Dynamic compaction replacement construction method for shallow layer in water

Abstract

The invention belongs to an in-water shallow layer dynamic compaction replacement construction method, which comprises the following steps of: partially digging out an in-water shallow layer weir base riverbed covering layer on the in-water shallow layer of a weir base under the condition that a cofferdam is not closed, replacing and filling stones, planting piles and carrying out dynamic compaction treatment construction, and carrying out dynamic compaction replacement construction on the in-water shallow layer covering layer, so that the construction can be carried out 8-15 months ahead of time; compared with the prior art, the method has the advantages that the construction condition of the upstream cofferdam without a dry land can be achieved, the weir foundation compaction project is simplified and convenient, the project cost is greatly reduced, and the method has a good using effect and has the advantages of saving labor and time during construction, being simple in construction, high in speed, saving materials, high in efficiency and high in practicability.

Description

TECHNICAL FIELD

[0001] The application belongs to a kind of water shallow dynamic compaction replacement construction method. BACKGROUND

[0002] Before dam construction, the upstream cofferdam is required to be closed to cut off the water flow, so that the water flow enters the diversion tunnel through the diversion open channel, and the groundwater level in the dam area is lowered to provide dry land conditions for dam construction. The entire process of cofferdam air closing takes a long time, and the surface layer is generally covered with alluvium, usually 6-10m thick, and locally up to 18-25m thick. The traditional method is to wait until the cofferdam is closed to air, then remove the surface layer (or shallow layer), usually more than 3m thick, and then fill the crushed stone, and then perform the foundation compaction and cofferdam foundation treatment construction. If so, the construction period will be delayed for 8-15 months, so under the condition that the cofferdam has not been closed to air, the upstream cofferdam has no dry land construction conditions, the underwater excavation depth is deep, and it is impossible to completely remove the surface layer; and the entire excavation of the surface layer, compaction of the cofferdam foundation and the huge cost of the project are enormous.

[0003] Therefore, it is necessary to seek a kind of shallow replacement in water covering layer, which can greatly advance the entire construction process and greatly reduce the cost, which is the current urgent task. SUMMARY

[0004] The purpose of the present application is to provide a kind of water shallow dynamic compaction replacement construction method to solve the problems raised in the above background, with the advantages of less surface layer removal, shorter construction period, good construction quality and low cost.

[0005] A kind of water shallow dynamic compaction replacement construction method, comprising the following steps: (1) change the river channel, use several diversion small channels to drain the surface water in the dynamic compaction replacement construction area, and set several water level lowering wells at the edge of the dynamic compaction replacement construction area, and use a water pump to pump out the accumulated water to lower the groundwater level in the dynamic compaction replacement construction area; (2) drill and survey the underground structure of the area in the dam area where the surface layer removal and foundation treatment construction are required, draw the underground structure map of the dam area according to the survey results, the underground structure map includes the soil layer structure from top to bottom, divided into upper, middle and lower three layers, each layer composition, range, thickness, and make a water shallow dynamic compaction replacement construction drawing according to the underground structure map, and mark each pile point in the underground loose soil layer area on the dynamic compaction replacement construction drawing; (3) collect steel reinforced concrete poles with a diameter of 25-35 cm and a length of 15-25 m, or piles, or waste poles, or waste piles; prepare pressure pile, pile driving equipment and dynamic compaction machine equipment; (4) clean the 1.5m shallow layer covering layer in the riverbed of the dynamic compaction replacement area; (5) Drill and drive piles in the dynamic compaction replacement zone of the loose soil layer according to the pile location map, ensuring that the lower end of each pile is driven vertically into the bearing layer, and the upper end of each pile is at least 1 to 1.5 m below the ground after the removal of the overburden layer and is supported by the lower end of the ground surface layer after dynamic compaction. Adjacent piles are spaced 2 m apart; no pile planting is required in the dynamic compaction replacement zone with hard rock geology. (6) After the piles are installed, a 2m thick layer of graded stone material is laid on the ground and rock geological hard dynamic compaction replacement area. The graded stone material has a particle size ≤30cm and a mud content <5%. After dynamic compaction, it serves as the foundation of the weir. (7) Dynamic compaction treatment: The dynamic compaction treatment of the retained overburden layer of the upstream cofferdam adopts a method of 2 passes of spot compaction plus 2 passes of full compaction. (a) For water treatment of shallow areas with a depth ≤6m, a 15t hammer is used. The design impact energy for spot tamping is 2250kN·m. The spacing between adjacent tamping points in the first pass is 6m, arranged in a quincunx pattern. The tamping points in the second pass are located between the tamping points in the first pass. After spot tamping, the pits are leveled with upper-grade graded stone chips. The design drop distance of the hammer for the two spot tamping passes is 15m, with 8 blows per point. For the two full tamping passes, a low-energy hammer impact energy of 1000kN·m is used. The design drop distance of the hammer for the two full tamping passes is 6.7m. The hammers of the adjacent tamping points overlap by 1 / 4 of the hammer bottom diameter, with 5 blows per point. (b) For water treatment of shallow areas with a depth > 6m, the weight of the tamping hammer is 20t. The design tamping energy for spot tamping is 4000kN·m. The spacing between the first tamping points is 5m, arranged in a quincunx pattern. The second tamping points are located between the first tamping points, with 13 blows per point. After spot tamping, the tamping pits are leveled. For full tamping, two tamping passes are performed using low-energy tamping with an energy of 1000kN·m. The design drop distance of the tamping hammer for the two full tamping passes is 6.7m. The tamping points of the full tamping passes overlap each other by 1 / 4 of the hammer bottom diameter, with 5 blows per point. (8) Vibration compaction: After the dynamic compaction is completed, vibration compaction equipment is used to vibrate and compact the soil in the compaction area.

[0006] (9) Measure the elevation of the dynamic compaction construction site, repair the sections that do not meet the design requirements, and then calculate the final average settlement of the site to meet the design requirements.

[0007] As a further description of the above technical solution: the specific steps of the dynamic compaction treatment construction are as follows: (1) Mark the location of the first compaction point and measure the site elevation; (2) The crane is in place, the hammer is placed at the tamping point, and the elevation of the top of the hammer before tamping is measured; (3) hoist the rammer to a predetermined height, open the unhooking device, the rammer is automatically dropped after unhooking, lower the hook, measure the height of the rammer top; if the rammer is found to be skewed more than 20° due to the inclination of the pit bottom, granular stone slag with a particle size of ≤30 cm should be filled into the pit in time to level with the top of the pit, and the amount of filling should be recorded; when the soft soil around the ramming point is squeezed out, it should be cleaned and transported out of the dynamic compaction treatment area in time, and after cleaning, the ramming point is paved with stone slag, and the construction continues; (4) repeat step (3) to complete the ramming of each ramming point according to the design specified number of ramming and control standards; (5) change the ramming point, repeat steps (2) to (4) to complete the ramming of each ramming point of the first pass of all points; (6) use a bulldozer to push the site of all ramming points in the first pass flat, and measure the site elevation; (7) after a specified interval, repeat steps (2) to (6) to complete the ramming of each ramming point of the second pass of all points; (8) perform the first pass of full ramming to compact the surface soil layer after passing through the second pass of all points; (9) use a bulldozer to push the site flat, and measure the site elevation after the first pass of full ramming; (10) after a specified interval, repeat steps (8) to (9) to complete the second pass of full ramming; (11) after full ramming and flattening, compact the virtual soil layer with a vibrating roller, accurately measure the site elevation, and then calculate the final average settlement of the site.

[0008] As a further description of the above technical solution: the average ramming settlement of the last two hits of the point ramming is not more than 5 cm.

[0009] As a further description of the above technical solution: the specified interval is 3 days between the two passes of point ramming.

[0010] As a further description of the above technical solution: the 2m thick graded stone slag is divided into upper, middle and lower three layers from top to bottom, the lower layer is 1m thick, the middle layer is 0.4m thick, and the upper layer is 0.6m thick; The particle size ratio of the middle graded stone slag in the lower layer is: 20-30mm : 10-20mm : 5-10mm : 0-5mm = 50% : 25% : 15% : 10%; The particle size ratio of the middle graded stone slag in the middle layer is: 20-30mm : 10-20mm : 5-10mm : 0-5mm = 30% : 30% : 20% : 20%; The particle size ratio of the upper layer of the middle graded stone slag is: 20-30mm : 10-20mm : 5-10mm : 0-5mm = 20% : 32% : 22% : 26%.

[0011] As the further description of the above technical solution: the vibration compaction is that the HD130 double steel roller compactor is used for static compaction for 3 times at a rolling speed of 1.5-1.7 km / h, then the Yz36 single steel roller compactor is directly used for strong vibration for 2 times and the YL37 rubber tire compactor is used for kneading compaction for 2 times at a rolling speed of 2.0-2.5 km / h after ensuring the flatness.

[0012] As the further description of the above technical solution: the repairing construction on the section not reaching the design requirement is that (1) the white lime is used to enclose the repairing construction section; (2) the upper graded stone slag material is filled in the section lower than the design ground elevation, and is fully rammed for 1-2 times, and is compacted by vibration roller to reach the design ground elevation; (3) the section higher than the design ground elevation is fully rammed for 1-2 times, and is compacted by vibration roller to reach the design ground elevation; (4) the section lower than the design relative density is fully rammed for 1-2 times to reach the design ground relative density.

[0013] As the further description of the above technical solution: the rammed pit punched on the same day should be backfilled in time and is flattened and compacted, when the construction site and the rammed pit are accumulated with water due to rainfall or the underground water level rising, the water must be pumped out by a small water pump and a hose in time outside the rammed area, the bottom silt is dug out, and the ramming construction can be continued after the silt is dried or filled with stone slag.

[0014] As the further description of the above technical solution: the quality detection after the dynamic compaction treatment is carried out 7 days after the construction is completed, a detection pit is set every 2000 square meters on the dynamic compaction construction site, and the in-situ dry density should be not less than 2.17 g / cm 3 Or the relative density is not less than 0.8.

[0015] As the further description of the above technical solution: the two full rammings need to be intermittent for 7 days.

[0016] The present application has the following beneficial effects: 1. The present application has the advantages of less shallow layer removal, shortened construction period, good construction quality and low cost, the upstream cofferdam foundation can be partially surface layer removed and foundation compaction treatment constructed before the cofferdam is closed, so that the construction period can be advanced by 8-15 months, the construction can be carried out under the condition that the upstream cofferdam is not dry, the surface layer does not need to be completely removed, the soil underground layer is planted with piles and the shallow layer is replaced by dynamic compaction, so that the cofferdam foundation compaction engineering is simplified and convenient, and the engineering cost is greatly reduced. Preliminary measurement shows that the construction period is shortened by 33%, the engineering cost is reduced by 25-30%, and the cofferdam foundation density treated by the method reaches the design requirement.

[0017] 2. This invention has low operating costs, convenient construction, and requires few construction personnel. The process of this invention is simple and easy to master. This invention has good usage effects and has the advantages of saving labor and effort during construction, simple construction, fast speed, saving materials, high efficiency and strong practicality. Attached Figure Description

[0018] Fig. 1 This is a schematic diagram of the geological structure of the shallow-medium layer dynamic compaction replacement zone in this invention; Fig. 2 This is a schematic diagram of the point compaction arrangement of the present invention; Fig. 3 This is a schematic diagram of the compaction arrangement of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. To facilitate understanding of the technical means, creative features, and achieved objectives and effects of the present invention, the present invention will be further elaborated below with reference to specific embodiments. However, the following embodiments are merely preferred embodiments of the present invention and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments without creative effort are all within the protection scope of the present invention. Unless otherwise specified, the construction methods in the following embodiments are conventional methods. Unless otherwise specified, the materials, devices, equipment, etc., used in the following embodiments can be obtained commercially.

[0020] Example 1: As Figs. 1 to 3 As shown, the construction site of this invention is in Northwest China. The reservoir dam site is located on the Tuantan River, a first-level tributary of the Tangxi River. The upstream cofferdam is located within the overburden layer, which is generally covered by alluvial deposits, typically 6m to 10m thick, with some areas reaching 18m to 25m in thickness. The material mainly consists of feldspar, quartz, sandstone, boulders, interbedded with pebbles and sand. Near the upstream side of the cofferdam's seepage prevention axis, the overburden thickness reaches 17m to 26m, consisting of alluvial deposits. The soil structure from top to bottom consists of three layers: the upper layer is soil and boulders, 2.8m to 6.3m thick, with some areas having an elevated structure and high permeability. Core samples are typically 10cm to 30cm in diameter, with some reaching 70cm, and contain 50% to 60% of the material; the pebble layer has a diameter of 2cm to 8cm, containing 20% ​​to 40% of the material, interbedded with gravelly sand, fine sand, and medium-coarse sand. The middle layer consists of boulders and large rock blocks, 7.3m to 12.2m thick. The lower layer consists of gravel mixed with sand or broken stones mixed with silty clay, with a thickness of 3.7m to 16.6m. It has moderate permeability and is distributed in the lower part. The gravel mixed with sand or broken stones has a particle size of 4cm to 8cm, with a small amount of 2cm to 3cm. It has good roundness, and the broken stones are angular, mixed with silty clay and fine sand.

[0021] A method for shallow underwater dynamic compaction replacement construction includes the following steps: (1) Change the river channel, make the river channel flowing through the dynamic compaction replacement construction area 2 change to at least 50 m outside the construction area, set up a 50 cm high dam 8 along the edge of the dynamic compaction replacement construction area, and use several diversion ditches to drain the surface water in the dynamic compaction replacement construction area. The accumulated water is led outside the dam 8 of the dynamic compaction replacement construction area. Several drawdown wells 6 are set up at the edge of the dynamic compaction replacement construction area, and adjacent drawdown wells are 200 m apart. The well depth is 6-10 m. The accumulated water in the well is pumped out by a water pump 7 and led outside the dynamic compaction replacement construction area 2 to lower the groundwater level in the dynamic compaction replacement construction area.

[0022] (2) The underground structure of the construction area in the dam area needs to be drilled and surveyed. The underground structure map of the dam area is drawn according to the survey results. The underground structure map includes the soil layer structure from top to bottom, which is divided into upper, middle and lower layers. The surface is 8 m below the upper layer, the middle layer is 8 m below the upper layer, and the lower layer is 15 m below the middle layer. The composition, range and thickness of each layer are determined according to the underground structure map. The shallow water dynamic compaction replacement construction drawing is prepared. The shallow water dynamic compaction replacement construction drawing includes the range of the dynamic compaction replacement construction area, the distribution state of the underground structure in the construction area, the distribution state of the underground hard rock layer 1, and the distribution state of the underground soil loose layer. The geological state is marked on the underground soil loose layer area 5 of the dynamic compaction replacement construction drawing.

[0023] (3) Collect steel reinforced concrete poles with a diameter of 25-35 cm and a length of 15-25 m, or piles, or waste poles, or waste piles; prepare pressure pile, piling equipment, dynamic compaction machine equipment; such as: excavator 2 for overburden excavation, loader 1 for stone residue filling, transport vehicle 7 for earthwork transportation, dynamic compaction construction, 15t\20t rammer for dynamic compaction machine 2, piling machine 1, etc.

[0024] (4) Clean the 1.5 m overburden layer in the riverbed shallow layer of the dynamic compaction replacement area 2; the excavated soil and stone is transported to the dam area outside the material factory.

[0025] (5) The pile planting area is located in the underground soil loose layer area 5 of the dynamic compaction replacement area 2, and the middle and lower layers are hard rock layers 1. The dynamic compaction replacement area 2 does not need to plant piles. The pile planting holes and pressure piles are drilled in the underground soil loose layer area according to the pile location map, and the lower end of each pile 4 is vertically driven into the bearing layer 3. The upper end of each pile is at least 1-1.5 m below the ground after the overburden layer is removed and is supported at the lower end of the ground layer after dynamic compaction. Adjacent piles are spaced 2 m apart. In the hard rock dynamic compaction replacement area, no pile planting is required. After the overburden layer is removed, 2 m thick graded stone residue is filled and dynamic compaction is performed.

[0026] (6) After planting piles, 2 m thick graded stone residue is filled in the pile planting area and the hard rock dynamic compaction replacement area. The particle size of the graded stone residue is ≤30 cm, and the clay content is <5%. After dynamic compaction, it serves as a weir foundation. The graded stone residue comes from the local material yard.

[0027] The 2m-thick graded stone chippings are divided into upper, middle and lower layers from top to bottom, the thickness of the lower layer of graded stone chippings 23 is 1m, the thickness of the middle layer of graded stone chippings 22 is 0.4m, and the thickness of the upper layer of graded stone chippings 21 is 0.6m; The particle size ratio of the lower layer of middle graded stone chippings is: 20-30mm: 10-20mm: 5-10mm: 0-5mm = 50%:25%:15%:10%; The particle size ratio of the middle layer of middle graded stone chippings is: 20-30mm: 10-20mm: 5-10mm: 0-5mm = 30%:30%:20%:20%; The particle size ratio of the upper layer of middle graded stone chippings is: 20-30mm: 10-20mm: 5-10mm: 0-5mm = 20%:32%:22%:26%.

[0028] (7) Dynamic compaction treatment: The dynamic compaction treatment of the remaining part of the overburden layer of the upstream cofferdam adopts 2 passes of point ramming and 2 passes of full ramming; (a) For the area with shallow layer depth ≤6m treated in water, a hammer with a weight of 15t is used, and each point is rammed for 8 times. The design ramming energy of point ramming is 2250kN·m, the first pass of ramming points 9 is arranged in a plum blossom shape with a spacing of 6m, and an interval of 3 days is required between the two passes of point ramming. The average ramming settlement of the last two strokes of point ramming is not more than 5cm, the second pass of ramming points 10 is located between the first pass of ramming points, the pit is leveled after point ramming with the upper layer of graded stone chippings, and the hammer is designed to fall by 15m for 2 passes of point ramming, each point is rammed for 8 times. Full ramming is performed for 2 passes with a low-energy ramming energy of 1000kN·m, the design falling distance of the hammer for 2 passes of full ramming is 6.7m, the full ramming points 11 are arranged with a mutual overlap of 1 / 4 of the hammer bottom diameter, each point is rammed for 5 times, and an interval of 7 days is required between the two passes of full ramming.

[0029] (b) For the area with shallow layer depth >6m treated in water, a hammer with a weight of 20t is used, and each point is rammed for 13 times. The design ramming energy of point ramming is 4000kN·m, the spacing between the first pass of ramming points is 5m, and the second pass of ramming points is arranged between the first pass of ramming points, each point is rammed for 13 times, and the pit is leveled after point ramming with the upper layer of graded stone chippings. Full ramming is performed for 2 passes with a low-energy ramming energy of 1000kN·m, the design falling distance of the hammer for 2 passes of full ramming is 6.7m, the full ramming points are arranged with a mutual overlap of 1 / 4 of the hammer bottom diameter, each point is rammed for 5 times, and an interval of 7 days is required between the two passes of full ramming.

[0030] The rammed pit should be backfilled and leveled and compacted in time when it is completed on the same day. When the construction site and the rammed pit are waterlogged due to rainfall or rising groundwater level, etc., the water must be pumped out outside the rammed area in time with a small water pump and hose, the bottom silt is excavated and dried, or filled with stone chippings before the ramming construction can continue.

[0031] (8) Vibration compaction, after the completion of dynamic compaction construction, the soil in the ramming area is compacted by vibration compaction equipment.

[0032] (9) Measure the elevation of the dynamic compaction construction site, and the quality detection after the dynamic compaction treatment is carried out 7 days after the completion of the construction. A detection point is set every 2000 square meters in the dynamic compaction replacement construction site to detect the in-situ dry density, which should not be less than 2.17 g / cm 3 or the relative density should not be less than 0.8. The sections that do not meet the design requirements are repaired, and the final average settlement of the site is calculated to meet the design requirements.

[0033] The steps for dynamic compaction treatment are as follows: (1) Mark the position of the first pass ramming point, and measure the elevation of the site; (2) The crane is in place, the rammer is placed at the ramming point, and the elevation of the rammer top before ramming is measured; (3) The rammer is lifted to the predetermined height, the unhooking device is opened, the rammer is automatically dropped after unhooking, the hook is lowered, and the elevation of the rammer top is measured. If it is found that the rammer is tilted more than 20° due to the inclination of the pit bottom, the pit should be filled with graded stone materials with a particle size of ≤30 cm to the same level as the top of the pit, and the amount of filling is recorded. When the soft soil around the ramming point is squeezed out, it should be cleaned and transported out of the dynamic compaction treatment area in time, and the stone material is laid around the cleaned ramming point before continuing the construction; (4) Repeat step (3) to complete the ramming of one ramming point according to the design specified number of ramming times and control standards; (5) Change the ramming point, repeat steps (2) to (4), and complete the ramming of each ramming point of the first pass of all points; (6) Use the bulldozer to push the site of the first pass of all ramming points flat, and measure the elevation of the site; (7) After the specified interval, i.e. 3 days between two passes of point ramming, repeat steps (2) to (6) to complete the ramming of each ramming point of the second pass of all points; (8) Perform the first pass of full ramming to compact the surface soil layer after passing through the second pass of all ramming points; (9) Use the bulldozer to push the site flat, and measure the elevation of the site after the first pass of full ramming; (10) After the specified interval, i.e. 7 days between two full rammings, repeat steps (8) to (9) to complete the second pass of full ramming; (11) After full ramming and leveling, compact the loose soil layer with a vibrating roller, and accurately measure the elevation of the site to calculate the final average settlement of the site. Vibration compaction is first carried out by static compaction with an HD130 double steel wheel roller for 3 passes at a rolling speed of 1.5-1.7 km / h to ensure flatness, and then directly carried out by strong vibration with a Yz36 single steel wheel roller for 2 passes and kneading compaction with a YL37 rubber tire roller for 2 passes at a rolling speed of 2.0-2.5 km / h.

[0034] The patch construction for the section not reaching the design requirement is: (1) the section is circled with white lime; (2) the section lower than the design ground elevation is filled with upper graded stone slag material, and is compacted by 1-2 times of ramming and vibration rolling to reach the design ground elevation; (3) the section higher than the design ground elevation is compacted by 1-2 times of ramming and vibration rolling to reach the design ground elevation; and (4) the section lower than the design relative density is compacted by 1-2 times of ramming to reach the design ground relative density.

[0035] The test data of the method of the embodiment of the present application and the conventional method are as follows: (1) the test conditions are the same. Table 1 (2). Table 1 shows that each index of the embodiment of the present application is better than each index of the conventional method, the surface cleaning cost of the present application is reduced by 50% per cubic meter, the compaction treatment cost is reduced by 4 times per square meter, the construction period is reduced by 25 days, the construction is advanced by 8-15 months, the present application has better compaction effect, and has the advantages of saving labor and material, simple construction, fast speed, high efficiency, strong practicability and the like.

[0036] The above is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this, any skilled person in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for shallow underwater dynamic compaction replacement construction, characterized in that, Includes the following steps: (1) Divert the river channel and use several diversion channels to drain the surface water in the dynamic compaction replacement construction area. Set up several water level lowering wells at the edge of the dynamic compaction replacement construction area and use pumps to pump out the water inside to lower the groundwater level in the dynamic compaction replacement construction area. (2) Conduct borehole surveys on the underground composition of the construction area where surface layer removal and foundation treatment are required in the dam area, and draw underground structure map of the dam area based on the survey results. The underground structure map includes the soil structure from top to bottom, divided into upper, middle and lower layers, the composition, range and thickness of each layer, and formulate the underwater shallow layer dynamic compaction replacement construction map based on the underground structure map. Mark each pile point in the underground loose soil layer area on the dynamic compaction replacement construction map. (3) Collect reinforced concrete poles or piles with a diameter of 25-35cm and a length of 15-25m, or scrap poles or scrap piles. Scrap poles or scrap piles should be free of transverse cross-sectional cracks. Prepare pile driving equipment and dynamic compaction equipment. (4) Clear 1.5m of shallow overburden layer from the riverbed within the dynamic compaction replacement zone; (5) According to the pile location map, drive pile holes and drive piles in the dynamic compaction replacement area of ​​the loose soil layer, ensuring that the lower end of each pile is driven vertically into the bearing layer, and the upper end of each pile is at least 1 to 1.5m below the ground after the removal of the overburden layer and supported on the lower end of the ground surface layer after dynamic compaction. Adjacent piles are spaced 2m apart; no pile planting is required in the dynamic compaction replacement area with hard rock geology. (6) After the piles are installed, a 2m thick layer of graded stone material is laid on the ground and rock geological hard dynamic compaction replacement area. The graded stone material has a particle size ≤30cm and a mud content <5%. After dynamic compaction, it serves as the foundation of the weir. (7) Dynamic compaction treatment: The dynamic compaction treatment of the retained overburden layer of the upstream cofferdam adopts a method of 2 passes of spot compaction plus 2 passes of full compaction. (a) For water treatment of shallow areas with a depth ≤6m, a 15t hammer is used. The design impact energy for spot tamping is 2250kN·m. The spacing between adjacent tamping points in the first pass is 6m, arranged in a quincunx pattern. The tamping points in the second pass are located between the tamping points in the first pass. After spot tamping, the pits are leveled with upper-grade graded stone chips. The design drop distance of the hammer for the two spot tamping passes is 15m, with 8 blows per point. For the two full tamping passes, a low-energy hammer impact energy of 1000kN·m is used. The design drop distance of the hammer for the two full tamping passes is 6.7m. The hammers of the adjacent tamping points overlap by 1 / 4 of the hammer bottom diameter, with 5 blows per point. (b) For water treatment of shallow areas with a depth > 6m, the weight of the tamping hammer is 20t. The design tamping energy for spot tamping is 4000kN·m. The spacing between the first tamping points is 5m, arranged in a quincunx pattern. The second tamping points are located between the first tamping points, with 13 blows per point. After spot tamping, the tamping pits are leveled. For full tamping, two tamping passes are performed using low-energy tamping with an energy of 1000kN·m. The design drop distance of the tamping hammer for the two full tamping passes is 6.7m. The tamping points of the full tamping passes overlap each other by 1 / 4 of the hammer bottom diameter, with 5 blows per point. (8) Vibratory compaction: After the dynamic compaction is completed, vibratory compaction equipment is used to compact the soil in the compaction area. (9) Measure the elevation of the dynamic compaction construction site, repair the sections that do not meet the design requirements, and then calculate the final average settlement of the site to meet the design requirements.

2. The method according to claim 1, characterized in that: The specific steps of the dynamic compaction treatment construction are as follows: (1) Mark the location of the first compaction point and measure the elevation of the site; (2) The crane is in place, the hammer is placed at the tamping point, and the elevation of the top of the hammer before tamping is measured; (3) Lift the hammer to the predetermined height, activate the unhooking device, the hammer will automatically fall after being unhooked, lower the hook, and measure the top elevation of the hammer; If the tamping hammer is found to be tilted by more than 20° due to the inclination of the pit bottom, graded stone chips with a particle size ≤30cm should be used to fill the pit until it is level with the top of the pit, and the amount of filling should be recorded. When soft soil is squeezed out around the tamping point, it should be cleaned up and transported out of the dynamic compaction treatment area at any time. After cleaning, stone chips should be laid around the tamping point before continuing construction. (4) Repeat step (3) to complete the tamping of one tamping point according to the number of tamping blows and control standards specified in the design; (5) Change the tamping point and repeat steps (2) to (4) to complete the first round of tamping of all tamping points; (6) Use a bulldozer to level the site of all the compaction points in the first pass and measure the site elevation; (7) After the specified interval, repeat steps (2) to (6) to complete the second round of compaction of all compaction points; (8) Conduct the first full compaction to compact the loose soil on the surface of the site that has been compacted twice. (9) Level the site with a bulldozer and measure the elevation of the site after the first full compaction. (10) After the specified interval, repeat steps (8) to (9) to complete the second full compaction; (11) After full compaction and leveling, use a vibratory roller to compact the loose soil layer, accurately measure the site elevation, and then calculate the final average settlement of the site.

3. The method according to claim 1 or 2, characterized in that: The average settlement of the last two blows of the point tamping is no more than 5cm.

4. The method according to claim 2, characterized in that: The specified interval is 3 days between two rounds of compaction.

5. The method according to claim 1, characterized in that: The 2m thick layer of graded stone aggregate is divided into three layers from top to bottom: the bottom layer is 1m thick, the middle layer is 0.4m thick, and the top layer is 0.6m thick. The particle size ratio of the lower layer of medium-graded stone chips is: 20-30mm: 10-20mm: 5-10mm: 0-5mm = 50%: 25%: 15%: 10%; The particle size ratio of the intermediate-layer medium-grade aggregate is: 20-30mm: 10-20mm: 5-10mm: 0-5mm = 30%: 30%: 20%: 20%; The particle size ratio of the upper intermediate grade stone chips is: 20~30mm:10~20mm:5~10mm:0~5mm=20%:32%:22%:26%.

6. The method according to claim 1, characterized in that: The aforementioned vibratory compaction involves first using an HD130 double-drum roller to statically compact three times at a speed of 1.5–1.7 km / h to ensure smoothness, then directly using a Yz36 single-drum roller for strong vibration twice and a YL37 rubber-tired roller for kneading twice at a speed of 2.0–2.5 km / h.

7. The method according to claim 1, characterized in that: The repair work for sections that do not meet the design requirements is as follows: (1) Use lime to delineate the repair work area; (2) Fill the section that is lower than the design ground elevation with the upper layer of graded stone material, compact it 1-2 times, and then compact it with a vibratory roller to reach the design ground elevation; (3) For sections that are higher than the design ground elevation, compact it 1-2 times and then compact it with a vibratory roller to reach the design ground elevation; (4) For sections that are lower than the design relative density, compact it 1-2 times to reach the design relative density.

8. The method according to claim 1 or 2, characterized in that: The ramming pits completed on the same day should be backfilled in time, leveled and compacted. When water accumulates in the construction site and ramming pits due to rainfall or rising groundwater levels, the water must be pumped out of the ramming area in time using a small water pump and hose. The silt at the bottom of the pit should be dug out and allowed to dry or filled with stone chips before ramming can continue.

9. The method according to claim 1, characterized in that: The quality inspection after dynamic compaction is carried out 7 days after construction. One test pit is set up for every 2000㎡ of the dynamic compaction replacement construction site, and the in-situ dry density should be no less than 2.17g / cm³. 3 Or a relative density of not less than 0.

8.

10. The method according to claim 1 or 2, characterized in that: A 7-day interval is required between the two full compaction operations.

Images