Full-rotation pore-forming stone-filling gravel pile tamping construction method

Abstract

The invention provides a full-rotation hole-forming stone-filling ramming gravel pile construction method, which belongs to the technical field of gravel pile construction, carries out a full-rotation in-hole ramming land gravel pile construction test by using existing equipment, and verifies the feasibility of the method. The technology for ramming the land gravel pile in the full-rotation hole is suitable for ultra-deep land gravel pile construction in special scenes that the site is limited in a deep riprap layer, important building structures are close to the deep riprap layer, the requirement for vibration control is high, and large equipment cannot be constructed, and more choices are provided for foundation treatment of follow-up projects. The defects that in the prior art, an original land gravel pile machine cannot directly conduct construction in a riprap layer, and large equipment such as the land gravel pile machine has high requirements for the bearing capacity of a foundation and is not suitable for coastal and near-edge operation are effectively overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of stone pile construction, and in particular relates to a full-rotation hole-forming, stone-filling, ramming and crushed stone pile construction method. Background Art

[0002] Many projects under construction are located on offshore islands and reefs. These often require the construction of new dikes, as described in the prior art solution with patent publication number "CN101289852A." These new dikes connect to the existing dike using a riprap slope embankment (including an east and west dike connection section). The west dike connection section is backfilled with quarried rock, followed by onshore gravel pile construction. Geological survey drilling results indicate that the riprap layer is 24-30 meters thick (+5.0m to -25m), containing crushed stone, large boulders, and a small amount of fine sand, with a complex stratigraphic distribution.

[0003] The onshore gravel piles in the west dike connection section are designed to have a length of 32.5m (+5.0m to -27.5m), a pile diameter of 1000mm, and a spacing of 1.95m. The design calls for a 20% replacement rate. The existing onshore gravel pile driver could not construct directly in the riprap layer (requiring an ultra-deep pilot hole). Furthermore, the construction area is narrow (67m long and 31m wide), bordered by the sea on the outside and a bagged sand cofferdam on the inside. The onshore gravel pile driver weighs 220t, and large equipment like onshore gravel pile drivers places high demands on the foundation's bearing capacity, making them unsuitable for operation near the sea or adjacent to the coast. Therefore, given the limitations of site and equipment, and in conjunction with existing construction projects and equipment at the project site, such as full-casing follow-up pilot holes and dynamic compaction gravel piers, it was crucial to test the gravel pile construction technology in this unique geological environment to demonstrate its feasibility. Summary of the Invention

[0004] In order to solve the defects in the existing technology, the present invention provides a full-rotation hole-forming, stone-filling and ramming crushed stone pile construction method, which effectively avoids the defects of the existing technology that the onshore crushed stone pile machine cannot be directly constructed in the riprap layer, the large equipment such as the onshore crushed stone pile machine has high requirements on the bearing capacity of the foundation, and is not suitable for operations near the sea or the edge.

[0005] The present invention utilizes the following technical solutions.

[0006] A full-rotation hole-forming, stone-filling, and ramming crushed stone pile construction method comprises: A full-rotation drilling rig is used to press the casing down to penetrate the riprap layer. The stones in the casing are removed by a crawler crane equipped with a mechanical grab and a rotary drilling rig. The hammer equipped with the crawler crane is used to compact the gravel backfilled in the casing in layers, thus forming the onshore gravel pile body.

[0007] Furthermore, the process flow of the full-rotation hole-forming stone-filling and ramming crushed stone pile construction method specifically includes: Step 1: Conduct hole construction; Step 2: Ramming gravel pile construction; Step 3: Ergonomic analysis.

[0008] Furthermore, step 1 specifically includes: Step 1-1: Clean and level the construction site, measure and stake out, then hoist and secure the positioning plate into place; Step 1-2: Use a crawler crane to lift the full-rotation drilling rig to the positioning plate point; Step 1-3: After the full-rotation drill is in place, hoist the casing to the full-rotation drill. Use the full-rotation drill to connect the casing sections and press them down to 0.3m above the designed bottom elevation. During the casing pressing process, use a hammer to measure the verticality of the casing. If the verticality deviation is large, adjust it to the correct verticality using the full-rotation drill in a timely manner. Steps 1-4: Use a crawler crane with a quick-release function and a mechanical grab bucket to clear the slag. For stone, use a rotary drilling rig to cut until the obstacle is cleared to the bottom elevation of the casing. Step 1-5: After the hole is cleaned, the hole depth and verticality are inspected; Step 1-6: Use a crawler crane to move the full-rotation equipment to provide a construction site for ramming gravel piles.

[0009] Furthermore, the full-rotation drilling rig includes a main clamping mechanism for clamping the casing, an auxiliary clamping mechanism for clamping the casing is arranged below the main clamping mechanism, the rotary mechanism surrounds the main clamping mechanism, a leveling cylinder is arranged on one side of the auxiliary clamping mechanism, the main clamping mechanism is connected to the clamping cylinder, a pressing and pulling mechanism connected to the leveling cylinder is arranged on one side of the clamping cylinder, a counterweight frame is arranged between the auxiliary clamping mechanism and the main clamping mechanism, and a reaction fork is connected to one side of the counterweight frame.

[0010] Furthermore, step 2 specifically includes: Step 2-1: Ramming layer thickness control; Step 2-2: Add materials and start construction; Step 2-3: compaction in layers; Step 2-4: Record the construction process.

[0011] Furthermore, in step 2-1, the calculation formula for the impact depth of the ramming hammer is as follows: Where: h is the impact depth of the rammer, unit: m; W is the weight of the rammer, unit: t; H is the drop distance of the rammer, unit: m; α is the correction coefficient of the effective reinforcement depth.

[0012] Furthermore, in step 2-2, an excavator is used to add crushed stones. The excavator bucket capacity and the weight of the crushed stones are measured in advance. The average value of the bucket capacity is taken to control the weight of the added materials. The amount of material added to each layer is the calculated amount of material added.

[0013] Furthermore, in steps 2-3, a plumb bob is used to measure the hole elevation. After confirming the gravel level, the casing is lifted 3.5 meters. During construction, ensure that 1.5 meters of gravel is left above the bottom of the casing. Each layer is rammed six times, and the rammer is raised to a height of 20 meters. The ramming volume should be recorded in detail, and the filling coefficient is calculated based on the accumulated ramming volume. After ramming the hole layer by layer to the hole mouth and removing the last section of casing, the equipment is moved to the next hole location. Repeat this process until the pile top elevation is reached.

[0014] Furthermore, in step 2-3, the filling coefficient i=actual backfill volume V1 / theoretical backfill volume V2.

[0015] Furthermore, in steps 2-4, during the tamping process, in addition to controlling the number of tamping times, the average tamping amount of the last two hits is required to be less than 10 cm. If the average tamping amount of the last two hits does not meet the requirements, the number of tamping times needs to be appropriately increased during the construction process.

[0016] Furthermore, in step 3, according to the construction statistics of the test piles, the time for the full-rotation drilling rig to lead the hole is 5 hours, and the time for layered material addition and ramming of the gravel piles is 2 hours. According to the on-site layout, two sets of full-rotation drilling rigs can be organized for flow construction, and the normal working efficiency of ramming gravel piles can reach 8 piles / effective day, which meets the on-site construction progress requirements.

[0017] Furthermore, the full-rotation hole-forming, stone-filling and ramming crushed stone pile construction method further includes: When the casing elevation exceeds the designed hole depth by 0.3m, before backfilling with gravel for the first test pile, the hole depth is measured with a measuring rope. If a small amount of mud is found in the hole, the casing is re-pressed to exceed the designed hole depth by 0.7m. After clearing the silt again, gravel is immediately backfilled and tamping construction is organized. During the construction process, the hole depth is measured and gravel is backfilled in a timely manner after the hole is cleaned. After the construction of the first gravel pile test pile was completed, the test pile was subjected to heavy dynamic probing inspection. According to the test results, the corrected number of blows in the middle area of the pile foundation was lower than the design requirements, and the local pile body quality did not meet the design requirements. The number of tamping hammers for each layer of gravel was increased to 8 blows. After the number of hammer blows was adjusted, the second gravel pile test pile was constructed and subjected to heavy dynamic probing inspection. The results must meet the design requirements.

[0018] The beneficial effects of the present invention are as follows: The present invention used existing equipment to conduct a full-rotation in-hole ramming onshore gravel pile construction test, verifying the feasibility of this method. The full-rotation in-hole ramming onshore gravel pile process is suitable for ultra-deep onshore gravel pile construction in special scenarios such as limited space in deep riprap layers, proximity to important building structures, high vibration control requirements, and inability to use large equipment for construction. This provides more options for foundation treatment in subsequent projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a specific process flow chart of the full-rotation hole-forming, stone-filling and ramming crushed stone pile construction method of the present invention.

[0020] Figure 2 It is a schematic diagram of the structure of the full-rotation drilling rig under full casing conditions in the present invention.

[0021] Figure 3 It is a curve diagram of the dynamic penetration test results of the gravel pile in the full-rotation hole-forming, stone-filling and ramming gravel pile construction method of the present invention. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of the present invention more clear, the following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely express the technical solutions of the present invention. The embodiments expressed in this application are only part of the embodiments of the present invention, not all of the embodiments. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without making creative work are all within the scope of protection of the present invention.

[0023] The invention provides a method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles, comprising: First, we need to select the hole-guiding scheme: The riprap layer in the construction area of this invention is often 24-30m thick (+5.0m to -25m). The backfill rock particle size varies, with some exceeding 100cm. Some areas of the riprap layer contain sand and gravel layers. Given the complex geology of this area, the drilling plan is analyzed as follows: (1) Pneumatic down-the-hole hammers are generally suitable for pile foundation construction with dense rock layers and a drilling depth of less than 20m. The present invention is used for backfilling rock, where the stone particles vary in size and the diameter of the gravel pile is 1000mm. There are very few pneumatic down-the-hole hammers with a diameter of 1000mm. In addition, according to the on-site pneumatic down-the-hole hammer drilling test, there are problems such as a high drill bit failure rate, low construction efficiency in the sand layer and gravel layer, and difficulty in penetrating the bottom stone layer. (2) The full-rotation drilling rig is small (5.08m long, 3.18m wide, 3.6m high) and lighter than a pneumatic down-the-hole hammer (48t total weight). Two sets of equipment can be deployed in this construction area. Pilot drilling tests have shown that the efficiency can reach 3-4 drills / day / set. During the construction process, the full casing is used, and the pilot drilling quality is good.

[0024] After comprehensively analyzing factors such as construction schedule and cost, a fully rotary drilling rig was selected for the drilling operation in the west dike connection section. This rig uses the rotation and pressure of the drill bit to drive the casing into the riprap layer. A grab bucket and rotary drilling rig then remove the slag to form the pile hole. This equipment not only occupies a small footprint, but also has the advantages of penetrating deep riprap layers and having minimal impact on the surrounding environment.

[0025] The process flow of the full-rotation hole-forming, stone-filling, and ramming crushed stone pile construction method of the present invention is as follows: The full-rotation hole-filling and ramming crushed stone pile uses a full-rotation drill to push the casing down to penetrate the riprap layer. The stone in the casing is removed by a crawler crane equipped with a mechanical grab and a rotary drilling rig. The 6t hammer equipped with the crawler crane is used to ram the crushed stone backfilled in the casing layer by layer to form the onshore crushed stone pile body. The specific process flow is shown in Figure 1 shown.

[0026] In a preferred but non-limiting embodiment of the present invention, the process flow of the full-rotation hole-forming, stone-filling and ramming crushed stone pile construction method specifically includes: Step 1: Conduct hole construction; The test of the embodiment of the present invention was conducted with a CRD2106H full-rotation drilling rig, a 90t crawler crane, an XR360 rotary drilling rig, and 70m of Ø1200 casing. The CRD2106H full-rotation drilling rig had an instantaneous rotation torque of 3505kN·m, a maximum casing downforce of 600kN, and a casing extraction force of 3760kN.

[0027] In a preferred but non-limiting embodiment of the present invention, step 1 specifically comprises: Step 1-1: Clean and level the construction site, measure and stake out, then hoist and secure the positioning plate into place; Step 1-2: Use a 90t crawler crane to hoist the full-rotation drilling rig to the positioning plate point; In a preferred but non-limiting embodiment of the present invention, Figure 2As shown, the full-rotation drilling rig includes a main clamping mechanism 4 for clamping the casing 1, an auxiliary clamping mechanism 2 for clamping the casing 1 is arranged below the main clamping mechanism 4, a rotary mechanism 3 surrounds the main clamping mechanism 4, a leveling cylinder 5 is arranged on one side of the auxiliary clamping mechanism 2, the main clamping mechanism 4 is connected to the clamping cylinder 6, a pressing and drawing mechanism 7 connected to the leveling cylinder 5 is arranged on one side of the clamping cylinder 6, a counterweight frame 8 is arranged between the auxiliary clamping mechanism 2 and the main clamping mechanism 4, and a reaction fork 9 is connected to one side of the counterweight frame 8.

[0028] Step 1-3: After the full-rotation drill is in place, hoist the Ø1200 casing to the full-rotation drill. Use the full-rotation drill to connect the casing sections and press them down to 0.3m above the designed bottom elevation. During the casing pressing process, use a hammer to measure the verticality of the casing. If the verticality deviation is large, adjust it to the correct verticality using the full-rotation drill in a timely manner. Steps 1-4: Use a crawler crane with a quick-release function and a mechanical grab bucket to clear the slag. For large-diameter rocks, use a rotary drilling rig to cut until the obstacle is cleared to the bottom elevation of the casing. Step 1-5: After the hole is cleaned, the hole depth and verticality are inspected; Step 1-6: Use a crawler crane to move the full-rotation equipment to provide a construction site for ramming gravel piles.

[0029] Step 2: Ramming gravel pile construction; In a preferred but non-limiting embodiment of the present invention, step 2 specifically comprises: Step 2-1: Ramming layer thickness control; In a preferred but non-limiting embodiment of the present invention, in step 2-1, the calculation formula for the impact depth of the ramming hammer is as follows: Where: h is the impact depth of the rammer, unit: m; W is the weight of the rammer, unit: t; H is the drop distance of the rammer, unit: m; α is the correction coefficient of the effective reinforcement depth.

[0030] The weight of the test pile hammer in the embodiment of the present invention is 6 tons, the average drop distance of the hammer is half of the hole depth, which is 20 meters, and the effective reinforcement depth correction coefficient is 0.45. The calculated influence depth of the hammer is: =4.93m According to previous construction experience, each layer should be rammed with no less than 6 hammers.

[0031] Step 2-2: Add materials and start construction; In a preferred but non-limiting embodiment of the present invention, in step 2-2, according to the above calculation, the length and width of the layered compaction are both 0.55m, the layered compaction thickness is 4.93m, the crushed stone bulk density is 1.43t / m³, and the crushed stone addition calculation for each layer is: 0.55*0.55*3.14*4.93*1.43=6.69t Use an excavator to add gravel. Measure the weight of gravel in the excavator bucket capacity in advance. Take the average value of the bucket capacity to control the added weight. The amount of material added to each layer is the calculated amount, just like the 6.69t mentioned above.

[0032] Step 2-3: compaction in layers; In a preferred but non-limiting embodiment of the present invention, in steps 2-3, a plumb bob is used to measure the hole elevation. After confirming the gravel level, the casing is lifted 3.5 meters (one section). During construction, a 1.5-meter height of gravel should be left above the bottom of the casing. Each layer should be rammed six times, and the rammer should be raised to a height of 20 meters. The ramming volume should be recorded in detail, and the filling coefficient is calculated based on the accumulated ramming volume. The casing is then rammed layer by layer to the hole mouth. After the last section of casing is removed, the equipment is moved to the next hole location. This process is repeated until the pile top elevation is reached.

[0033] In a preferred but non-limiting embodiment of the present invention, in step 2-3, the filling coefficient i=actual backfill volume V1 / theoretical backfill volume V2.

[0034] The filling coefficient is calculated based on the inner diameter of the full casing being 1100mm, the hole depth being 33.2m, the cumulative stone injected being 33.2m + 3.3m = 36.5m, and the effective gravel pile diameter being 1000mm. The filling coefficient is as follows: (36.5 × 0.55 × 0.55 × 3.14) ÷ (33.2 × 0.5 × 0.5 × 3.14) = 1.33 After calculation, the filling coefficient is greater than 1.2, which meets the design requirements.

[0035] Step 2-4: Record the construction process.

[0036] In steps 2-4, the backfill can be performed 7 times to level the ground according to the cyclic sequence of "backfill → sectioned pipe removal → hole depth measurement → heavy hammer compaction → recording cumulative sedimentation". The recorded data are shown in Table 1 below: Table 1 Construction record of rammed gravel piles In a preferred but non-limiting embodiment of the present invention, in steps 2-4, during the tamping process, in addition to controlling the number of tamping times, the average tamping amount of the last two hits is required to be less than 10 cm. If the average tamping amount of the last two hits does not meet the requirements, the number of tamping times needs to be appropriately increased during the construction process.

[0037] Step 3: Ergonomic analysis.

[0038] In a preferred but non-limiting embodiment of the present invention, in step 3, according to the statistics of the test pile construction, the time for the full-rotation drilling rig to drill the hole is about 5 hours (the drilling depth is about 20 meters), and the time for layered material addition and ramming the gravel pile to form the pile is about 2 hours. According to the on-site layout, two sets of full-rotation drilling rig equipment can be organized for flow construction, and the normal working efficiency of ramming the gravel pile can reach 8 piles / effective day, which meets the on-site construction progress requirements.

[0039] In a preferred but non-limiting embodiment of the present invention, the full-rotation hole-forming, stone-filling and ramming crushed stone pile construction method further includes: When the casing elevation exceeded the designed hole depth by 0.3m, before backfilling the first test pile with gravel, the hole depth was measured with a measuring rope. A small amount of mud gushing out of the hole was found. Therefore, the casing was re-pressed to exceed the designed hole depth by 0.7m. After clearing the silt again, gravel was immediately backfilled and tamping construction was organized. During the construction process, the hole depth should be measured and gravel backfilled in time after cleaning the hole to avoid mud gushing out from the bottom that would affect the quality of the gravel pile. After the construction of the first gravel pile test pile was completed, the test pile was subjected to heavy dynamic penetration testing. According to the test results, the corrected number of blows in the middle area of the pile foundation was lower than the design requirements (the test requirements are that the average value of N63.5 in the soft soil layer is ≥10 blows, the minimum value of N63.5 is ≥7 blows, and the number of test points within the range of 7 to 10 blows for a single pile is less than 20% of the total number of test points). The local pile body quality does not meet the design requirements. After analysis, it may be that the number of hammer blows for each layer of gravel is insufficient and the density of the gravel layer is low. Therefore, the number of hammer blows for each layer of gravel is increased to 8. After the number of hammer blows is adjusted, the second gravel pile test pile is constructed and subjected to heavy dynamic penetration testing. Figure 3 As shown, the results must meet the design requirements.

[0040] The beneficial effects of the present invention are as follows: The present invention used existing equipment to conduct a full-rotation in-hole ramming onshore gravel pile construction test, verifying the feasibility of this method. The full-rotation in-hole ramming onshore gravel pile process is suitable for ultra-deep onshore gravel pile construction in special scenarios such as limited space in deep riprap layers, proximity to important building structures, high vibration control requirements, and inability to use large equipment for construction. This provides more options for foundation treatment in subsequent projects.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not deviate from the spirit and scope of the present invention should be covered within the protection space of the claims of the present invention.

Claims

1. A method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles, characterized in that: include: A full-rotation drilling rig is used to press the casing down to penetrate the riprap layer. The stones in the casing are removed by a crawler crane equipped with a mechanical grab and a rotary drilling rig. The hammer equipped with the crawler crane is used to compact the gravel backfilled in the casing in layers, thus forming the onshore gravel pile body.

2. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 1, characterized in that: The technical process of the full-rotation hole-filling and rammed stone pile construction method specifically includes: Step 1: Conduct hole construction; Step 2: Ramming gravel pile construction; Step 3: Ergonomic analysis.

3. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 2, characterized in that: Step 1 specifically includes: Step 1-1: Clean and level the construction site, measure and stake out, then hoist and secure the positioning plate into place; Step 1-2: Use a crawler crane to lift the full-rotation drilling rig to the positioning plate point; Step 1-3: After the full-rotation drill is in place, hoist the casing to the full-rotation drill. Use the full-rotation drill to connect the casing sections and press them down to 0.3m above the designed bottom elevation. During the casing pressing process, use a hammer to measure the verticality of the casing. If the verticality deviation is large, adjust it to the correct verticality using the full-rotation drill in a timely manner. Steps 1-4: Use a crawler crane with a quick-release function and a mechanical grab bucket to clear the slag. For stone, use a rotary drilling rig to cut until the obstacle is cleared to the bottom elevation of the casing. Step 1-5: After the hole is cleaned, the hole depth and verticality are inspected; Step 1-6: Use a crawler crane to move the full-rotation equipment to provide a construction site for ramming gravel piles.

4. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 3, characterized in that: The full-rotation drilling rig includes a main clamping mechanism for clamping the casing, an auxiliary clamping mechanism for clamping the casing is arranged below the main clamping mechanism, a rotary mechanism surrounds the main clamping mechanism, a leveling cylinder is arranged on one side of the auxiliary clamping mechanism, the main clamping mechanism is connected to the clamping cylinder, a pressing and pulling mechanism connected to the leveling cylinder is arranged on one side of the clamping cylinder, a counterweight frame is arranged between the auxiliary clamping mechanism and the main clamping mechanism, and a reaction fork is connected to one side of the counterweight frame.

5. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 4, characterized in that: Step 2 specifically includes: Step 2-1: Ramming layer thickness control; Step 2-2: Add materials and start construction; Step 2-3: compaction in layers; Step 2-4: Record the construction process.

6. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 5, characterized in that: In step 2-1, the calculation formula for the impact depth of the ram is as follows: ； Where: h is the impact depth of the rammer, unit: m; W is the weight of the rammer, unit: t; H is the drop distance of the rammer, unit: m; α is the correction coefficient of the effective reinforcement depth; In step 2-2, use an excavator to add crushed stone. Measure the excavator bucket capacity and crushed stone weight in advance. Take the average bucket capacity to control the added weight. The added amount for each layer is the calculated amount. In step 2-3, use a plumb bob to measure the elevation in the hole. After confirming the height of the gravel poured, pull out the entire casing 3.5 meters. During the construction process, ensure that 1.5 meters of gravel is left above the bottom of the entire casing. The number of tamping times for each layer is 6, and the tamping hammer is lifted to a height of 20 meters. At the same time, the tamping volume should be recorded in detail, and the filling coefficient is calculated by accumulating the tamping volume. After tamping layer by layer to the hole mouth and removing the last section of the casing, move the equipment to the next hole position and repeat the above process until the pile top elevation is reached.

7. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 6, characterized in that: In step 2-3, the filling coefficient i = actual backfill volume V1 / theoretical backfill volume V2.

8. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 7, characterized in that: In steps 2-4, during the tamping process, in addition to controlling the number of tamping times, the average tamping depth of the last two hits is required to be less than 10 cm. If the average tamping depth of the last two hits does not meet the requirements, the number of tamping times needs to be appropriately increased during the construction process.

9. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 8, characterized in that: In step 3, according to the construction statistics of the test piles, the full-rotation drilling rig takes 5 hours to drill the hole, and the layered material addition and ramming of the gravel piles takes 2 hours. According to the on-site layout, two sets of full-rotation drilling rigs can be organized for continuous construction. The normal working efficiency of ramming gravel piles can reach 8 piles / effective day, which meets the on-site construction progress requirements.

10. The method for constructing fully rotary hole-forming, stone-filling and ramming crushed stone piles according to claim 9, characterized in that: The full-rotation hole-forming, stone-filling and ramming crushed stone pile construction method also includes: When the casing elevation exceeds the designed hole depth by 0.3m, before backfilling with gravel for the first test pile, the hole depth is measured with a measuring rope. If a small amount of mud is found in the hole, the casing is re-pressed to exceed the designed hole depth by 0.7m. After clearing the silt again, gravel is immediately backfilled and tamping construction is organized. During the construction process, the hole depth is measured and gravel is backfilled in a timely manner after the hole is cleaned. After the construction of the first gravel pile test pile was completed, the test pile was subjected to heavy dynamic probing inspection. According to the test results, the corrected number of blows in the middle area of the pile foundation was lower than the design requirements, and the local pile body quality did not meet the design requirements. The number of tamping hammers for each layer of gravel was increased to 8 blows. After the number of hammer blows was adjusted, the second gravel pile test pile was constructed and subjected to heavy dynamic probing inspection. The results must meet the design requirements.

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