Underwater dredging generally refers to equipping the ship with dredging machinery and tools. As a construction platform, the dredger operates dredging equipment to excavate silt on the water surface. And transported to the onshore storage yard through the pipeline transportation system. ? Underwater dredging has the following methods.
a.？ Grasp dredging: Excavate silt at the bottom of the river with grab dredgers. Through the grab bucket on the forearm of grab dredger, the grab bucket is inserted into the bottom of the river by oil pressure, and the bucket is closed to grab underwater silt. Then lift the swing and open the grab. Unload the sludge directly to the barge parked next to the dredger. Dig? Swing? Mud unloading circulation operation. ? The cleaned sludge is transported to the sludge yard by barge. Shore grab is still needed to unload mud from barge. Transport the mud from the barge to the mud yard on the shore.
Grab dredger is suitable for dredging with thick silt layer. There are many obstacles in the construction area. Small rivers are mostly used for dredging projects to expand the flood discharge section of rivers. ? Grab dredgers are flexible and maneuverable. There is no garbage in the river? Stones and other obstacles? Suitable for digging hard earthwork or earthwork with more impurities and garbage; Moreover, the construction technology is simple, the equipment is easy to organize, the project investment is small, and the construction process is not affected by the weather. However, the grab dredger is not sensitive to extremely weak sediment, and it is easy to "dig into the hard soil at the lower part of the river bed, thus leaking a lot of surface sediment, especially floating mud" during excavation; It is easy to cause the floating mud on the surface to return to the water body after being stirred. According to the engineering experience [3-5], the dredging rate of grab dredging can only reach about 30%. In addition, grab dredging is easy to cause the omission of floating mud and strongly disturb the bottom mud, which often fails to achieve the original purpose in dredging projects aimed at improving water quality.
b.？ Pump suction dredging: also known as jet suction dredging, it is equipped with a hydraulic flushing water gun and a mud suction pump. In the 1 cylinder cover, the mud at the bottom is stirred into mud with a water gun, sucked out by the mud pump at the other side, and then sent to the storage yard on the shore through the pipeline. The whole set of machines and tools are loaded on the ship and removed when moving. Another pumping method is to use compressed air as power to pump and discharge sludge. The cylindrical pump barrel with an opening at the lower end sinks to the bottom of the water under the action of gravity, and then negative pressure is applied in the pump barrel. Under the static pressure of water and the vacuum negative pressure of the pump barrel, soft mud is sucked into the pump barrel. Then, compressed air is used to press the sludge in the cylinder into the sludge discharge pipe, and the sludge is transported to the sludge carrier or the onshore storage yard through the sludge discharge valve and the sludge conveying pipe.
The equipment for pumping and dredging is relatively simple. Can be equipped with small and medium-sized ships and equipment, suitable for small river construction. ? In general, it is easy to suck out a lot of river water. Resulting in an increase in the workload of subsequent mud treatment. ? At the same time? The composition of river garbage in China is complex. Different sizes are easy to block the mud suction port.
c.？ Ordinary cutter suction dredging: ordinary cutter suction dredging is mainly completed by cutter suction dredgers. ? Cutter suction dredger is composed of floating body,? Hinge reamer? On straw? Lower the suction pump? Power, etc. ? It uses the rotary motion of the cutter installed at the front of the bridge in front of the ship. Cutting and stirring riverbed sediments. Mix mud with water. Mud is formed and sucked into the vacuum generated by the centrifugal pump on board. Make the mud enter the suction end of the mud pump along the mud suction pipe. It is transported by fully enclosed pipeline (after the row spacing exceeds the rated row spacing of dredgers, the relay pump boats are connected in series in the middle for pressurized transportation) to the storage yard.
Ordinary cutter suction dredging is suitable for medium and large mud layers. River dredging. ? Ordinary cutter suction dredging is a kind of dredging. Cloud? The integrated construction technology of mud blowing adopts fully enclosed pipeline to transport mud. Will not sprinkle mud, mud leakage; In the process of dredging, the navigation of the river channel will not be affected, and the construction will not be affected by the weather. Using GPS and echo detector to control the construction at the same time can improve the construction accuracy. Ordinary cutter suction dredging is easy to cause pollutant diffusion and serious siltation in sediment because of the open excavation with spiral slice cutter. The removal rate of sediments is generally around 70%. In addition, the low concentration of dredged mud will increase the amount of mud and the area of mud yard.
2. Environmental protection and dredging
Environmental dredging has two meanings. On the one hand, it refers to the dredging project aimed at improving water quality. On the other hand, it can avoid affecting the water environment as much as possible during the dredging process. ? The characteristics of environmental protection dredging are: (1) the dredging equipment should have high positioning accuracy and excavation accuracy, prevent leakage and over-excavation, and do not damage the native soil; ? (2) In the dredging process, the disturbance is prevented from spreading, the secondary pollution of water body is not caused, the turbidity of water body is reduced, the noise of construction machinery is controlled, and the normal life of residents is not disturbed; ? (3) Sludge dumps should be far away from residential areas to prevent secondary pollution during transportation.
Environmental protection cutter suction dredging is the most commonly used environmental protection dredging method at present. Suitable for tuba, tuba, and? China? Rivers, lakes and reservoirs. Mostly used in rivers. Environmental protection and dredging of lakes and reservoirs. ? Environmental protection cutter suction dredging is dredging by using environmental protection cutter suction dredger. ? Environmental protection cutter suction dredger is equipped with special environmental protection cutter head. In the process of dredging, the environmental protection reamer head is used to implement closed low disturbance dredging. The excavated mud is pumped by the high-power mud pump on the dredger and enters the mud conveying pipeline. It is transported to the designated mud unloading area through a fully enclosed pipeline.
The environmental protection cutter suction dredger is equipped with a special environmental protection cutter head, which can prevent the leakage and diffusion of polluted sludge. It can dredge thin polluted sediment with little disturbance to sediment. Avoid the diffusion and escape of polluted sediment. Can the sediment removal rate be achieved? More than 95%; The concentration of dredging is high, the mass fraction of dredging mud is above 70%, and the thickness of primary dredging mud is 20 ~ 1 10 cm. At the same time, the environmentally-friendly cutter suction dredger has high-precision positioning technology and on-site monitoring system, which can visually observe the excavation trajectory of dredging equipment through simulated animation; Through the depth indicator and echo sounder to control the elevation, the reaming depth can be accurately located and the excavation accuracy is high.
Sludge solidification technology treatment
What is the initial moisture content of dredged mud? More than 80%, and the silt particles are very fine, and the clay content is more than 20%, which makes the sludge deposition speed in the yard very slow and the consolidation time is very long. Within two or three years after siltation, only a natural hard shell layer with a thickness of about 20 cm can be formed on the surface of the dredged sludge yard, while the lower part is still fluid sludge with a water content of more than 1. 5 times the liquid limit, so it is very difficult to carry out ordinary foundation treatment. The surface treatment technology of the sludge yard is to use the in-situ solidification treatment technology of the sludge yard to artificially and rapidly form an artificial hard shell layer on the surface of the sludge yard. The artificial hard shell layer has certain strength and rigidity, which can meet the construction requirements of small machinery, and can be used for laying drainage boards and stacking construction, which is convenient for further treatment of the yard. The design of artificial hard shell is the key of surface treatment technology. Considering the requirements of subsequent construction, the strength parameters and design thickness of hard shell layer are determined through experiments and simulations. Artificial hard shell technology is often combined with sludge solidification technology to form solidified sludge artificial hard shell, and it is best to use polystyrene foam (EPS) particles to form light artificial hard shell.
The latest dredging technologies are as follows:
A. high-concentration in-situ environmental protection dredging method. ? Due to the environmental protection dredging methods commonly used at present, the concentration of dredged sludge is in? 15% ~ 20%, the volume of water molecules is much larger than that of soil particles, and the volume of dredged mud is about granular? 4~5? Time magazine. These high-content cement pastes often need to be placed in a large yard, and many dredging projects are seriously restricted because of the problems in the yard. High-concentration in-situ environmental protection dredging can reduce the capacity-increasing rate of mud during dredging, reduce the water content of mud during intermediate transportation, and directly turn mud into earth material that can be used for filling. Therefore, in order to save land and reduce the cost of dredging and sludge treatment, high concentration in-situ environmental protection dredging technology has become the future development direction.
The development trend of.
B. Rapid drainage technology for sludge in the storage yard. ? At present, most of the silt dredged in inland rivers is piled up in the yard. ? Silt yard adopts foundation treatment. After solving the problem that it is in a swamp state for a long time, it can be used for buildings. Scenery? Land used as farmland. ? And this foundation treatment process is the process of silt consolidation and drainage. ? Mud has a high clay content. Poor water permeability and long consolidation time under self-weight. The strength after self-weight consolidation is low. ? The rapid drainage and consolidation of silt has become an urgent problem. ? Application of vacuum preloading method and surcharge preloading method in soft soil foundation. Silt is often difficult to play a good role. The water content of silt is extremely high. In the flowing state, the effective stress between particles is very low. Under the condition of high pressure vacuum, sludge particles will flow with interstitial water. So that the drain plate is blocked and cannot drain water. ? How to solve the problem of silt blockage in drainage system has become the key to rapid drainage of silt. ? The rapid drainage technology of sludge in storage yard is to lay multi-layer and multi-row horizontal drainage channels in sludge. Its layer spacing,? All the line spacing? 60? ~80 cm？ Around, a high-density drainage network is formed under the mud. Connecting the pipe network with the horizontal drainage pipe sealed on the ground, and then connecting it with the jet drainage device, pumping water can accelerate the drainage speed of sludge. At present, the development of this technology and its key problems are still in the initial exploration stage.
Sludge recycling technology
Sludge resource utilization technology includes heat treatment method of sludge brick making. ? Heat treatment method is to convert sludge into building materials by heating and sintering. According to different principles, it can be divided into sintering and melting. ? Sintering is achieved by heating at 800 ~ 65438 0200℃. Dehydrated sludge? Decomposition of organic components? Adhesion between particles can be used to make bricks or cement if the moisture content of sludge is appropriate. Melting is by heating? 1 200 ~ 1 500℃ dewaters sludge, decomposes organic components and melts inorganic minerals. The molten slurry can be made into ceramsite after cooling treatment. Heat treatment technology is characterized by high added value of products. However, the amount of sludge that can be treated by heat treatment technology is very limited. Like an ordinary brick factory? 1? Can you consume silt in one year? 5? Wan? M3, at present, can not meet the demand of millions of cubic meters of dredged sludge treatment in China. From the point of view of large-scale industrial sludge treatment, solidification, drying and sludge resource utilization technology are very important, and if combined with yard treatment technology, it will show greater benefits.
Using Smith Barney environmental protection sludge dehydrator can effectively reduce the water content of sludge and reduce the later drying cost. Sludge comes in, mud cakes and clear water come out, and clear water can raise fish! National high-tech enterprise certification, reliable product technology, market recognition and good reputation are your wise choice for dredging rivers!