In-situ dewatering and consolidation method for river and lake dredged sludge under low temperature condition

Abstract

The application discloses a kind of low-temperature conditions under river and lake dredging bottom mud in-situ drainage consolidation method, comprising the following steps: step 1: two dykes are set in dredging riverway;Step 2: several layers of transverse drainage components are laid in the process of hydraulic filling bottom mud;Step 3: when the elevation of hydraulic filling reaches the height of the dyke top, the transverse drainage components are connected to a vacuum pump;Step 4: a sealed environment is established by covering a sealing membrane, and a stepwise preloading drainage is adopted;Step 5: the construction area is depressurized, the sealing membrane is removed, and the dried and contaminated bottom mud in the two dykes is dry-excavated and transported out. The dykes are removed, and the dredging and drying of the riverway is finally completed. The application improves the consolidation rate of the soil through freeze-thaw cycles of dredged sediment, expands the application scenarios of dredged sediment dewatering and drying, and enables the process to be constructed below zero degrees Celsius in winter.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of river and lake dredged sediment dewatering and drying, and particularly relates to a method for in-situ drainage and consolidation of river and lake dredged sediment under low-temperature conditions. BACKGROUND

[0002] The river and lake dredged sediment has the characteristics of high water content, large compressibility, low shear strength, poor permeability and basically no bearing capacity, so before engineering construction or resource utilization, it needs to be dewatered and dried to make the dredged sediment quickly solidified. The vacuum preloading method has the advantages of low cost, simple construction and no pollution, and is the most traditional and most widely used method. The traditional vacuum preloading method is to set plastic drainage boards in the deep soil body, and water in the sludge is quickly removed by applying vacuum negative pressure to the drainage boards, so as to realize the rapid consolidation of the pretreated soil layer and achieve the purpose of dewatering and drying.

[0003] Most of the eastern regions of China are short-time frozen soil (a few hours / days to half a month) or seasonal frozen soil (half a month to several months); frozen soil refers to various rock-soil and soil containing ice below 0℃. Rock-soil and soil without ice below 0℃ are called cold soil or cold soil. Under low-temperature conditions, i.e. when the environmental temperature is below 0℃, the water in the dredged sediment freezes, and the flowability of the contained water decreases, making it difficult to use the traditional vacuum preloading construction for dewatering and drying.

[0004] However, the present inventors have found that the above prior art at least has the following technical problems:

[0005] 1. At present, the thickness of the river and lake dredged sediment is less than ten meters, and the length of the drainage board is generally not higher than ten meters, which belongs to shallow vacuum preloading construction. An important process is to vertically set the drainage board on the surface of the river and lake dredged sediment. This operation process consumes a lot of time and affects the progress of the project. Moreover, the bearing capacity of the surface of the dredged sediment is low, and the mechanical equipment is difficult to travel. At present, the construction method of laying bamboo grating on the surface of the dredged sediment and manually inserting the board is generally used, which has great safety risks.

[0006] 2. The vacuum preloading treatment in the land storage pool has a long construction period. The dredged sediment needs to be piled in the storage pool first, and then the drainage board is set, the sealing film is overlaid, and the air is extracted. The construction period is generally 4-6 months, which is difficult to meet the demand of many projects for the construction period.

[0007] 3. Conventional vacuum preloading dewatering of dredged sediment can only be carried out at ambient temperatures above 0℃. This is due to two reasons: First, the water in the drainage pipeline must be liquid. When the ambient temperature is below 0℃, the water in the pipeline will freeze, blocking the pumping (air) pipeline. Simultaneously, the dredged sediment will experience frost heave, increasing in volume and damaging equipment embedded in the soil. Second, when the ambient temperature is below -20℃, the dredged sediment will solidify into frozen soil, with a sharp increase in shear strength and a significant decrease in permeability, making pumping (air) operations difficult. These factors limit the construction environment conditions for dredged sediment dewatering and drying, restricting its application scenarios and making it difficult to meet the time requirements of some projects.

[0008] Therefore, based on these issues, a method for in-situ drainage and consolidation of river and lake dredged sediment under low-temperature conditions is proposed. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides an in-situ drainage and consolidation method for dredged sediment in rivers and lakes under low-temperature conditions, which significantly improves drainage efficiency, reduces multiple construction procedures, and greatly enhances the drying treatment efficiency of dredged sediment.

[0010] This invention is implemented as follows: a method for in-situ drainage and consolidation of dredged sediment in rivers and lakes under low-temperature conditions, characterized by the following steps:

[0011] Step 1: Two dikes are set up in the dredged river channel to drain the water from the two dikes and to transport the polluted bottom sludge dredged from the river channel into the sludge storage pool formed between the two dikes by hydraulic conveying.

[0012] Step 2: During the backfilling process, several layers of transverse drainage components are laid. Each transverse drainage component includes a drainage pipe and geotextile wrapped around the drainage pipe. The drainage pipe is composed of several individual drainage pipes spliced ​​together sequentially, and each individual drainage pipe has a water passage hole. The drainage pipes of the above drainage components are all connected to a water supply pipeline through drainage risers. The water supply pipeline is connected to a vacuum pump through a water vapor separator. Each layer of transverse drainage components is wrapped with a self-regulating electric heating tape.

[0013] Step 3: When the filling elevation reaches the top height of the dike, stop filling and connect both ends of the drainage pipe to the delivery pipeline. Connect the delivery pipeline to the vacuum pump and water vapor separator. Specifically, connect every three drainage hoses to a four-way fitting, and connect the remaining hole of the fitting to the vacuum pump through the water delivery pipeline.

[0014] Step 4: Cover with a sealing membrane. After the sealing membrane is applied, the vacuum pump starts to extract air. During the extraction process, the tailwater and tail gas are treated to ensure the safety and environmental protection of the construction process. In order to generate multiple freeze-thaw cycles in the dredged sediment, the following three steps are taken:

[0015] Step 4.1): pre-pressurization stage, gradually pressurized to 40-60 kPa, so that the dredged soil body is initially attached to the PVC pipe, and the process lasts for 72 h;

[0016] Step 4.2): continuous pressurization stage, pressurized to 80 kPa, and heated for 24 h under the pressurized condition;

[0017] Step 4.3): temperature control stage, keep the vacuum pressure at 80 kPa, and cyclically heat according to the change of the ambient temperature under the pressurized condition, so that the soil body generates freeze-thaw cycles. Specifically, divide the 24-hour period into four time periods, namely, time period A, time period B, time period C, and time period D. Please refer to Figure 6 ;

[0018] Time period A: 00:00-06:00, the soil body temperature slowly decreases under the influence of the ambient temperature, and the heating zone does not increase the temperature;

[0019] Time period B: 06:00-12:00, the soil body temperature starts to rise under the influence of light, and the heating zone starts to heat and increase the temperature, so as to increase the temperature rising speed of the soil body and maintain the soil body temperature at a high level;

[0020] Time period C: 12:00-18:00, the heating zone keeps the soil body temperature at the preset temperature; keep the dried soil body at a high constant temperature, stop heating when the dried soil body exceeds the preset temperature of the temperature sensor arranged in the soil body, and start heating when the dried soil body is lower than the preset temperature, so as to keep the soil body at a constant temperature for 6 hours;

[0021] Time period D: 18:00-24:00, stop the heating zone from increasing the temperature, and the soil body temperature slowly falls under the influence of the ambient temperature;

[0022] In this process, the freeze-thaw cycle period of the dredged soil is 24 h, the heating cycle frequency of the self-limiting temperature electric heating zone is synchronized with the ambient temperature change frequency, and is consistent with the daily temperature change. The beneficial aspect of this setting is that the ambient temperature rise is synchronized with the heating of the heating zone during the soil body heating process, so as to achieve the purpose of energy saving;

[0023] Step 5: depressurize in the construction area, remove the sealing film, dry dig and transport the dried contaminated sediment in the two dikes, remove the dikes, and finally complete the dredging and drying treatment work of the river channel.

[0024] Further preferably, in the single-layer transverse drainage assembly, the self-limiting temperature electric heating zone is wound on the drainage pipe of the drainage assembly at intervals.

[0025] Further preferably, in the single-layer transverse drainage assembly, the self-limiting temperature electric heating zone is wound on the drainage pipe of the drainage assembly at intervals.

[0026] Further preferably, the interval height of adjacent transverse drainage assemblies is 1.5 m, and the interval distance of adjacent transverse drainage assemblies is 1.2 m.

[0027] Further preferably, the geotextile is in a cylindrical structure.

[0028] Further preferably, a temperature sensor for detecting the temperature of the soil is embedded in the bottom mud between the two dikes.

[0029] Further preferably, the drainage pipes of each layer of transverse drainage assemblies are connected to water supply pipelines at both ends, and three drainage hoses on one side are connected to a drainage riser through a four-way pipe fitting.

[0030] Further preferably, both ends of the drainage riser are connected to a vacuum pump through a water supply pipeline.

[0031] Further preferably, the winding form of the self-limiting temperature electric heat tracing tape wound on the drainage pipe is spiral winding.

[0032] Further preferably, the spiral spacing of the self-limiting temperature electric heat tracing tape is 0.2 m.

[0033] The present application has the advantages and technical effects that the present application has the following advantages by adopting the above technical scheme:

[0034] 1. The present application solves the problem of difficult dehydration and drying construction when the environmental temperature is below 0℃, expands the application scenario of dredged mud dehydration and drying, and can be used for construction in winter.

[0035] 2. Through the freeze-thaw cycle of dredged mud, the consolidation rate of the soil is improved, and the application scenario of dredged mud dehydration and drying is expanded, so that the process can be used for construction below 0℃ in winter.

[0036] 3. In the process of dredged mud reclamation, drainage boards are simultaneously embedded, and after reclamation is completed, the drainage board is set up, reducing the construction steps of setting up vertical drainage boards, greatly shortening the dredged mud treatment period, improving the construction efficiency, reducing the transportation cost of dredged soil off-site treatment, and enhancing the dehydration and consolidation effect of deep soil.

[0037] 4. The transverse drainage assembly used in the present application contains a hard rough pipe, and the drainage and gas cross section is larger than that of the traditional drainage board, which is more conducive to keeping the drainage and gas passage unobstructed and reducing the phenomenon of drainage board deformation and pipe blockage.

[0038] 5. The method used in the present application is to treat the bottom mud in the river, which is equivalent to in-situ treatment of silt, reducing the transportation distance of the contaminated bottom mud, and reducing the transportation energy consumption.

[0039] 6. This invention allows for the installation of air extraction devices at any location on both sides of the river, enabling flexible site layout that meets the safety and environmental protection requirements of busy urban areas.

[0040] 7. This invention can extract air at both ends of the horizontal drainage plate, improving the vacuum conduction efficiency and thus enhancing the consolidation effect. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of the present invention;

[0042] Figure 2 This is a schematic diagram of the self-regulating electric heating cable winding structure;

[0043] Figure 3 This is a schematic diagram of a three-dimensional structure with part of the geotextile removed;

[0044] Figure 4 This is a schematic diagram of a self-regulating electric heating cable structure;

[0045] Figure 5 This is a schematic diagram of the cross-sectional structure of the present invention;

[0046] Figure 6 It is a soil temperature control curve.

[0047] In the diagram: 1. Dike; 2. Sealing membrane; 3. Lateral drainage assembly; 3-1. Drainage pipe; 3-10. Water passage hole; 3-2. Geotextile; 3-3. Water supply pipeline; 3-4. Water vapor separator; 3-5. Vacuum pump; 3-6. Self-regulating heating cable; 3-60. Tinned soft copper wire; 3-61. "PTC" conductive plastic layer; 3-62. Polyolefin insulation layer; 3-63. Metal shielding layer; 3-64. Polyolefin insulation layer; 3-7. Four-way fitting. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0049] Please see Figures 1 to 5 Example:

[0050] In practice, at a dredging sediment drying treatment project in Jiangsu Province, where there is no sludge dumping site nearby, and taking an ambient temperature of -8℃ as an example, the dredging sediment in the river channel is treated using a low-temperature in-situ drainage consolidation method for river and lake dredging sediment disclosed in this invention. This involves multiple freeze-thaw cycles and air extraction, achieved through the following steps:

[0051] Step 1: two dikes are arranged in the dredged river channel, the water in the two dikes is discharged, and the dredged contaminated sediment in the river channel is input into the storage pool formed between the two dikes by hydraulic transportation; the sediment treatment site is located in the river channel, which is equivalent to in-situ treatment of silt, reducing the transportation distance of hydraulic transportation of contaminated sediment and reducing the transportation energy consumption;

[0052] Step 2: several layers of transverse drainage assemblies 3 are laid during the process of filling the dredged sediment, the transverse drainage assembly includes a drainage pipe 3-1 and a geotextile 3-2 wrapped on the drainage pipe, the drainage pipe is sequentially spliced by several drainage pipe monomers, and each drainage pipe monomer is provided with a water passing hole 3-10; the drainage pipe of the above-mentioned drainage assembly is connected to a water delivery pipeline 3-3 through a drainage vertical pipe, the water delivery pipeline is connected to a vacuum pump 3-5 through a water vapor separation device 3-4, and in the actual vacuum preloading, the negative pressure generated by the vacuum pump is conducted to the drainage pipe through the vapor-liquid delivery pipeline, the negative pressure is generated in the soil body by the drainage pipe and the geotextile, and the water in the soil body is transferred under the action of the negative pressure, and is collected near the geotextile inside the soil body, the water body enters the drainage pipe through the geotextile 2, and is pumped out of the soil body by the vacuum pump, so that the effect of soil drainage and consolidation is achieved, and each layer of transverse drainage assembly is wound with a self-limiting temperature electric heat tracing tape 3-6; during production, the drainage pipe is inserted into the geotextile which is sewn in advance, and is connected to a suitable length at the head and tail according to the width of the river channel, and the drainage pipe is laid during the process of filling in the river channel, and is laid simultaneously during the process of rising of the filling elevation; specifically, one layer of drainage pipe is laid every 1.5 m of rising of the filling elevation, and the transverse spacing of the drainage pipe is 1.2 m;

[0053] Step 3: when the filling elevation reaches the height of the dike top, stop filling, connect the two ends of the drainage pipe to the delivery pipeline respectively, and connect the delivery pipeline to the vacuum pump and the water vapor separation device; specifically, one four-way pipe is connected to every three drainage hoses, and the remaining one hole of the pipe is connected to the vacuum pump through the water delivery pipeline;

[0054] Step 4: cover the sealing film to establish a vacuum sealed environment, start the vacuum pump after covering the sealing film, treat the tail water and tail gas during the air pumping process, and ensure the safety and environmental protection during construction; in this process, in order to make the dredged sediment undergo multiple freeze-thaw cycles, the following three steps are taken:

[0055] Step 4.1): pre-pressurization stage, gradually pressurize to 40 ～ 60kPa, so that the dredged soil body is preliminarily attached to the PVC pipe, and the process lasts for 72h;

[0056] Step 4.2): continuous pressurization stage, pressurize to 80kPa, and continuously heat for 24h under the pressurization condition;

[0057] Step 4.3): temperature control phase, keep the vacuum pressure 80kPa, cycle heating under the condition of pressure increase according to the ambient temperature changes, so that the soil body produces freeze-thaw cycle, specifically, 24 hours a day is divided into four periods, respectively: period A, period B, period C, period D; please refer to Figure 6 ;

[0058] Period A: 00:00-06:00, the soil temperature slowly decreases under the influence of ambient temperature, and the heating zone does not increase temperature;

[0059] Period B: 06:00-12:00, the soil temperature begins to rise under the influence of light, and the heating zone begins to heat and increase the temperature, so as to increase the temperature rising speed of the soil and maintain the soil temperature at a high level;

[0060] Period C: 12:00-18:00, the heating zone keeps the soil temperature at a preset temperature; the dry soil is kept at a high constant temperature, when the dry soil exceeds the preset temperature of the temperature sensor arranged in the soil, the heating is stopped, and when the dry soil is lower than the preset temperature, the heating is started, so as to keep the soil at a constant temperature, and the duration is 6 hours;

[0061] Period D: 18:00-24:00, stop the heating zone to increase the temperature, and the soil temperature slowly falls under the influence of ambient temperature;

[0062] In this process, the dredged soil freeze-thaw cycle period is 24h, the temperature limiting electric heating zone increases the temperature, and the temperature increase cycle frequency is synchronous with the ambient temperature change frequency, which is consistent with the daily temperature change. The beneficial aspect of this setting is that the ambient temperature rise is synchronous with the heating zone temperature rise during the soil temperature increase process, so as to achieve the purpose of energy saving;

[0063] Step 5: pressure relief in the construction area, remove the sealing film, dry dig the dry contaminated sediment in the two dikes, remove the dikes, and finally complete the dredging and drying treatment of the river.

[0064] The traditional vacuum preloading drying method needs more than 120 days of construction period, and cannot be constructed under the condition that the temperature is below 0℃ all day in winter. Under the condition that the temperature is above 0℃ in the daytime and below 0℃ at night, the drying period is also greatly prolonged, and the final drying and consolidation effect is also affected. The drying method only needs 60-90 days of construction period, and is not affected by the temperature, and the dredged sediment can be frozen and thawed under low temperature, so that the drying and consolidation effect is improved.

[0065] In order to further improve the drainage and consolidation effect, the present application can also adopt the following technical scheme:

[0066] Further preferably, in the single-layer transverse drainage assembly, the self-temperature-limiting electric heating zone is wound on the drainage pipe of the drainage assembly.

[0067] Further preferably, the self-limiting temperature electric heating tape is wound in the single-layer transverse drainage assembly with 1-2 drainage pipes as interval.

[0068] Further preferably, the interval height of adjacent transverse drainage assemblies is 1.5 m, and the interval distance of adjacent transverse drainage assemblies is 1.2 m.

[0069] The application solves the problem that the dewatering and drying construction is difficult to be carried out when the environmental temperature is lower than 0℃, expands the application scene of the dredged sediment dewatering and drying, and the construction can be carried out in winter by using the process, and the self-limiting temperature electric heating tape is wound on the drainage pipe.

[0070] The drainage pipe is transversely wound with the self-limiting temperature electric heating tape with 1-2 as interval, and the PVC pipe wound with the self-limiting temperature electric heating tape is arranged at each depth in the vertical direction.

[0071] The self-limiting temperature electric heating tape comprises a 3-60 tin-plated soft copper wire, a 3-61 PTC conductive plastic layer, a 3-62 polyolefin insulation layer and a 3-63 metal shielding layer.

[0072] The self-limiting temperature electric heating tape is also called self-controlled temperature electric heating tape, is a strip-shaped constant temperature electric heating product, is composed of high molecular conductive carbon particles and two parallel busbars plus an insulation layer, and the resistivity of the PTC heating element has a very high positive temperature coefficient and is mutually connected in parallel.

[0073] The self-limiting temperature electric heating tape is wound outside the PVC pipe, and the purpose of the arrangement is to increase the temperature and improve the temperature of the surrounding soil through the self-limiting temperature electric heating tape.

[0074] The self-limiting temperature electric heating tape is made of flexible material and has waterproof performance, and the arrangement is beneficial to winding outside the hard PVC and burying in the saturated soil.

[0075] The self-limiting temperature electric heating tape can be connected end to end to lengthen, or can be cut from the middle to meet the temperature increasing demand of PVC pipes of different lengths.

[0076] The beneficial aspect of the freezing and thawing cycle of the soil in the vacuum preloading air extraction stage is based on the conclusion obtained through relevant tests: the dredged sediment with high water content can increase the void ratio and permeability of the soil under the action of freezing and thawing cycle. Especially, the higher the initial water content of the dredged sediment, the more severe the structure damage of the soil sample under the repeated freezing and thawing cycle, the greater the change rate of the void ratio and permeability coefficient, the longer the freezing and thawing cycle damage lasts, and there is a weak frost shrinkage compaction in the repeated freezing and thawing cycle process.

[0077] When the environment rises, the self-limiting temperature electric heating tape starts to heat; when the environment temperature drops, the self-limiting temperature electric heating tape stops heating, with a 24-hour cycle, so that the dredged sediment produces freeze-thaw cycles.

[0078] Further preferably, both ends of the vertical drainage pipe are connected to the water conveying pipeline through the water conveying pipeline.

[0079] Further preferably, the self-limiting temperature electric heating tape is spirally wound on the drainage pipe.

[0080] Further preferably, the spiral spacing of the self-limiting temperature electric heating tape is 0.2 m.

[0081] Preferably, the geotextile is a cylindrical structure. In actual production, the two long edges of the geotextile are combined together by sewing to form a hollow cylindrical structure with two open sides. The purpose of this arrangement is to allow the drainage pipe to pass through the geotextile and support the inside of the geotextile as a hollow structure. After inserting the drainage pipe, the two ends of the geotextile are tied with a rope. The purpose of this arrangement is to prevent water leakage and air leakage between the drainage pipe and the geotextile.

[0082] Preferably, a temperature sensor for detecting the temperature of the soil is embedded in the sediment between the two dikes. The temperature sensor is electrically connected to a display or a controller. The temperature in the soil can be observed in real time through the display, and the heating power of the self-limiting temperature electric heating tape or the opening and closing of the self-limiting temperature electric heating tape can be controlled through the controller. The main use of the freeze-thaw cycle control is the temperature control sensor embedded in the soil. The temperature limit value is preset, and the heating power of the self-limiting temperature electric heating tape is adjusted according to the change of the environment temperature, so that the dredged sediment as a whole produces freeze-thaw cycles with a 24-hour cycle, and the dredged sediment is dehydrated and dried under the freeze-thaw cycles.

[0083] Preferably, further preferably, the drainage pipes at both ends of each layer of transverse drainage assembly are connected to the water conveying pipeline, and three drainage hoses on one side are connected to a drainage vertical pipe through a four-way pipe fitting 3-7.

[0084] Preferably, the two ends of the drainage pipe are connected to the water conveying pipeline through the water conveying pipeline, and the two ends are drained simultaneously to improve the drainage efficiency.

[0085] Further preferably, the self-limiting temperature electric heating tape is spirally wound on the drainage pipe to ensure uniform heating from top to bottom.

[0086] Further preferably, the spiral spacing of the self-limiting temperature electric heating tape is 0.2 m.

[0087] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for in-situ dewatering and consolidation of dredged river and lake sediment under low temperature conditions, characterized in that: It comprises the following steps: Step 1: two dikes are arranged in the dredged river channel, the water in the two dikes is discharged, and the dredged contaminated bottom mud in the river channel is input into the mud storage pool formed between the two dikes by hydraulic conveying; Step 2: several layers of transverse drainage assemblies are laid during the process of filling the bottom mud, the transverse drainage assembly comprises a drainage pipe and a geotextile wrapped on the drainage pipe, the drainage pipe is sequentially spliced by several drainage pipe monomers, and each drainage pipe monomer is provided with a water passing hole; the drainage pipe of the above-mentioned drainage assembly is connected with a water delivery pipeline through a drainage vertical pipe, the water delivery pipeline is connected with a vacuum pump through a water vapor separation device; each layer of transverse drainage assembly is wound with a self-limiting temperature electric heat tracing band; a temperature sensor for detecting the temperature of the soil body is pre-buried in the bottom mud between the two dikes; Step 3: when the filling elevation reaches the height of the dike top, stop filling, connect the two ends of the drainage pipe with the delivery pipeline respectively, and the delivery pipeline is docked with the vacuum pump and the water vapor separation device; Step 4: cover the sealing film, the vacuum pump starts to pump after the sealing film is covered, the tail water and tail gas are treated during the pumping process to ensure the safety and environmental protection of the construction process, and the following three steps are taken to make the dredged bottom mud undergo multiple freeze-thaw cycles during the process: Step 4.1): pre-pressurization stage, gradually pressurize to 40-60kPa, so that the dredged soil body preliminarily adheres to the PVC pipe, and the process lasts for 72h; Step 4.2): continuous pressurization stage, pressurize to 80kPa, and continuously heat for 24h under the pressurized condition; Step 4.3): temperature control stage, maintain the vacuum pressure at 80kPa, and cyclically heat according to the environmental temperature change under the pressurized condition to make the soil body undergo freeze-thaw cycles, specifically, divide each 24h into four time periods, which are time period A, time period B, time period C and time period D; Time period A: 00:00-06:00, the temperature of the soil body slowly decreases under the influence of the environmental temperature, and the heat tracing band does not increase the temperature; Time period B: 06:00-12:00, the soil body starts to rise in temperature under the influence of light, and at the same time, the heat tracing band starts to heat and increase the temperature, so as to improve the temperature rising speed of the soil body and maintain the temperature of the soil body at a high level; Time period C: 12:00-18:00, the heat tracing band keeps the temperature of the soil body at a preset temperature; the dried soil body is kept at a high constant temperature, and when the dried soil body exceeds the preset temperature of the temperature sensor arranged in the soil body, the heating is stopped, and when the dried soil body is lower than the preset temperature, the heating is started, so that the soil body is kept at a constant temperature, and the duration is 6 hours; Time period D: 18:00-24:00, stop the temperature increase of the heat tracing band, and the temperature of the soil body slowly falls under the influence of the environmental temperature; In this process, 24h is taken as the freeze-thaw cycle period of the dredged soil, the temperature increase cycle frequency of the self-limiting temperature electric heat tracing band is synchronous with the environmental temperature change frequency, and is consistent with the daily temperature change, which is beneficial in that the environmental temperature rise is synchronous with the temperature increase of the heat tracing band during the temperature increase process of the soil body, so as to achieve the purpose of energy saving; Step 5: depressurize in the construction area, remove the sealing film, dry dig and transport the dried contaminated bottom mud in the two dikes, remove the dikes, and finally complete the dredging and drying treatment of the river channel.

2. The method for dewatering and consolidating in-situ dredged river and lake sediment under cryogenic conditions according to claim 1, characterized in that: In the single-layer transverse drainage assembly, the self-limiting temperature electric heating tape is wound on the drainage pipe of the drainage assembly at intervals.

3. The method for dewatering and consolidating in-situ dredged river and lake sediment under cryogenic conditions according to claim 1, characterized in that: In the single-layer transverse drainage assembly, the self-limiting temperature electric heating tape is wound on the drainage pipe of the drainage assembly at intervals.

4. The method for dewatering and consolidating in-situ dredged river and lake sediment under cryogenic conditions according to claim 1, characterized in that: The interval height between adjacent transverse drainage assemblies is 1.5 m, and the interval distance between adjacent transverse drainage assemblies is 1.2 m.

5. The method for dewatering and consolidating in-situ dredged river and lake sediment under cryogenic conditions according to claim 1, characterized in that: The geotextile is in a cylindrical structure.

6. The method for dewatering and consolidating in-situ dredged river and lake sediment under cryogenic conditions according to claim 1, characterized in that: The two ends of the drainage pipe of each layer of transverse drainage assembly are connected with water conveying pipelines, and three drainage hoses on one side are connected with a drainage vertical pipe through a four-way pipe fitting.

7. The method for dewatering and consolidating in-situ dredged river and lake sediment under cryogenic conditions according to claim 6, characterized in that: The two ends of the drainage vertical pipe are connected with vacuum pumps through water conveying pipelines.

8. The method for dewatering and consolidating dredged river and lake sediment in-situ under cryogenic conditions according to claim 1, characterized in that: The winding form of the self-limiting temperature electric heating tape wound on the drainage pipe is spiral winding.

9. The method for dewatering and consolidating in-situ dredged river and lake sediment under cryogenic conditions according to claim 8, characterized in that: The winding spiral pitch of the self-limiting temperature electric heating tape is 0.2 m.

Images