Hole-forming construction method for super-thick backfill complex geological cast-in-place pile

Abstract

The invention discloses an ultra-thick backfill complex geological cast-in-place pile hole forming construction method, and particularly relates to the technical field of foundation pile foundation construction, and the method comprises the steps of S1, site leveling and pile position paying off, S2, 1.2 m drill bit rotary digging hole forming, S3, backfill tamping, S4, 1 m drill bit rotary digging pile machine hole forming, S5, hole cleaning, S6, reinforcement cage manufacturing and mounting, S7, guide pipe placing, S8, secondary hole cleaning and S9, pile body concrete pouring. According to the method, the super-thick backfill complex geology in-situ SDDC in-hole deep dynamic compaction and rotary excavating pile hole-forming construction technology is adopted, in a high-position backfill area, the SDDC in-hole deep dynamic compaction technology is used for forming a pile body cylindrical soil body with the diameter being 2-3 m and easy to form a hole in an original pile position, then the rotary excavating technology is used for forming a hole in a cylinder, the hole-forming quality of a pile foundation under the complex geology condition is guaranteed, and the construction efficiency is improved. The most suitable mechanical equipment can be reasonably selected for pile foundation equipment according to specific geological conditions, the construction cost can be reduced through the combined construction technology, and the pile foundation hole forming construction quality is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of base pile foundation construction, and more specifically to a method for constructing a hole for an ultra-thick backfilled complex geological cast-in-place pile. Background Art

[0002] In the field of construction engineering, especially in foundation engineering construction, bored piles, as a commonly used foundation treatment technology, are widely used in foundation reinforcement under various geological conditions. However, when faced with ultra-thick backfill and complex geological conditions, traditional bored pile construction methods often face many challenges.

[0003] 1. The geological characteristics of the ultra-thick backfill layer are complex and changeable. The soil layer may contain a large amount of impurities and unstable factors, such as stones, garbage, and soft soil layers, which will have an adverse effect on the bored pile construction. Traditional construction methods are often difficult to effectively cope with these complex geological conditions, resulting in unstable hole quality, and even possible problems such as hole collapse and deviation. 2. Cast-in-place pile construction under complex geological conditions has extremely high requirements for equipment and technology. When dealing with ultra-thick backfill layers, traditional drilling equipment and technology often have problems such as slow drilling speed, low hole-making efficiency, and difficult verticality control. These problems not only extend the construction period and increase construction costs, but may also pose a potential threat to project quality; 3. In the context of environmental protection and sustainable development, traditional cast-in-place pile construction methods still have problems such as waste of resources and environmental pollution. For example, the mud and drilling slag generated during the drilling process are often difficult to be effectively treated and utilized, which not only wastes resources but also may cause pollution to the surrounding environment.

[0004] In view of the above situation, the present invention provides a method for constructing a super-thick backfilled bored pile in complex geology. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for constructing a super-thick backfilled complicated geological cast-in-place pile hole to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for constructing a super-thick backfilled complex geological cast-in-place pile hole, the construction method comprising the following steps: S1. Site leveling and pile position layout. Use an excavator to level the site before construction, reserve a 200mm thick soil layer and manually level it to ≦±10cm. Use a GPS measuring instrument to determine the engineering pile control point according to the coordinate control point. After verification, use a steel ruler to determine the pile position and group and number it. The point error is ≤2cm. Use a φ20mm steel drill to drill a 30-40cm deep hole and fill it with lime powder for marking. Keep a record of the layout. After acceptance, start rotary drilling; S2, 1.2m drill bit rotary drilling hole, rotary drilling machine leading hole, frame vertical, drill rod aligned with the center point of the pile hole, drilling sequence from east to west, from south to north, alternate rows, alternate intervals, until the excavation to the middle weathered layer of mudstone, soil layer excavated and transported out in time; S3. Backfill and compact. When a hole collapses during excavation, fill the hole with impurity-free silty clay in layers to the floor of the site. The layer thickness is ≤4m. Use a 1m diameter and 10t heavy hammer to compact the hole. Aim at the center of the hole during the compaction. Ensure that the machine body is stable, the gantry brace is firm, the hammer height is sufficient, and the drop distance and number of blows meet the design process. Each time the filling is carried out according to the process requirements to ensure that the pile soil is uniform and dense; S4, 1m drill bit rotary pile driver to drill holes, according to the pile point by rotary drilling rig to ensure that the verticality of the hole, pile position, hole diameter meet the design requirements, rotary drilling into the rock layer 3m, rotary drilling soil after rotary drilling timely transport, transportation distance 10km; S5. Hole cleaning: When the rotary drilling rig reaches the designed depth, clean the hole in time. Use a cylindrical drill with a valve to clean the sediment. The sediment should be ≤50mm after hole cleaning. After hole cleaning, check the hole diameter, hole depth and verticality. If qualified, remove the drilling rig and cover the cover plate. S6. Fabrication and installation of steel cage. The steel cage shall be processed according to the design. The main reinforcement position shall be controlled by steel positioning brackets to divide the distance equally. The allowable deviation of the main reinforcement spacing is ±10mm. The allowable deviation of the stirrup or spiral reinforcement pitch is ±20mm. The allowable deviation of the steel cage diameter is ±10mm. The allowable deviation of the steel cage length is ±50mm. Stiffening hoops are added every 2m. The longitudinal steel bars are overlapped on one side with a lap length of ≥10d. The joints are staggered by no less than 35d. The number of joints in the same section is ≤50%. Deformation shall be prevented during transportation and hoisting. Before placement, check the situation in the hole, align the hole position, and lower it slowly and straightly to avoid collision with the hole wall. S7. Place the conduit. After the steel cage is placed, measure the thickness of the sediment. When the sediment thickness is ≤5cm, install the concrete conduit. The inner diameter of the conduit is 300mm. Connect with screws. Check the appearance of the conduit. Calculate the required length according to the casing top elevation and the hole bottom elevation. Try to assemble and number the conduit. Use a crane to cooperate with manual installation. Make the conduit in the center of the steel cage. Sink it steadily. Keep the bottom of the conduit 40cm away from the bottom of the hole. Clamp the conduit with a chuck. S8, Secondary hole cleaning: After the catheter is placed, the thickness of the mud and sediment at the bottom of the hole is tested. If it does not meet the requirements, the reverse circulation hole cleaning process is carried out. After the thickness of the sediment at the bottom of the hole is less than 5cm, the mud density is reduced to less than 1.15 and then the hole cleaning is stopped. The interval between the completion of hole cleaning and the pouring of concrete shall not exceed 45 minutes. The mud density within 500mm of the bottom of the hole before pouring concrete shall be less than 1.20; S9. Pour the concrete for the pile body. Clean the hole before pouring. The hole wall and bottom should be clean and free of scum and looseness. If there is groundwater and the seepage volume is not large, pump out the accumulated water. Pour with the conduit method. The end of the conduit should be ≤1.5m away from the bottom of the hole. The concrete should be vibrated with an inserted vibrator and vibrated once every 1.5m of pouring. Pour continuously and vibrate to make it dense. The filling coefficient should be >1. The pouring should exceed the designed pile top elevation by 500mm. The concrete strength grade should be C30, the slump should be 160 - 180mm, the initial setting time should be ≥ 45min and ≤2h, the final setting time should be ≤6h, the pouring time should be (10m³) / 30min, the height of the casing submerged during pouring should be ≤3m, and the pipe should be pulled out at a rate of 1m / 6min after pouring to the pipe pulling height. The filling coefficient of the pile concrete test pile should be 1.2 - 1.35, and the expansion depth of the expansion head at the bottom of the pile into the rock should be 3m of the pile into the rock.

[0007] Preferably, in step S3, the tamping parameters of the tamping hammer are: 6 hammers, drop distance ≥ 8m, average settlement of the last two hammers ≤ 5cm, and real-time monitoring of the displacement of the soil around the hole during the tamping process. If the displacement rate exceeds 10mm / min, the tamping is suspended and reinforcement measures are taken.

[0008] Preferably, in step S3, the water content of the impurity-free silty clay is controlled at 18% - 22%.

[0009] Preferably, in step S2, during the process of rotary drilling of the hole by the 1.2 m drill bit, the verticality of the hole is checked every 2 m of drilling, and if the verticality deviation exceeds 1 / 100, the drill rod angle is adjusted in time.

[0010] Preferably, in step S8, the reverse circulation hole cleaning process comprises the following specific steps: Seal and connect the high-pressure pipe of the mud pump and the injection conduit, turn on the mud pump, and let the mud enter the bottom of the borehole from the mud pool through the injection conduit. Under the action of the mud pump, the mud at the bottom of the hole carries the drilling cuttings and flows upward through the injection conduit and returns to the mud pool on the ground. In the mud pool, the drilling cuttings are separated through sedimentation, filtration and other treatment methods. The purified mud can be recycled again. The mud circulation flow rate is controlled between 100-150m³ / h.

[0011] Preferably, in step S6, the main reinforcement of the reinforcement cage is HRB400 grade reinforcement.

[0012] Preferably, in step S9, when pouring the pile body concrete, a funnel is arranged on the top of the conduit, and the funnel capacity is not less than 1m³.

[0013] Preferably, after the bored pile construction is completed, the settlement of the soil around the pile is observed, and the observation period is ≥ 3 months. If the settlement exceeds 10 mm, the pile foundation is reinforced.

[0014] Technical effects and advantages of the present invention: 1. The present invention changes the single construction process used in the past for bored piles, and innovatively adopts the ultra-thick backfill complex geological in-situ SDDC hole deep tamping plus rotary drilling pile hole construction technology. In the high-position backfill area, the SDDC hole deep tamping technology is used to form a 2-3m diameter easy-to-drill pile body cylindrical soil body at the original pile position, and then the rotary drilling process is used to drill holes in the cylinder to ensure the quality of pile foundation drilling under complex geological conditions. The pile foundation equipment can reasonably select the most suitable mechanical equipment according to the specific geological conditions. By combining the construction process, the project cost can be reduced and the quality of pile foundation drilling construction can be ensured; 2. The construction process of the present invention brings into play the comprehensive effect of the combined construction process of deep tamping and rotary drilling pile drilling in the in-situ SDDC hole of ultra-thick backfill with complex geology. The research and application of this technology solves the problem of difficult pile drilling in high backfill areas, reduces engineering costs, has good social and economic benefits, provides reference and reference for similar projects, and has great promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the overall flow chart of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention provides a method for constructing a super-thick backfilled cast-in-place pile hole in complex geology, and the method specifically comprises the following steps: S1. Site leveling and pile position layout. Before construction, first use an excavator to perform preliminary leveling on the entire site to ensure that the site is roughly flat. Reserve a soil layer of about 200mm thick for subsequent manual fine leveling. The manual leveling reserves the soil layer to an error range of ≦±10cm. According to the coordinate control points provided by the project, use a GPS measuring instrument to accurately determine the control points of the project piles. Review the determined control points to ensure that they are correct. Use a steel ruler to determine the pile positions, group and number the pile positions, and control the position error to ≤2cm. Use a φ20mm steel drill to drill holes at the pile positions with a depth of 30-40cm. Fill with white lime powder for marking, and keep record of the layout. After acceptance, start rotary drilling operations; S2. Use a 1.2m drill bit to drill holes. Use a rotary drilling machine to guide the hole. Ensure that the frame is vertical and the drill rod is aligned with the center point of the pile hole. The drilling sequence is from east to west and from south to north. Alternate rows and columns are drilled at intervals to reduce the impact on adjacent pile holes. During the rotary drilling process, the verticality of the hole is checked every 2m. If the verticality deviation exceeds 1 / 100, the drill rod angle is adjusted in time to ensure that the hole is vertical until the middle weathered layer of mudstone is excavated. After the soil layer is excavated, it is transported to the designated location in time; S3, backfill and compaction. When a hole collapses during excavation, stop excavation immediately and use impurity-free silty clay for layered backfilling. The layer thickness is controlled to be ≤4m. After each layer is backfilled, use a 1m diameter and 10t heavy hammer for compaction. The compaction parameters are set as follows: 6 hammer strikes, drop distance ≥8m, and the average settlement of the last two strikes ≤5cm. During the compaction process, the displacement of the soil around the hole is monitored in real time. If the displacement rate exceeds 10mm / min, stop the compaction and take reinforcement measures. The moisture content of the impurity-free silty clay is controlled at 18%-22% to ensure the compaction effect. S4, 1m drill bit rotary drilling pile driver drilling, according to the location of the pile point, use the 1m drill bit rotary drilling rig to dig holes. During the digging process, ensure that the verticality of the hole body, the pile position, and the hole diameter meet the design requirements. Rotary drilling goes 3m into the rock layer, and the soil is promptly transported to the designated location 10km away from the construction site after rotary drilling; S5. Hole cleaning: After the rotary drilling rig reaches the designed depth, clean the hole in time and use a cylindrical drill with a valve to clean the sediment to ensure that the sediment is ≤50mm after cleaning. After cleaning, check the hole diameter, hole depth and verticality. After ensuring that they meet the design requirements, remove the drilling rig and cover the cover; S6. Fabrication and installation of steel cage. The steel cage is processed and manufactured according to the design requirements. The main reinforcement adopts HRB400 grade steel bars. The main reinforcement position is controlled by steel bar positioning brackets to divide the distance equally. The allowable deviation of the main reinforcement spacing is ±10mm, the allowable deviation of the stirrup or spiral reinforcement pitch is ±20mm, the allowable deviation of the steel cage diameter is ±10mm, and the allowable deviation of the steel cage length is ±50mm. A stiffening hoop is set every 2m. The longitudinal steel bars are single-sided lap welded, the lap length is ≥10d, the joints are staggered not less than 35d, and the number of joints in the same section is ≤50%. Prevent the steel cage from deforming during transportation and lifting. Check the hole before placement to ensure that there is no debris in the hole and the hole wall is stable. After aligning the hole position, hold the steel cage steady, slowly and straightly to avoid collision with the hole wall. S7. Place the conduit. After the steel cage is placed, measure the thickness of the sediment to ensure that the thickness of the sediment is ≤5cm. Install the concrete conduit with an inner diameter of 300mm. Use screws to connect. Check the appearance of the conduit to ensure that there is no damage or deformation. Calculate the required conduit length based on the casing top elevation and the hole bottom elevation, and conduct trial assembly and numbering. Use a crane to cooperate with manual installation of the conduit to ensure that the conduit is in the center of the steel cage. Sink steadily and control the bottom of the conduit to be 40cm from the bottom of the hole. Use a chuck to clamp the conduit. S8. Secondary hole cleaning: After the catheter is placed, the thickness of the mud and sediment at the bottom of the hole is tested again. If it does not meet the requirements, the reverse circulation hole cleaning process is used for hole cleaning. The specific steps of the reverse circulation hole cleaning process are: the high-pressure pipe of the mud pump and the injection catheter are sealed and connected, the mud pump is turned on, and the mud enters the bottom of the borehole from the mud pool through the injection catheter, and returns to the ground mud pool with the drilling cuttings. The drilling cuttings are separated in the mud pool by sedimentation, filtration and other treatment methods. The purified mud can be recycled again. The mud circulation flow rate is controlled between 100-150m³ / h. When the thickness of the sediment at the bottom of the hole is less than 5cm and the mud specific gravity is less than 1.15, the hole cleaning is stopped. The interval between the completion of hole cleaning and the pouring of concrete shall not exceed 45min. S9. Pour the concrete for the pile body. Clean the hole again before pouring to ensure that the hole wall and bottom are clean and free of scum and looseness. If there is groundwater and the seepage is not large, remove the accumulated water and use the conduit method for pouring. The end of the conduit should be ≤1.5m away from the bottom of the hole. The concrete should be vibrated with an inserted vibrator and vibrated once every 1.5m of pouring to ensure continuous pouring and compaction. The filling coefficient is greater than 1. The pouring exceeds the designed pile top elevation by 500mm. The concrete strength grade is C30 and the slump is controlled at 1. 60-180mm, initial setting time ≥45min and ≤2h, final setting time ≤6h, pouring time controlled within each truck (10m³) / 30min, submerged casing height ≤3m during pouring, after pouring to the pipe pulling height, pipe pulling at a speed of 1m / 6min, pile concrete filling coefficient test pile is 1.2-1.35, the expansion depth of the pile bottom into the rock expansion head is 3m of the pile into the rock depth, a funnel is set at the top of the guide tube, and the funnel capacity is not less than 1m³; S10. Post-observation and reinforcement: After the bored pile construction is completed, the settlement of the soil around the pile is observed. The observation period is ≥ 3 months. If the settlement exceeds 10 mm, the pile foundation is reinforced.

[0018] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for constructing super-thick backfilled bored piles in complex geology, characterized by: The construction method comprises the following steps: S1. Site leveling and pile position layout. Use an excavator to level the site before construction, reserve a 200mm thick soil layer and manually level it to ≦±10cm. Use a GPS measuring instrument to determine the engineering pile control point according to the coordinate control point. After verification, use a steel ruler to determine the pile position and group and number it. The point error is ≤2cm. Use a φ20mm steel drill to drill a 30-40cm deep hole and fill it with lime powder for marking. Keep a record of the layout. After acceptance, start rotary drilling; S2, 1.2m drill bit rotary drilling hole, rotary drilling machine leading hole, frame vertical, drill rod aligned with the center point of the pile hole, drilling sequence from east to west, from south to north, alternate rows, alternate intervals, until the excavation to the middle weathered layer of mudstone, soil layer excavated and transported out in time; S3. Backfill and compact. When a hole collapses during excavation, fill the hole with impurity-free silty clay in layers to the floor of the site. The layer thickness is ≤4m. Use a 1m diameter and 10t heavy hammer to compact the hole. Aim at the center of the hole during the compaction. Ensure that the machine body is stable, the gantry brace is firm, the hammer height is sufficient, and the drop distance and number of blows meet the design process. Each time the filling is carried out according to the process requirements to ensure that the pile soil is uniform and dense; S4, 1m drill bit rotary pile driver to drill holes, according to the pile point by rotary drilling rig to ensure that the verticality of the hole, pile position, hole diameter meet the design requirements, rotary drilling into the rock layer 3m, rotary drilling soil after rotary drilling timely transport, transportation distance 10km; S5. Hole cleaning: When the rotary drilling rig reaches the designed depth, clean the hole in time. Use a cylindrical drill with a valve to clean the sediment. The sediment should be ≤50mm after hole cleaning. After hole cleaning, check the hole diameter, hole depth and verticality. If qualified, remove the drilling rig and cover the cover plate. S6. Fabrication and installation of steel cage. The steel cage shall be processed according to the design. The main reinforcement position shall be controlled by steel positioning brackets to divide the distance equally. The allowable deviation of the main reinforcement spacing is ±10mm. The allowable deviation of the stirrup or spiral reinforcement pitch is ±20mm. The allowable deviation of the steel cage diameter is ±10mm. The allowable deviation of the steel cage length is ±50mm. Stiffening hoops are added every 2m. The longitudinal steel bars are overlapped on one side with a lap length of ≥10d. The joints are staggered by no less than 35d. The number of joints in the same section is ≤50%. Deformation shall be prevented during transportation and hoisting. Before placement, check the situation in the hole, align the hole position, and lower it slowly and straightly to avoid collision with the hole wall. S7. Place the conduit. After the steel cage is placed, measure the thickness of the sediment. When the sediment thickness is ≤5cm, install the concrete conduit. The inner diameter of the conduit is 300mm. Connect with screws. Check the appearance of the conduit. Calculate the required length according to the casing top elevation and the hole bottom elevation. Try to assemble and number the conduit. Use a crane to cooperate with manual installation. Make the conduit in the center of the steel cage. Sink it steadily. Keep the bottom of the conduit 40cm away from the bottom of the hole. Clamp the conduit with a chuck. S8, Secondary hole cleaning: After the catheter is placed, the thickness of the mud and sediment at the bottom of the hole is tested. If it does not meet the requirements, the reverse circulation hole cleaning process is carried out. After the thickness of the sediment at the bottom of the hole is less than 5cm, the mud density is reduced to less than 1.15 and then the hole cleaning is stopped. The interval between the completion of hole cleaning and the pouring of concrete shall not exceed 45 minutes. The mud density within 500mm of the bottom of the hole before pouring concrete shall be less than 1.20; S9. Pour the concrete for the pile body. Clean the hole before pouring. The hole wall and bottom should be clean and free of scum and looseness. If there is groundwater and the seepage volume is not large, pump out the accumulated water. Pour with the conduit method. The end of the conduit should be ≤1.5m away from the bottom of the hole. The concrete should be vibrated with an inserted vibrator and vibrated once every 1.5m of pouring. Pour continuously and vibrate to make it dense. The filling coefficient should be >1. The pouring should exceed the designed pile top elevation by 500mm. The concrete strength grade should be C30, the slump should be 160 - 180mm, the initial setting time should be ≥ 45min and ≤2h, the final setting time should be ≤6h, the pouring time should be (10m³) / 30min, the height of the casing submerged during pouring should be ≤3m, and the pipe should be pulled out at a rate of 1m / 6min after pouring to the pipe pulling height. The filling coefficient of the pile concrete test pile should be 1.2 - 1.35, and the expansion depth of the expansion head at the bottom of the pile into the rock should be 3m of the pile into the rock.

2. The method for constructing super-thick backfilled complicated geological conditions bored piles according to claim 1, characterized in that: In step S3, the tamping parameters of the tamping hammer are: 6 hammers, drop distance ≥ 8m, average settlement of the last two hammers ≤ 5cm, and real-time monitoring of the displacement of the soil around the hole during the tamping process. If the displacement rate exceeds 10mm / min, the tamping is suspended and reinforcement measures are taken.

3. The method for constructing super-thick backfilled complicated geological conditions bored piles according to claim 1, characterized in that: In step S3, the water content of the impurity-free silty clay is controlled at 18% - 22%.

4. The method for constructing super-thick backfilled complicated geological conditions bored piles according to claim 1 is characterized by: In step S2, during the process of drilling a hole with the 1.2 m drill bit, the verticality of the hole is checked every 2 m of drilling. If the verticality deviation exceeds 1 / 100, the drill rod angle is adjusted in time.

5. The method for constructing super-thick backfilled bored piles in complex geology according to claim 1 is characterized by: In step S8, the specific steps of the reverse circulation hole cleaning process are: Seal and connect the high-pressure pipe of the mud pump and the injection conduit, turn on the mud pump, and let the mud enter the bottom of the borehole from the mud pool through the injection conduit. Under the action of the mud pump, the mud at the bottom of the hole carries the drilling cuttings and flows upward through the injection conduit and returns to the mud pool on the ground. In the mud pool, the drilling cuttings are separated through sedimentation, filtration and other treatment methods. The purified mud can be recycled again. The mud circulation flow rate is controlled between 100-150m³ / h.

6. The method for constructing super-thick backfilled bored piles in complex geology according to claim 1 is characterized by: In step S6, the main reinforcement of the reinforcement cage is HRB400 grade reinforcement.

7. The method for constructing super-thick backfilled bored piles in complex geology according to claim 1 is characterized by: In step S9, when pouring the pile body concrete, a funnel is arranged on the top of the conduit, and the funnel capacity is not less than 1m³.

8. The method for constructing super-thick backfilled bored piles in complex geology according to claim 1 is characterized by: After the bored pile construction is completed, the settlement of the soil around the pile is observed. The observation period is ≥ 3 months. If the settlement exceeds 10mm, the pile foundation is reinforced.

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