the sand washing device;

[0014] Step three: delivering the fine sand washed by the sand washing device into the dehydration screen for vibration dehydration, and outputting the finished sand after dehydration by the conveying belt device.

[0015] In step two, the coarse material with a diameter greater than 4 mm screened out by the drum screen is fed into the crusher for crushing, and the crushed sand is re-delivered into the cleaning pool.

[0016] In step three, the sand washing device comprises a first water wheel sand washer, a second water wheel sand washer and a third water wheel sand washer arranged in sequence, and the fine material screened out by the drum screen is sequentially washed by the first water wheel sand washer, the second water wheel sand washer and the third water wheel sand washer.

[0017] The waste mud produced in the sand washing process is conveyed to the first cyclone for separation, the fine sand with a diameter greater than 4mm separated by the first cyclone is conveyed to the third water wheel sand washer, and then is sent to the dehydration screen for vibration dehydration, and finally is output.

[0018] The mud separated by the cyclone is dehydrated in the belt filter, and finally the mud residue with low water content is obtained.

[0019] The beneficial effects of the present application are:

[0020] 1. The foundation pit excavation sandy soil washing, filtering, purifying and separating system and method can be directly arranged in the foundation pit site or the surrounding position, realizes the nearby treatment of the sandy soil excavated from the foundation pit, reduces the influence of the mud head vehicle on the busy municipal traffic, and saves energy and protects the environment.

[0021] 2. The foundation pit excavation sandy soil washing, filtering, purifying and separating system and method separates the excavated sandy soil into mud and sand, realizes the waste into treasure, realizes the resource recycling, the separated finished sand can be used for construction, municipal engineering and the like, can effectively alleviate the problem of insufficient sand supply on the market, and has great social and economic benefits.

[0022] 3. The main and auxiliary machines used in the foundation pit excavation sandy soil washing, filtering, purifying and separating system and method are domestic standard equipment, the mechanical equipment automatically operates, the operation is simple, and only three workers are needed to complete the whole process of soil washing, filtering and purifying.

[0023] 4. By using the foundation pit excavation sandy soil washing, filtering, purifying and separating system and method, the sand and water in the sandy soil are separated, the waste mud residue with low water content is finally produced, the waste mud residue is transported to the designated position, compared with the treatment method of directly transporting the construction residual mud, the degree of reduction is high, the water content is low, the transportation is convenient, and the transportation cost is greatly saved. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present application will be further described below in combination with the drawings and examples.

[0025] Figure 1 is a schematic diagram of an embodiment of the present application;

[0026] Figure 2 is a construction flow chart of an embodiment of the present application.

[0027] Explanation of reference signs: 11, cleaning pool; 12, chain bucket conveyor; 13, feeding hopper; 14, screen; 15, slurry storage pool; 16, second cyclone; 21, drum screen; 22, crusher; 23, first conveying belt assembly; 31, first water wheel sand washer; 32, second water wheel sand washer; 33, third water wheel sand washer; 34, slurry pool; 35, first cyclone; 41, dewatering screen; 42, belt filter press; 43, slurry storage tank; 44, chemical pool; 45, clean water pool. DETAILED DESCRIPTION

[0028] The concept, specific structure and generated technical effects of the present application will be described clearly and completely in combination with the embodiments and the drawings, so as to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments, and other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative labor are within the scope of protection of the present application. In addition, all the coupling / connection relationships involved in the patent do not mean that the components are directly connected, but that a better coupling structure can be composed by adding or reducing coupling accessories according to the specific implementation situation. The technical features in the present application can be combined interactively without conflict.

[0029] A foundation pit excavation sandy soil washing and filtering purification separation system, as shown in Figure 1 The feeding device includes a cleaning pool 11 and a chain bucket conveyor 12 arranged in the cleaning pool 11 and used for conveying residual mud and soil in the cleaning pool 11 to the separation device. The separation device includes a drum screen 21 used for screening and separating the particle size of the residual mud and soil conveyed by the chain bucket conveyor 12. Specifically, the drum screen 21 screens the residual mud and soil into coarse material with a particle size greater than 4 mm and fine material with a particle size less than 4 mm. The sand washing device is used for cleaning the fine material screened by the drum screen 21. The dewatering device includes a dewatering screen 41 used for vibration dewatering of the fine sand cleaned by the sand washing device.

[0030] The feeding device further includes a feeding hopper 13 connected with the cleaning pool 11. A reinforcing screen 14 for filtering the residual mud and soil is arranged at the opening of the feeding hopper 13. In order to facilitate the large-particle impurities filtered to automatically fall off the screen 14, the screen 14 is arranged obliquely.

[0031] The feeding device further includes a slurry storage pool 15 connected with the upper part of the cleaning pool 11 through a pipeline. The slurry storage pool 15 is used for storing the slurry in the upper part of the cleaning pool 11.

[0032] The feeding device further comprises a second cyclone 16 arranged above the chain bucket conveyor 12 and a second high-pressure pump (not shown in the figure) for pumping the slurry in the slurry storage tank 15 into the second cyclone 16, the slurry storage tank 15 is connected with the feeding port of the second cyclone 16 through a pipeline, the slurry discharge port of the second cyclone 16 is connected with the dewatering device, and the residue discharge port of the second cyclone 16 is directed towards the chain bucket conveyor 12. The slurry in the slurry storage tank 15 is pumped into the second cyclone 16 by the second high-pressure pump, and the sand particles with a diameter greater than 4 mm in the slurry are directly dropped into the chain bucket through centrifugal action, and the remaining slurry flows to the dewatering device for dewatering.

[0033] The separation device further comprises a crusher 22 for crushing the coarse material screened out by the drum screen 21 and a first conveying belt assembly 23 arranged between the coarse material outlet of the drum screen 21 and the feeding port of the crusher 22, the crusher 22 is arranged above the cleaning tank 11, and the discharge port of the crusher 22 is directed towards the cleaning tank 11.

[0034] The sand washing device comprises a first water wheel sand washing machine 31, a second water wheel sand washing machine 32 and a third water wheel sand washing machine 33 arranged in sequence, the first water wheel sand washing machine 31 is arranged near one side of the drum screen 21, the third water wheel sand washing machine 33 is arranged near one side of the dewatering screen 41, and the fine material outlet of the drum screen 21 is directed towards the feeding port of the first water wheel sand washing machine 31.

[0035] The sand washing device further comprises a slurry tank 34, and the slurry discharge ports of the first water wheel sand washing machine 31, the second water wheel sand washing machine 32 and the third water wheel sand washing machine 33 are respectively communicated with the slurry tank 34 through pipelines. Specifically, the slurry tank 34 is connected with the bottom of the slurry storage tank 15 through a pipeline, the size of the slurry storage tank 15 is 1.0m×1.0m×1.2m, when the slurry in the slurry storage tank 15 is too much, the slurry in the slurry storage tank 15 flows into the slurry tank 34 through the pipeline for storage, so as to prevent the slurry in the slurry storage tank 15 from overflowing.

[0036] The sand washing device further comprises a first cyclone 35 and a first high-pressure pump (not shown in the figure) for pumping the slurry in the slurry tank 34 into the first cyclone 35, the first cyclone 35 is used for separating fine sand in the slurry and sending the fine sand to the third water wheel sand washing machine 33, the feeding port of the first cyclone 35 is communicated with the slurry tank 34 through a pipeline, the residue discharge port of the first cyclone 35 is directed towards the third water wheel sand washing machine 33, and the slurry discharge port of the first cyclone 35 is connected with the dewatering device. In this embodiment, three first cyclones 35 are arranged, and the three first cyclones 35 are arranged between the second water wheel sand washing machine 32 and the third water wheel sand washing machine 33.

[0037] The dewatering device further comprises a belt filter 42 for pressure filtration and dewatering of the mud discharged from the first cyclone 35 and the mud discharged from the second cyclone 16, the belt filter 42 squeezes the water in the mud dry to form mud residue with low water content, and then the mud residue is transported to a designated location by a mud truck for disposal, and the load of the mud truck can be effectively reduced due to the low water content in the mud residue.

[0038] The dewatering device further comprises a slurry storage tank 43 for storing the mud discharged from the first cyclone 35 and the mud discharged from the second cyclone 16, the feed inlet of the slurry storage tank 43 is connected with the slurry discharge port of the first cyclone 35 and the slurry discharge port of the second cyclone 16, and the discharge outlet of the slurry storage tank 43 is connected with the belt filter 42. Specifically, the discharge outlet of the slurry storage tank 43 is arranged at the bottom of the slurry storage tank 43.

[0039] The dewatering device further comprises a medicament pool 44 for storing flocculants, the discharge outlet of the medicament pool 44 is connected with the slurry storage tank 43, and specifically, the flocculants are stored in the medicament pool 44, the flocculants are delivered to the slurry storage tank 43 through the medicament pool 44, the mud in the slurry storage tank 43 is fully precipitated and flocculated into groups, the water in the upper layer of the slurry storage tank 43 is cleaner and clearer, and can be used for cleaning the cleaning pool 11 and the first water wheel sand washer 31, the second water wheel sand washer 32 and the third water wheel sand washer 33 for reuse.

[0040] The dewatering device further comprises a clean water pool 45, which is used for collecting the clean water in the upper part of the slurry storage tank 43 and the clean water generated in the squeezing process of the belt dewatering machine, the clean water stored in the clean water pool 45 can be further delivered to the cleaning pool 11 and the first water wheel sand washer 31, the second water wheel sand washer 32 and the third water wheel sand washer 33 for reuse, thereby saving resources.

[0041] The construction method of the above-mentioned foundation pit excavation sandy soil washing, filtering, purifying and separating system, as shown in Figure 2 , comprises the following steps:

[0042] Step S1, residual mud residue storage

[0043] A large amount of residual mud residue is generated during the excavation of a deep foundation pit project. In order to not affect the on-site construction and to facilitate the transportation of the finished sand, the entire treatment site is set separately from the project site, the residual mud residue treatment site is set near the project site, and the foundation pit soil on site is transported to the treatment site by a mud truck for centralized stacking. The size of the residual mud residue stacking site can be determined according to the actual situation of the project site.

[0044] Step S2, residual mud residue net screening pretreatment

[0045] The residual sludge is put into the feeding hopper by the excavator. A large steel mesh is arranged above the feeding hopper to filter out the large stones in the residual sludge to prevent damaging the equipment.

[0046] Step S3, dilution of residual sludge

[0047] The residual sludge enters the cleaning pool through the feeding hopper, and is settled at the bottom of the cleaning pool after being diluted by water. Part of the sludge is mixed with water and flows into the slurry storage pool through the upper pipeline.

[0048] One end of the chain bucket conveyor is placed in the cleaning pool at a certain depth so as to be in contact with the residual sludge diluted at the bottom of the cleaning pool. After the bucket of the chain bucket conveyor is dug, the bucket is lifted out of the water surface with the rotation of the bucket chain of the chain bucket conveyor, and is conveyed to the top. After the direction of the chain bucket conveyor is changed by the upper guide wheel, the sludge in the chain bucket of the chain bucket conveyor is poured into the drum screen under the gravity of the sludge itself.

[0049] The slurry in the slurry storage pool is pumped to the second cyclone by the second high-pressure pump. The second cyclone is arranged above the chain bucket conveyor. After centrifugal action, the sand particles with a diameter greater than 4 mm directly fall into the chain bucket of the chain bucket conveyor, and the slurry flows into the slurry storage tank. The size of the slurry storage pool is 1.0 m x 1.0 m x 1.2 m. When there is too much slurry in the slurry storage pool, the slurry flows into the slurry pool.

[0050] Step S4, primary screening by drum screen

[0051] The residual sludge after dilution is transported to the drum screen by the chain bucket conveyor. The drum screen is placed obliquely, and water is sprayed into the drum screen by the spraying device while the drum screen is rolling, so as to achieve the purpose of preliminary washing.

[0052] The drum screen used in the method is GS1830, and the technical parameters of the drum screen are shown in Table 1.

[0053] Table 1 Technical parameters of GS1830 drum screen

[0054]

[0055] After the material enters the drum screen, the material on the screen surface can be continuously turned over due to the inclination and rotation of the drum screen. The coarse material with a particle size greater than 4 mm is discharged through the coarse material outlet of the drum, and the fine material with a particle size less than 4 mm is discharged from the lower end of the screen hole, i.e. the fine material outlet, and enters the sand washing device for the next step of washing.

[0056] The coarse material discharged from the drum screen is transported to the hammer crusher by the conveyor belt device, and then is sent into the cleaning pool and is transported to the drum screen by the chain bucket conveyor for screening.

[0057] The turning and rolling of the material in the drum of the drum screen with the model of GS1830 can make the material stuck in the screen hole be bounced out, so as to prevent the screen hole from being blocked.

[0058] Step S5, sand washing device washing sand

[0059] The sand washing device comprises a first water wheel sand washing machine, a second water wheel sand washing machine and a third water wheel sand washing machine arranged in sequence.

[0060] Specifically, the fine material with a diameter less than 4 mm separated by the roller screen is transported into the first water wheel sand washing machine, and the fine material sequentially passes through the cleaning of the first water wheel sand washing machine, the second water wheel sand washing machine and the third water wheel sand washing machine, and the fine sand is carried away by the blades of the third water wheel sand washing machine and then poured into the dehydration screen, and after being vibrated and dehydrated by the dehydration screen, the fine sand is transported to the empty land by the conveyor belt device. The mud produced in the sand washing process is pumped into the mud pool for further treatment. The mud pool receives the mud filtered by the first water wheel sand washing machine, the second water wheel sand washing machine and the third water wheel sand washing machine, and the size of the mud pool meets the working capacity of the sand washing device.

[0061] The sand washing device used in the method adopts XS2800, and the treatment technical index is shown in Table 2.

[0062] Table 2 Technical parameter table of sand washing device

[0063]

[0064] In the sand washing process, the impeller of the water wheel sand washing machine slowly rotates under the action of the motor, the sand is transferred from the feeding groove into the sand washing groove, rolls and grinds each other under the driving of the impeller, so as to facilitate the removal of impurities covering the surface of the sand, and at the same time, the water vapor layer covering the sand particles is destroyed to facilitate dehydration. On the other hand, the impeller can bring the water in the previous sand washing groove into the next sand washing groove to add water in the next sand washing groove. The strong water flow timely carries away the impurities and foreign matters with small specific gravity produced in the sand washing process, and the clean sand is carried away by the blades and then poured into the dehydration screen.

[0065] Step S6, mud washing and filtering treatment

[0066] S6a. Before the mud squeezing and filtering, the first cyclone is used to pretreat the mud.

[0067] The three first cyclones are arranged between the second water wheel sand washing machine and the third water wheel sand washing machine, and use the centrifugal sedimentation principle to further separate and treat the waste mud in the mud pool. The coarse particles with a diameter greater than 4 mm in the mud are directly dropped into the third water wheel sand washing machine from the discharge port of the first cyclone for further washing and filtering, and then sent to the dehydration screen for vibration dehydration from the third water wheel sand washing machine, and finally output, while the mud separated by the first cyclone is directly pumped into the mud storage tank for storage.

[0068] S6b. After the mud treated by the first cyclone, it is first put into the slurry storage tank, and is precipitated, dewatered and flocculated into a concentrated mud slurry under the flocculation of the flocculants polyacrylamide and polyaluminum chloride in the slurry storage tank, and then flows to the distributor of the belt filter press from the bottom of the slurry storage tank. The water discharged from the mud slurry in the process of dewatering in the belt filter press continuously penetrates the filter cloth and falls into the clean water tank, and the filtered water can be used on site for the second time. The mud residue after dewatering is transported to the outside by the conveyor belt device, and the water content is less than 20%, which can be directly transported to the designated place by the earth car for disposal in the later period.

[0069] The mud slurry is precipitated, dewatered and flocculated into a concentrated mud slurry under the flocculation of the flocculants polyacrylamide and polyaluminum chloride in the slurry storage tank, and then flows to the gravity dewatering section of the belt filter press through the distributor. Under the action of gravity, the free water penetrates the back of the filter screen and is separated, and the sludge on the filter screen forms a non-flowing sludge, which is then clamped between the upper and lower screen belts as the screen belt moves. The filter belt has adjustable tension, and the diameter of the rotating roller and the counter roller gradually decreases. The continuous slow counter-roller extrusion force and shear force are continuously increased through the wedge-shaped area, low-pressure area, medium-pressure area, high-pressure area and strong counter-roller extrusion area, and finally the filter cake with low water content is discharged.

[0070] In summary, the present application has the following beneficial effects:

[0071] 1. The foundation pit excavation sandy soil washing, filtering, purifying and separating system and method can be directly arranged in the foundation pit site or the surrounding position, realizes the nearby treatment of the sandy soil excavated from the foundation pit, reduces the influence of the mud truck on the busy municipal traffic, and saves energy and protects the environment.

[0072] 2. The foundation pit excavation sandy soil washing, filtering, purifying and separating system and method separates the excavated sandy soil into mud and sand, realizes the recycling of waste, realizes resource recycling and utilization, and the separated finished sand can be used for construction, municipal engineering and the like, can effectively alleviate the problem of insufficient sand supply on the market, and has great social and economic benefits.

[0073] 3. The main and auxiliary machines used in the foundation pit excavation sandy soil washing, filtering, purifying and separating system and method are domestic standardized equipment, the mechanical equipment automatically operates, and the operation is simple, and only three workers are needed to complete the whole process of soil washing, filtering and purifying.

[0074] 4. By using the foundation pit excavation sandy soil washing, filtering, purifying and separating system and method, the sand and water in the sandy soil excavated from the foundation pit are separated, finally the waste mud residue with low water content is produced, and the waste mud residue is transported to the designated place. Compared with the treatment method of directly transporting construction residual mud, the degree of reduction is high, the water content is low, the transportation is convenient, and the transportation cost is greatly saved.

[0075] The above is a specific description of the preferred embodiments of the present application, but the present application is not limited to the described embodiments, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A foundation pit excavation sandy soil washing and filtering purification separation system, characterized in that: The device comprises a feeding device, a separating device, a sand washing device and a dehydration device; the feeding device comprises a cleaning pool and a chain bucket conveyor arranged in the cleaning pool and used for conveying residual mud and soil in the cleaning pool to the separating device; the separating device comprises a drum screen used for screening and separating the particle size of the residual mud and soil conveyed by the chain bucket conveyor; the sand washing device is used for cleaning the fine material screened by the drum screen; and the dehydration device comprises a dehydration screen used for vibrating dehydration of the fine sand cleaned by the sand washing device; The feeding device further comprises a slurry storage pool and a second cyclone; the slurry storage pool is connected with the upper part of the cleaning pool through a pipeline; the slurry storage pool is used for storing the mud slurry in the upper part of the cleaning pool; and the slurry storage pool is connected with the feeding port of the second cyclone through a pipeline; The sand washing device comprises a mud slurry pool and a first cyclone; the mud slurry pool is connected with the bottom of the slurry storage pool through a pipeline; and the feeding port of the first cyclone is communicated with the mud slurry pool through a pipeline; The sand washing device further comprises a first water wheel sand washer, a second water wheel sand washer and a third water wheel sand washer arranged in sequence; the first water wheel sand washer is arranged on the side close to the drum screen; the third water wheel sand washer is arranged on the side close to the dehydration screen; the fine material outlet of the drum screen is directed to the feeding port of the first water wheel sand washer; and the slurry discharge ports of the first water wheel sand washer, the second water wheel sand washer and the third water wheel sand washer are respectively communicated with the mud slurry pool through pipelines; The dehydration device further comprises a slurry storage tank, a reagent pool and a belt filter press; the feeding port of the slurry storage tank is connected with the slurry discharge ports of the first cyclone and the second cyclone; the discharge port of the reagent pool is connected with the slurry storage tank; the reagent pool stores flocculants; the discharge port of the slurry storage tank is connected with the belt filter press; and the belt filter press is used for pressure filtration and dehydration of the mud slurry to a filter cake with a water content of less than 20%.

2. A system for washing, filtering, purifying and separating sandy soil for foundation excavation according to claim 1, characterized in that: The separating device further comprises a crusher used for crushing the coarse material screened by the drum screen and a first conveying belt assembly arranged between the coarse material outlet of the drum screen and the feeding port of the crusher; the crusher is arranged above the cleaning pool; and the discharge port of the crusher is directed to the cleaning pool.

3. A system for washing, filtering, and purifying sandy soil for excavation of a foundation pit according to claim 1, characterized in that: The first cyclone is used for separating the fine sand in the mud slurry and sending the fine sand to the third water wheel sand washer; and the residue discharge port of the first cyclone is directed to the third water wheel sand washer.

4. A method of washing, filtering, purifying and separating sandy soil for foundation excavation, characterized by: The foundation pit excavation sandy soil washing and filtering purification separation system based on any one of claims 1-3 comprises the following steps: Step one, residual mud and soil in the foundation pit is conveyed to the cleaning pool for dilution; after water dilution, the residual mud and soil is settled at the bottom of the cleaning pool; part of the mud is mixed with water and flows into the slurry storage pool through the upper pipeline; the mud slurry in the slurry storage pool is pumped to the second cyclone by a second high-pressure pump; the second cyclone is arranged above the chain bucket conveyor; through centrifugal action, sand particles with a diameter greater than 4 mm directly fall into the chain bucket of the chain bucket conveyor; and the mud slurry flows into the slurry storage tank; Step two, the diluted residual sludge is transported to the drum screen by the chain bucket conveyor for screening, the fine material with a diameter less than 4mm separated by the drum screen is sent to the sand washing device, the first cyclone of the sand washing device pre-treats the slurry, and the slurry treated by the first cyclone is first sent to the slurry storage tank; the slurry in the slurry storage tank is precipitated, dewatered and flocculated into a concentrated slurry under the flocculation of the flocculant, and then flows from the bottom of the slurry storage tank to the distributor of the belt filter press, the belt filter press implements a continuous slow roller extrusion force and shear force through the filter belt with adjustable tension, rollers with gradually decreasing diameters and counter rollers, and the water in the sludge is continuously extruded through the wedge area, low pressure area, medium pressure area, high pressure area and strong roller extrusion area, and finally the filter cake with a water content of less than 20% is discharged; Step three, the fine sand washed by the sand washing device is conveyed to the dewatering screen for vibration dewatering, and the finished sand after dewatering is output by the conveyor belt device.

5. A method of washing, filtering, purifying and separating sand soil for foundation excavation according to claim 4, characterized in that: In step two, the coarse material with a diameter greater than 4mm separated by the drum screen is sent to the crusher for crushing, and the crushed sand is re-conveyed to the cleaning pool.

6. A method of washing, filtering, purifying and separating sand soil for foundation pit excavation according to claim 4, characterized in that: In step three, the sand washing device includes a first water wheel sand washer, a second water wheel sand washer and a third water wheel sand washer arranged in sequence, and the fine material separated by the drum screen is sequentially cleaned by the first water wheel sand washer, the second water wheel sand washer and the third water wheel sand washer.

7. A method of washing, filtering, purifying and separating sand soil for foundation pit excavation according to claim 6, characterized in that: The waste slurry generated during the sand washing process is conveyed to the first cyclone for separation, and the fine sand with a diameter greater than 4mm separated by the first cyclone is conveyed to the third water wheel sand washer.

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