Method for dewatering and drying river and lake dredged sludge

Abstract

The application discloses a kind of river and lake dredging sludge dewatering and drying method, the method is by constructing sludge disposal site to carry out solidification drainage, comprising: S1, constructing sludge disposal site with at least two dewatering and drying zones;S2, sludge water is sent to dewatering and drying zone from the import of dewatering and drying zone, sludge water is separated and clear water is generated in dewatering and drying zone, and clear water flows out from the water outlet of dewatering and drying zone;S3, the seepage water in the bottom mud layer is pumped out by using water pump group.The application increases the free settling time when dewatering and drying, ensures the clarification effect of sludge water reaching the water outlet, and improves the dewatering efficiency of clear water.In addition, by using the water pump to pump out the pore water in the silt during the consolidation process of the drainage pipe and the drainage ditch, the discharge of silt pore water is accelerated, and the dewatering and drying of the bottom mud is further accelerated.The sludge disposal site constructed by the application has two or more dewatering and drying zones, and the dewatering and drying zones can be converted, which further improves the dewatering and drying efficiency of the bottom mud.

Description

Technical Field

[0001] This invention relates to the field of lake silt treatment, and in particular to a method for dewatering and drying river and lake dredged sediment. Background Technology

[0002] Eutrophication is one of the main factors causing water pollution in my country's rivers and lakes. The primary cause is the continuous and excessive input of nutrients such as nitrogen, phosphorus, and organic matter. Polluted lake sediment, primarily composed of organic matter, also contains a large amount of harmful substances such as pathogens, viruses, and parasites (eggs). If not effectively treated, it can easily cause secondary pollution. Furthermore, dredged sediment is a natural resource with certain resource attributes; abandoning it without utilization is neither environmentally friendly nor economical.

[0003] Currently, the main methods for treating endogenous pollution in rivers and lakes fall into three categories: physical, chemical, and biological. Environmental dredging, as a physical treatment method, is widely used in endogenous pollution control technologies due to its advantages such as shallow dredging depth, minimal disturbance to bottom sediment, and low secondary pollution. Sludge dumps are sites for dewatering and drying dredged sediment. Existing dewatering and consolidation methods for sludge dumps mainly include natural dewatering, vacuum pre-compression dewatering, and dewatering with added solidifying agents. Among these, natural dewatering has a long dewatering time, requires a long period of land acquisition for sludge dumps, has a high sand content at the discharge point, is greatly affected by weather, and is prone to secondary pollution; therefore, it is rarely used in actual projects. The alkaline solidifying agents used in the dewatering method with added solidifying agents may alter the properties of the soil.

[0004] Vacuum pre-compression dewatering utilizes vacuum extraction to remove pore water from sludge, offering a slight improvement in drying efficiency compared to natural dewatering, and is one of the most commonly used environmentally friendly dredging methods. However, in practical applications, vacuum extraction can lead to clogging and has high operating costs. For example, CN2172313777U discloses an accelerated consolidation sludge discharge site that uses vacuum extraction to discharge pore water through a filter pipe network. While this method accelerates pore water discharge to some extent, clogging can occur if sediment particles enter the filter pipe network, affecting pumping efficiency. Furthermore, this drainage method still suffers from drawbacks such as high sand content at the discharge outlet, long drying time, long operating time, and large land area required.

[0005] In summary, while minimizing the land area occupied by the sludge discharge site, extending the settling and separation time of mud and water within the sludge discharge site and shortening the discharge rate of open water and pore water are crucial to improving the drying efficiency of the sludge discharge site. Summary of the Invention

[0006] In view of this, the present invention aims to provide a method for dewatering and drying bottom sediment from river and lake dredging. This method ensures the settling effect of mud and water by constructing a mud discharge field that can prolong the settling time of mud and water, reduces the sand content at the discharge outlet, and improves the discharge efficiency of pore water, thereby improving the drying efficiency of bottom sediment.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The present invention describes a method for dewatering and drying river and lake dredged sediment, wherein the dewatering and drying method involves solidifying and draining sediment by constructing a sludge discharge site, and includes the following steps:

[0009] S1, construct a sludge discharge site with at least two dewatering and drying zones;

[0010] S2, the mud and water are pumped from the inlet of the dewatering and drying zone to the dewatering and drying zone. The mud and water settle and separate in the dewatering and drying zone and produce clear water. The clear water flows out through the outlet of the dewatering and drying zone.

[0011] S3, use a water pump set to extract the seepage water from the bottom mud layer;

[0012] The sludge discharge site with at least two dewatering and drying zones described in S1 includes the following:

[0013] S11, clear the top layer of soil, and excavate the first and second drainage ditches at the designed location. There are multiple first and second drainage ditches, and they are interwoven.

[0014] S12, construct a cofferdam and a partition dike using the topsoil and the excavated soil. The partition dike is parallel to the short side of the cofferdam and the cofferdam is divided into at least two dehydration and drying zones using the partition dike.

[0015] When constructing the cofferdam, a drainage unit is built at the drainage outlet of each dewatering and drying zone;

[0016] S13, construct at least two guide channels in each dewatering and drying zone, with one end of each guide channel forming a guide opening 2-3m away from the cofferdam, and the guide openings are arranged diagonally to make the mud and water flow in an S-shape.

[0017] During the construction of the diversion channel, a partition board is laid above the second drainage ditch;

[0018] S14, Lay a main drainage pipe in the first drainage ditch and a branch drainage pipe in the second drainage ditch, and seal the ends of the branch drainage pipes; Install permeable perforated pipes on the main drainage pipe and the branch drainage pipes using connectors.

[0019] S15, in the first and second drainage ditches, permeable gravel and reverse-seepage medium-coarse sand are laid sequentially from the inside to the outside to fix the drainage main pipe and drainage branch pipe.

[0020] In the above scheme, the diversion outlets in each dewatering and drying zone are arranged diagonally, and the mud-water inlet and outlet of the dewatering and drying zone are also arranged diagonally. The mud-water moves in an S-shaped curve towards the outlet unit in the drying zone, which prolongs the flow path of the mud-water and increases the free settling time of the sludge in the discharge field. This not only ensures the clarification effect of the mud-water reaching the outlet and reduces the loss of silt, but also improves the discharge efficiency of open water.

[0021] This invention involves excavating crisscrossing drainage ditches and pre-burying crisscrossing drainage pipes within the cofferdam. A water pump unit can be used to quickly discharge pore water in the pipes and seepage water that has seeped into the drainage ditches, thereby accelerating the discharge of pore water from the silt and further speeding up the dehydration and drying of the bottom mud. In addition, this invention lays a layer of medium-coarse sand with reverse osmosis in the drainage ditches, which can effectively prevent reverse osmosis and ensure the drying effect.

[0022] The sludge discharge site constructed by this invention has at least two dewatering and drying zones. Each dewatering and drying zone has an inlet (i.e., a mud-water inlet) and an outlet. The dewatering and drying zones can be switched or operated simultaneously. Depending on the actual situation, the outlet unit can be closed and the site can be switched to another drying zone for sludge discharge (or they can operate simultaneously). This maximizes drying efficiency, shortens drying time, and enables the sludge discharge site to dry quickly, thereby minimizing the time the sludge discharge site occupies. In addition, compared with an undivided sludge discharge site, this invention further improves drying efficiency by dividing the constructed sludge discharge site into zones, while ensuring mud-water settling time. It also allows the sludge to be laid more evenly on the sludge discharge site, reducing the amount of subsequent land leveling work.

[0023] Preferably, the cross-sections of the cofferdam and dike in S12 and the cross-section of the guide beam in S13 are trapezoidal structures, with the top width of the cofferdam, dike, and guide beam ≥ 4m; and the slope of the cofferdam, dike, and guide beam ≥ 1:2.5. More preferably, when constructing the cofferdam and dike, impermeable geotextile is laid on the water-facing side of the cofferdam and dike; in S13, when constructing the guide beam, each water-facing side of the guide beam is laid with impermeable geotextile.

[0024] In this invention, the top width of the cofferdam, dike, and guide beam is controlled to be above 4m to effectively ensure the load-bearing capacity of these components and prevent collapse. Impermeable geotextile is laid on the water-facing surfaces of the cofferdam, dike, and guide beam to further prevent collapse and ensure structural stability. Furthermore, during actual construction, the compaction degree of the cofferdam, dike, and guide beam can be controlled to be above 0.91 to further ensure structural stability. During actual construction, the elevation of the cofferdam, dike, and guide beam is higher than the designed sludge discharge elevation; the specific elevation can be determined according to the project level.

[0025] Preferably, in actual construction, in S15, the thickness of the permeable sand and gravel is 75-100 mm; the thickness of the reverse osmosis coarse sand layer is 75-100 mm; the permeable sand and gravel are laid on both sides and top of the drainage pipe (including drainage main pipe and drainage branch pipe) to fix the drainage pipe; the reverse osmosis coarse sand is filled on both sides and top of the permeable sand and gravel, which has a reverse osmosis effect and prevents the water that has seeped into the drainage ditch from seeping back into the bottom mud layer.

[0026] Preferably, both the drainage main pipe and the drainage branch pipe are made of PVC pipe, with the diameter of the drainage branch pipe being 50-100 mm and the diameter of the drainage main pipe being 100-200 mm. In actual construction, the two ends of the drainage branch pipe are sealed, and the two ends of the drainage main pipe extend out of the cofferdam, with one end connected to the outside air and the other end connected to the water pump set to ensure normal drainage.

[0027] In S14, the top of the permeable perforated pipe is sealed during installation (i.e., the permeable perforated pipe is a blind permeable pipe), and a filter cloth is wrapped around the permeable perforated pipe to prevent sediment from entering (to avoid sediment clogging the permeable perforation holes). The permeable perforated pipe is made of PVC pipe with a diameter of 150-300 mm. Using large-diameter pipes ensures a sufficient number of permeable holes and permeable area, providing more permeability possibilities for pore water in the bottom sediment.

[0028] Preferably, in step S12, the construction of the drainage unit at the drainage outlet of each dehydration and drying zone includes the following: pre-embedding a gate box with a side inlet at the drainage outlet of the dehydration and drying zone; horizontally installing a drainage pipe on the lower part of the other side wall of the gate box; and the outlet end of the drainage pipe being located outside the cofferdam. This invention reduces the amount of construction work by installing the gate box and drainage pipe during the construction of the cofferdam.

[0029] Preferably, in step S11, when excavating the second drainage ditch, the bottom surface of the second drainage ditch is a slope with a certain gradient. The inclination direction of the second drainage ditch in each dehydration and drying zone is consistent, which facilitates the water that has seeped into the drainage ditch to eventually flow along the slope to the lowest point, so as to completely drain the seepage water in the bottom mud.

[0030] Preferably, in step S14, after installing the permeable perforated pipe, the method further includes: installing a first water pump outside the cofferdam and connecting one end of the drainage main pipe to the inlet of the first water pump.

[0031] In S3, the step of using a water pump set to extract the permeable water from the bottom sediment layer includes the following: using a first water pump to extract part of the permeable water that flows back from the permeable flower pipe and permeable branch pipe to the permeable main pipe.

[0032] When no water flows out of the outlet of the first water pump, a sump is dug at one end of the second drainage ditch, and a second water pump is installed outside the cofferdam. The inlet pipe of the second water pump is inserted into the sump, and the second water pump is used to discharge part of the seepage water that has flowed into the second drainage ditch.

[0033] When there is no obvious water outflow from the drain outlet, use an excavator to dig a water collection pit at one end of the second drainage ditch so that the seepage water can eventually flow back into the water collection pit, so as to discharge the seepage water as soon as possible and improve the drying efficiency.

[0034] The advantage of this invention is that the guide ports in each dewatering and drying zone are arranged diagonally, and the mud-water inlet and outlet in the dewatering and drying zone are also arranged diagonally. The mud-water moves in an S-shaped curve towards the outlet unit in the drying zone, which prolongs the flow path of the mud-water and increases the free settling time of the sludge in the discharge field. This not only ensures the clarification effect of the mud-water reaching the outlet and reduces the loss of silt, but also improves the discharge efficiency of open water.

[0035] This invention involves excavating crisscrossing drainage ditches and constructing a drainage pipe network within the cofferdam. A water pump unit can be used to quickly discharge pore water from the drainage pipe network and pore water that has seeped into the drainage ditches, thereby accelerating the discharge of pore water and further speeding up the dehydration and drying of the bottom sediment. In addition, this invention lays a layer of medium-coarse sand with reverse osmosis in the drainage ditches, which can effectively prevent reverse osmosis and ensure the drying effect.

[0036] The sludge discharge site constructed by this invention has two or more dewatering and drying zones. Each dewatering and drying zone has an inlet (i.e., a mud-water inlet) and an outlet. The dewatering and drying zones can be switched or operate simultaneously. Depending on the actual situation, the outlet unit can be closed and the sludge can be discharged to another drying zone. This further improves the dewatering and drying efficiency of the bottom mud, shortens the drying time, and enables the sludge discharge site to dry quickly, so as to minimize the occupation time of the sludge discharge site. In addition, the zoned dewatering and drying also allows the mud layer to be laid more evenly on the sludge discharge site, reducing the amount of land leveling work. Attached Figure Description

[0037] Figure 1 This is a plan view of the sludge discharge site constructed according to the present invention.

[0038] Figure 2 yes Figure 1 Plan view of the dehydration and drying zone on the right side of the middle section.

[0039] Figure 3 yes Figure 2 Enlarged sectional view along the DD direction.

[0040] Figure 4 yes Figure 2 EE-directed sectional view.

[0041] Figure 5This is a construction status diagram of the second drainage ditch of the present invention.

[0042] Figure 6 This is a construction status diagram of the drainage unit described in this invention. Detailed Implementation

[0043] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the scope of protection of the present invention is not limited to the following embodiments.

[0044] It should be noted that, in this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] This invention provides a method for dewatering and drying bottom sediment from river and lake dredging. This method achieves rapid dewatering and drying of bottom sediment by constructing a sludge discharge site with two or more dewatering and drying zones. This not only ensures the clarity of the open water at the outlet (i.e., the water after sediment settling), reduces sediment loss, and improves the construction efficiency of the sludge discharge site, but also effectively improves the drainage efficiency of pore water, further improving the dewatering and drying efficiency of the settled bottom sediment layer within the sludge discharge site, shortening the land occupation time and reducing land occupation costs.

[0046] The following describes the invention in more detail using dredged sediment from a lake as an example. The dewatering and drying method for dredged sediment from rivers and lakes described in this invention involves first constructing a sludge discharge site with two dewatering and drying zones, then pumping the lake sediment (containing a significant amount of water, a mud-water mixture) to the dewatering and drying zones, and finally discharging it using a pumping unit. The specific steps include:

[0047] S1, construct a sludge discharge site with two (according to sediment) dewatering and drying zones, and excavate an external drainage ditch 14 outside the sludge discharge site to discharge water into the lake through the external drainage ditch 14;

[0048] Since some substances in the upper soil layer may affect the reuse of the solidified mud layer, the present invention removes about 30cm of upper soil layer to reduce the impact of soil on the solidified mud layer and improve the utilization rate of the solidified mud layer.

[0049] The sludge discharge site has two dewatering and drying zones, which can work simultaneously or alternately until the designed sludge discharge elevation is reached, thus improving the dewatering and drying efficiency of the bottom sludge.

[0050] The dehydration and drying zone preferably has a rectangular structure, with the long diagonal corresponding to the mud-water inlet and the outlet, respectively, to extend the mud-water outlet path as much as possible and increase the sediment settling time.

[0051] S2, the mud and water are pumped from the inlet of the dehydration and drying zone to the dehydration and drying zone. During the flow of the mud and water in the dehydration and drying zone, the solid part gradually settles down and pushes the separated open water to flow towards the drain outlet. Then, it flows outward through the drain outlet of the dehydration and drying zone into the external drainage ditch 14.

[0052] S3. When there is no obvious outflow of water at the drain outlet or the clarity at the drain outlet is low, close the drain outlet and use the water pump set to pump out the seepage water in the bottom sediment layer.

[0053] The method for constructing the sludge discharge site with two dewatering and drying zones in S1 includes the following:

[0054] S11, after clearing the topsoil (approximately 30cm thick), excavate multiple first drainage ditches 1 and second drainage ditches 2 at intervals at the designed location. First drainage ditches 1 and second drainage ditches 2 are rectangular, 0.5m wide and 0.5m deep; and the first drainage ditches 1 and second drainage ditches 2 are excavated in a crisscross pattern, as detailed in [reference needed]. Figure 1 and Figure 2 ;

[0055] S12, construct a cofferdam 3 and a partition 4 using the topsoil and the soil obtained from excavating drainage ditches. The partition 4 is located inside the cofferdam 3 and is parallel to the short side of the cofferdam 3. That is, the area enclosed by the cofferdam 3 is divided into two parts by the partition 4 (as equally as possible).

[0056] When constructing cofferdam 3, the drainage unit can be constructed at the corner of cofferdam 3 (i.e., the drainage outlet of the dewatering and drying zone) to improve the construction efficiency of the sludge discharge site. If the drainage unit is constructed after the cofferdam 3 is completed, the cofferdam 3 will need to be excavated again, which will result in a large amount of work and be labor-intensive and time-consuming.

[0057] S13, construct guide beams 5 in each dewatering and drying zone (only two are shown in the figure due to the large size of the sludge discharge site). One end of each guide beam 5 forms a guide opening at a distance of 2-3m from the cofferdam 3. The guide openings are arranged diagonally to make the mud and water flow in an S-shape. The more guide beams 5 there are, the longer the mud and water travel path and the longer the corresponding settling time, ensuring that the solid parts in the mud and water settle down as much as possible. See details below. Figure 1-2 ;

[0058] When constructing the diversion duct 5, since the direction of the diversion duct 5 is perpendicular to the direction of the second drainage ditch 2, in order to prevent the diversion duct 5 from filling the second drainage ditch 2 below, a partition is laid on top of the second drainage ditch 2.

[0059] When constructing the sludge discharge site, the diversion outlets in the dewatering and drying zone are arranged diagonally, as are the mud and water inlet and outlet in the dewatering and drying zone. This causes the mud and water to move in an S-shaped curve towards the outlet unit in the drying zone, which prolongs the flow path of the mud and water and increases the free settling time of the sludge in the discharge site. This not only ensures the clarification effect of the mud and water reaching the outlet, but also avoids the loss of silt and sand.

[0060] S14, a main drainage pipe 6 is laid in the first drainage ditch 1, and a branch drainage pipe 7 is laid in the second drainage ditch 2. The ends of the branch drainage pipe 7 are sealed. Permeable perforated pipes 8 (vertical) are installed on the main drainage pipe 6 and the branch drainage pipe 7 using connectors. The main drainage pipe 6, the branch drainage pipe 7, and the permeable perforated pipe 8 constitute a drainage network. See details below. Figure 2-4 ;

[0061] The ends of the drainage branch pipe 7 are sealed with end caps, and both ends of the drainage main pipe 6 extend outwards through the cofferdam 3. One end is open to the outside air to prevent negative pressure suction; the other end is connected to the first water pump 9, which quickly pumps out the pore water that has seeped into the drainage network. See details below. Figure 2 ;

[0062] S15, in the first drainage ditch 1 and the second drainage ditch 2, permeable sand and coarse sand that allows for reverse seepage are laid from the inside out. This not only fixes the drainage main pipe 6 and the drainage branch pipe 7, but also prevents pore water from seeping upwards.

[0063] In actual construction, the first drainage ditch 1 and the second drainage ditch 2 can be excavated while the cofferdam 3 is being constructed, so as to make full use of the soil obtained from the excavation of the first drainage ditch 1 and the second drainage ditch 2 and reduce the soil piling area.

[0064] During construction, an external drainage ditch 14 is constructed outside the cofferdam 3. The external drainage ditch 14 is excavated around the cofferdam 3 to provide drainage space for surface water and pore water. In actual construction, the external drainage ditch 14 can be excavated before the construction of the cofferdam 3, or it can be excavated while the cofferdam 3 is being constructed, or it can be excavated after the construction of the cofferdam 3 is completed.

[0065] The sludge discharge site constructed by this invention has two dewatering and drying zones (of course, it can also be three or more depending on the amount of sand discharged). Each dewatering and drying zone has a mud-water inlet and a water outlet. The dewatering and drying zones can be switched to different working zones. Depending on the actual situation, the water outlet unit can be closed and the sludge can be discharged to another drying zone. In this process, it is only necessary to switch the outlet of the mud-water pipeline from the mud-water inlet of one drying zone to the mud-water inlet of another drying zone. Mud-water is pumped into another drying zone for drying, realizing one inlet and multiple outlets, improving drying efficiency, shortening drying time, and enabling the sludge discharge site to dry quickly, so as to minimize the occupation time of the sludge discharge site.

[0066] In addition, compared with an undivided sludge dump, the present invention further improves the drying efficiency by dividing the constructed sludge dump into sections, while ensuring the settling time of the mud and water, and allows the sludge to be laid more evenly on the sludge dump, reducing the amount of subsequent land leveling work.

[0067] In actual construction, the cross-sections of cofferdam 3 and dike 4 in S12 and guide beam 5 in S13 are all trapezoidal structures, as detailed in [reference needed]. Figure 3-4 Their cross-sectional dimensions are consistent, with a top width controlled at over 4m, a slope controlled at 1:2.5, and a compaction degree controlled at over 0.91, improving the structural stability of cofferdam 3, dike 4, and guide beam 5 and preventing collapse. Furthermore, the elevations of cofferdam 3, dike 4, and guide beam 5 are all higher than the designed sludge discharge elevation; the specific elevations can be determined based on the sludge discharge volume.

[0068] In actual construction, after the cofferdam 3, the dike 4, and the guide beam 5 are constructed, impermeable geotextile is laid on the water-facing side of the cofferdam 3, each water-facing side (i.e., slope) of the dike 4, and each water-facing side (i.e., slope) of the guide beam 5. This invention lays impermeable geotextile on the compacted cofferdam 3 and other civil structures, improving impermeability and the stability of the civil structures, preventing collapse, and ensuring normal settlement and drainage of mud and water.

[0069] In a preferred embodiment of the present invention, the specific construction of the permeable sand and gravel and the reverse seepage medium-coarse sand in S15 includes the following: taking the laying of permeable sand and gravel and the reverse seepage medium-coarse sand in the second drainage ditch 2 as an example, firstly, a permeable sand and gravel layer 10 with a thickness of 75~100 mm is laid on both sides and the top of the drainage branch pipe 7 to form a permeable sand and gravel layer 10 (i.e., the permeable sand and gravel layer 10 has a door-shaped structure) to fix the drainage branch pipe 7; then, a reverse seepage medium-coarse sand layer 11 with a thickness of 75~100 mm is laid on both sides and the top of the permeable sand and gravel layer 10 to form a reverse seepage layer 11. This not only prevents the drainage branch pipe 7 from lateral displacement and sliding problems, but also prevents the water that has seeped into the drainage ditch from seeping upwards, so that the water that has seeped down flows along the second drainage ditch 2 to the collection pit behind, realizing the timely discharge of the seepage water and improving the drying rate.

[0070] In a preferred embodiment of the present invention, both the drainage main pipe 6 and the drainage branch pipe 7 are made of PVC pipe, the diameter of the drainage branch pipe 7 is 50-100 mm, and the diameter of the drainage main pipe 6 is 100-200 mm.

[0071] The permeable perforated pipe 8 also uses PVC pipe with a diameter of 150-300 mm. Permeable holes are evenly distributed on the permeable perforated pipe 8. The use of a large-diameter pipe ensures a large number of permeable holes and a large permeable area, providing more possibilities for the permeability of pore water in the bottom sediment. Furthermore, during installation, the top of the permeable perforated pipe 8 is sealed (a blind seal can be used), and a filter cloth is wrapped around it to prevent sediment from entering and affecting the normal drainage of the drainage network. Moreover, in actual installation, the height of the permeable perforated pipe 8 is 200 mm higher than the designed sludge discharge site elevation. The permeable perforated pipe 8 is connected to the drainage main pipe 6 and drainage branch pipe 7 via a tee or straight connector, and a sealing ring is used at the connection to ensure a stable connection.

[0072] In a preferred embodiment of the present invention, in S12, a drainage unit is constructed at the drainage outlet of each dewatering and drying zone, including the following: a gate box 12 with a side inlet is installed at the drainage outlet of the dewatering and drying zone (diagonally arranged with respect to the silt inlet of the dewatering and drying zone). (The lower part of the gate box 12 is buried in the soil layer, and the height of its side inlet is higher than the height of the settled silt layer, allowing the upper layer of clear water to flow out). A drainage pipe 13 (preferably a steel pipe with a diameter of 300-400 mm) is horizontally installed at the lower part of the other side wall of the gate box 12 (opposite to the side inlet). The outlet end of the drainage pipe 13 is located outside the cofferdam 3 and extends into the external drainage ditch 14, allowing the surface water obtained during the silt settling process to enter the gate box 12 through the side opening and then be discharged into the external drainage ditch 14 by the drainage pipe 13, thus realizing the timely discharge of surface water. For the specific structure, see [link to specific details]. Figure 6 .

[0073] To maximize the drainage of pore water that has seeped into the drainage ditch, the bottom of the second drainage ditch 2 is sloped (i.e., has a certain gradient), and the height of the slope gradually decreases towards the dike 4. During the sediment solidification process, some of the pore water in the sediment naturally seeps into the first drainage ditch 1 and the second drainage ditch 2 below. Due to the slope of the second drainage ditch 2, this portion of pore water eventually converges under the action of slope force, achieving pore water discharge and further improving the drying rate of the sediment.

[0074] In a preferred embodiment of the present invention, in S14, after installing the permeable flower pipe 8, the method further includes: installing a first water pump 9 outside the cofferdam 3, and connecting one end of the drainage main pipe 6 to the inlet of the first water pump 9; each drainage main pipe 6 is connected to a first water pump 9, and multiple first water pumps 9 work synchronously to improve drainage efficiency; in addition, the drainage main pipe 6 is connected to the outside to replenish air and ensure pumping efficiency.

[0075] In a preferred embodiment of the present invention, step S2 includes the following specific details:

[0076] For ease of distinction, the guide beam 5 adjacent to the dike 43 is designated as guide beam 5A1, and the guide opening between it and the cofferdam 31 is designated as guide opening B1; the guide beam 5 adjacent to the short side of the cofferdam 31 is designated as guide beam 5A2, and the guide opening between it and the cofferdam 31 is designated as guide opening B2; guide beam 5A1 and the dike 3 form the drainage zone C1, guide beam 5A1 and guide beam 5A2 form the drainage zone C2, and guide beam 5A2 and the cofferdam 31 form the drainage zone C3; the mud and water inlet of the dewatering and drying zone is marked as F1, and its drainage outlet is marked as F2, with F1 and F2 arranged diagonally;

[0077] The sludge pump will pump the sludge and water obtained from the lake dredging to point F1. The power provided by the sludge pump will cause the sludge and water to flow in the drainage area C1, and then turn around and flow into the drainage area C2, adjusting the flow direction of the sludge and water. After the sludge and water reaches the end, they will turn around and flow into the drainage area C3. That is, the sludge and water flow in the dewatering and drying area in an S-shaped route, which prolongs the flow path of the sludge and water, increases the free settling time of the sludge in the discharge site, ensures the clarification effect at the drainage outlet, reduces the amount of sediment discharge, improves the drying efficiency, and also allows the sludge to be laid more evenly in the dewatering and drying area, reducing the amount of leveling work in the later stage.

[0078] During the flow of mud and water, the mud layer in the mud and water gradually settles down and the surface water after settling moves towards the drain outlet. The settled clear water enters the gate box 12 and enters the external drainage ditch 14 through the drain pipe 13, realizing the drainage of the surface water, while the mud layer or turbid water with poor separation effect is blocked.

[0079] When the mud-water separation effect at the drainage unit is not ideal, the gate at the side opening of the gate box can be closed, and the drainage unit of another dewatering and drying zone can be opened to inject mud and water into the other dewatering and drying zone for mud-water separation and sludge solidification. The two drainage units drain water separately, which improves the dewatering efficiency of the bottom mud.

[0080] In a preferred embodiment of the present invention, step S3 includes the following specific details:

[0081] When the mud-water separation effect at the outlet is not ideal or the water flow in the outlet pipe 13 is not obvious, the outlet unit is shut down; the pore water in the mud layer enters the permeable flower pipe 8 through the permeable holes, and flows into the external drainage ditch 14 under the action of the first pump 9. The first pump 9 works continuously until there is no obvious drainage at its outlet.

[0082] In addition, a sump pit 15 is excavated at the lower end of the second drainage ditch 2, and a second water pump is installed outside the cofferdam 3. The inlet pipe of the second water pump is inserted into the sump pit 15, and the second water pump is used to discharge part of the seepage water that has flowed into the second drainage ditch 2. To improve pumping efficiency, each sump pit 15 can correspond to one second water pump; to improve drainage efficiency, the first water pump 9 and the second water pump can be started simultaneously to accelerate the discharge efficiency of pore water, further improve the dewatering and drying speed of the bottom sediment, and shorten the occupation time.

[0083] The drainage network, drainage ditch and water pump in this invention are combined to achieve rapid drainage of pore water, improve the drying speed of silt, and reduce the time and cost of temporary land acquisition. After drying, the permeable flower pipe 8, drainage main pipe 6 and drainage branch pipe 7 can be recycled and reused, reducing the cost of silt drainage and stockpiling and effectively meeting the needs of soil return and reclamation in the later stage of silt disposal site.

[0084] Finally, it should be emphasized that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still make modifications to the technical solutions described in the foregoing embodiments without creative effort, or make equivalent substitutions for some of the technical features. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for dewatering and drying sediment from river and lake dredging, characterized in that: The dehydration and drying method involves solidifying and draining the sludge by constructing a sludge discharge site, and includes the following steps: S1, construct a sludge discharge site with at least two dewatering and drying zones; S2, the mud and water are pumped from the inlet of the dewatering and drying zone to the dewatering and drying zone. The mud and water settle and separate in the dewatering and drying zone and produce clear water. The clear water flows out through the outlet of the dewatering and drying zone. S3, using a pump set to extract the seepage water from the bottom mud layer: using the first pump to extract part of the seepage water that flows back from the permeable flower pipe and permeable branch pipe to the permeable main pipe; when there is no water flowing out of the outlet of the first pump, a sump pit is dug at one end of the second drainage ditch, a second pump is installed outside the cofferdam, the inlet pipe of the second pump is inserted into the sump pit, and the second pump is used to discharge part of the seepage water that flows into the second drainage ditch; The sludge discharge site with at least two dewatering and drying zones described in S1 includes the following: S11, clear the top layer of soil, and excavate the first and second drainage ditches at the designed locations. Both the first and second drainage ditches are multiple and crisscross, and the bottom of the second drainage ditch is a slope with a certain gradient. S12, construct a cofferdam and a partition dike using the soil obtained from cleaning and excavation. The partition dike is parallel to the short side of the cofferdam. The partition dike divides the cofferdam into at least two dewatering and drying zones. When constructing the cofferdam, construct a drainage unit at the drainage outlet of each dewatering and drying zone: pre-embed a gate box with a side inlet at the drainage outlet of the dewatering and drying zone, and horizontally install a drainage pipe at the lower part of the other side wall of the gate box. The outlet end of the drainage pipe is located outside the cofferdam. S13, construct at least two guide channels in each dewatering and drying zone, with one end of each guide channel forming a guide opening 2-3m away from the cofferdam, and the guide openings are arranged diagonally to make the mud and water flow in an S-shape. During the construction of the diversion channel, a partition board is laid above the second drainage ditch; S14, Lay a main drainage pipe in the first drainage ditch and a branch drainage pipe in the second drainage ditch, sealing the ends of the branch drainage pipes; Install permeable perforated pipes on the main drainage pipes and branch drainage pipes using connectors; Both the main drainage pipes and branch drainage pipes are made of PVC pipes, with the branch drainage pipes having a diameter of 50-100mm and the main drainage pipes having a diameter of 100-200mm. When installing the permeable perforated pipes, seal the top of the permeable perforated pipes and wrap the permeable perforated pipes with filter cloth to prevent silt from entering. The permeable perforated pipes are made of PVC pipes with a diameter of 150-300mm; After the permeable perforated pipes are installed, install the first water pump outside the cofferdam and connect one end of the main drainage pipe to the inlet of the first water pump. S15, in the first and second drainage ditches, permeable gravel and reverse seepage medium-coarse sand are laid from the inside out to fix the drainage main pipe and drainage branch pipe; wherein, the thickness of the reverse seepage medium-coarse sand layer is 75-100mm. The cross-sections of the cofferdam and dike in S12 and the cross-section of the guide beam in S13 are trapezoidal structures, with the top width of the cofferdam, dike and guide beam ≥ 4m and the slope of the cofferdam, dike and guide beam ≥ 1:2.

5.

2. The method for dewatering and drying river and lake dredged sediment according to claim 1, characterized in that: In S12, when constructing the cofferdam and the dike, the water-facing surfaces of the cofferdam and the dike are covered with impermeable geotextile; in S13, when constructing the guide beam, each water-facing surface of the guide beam is covered with impermeable geotextile.

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