A construction method for pre-buried vertical drainage device in mud receiving area

Abstract

The present invention relates to the technical field of pretreatment construction of onshore mud receiving areas, and in particular to a construction method for pre-buried vertical drainage devices in mud receiving areas. The method comprises: filling a cofferdam to form a mud receiving area; making a vertical drainage device; burying the vertical drainage device before dredging and filling; performing filling operations; burying a moisture content monitoring device in the mud receiving area after filling is completed; excavating and transporting the dredged soil after it meets the design requirements; and reusing the vertical drainage device to carry out the next dredging and filling construction. The present invention can quickly and effectively drain the moisture in the lower layer of dredged soil, reduce the moisture content of the dredged soil, and change the physical state of the dredged soil. At the same time, the method can reuse the drainage device without the need to repeatedly build drainage channels. While shortening the drying time of the dredged soil, it saves engineering costs, is energy-saving and environmentally friendly, and effectively solves the problem of excessive moisture content of the lower layer of dredged soil and difficulty in transportation and transportation.

Description

Technical Field

[0001] The invention relates to the technical field of pretreatment construction of onshore mud receiving areas, and in particular to a construction method for a pre-buried vertical drainage device in a mud receiving area. Background Art

[0002] In recent years, due to the shortage of land resources, dredging and filling projects have increased. After the dredged soil is filled in the landside receiving area, it is often necessary to dry it to meet the design requirements before it is transported to other areas for use. And because the scope of the receiving area is limited, there are cases where the receiving area is filled and dredged soil is transported back and forth multiple times.

[0003] Since conventional drainage consolidation technology requires the installation of drainage devices after filling, and conventional drainage consolidation technology can only satisfy the drainage and consolidation of dredged soil once and cannot be reused, drainage devices must be installed again after each filling of the mud receiving area. Conventional technology not only greatly affects the dredging and filling period, but also has high costs and low utilization rate of the mud receiving area. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a construction method for pre-buried vertical drainage device in mud receiving area, which shortens the drying time of dredged soil, saves engineering cost, is energy-saving and environmentally friendly, and effectively solves the problem of high moisture content of lower dredged soil and difficulty in transportation.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a construction method for pre-buried vertical drainage device in mud receiving area, characterized in that it comprises the following steps:

[0006] The first step is to build a cofferdam to form a mud receiving area. The cofferdam is built around the area to be filled. The cofferdam body is constructed with impermeable materials. The top width of the cofferdam is 2m. The slope on the side close to the mud receiving area is set at 1:2, and the slope on the other side is set at 1:2.5. At the same time, a layer of non-woven geotextile is laid on the side of the cofferdam close to the mud receiving area, and a sedimentation tank and a drainage outlet are set on the sea side to discharge the water in the dredged soil into the sea while ensuring environmental protection requirements.

[0007] The second step is to make a vertical drainage device. After the cofferdam in the mud receiving area is completed, start making the vertical drainage device, 1 / 3 of which is driven into the original ground, and the remaining 2 / 3 is above the original ground. During dredging and filling, the elevation of the filled soil is controlled to ensure that the top elevation of the vertical drainage device is 0.2m higher than the top elevation of the filled soil.

[0008] The third step is to bury the vertical drainage device before dredging and filling. Before dredging and filling, the vertical drainage device is prefabricated and buried, and the vertical drainage device is arranged in a square with a spacing of 10×10m. During the driving process, the elevation control is mainly used to ensure that the vertical drainage device is stable after the driving is completed. After the vertical drainage device is driven, the steel pipe is filled with medium-coarse sand, and the mud content of the medium-coarse sand is less than 5%;

[0009] The fourth step is to carry out the filling operation. After the vertical drainage device is installed, the filling operation of the mud receiving area begins. The offshore dredged soil is blown into the mud receiving area through the mud discharge pipeline. During the filling process, the overall filling elevation of the mud receiving area is controlled to ensure that the mud blowing port forms a slope of not less than 0.5% to the drainage port. At the same time, during the filling process, the mud blowing port must be kept away from the drainage port.

[0010] The fifth step is to bury a moisture content monitoring device in the mud receiving area after the filling is completed; after the filling is completed in the mud receiving area, 4 automatic moisture content monitoring devices are arranged. First, the moisture content monitoring device is buried in the dredged soil. To ensure that the moisture content index of the bottom silt meets the requirements, the burial depth is determined to be 3m, and it is connected to the upper data receiving device through a connecting line. The data receiving device can automatically display the moisture content index of the dredged soil in real time. When the moisture content of the dredged soil reaches below 20%, the dredged soil transportation construction is carried out;

[0011] Step 6: After the dredged soil meets the design requirements, excavation and transportation are carried out; the results are displayed by the moisture content monitoring device. When the values ​​of the 4 moisture content monitoring devices are all less than 20%, the moisture content of the dredged soil in the mud receiving area meets the design requirements and transportation construction can be carried out. During the excavation process, the embedded vertical drainage device is protected, and workers are used to cooperate in excavation within 1m around the vertical drainage device;

[0012] Step 7: Repeat the use of the vertical drainage device to carry out the next dredging and filling operation; after the dredged soil is transported, continue the filling operation in the mud receiving area, repeat the construction from Step 4 to Step 6, and complete the subsequent filling and transportation of dredged soil;

[0013] Step 8, summary of application effects: Through the above steps, a summary conclusion is drawn, proving that the invention can solve the core problem of the slow decrease in moisture content of the lower dredged soil during multiple filling and drying and transportation of the dredged soil in the mud receiving area. By pre-burying the drainage device before filling in the mud receiving area, the drying time can be greatly shortened, and the drainage device can be reused many times after being set up once, reducing the construction of drainage channels for the dredged soil each time in the conventional drainage consolidation construction method, which saves construction time and reduces construction cost investment, saving energy and protecting the environment. While meeting the conditions for the transportation of dredged soil, the utilization efficiency of the mud receiving area is improved, and the overall construction period of the project is reduced.

[0014] In the first step, the structural form of the cofferdam is designed and determined according to the height of the dredged soil in the mud receiving area. The top elevation of the cofferdam in the mud receiving area is set to +5.5m, 0.5m higher than the filling elevation. The cofferdam body is constructed with impermeable clay.

[0015] In the third step, the arrangement spacing and installation method of the drainage device are determined, and the vertical drainage device is arranged using a hydraulic pile driver.

[0016] In the fourth step, a suction dredger is used to blow the offshore dredged soil into the mud receiving area through a mud discharge pipeline.

[0017] In the sixth step, an excavator is used to dig the dredged soil, which is then loaded into a dump truck and transported to a designated area.

[0018] A pre-buried vertical drainage device for a mud receiving area is characterized in that it comprises a plurality of evenly distributed circular steel pipes with conical bottoms, wherein the steel pipes comprise, from bottom to top, an original soil portion, a dredged soil portion and an exposed portion, wherein a plurality of water filter holes are evenly arranged around the dredged soil portion, and a layer of non-woven geotextile is connected to the inner wall, and the specification of the geotextile is 400g / ㎡.

[0019] The water filtering holes have a diameter of 0.5 cm and are arranged in a plum blossom shape with a spacing of 5 cm.

[0020] The steel pipe is a Q345 circular steel pipe with a diameter of 50 cm, a wall thickness of 1 cm, and a length of 6.2 m. The interior of the steel pipe is filled with medium-coarse sand with a mud content of less than 5%.

[0021] The present invention buries drainage pipes before filling in the mud receiving area to quickly and effectively drain the moisture in the lower dredged soil, thereby reducing the moisture content of the dredged soil and changing the physical state of the dredged soil from fluid plastic to semi-solid. At the same time, the drainage device can be reused without the need to repeatedly build drainage channels. While ensuring the drainage and consolidation quality of the dredged soil and shortening the drying time of the dredged soil, the project cost is saved, energy is saved and the environment is protected, and the problem of excessively high moisture content of the lower dredged soil and difficulty in transportation and relocation is effectively solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the cross-section diagram of the cofferdam;

[0023] Figure 2 It is a schematic diagram of a vertical drainage device;

[0024] Figure 3 It is the plan location diagram of the vertical drainage device;

[0025] Figure 4 This is the plan layout of the moisture content monitoring device in the mud receiving area;

[0026] Figure 5 Schematic diagram of the moisture content monitoring device.

[0027] In the figure: steel pipe 1, original soil part 11, dredged soil part 12, exposed part 13, water filter hole 2, non-woven geotextile 3, cofferdam 4, original soil 5, dredged soil 6, moisture content monitoring device 7, moisture content monitoring sensor 71, connecting line 72, data receiving device 73, protective sleeve 74, arrangement spacing D. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings, but the present invention is not limited to the specific embodiments.

[0029] Example 1

[0030] like Figure 2 A pre-buried vertical drainage device for a mud receiving area includes a plurality of evenly distributed circular steel pipes 1 with conical bottoms. The steel pipes 1 include, from bottom to top, an original soil portion 11, a dredged soil portion 12, and an exposed portion 13. The dredged soil portion 12 is evenly provided with a plurality of water filtering holes 2 around it, and a layer of non-woven geotextile 3 is connected to the inner wall.

[0031] The water filtering holes 2 have a diameter of 0.5 cm and are arranged in a plum blossom shape with a spacing D of 5 cm.

[0032] The steel pipe 1 is a Q345 round steel pipe with a diameter of 50 cm, a wall thickness of 1 cm, and a length of 6.2 m. The interior of the steel pipe 1 is filled with medium-coarse sand with a mud content of less than 5%.

[0033] Example 2

[0034] Project background: The water depth at the front of a certain wharf does not meet the design requirements, and dredging of the harbor is required. However, there is no suitable mud dumping point in the sea area around the project. The design requires the construction of a mud receiving area on land for filling and the transportation of dredged soil to the surrounding designated area. Due to the limited area of ​​the rear site, the dredging volume is much larger than the capacity of the mud receiving area. The dredging volume is about 2 million m³, and the single capacity of the mud receiving area is only 10 m³. The mud receiving area needs to be filled and dredged soil transported repeatedly.

[0035] The first step is to build a cofferdam to form a mud receiving area;

[0036] like Figure 1 , a cofferdam 4 for the mud receiving area is built around the area to be filled. The original surface elevation is -3m, the filling elevation is +7m, and the filling area is 50,000 square meters. The top elevation of the cofferdam 4 in the mud receiving area is set at +7.5m, which is 0.5m higher than the filling elevation. The cofferdam 4 is constructed with impermeable clay. The top width of the cofferdam 4 is 2m. The slope on one side close to the mud receiving area is set at 1:2, and the slope on the other side is set at 1:2.5 to ensure the stability of the cofferdam 4 in the mud receiving area during the filling and drying process. At the same time, a layer of non-woven geotextile 3 is laid on the side of the cofferdam 4 close to the mud receiving area to prevent the filling soil from seeping out of the cofferdam 4. A sedimentation tank and a drainage outlet are set on the sea side to discharge the water in the dredged soil 6 into the sea while ensuring environmental protection requirements.

[0037] The second step is to make a vertical drainage device;

[0038] After the cofferdam 4 in the mud receiving area is filled, a vertical drainage device is made according to the structure described in Example 1, 2m is driven into the original ground, and the remaining 4.0m is located in the dredging layer. During dredging and filling, the elevation of the dredged fill soil is controlled to ensure that the top elevation of the vertical drainage device is 0.2m higher than the top elevation of the dredged fill soil. The bottom is conical, which is convenient for the vertical drainage device to be driven in. A layer of non-woven geotextile 3 is arranged on the inner wall of the vertical drainage device located in the dredging layer to prevent the dredged soil 6 from entering the steel pipe 1 and blocking the drainage channel, ensuring that the dredged soil 6 can smoothly discharge the water.

[0039] The third step is to bury the vertical drainage device before dredging and filling;

[0040] like Figure 3 Before dredging and filling, the vertical drainage device is prefabricated and buried. The vertical drainage device is arranged in a square with a spacing of 10×10m using a hydraulic pile driver. The elevation control is mainly used during the driving process to ensure that the vertical drainage device is stable after the driving is completed. After the vertical drainage device is driven, the steel pipe 1 is filled with medium-coarse sand, and the mud content of the medium-coarse sand is required to be less than 5%.

[0041] The fourth step is to carry out blowing and filling operations;

[0042] After the vertical drainage device is completed, the filling operation of the mud receiving area begins. The dredger suction boat is used to blow the offshore dredged soil into the mud receiving area through the mud discharge pipeline. However, during the filling process, the overall filling elevation of the mud receiving area must be controlled to ensure that the mud blowing port forms a slope of no less than 0.5% to the drainage port, so that the water discharged from the dredged soil through the vertical drainage channel during the drying process flows to the drainage port. At the same time, during the filling process, it is necessary to ensure that the mud blowing port is far away from the drainage port.

[0043] The fifth step is to bury a moisture content monitoring device in the mud receiving area after the filling is completed;

[0044] like Figure 4-Figure 5 After the filling of the mud receiving area is completed, 4 automatic moisture content monitoring devices 7 need to be arranged. First, the moisture content monitoring sensor 71 is buried in the dredged soil 6. To ensure that the moisture content index of the bottom mud meets the requirements, the sensor is buried at a depth of 3m and connected to the upper data receiving device 73 through a connecting line 72. The data receiving device 73 can automatically display the moisture content index of the dredged soil 6 in real time. The moisture content of the dredged soil 6 in this project is required to be below 20% before the dredged soil can be transported.

[0045] Step 6: After the dredged soil meets the design requirements, it is excavated and transported;

[0046] The results are displayed by the moisture content monitoring device 7. When the values ​​of the 4 moisture content monitoring devices 7 are all less than 20%, it can be considered that the moisture content of the dredged soil in the mud receiving area meets the design requirements and the reverse transportation construction can be carried out. The dredged soil is excavated by an excavator, loaded and unloaded into a dump truck and then transported to the designated area. During the excavation process, attention should be paid to protecting the embedded vertical drainage device. Within 1m around the vertical drainage device, workers are used to cooperate in excavation to avoid damage to the vertical drainage device during the excavation process, which will affect the drainage effect of the dredged soil in the next cycle.

[0047] Step 7: Reuse the drainage device for the next dredging and filling operation;

[0048] After the dredged soil is transported, the filling operation in the mud receiving area can be continued, and the fourth to sixth steps can be repeated to complete a total of four filling and transportation operations of the mud receiving area.

[0049] Step 8: Summary of application effects;

[0050] After the construction is completed, the process of the present invention is compared and analyzed with the conventional process from three main aspects: cost, construction period, and environmental protection.

[0051] (1) Cost comparison analysis

[0052] Table 1 Cost of primary filling and dredged soil transportation in the conventional mud receiving area

[0053]

[0054] The volume of earth dredged and filled in a single operation is 400,000 m³, and processes 2-4 need to be repeated 5 times.

[0055] The total construction cost is = cofferdam filling × 1 + shallow foundation treatment × 5 + drainage system construction × 5 + dredged soil transportation × 5 = 80 + 48 × 5 + 88 × 5 + 50 × 5 = 10.1 million yuan.

[0056] Table 2 Cost of primary filling and dredged soil transportation in the mud receiving area of ​​the present invention

[0057]

[0058] The volume of earth dredged and filled in a single operation is 400,000 m³. As the drainage device can be reused, there is no need for multiple constructions, and only 3 processes need to be repeated 5 times.

[0059] The total construction cost is = cofferdam filling × 1 + drainage system buried before filling × 1 + dredged soil transportation × 5 = 80 + 3.2 million + 50 × 5 = 6.5 million yuan.

[0060] (2) Comparative analysis of construction period

[0061] Table 3 The construction period of primary filling and dredged soil transportation in the conventional process mud receiving area

[0062]

[0063] The volume of earth dredged and filled in a single operation is 400,000 m³, and processes 2-5 need to be repeated 5 times.

[0064] The total construction period is = cofferdam filling × 1 + shallow foundation treatment × 5 + drainage system construction × 5 + dredged soil consolidation × 5 + dredged soil transportation × 5 = 2 + 3 × 5 + 1 × 5 + 5 × 5 + 1 × 5 = 52 months.

[0065] Table 4 The construction period of the primary filling and dredged soil transportation in the mud receiving area of ​​the present invention

[0066]

[0067] The volume of earth dredged and filled in a single operation is 400,000 m³. As the drainage device can be reused, it does not need to be constructed multiple times, and only steps 4-5 need to be repeated 5 times.

[0068] The total construction period is = cofferdam filling × 1 + drainage system buried before filling × 1 + dredged soil consolidation × 5 + dredged soil transportation × 5 = 2 + 2 + 5 × 5 + 1 × 5 = 30 months.

[0069] (3) Comparative analysis of environmental protection

[0070] Conventional process: Multiple drainage device construction causes waste of resources and does not conform to the concept of green construction.

[0071] The process of the present invention: the drainage device can be reused to avoid waste of resources, which is in line with the national green construction development concept.

[0072] Conclusion: Through comparative analysis, the present invention has made great progress in cost, construction period and environmental protection compared with conventional processes. It shortens the drying time of dredged soil, saves project cost, is energy-efficient and environmentally friendly, and effectively solves the problem of excessive moisture content of the lower dredged soil and difficulty in transportation.

Claims

1. A construction method for pre-buried vertical drainage device in mud receiving area, characterized in that: The following steps are involved: The first step is to build a cofferdam to form a mud receiving area. The cofferdam is built around the area to be filled. The cofferdam body is constructed with impermeable materials. The top width of the cofferdam is 2m. The slope on the side close to the mud receiving area is set at 1:2, and the slope on the other side is set at 1:2.

5. At the same time, a layer of non-woven geotextile is laid on the side of the cofferdam close to the mud receiving area, and a sedimentation tank and a drainage outlet are set on the sea side to discharge the water in the dredged soil into the sea while ensuring environmental protection requirements. The second step is to make a vertical drainage device. After the cofferdam in the mud receiving area is completed, start making the vertical drainage device, 1 / 3 of which is driven into the original ground, and the remaining 2 / 3 is above the original ground. During dredging and filling, the elevation of the filled soil is controlled to ensure that the top elevation of the vertical drainage device is 0.2m higher than the top elevation of the filled soil. The third step is to bury the vertical drainage device before dredging and filling. Before dredging and filling, the vertical drainage device is prefabricated and buried, and the vertical drainage device is arranged in a square with a spacing of 10×10m. During the driving process, the elevation control is mainly used to ensure that the vertical drainage device is stable after the driving is completed. After the vertical drainage device is driven, the steel pipe is filled with medium-coarse sand, and the mud content of the medium-coarse sand is less than 5%; The fourth step is to carry out the filling operation. After the vertical drainage device is installed, the filling operation of the mud receiving area begins. The offshore dredged soil is blown into the mud receiving area through the mud discharge pipeline. During the filling process, the overall filling elevation of the mud receiving area is controlled to ensure that the mud blowing port forms a slope of not less than 0.5% to the drainage port. At the same time, during the filling process, the mud blowing port must be kept away from the drainage port. The fifth step is to bury a moisture content monitoring device in the mud receiving area after the filling is completed; after the filling is completed in the mud receiving area, 4 automatic moisture content monitoring devices are arranged. First, the moisture content monitoring device is buried in the dredged soil. To ensure that the moisture content index of the bottom silt meets the requirements, the burial depth is determined to be 3m, and it is connected to the upper data receiving device through a connecting line. The data receiving device can automatically display the moisture content index of the dredged soil in real time. When the moisture content of the dredged soil reaches below 20%, the dredged soil transportation construction is carried out; Step 6: After the dredged soil meets the design requirements, excavation and transportation are carried out; the results are displayed by the moisture content monitoring device. When the values ​​of the 4 moisture content monitoring devices are all less than 20%, the moisture content of the dredged soil in the mud receiving area meets the design requirements, and transportation construction is carried out. During the excavation process, the embedded vertical drainage device is protected, and workers are used to cooperate in excavation within 1m around the vertical drainage device; The seventh step is to reuse the vertical drainage device to carry out the next dredging and filling construction; after the dredged soil is transported, continue the filling operation in the mud receiving area, repeat the fourth to sixth steps, and complete the subsequent filling and transportation of dredged soil.

2. The construction method of a pre-buried vertical drainage device in a mud receiving area according to claim 1 is characterized in that: In the first step, the structural form of the cofferdam is designed and determined according to the height of the dredged soil in the mud receiving area. The top elevation of the cofferdam in the mud receiving area is set to +5.5m, 0.5m higher than the filling elevation. The cofferdam body is constructed with impermeable clay.

3. The construction method of a pre-buried vertical drainage device in a mud receiving area according to claim 1 is characterized in that: In the third step, the arrangement spacing and installation method of the drainage device are determined, and the vertical drainage device is arranged using a hydraulic pile driver.

4. The construction method of a pre-buried vertical drainage device in a mud receiving area according to claim 1 is characterized in that: In the fourth step, a suction dredger is used to blow the offshore dredged soil into the mud receiving area through a mud discharge pipeline.

5. The construction method of a pre-buried vertical drainage device in a mud receiving area according to claim 1 is characterized in that: In the sixth step, an excavator is used to dig the dredged soil, which is then loaded into a dump truck and transported to a designated area.

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