Building engineering pile foundation construction method

Abstract

The invention relates to the technical field of building construction, in particular to a building engineering pile foundation construction method which comprises the following steps: S1, measurement preparation; s2, plane control; s3, elevation control; s4, pile casing burying; s5, slurry treatment; s6, rotary digging and hole forming; s7, hole cleaning; s8, a reinforcement cage is manufactured and hoisted; and S9, underwater concrete pouring is conducted. According to the method, the requirements of an owner on engineering quality, progress, safety, environmental protection and the like in a bid invitation file can be met; and advanced construction technology and construction equipment are adopted, key parts are emphatically controlled, and the engineering construction quality and speed are guaranteed.

Description

Technical Field

[0001] The invention relates to a construction method for a pile foundation of a building project, in particular to a construction method for a pile foundation of a building project, and belongs to the technical field of building construction. Background Art

[0002] Construction engineering is a broad concept involving many aspects: construction engineering refers to engineering facilities built with building materials for all production, life and environmental management. In a narrow sense, it mainly refers to various houses and their affiliated structures, such as apartments, villas, schools, hospitals, etc., and also includes roads, railways and other buildings. Construction engineering mainly includes the following types of projects: housing engineering: industrial construction engineering; transportation construction engineering; water conservancy construction engineering, etc.; in the construction of housing engineering, the construction of the foundation is particularly important. A good foundation can greatly improve the life and safety of the house.

[0003] Therefore, a construction method for pile foundation of a building project is urgently needed to solve the above-mentioned problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for pile foundation construction of a building project, which can meet the requirements of the owner in the bidding documents on project quality, progress, safety, environmental protection and other aspects; and adopt advanced construction technology and construction equipment to focus on key parts to ensure the quality and speed of project construction.

[0005] In order to achieve the above object, the main technical solution adopted by the present invention includes: a construction method for pile foundation of a building engineering, comprising the following steps:

[0006] S1: Measurement preparation: familiarize yourself with the drawings, construction process and measurement specifications, determine the measurement plan, hand over and check the measurement reference points provided by the owner, and keep records;

[0007] S2: Plane control: Following the principle of "whole first, then part, high precision controlling low precision", a plane control network is established for the entire site, using RTK and polar coordinate method, and then establishing a plane control network for each support construction. The control point piles are protected with concrete and marked with red paint;

[0008] S3: Elevation control: The semi-permanent elevation points buried in the site are measured together with the site leveling base points provided by the owner. After verification, they are used as the reference points for the construction elevation control of the pile foundation. There are four leveling points in the site;

[0009] S4: Casing burial: The burial of casing is firstly done by digging the approximate position with an excavator and then trimming it manually. After the casing is laid, in order to ensure the accurate burial position of the casing, the center point inside the casing and the center point of the pile position are checked with the guard pile measured in advance;

[0010] S5: Mud treatment: A mud pool is set up according to the construction arrangement and route of the pile driver as a mud treatment system; and a mud ditch is set up according to the actual needs of the construction, and the mud ditch pool is excavated on site;

[0011] S6: Rotary drilling: After the drilling rig is in place, the drill rod is adjusted vertically, and then the pile center newly determined after the casing is buried is checked to see if it coincides with the drill bit center. If the deviation is large, the drilling rig position should be adjusted to ensure that the center of the drill hole meets the design requirements, and the drilling rig is used to dig the hole;

[0012] S7: Hole cleaning: When the hole reaches the designed depth and the specified rock layer, the hole cleaning operation will begin after confirmation by the supervisor;

[0013] S8: Fabrication and placement of steel cage: The steel cage is fabricated in the processing yard. The processing must meet the size requirements of the drawings. The cage must be complete and firm. After the hole test is qualified, the steel cage is placed by crane.

[0014] S9: Underwater concrete pouring: Underwater concrete is poured using a Φ250 conduit, with the bottom of the conduit about 30 to 50 cm away from the bottom of the hole. A concrete plug is hung in the conduit. Before pouring begins, the slump and other performance indicators of the concrete should be checked. After meeting the design requirements, the mixer truck is in place and starts unloading. When there is enough concrete storage in the storage hopper, the plug wires on both sides are cut off at the same time. At this time, the mixer truck maintains rapid and continuous feeding to pour the concrete pile foundation.

[0015] Preferably, the plane control in S2 includes: a primary control network and a secondary plane control network. The primary control network is the control reference point provided by the owner. The secondary plane control network is based on the primary plane control network and is arranged at the plane control points in the site. The secondary plane control network will serve as the basis for construction measurement and will use the polar coordinate method for positioning and laying out.

[0016] Preferably, the control method of the plane control point is: measure the control coordinate point to the first support. According to the control network reference points laid out before construction and the division of flow sections during construction, make internal control points in each construction area;

[0017] After the support axis is measured and set, self-inspection must be carried out. After the self-inspection is qualified, the inspection form should be filled in in time, stating the inspection content and attaching a measurement result table of the inspection content to be submitted to the supervision unit for review and approval, and the accuracy of each measurement result should be verified in time;

[0018] The method of plane detail measurement is as follows: 1. Pile position measurement and layout: mark the coordinates of the center point of the engineering pile, and then use the coordinate layout function of the high-precision electronic total station to layout the pile position; 2. Use CAD software to mark the coordinates of each feature point, and then use the coordinate layout function of the total station to layout the required points one by one.

[0019] Preferably, the elevation transmission method in S3 is: 1. Joint measurement of elevation control points: when measuring the elevation within the project, first jointly measure the elevation control points; only after confirmation through joint measurement can the required elevation be measured within the project; 2. The method for measuring the elevation reference point adopts the steel ruler method, based on the elevation control point, and uses a level to measure and set up a leveling route for the project with the center wire reading method, and measures the elevation to the side of the ground wall or column, and then uses a 50m steel ruler to measure downward, and the elevation reference point is marked on the side of the ground wall or column with red paint, and the data is indicated.

[0020] Preferably, the manufacturing method of the casing in S4 is: the casing is rolled with a steel plate with a thickness of 10 mm, the inner diameter of the casing is 20 to 30 cm larger than the pile diameter, the length is 2 to 6 m, a 30*20 cm overflow port is opened 20 cm from the top, the pile position deviation of the protective pile shall not be greater than 50 mm, the top of the casing is 0.5 m above the ground and the vertical inclination is not greater than 0.5%.

[0021] Preferably, in S5, bentonite slurry is used to prepare the slurry, and the performance index of the slurry preparation is:

[0022] The proportion is 1.10-1.15;

[0023] The viscosity is as follows: clay soil: 18S~25S, sandy soil: 25S~30S;

[0024] Sand content: <6%;

[0025] PH value: 7-9;

[0026] The specific gravity is tested by the mud specific gravity method, the viscosity is tested by the funnel method, the sand content is tested by the bottle washing method, and the pH value is tested by pH test paper.

[0027] When drilling holes in clay soil, clean water is injected to make slurry with original soil to protect the wall, and the circulating slurry density is controlled at 1.1-1.3. When drilling holes in sandy soil and thick sand-interlayered layers, mud balls are put into the holes to make slurry, and the density is controlled at 1.2-1.3.

[0028] Preferably, the quality of the filling hole in S6 is as follows: the allowable deviation of the pile position, the axis and the vertical axis direction should not exceed 5cm, the verticality deviation of the pile body is not more than 0.5%, the main reinforcement spacing deviation is not more than 10mm, the stirrup spacing deviation is not more than 20mm, the steel cage length deviation is not more than 100mm, the steel cage diameter deviation is not more than 10mm, and the bottom sediment thickness is not more than 50mm;

[0029] The method of filling holes is as follows: at the beginning, the cutting teeth of the drill bit cut into the soil layer to a relatively small depth under the action of the deadweight of the drill tool, and as the drill bucket rotates, the soil layer in front is cut and the crushed soil cut is put into the drill bucket. The depth of the drill bucket drilling into the soil layer and the weight of the soil added to the drill bucket continue to increase, and the rotational resistance also increases; due to the action of the hydraulic torque converter in the transmission system, as the rotational resistance increases, its rotation speed decreases, and the pressure on the contact surfaces of the grooves and keys of the inner and outer drill rods for transmitting torque also increases accordingly. At this time, the pressurized oil cylinder is operated to pressurize the drill rod column, and its pressure can be transmitted to the drill bit, increasing the penetration depth of the drill bucket; the drilling load increases accordingly, and the rotation speed further decreases, and even stops rotating instantly. In this way, a drilling process is performed in which the penetration depth rotational resistance torque increases step by step in a very short time, and the load and rotation speed fluctuate within a wide range;

[0030] Therefore, when the drill bucket is lowered to the bottom of the hole and the rotary table is driven to rotate, it is self-weight drilling without pressure. After the load increases to a certain extent, the pressurized hydraulic cylinder is operated to pressurize the drill rod column for a short time through the power head. The pressurization operation can be repeated 1 to 2 times depending on the situation. When the drill bucket cuts in very little or even does not cut in after pressurization, the drill should be lifted immediately. Therefore, during the drilling process, the operator should pay close attention to the pressure and speed instruments in the working cabin and the changes in the drilling load, and pressurize and lift the drill in time;

[0031] The performance indicators of the circulating mud generated during rotary drilling are:

[0032] Specific gravity: clay soil: 1.1-1.2, sandy soil: 1.1-1.3, weathered rock: 1.25-1.4;

[0033] Viscosity: clay soil: 18S~30S, sandy soil: 25S~35S;

[0034] Sand content: <8%;

[0035] The specific gravity is tested by the mud specific gravity method, the viscosity is tested by the funnel method, and the sand content is tested by the bottle washing method.

[0036] Preferably, the hole cleaning method in S7 is as follows:

[0037] S10: For pile holes made of original soil, after reaching the designed depth, the hole can be cleaned and the slurry can be replaced. The slurry density after cleaning should be controlled at about 1.15.

[0038] S11: For sandy soil and gravel layers with poor soil quality, the specific gravity of the mud at the bottom of the hole after cleaning should be 1.10-1.15;

[0039] S12: At the end of hole cleaning, in addition to measuring the specific gravity of the mud at the bottom of the hole according to the requirements of paragraphs 1 and 2, the sand content and viscosity should also be measured. The sand content of the mud at the bottom of the hole after hole cleaning should be ≤6%, and the viscosity should be ≤25s;

[0040] S13: The thickness of the sediment at the bottom of the hole after cleaning shall not be greater than 100mm, and shall meet the requirements of ≤50mm for end-bearing piles and ≤100mm for friction piles. Underwater concrete can be poured only after the hole is cleaned and qualified.

[0041] Preferably, the construction method of the steel cage in S8 is as follows:

[0042] S14: Place logs or square timbers at the bottom of the raw steel bars to isolate them from the ground, and prepare rainproof materials such as colored strips;

[0043] S15: During processing, first remove stains on the surface of the raw steel bar, such as paint, scale rust, attached dirt, oil, etc., to keep the surface clean. If there are any bends in the raw steel bar, straighten them before processing;

[0044] S16: The steel bars are connected mechanically, and the joints shall meet the requirements of the specification. The binding order of the skeleton is to process the reinforcing hoops first and then spot weld the spiral hoops;

[0045] S17: The allowable deviation of the main reinforcement protection layer of the steel cage should be ±20mm. Concrete pads should be set on the outside of the steel cage. There should be no less than 2 groups of pads on each section of the steel cage, and each group should have no less than 3 blocks, and they should be evenly distributed on the same section to ensure the thickness of the steel protection layer;

[0046] The lifting method of the steel cage is as follows: the steel cage is lifted by the shoulder pole lifting method, the lifting point is set at the connection between the steel cage hoop and the main reinforcement, and the lifting points are symmetrical and lifted at one time. The steel cage is set with 4 to 6 lifting points to ensure that the steel cage does not deform during lifting. When lifting the steel cage into the hole, it should be aligned with the hole position, kept vertical, gently and slowly put into the hole, and it should not be rotated left and right. If there is an obstacle, the lowering should be stopped, the cause should be found out and dealt with, it is strictly forbidden to lift it high and drop it suddenly or force it in. When lowering the steel cage, a technician is required to experience and other problems. The long pile skeleton should be made in sections. The length of each section should be determined according to the lifting conditions. It should be ensured that there is no deformation and the joints should be staggered. The first section of the steel cage is placed in the hole, and the temporary cross stiffening support is taken out. The I-beam is passed through the stiffening hoop at the top of the casing to hang the steel cage, and the I-beam is ensured to be horizontal and the steel cage is vertical. The second section of the steel cage is hoisted and aligned with the first section, and then mechanical casing connection or welding is performed. Then the steel cage is lowered, and the cycle is repeated. When lowering the steel cage, it should be slow and even. According to the depth of the cage, the verticality of the steel cage manhole should be adjusted at any time to avoid its tilting and swinging as much as possible.

[0047] Preferably, the concrete in S9 is commercial concrete, C35 / C40 underwater concrete, with a slump of 180-220 mm;

[0048] Underwater concrete filling method is:

[0049] 2. Underwater concrete is poured with a Φ250 conduit, the bottom of which is about 30 to 50 cm from the bottom of the hole. A concrete plug is hung in the conduit. Before pouring, the slump and other performance indicators of the concrete should be checked. After the design requirements are met, the mixer truck is in place and starts unloading. When there is enough concrete storage in the storage hopper, the plug wires on both sides are cut off at the same time. At this time, the mixer truck keeps feeding quickly and continuously;

[0050] 2. Check the sediment at the bottom of the hole before pouring. During the pouring process, as the concrete rises, lift and remove the guide tube in time. The bottom of the guide tube should be buried 2 to 4 meters below the concrete surface, not more than 6 meters, and not less than 1 meter;

[0051] 3. During the underwater concrete pouring process, a dedicated person shall measure the buried depth of the conduit and fill in the underwater concrete pouring record form;

[0052] 4. The pouring of underwater concrete should be carried out continuously without interruption;

[0053] 5. When lifting the conduit, avoid hitting the steel cage. When the concrete surface is close to the bottom of the steel cage, control the buried depth of the conduit not too deep. When the concrete surface rises to 3-4m inside the steel cage, lift the conduit so that the bottom of the conduit is higher than the bottom of the steel bar.

[0054] 6. Control the amount of concrete poured in the last time to prevent the pile top from being too low;

[0055] 7. After pouring concrete into the pile hole, wait for the concrete to harden and then backfill the pile hole with stone powder or plain soil.

[0056] The present invention has at least the following beneficial effects:

[0057] 1. By utilizing the following construction steps: S1: measurement preparation; S2: plane control; S3: elevation control; S4: casing burial; S5: mud treatment; S6: rotary drilling; S7: hole cleaning; S8: production and hanging of steel cage; S9: underwater concrete pouring, the invention can meet the owner's requirements in the bidding documents on project quality, progress, safety, environmental protection and other aspects; and adopt advanced construction technology and construction equipment, focus on key parts to ensure the quality and speed of project construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0059] Figure 1 It is a construction process flow chart of the present invention;

[0060] Figure 2It is a schematic diagram of the measurement technical requirements of the present invention;

[0061] Figure 3 It is intended to show the properties of the mud of the present invention;

[0062] Figure 4 It is a schematic diagram showing the performance of the circulating mud of the present invention;

[0063] Figure 5 It is a schematic diagram of the steel cage installation structure of the present invention. DETAILED DESCRIPTION

[0064] The following will describe the implementation methods of the present application in detail with the help of accompanying drawings and examples, so that the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0065] like Figure 1-Figure 5 As shown, the construction engineering pile foundation construction method provided in this embodiment includes the following steps:

[0066] S1: Measurement preparation: familiarize yourself with the drawings, construction process and measurement specifications, determine the measurement plan, hand over and check the measurement reference points provided by the owner, and keep records;

[0067] The number of surveyors and their division of labor are arranged according to the difficulty and quantity of the project. All instruments and equipment entering the site are qualified according to national regulations and are within the validity period. During use, the common indicators of the instruments are checked at any time. Once the deviation exceeds the allowable range, it will be corrected in time to ensure the accuracy of the instrument;

[0068] S2: Plane control: Following the principle of "whole first, then part, high precision controlling low precision", a plane control network is established for the entire site, using RTK and polar coordinate method, and then establishing a plane control network for each support construction. The control point piles are protected with concrete and marked with red paint;

[0069] Plane control includes: primary control network and secondary plane control network. The primary control network is the control reference point provided by the owner. It is the only basis for the establishment and review of the secondary plane control network, and also the only basis for settlement and deformation observation. During the entire construction period, the stability and reliability of this control network must be guaranteed. The setting position of this control point is selected in a stable and reliable place, and a protective device is set;

[0070] The secondary plane control network is based on the primary plane control network and is arranged at the plane control points in the site. The secondary plane control network will serve as the basis for construction measurement. The polar coordinate method is used for positioning and laying out, and points should be placed in relatively stable places as much as possible. Due to the small site and poor stability around the project, the secondary plane control network should be reviewed regularly and can only be used if it meets the accuracy requirements. The control method of the plane control point is to measure the control coordinate point to the first support. According to the control network benchmark points laid out before construction and the division of flow sections during construction, internal control points are made in each construction area;

[0071] After the support axis is measured and set, self-inspection must be carried out. After the self-inspection is qualified, the inspection form should be filled in in time, stating the inspection content and attaching a measurement result table of the inspection content to be submitted to the supervision unit for review and approval, and the accuracy of each measurement result should be verified in time;

[0072] The method of plane detail measurement is as follows: 1. Pile position measurement and placement: mark the coordinates of the center point of the engineering pile, and then use the coordinate layout function of the high-precision electronic total station to place the pile position; 2. Use CAD software to mark the coordinates of each feature point, and then use the coordinate layout function of the total station to place the required points one by one;

[0073] S3: Elevation control: The semi-permanent elevation points buried in the site are measured together with the site leveling base points provided by the owner. After verification, they are used as the reference points for the construction elevation control of the pile foundation. There are four leveling points in the site;

[0074] 2. The elevation transfer method is as follows: 1. Joint measurement of elevation control points: When measuring elevation within the project, first measure the elevation control points; only after the joint measurement confirms that they are correct can the required elevation be measured within the project; 2. The elevation benchmark point measurement method adopts the steel ruler method, based on the elevation control points, using the level to measure the leveling route of the project with the middle thread reading method, measure the elevation to the side of the ground wall or column, and then use a 50m steel ruler to measure downwards. The elevation benchmark point is marked on the side of the ground wall or column with red paint, and the data is marked;

[0075] During the construction process, the elevation is measured and delivered to the project using a level (the model is subject to the actual situation on site). At least three level points are delivered for each excavation layer for mutual verification, and the horizontal line is measured at its average point. When leveling, the level should be placed at the center of the measuring point range as much as possible, and precise leveling should be performed. The allowable error of the horizontal line elevation is ±3mm. The measurement technology requirements are as follows: Figure 2 As shown;

[0076] S4: Casing burial: The burial of casing is firstly done by digging the approximate position with an excavator and then trimming it manually. After the casing is laid, in order to ensure the accurate burial position of the casing, the center point inside the casing and the center point of the pile position are checked with the guard pile measured in advance;

[0077] 3. The production method of the casing is as follows: the casing is rolled with a steel plate with a thickness of 10mm. The inner diameter of the casing is 20-30cm larger than the pile diameter, and the length is 2-6m. A 30*20cm overflow port is opened 20cm away from the top. The position deviation of the pile shall not exceed 50mm. The top of the casing is 0.5m above the ground and the vertical inclination is not more than 0.5% to prevent the hole from collapsing and surface water from flowing into the hole.

[0078] After the casing is buried, the surrounding area is compacted with clay, and then the center line of the pile foundation is restored again. The elevation of the top of the casing is measured with a level and recorded as the baseline for controlling the hole depth;

[0079] After the casing is buried, apply for the measurement supervision engineer to check the center deviation, top elevation and inclination of the casing, and check the accuracy of the "cross" guide pile. Only when the supervision engineer accepts the casing as qualified can the drilling rig be aligned;

[0080] S5: Mud treatment: A mud pool is set up according to the construction arrangement and route of the pile driver as a mud treatment system; and a mud ditch is set up according to the actual needs of the construction, and the mud ditch pool is excavated on site;

[0081] Bentonite slurry is used for mud preparation, and the performance indicators of mud preparation are:

[0082] The proportion is 1.10-1.15;

[0083] The viscosity is as follows: clay soil: 18S~25S, sandy soil: 25S~30S;

[0084] Sand content: <6%;

[0085] PH value: 7-9;

[0086] The specific gravity is tested by the mud specific gravity method, the viscosity is tested by the funnel method, the sand content is tested by the bottle washing method, and the pH value is tested by pH test paper.

[0087] When drilling holes in clay soil, clean water is injected to make slurry with original soil to protect the wall, and the specific gravity of the circulating slurry is controlled at 1.1-1.3; when drilling holes in sandy soil and thick sandy layers, mud balls are put into the hole to make slurry, and the specific gravity is controlled at 1.2-1.3;

[0088] During the drilling process, the mud has the functions of protecting the wall, removing ballast, cooling the equipment, cutting soil and lubricating. Mud preparation is a key measure to ensure the quality of drilling. According to construction experience and the characteristics of this project, mud can be made on site.

[0089] When the mud circulates, the debris brought up by the mud flows through the sedimentation tank and settles down. The good mud flows into the circulation tank for secondary sedimentation, then into the slurry storage tank, and finally injected into the hole through the hose by the mud pump. During the construction process, the mud specific gravity should be controlled according to the geological conditions of different strata to improve the hole quality and footage speed. During the construction process, the specific gravity of the mud should be measured frequently, and the viscosity, sand content and colloid rate should be measured frequently; the mud performance standards are as follows Figure 3 As shown;

[0090] S6: Rotary drilling: After the drilling rig is in place, the drill rod is adjusted vertically, and then the pile center newly determined after the casing is buried is checked to see if it coincides with the drill bit center. If the deviation is large, the drilling rig position should be adjusted to ensure that the center of the drill hole meets the design requirements, and the drilling rig is used to dig the hole;

[0091] The quality of the hole after filling is as follows: the allowable deviation of the pile position, the axis and the vertical axis direction should not exceed 5cm, the verticality deviation of the pile body is not more than 0.5%, the main reinforcement spacing deviation is not more than 10mm, the stirrup spacing deviation is not more than 20mm, the steel cage length deviation is not more than 100mm, the steel cage diameter deviation is not more than 10mm, and the sediment thickness at the bottom of the hole is not more than 50mm;

[0092] The method of filling holes is as follows: at the beginning, the cutting teeth of the drill bit cut into the soil layer to a relatively small depth under the action of the deadweight of the drill tool, and as the drill bucket rotates, the soil layer in front is cut and the crushed soil cut is put into the drill bucket. The depth of the drill bucket drilling into the soil layer and the weight of the soil added to the drill bucket continue to increase, and the rotational resistance also increases; due to the effect of the hydraulic torque converter in the transmission system, as the rotational resistance increases, its rotation speed decreases, and the pressure on the contact surface of the groove and key of the inner and outer drill rods that transmit torque also increases accordingly. At this time, the pressurized oil cylinder is operated to pressurize the drill rod column, and its pressure can be transmitted to the drill bit to increase the penetration depth of the drill bucket; the drilling load increases accordingly, and the rotation speed further decreases, and even stops rotating instantly. In this way, in a very short time, a drilling process in which the penetration depth rotational resistance torque increases step by step, and the load and rotation speed fluctuate in a large range;

[0093] Therefore, when the drill bucket drops to the bottom of the hole and the starter turntable drives the rotation, it is self-weight drilling without pressurization (pressurization when the rotation resistance is not large will shrink the drill string due to the small positive pressure on the inner and outer drill rod torque transmission grooves and key contact surfaces and the resulting axial friction). After the load increases to a certain extent, the pressurized hydraulic cylinder is operated to pressurize the drill string for a short time through the power head. The pressurization operation can be repeated 1 to 2 times depending on the situation. When the drill bucket cuts in very little or even does not cut in after pressurization, the drill should be lifted immediately. Therefore, during the drilling process, the operator should pay close attention to the pressure and speed instruments in the working cabin and the changes in the drilling load, and pressurize and lift the drill in time;

[0094] like Figure 4 As shown in the figure, the performance indicators of the circulating mud generated during rotary drilling are:

[0095] Specific gravity: clay soil: 1.1-1.2, sandy soil: 1.1-1.3, weathered rock: 1.25-1.4;

[0096] Viscosity: clay soil: 18S~30S, sandy soil: 25S~35S;

[0097] Sand content: <8%;

[0098] The specific gravity is tested by the mud specific gravity method, the viscosity is tested by the funnel method, and the sand content is tested by the bottle washing method;

[0099] In addition, the following issues should be noted during drilling:

[0100] 1. Correctly select the shape and specifications of the cutting teeth at the bottom of the drill bucket: For soft layers, wedge-shaped tooth sleeves can be used, with small cutting angles, small edge angles, and slightly larger tooth widths; for hard layers, larger cutting angles and narrower curved angle tooth sleeves should be used; for soft layers, especially cohesive soil layers, the distance between teeth should be larger to avoid mud sticking to the drill, which will greatly reduce the drilling efficiency. After lifting the drill, the bottom cutting teeth should be checked frequently, the mud between the teeth should be cleaned in time, and the blunt tooth sleeves should be replaced;

[0101] 2. To ensure the stability of the hole wall, a casing of appropriate length should be inserted into the hole mouth according to the thickness of the loose layer of the surface soil, and the mud liquid level should be maintained. As the mud leaks and the hole depth increases, the mud should be added to the hole in time;

[0102] 3. Drilling into the rock formation, if you find that the drilling depth is too small each time, use an auger;

[0103] 4. Drill in and excavate the earth, and promptly transport the earth to the arranged site for stacking using a loader;

[0104] 5. During the drilling process, the mud should be tested frequently, and the changes in the strata should be noted. The mud density should be adjusted at any time according to the geological conditions. Slag samples should be taken at the places where the strata change, and the strata conditions should be determined and compared with the geological profile. The drilling construction records should be written truthfully. When the drilling geology is obviously different from the design, it must be reported to the on-site construction personnel in a timely manner. The various indicators of the mud (including mud density, viscosity and sand content) should be measured for each geological layer, and records should be kept;

[0105] 6. Always check the position of the drilling rig to keep it in the correct position and the platform stable until the hole reaches the designed depth;

[0106] 11. S7: Hole cleaning: When the hole reaches the designed depth and the specified rock layer, the hole cleaning operation will begin after confirmation by the supervisor. The hole cleaning method is as follows:

[0107] S10: For pile holes made of original soil, after reaching the designed depth, the hole can be cleaned and the slurry can be replaced. The slurry density after cleaning should be controlled at about 1.15.

[0108] S11: For sandy soil and gravel layers with poor soil quality, the specific gravity of the mud at the bottom of the hole after cleaning should be 1.10-1.15;

[0109] S12: At the end of hole cleaning, in addition to measuring the specific gravity of the mud at the bottom of the hole according to the requirements of paragraphs 1 and 2, the sand content and viscosity should also be measured. The sand content of the mud at the bottom of the hole after hole cleaning should be ≤6%, and the viscosity should be ≤25s;

[0110] S13: The thickness of the sediment at the bottom of the hole after cleaning shall not be greater than 100mm, and shall meet the requirements of ≤50mm for end-bearing piles and ≤100mm for friction piles. Underwater concrete can be poured only after the hole is cleaned to the required standard;

[0111] The hole cleaning uses the mud in the slurry storage tank to carry out positive circulation to replace the slag slurry in the hole. During the hole cleaning process, high-quality mud should be continuously pumped into the hole to keep the liquid level in the hole stable.

[0112] S8: Fabrication and hoisting of steel cage: The steel cage is fabricated in the processing yard. The processing must meet the size requirements of the drawings. The cage is complete and firm. After the hole test is qualified, the steel cage is placed by crane. The construction method of the steel cage is as follows: Figure 5 As shown;

[0113] S14: Place logs or square timbers at the bottom of the raw steel bars to isolate them from the ground, and prepare rainproof materials such as colored strips;

[0114] S15: During processing, first remove stains on the surface of the raw steel bar, such as paint, scale rust, attached dirt, oil, etc., to keep the surface clean. If there are any bends in the raw steel bar, straighten them before processing;

[0115] S16: The steel bars are connected mechanically, and the joints shall meet the requirements of the specification. The binding order of the skeleton is to process the reinforcing hoops first and then spot weld the spiral hoops;

[0116] S17: The allowable deviation of the main reinforcement protection layer of the steel cage should be ±20mm. Concrete pads should be set on the outside of the steel cage. There should be no less than 2 groups of pads on each section of the steel cage, and each group should have no less than 3 blocks, and they should be evenly distributed on the same section to ensure the thickness of the steel protection layer;

[0117] The lifting method of the steel cage is as follows: the steel cage is lifted by the shoulder pole lifting method, the lifting point is set at the connection between the steel cage hoop and the main reinforcement, and the lifting points are symmetrical and lifted at one time. The steel cage is set with 4 to 6 lifting points to ensure that the steel cage does not deform during lifting. When lifting the steel cage into the hole, it should be aligned with the hole position, kept vertical, gently and slowly put into the hole, and it should not be rotated left and right. If there is an obstacle, the lowering should be stopped, the cause should be found out and dealt with, it is strictly forbidden to lift it high and drop it suddenly or force it in. When lowering the steel cage, a technician is required to experience and other problems. The long pile skeleton should be made in sections. The length of each section should be determined according to the hoisting conditions. It should be ensured that there is no deformation and the joints should be staggered. The first section of the steel cage is placed in the hole, and the temporary cross stiffening support is taken out. The I-beam is passed through the stiffening hoop at the top of the casing to hang the steel cage, and the I-beam is ensured to be horizontal and vertical to the steel cage. The second section of the steel cage is hoisted and aligned with the first section, and then the mechanical sleeve connection or welding is performed, and then the steel cage is lowered. This cycle is repeated. When lowering the steel cage, it should be slow and even. According to the depth of the cage, the verticality of the steel cage manhole should be adjusted at any time to avoid its tilt and swing as much as possible.

[0118] S9: Underwater concrete pouring: Underwater concrete is poured using a Φ250 conduit, the bottom of which is about 30 to 50 cm from the bottom of the hole. A concrete plug is placed in the conduit. Before pouring, the slump and other performance indicators of the concrete should be checked. After the design requirements are met, the mixer truck is in place and starts unloading. When there is enough concrete storage in the storage hopper, the plug wires on both sides are cut off at the same time. At this time, the mixer truck keeps feeding quickly and continuously, so as to pour the concrete pile foundation;

[0119] The concrete shall be commercial concrete, C35 / C40 underwater concrete, with a slump of 180-220mm. The concrete must have good workability, and its mix ratio shall be determined through experiments;

[0120] Underwater concrete filling method is:

[0121] 1. Underwater concrete is poured with a Φ250 conduit, the bottom of the conduit is about 30-50cm away from the bottom of the hole, and a concrete plug is hung in the conduit. Before pouring, the slump and other performance indicators of the concrete should be checked. After meeting the design requirements, the mixer truck starts unloading. When there is enough concrete storage in the storage hopper, the plug wires on both sides are cut off at the same time. At this time, the mixer truck keeps feeding quickly and continuously to ensure that the bottom end of the conduit is buried in the underwater concrete at a depth of more than 0.8m at one time to prevent pile breakage;

[0122] 2. Check the sediment at the bottom of the hole before pouring. During the pouring process, as the concrete rises, lift and remove the conduit in time. The bottom of the conduit should be buried 2 to 4 meters below the concrete surface, no more than 6 meters, and no less than 1 meter. It is strictly forbidden to lift the bottom of the conduit out of the concrete surface;

[0123] 3. During the underwater concrete pouring process, a dedicated person shall measure the buried depth of the conduit and fill in the underwater concrete pouring record form;

[0124] 4. The pouring of underwater concrete should be carried out continuously without interruption. Once there is a machine failure, power outage, water outage, conduit blockage, water inflow and other accidents, effective measures should be taken immediately to deal with them, and records should be kept at the same time;

[0125] 5. When lifting the conduit, avoid hitting the steel cage. When the concrete surface is close to the bottom of the steel cage, control the buried depth of the conduit not too deep. When the concrete surface rises to 3-4m inside the steel cage, lift the conduit so that the bottom of the conduit is higher than the bottom of the steel bar to prevent the steel cage from floating up.

[0126] 6. Control the amount of concrete poured in the last time to prevent the pile top from being too low;

[0127] 7. After pouring concrete into the pile hole, wait for the concrete to harden and then backfill the pile hole with stone powder or plain soil to ensure construction safety.

[0128] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0129] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0130] The above description shows and describes several preferred embodiments of the present invention, but as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept described herein through the above teachings or the technology or knowledge of the relevant field. Changes and variations made by those skilled in the art do not depart from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A construction method for pile foundation of a building project, characterized in that: The steps include: S1: Measurement preparation: familiarize yourself with the drawings, construction process and measurement specifications, determine the measurement plan, hand over and check the measurement reference points provided by the owner, and keep records; S2: Plane control: Following the principle of "whole first, then part, high precision controlling low precision", a plane control network is established for the entire site. RTK and polar coordinate method are used to establish a plane control network for each support construction. The control point piles are protected with concrete and marked with red paint. S3: Elevation control: The semi-permanent elevation points buried in the site are measured together with the site leveling base points provided by the owner. After verification, they are used as the reference points for the construction elevation control of the pile foundation. There are four leveling points in the site; S4: Casing burial: The burial of casing is firstly done by digging the approximate position with an excavator and then trimming it manually. After the casing is laid, in order to ensure the accurate burial position of the casing, the center point inside the casing and the center point of the pile position are checked with the guard pile measured in advance; S5: Mud treatment: A mud pool is set up according to the construction arrangement and route of the pile driver as a mud treatment system; and a mud ditch is set up according to the actual needs of the construction, and the mud ditch pool is excavated on site; S6: Rotary drilling: After the drilling rig is in place, the drill rod is adjusted vertically, and then the pile center newly determined after the casing is buried is checked to see if it coincides with the drill bit center. If the deviation is large, the drilling rig position should be adjusted to ensure that the center of the drill hole meets the design requirements, and the drilling rig is used to dig the hole; S7: Hole cleaning: When the hole reaches the designed depth and the specified rock layer, the hole cleaning operation will begin after confirmation by the supervisor; S8: Fabrication and placement of steel cage: The steel cage is fabricated in the processing yard. The processing must meet the size requirements of the drawings. The cage must be complete and firm. After the hole test is qualified, the steel cage is placed by crane. S9: Underwater concrete pouring: Underwater concrete is poured using a Φ250 conduit, with the bottom of the conduit about 30 to 50 cm away from the bottom of the hole. A concrete plug is hung in the conduit. Before pouring begins, the slump and other performance indicators of the concrete should be checked. After meeting the design requirements, the mixer truck is in place and starts unloading. When there is enough concrete storage in the storage hopper, the plug wires on both sides are cut off at the same time. At this time, the mixer truck maintains rapid and continuous feeding to pour the concrete pile foundation.

2. A construction engineering pile foundation construction method according to claim 1, characterized in that: The plane control in S2 includes: the primary control network and the secondary plane control network. The primary control network is the control reference point provided by the owner. The secondary plane control network is based on the primary plane control network and is arranged at the plane control points in the site. The secondary plane control network will be used as the basis for construction measurement and will use the polar coordinate method for positioning and laying out.

3. A construction method for pile foundation of a building project according to claim 2, characterized in that: The control method of the plane control point is: measure the control coordinate point to the first support. According to the control network benchmark points laid out before construction and the division of flow sections during construction, internal control points are made in each construction area; After the support axis is measured and set, self-inspection must be carried out. After the self-inspection is qualified, the inspection form should be filled in in time, stating the inspection content and attaching a measurement result table of the inspection content to be submitted to the supervision unit for review and approval, and the accuracy of each measurement result should be verified in time; The method of plane detail measurement is as follows:

1. Pile position measurement and layout: mark the coordinates of the center point of the engineering pile, and then use the coordinate layout function of the high-precision electronic total station to layout the pile position; 2. Use CAD software to mark the coordinates of each feature point, and then use the coordinate layout function of the total station to layout the required points one by one.

4. A construction method for pile foundation of a building project according to claim 1, characterized in that: The transmission method of the elevation in S3 is as follows:

1. Joint measurement of elevation control points: when measuring the elevation within the project, firstly, the elevation control points are jointly measured; Only after the joint survey confirms that it is correct, can the required elevation be measured within the project; 2. The elevation reference point is measured by pulling a steel ruler. Based on the elevation control point, a level is used to measure the leveling route for the project using the center thread reading method. The elevation is measured to the side of the ground wall or column, and then a 50m steel ruler is used to measure downward. The elevation reference point is marked on the side of the ground wall or column with red paint, and the data is indicated.

5. A construction method for pile foundation of a building project according to claim 1, characterized in that: The manufacturing method of the casing in S4 is as follows: the casing is rolled with a steel plate with a thickness of 10 mm, the inner diameter of the casing is 20 to 30 cm larger than the pile diameter, the length is 2 to 6 m, a 30*20 cm overflow port is opened 20 cm away from the top, the pile position deviation of the casing shall not be greater than 50 mm, the top of the casing is 0.5 m above the ground and the vertical inclination is not greater than 0.5%.

6. A construction method for pile foundation of a building project according to claim 1, characterized in that: In S5, bentonite slurry is used to prepare the slurry, and the performance indicators of the slurry preparation are: The proportion is 1.10-1.15; The viscosity is as follows: clay soil: 18S~25S, sandy soil: 25S~30S; Sand content: <6%; PH value: 7-9; The specific gravity is tested by the mud specific gravity method, the viscosity is tested by the funnel method, the sand content is tested by the bottle washing method, and the pH value is tested by pH test paper. When drilling holes in clay soil, clean water is injected to make slurry with original soil to protect the wall, and the circulating slurry density is controlled at 1.1-1.

3. When drilling holes in sandy soil and thick sand-interlayered layers, mud balls are put into the holes to make slurry, and the density is controlled at 1.2-1.

3.

7. A construction method for pile foundation of a building project according to claim 1, characterized in that: The quality of the hole filling in S6 is as follows: the allowable deviation of the pile position, the axis and the vertical axis direction should not exceed 5cm, the verticality deviation of the pile body is not more than 0.5%, the main reinforcement spacing deviation is not more than 10mm, the stirrup spacing deviation is not more than 20mm, the steel cage length deviation is not more than 100mm, the steel cage diameter deviation is not more than 10mm, and the bottom sediment thickness is not more than 50mm; The method of filling holes is as follows: at the beginning, the cutting teeth of the drill bit cut into the soil layer to a relatively small depth under the action of the deadweight of the drill tool, and as the drill bucket rotates, the soil layer in front is cut and the crushed soil cut is put into the drill bucket. The depth of the drill bucket drilling into the soil layer and the weight of the soil added to the drill bucket continue to increase, and the rotational resistance also increases; due to the action of the hydraulic torque converter in the transmission system, as the rotational resistance increases, its rotation speed decreases, and the pressure on the contact surfaces of the grooves and keys of the inner and outer drill rods for transmitting torque also increases accordingly. At this time, the pressurized oil cylinder is operated to pressurize the drill rod column, and its pressure can be transmitted to the drill bit, increasing the penetration depth of the drill bucket; the drilling load increases accordingly, and the rotation speed further decreases, and even stops rotating instantly. In this way, a drilling process is performed in which the penetration depth rotational resistance torque increases step by step in a very short time, and the load and rotation speed fluctuate within a wide range; Therefore, when the drill bucket is lowered to the bottom of the hole and the rotary table is driven to rotate, it is self-weight drilling without pressure. After the load increases to a certain extent, the pressurized hydraulic cylinder is operated to pressurize the drill rod column for a short time through the power head. The pressurization operation can be repeated 1 to 2 times depending on the situation. When the drill bucket cuts in very little or even does not cut in after pressurization, the drill should be lifted immediately. Therefore, during the drilling process, the operator should pay close attention to the pressure and speed instruments in the working cabin and the changes in the drilling load, and pressurize and lift the drill in time; The performance indicators of the circulating mud generated during rotary drilling are: Specific gravity: clay soil: 1.1-1.2, sandy soil: 1.1-1.3, weathered rock: 1.25-1.4; Viscosity: clay soil: 18S~30S, sandy soil: 25S~35S; Sand content: <8%; The specific gravity is tested by the mud specific gravity method, the viscosity is tested by the funnel method, and the sand content is tested by the bottle washing method.

8. A construction method for pile foundation of a building project according to claim 1, characterized in that: The method for clearing the hole in S7 is as follows: S10: For pile holes made of original soil, after reaching the designed depth, the hole can be cleaned and the slurry can be replaced. The slurry density after cleaning should be controlled at about 1.

15. S11: For sandy soil and gravel layers with poor soil quality, the specific gravity of the mud at the bottom of the hole after cleaning should be 1.10-1.15; S12: At the end of hole cleaning, in addition to measuring the specific gravity of the mud at the bottom of the hole according to the requirements of paragraphs 1 and 2, the sand content and viscosity should also be measured. The sand content of the mud at the bottom of the hole after hole cleaning should be ≤6%, and the viscosity should be ≤25s; S13: The thickness of the sediment at the bottom of the hole after cleaning shall not be greater than 100mm, and shall meet the requirements of ≤50mm for end-bearing piles and ≤100mm for friction piles. Underwater concrete can be poured only after the hole is cleaned and qualified.

9. A construction method for pile foundation of a building project according to claim 1, characterized in that: The construction method of the steel cage in S8 is as follows: S14: Place logs or square timbers at the bottom of the raw steel bars to isolate them from the ground, and prepare rainproof materials such as colored strips; S15: During processing, first remove stains on the surface of the raw steel bar, such as paint, scale rust, attached dirt, oil, etc., to keep the surface clean. If there are bent positions of the raw steel bar, straighten them before processing; S16: The steel bars are connected mechanically, and the joints shall meet the requirements of the specification. The binding order of the skeleton is to process the reinforcing hoops first and then spot weld the spiral hoops; S17: The allowable deviation of the main reinforcement protection layer of the steel cage should be ±20mm. Concrete pads should be set on the outside of the steel cage. There should be no less than 2 groups of pads on each section of the steel cage, and each group should have no less than 3 pads, and they should be evenly distributed on the same section to ensure the thickness of the steel protection layer; The lifting method of the steel cage is as follows: the steel cage is lifted by the shoulder pole lifting method, the lifting point is set at the connection between the steel cage hoop and the main reinforcement, and the lifting points are symmetrical and lifted at one time. The steel cage is set with 4 to 6 lifting points to ensure that the steel cage does not deform during lifting. When lifting the steel cage into the hole, it should be aligned with the hole position, kept vertical, gently and slowly put into the hole, and it should not be rotated left and right. If there is an obstacle, the lowering should be stopped, the cause should be found out and dealt with, it is strictly forbidden to lift it high and drop it suddenly or force it in. When lowering the steel cage, a technician is required to experience and other problems. The long pile skeleton should be made in sections. The length of each section should be determined according to the lifting conditions. It should be ensured that there is no deformation and the joints should be staggered. The first section of the steel cage is placed in the hole, and the temporary cross stiffening support is taken out. The I-beam is passed through the stiffening hoop at the top of the casing to hang the steel cage, and the I-beam is ensured to be horizontal and the steel cage is vertical. The second section of the steel cage is hoisted and aligned with the first section, and then mechanical casing connection or welding is performed. Then the steel cage is lowered, and the cycle is repeated. When lowering the steel cage, it should be slow and even. According to the depth of the cage, the verticality of the steel cage manhole should be adjusted at any time to avoid its tilting and swinging as much as possible.

10. A construction method for pile foundation of a building project according to claim 1, characterized in that: The concrete in S9 is commercial concrete, C35 / C40 underwater concrete, with a slump of 180-220 mm; Underwater concrete filling method is:

1. Underwater concrete is poured with a Φ250 conduit, the bottom of which is about 30 to 50 cm from the bottom of the hole. A concrete plug is hung in the conduit. Before pouring, the slump and other performance indicators of the concrete should be checked. After the design requirements are met, the mixer truck is in place and starts unloading. When there is enough concrete storage in the storage hopper, the plug wires on both sides are cut off at the same time. At this time, the mixer truck keeps feeding quickly and continuously; 2. Check the sediment at the bottom of the hole before pouring. During the pouring process, as the concrete rises, lift and remove the guide tube in time. The bottom of the guide tube should be buried 2 to 4 meters below the concrete surface, not more than 6 meters, and not less than 1 meter; 3. During the underwater concrete pouring process, a dedicated person shall measure the buried depth of the conduit and fill in the underwater concrete pouring record form; 4. The pouring of underwater concrete should be carried out continuously without interruption; 5. When lifting the conduit, avoid hitting the steel cage. When the concrete surface is close to the bottom of the steel cage, control the buried depth of the conduit not too deep. When the concrete surface rises to 3-4m inside the steel cage, lift the conduit so that the bottom of the conduit is higher than the bottom of the steel bar.

6. Control the amount of concrete poured in the last time. The top elevation of the poured pile should be higher than the design by a certain height, generally 0.5 to 1.0 m; 7. After pouring concrete into the pile hole, wait for the concrete to harden and then backfill the pile hole with stone powder or plain soil.

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