Construction method for cast-in-situ bored pile in treatment process of drainage pipe network

Abstract

The invention relates to the technical field of cast-in-situ bored pile construction, and discloses a construction method for a cast-in-situ bored pile in the treatment process of a drainage pipe network. Positioning and drilling by a drilling machine; wall protecting slurry is prepared; primary hole cleaning; manufacturing and hoisting a reinforcement cage; cleaning the hole for the second time; pouring underwater concrete; the special wall protection slurry is adopted, and high-quality bentonite is selected to ensure that the slurry has good dispersion suspension property and slurry making property, so that the stability of a hole wall is favorably maintained, the hole wall is prevented from collapsing, and the construction safety and progress are ensured; and through the reverse circulation hole cleaning technology and underwater concrete pouring, the cleanliness in the hole and the pouring quality of concrete are improved. By using the pile casing and elaborately designing and manufacturing the reinforcement cage, the structural stability and the bearing capacity of the pile body are improved, and then the uniformity and the stability of the pile body during stress are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of bored cast-in-place pile construction, in particular to a method for constructing bored cast-in-place piles in the process of drainage pipe network management. Background Art

[0002] Bored cast-in-place piles are a basic construction technology widely used in foundation reinforcement and comprehensive drainage network management projects; this method is suitable for complex geological conditions with loose soil, high groundwater level or reinforcement required; bored cast-in-place piles use drilling equipment to drill deep holes in the ground, and then concrete is poured into the holes to form a pile foundation with strong bearing capacity and small deformation.

[0003] The Chinese invention patent with announcement number CN103924584B in the prior art book provides a construction method for bored piles, including several key steps: first, drill holes and install steel cages, fix vertical and horizontal circular pipes on the steel cages, and keep these pipes unobstructed. The tops of these vertical pipes and the ports of the injection pipes are sealed with a water-soluble material. Next, pour concrete into the pile hole. Use an ultra-high pressure water device to inject water into the vertical pipes. When the water-soluble sealing material of the injection pipe is dissolved, the uncured outer layer of concrete is sprayed open by high-pressure water flow to form pits on the side walls of the pile hole. After 28 days, use high-pressure grouting equipment to inject cement mortar into the vertical pipes, and inject into multiple vertical pipes at the same time to fill the areas opened by high-pressure water and penetrate into the side wall pits. After the grouting is completed, wait for the cement mortar to harden to seal the holes.

[0004] However, this method is technically complex and relies on special equipment such as ultra-high pressure water devices and high-pressure grouting equipment, which not only increases the initial investment, but also requires specific technical knowledge, resulting in increased construction costs and time. Secondly, the use of high-pressure water flow to form pits on the side walls of the pile hole will affect the structural stability and bearing capacity of the pile body. In addition, high-pressure operations will bring environmental and safety risks, and once there is a problem with the pile body, subsequent repair and maintenance will also be more difficult. Summary of the invention

[0005] The purpose of the present invention is to provide a method for constructing bored piles in the process of drainage network management, so as to improve the construction quality, efficiency and safety.

[0006] The present invention is implemented by the following technical scheme: A construction method for bored piles in the process of drainage network management, comprising the following steps: Step S1: measuring, setting out and burying pile positions.

[0007] Step S2: making and burying casing.

[0008] Step S3: Drilling machine positioning and drilling.

[0009] Step S4: preparing wall protection slurry.

[0010] Step S5: cleaning the hole once.

[0011] Step S6: Fabrication and hanging of steel cage.

[0012] Step S7: Secondary hole cleaning.

[0013] Step S8: Underwater concrete pouring.

[0014] In order to better implement the present invention, further, the step S1 specifically includes: Step S11: Review the pile position coordinates and confirm the pile position data provided by the design drawings.

[0015] Step S12: staking out and burying of pile guards. Professional surveying personnel use a total station or GPS to carry out on-site staking out of the pile positions using a coordinate method, and lay out the positions of the entire row of guard piles at one time along the direction of the foundation pit.

[0016] Step S13: single pile guard stakeout and pile burying, four pile positions are drawn out in a "cross" shape along the center of the pile to control the pile position, as a single pile guard stake, the single pile guard stake uses a wooden stake (3cm×3cm), the top of the stake is nailed, the height is 80cm, it is buried 45cm underground, and protected with mortar or plain concrete.

[0017] Step S14: The inspection includes self-inspection and supervision inspection. The on-site technicians verify the pile position using the geometric dimension method and review the pile position guard pile once a day. If the guard pile is damaged or displaced, the surveying personnel will be notified in time for re-measurement. After the pile position is laid out, it will be reported to the supervision engineer for review in a timely manner after being checked by the on-site technicians. The supervision engineer will use the total station to use the coordinate method to match the pile position, and after it is correct, the casing will be buried.

[0018] In order to better implement the present invention, further, the step S2 specifically includes: Step S21: Use a 1000mm steel casing with a wall thickness of 5mm; weld 5mm thick and 15cm high reinforcement rings on the top, middle and bottom to enhance structural stability; ensure that the joints are welded densely and without leakage; the top of the casing should be 0.3m above the ground when buried; during construction, first use a 1000mm drill bit to open a hole, then bury the casing, and hoist it with a crane; after installing the casing, replace it with an 800mm drill bit for subsequent operations.

[0019] Step S22: During the installation process, the surveying team will stake out the pile position and the technicians will review it to ensure that the drill bit center is consistent with the pile position center; the hole diameter is 40cm larger than the casing diameter, and the depth is the same as the casing length. After the casing is hoisted into place, it is adjusted by the rope and the plumb line to ensure that the deviation between the center of the casing and the center of the pile position does not exceed 3cm; the verticality of the casing is checked by measuring the distance between the casing and the plumb line, and the slope shall not exceed 1%; after meeting the requirements, the soil is filled symmetrically around the casing and compacted, and finally the position and verticality of the casing are checked again to ensure the accuracy and stability of the installation.

[0020] In order to better implement the present invention, further, the step S3 includes: Step S31: Determine the drilling rig location and mark it with white lime lines around the drilling rig location.

[0021] Step S32: Mark the position, locate, move the rotary drilling rig to the position marked by the white gray line, and do not move it any further.

[0022] Step S33: Connect the guard pile, pull the cross line to adjust the drill bit center to the pile center; adjust the verticality of the drill rod and mast through the drilling rig's own instruments and equipment and lock them.

[0023] Step S34: Start drilling, start slowly and then speed up, start with a penetration of 40-50 cm each time, confirm whether there is an unfavorable stratum underground, and after 5 meters of penetration, if the drilling is normal, increase the penetration appropriately and control it at 70-90 cm each time.

[0024] Step S35: After the hole reaches the designed elevation, the hole depth, hole diameter, hole wall verticality, and sediment thickness are checked.

[0025] In order to better implement the present invention, further, the step S4 specifically includes: Step S41: Selection of raw materials for pulping: bentonite is used for pulping, and calcium sodium-based bentonite mainly composed of montmorillonite is selected to ensure that the soil has good dispersion, suspension and pulping properties, and the quality grade reaches the second-level standard.

[0026] Step S42: Bentonite, water and soda ash are made into a raw slurry in proportion, wherein the content of bentonite in 1 cubic meter of mud is 6-8%, and the content of soda ash is 3%-4% of the content of bentonite; firstly, a certain amount of water is added into the mud preparation box, and then bentonite is added in proportion, and the high-speed water flow generated by the 3PNL mud pump is used to stir in the pool for 30 minutes to fully disperse the bentonite particles, and then soda ash is added in proportion and fully stirred to make the raw slurry.

[0027] Step S43: Mud performance testing. During the drilling process, slag is discharged in a circulating manner. Under normal construction conditions, the mud performance indicators are measured every 4 hours. The specific gravity, viscosity, sand content, etc. of the mud are tested. When it is found that the mud quality cannot meet the wall protection requirements, soda ash and CMC treatment agent are added according to the mud indicators to improve the mud performance and ensure the stability of the hole wall. When drilling to the designed elevation, the drill bit is lifted 5 cm from the bottom of the hole and the drill bit is continued to be rotated to maintain mud circulation, and the mud performance is adjusted so that the hole cleaning mud performance indicators meet the design requirements.

[0028] In order to better implement the present invention, further, step S5 includes: Step S51: After the hole depth is reached, check the hole diameter and verticality, and after passing the inspection, perform hole cleaning.

[0029] Step S52: Use reverse circulation to clean the hole. After the hole is completed, stop drilling, lift the drill bit 10 to 20 cm away from the bottom of the hole, and press mud with a relative density of 1.15 g / cm³ and a sand content of less than 4% at a medium speed to replace the suspended drilling debris in the hole.

[0030] Step S53: high-quality mud is configured to circulate for a sufficient time to displace and discharge the suspended drilling cuttings in the hole. The hole cleaning time is not less than three mud cycles.

[0031] In order to better implement the present invention, further, step S6 includes: Step S61: Fabrication of the steel cage. The main reinforcement of the steel cage is placed on the processing platform. The main reinforcement of the steel cage is first fixedly connected with the reinforcing hoops to form a steel cage skeleton. The main reinforcement of the steel cage is positioned using a special flange disc and then fixedly connected with the reinforcing ring. After the processing of the steel cage skeleton is completed, the spiral hoops are installed. After the spiral hoops are installed, the steel cage is reinforced as a whole. The steel cage is pre-assembled as a whole and acceptance is carried out. The steel cage is disassembled and hoisted.

[0032] Step S62: Connection of the steel cage. In each section of the steel cage, the joints of the longitudinal steel bars are mainly connected by welding. The stirrups and reinforcing bars are also welded, and the single-sided length of the weld must be greater than or equal to 10d, where d is the diameter of the steel bar. To ensure structural stability, the number of steel bar joints on the same section shall not exceed 50% of the total number of main bars in the section, and the positions of two adjacent joints need to be staggered by 35d, where d is the diameter of the steel bar, and maintain a spacing of at least 500mm. In addition, the stirrups are usually in spiral form, and the reinforcing stirrups are connected to the main bars by spot welding.

[0033] Step S63: hoisting the steel cage. The steel cage needs to be hoisted in sections. The steel cage is hoisted by a crane. When the steel cage is a certain height from the ground, the secondary hoisting hook stops hoisting and the main hoist continues to hoist to the hole mouth until the steel cage is placed in the hole.

[0034] In order to better realize the present invention, further, step S7 is specifically as follows: the secondary hole cleaning mainly adopts the air lift reverse circulation method, adjusts the viscosity and specific gravity of the mud, and when the thickness of the sediment at the bottom of the hole is ≤50mm, the viscosity of the slurry in the hole is ≤20s, the sand content is less than 2%, and the specific gravity is ≤1.10, underwater concrete pouring can be carried out after acceptance and approval by the on-site supervision engineer.

[0035] In order to better implement the present invention, further, the step S8 is specifically as follows: Step S81: After the hole is cleaned, install the primary filling bucket and prepare for filling.

[0036] Step S82: Before pouring, check the slump and workability of the concrete at the hole mouth. The slump is 18-22 cm. Pouring can only be done when the slump meets the requirements of underwater pouring and has good workability. Perform initial pouring according to the calculated initial pouring volume to ensure that the buried depth of the conduit in the concrete is controlled at 0.8-1.3 m after the initial pouring.

[0037] Step S83: During the pouring process, the rising height of the concrete is measured and the buried depth of the pipe is calculated. The amount of concrete is measured and recorded every time the concrete surface elevation rises by 5m. The underwater concrete pouring record is filled in and the guide tube is pulled out in time. The buried depth of the guide tube in the concrete is controlled at 2 to 6m, and the minimum buried depth of the pipe shall not be less than 2m. To ensure the strength of the concrete on the pile top, a certain amount of concrete is over-poured on the basis of the designed elevation of the pile top. The over-pour height shall not be less than 0.8m. The concrete shall be poured continuously without pause.

[0038] Step S84: The concrete pouring volume should meet the design and specification requirements. After the on-site technicians measure and confirm that it meets the requirements, the pouring is stopped and the casing is removed in time.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The present invention adopts a special wall protection mud and selects high-quality bentonite to ensure that the mud has good dispersion, suspension and slurry-making properties, which helps to maintain the stability of the hole wall and prevent the hole wall from collapsing, thereby ensuring construction safety and progress.

[0040] (2) The present invention improves the cleanliness of the hole and the quality of concrete pouring through reverse circulation hole cleaning technology and underwater concrete pouring. This not only improves the bearing capacity of the pile, but also reduces the impact of residual impurities in the hole on the strength of the pile body.

[0041] (3) The present invention increases the structural stability and bearing capacity of the pile body by using the casing and carefully designing and manufacturing the steel cage. In particular, the structural reinforcement of the casing and the strict connection specifications of the steel cage ensure the uniformity and stability of the pile body when subjected to stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments with reference to the following drawings: Figure 1 It is a schematic diagram of pile foundation positioning in the present invention; Figure 2 It is a schematic diagram of casing burial in the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, process conditions and advantages of the present invention more clearly understood, the present invention is further described in detail in conjunction with the following embodiments, but the embodiments of the present invention are not limited thereto. Without departing from the above-mentioned technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the field, which should all be included in the scope of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] Embodiment 1: like Figure 1-Figure 2 As shown, a construction method for bored piles in the process of drainage network management includes the following steps: Step S1: measuring, setting out and burying pile positions.

[0045] Step S2: making and burying casing.

[0046] Step S3: Drilling machine positioning and drilling.

[0047] Step S4: preparing wall protection slurry.

[0048] Step S5: cleaning the hole once.

[0049] Step S6: Fabrication and hanging of steel cage.

[0050] Step S7: Secondary hole cleaning.

[0051] Step S8: Underwater concrete pouring.

[0052] Step S1 specifically includes: Step S11: Review the pile position coordinates and confirm the pile position data provided by the design drawings.

[0053] Step S12: staking out and burying of pile guards. Professional surveying personnel use a total station or GPS to carry out on-site staking out of the pile positions using a coordinate method, and lay out the positions of the entire row of guard piles at one time along the direction of the foundation pit.

[0054] Step S13: single pile guard stakeout and pile burying, four pile positions are drawn out in a "cross" shape along the center of the pile to control the pile position, as a single pile guard stake, the single pile guard stake uses a wooden stake (3cm×3cm), the top of the stake is nailed, the height is 80cm, it is buried 45cm underground, and protected with mortar or plain concrete.

[0055] Step S14: The inspection includes self-inspection and supervision inspection. The on-site technicians verify the pile position using the geometric dimension method and review the pile position guard pile once a day. If the guard pile is damaged or displaced, the surveying personnel will be notified in time for re-measurement. After the pile position is laid out, it will be reported to the supervision engineer for review in a timely manner after being checked by the on-site technicians. The supervision engineer will use the total station to use the coordinate method to match the pile position, and after it is correct, the casing will be buried.

[0056] Step S2 specifically includes: Step S21: Use a 1000mm steel casing with a wall thickness of 5mm; weld 5mm thick and 15cm high reinforcement rings on the top, middle and bottom to enhance structural stability; ensure that the joints are welded densely and without leakage; the top of the casing should be 0.3m above the ground when buried; during construction, first use a 1000mm drill bit to open a hole, then bury the casing, and hoist it with a crane; after installing the casing, replace it with an 800mm drill bit for subsequent operations.

[0057] Step S22: During the installation process, the surveying team will stake out the pile position and the technicians will review it to ensure that the drill bit center is consistent with the pile position center; the hole diameter is 40cm larger than the casing diameter, and the depth is the same as the casing length. After the casing is hoisted into place, it is adjusted by the rope and the plumb line to ensure that the deviation between the center of the casing and the center of the pile position does not exceed 3cm; the verticality of the casing is checked by measuring the distance between the casing and the plumb line, and the slope shall not exceed 1%; after meeting the requirements, the soil is filled symmetrically around the casing and compacted, and finally the position and verticality of the casing are checked again to ensure the accuracy and stability of the installation.

[0058] Step S3 comprises: Step S31: Determine the drilling rig location and mark it with white lime lines around the drilling rig location.

[0059] Step S32: Mark the position, locate, move the rotary drilling rig to the position marked by the white gray line, and do not move it any further.

[0060] Step S33: Connect the guard pile, pull the cross line to adjust the drill bit center to the pile center; adjust the verticality of the drill rod and mast through the drilling rig's own instruments and equipment and lock them.

[0061] Step S34: Start drilling, start slowly and then speed up, start with a penetration of 40-50 cm each time, confirm whether there is an unfavorable stratum underground, and after 5 meters of penetration, if the drilling is normal, increase the penetration appropriately and control it at 70-90 cm each time.

[0062] Step S35: After the hole reaches the designed elevation, the hole depth, hole diameter, hole wall verticality, and sediment thickness are checked.

[0063] Step S4 specifically includes: Step S41: Selection of raw materials for pulping: bentonite is used for pulping, and calcium sodium-based bentonite mainly composed of montmorillonite is selected to ensure that the soil has good dispersion, suspension and pulping properties, and the quality grade reaches the second-level standard.

[0064] Step S42: Bentonite, water and soda ash are made into a raw slurry in proportion, wherein the content of bentonite in 1 cubic meter of mud is 6-8%, and the content of soda ash is 3%-4% of the content of bentonite; firstly, a certain amount of water is added into the mud preparation box, and then bentonite is added in proportion, and the high-speed water flow generated by the 3PNL mud pump is used to stir in the pool for 30 minutes to fully disperse the bentonite particles, and then soda ash is added in proportion and fully stirred to make the raw slurry.

[0065] Step S43: Mud performance testing. During the drilling process, slag is discharged in a circulating manner. Under normal construction conditions, the mud performance indicators are measured every 4 hours. The specific gravity, viscosity, sand content, etc. of the mud are tested. When it is found that the mud quality cannot meet the wall protection requirements, soda ash and CMC treatment agent are added according to the mud indicators to improve the mud performance and ensure the stability of the hole wall. When drilling to the designed elevation, the drill bit is lifted 5 cm from the bottom of the hole and the drill bit is continued to be rotated to maintain mud circulation, and the mud performance is adjusted so that the hole cleaning mud performance indicators meet the design requirements.

[0066] Step S5 includes: Step S51: After the hole depth is reached, check the hole diameter and verticality, and after passing the inspection, perform hole cleaning.

[0067] Step S52: Use reverse circulation to clean the hole. After the hole is completed, stop drilling, lift the drill bit 10 to 20 cm away from the bottom of the hole, and press mud with a relative density of 1.15 g / cm³ and a sand content of less than 4% at a medium speed to replace the suspended drilling debris in the hole.

[0068] Step S53: high-quality mud is configured to circulate for a sufficient time to displace and discharge the suspended drilling cuttings in the hole. The hole cleaning time is not less than three mud cycles.

[0069] Step S6 includes: Step S61: Fabrication of the steel cage. The main reinforcement of the steel cage is placed on the processing platform. The main reinforcement of the steel cage is first fixedly connected with the reinforcing hoops to form a steel cage skeleton. The main reinforcement of the steel cage is positioned using a special flange disc and then fixedly connected with the reinforcing ring. After the processing of the steel cage skeleton is completed, the spiral hoops are installed. After the spiral hoops are installed, the steel cage is reinforced as a whole. The steel cage is pre-assembled as a whole and acceptance is carried out. The steel cage is disassembled and hoisted.

[0070] Step S62: Connection of the steel cage. In each section of the steel cage, the joints of the longitudinal steel bars are mainly connected by welding. The stirrups and reinforcing bars are also welded, and the single-sided length of the weld must be greater than or equal to 10d, where d is the diameter of the steel bar. To ensure structural stability, the number of steel bar joints on the same section shall not exceed 50% of the total number of main bars in the section, and the positions of two adjacent joints need to be staggered by 35d, where d is the diameter of the steel bar, and maintain a spacing of at least 500mm. In addition, the stirrups are usually in spiral form, and the reinforcing stirrups are connected to the main bars by spot welding.

[0071] Step S63: hoisting the steel cage. The steel cage needs to be hoisted in sections. The steel cage is hoisted by a crane. When the steel cage is a certain height from the ground, the secondary hoisting hook stops hoisting and the main hoist continues to hoist to the hole mouth until the steel cage is placed in the hole.

[0072] Step S7 is specifically as follows: the secondary hole cleaning mainly adopts the air lift reverse circulation method to adjust the viscosity and specific gravity of the mud. When the thickness of the sediment at the bottom of the hole is ≤50mm, the viscosity of the slurry in the hole is ≤20s, the sand content is less than 2%, and the specific gravity is ≤1.10, underwater concrete pouring can be carried out after acceptance and approval by the on-site supervision engineer.

[0073] Step S8 is specifically as follows: Step S81: After the hole is cleaned, install the primary filling bucket and prepare for filling.

[0074] Step S82: Before pouring, check the slump and workability of the concrete at the hole mouth. The slump is 18-22 cm. Pouring can only be done when the slump meets the requirements of underwater pouring and has good workability. Perform initial pouring according to the calculated initial pouring volume to ensure that the buried depth of the conduit in the concrete is controlled at 0.8-1.3 m after the initial pouring.

[0075] Step S83: During the pouring process, the rising height of the concrete is measured and the buried depth of the pipe is calculated. The amount of concrete is measured and recorded every time the concrete surface elevation rises by 5m. The underwater concrete pouring record is filled in and the guide tube is pulled out in time. The buried depth of the guide tube in the concrete is controlled at 2 to 6m, and the minimum buried depth of the pipe shall not be less than 2m. To ensure the strength of the concrete on the pile top, a certain amount of concrete is over-poured on the basis of the designed elevation of the pile top. The over-pour height shall not be less than 0.8m. The concrete shall be poured continuously without pause.

[0076] Step S84: The concrete pouring volume should meet the design and specification requirements. After the on-site technicians measure and confirm that it meets the requirements, the pouring is stopped and the casing is removed in time.

[0077] Embodiment 2: A construction method for bored piles in the process of drainage network management, comprising the following steps: Step S1: measuring, setting out and burying pile positions.

[0078] Step S2: making and burying casing.

[0079] Step S3: Drilling machine positioning and drilling.

[0080] Step S4: preparing wall protection slurry.

[0081] Step S5: cleaning the hole once.

[0082] Step S6: Fabrication and hanging of steel cage.

[0083] Step S7: Secondary hole cleaning.

[0084] Step S8: Underwater concrete pouring.

[0085] Step S1 specifically includes: Step S11: Review the pile position coordinates and confirm the pile position data provided by the design drawings.

[0086] Step S12: staking out and burying of pile guards. Professional surveying personnel use a total station or GPS to carry out on-site staking out of the pile positions using a coordinate method, and lay out the positions of the entire row of guard piles at one time along the direction of the foundation pit.

[0087] Step S13: single pile guard stakeout and pile burying, four pile positions are drawn out in a "cross" shape along the center of the pile to control the pile position, as a single pile guard stake, the single pile guard stake uses a wooden stake (3cm×3cm), the top of the stake is nailed, the height is 80cm, it is buried 45cm underground, and protected with mortar or plain concrete.

[0088] Step S14: The inspection includes self-inspection and supervision inspection. The on-site technicians verify the pile position using the geometric dimension method and review the pile position guard pile once a day. If the guard pile is damaged or displaced, the surveying personnel will be notified in time for re-measurement. After the pile position is laid out, it will be reported to the supervision engineer for review in a timely manner after being checked by the on-site technicians. The supervision engineer will use the total station to use the coordinate method to match the pile position, and after it is correct, the casing will be buried.

[0089] Step S2 specifically includes: Step S21: Use a 1000mm steel casing with a wall thickness of 5mm; weld 5mm thick and 15cm high reinforcement rings on the top, middle and bottom to enhance structural stability; ensure that the joints are welded densely and without leakage; the top of the casing should be 0.3m above the ground when buried; during construction, first use a 1000mm drill bit to open a hole, then bury the casing, and hoist it with a crane; after installing the casing, replace it with an 800mm drill bit for subsequent operations.

[0090] Step S22: During the installation process, the surveying team will stake out the pile position and the technicians will review it to ensure that the drill bit center is consistent with the pile position center; the hole diameter is 40cm larger than the casing diameter, and the depth is the same as the casing length. After the casing is hoisted into place, it is adjusted by the rope and the plumb line to ensure that the deviation between the center of the casing and the center of the pile position does not exceed 3cm; the verticality of the casing is checked by measuring the distance between the casing and the plumb line, and the slope shall not exceed 1%; after meeting the requirements, the soil is filled symmetrically around the casing and compacted, and finally the position and verticality of the casing are checked again to ensure the accuracy and stability of the installation.

[0091] Step S3 comprises: Step S31: Determine the drilling rig location and mark it with white lime lines around the drilling rig location.

[0092] Step S32: Mark the position, locate, move the rotary drilling rig to the position marked by the white gray line, and do not move it any further.

[0093] Step S33: Connect the guard pile, pull the cross line to adjust the drill bit center to the pile center; adjust the verticality of the drill rod and mast through the drilling rig's own instruments and equipment and lock them.

[0094] Step S34: Start drilling, start slowly and then speed up, start with a penetration of 40-50 cm each time, confirm whether there is an unfavorable stratum underground, and after 5 meters of penetration, if the drilling is normal, increase the penetration appropriately and control it at 70-90 cm each time.

[0095] Step S35: After the hole reaches the designed elevation, the hole depth, hole diameter, hole wall verticality, and sediment thickness are checked.

[0096] Key points and precautions for drilling rig operation during drilling: ① During the drilling process, always pay attention to the drilling rig instrument. If the instrument shows a change in verticality, adjust it in time and continue drilling after adjustment.

[0097] ② When drilling, record the depth of each penetration and fill in the drilling construction record in time. When handing over the shift, the drilling situation and precautions for the next shift should be explained.

[0098] ③ When drilling is stopped for some reason, it is strictly forbidden to leave the drill bit in the hole. After lifting the drill, the hole mouth should be covered for protection.

[0099] ④ The rotary drilling hole should be over-excavated by 10cm to ensure the pile length, and the over-excavation depth of piles in the same row should be basically the same.

[0100] ⑤ During the drilling process, a dedicated person shall be assigned to check the geological conditions.

[0101] ⑥ During the drilling process, the drilling speed of the drill should be adjusted according to the geological conditions. In the clay layer, the drilling speed of the drill should be controlled at 80-90cm / time, and in the sand layer, the drilling speed of the drill should be controlled at 40-50cm / time.

[0102] ⑦ During the drilling process, the lifting speed of the drill rod is controlled at 0.4 m / s.

[0103] Step S4 specifically includes: Step S41: Selection of raw materials for pulping: bentonite is used for pulping, and calcium sodium-based bentonite mainly composed of montmorillonite is selected to ensure that the soil has good dispersion, suspension and pulping properties, and the quality grade reaches the second-level standard.

[0104] Step S42: Bentonite, water and soda ash are made into a raw slurry in proportion, wherein the content of bentonite in 1 cubic meter of mud is 6-8%, and the content of soda ash is 3%-4% of the content of bentonite; firstly, a certain amount of water is added into the mud preparation box, and then bentonite is added in proportion, and the high-speed water flow generated by the 3PNL mud pump is used to stir in the pool for 30 minutes to fully disperse the bentonite particles, and then soda ash is added in proportion and fully stirred to make the raw slurry.

[0105] Step S43: Mud performance testing. During the drilling process, slag is discharged in a circulating manner. Under normal construction conditions, the mud performance indicators are measured every 4 hours. The specific gravity, viscosity, sand content, etc. of the mud are tested. When it is found that the mud quality cannot meet the wall protection requirements, soda ash and CMC treatment agent are added according to the mud indicators to improve the mud performance and ensure the stability of the hole wall. When drilling to the designed elevation, the drill bit is lifted 5 cm from the bottom of the hole and the drill bit is continued to be rotated to maintain mud circulation, and the mud performance is adjusted so that the hole cleaning mud performance indicators meet the design requirements.

[0106] Step S5 includes: Step S51: After the hole depth is reached, check the hole diameter and verticality, and after passing the inspection, perform hole cleaning.

[0107] Step S52: Use reverse circulation to clean the hole. After the hole is completed, stop drilling, lift the drill bit 10 to 20 cm away from the bottom of the hole, and press mud with a relative density of 1.15 g / cm³ and a sand content of less than 4% at a medium speed to replace the suspended drilling debris in the hole.

[0108] Step S53: high-quality mud is configured to circulate for a sufficient time to displace and discharge the suspended drilling cuttings in the hole. The hole cleaning time is not less than three mud cycles.

[0109] Step S6 includes: Step S61: Fabrication of the steel cage. The main reinforcement of the steel cage is placed on the processing platform. The main reinforcement of the steel cage is first fixedly connected with the reinforcing hoops to form a steel cage skeleton. The main reinforcement of the steel cage is positioned using a special flange disc and then fixedly connected with the reinforcing ring. After the processing of the steel cage skeleton is completed, the spiral hoops are installed. After the spiral hoops are installed, the steel cage is reinforced as a whole. The steel cage is pre-assembled as a whole and acceptance is carried out. The steel cage is disassembled and hoisted.

[0110] Step S62: Connection of the steel cage. In each section of the steel cage, the joints of the longitudinal steel bars are mainly connected by welding. The stirrups and reinforcing bars are also welded, and the single-sided length of the weld must be greater than or equal to 10d, where d is the diameter of the steel bar. To ensure structural stability, the number of steel bar joints on the same section shall not exceed 50% of the total number of main bars in the section, and the positions of two adjacent joints need to be staggered by 35d, where d is the diameter of the steel bar, and maintain a spacing of at least 500mm. In addition, the stirrups are usually in spiral form, and the reinforcing stirrups are connected to the main bars by spot welding.

[0111] Step S63: hoisting the steel cage. The steel cage needs to be hoisted in sections. The steel cage is hoisted by a crane. When the steel cage is a certain height from the ground, the secondary hoisting hook stops hoisting and the main hoist continues to hoist to the hole mouth until the steel cage is placed in the hole.

[0112] Things to note when hoisting the steel cage: ① When hoisting the steel cage, a special person should be arranged on site to direct. When the steel cage is put into the hole, it should be aligned with the hole position and gently placed. It should be slowly put into the hole and slowly lowered. It should not rotate left and right. ③ When each section of the steel cage is lowered into the hole to the first reinforcing hoop of each section, insert the shoulder pole to fix the steel cage at the hole mouth. Lift the next section of the steel cage to the top of the hole position, align the main bars, grouting pipes and other pipes of the upper and lower sections of the steel cage, and ensure that the upper and lower axes are consistent. The grouting pipes and acoustic detection pipes are connected and constructed. The welding of the steel joints should be standardized to meet the design requirements, and the welding should be firm and dense. ④ When the hole mouth is extended to extend the steel cage, it should be connected and lowered in sections in the overlapping order. After each section of the steel cage is connected, the spiral bars at the joints are supplemented before the cage is lowered. ⑤ Determine the length of the hanging reinforcement according to the design elevation of the steel cage and the elevation of the casing top, and weld the hanging reinforcement to the main reinforcement firmly. After the steel cage is hoisted to the designed position, fix the hanging reinforcement firmly on the shoulder pole at the hole to prevent the steel cage from floating up or sinking during the concrete pouring process.

[0113] Step S7 is specifically as follows: the secondary hole cleaning mainly adopts the air lift reverse circulation method to adjust the viscosity and specific gravity of the mud. When the thickness of the sediment at the bottom of the hole is ≤50mm, the viscosity of the slurry in the hole is ≤20s, the sand content is less than 2%, and the specific gravity is ≤1.10, underwater concrete pouring can be carried out after acceptance and approval by the on-site supervision engineer.

[0114] Step S8 is specifically as follows: Step S81: After the hole is cleaned, install the primary filling bucket and prepare for filling.

[0115] Step S82: Before pouring, check the slump and workability of the concrete at the hole mouth. The slump is 18-22 cm. Pouring can only be done when the slump meets the requirements of underwater pouring and has good workability. Perform initial pouring according to the calculated initial pouring volume to ensure that the buried depth of the conduit in the concrete is controlled at 0.8-1.3 m after the initial pouring.

[0116] Step S83: During the pouring process, the rising height of the concrete is measured and the buried depth of the pipe is calculated. The amount of concrete is measured and recorded every time the concrete surface elevation rises by 5m. The underwater concrete pouring record is filled in and the guide tube is pulled out in time. The buried depth of the guide tube in the concrete is controlled at 2 to 6m, and the minimum buried depth of the pipe shall not be less than 2m. To ensure the strength of the concrete on the pile top, a certain amount of concrete is over-poured on the basis of the designed elevation of the pile top. The over-pour height shall not be less than 0.8m. The concrete shall be poured continuously without pause.

[0117] Step S84: The concrete pouring volume should meet the design and specification requirements. After the on-site technicians measure and confirm that it meets the requirements, the pouring is stopped and the casing is removed in time.

[0118] Precautions for pouring concrete piles: ① When pouring concrete, the hopper must store enough material for one time to ensure that the conduit is buried in the concrete for more than 1.0m, so as to avoid the phenomenon of mud in the pipe due to the lower end of the conduit not being buried in the concrete, which will lead to the failure of concrete pouring. ② During the pouring process, the concrete should be poured into the silo evenly and not too violently. The concrete pouring situation and whether the steel cage floats should be observed frequently. It is strictly forbidden to pour concrete that does not meet the requirements into the funnel. It should be slipped into the funnel only after the discharge hopper is mixed and qualified. ③ The elevation of the concrete surface layer in the hole should be measured frequently to ensure the buried depth of the conduit. The pouring of concrete must be done in one go, and no pause is allowed. If there is a pause, the conduit must be moved. The conduit must not be released suddenly, and it should be removed quickly. Each time the conduit is removed, it should not exceed 15 minutes. The removed conduit must be lifted steadily to the side and stacked neatly, and rinsed in time, and oiled and maintained in time after drying. ④ When the concrete pouring is near the end, the drainage mud may be too thick and should be removed and unblocked. And carefully calculate and measure the pouring height, and control the reserved height of the pile head. ⑤ Control of the buried depth of the conduit during the pouring process: In order to ensure the concrete quality of the pile body, the depth of the conduit buried in the concrete must be strictly controlled during the concrete pouring process. During the pouring process, the buried depth of the conduit should be 2 to 6 meters. Too large or too small will cause different forms of quality problems under different external conditions, which will directly affect the quality of the pile.

[0119] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for constructing bored piles in the process of drainage network management, characterized in that: The following steps are involved: Step S1: measuring, setting out and burying pile positions; Step S2: making and burying the casing; Step S3: drilling rig positioning and drilling; Step S4: preparing wall protection slurry; Step S5: cleaning the hole once; Step S6: making and hanging the steel cage; Step S7: secondary hole cleaning; Step S8: Underwater concrete pouring.

2. A method for constructing bored piles in the process of drainage network management according to claim 1, characterized in that: The step S1 specifically includes: Step S11: Review the pile position coordinates and confirm the pile position data provided by the design drawings; Step S12: staking out and burying of pile guards, with professional surveyors using a total station or GPS to perform field staking out of the pile positions using a coordinate method, and laying out the entire row of guard piles along the foundation pit direction at one time; Step S13: single pile guard stake setting and pile burying, four pile positions are drawn out in a "cross" shape along the center of the pile to control the pile position, as a single pile guard stake, the single pile guard stake adopts a wooden stake (3cm×3cm), the top of the stake is nailed, the height is 80cm, it is buried 45cm underground, and protected with mortar or plain concrete; Step S14: The inspection includes self-inspection and supervision inspection. The on-site technicians verify the pile position using the geometric dimension method and review the pile position guard pile once a day. If the guard pile is damaged or displaced, the surveying personnel will be notified in time for re-measurement. After the pile position is laid out, it will be reported to the supervision engineer for review in a timely manner after being checked by the on-site technicians. The supervision engineer will use the total station to use the coordinate method to match the pile position, and after it is correct, the casing will be buried.

3. A method for constructing bored piles in the process of drainage network management according to claim 2, characterized in that: The step S2 specifically includes: Step S21: Use a 1000mm steel casing with a wall thickness of 5mm; weld 5mm thick and 15cm high reinforcement rings on the top, middle and bottom to enhance structural stability; ensure that the joints are welded tightly and without leakage; the top of the casing should be 0.3m above the ground when buried; first use a 1000mm drill bit to drill a hole during construction, then bury the casing and hoist it with a crane; after installing the casing, replace it with an 800mm drill bit for subsequent operations; Step S22: During the installation process, the surveying team will mark out the pile position and the technical staff will review it to ensure that the drill center is consistent with the pile center; the diameter of the excavated hole is 40 cm larger than the casing diameter, and the depth is the same as the casing length; after the casing is hoisted into place, it is adjusted by ropes and plumb lines to ensure that the deviation between the center of the casing and the center of the pile position does not exceed 3 cm; the verticality of the casing is checked by measuring the distance between the casing and the plumb line, and the slope shall not exceed 1%; after meeting the requirements, fill the soil symmetrically around the casing and tamp it, and finally check the position and verticality of the casing again to ensure the accuracy and stability of the installation.

4. A method for constructing bored piles in the process of drainage network management according to claim 3, characterized in that: The step S3 comprises: Step S31: Determine the drilling rig location and sprinkle white lime lines around the drilling rig location; Step S32: Mark the position, locate, move the rotary drilling rig to the position marked by the white gray line, and do not move it any further; Step S33: connect the guard pile, pull the cross line to adjust the drill bit center to the pile center; adjust the verticality of the drill rod and mast through the drilling rig's own instruments and equipment and lock them; Step S34: Start drilling, start slowly and then speed up, start with a penetration of 40-50 cm each time, confirm whether there is an unfavorable stratum underground, and if the drilling is normal after 5 meters, increase the penetration appropriately, and control it at 70-90 cm each time; Step S35: After the hole reaches the designed elevation, the hole depth, hole diameter, hole wall verticality, and sediment thickness are checked.

5. A method for constructing bored piles in the process of drainage network management according to claim 4, characterized in that: The step S4 specifically includes: Step S41: Selection of raw materials for pulping: bentonite is used for pulping, and calcium-sodium-based bentonite mainly composed of montmorillonite is selected to ensure that the soil has good dispersion, suspension and pulping properties, and the quality grade reaches the second-level standard; Step S42: Bentonite, water and soda ash are prepared into a stock slurry in proportion, wherein the content of bentonite in 1 cubic meter of mud is 6-8%, and the content of soda ash is 3%-4% of the content of bentonite; a certain amount of water is first added into the mud preparation tank, and then bentonite is added in proportion, and the high-speed water flow generated by the 3PNL mud pump is used to stir in the tank for 30 minutes to fully disperse the bentonite particles, and then soda ash is added in proportion and fully stirred to prepare the stock slurry; Step S43: Mud performance testing. During the drilling process, slag is discharged in a circulating manner. Under normal construction conditions, the mud performance indicators are measured every 4 hours. The specific gravity, viscosity, and sand content of the mud are tested. When it is found that the mud quality cannot meet the wall protection requirements, soda ash and CMC treatment agent are added according to the mud indicators to improve the mud performance and ensure the stability of the hole wall. When drilling to the designed elevation, the drill bit is lifted 5 cm from the bottom of the hole and the drill bit is continued to be rotated to maintain mud circulation, and the mud performance is adjusted so that the hole cleaning mud performance indicators meet the design requirements.

6. A method for constructing bored piles in the process of drainage network management according to claim 5, characterized in that: The step S5 comprises: Step S51: After the hole depth is in place, check the hole diameter and verticality, and after the inspection and certification, perform hole cleaning; Step S52: adopt reverse circulation to clean the hole. After the hole is completed, stop drilling, lift the drill bit 10-20 cm away from the bottom of the hole, and press mud with a relative density of 1.15 g / cm³ and a sand content of less than 4% at a medium speed to replace the suspended drilling debris in the hole; Step S53: high-quality mud is configured to circulate for a sufficient time to displace and discharge the suspended drilling cuttings in the hole. The hole cleaning time is not less than three mud cycles.

7. A method for constructing bored piles in the process of drainage network management according to claim 6, characterized in that: The step S6 comprises: Step S61: making a steel cage, placing the main reinforcement of the steel cage on the processing platform, first fixing and connecting the main reinforcement of the steel cage with the reinforcing hoops to form a steel cage skeleton, positioning the main reinforcement of the steel cage with a special flange disc, and then fixing and connecting it with the reinforcing ring; after the steel cage skeleton is processed, installing the spiral hoops; after the spiral hoops are installed, the steel cage is reinforced as a whole; the steel cage is pre-assembled as a whole, and acceptance construction is carried out; the steel cage is disassembled and hoisted; Step S62: connection of the steel cage. In each section of the steel cage, the joints of the longitudinal steel bars are mainly connected by welding. The stirrups and reinforcing bars are also welded, and the single-sided length of the weld must be greater than or equal to 10d, where d is the diameter of the steel bar. To ensure structural stability, the number of steel bar joints on the same section shall not exceed 50% of the total number of main bars in the section, and the positions of two adjacent joints need to be staggered by 35d, where d is the diameter of the steel bar, and maintain a spacing of at least 500mm. In addition, the stirrups are usually in spiral form, and the reinforcing stirrups are connected to the main bars by spot welding. Step S63: hoisting the steel cage. The steel cage needs to be hoisted in sections. The steel cage is hoisted by a crane. When the steel cage is a certain height from the ground, the secondary hoisting hook stops hoisting and the main hoist continues to hoist to the hole mouth until the steel cage is placed in the hole.

8. A method for constructing bored piles in the process of drainage network management according to claim 7, characterized in that: The step S7 is specifically as follows: the secondary hole cleaning mainly adopts the air lift reverse circulation method to adjust the viscosity and specific gravity of the mud. When the thickness of the sediment at the bottom of the hole is ≤50mm, the viscosity of the slurry in the hole is ≤20s, the sand content is less than 2%, and the specific gravity is ≤1.10, underwater concrete pouring can be carried out after acceptance and approval by the on-site supervision engineer.

9. A method for constructing bored piles in the process of drainage network management according to claim 8, characterized in that: The step S8 is specifically as follows: Step S81: After the hole is cleaned, install the primary filling bucket and prepare for filling; Step S82: Before pouring, check the slump and workability of the concrete at the hole mouth. The slump is 18-22 cm. When the slump meets the requirements of underwater pouring and has good workability, pouring can be carried out. Perform initial pouring according to the calculated initial pouring volume to ensure that the buried depth of the conduit in the concrete is controlled at 0.8-1.3 m after the initial pouring. Step S83: During the pouring process, the rising height of the concrete is measured and the buried pipe depth is calculated. The amount of concrete is measured and recorded every 5m rise in the concrete surface elevation. The underwater concrete pouring record is filled in and the conduit is pulled out in time. The buried depth of the conduit in the concrete is controlled at 2-6m, and the minimum buried pipe depth shall not be less than 2m. To ensure the strength of the concrete on the pile top, a certain amount of concrete is poured on the basis of the designed elevation of the pile top. The over-pouring height shall not be less than 0.8m. The concrete needs to be poured continuously without pauses in the middle. Step S84: When the concrete pouring volume meets the design and specification requirements and is confirmed by the on-site technician to meet the requirements, the pouring is stopped and the casing is removed in time.

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