CN111908748A

CN111908748A - River channel dredging method

Info

Publication number: CN111908748A
Application number: CN202010766935.6A
Authority: CN
Inventors: 米卫星; 张义周
Original assignee: China Construction Water Affairs Environmental Protection Co Ltd
Current assignee: China Construction Water Affairs Environmental Protection Co Ltd
Priority date: 2020-08-03
Filing date: 2020-08-03
Publication date: 2020-11-10

Abstract

The invention relates to the technical field of river channel dredging, in particular to a river channel dredging method, which comprises the following steps: carrying out cofferdam division on a riverway to be cleaned, and carrying out sectional dredging by adopting a cutter suction pumping and hydraulic excavation auxiliary mode; sequentially carrying out primary precipitation, sorting and flocculating precipitation on the cleaned mud water to obtain purified sludge; and (4) dehydrating and tedding the purified sludge in sequence, and backfilling mud cakes obtained by tedding. The river dredging method adopts a physical and chemical combined treatment process, skillfully combines the two methods, can effectively treat heavy metal ions such as arsenic, copper, chromium and the like in the sediment, realizes harmless and resource treatment of the sediment, can prevent secondary pollution caused by the fact that the sediment is discarded without being treated, can effectively utilize the sediment, enhances the flood-carrying dredging capability of the river, solves the problem of difficult treatment of sediment pollution of the river, and achieves the purposes of reducing, stabilizing, harmless and resource treatment of pollutants.

Description

River channel dredging method

Technical Field

The invention relates to the technical field of river channel dredging, in particular to a river channel dredging method.

Background

The river course is an important component of the city and plays a decisive role in flood control, waterlogging prevention and urban environment optimization. However, with the development of economy and the continuous acceleration of urbanization, people destroy vegetation to cause water and soil loss, and deposit domestic garbage and various building silt into the river along the river, which leads to continuous sedimentation at the bottom of the river, and the water body is gradually black and smelly, which affects the flood safety and the landscape of the river, and seriously threatens the stability of the river ecosystem and the human living environment, so that the comprehensive regulation of the river gradually draws attention of people.

The river sediment has the characteristics of high water content, fine particles, strong rheological property, high nutrient content, large deposition, strong toxicity and environmental harmfulness and the like, and is easy to degrade to generate stink. The toxicity and harm of the bottom mud mainly come from the fact that the bottom mud contains a large amount of pathogenic microorganisms, organic pollutants, hard-to-degrade heavy metals and the like, and secondary pollution and ecological risks are easily caused; moreover, the river channel dredging project is used as a preposed process of the river channel comprehensive treatment project, and the subsequent bank slope reconstruction, the sewage interception project, the landscape lifting and the like are all based on the preposed process. Therefore, the work of dredging the river channel is imperative.

At present, the technical measures for dredging the river channel are mainly divided into dry dredging, water dredging and environment-friendly dredging. The dry dredging refers to pumping out river water, thoroughly exposing bottom mud on the surface, then digging out through a machine, transferring to a treatment station for centralized treatment, and the method has the advantages of high speed, more thorough sludge concentration and the like. The water dredging is that the dredger type dredging equipment is utilized to convey excavated sludge to an engineering designated position for treatment, and modes such as grab bucket type, cutter suction type or pump suction type are generally adopted, wherein the grab bucket type is generally applied to dredging and dredging engineering of medium and small river channels, the dredging effect of the river channels with thicker sludge layers and more obstacles is more obvious, the dredging mode is more convenient to operate and is not basically influenced by weather change, the dredging effect cannot be influenced by too many obstacles in the river channels, but the sludge after stirring can be returned to the water area again, and the integral dredging efficiency is influenced. The cutter suction type dredging method has the advantages of high precision, difficulty in leakage of sludge, no influence on the original navigation operation of a river channel and the like, and is widely applied to medium-sized river channels. The pump suction type dredging method is suitable for most of small river channel sludge cleaning works, but the problem of excessive water absorption can occur in the dredging process, and great inconvenience is brought to subsequent slurry treatment. Therefore, when the water dredging technology is applied, the basic situation of the river channel needs to be comprehensively considered, and the most appropriate dredging method is selected, so that the dredging efficiency and effect are ensured. The environment-friendly dredging technology completely meets the environment-friendly requirement and the sustainable development strategy, the environment-friendly dredging is completed through specialized spiral dredging equipment, an environment-friendly cutter-suction cutter, sealed rotary bucket dredging and other equipment, the sludge in the river channel can be thoroughly cleared by fully utilizing hydrostatic pressure and compressed air, the adverse effect on the water body of the river channel can be reduced to the greatest extent by the device, higher dredging quality and dredging benefit can be realized, and the damage and the pollution to the environment around the river channel can be avoided. However, this method has problems of high implementation cost and low resource utilization rate.

Therefore, aiming at the problems that the existing dredging technology cannot accurately dredge, the sludge cannot be reasonably treated, tail water cannot be discharged after reaching the standard and the implementation cost is high, a novel river dredging method is developed, and the novel river dredging method is a technical problem which needs to be solved urgently in the field.

Disclosure of Invention

The invention aims to provide a river channel dredging method which essentially solves the problems of river channel siltation and endogenous pollution.

The invention provides a river channel dredging method, which comprises the following steps:

s1, carrying out cofferdam division on the riverway to be cleaned, and carrying out sectional dredging by adopting a cutter suction pumping and hydraulic excavation assisting mode;

s2, sequentially carrying out primary precipitation, sorting and flocculation precipitation on the cleaned mud water to obtain purified sludge;

and S3, sequentially dehydrating and tedding the purified sludge, and backfilling mud cakes obtained by tedding.

Aiming at riverways with poor water quality, high nitrogen and phosphorus content and high bottom sediment heavy metal content, the invention adopts a physical and chemical combined treatment method of water conservancy excavation, cutter suction pump segmented accurate desilting, bottom sediment flocculation precipitation, separation and dehydration, tedding and backfilling and the like, thereby achieving the purposes of reduction, stabilization, harmlessness and resource utilization. The dredging bottom mud is subjected to harmless and resource treatment and then backfilled in the range on two sides of the bank slope, so that the secondary environmental pollution caused by the abandonment of the bottom mud can be prevented, and the bottom mud can be effectively utilized, therefore, the river channel dredging method disclosed by the invention improves the current situation of river channel pollution, enhances the flood-carrying dredging capacity of the river channel, and fundamentally solves the problems of river channel sedimentation and endogenous pollution.

Further, in step S1, when the cofferdam is divided, the temporary cofferdam is used to divide the river into multiple sections by taking the plan view and the cross-sectional view of the river as the basis for dredging, and an intermediate pump station is arranged between each section.

In order to prevent secondary pollution caused by disturbance to surrounding undisturbed stratums in the dredging process of a river channel, pollution diffusion is reduced and back silting is prevented through building of segmented cofferdams, when the cofferdams are divided, a plane view and a section view of the river channel are used as dredging bases, a section surveying and mapping straight line section can be divided into 10-20m sections according to specific conditions of the river channel, a turning section is encrypted and surveyed according to 3-8m, considering that the river channel dredging is generally carried out in dry seasons, the water quantity in the river channel is small, the flow rate is low, the river channel can be divided into multiple sections through temporary cofferdams, and an intermediate pump station is arranged between each section so as to facilitate subsequent transportation and treatment of silt.

Further, in step S1, during the segmental dredging, the reamer head is firstly used to cut the bottom mud, the river water is taken and stirred by being assisted with water jetting of a high-pressure water gun, and finally the mud water on the bottom layer is cleaned out of the river channel in a manner of cutter suction pumping.

The cutter suction dredger is composed of a diesel engine, a gear pump, a gearbox, a mud pump, a reamer, a suction pipe and the like, and is mainly characterized in that sludge at the bottom of water is rotationally stirred by a reamer head to be in a boiling state, then the sludge is sucked and conveyed to a designated place through a pump pipe, a screen is arranged at a sludge suction inlet, and solids with large particle size and branches and leaves are prevented from entering the pump and the pipeline. The method has high working efficiency, can adapt to various terrain operations, has strong adaptability to slurry, can be directly connected in series with a sludge pump station for long-distance conveying, and has the pump selection according to the actual requirements on the site and fully considers the economical efficiency. The method has the advantages of more flexible spatial arrangement, high working efficiency, lower energy consumption and cost, and no pollution caused by sludge scattering by adopting pipeline transportation. And utilize the reamer head to carry out the sediment cutting to get river and stir through assisting the water jet of high-pressure squirt, can make sectional silt present mobility, clear up the muddy water of bottom out the river course through the mode of cutter suction pump sending at last, can reach the purpose of accurate desilting.

Further, in step S2, during the preliminary sedimentation, the sludge and water after being cleaned sequentially pass through the sedimentation tank with the height difference at the top of the multiple stages, so as to realize the preliminary separation of the sludge and water.

During preliminary sedimentation, during the mud water that can clear up had the sedimentation tank that there is the difference in height at multistage top through the elevator pump that cofferdam section intermediate arrangement temporarily, can ensure the holistic precipitation effect of silt on the one hand, and on the other hand, the supernatant between the multistage sedimentation is decided the pond and is passed through the mode of gravity overflow and get into next stage sedimentation tank, has reduced corresponding processing energy consumption.

Further, in step S2, the sludge obtained by the preliminary sedimentation is sorted to remove particulate matter with a diameter larger than 3 mm.

In order to prevent sand and sundries with the diameter more than 3mm from entering a subsequent pipeline and a treatment system to influence the dredging effect and possibly cause the damage of mechanical equipment, a sorting machine can be adopted to separate the sand and the sundries from the sludge obtained by preliminary sedimentation. The separated gravels can be used for manufacturing building blocks or other building materials after being crushed, and the sorted sundries are transported to a municipal refuse disposal station for centralized treatment.

Further, in step S2, during the flocculation, ferrous sulfate, polyaluminium chloride and polyacrylamide are sequentially added to the sorted muddy water.

In order to reduce the content of heavy metals and toxic and harmful substances in the sludge, the sorted mud water is treated by adopting a chemical flocculation precipitation mode, and in order to improve the flocculation effect and reduce the treatment cost, ferrous sulfate, polyaluminium chloride and polyacrylamide can be sequentially used for flocculation treatment. The dosage of each flocculating agent is determined according to the original detection result and a field beaker test, and under the normal condition, the dosage of ferrous sulfate is 0.5-2.5mg/L, the dosage of polyaluminium chloride is 0.5-2.0mg/L, and the dosage of polyacrylamide is 0.5-2.0mg/L, so that the flocculating and settling effect is optimal.

Further, in step S3, during the dewatering, the purified sludge is intercepted, concentrated and filter-pressed by a sludge solidification technology to obtain a thin cake-like sticky substance.

The current common sludge treatment methods comprise a natural dehydration drying method, a vacuum preloading method, a geotechnical tube bag method, a mechanical dehydration method, a sludge solidification method and the like, wherein the cost of the natural dehydration drying method is the lowest, but the natural dehydration drying method occupies a large area, has severe environmental influence and has high subsequent cost; the vacuum preloading construction process is simple, the direct treatment cost is low, but the occupied site is large, and the environmental impact is large; the geotechnical pipe bag method adopts self-weight compaction dehydration, so that the direct treatment cost is low, but the occupied site is large, and the environmental risk of pollution transfer exists; the mechanical dehydration method adopts mechanical pressure extrusion, and has high direct treatment cost and great environmental influence. Compared with the above technology, the sludge solidification method has the advantages of mature and stable technology, high treatment efficiency, low comprehensive cost and high automation degree. Therefore, the sludge solidification technology is adopted in the invention to carry out interception, concentration and filter pressing on the purified sludge so as to realize sludge-water separation.

Further, in step S3, when the thin pancake-shaped sticky substance is aired, the thin pancake-shaped sticky substance is crushed until the particle size is less than or equal to 5cm, and the thin pancake-shaped sticky substance can be backfilled after the water content of the thin pancake-shaped sticky substance meets the requirement.

When the mud cake is backfilled, the grain diameter and the water content of the mud cake are required to a certain extent, so that when the mud cake is turned over and aired, the mud cake can be crushed until the grain diameter is less than or equal to 5cm, and the mud cake can be backfilled after the water content meets the requirement, and the backfilling of the mud cake is not only beneficial to self-balancing of earthwork in a dredging project, but also beneficial to reducing the manufacturing cost and lowering the investment.

Further, the method also comprises tail water treatment, and specifically comprises the following steps: and sequentially passing the flocculating and settling effluent, the filter-pressing effluent and the tedding seepage water through the multistage sedimentation tank, and carrying out microbial treatment on clear water overflowing from the sedimentation tank.

The river channel dredging method also comprises the treatment of tail water, wherein the tail water comprises flocculation precipitation effluent, filter pressing effluent and tedding infiltration, the tail water can be directly and sequentially treated through a multi-stage sedimentation tank, and clear water overflowing from the final sedimentation tank contains a large number of microorganisms, so that the tail water can be directly discharged to an adjacent artificial wetland for advanced treatment and can also be discharged to municipal sewage pipe network facilities for further treatment.

Compared with the prior art, the river channel dredging method has the following advantages:

1. the river dredging method adopts a physical and chemical combined treatment process, skillfully combines the two methods, can effectively treat heavy metal ions such as arsenic, copper, chromium and the like in the bottom mud, and can prevent secondary environmental pollution caused by the disposal of the bottom mud and effectively utilize the bottom mud after harmless and resource treatment;

2. after the treatment by the method, the current situation of river pollution can be obviously improved, and river water is clear and has no obvious odor; the method for dredging the river channel can improve the current situation of river channel pollution, simultaneously enhance the flood-carrying dredging capability of the river channel, substantially solve the problems of river channel sedimentation and endogenous pollution, and achieve the purposes of reduction, stabilization, harmlessness and recycling.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a flow chart of the river dredging process of the present invention;

fig. 2 is a section view of the river channel dredging of the invention.

Description of reference numerals:

1: the dredging range; 2: a current dike; 3: designing a combined slope protection; 4: designing a footpath; 5: designing an embankment; 6: designing the elevation of the dredging bottom; 7: the current sludge state elevation; 8: and designing a flood line.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms also include the plural forms unless the context clearly dictates otherwise, and further, it is understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, devices, components, and/or combinations thereof.

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Taking old river channel dredging engineering in a certain region in Shenzhen city as an example, the river channel dredging method disclosed by the invention is adopted to carry out dredging and dredging engineering.

And S1, carrying out cofferdam division on the riverway to be cleaned, and carrying out sectional dredging by adopting a cutter suction pumping mode and a hydraulic flushing excavation mode.

Firstly, performing original topographic mapping on the river channel by using a total station, drawing a plan view and a section view of the river channel, and taking the plan view and the section view as a dredging basis. During surveying, the straight section surveying line section is used for surveying according to 15m cross section, and the turning section is used for encrypting and surveying according to 5 m. Because the river channel desilting is carried out in dry seasons, the water quantity in the river channel is small, the flow speed is low, the river channel is divided into multiple sections (the length of each section is controlled to be 300-500 m) by adopting the temporary cofferdam, and a pump station is arranged between the multiple sections. During cofferdam construction, river sludge is adopted, the height of the sludge is 0.5m higher than the river water level line, the width of a weir crest is 1m, the slope ratio of two sides is controlled to be about 1.5, meanwhile, river internal diversion is well made, and a diversion area is covered during lower-section dredging (a dredging section diagram is shown in figure 2);

during dredging, firstly, a reamer head is adopted to cut bottom mud, river water is taken to be assisted by a high-pressure water gun to jet water and stir, so that the mud close to the designed section is in fluidity, and finally, the maximum treatment capacity is 100m³The structure of a suction pipe, a slurry pump and the like of the cutter suction dredger of the/h cleans the muddy water at the bottom layer out of a river channel, and simultaneously, a GPS positioning system is adopted and an ECHO Sounder ECHO detector is used for controlling the section, so that the aim of accurately dredging is fulfilled.

And S2, sequentially carrying out primary precipitation, sorting and flocculating precipitation on the cleaned muddy water to obtain the purified sludge.

Firstly, primarily precipitating the cleaned mud water to realize the primary separation of the mud water, in the primary precipitation process, in order to ensure that sludge particles are rapidly precipitated under the action of gravity and water flow resistance, according to the free precipitation theory and flow calculation, adopting a bricked semi-underground structure to design three stages of precipitation tanks with the sizes of 20m, 15m, 1m and 15m, 12m, 1m respectively, wherein the height difference of the top of each stage of precipitation tank is controlled between 300 and 500mm, cement mortar with the thickness of 1cm is smeared on the inner surface of each stage of precipitation tank, and a layer of waterproof coiled material is adhered on the inner surface of each stage of precipitation tank. The muddy water firstly flows into a first-stage sedimentation tank through a lifting pump temporarily arranged in the middle to primarily sediment substances with larger particles in the muddy water, the supernatant of the first sedimentation tank overflows to a second-stage sedimentation tank to further sediment fine particles which are not in the reach of the first sedimentation tank, and the last-stage sedimentation tank mainly ensures the integral sedimentation effect of the sludge;

then, pumping the precipitated sludge into an integrated sorting machine for sorting sand, stones and sundries so as to remove granular substances with the diameter larger than 3mm and without dehydration treatment, preventing the granular substances from entering subsequent pipelines and treatment systems to influence dredging effect and avoiding damage to other mechanical equipment;

and finally, performing flocculation precipitation on the precipitated sludge to reduce the contents of heavy metals and toxic and harmful substances in the sludge. In the process, according to the daily dredging amount, a three-level dosing reaction area is designed by adopting a brick semi-underground structure, and the volumes of the three-level dosing reaction area are respectively 200m³、100m³And 100m³The height difference between the tanks is 50-80cm, and the inner surface of each stage of dosing reaction zone is coated with cement mortar with the thickness of 1cm and is adhered with a layer of waterproof coiled material. The medicine is added into each medicine adding reaction area by an automatic medicine feeder with the adding capacity of 3m³And a stirrer is arranged in each stage of reaction area, so that the contact reaction effect of the medicine and muddy water can be improved. The first-stage dosing reaction zone takes ferrous sulfate as a flocculating agent, and the flocculating group of the first-stage dosing reaction zone has large particles, high sedimentation speed, dense sludge, good color removal effect, no toxicity, benefit for the growth of microorganisms and low price; the sludge treated by the first dosing reaction zone automatically flows to the second dosing reaction zone from a conical bottom gate, and the heavy metal is ensured by adding polyaluminium chlorideAnd the removal effect of toxic and harmful substances; finally, the sludge flows into a third dosing reaction zone in which polyacrylamide is added. According to the original detection result and the field test, the adding amounts of the ferrous sulfate, the polyaluminium chloride and the polyacrylamide are respectively 2mg/L, 1.5mg/L and 1 mg/L.

In the dredging project, the distance is 100m³The silt removal amount and the field test parameters are determined by selecting the 3m integrated rated silt discharge amount of 100m³The filter cloth in the belt type concentration and dehydration filter press is used for intercepting, concentrating and filter pressing the concentrated slurry discharged from the dosing reaction tank to prepare a thin cake-shaped sticky substance.

The thin-cake-shaped sticky materials are transferred to a designated airing field by using the loader, and because the dredging amount is large, two storage yard subareas are arranged for airing in order to facilitate the airing and turnover of the sectional dredging amount, and the first field occupies an area of about 6000m²Is arranged nearby a concentration and dehydration filter press, and occupies about 9000m of the second site²The device is arranged near a soil filling point, the distance between two fields is about 500m, and the stacking height is not more than 1 m. When the weather is fine, the mud cakes with larger grain sizes are crushed to be less than or equal to 5cm in the tedding process by using a digging machine and manual combined mode for irregular tedding, and the mud cakes are well covered and waterproof in rainy days. And after the water content of the mud cake reaches the backfilling requirement of 30%, operating and backfilling.

And finally, uniformly treating tail water in the river channel dredging process, building drainage ditches with the bottom width of 0.3m and the depth of 0.3m at positions 1m away from the side of the storage yard and the surfaces sprayed with mortar, and building water collecting wells with the depth of 0.5m by 0.5m at positions every 50m in the drainage ditches, wherein the water collecting wells are arranged at corners as much as possible. Meanwhile, a clean water pond with a semi-underground brick structure and the size of 30m by 1.5m is built behind the third-stage sedimentation pond. The effluent of the dosing reaction area, the filtered water of the concentration filter press and the water seepage of the tedding mud cake all flow into the three-stage sedimentation tank through the drainage channel or the drainage pipeline, the effluent of the sedimentation tank overflows to the clean water tank, the water in the clean water tank is conveyed to the nearby artificial wetland through the built-in lifting pump for advanced treatment, the effluent of the artificial wetland reaches surface water IV and then is used for replenishing old river channels, and the effluent can also be circularly used for water injection stirring and filter belt cleaning.

In order to further research and analyze the river channel dredging method disclosed by the invention, the contents of heavy metals and toxic and harmful substances in the bottom mud can be effectively reduced, and the water content and the contents of the heavy metals and the toxic and harmful components of the thin-cake-shaped sticky substances after concentration and pressure filtration are detected.

In order to improve the accuracy of the detection result, the point distribution principle covers the whole river as completely as possible with a small number of points and accurately detects the pollution condition of the bottom mud, the mesh point distribution method is suitable for river channels with uniform pollution, and if a plurality of industrial or domestic sewage outlets exist around the river channel and the pollution degree of the bottom mud is not uniform, sampling points need to be encrypted near the sewage outlets. Meanwhile, the sampling points are arranged from dense to sparse according to the water flow direction and the sludge accumulation condition, the pollution range and the pollution degree cannot be accurately reflected if the distance is too large, and the detection cost is increased if the distance is too small.

Therefore, in order to verify the dredging effect on the old river channel, 7 sampling sections are arranged at the entrance and exit of the river channel, the direct current section, the bend, the neighborhood of the village and the sewage discharge outlet respectively, 14 samples are collected, and a national authoritative third-party detection institution is entrusted to carry out detection and analysis by using a national standard method, wherein the standard detection method is shown in table 1, and the detection result is shown in table 2.

TABLE 1 Standard assays

In order to evaluate the treatment effect of the method on the bottom mud, the following method is adopted for analysis:

1) single term pollution index method

Measured values C of each evaluation parameter_iDivided by the corresponding standard value S_iObtaining the pollution index I of the evaluation parameter_i：

I_i＝C_i/S_i

In the formula: c_i-measured concentration of i-th contaminant in the bottom mud, mg/L;

S_i-standard value, natural content or environmental background value, mg/L, of the ith pollutant in the river soil.

When I is_i>1, indicates that the concentration thereof exceeds the evaluation standard value.

2) Internal Mello pollution index method

And after the pollution indexes of the evaluation factors are calculated, calculating the inner Meiro pollution indexes of all layers of the bottom mud according to the following formula. The formula is as follows:

in the formula: p_Heald-the overall pollution index of heavy metals;

I_maxcontamination index of the respective factor I_iMaximum value of (d);

I_av-average value of the contamination index of each factor.

And according to the calculated comprehensive pollution index and the classification standard in the following table, evaluating the current situation of the bottom sludge pollution.

The evaluation shows that the P is 0.2 < 0.7, so that the pollution degree of the bottom mud of the river channel is reduced to be clean and safe after treatment.

And the water content of the concentrated filter-pressed sample is taken along 8 sections of the river, the treated mud sample is detected to have the water content of 48.2 +/-2.5 percent after dehydration, and the color of the sample is black brown and viscous. The water content of the mud cakes after being tedded is less than 30 percent and is 25.3 +/-3.4 percent, and the mud cakes are dark brown and moist and meet the backfill requirement.

In conclusion, the silt of about 13 ten thousand meters can be cleaned by using the dredging method to clean the river channel³The cleaning length is about 3.5km, the construction period is about 3 months, and the comprehensive unit price is about 180 yuan/m³Good economical efficiency and high practicability. And the water content of the treated bottom mud is lower than 30%, the contents of heavy metals and toxic and harmful substances of the treated bottom mud reach IV grade of technical Specification for treating effluents of river and lake sludge treatment factories (SZDB/Z236-2017), and the backfilling requirement is met.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A river channel dredging method is characterized by comprising the following steps:

2. The dredging method according to claim 1, wherein in step S1, when the cofferdam is divided, the temporary cofferdam is used to divide the river into multiple sections according to the plan view and the cross-sectional view of the river, and intermediate pumping stations are arranged between the multiple sections.

3. The dredging method according to claim 2, wherein in the step S1, during the segmental dredging, firstly, the reamer head is used for cutting bottom mud, the river water is taken and stirred by being assisted by water jetting of a high-pressure water gun, and finally, the muddy water on the bottom layer is cleaned out of the river channel in a manner of cutter suction pumping.

4. The dredging method according to claim 3, wherein in the step S2, in the preliminary sedimentation, the cleaned mud water passes through the sedimentation tanks with height difference at the tops of the multiple stages in sequence to realize the preliminary separation of the mud water.

5. The method according to claim 4, wherein in the step S2, the sludge obtained by the preliminary sedimentation is sorted to remove particulate matter with a diameter larger than 3 mm.

6. The dredging method according to claim 5, wherein in the step S2, during the flocculation, ferrous sulfate, polyaluminium chloride and polyacrylamide are sequentially added into the sorted muddy water.

7. The dredging method according to claim 6, wherein in the step S3, the dewatered sludge is subjected to trapping, thickening and pressure filtering by using a sludge solidification technique to obtain a wafer-like sticky substance.

8. The dredging method according to claim 7, wherein in step S3, the pancake-shaped sticky matter is aired and crushed until the grain size is less than or equal to 5cm during the tedding, and the backfilling is performed after the water content reaches the backfilling requirement.

9. The dredging method according to claim 8, further comprising tail water treatment, specifically comprising: and sequentially passing the flocculating and settling effluent, the filter-pressing effluent and the tedding seepage water through the multistage sedimentation tank, and carrying out microbial treatment on clear water overflowing from the sedimentation tank.