River channel cutter suction dredging and pit flushing backfilling integrated construction method

Abstract

The invention discloses a river channel cutter suction dredging and pit flushing backfilling integrated construction method. The method comprises the steps of preparation before construction and ship dispatching, unmanned ship underwater measurement and ship entry, cutter suction dredger consignment, cutter suction dredger positioning, pipeline laying, sewage fence lock installation, backfilling construction area measurement, dredging operation, pit flushing backfilling, construction detection and acceptance. Sediment sucked by the dredging construction area is directly conveyed to the backfilling construction area through the overwater mud discharging pipe to be backfilled, cutter suction dredging and pit flushing backfilling are synchronously carried out to achieve integrated construction, the construction efficiency is improved, equipment and personnel investment is reduced, the construction cost and safety risks are reduced, environmental pollution is reduced, and the method is suitable for popularization and application. The effects of improving river water quality and protecting water resources are obvious.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water conservancy engineering, in particular to a river channel cutter suction dredging and pit flushing backfill integrated construction method. BACKGROUND

[0002] With the rapid development of the water conservancy industry, river channel management has become the mainstream today, and for the construction work around the city, necessary river channel management work has far-reaching significance for improving the level of urban infrastructure. The river channel has been lacking effective management for a long time, resulting in serious siltation, affecting the flood carrying capacity and water quality.

[0003] Traditional shallow water channel dredging adopts earth and stone cofferdams to close the construction range for drainage, and then excavators and transport vehicles are used to clean and transport the river bottom sand, which has long construction period, low efficiency, is easy to pollute the river channel, and the construction quality is difficult to guarantee. The traditional pit flushing backfill is to transport the backfill soil / sand from the river bank to the pit flushing area by sand transport ship, and the two construction methods are independently implemented, which cannot form an organic combination, resulting in low construction efficiency and increasing construction cost.

[0004] It can be seen that the above-mentioned prior art has obvious inconvenience and defects in structure, method and use, and needs to be further improved. How to create a new river channel cutter suction dredging and pit flushing backfill integrated construction method is one of the current important research and development topics. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a river channel cutter suction dredging and pit flushing backfill integrated construction method, which directly transports the silt sucked by the dredging construction area to the backfill construction area through the mud discharge pipe laid on the water surface, improves the construction efficiency, reduces the construction cost, and overcomes the shortcomings of the prior art.

[0006] To solve the above technical problems, the present application provides a river channel cutter suction dredging and pit flushing backfill integrated construction method, and the construction steps include: Step S1: preparation before construction and ship deployment; Step S2: unmanned ship underwater measurement and ship entry point; The present river bottom elevation is measured by an unmanned ship, and a river bottom elevation triangular net map is drawn by using professional measurement software; Step S3: barge transportation of cutter suction ship; The operator drives the barge to transport the cutter suction ship to slowly enter the dredging construction area according to the predetermined route, and determines the position of the cutter suction ship by using the satellite positioning system; Step S4: cutter suction ship positioning; After the cutter suction dredger arrives at the construction site, it lowers the positioning piles and inserts them into the riverbed through a hydraulic system. After the piles are fixed, it drops anchors on the port and starboard sides with the anchor chain at a horizontal angle of 30°. The anchor chain length or the angle of the positioning piles is adjusted to ensure that the cutter suction dredger is positioned in the center of the construction area. Step S5: Perform steps S5a, S5b, and S5c simultaneously; Step S5a: Pipeline laying; A sludge discharge pipe is laid from the sludge discharge port of the cutter suction dredger to the backfill construction area. The sludge discharge pipe floats on the water surface and is laid in a smooth and continuous arc shape. Step S5b: Install the waste rail lock; Anchor the two ends of the debris barrier on both sides of the riverbank so that the debris barrier spans the river and is located above the water surface, and fix the floating tubes on the debris barrier at equal intervals. Step S5c: Measurement of the backfill construction area; Step S6: Perform steps S6a and S6b simultaneously; Step S6a: Dredging operation; Step S6b: Backfilling the ditch; Step S7: Construction inspection and acceptance.

[0007] As an improvement of the present invention, in step S5a, the sludge discharge pipe is a single PE pipe with a length of 12m and a diameter of 200mm connected end to end, and adjacent PE pipes are connected by flanges and fitted with sealing gaskets. 3.5mm foam board is tied to the sludge discharge pipe.

[0008] Furthermore, in step S5a, a positioning buoy is installed at the port of the sludge discharge pipe in the backfill construction area. The sludge discharge pipe is tied and fixed to the positioning buoy, and the positioning buoy is anchored to the riverbed by three steel cables. The three steel cables are evenly distributed circumferentially in the horizontal plane.

[0009] Furthermore, in step S5a, the sludge discharge pipe is connected to the energy dissipation pipe at the port of the backfill construction area via a flange. The energy dissipation pipe is inclined upward at 45° to the water surface. The sludge-blocking net is welded and fixed at the outlet of the energy dissipation pipe via a bracket. The sludge-blocking net is perpendicular to the energy dissipation pipe and has a distance between it and the outlet of the energy dissipation pipe.

[0010] Furthermore, in step S5, a mixing pipe is provided near the backfilling construction area of ​​the sludge discharge pipe. One end of the mixing pipe is connected to the sludge discharge pipe through a flange, and the other end is set on the riverbank for mixing fine sand into the sludge discharge pipe.

[0011] Furthermore, in step S5b, the debris barrier lock is made of high-strength, corrosion-resistant rope material, and the float is made of high-density polyethylene. Specific construction steps include: Step S5b1: Survey the downstream topography, water flow velocity, water depth and geological conditions on both banks of the river to determine the location, height and anchor installation points of the debris barrier; Step S5b2: Mark the anchor installation points on both sides of the river channel, excavate anchor pits using an excavator, place the anchors into the anchor pits, and then pour concrete to fix the anchors. Step S5b3: Secure the buoys to the debris barrier at equal intervals using locking clips, and connect one end to the anchor. Drive the workboat to the opposite bank and gradually unfold the debris barrier. Once on the opposite bank, tighten the debris barrier using a hand-operated hoist and secure it to the anchor. Step S5b4: Check the position, height, tension, buoy connection, and anchor fixing of the debris barrier.

[0012] Furthermore, in step S6a, the dredging construction area is divided into multiple construction sections along the length of the river and into multiple construction strips along the width of the river. The overlap length between adjacent construction sections and the overlap width between adjacent construction strips are both not less than 1.5 times the soil excavation thickness, and the construction trajectory of the cutter suction dredger is S-shaped.

[0013] Furthermore, in step S6a, the cutter diameter of the cutter suction dredger is 0.6-1.8m. When the dredging depth is greater than the single dredging depth of the cutter, layered construction is carried out, and the layer thickness is 0.5-1.5 times the cutter diameter and increases from bottom to top.

[0014] Furthermore, in step S6b, multiple backfilling construction points are set up within the backfilling construction area. The backfilling construction points are arranged at 50m intervals. Backfilling is stopped when the backfill soil elevation is 20mm higher than the design elevation, and the mud discharge pipe port is adjusted to the next backfilling construction point to continue backfilling.

[0015] With this design, the present invention has at least the following advantages.

[0016] 1. Dredging operations in the dredging area are carried out using cutter suction dredgers, eliminating the need for cofferdams and making construction convenient.

[0017] 2. The silt extracted from the dredging construction area is directly transported to the backfill construction area through the water discharge pipe for backfilling, realizing the integrated construction of dredging and backfilling, improving construction efficiency, reducing equipment and personnel input, and lowering construction costs and safety risks.

[0018] 3. The silt is transported through closed pipelines, and the entire construction process is carried out continuously, reducing pollution of river water resources; the silt does not need to be transported by vehicles, effectively avoiding the spillage of silt and sand, preventing road pollution, and reducing traffic pressure on the site; fewer construction equipment is required, reducing noise pollution at the construction site.

[0019] 4. Energy dissipation pipes, silt traps, and positioning pontoons are installed in the backfill construction area. The mud and sand are sprayed onto the silt traps through the energy dissipation pipes and then naturally settle into the scour pit, achieving precise backfilling at fixed points, improving the quality of backfilling construction, and making construction simple, convenient, and efficient. Attached Figure Description

[0020] The above is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Figure 1 This is a flowchart illustrating the present invention.

[0022] Figure 2 This is a schematic diagram of the layout of the dredging and backfilling construction areas.

[0023] Figure 3 This is a schematic diagram of the elevation structure of the sludge discharge pipe at the port of the backfill construction area.

[0024] Figure 4 This is a schematic diagram of the plan layout of the sludge discharge pipe at the port of the backfill construction area.

[0025] Explanation of reference numerals in the attached drawings: 1. Dredging construction area; 11. Construction section; 12. Construction strip; 2. Backfilling construction area; 21. Backfilling construction point; 3. Sludge discharge pipe; 4. Energy dissipation pipe; 5. Support frame; 6. Sludge trap net; 7. Positioning buoy; 8. Steel cable. Detailed Implementation

[0026] Please see Figures 1 to 3 This invention provides an integrated construction method for river channel dredging and backfilling of dredged pits, which is applicable to dredging work in waterways, canals, lakes and other water bodies with a water depth of more than 1.5m. It not only dredges and levels the riverbed, but also backfills the pits and trenches on the riverbed, which has a significant effect on improving the water quality of the river and protecting water resources. The specific construction steps include S1 to S7.

[0027] Step S1: Pre-construction preparations and vessel deployment.

[0028] Step S2: Underwater measurement by unmanned vessel and vessel approach.

[0029] Unmanned surface vessels were used to measure the current riverbed elevation, and professional measurement software was used to create a triangulation network diagram of the riverbed elevation.

[0030] Step S3: Transport by cutter suction dredger.

[0031] The operators piloted the barge to transport the cutter suction dredger slowly into dredging area 1 along a predetermined route, using a satellite positioning system to determine the dredging dredger's location. During the journey, they constantly monitored the river's water depth, current direction, and surrounding environment, paying close attention to any potential obstacles in the river and taking preventative measures.

[0032] Step S4: Positioning the cutter suction dredger.

[0033] After the cutter suction dredger reaches the construction location, positioning stakes are lowered and inserted into the riverbed via a hydraulic system. These positioning stakes are then driven into the riverbed by the hydraulic system, thus securing the cutter suction dredger in the construction position.

[0034] Before installing the positioning stakes, the stakes and their hydraulic system must be rigorously inspected and tested to ensure their reliable performance. When inserting the stakes, the insertion speed and depth must be carefully controlled to avoid excessive damage to the riverbed. Simultaneously, the stability of the positioning stakes should be closely monitored, and any abnormalities should be addressed promptly.

[0035] After the positioning piles are fixed, anchors are dropped on the port and starboard sides, with the anchor chains at a horizontal angle of 30°.

[0036] Before anchoring, conduct a comprehensive inspection of the anchor and anchor chain to ensure they are undamaged, free of rust, and meet strength requirements. During anchoring, strictly follow the operating procedures to avoid anchor chain tangling or excessive tension that could lead to breakage.

[0037] Adjust the anchor chain length or the angle of the positioning piles to ensure that the cutter suction dredger is positioned in the center of the construction area.

[0038] During the repositioning process, the influence of factors such as river flow and wind direction must be fully considered, and adjustments made promptly to ensure the cutter suction dredger maintains a stable position and attitude throughout the construction process. Simultaneously, attention should be paid to observing the surrounding environment to avoid collisions with other facilities. Accurate repositioning ensures the cutter suction device is in the optimal working position, guaranteeing even and thorough removal of silt from the riverbed and improving construction quality.

[0039] Step S5: Perform steps S5a, S5b, and S5c simultaneously; Step S5a: Pipeline laying; A sludge discharge pipe 3 will be laid from the sludge discharge port of the cutter suction dredger to the backfill construction area. Sludge discharge pipe 3 will consist of single 12m long, 200mm diameter PE pipes connected end-to-end. Adjacent PE pipes will be connected by flanges and sealed with gaskets. Before the pipes arrive on site, the pipe bodies should be inspected; damaged, severely rusted, or worn pipe fittings should not be used without repair. Because the floating pipes must withstand the effects of water flow, waves, and the impact of dredging construction, the connections between pipe sections must be secure and reliably sealed.

[0040] A 3.5mm foam board is tied to the sludge discharge pipe 3 to make it float on the water surface. The sludge discharge pipe 3 is laid in a smooth and continuous arc shape. During construction, the sway of the floating pipe must be strictly controlled to ensure smooth operation of the line.

[0041] The sludge discharge pipe 3 is equipped with a positioning buoy 7, an energy dissipation pipe 4, and a sludge trap 6 at the port of the backfill construction area 2.

[0042] The mud discharge pipe 3 is tied and fixed to the positioning buoy 7. The positioning buoy 7 is anchored to the riverbed by three steel cables. The three steel cables are evenly distributed in the circumference of the horizontal plane, that is, they are arranged at intervals of 120° to ensure stable positioning.

[0043] At the end of the sludge discharge pipe 3, an energy dissipation pipe 4 is connected via a flange. The energy dissipation pipe 4 is inclined upwards at a 45° angle to the water surface. At the outlet of the energy dissipation pipe 4, a sludge trap 6 is welded and fixed to it via a bracket 5. The sludge trap 6 is perpendicular to the energy dissipation pipe 4 and has a distance between it and the outlet of the energy dissipation pipe 4. During backfilling, the sludge is sprayed through the energy dissipation pipe 4 onto the sludge trap 6 and then naturally settles into the lower flushing pit, achieving precise and targeted backfilling.

[0044] It should be noted that the sludge discharge pipe 3 is equipped with an interface flange near the backfilling construction area 2 for connecting the mixing pipe. This interface flange is sealed with a blind flange when not in use. When in use, one end of the mixing pipe is connected to the sludge discharge pipe 3, and the other end is set on the riverbank. If the sludge extracted during the dredging operation in the construction area does not meet the backfilling requirements of the flushing pit, fine silt can be mixed into the sludge discharge pipe 3 from the riverbank for backfilling.

[0045] Step S5b: Install the waste lock.

[0046] Anchor the two ends of the debris barrier on both sides of the riverbank so that the debris barrier spans the river and is located above the water surface, and fix the floating tubes on the debris barrier at equal intervals.

[0047] The debris barrier lock is made of high-strength, corrosion-resistant rope material, and the float is made of high-density polyethylene. The specific construction steps include S5b1 to S5b4.

[0048] Step S5b1: Survey the downstream topography, water flow velocity, water depth and geological conditions on both banks of the river to determine the location, height and anchor installation points of the debris barrier; Step S5b2: Mark the anchor installation points on both sides of the river channel, excavate anchor pits using an excavator, place the anchors into the anchor pits, and then pour concrete to fix the anchors. Step S5b3: Secure the buoys to the debris barrier at equal intervals using locking clips, and connect one end to the anchor. Drive the workboat to the opposite bank and gradually unfold the debris barrier. Once on the opposite bank, tighten the debris barrier using a hand-operated hoist and secure it to the anchor. Step S5b4: Check the position, height, tension, buoy connection, and anchor fixing of the debris barrier.

[0049] Step S5c: Measurement of the backfill construction area.

[0050] Step S6: Perform steps S6a and S6b simultaneously.

[0051] Step S6a: Dredging operation.

[0052] Please seeFigure 2 During dredging operations, the dredging construction area 1 is divided into multiple construction sections 11 along the length of the river and multiple construction strips 12 along the width of the river. In this embodiment, there are 4 construction sections 11 and 6 construction strips 12.

[0053] The overlap length between adjacent construction sections 11 and the overlap width between adjacent construction strips 12 shall not be less than 1.5 times the soil excavation thickness to ensure that no shallow embankments are left.

[0054] When a cutter suction dredger is carrying out dredging operations, it will proceed from upstream to downstream in stages, and carry out each section one by one. The overall construction trajectory is S-shaped, and the construction should be carried out in accordance with the principle of "adjusting distant soil in the near and adjusting near soil in the far".

[0055] The cutter diameter of the cutter suction dredger is 0.6-1.8m. When the dredging depth is greater than the single dredging depth of the cutter, layered construction is carried out. The thickness of each layer is 0.5-1.5 times the cutter diameter and increases from bottom to top, that is, the construction follows the principle of "thick upper layer and thin lower layer".

[0056] Before setting up the cutter suction dredger's power system and dredging equipment, operators must conduct a comprehensive inspection of the power system to ensure that key components such as the engine and transmission are in good working order. Simultaneously, all components of the dredging equipment must be tested and adjusted, such as the cutter head connections and lubrication system, to ensure stable operation after startup.

[0057] During equipment operation, operators must closely monitor various parameters on the instrument panel, such as speed, torque, and oil temperature, to ensure these parameters are within normal ranges. If any abnormality is detected, immediately stop the machine for inspection, troubleshoot the problem, and then restart it.

[0058] During dredging operations, operators should flexibly adjust the cutting depth of the cutter according to the properties of the soil layer, with an adjustment range between 0.6 and 1.8 meters.

[0059] Different soil layers have different hardness and structure. Soft soil layers may only require smaller cutting forces and shallower cutting depths, while hard soil layers require larger cutting forces and deeper cutting depths.

[0060] When cutting through soft soil layers, the cutting depth of the cutterhead can be appropriately reduced. This prevents the cutterhead from penetrating too deeply into the soil, which would increase the dredger's energy consumption and accelerate equipment wear. At the same time, a smaller cutting depth also helps maintain the concentration and fluidity of the dredged mud, improving dredging efficiency.

[0061] When encountering hard soil layers, the cutting depth of the cutter needs to be increased accordingly. In this case, the operator needs to gradually increase the cutter's rotation speed to increase the cutting force and break up the hard soil. However, care must be taken to control the increase in rotation speed and cutting depth to avoid excessive impact and damage to the cutter and equipment.

[0062] During the cutting process, operators must constantly observe the working status and cutting effect of the cutter head. If problems such as sluggish cutter rotation, low cutting efficiency, or abnormal vibration are found, the cutter head's rotation speed and cutting depth should be adjusted promptly. Through continuous trial and adjustment, the most suitable cutting parameters for the current soil properties can be found to ensure dredging efficiency and quality.

[0063] Step S6b: Backfill the ditch.

[0064] Please see Figure 2 Multiple backfilling construction points 21 are set up in the backfilling construction area 2. The spacing of the backfilling construction points 21 is determined according to the siltation characteristics of the backfill soil and the performance of the hydraulic filling equipment. If the backfill soil is silty soil or fine sand, the spacing of the backfilling construction points 21 should be controlled at 100-150m. If the backfill soil is clay or medium-coarse sand, the spacing should be controlled at 30-60m.

[0065] In this embodiment, backfilling construction points 21 are arranged at 50m intervals. Backfilling is stopped when the backfill soil elevation is 20mm higher than the design elevation. The mud discharge pipe port is adjusted to the next backfilling construction point to continue backfilling. The 20mm higher than the design elevation is the consolidation settlement of the backfill soil.

[0066] Step S7: Construction inspection and acceptance.

[0067] This invention directly transports the silt extracted from the dredging construction area to the backfill construction area via an underwater silt discharge pipe, realizing integrated construction of cutter suction dredging and flushing pit backfilling. This improves construction efficiency, reduces equipment and personnel input, lowers construction costs and safety risks, and also reduces environmental pollution. It has a significant effect on improving river water quality and protecting water resources.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, or alterations made by those skilled in the art using the disclosed technical content shall fall within the protection scope of the present invention.

Claims

1. A method for integrated construction of riverway cutter suction dredging and pit blasting backfilling, characterized in that, The construction steps include: Step S1: preparation before construction and ship arrangement; Step S2: unmanned ship underwater measurement and ship entry point; The current river bottom elevation is measured by the unmanned ship, and a river bottom elevation triangular net map is drawn by using professional measurement software; Step S3: barge transportation of the cutter suction dredger; The operator drives the barge to slowly enter the dredging construction area along the predetermined route, and determines the position of the cutter suction dredger by using the satellite positioning system; Step S4: cutter suction dredger positioning; After the cutter suction dredger reaches the construction position, the positioning pile is lowered and inserted into the river bottom through the hydraulic system, and after the fixing is completed, the port and starboard anchors are thrown, the anchor chain horizontal angle is 30°, the anchor chain length or the positioning pile angle is adjusted to ensure that the cutter suction dredger is positioned at the center position of the construction area; Step S5: simultaneously perform steps S5a, S5b and S5c; Step S5a: pipeline laying; A sludge discharge pipe is laid from the sludge discharge port of the cutter suction dredger to the backfill construction area, the sludge discharge pipe floats on the water surface, and the overall laying is in a smooth and continuous arc shape; Step S5b: installation of the trash rack; The two ends of the trash rack are anchored on the two sides of the river bank, so that the trash rack spans the river and is located above the water surface, and the floating buoys are fixed on the trash rack at equal intervals; Step S5c: backfill construction area measurement; Step S6: simultaneously perform steps S6a and S6b; Step S6a: dredging operation; Step S6b: pit flushing and backfilling; Step S7: construction detection and acceptance.

2. The integrated construction method of riverway cutter suction dredging and pit blasting backfilling according to claim 1, characterized in that, In step S5a, the sludge discharge pipe is made of PE pipes with a single length of 12 m and a diameter of 200 mm, which are connected end to end, adjacent PE pipes are connected through flanges and equipped with sealing pads, and the sludge discharge pipe is bound with 3.5 mm foam plates.

3. The integrated construction method of riverway cutter suction dredging and pit blasting backfilling according to claim 1, characterized in that, In step S5a, positioning buoys are arranged at the ports of the backfill construction area, the sludge discharge pipe is fixed with the positioning buoys, the positioning buoys are anchored on the river bottom through three steel cables, and the three steel cables are evenly distributed in the horizontal plane.

4. The integrated construction method of riverway cutter suction dredging and pit blasting backfilling according to claim 1, characterized in that, In step S5a, the sludge discharge pipe is connected with the energy dissipation pipe through the flanges at the ports of the backfill construction area, the energy dissipation pipe is inclined upward at an angle of 45° with the water surface, the energy dissipation pipe is fixed with the support by welding at the outlet, the trash screen is perpendicular to the energy dissipation pipe and has a distance between the energy dissipation pipe outlet.

5. The integrated construction method of riverway cutter suction dredging and pit blasting backfilling according to claim 1, characterized in that, In step S5, a mixing pipe is arranged near the backfill construction area, one end of the mixing pipe is connected with the sludge discharge pipe through the flanges, and the other end is arranged on the river bank, which is used for mixing fine silt into the sludge discharge pipe.

6. The integrated construction method of riverway cutter suction dredging and pit blasting backfilling according to claim 1, characterized in that, In step S5b, the trash rack is made of high-strength corrosion-resistant rope material, and the floating buoys are made of high-density polyethylene, and the specific construction steps include: Step S5b1: survey the terrain, water flow speed, water depth and both bank geology of the river downstream to determine the position, height and anchor installation point of the trash rack; Step S5b2: mark the anchor installation point on both banks of the river, excavate the anchor pit with an excavator, and pour concrete after the anchor is placed in the anchor pit to fix the anchor; Step S5b3: fix the floating buoys on the trash rack at equal intervals by using the lock, connect one end with the anchor, drive the work boat to the opposite bank and gradually unfold the trash rack, and after reaching the opposite bank, tighten the trash rack by using the hand-operated hoist and fix it to the anchor; Step S5b4: check the position, height, tension, floating buoy connection and anchor fixing of the trash rack.

7. The integrated construction method of riverway cutter suction dredging and pit blasting backfilling according to claim 1, characterized in that, The dredging construction area in the step S6a is divided into multiple construction sections along the length direction of the river and multiple construction strips along the width direction of the river, the overlapping length between adjacent construction sections and the overlapping width between adjacent construction strips are not less than 1.5 times the thickness of the soil body to be excavated, and the construction track of the cutter suction dredger is in S shape.

8. The integrated construction method of riverway cutter suction dredging and pit blasting backfilling according to claim 1, characterized in that, The cutter diameter of the cutter suction dredger in the step S6a is 0.6-1.8 m, when the dredging depth is greater than the single excavation depth of the cutter, layered construction is performed, the layered thickness is 0.5-1.5 times the cutter diameter and increases from bottom to top.

9. The integrated construction method of riverway cutter suction dredging and pit blasting backfilling according to claim 1, characterized in that, Multiple backfill construction points are arranged in the backfill construction area in the step S6b, the backfill construction points are arranged at intervals of 50 m, backfilling is stopped when the backfill soil elevation is greater than the design elevation by 20 mm, the end of the sludge discharge pipe is adjusted to the next backfill construction point for continuous backfilling.

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