An integral one-time construction method for underground circular and above-ground square pile foundations

Abstract

A method for the integral one-time construction of an underground circular and above-ground square plate pile foundation, and its construction steps are as follows: S1. Level the site; S2. Measure and set out the lines; S3. Construct the locking groove; S4. Prepare the slurry; S5. Position the drilling rig; S6. Drill the hole; S7. Detect the hole depth, inclination, diameter and clean the hole; S8. Hoist and place the steel bar cage; S9. Install the formwork; S10. Place the conduit; S11. Pour underwater concrete; S12. Decorate the pile body. In the present invention, the part below the ground is constructed by the impact drilling pile method, and the part above the ground is constructed by the method of casting with formwork. The construction methods such as the impact drilling method, the manual dug pile method and the casting with formwork method are skillfully integrated by setting the locking groove and the slurry discharge port; the purpose of one-time pouring of the lower circular and upper square plate pile foundation is realized; the technical effect of one-time pouring of the lower circular and upper square plate pile foundation and avoiding the horizontal construction joint is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of integral construction of sheet pile foundations, and particularly to an integral one-time construction method for an underground circular and above-ground square sheet pile foundation. Background Art

[0002] For underground circular and above-ground square sheet pile foundations, conventional designs are less common. They are mainly used in areas with limited space and large upper loads, where sheet piles are needed as retaining walls to achieve the effect of stabilizing slopes.

[0003] For high embankment roads with high fill, in order to stabilize slopes and prevent collapses, various forms of retaining walls are mostly used. However, for areas with poor geological conditions and effective foundation bearing capacity, piles are generally added under the retaining wall to improve the bearing capacity. But for areas with limited space, due to the limited height of the retaining wall, in order to increase the height of protection and reduce land occupation, pile-sheet retaining walls are mostly used.

[0004] In conventional sheet pile walls, both the upper and lower parts above and below the ground are rectangular. For the part below the ground, artificial dug holes are mostly used for hole formation; for the part above the ground, formwork is erected for pouring.

[0005] For areas with high groundwater levels, large formation permeability coefficients, abundant groundwater, and poor formation stability, due to high safety risks, it is impossible to use the method of artificial dug holes for hole formation. For such areas, mechanical hole formation can only be used for the underground part, and the hole shape is generally circular; the ground part is generally designed as rectangular, mainly to install retaining plates between two pile foundations to increase the retaining capacity, but the number of such pile foundations is small and the construction methods are limited.

[0006] The conventional construction method of underground circular and above-ground square sheet pile foundations will result in a horizontal construction joint at the junction of the above-ground and underground parts of the pile foundation, greatly reducing the retaining capacity of the structure, being unfavorable for the shear resistance of the structure, violating the original design intention, and forming a safety hazard. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides an integral one-time construction method for an underground circular and above-ground square sheet pile foundation.

[0008] The technical solution adopted by the present invention is as follows:

[0009] An integral one-time construction method for an underground circular and above-ground square sheet pile foundation, and its construction steps are as follows:

[0010] S1. Site leveling:

[0011] Before construction, determine the scope of the bored pile site, and arrange personnel to remove sundries and level and compact in a timely manner. The working platform must be flat, firm, stable and tamped, so that the drilling rig can be smoothly positioned and placed stably, and can bear all the loads during construction operations;

[0012] S2. Measurement and setting out:

[0013] Before construction, the pile center and the four corners of the lock are directly marked. The construction personnel determine the location of the lock according to the measurement points. After the lock is constructed, the surveyor re-measures the lock elevation and conducts technical briefing to determine the required excavation depth.

[0014] S3. Make the lock:

[0015] First, the ground part of the lock mouth is constructed. This part is made of reinforced concrete. The top surface is kept flat and the four corners are accurately positioned. Then, according to the geological conditions of the pile hole mouth section, each section is dug down 0.5 to 1m, and C20 concrete is used to cast the retaining wall. The upper and lower sections of the retaining wall steel bars should be reliably connected. The upper section of the retaining wall steel bars penetrate into the lower section of the retaining wall. The retaining wall should be constructed to the boundary line of the light and dark piles. In order to facilitate the discharge of mud during pouring, a hole should be left on the four sides of the lock mouth.

[0016] S4. Mud preparation:

[0017] According to the geological conditions of the pile foundation, the mud is prepared by using imported clay, and additives are added appropriately according to the actual situation on site;

[0018] S5. Drilling rig in place:

[0019] Put the drilling rig in place, set up the drilling frame, align it with the center of the pile hole, adjust and install the lifting system, pull the wind cable, lift the drill bit, and slowly put it into the lock;

[0020] S6. Drilling:

[0021] When drilling, the hole should be filled with mud first. During the drilling and the entire drilling process, the water level in the hole should always be kept at least 1.5m above the groundwater level and 0.3m below the top surface of the lock mouth to prevent overflow. During the drilling process, the waste mud and sediment should be transported to the designated location for treatment by tank trucks and should not be discharged at will at the construction site. After the drilling is completed, the broken drilling debris and part of the mud are squeezed into the hole wall, and most of it is carried out of the hole by mud circulation;

[0022] S7. Check hole depth, inclination, diameter and hole cleaning:

[0023] After the pile foundation is bored, the verticality of the pile is measured with a borehole probe. The length of the borehole probe is 4-6 times the designed pile diameter and not less than 6m. The outer diameter is the same as the designed pile diameter. Both ends are tapered and have sufficient strength. The pile foundation that has passed the borehole probe inspection is promptly cleaned for the second time. The purpose of hole cleaning is to clear the sediment in the pile foundation and the disturbed soft layer, reduce the sediment thickness at the bottom of the pile hole, and prevent the sediment from being too thick at the bottom of the pile and reducing the bearing capacity of the pile;

[0024] S8. Lifting and placement of steel frame:

[0025] The steel cage is fabricated in two sections at the steel processing yard. The main bars and the reinforcement stirrups are all welded to increase the stiffness of the steel cage. The steel bars are connected by welding. The positions of adjacent joints are staggered vertically, horizontally and in all directions. The staggering distance meets the specification requirements. After passing the acceptance, it is transported to the construction site by a tractor and a small trailer, and hoisted by a truck-mounted crane with the assistance of a drilling rig. Before hoisting the steel cage, the length of the lifting bars is welded according to the measurement disclosure. After the steel cage is lowered into the hole, the elevation of the steel cage is promptly rechecked according to the position of the lifting bars to ensure accuracy. Then the steel cage is firmly positioned to prevent the accidents of the steel cage dropping and floating;

[0026] S9. Formwork:

[0027] The pile body formwork is assembled strictly according to the measured points to ensure accuracy. The part of the pile body above the ground is assembled with a standardized steel formwork. After the reinforcement is completed and self-inspection is qualified, it is reported to the supervisor for acceptance. During the installation of the formwork, the hole cleaning operation is always maintained through the reserved holes in the collar to prevent excessive sediment. After the mud performance indexes are detected to meet the requirements, the conduit can be lowered;

[0028] S10. Placing the conduit:

[0029] The underwater concrete is poured using a conduit, and then each section is numbered and the cumulative length is calibrated in the order of entering the hole to ensure that the distance from the bottom of the hole is between 20 and 40 cm;

[0030] S11. Pouring underwater concrete:

[0031] During pouring, the part below the collar adopts the underwater pile pouring process, and the part above the collar is vibrated with an insertion vibrator. The conduit shall not be removed throughout the pouring process. At the end of the pouring, the quantity of the poured concrete is checked, and the depth of the reverse hole is measured to determine whether the measured pouring height of the concrete is correct;

[0032] S12. Pile body finishing:

[0033] After the concrete of the pile body reaches a certain strength, the collar and the retaining wall need to be demolished to finish the pile body.

[0034] The relative density of the mud prepared in step S4 is 1.10 - 1.30, the viscosity is 18 - 24 s, and the sand content is less than 4%.

[0035] During the drilling and slag cleaning in step S6, the soil layer slag samples shall be inspected and preserved. When there are changes and transitions in the soil layer, the changes in the soil layer and the drilling depth shall be recorded, and geological confirmation shall be carried out. In case of differences between the geological conditions and the design, it shall be reported in time. After determining the treatment measures, the construction shall continue.

[0036] In the S6 step, the drilling operation is carried out continuously. When the drilling stops due to reasons, the drill bit is lifted more than 5 m above the bottom of the hole to prevent the hole from collapsing and burying the drill. After taking out the slag or when the drilling stops for other reasons and then starts drilling again, the stroke is gradually increased from a low stroke to the normal stroke to avoid jamming the drill.

[0037] During the entire drilling process in the S6 step, the diameter and size of the drill bit should be checked in a timely manner and repaired in a timely manner to avoid the pile diameter being smaller than the design requirements after the hole is formed.

[0038] In the S8 step, the steel reinforcement cage is processed and hoisted in two sections. When hoisting the lower section, it is temporarily supported on the lock by steel pipes, and the upper and lower sections of the steel reinforcement cage are welded and connected by steel bars.

[0039] In the S11 step, underwater concrete is poured by using a concrete pump truck to pump the concrete into the hopper. During pouring, the slurry is discharged from the reserved hole in the lock. At the same time, high-pressure water is used to flush out the concrete contaminated by the slurry through the reserved hole. When the fresh concrete rises to the lock, the reserved hole is closed, and pouring continues to the top of the pile. At the same time, an insertion vibrator is used for vibration to ensure the compaction of the concrete. To ensure the construction quality, at least 1 m of over-pouring is required, and the excess concrete is directly discharged from the formwork opening.

[0040] In the S8 step, when the length of the steel reinforcement cage is greater than 8 m, the three-point lifting method with a shoulder pole is used for lifting, and when the length of the steel reinforcement cage is less than 8 m, the two-point hoisting method is used.

[0041] The beneficial effects of the present invention: For the part below the ground of the present invention, the construction method of drilling impact piles is adopted, and for the part above the ground, the method of casting with formwork is used. The construction methods such as the impact drilling method, the manual digging method, and the casting with formwork method are skillfully integrated by setting the lock and the slurry discharge port; the purpose of one-time pouring of the pile foundation with a round bottom and a square top plate is realized; the technical effect of one-time pouring of the pile foundation with a round bottom and a square top plate and avoiding horizontal construction joints is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is the plan view of the pile and plate positions of the present invention.

[0043] Figure 2 It is the side view of the pile and plate positions of the present invention.

[0044] Figure 3 It is the plan view of the lock of the present invention.

[0045] Figure 4 It is the side view of the lock of the present invention.

[0046] Figure 5 It is the schematic diagram of the hoisting points of the steel reinforcement cage of the present invention.

[0047] Wherein: 1 - lock; 2 - hole; 3 - retaining plate; 4 - pile; 5 - steel reinforcement cage. DETAILED DESCRIPTION OF THE INVENTION

[0048] Example 1

[0049] Sheet pile foundation design technical parameters and specification requirements:

[0050] Pile diameter and type: bored piles with a depth of 16.5m underground and φ1.5m; rectangular piles 4 with a height of 6m above ground and a size of 1.5*1.5m long, and retaining plates 3 with a height of 6m on the above-ground part.

[0051] The part above the ground is cast by vertical formwork, and the part below the ground is constructed by drilling. The parts above the ground and below the ground should be cast at one time, and no horizontal construction joints should be formed.

[0052] An overall one-time construction method for an underground circular and above-ground square sheet pile foundation, the construction steps of which are:

[0053] S1. Leveling the site:

[0054] Before construction, determine the scope of the bored pile site, arrange personnel to remove debris, level and compact the site in a timely manner, and the working platform must be flat, solid, stable and compacted to enable the drilling rig to be smoothly positioned and placed stably, and to bear all loads during construction;

[0055] S2. Measurement and setting out:

[0056] Before construction, the center of pile 4 and the four corners of lock 1 are directly staked out. The construction personnel determine the location of lock 1 according to the measurement points. After lock 1 is constructed, the surveyor re-measures the elevation of lock 1 and gives technical instructions to determine the required excavation depth.

[0057] S3. Make the lock:

[0058] First, the ground part of the lock mouth 1 is constructed. This part is made of reinforced concrete with a height of 50cm, a thickness of 50cm, and a size of 1.6*1.6m. The top surface is kept flat and the four corners are accurately positioned. Then, according to the geological conditions of the pile hole mouth section, each section is dug down 0.5~1m, and C20 concrete is used to cast the retaining wall. The upper and lower sections of the retaining wall steel bars should be reliably connected. The upper section of the retaining wall steel bars penetrate into the lower section of the retaining wall. The retaining wall should be constructed to the boundary line of the light and dark piles. In order to facilitate the discharge of mud during pouring, a 30*20cm hole 2 is left on each side of the lock mouth 1;

[0059] S4. Mud preparation:

[0060] According to the geological conditions of the pile foundation, the mud is prepared by transporting clay from outside, and additives are added appropriately according to the actual situation on site to adjust the mud. The relative density of the mud is 1.10-1.30, the viscosity is 18-24s, and the sand content is less than 4%;

[0061] S5. Drilling rig in place:

[0062] Position the drilling rig, set up the drill tower, align it with the center of the pile hole, adjust and install the hoisting system, secure the guy ropes, lift the drill bit, and slowly lower it into the collar 1;

[0063] S6. Drilling:

[0064] During the initial drilling, mud should be poured into the hole first. Throughout the entire drilling process, the water level in the hole should always be kept more than 1.5 m above the groundwater level and less than 0.3 m below the top surface of the collar 1 to prevent overflow. During the drilling process, waste mud and sediment should be transported to the designated location for treatment by tanker trucks and should not be randomly discharged at the construction site; when drilling and scooping out sediment, the soil samples of each layer should be inspected and preserved. When there are changes in the strata and at the transition points, record the changes in the strata and the drilling depth, and conduct geological confirmation. In case of differences between the geological conditions and the design, report them in a timely manner. After determining the treatment measures, continue the construction; the drilling operation should be carried out continuously. In case of suspension of drilling due to reasons, lift the drill bit more than 5 m above the bottom of the hole to prevent the hole from collapsing and burying the drill. When resuming drilling after taking out the sediment or due to other reasons for stopping drilling, gradually increase the stroke from a low stroke to the normal stroke to avoid jamming the drill; during the entire drilling process, the diameter and size of the drill bit should be checked in a timely manner and repaired promptly to prevent the pile diameter after hole formation from being smaller than the design requirements. After the drilling is completed, the broken drill cuttings and part of the mud are squeezed into the hole wall, and most of them are carried out of the hole by the mud circulation; during the drilling process, attention should be paid to the changes in the strata. For different soil layers, different drilling methods should be adopted. The stroke is respectively specified according to the soil layer conditions: generally, a large stroke is adopted when passing through hard and dense pebble layers or soil layers such as bedrock boulders; a medium stroke is adopted when passing through loose sand, gravel-like soil or pebble interbedded soil layers. If the stroke is too large, the vibration at the bottom of the hole is large, which is likely to cause the hole to collapse; a medium stroke is adopted when passing through high liquid limit clay and sandy low liquid limit clay; a small stroke is adopted in areas prone to collapse, and the viscosity and relative density of the mud are increased;

[0065] S7. Detecting the hole depth, inclination, diameter and cleaning the hole:

[0066] After the pile foundation hole is formed, use a hole detector to measure the verticality of the pile 1. The length of the hole detector is 4 - 6 times the designed pile diameter and not less than 6 m. The outer diameter is the same as the designed pile diameter, and both ends are tapered and have sufficient strength. For the pile foundation that has passed the inspection of the hole detector, conduct secondary bottom cleaning in a timely manner. The purpose of bottom cleaning is to remove the sediment in the pile foundation and the disturbed soft layer, reduce the sediment thickness at the bottom of the pile hole, and prevent the bearing capacity of the pile 4 from being reduced due to too thick sediment remaining at the bottom of the pile. After bottom cleaning, the mud properties should meet the following standards: 1) When touching the mud discharged or pumped out of the hole by hand, there are no 2 - 3 mm particles; 2) The mud specific gravity is not greater than 1.1; 3) The sand content is less than 2%; 4) The viscosity is 17 - 20 s; 5) The sediment thickness is not greater than 10 cm; The construction allowable deviation and inspection method of the bored pile 4. The allowable deviation of the position of the top surface of the collar 1 of the bored pile is 50 mm, the inclination of the collar 1 is 1%, the center position of the hole of the row of piles is 50 mm, which is checked by the measurement method, and the inclination of the bored pile 4 is 1%;

[0067] S8. Hoisting and placing of steel cage:

[0068] The steel cage 5 is fabricated into two sections in the steel bar processing yard. All the main bars and the reinforcement stirrups are welded to increase the stiffness of the steel cage 5. The steel bars are connected by welding. The positions of adjacent joints are staggered vertically, horizontally and in all directions. The staggering distance meets the specification requirements. After passing the acceptance, it is transported to the construction site by a tractor and a small trailer, and hoisted by a truck crane with the cooperation of the drill rig. Before hoisting the steel cage 5, the length of the hoisting bars is welded according to the hoisting bar length given in the measurement disclosure. After the steel cage 5 is lowered into the hole, the elevation of the steel cage 5 is promptly checked according to the position of the hoisting bars to ensure its accuracy. Then the steel cage 5 is firmly positioned to prevent the accidents of the steel cage dropping and floating. In order to ensure that the steel cage 5 does not deform during hoisting, when the length of the steel cage 5 is greater than 8m, the three-point hoisting method with a spreader is adopted, and the hoisting is kept stable. To prevent the steel cage 5 from deforming, wooden poles or long bamboo poles are added outside the steel cage 5 to enhance its stiffness. The allowable deviations of the steel cage are shown in Table 1. Table 1 Allowable deviations of the steel cage for bored piles

[0069] Serial number Item Allowable deviation (mm) Inspection method 1 Length of steel bar cage ±100 Measurement inspection 2 Diameter of steel bar cage ±20 Measurement inspection 3 Main bar spacing ±0.5d Measurement inspection 4 Spacing of stiffening stirrups ±20 Measurement inspection 5 Spacing of stirrups or spiral bars ±20 Measurement inspection 6 Verticality of steel bar cage 1％L Plumb line and measurement inspection

[0070] The steel cage 5 is processed and hoisted in two sections. During the hoisting of the lower section, it is temporarily supported on the collar 1 with steel pipes. The upper and lower sections of the steel cage 5 are welded and connected with steel bars.

[0071] After the steel reinforcement cage 5 is fabricated and passes the acceptance inspection, it can be hoisted. The installation of the steel reinforcement cage 5 uses a truck crane. To ensure that the steel reinforcement cage 5 does not deform during hoisting, for a long steel reinforcement cage 5, triangular supports should be welded inside the reinforcement cage before hoisting to enhance its stiffness. When the length of the steel reinforcement cage 5 is less than 8m and two-point hoisting is used, the first hoisting point is set at the lower part of the steel reinforcement cage 5, and the second point is set between the midpoint and the upper one-third point of the length of the steel reinforcement cage 5. For a long steel reinforcement cage 5, two fir poles should be temporarily tied inside the steel reinforcement cage 5 before hoisting to enhance its stiffness. During hoisting, first lift the first point to slightly lift the steel reinforcement cage 5, and then lift the second hoisting point simultaneously. After the steel reinforcement cage 5 leaves the ground, stop lifting the first hoisting point and continue to lift the second hoisting point. As the second hoisting point rises continuously, slowly release the first hoisting point until the steel reinforcement cage 5 is perpendicular to the ground and stop hoisting. Release the first hoisting point and check whether the main reinforcement is straight. If it is bent, it should be straightened. When the steel reinforcement cage 5 enters the hole opening, it should be straightened and slowly lowered, and it is strictly prohibited to swing and collide with the hole wall. Then, gradually untie the tying points of the tied fir poles and the steel bar cross supports from bottom to top. When the steel reinforcement cage 5 descends to the vicinity of the second hoisting point and the reinforcement hoop is close to the hole opening, a wooden stick or a steel section (depending on the weight of the cage) can be passed through the lower part of the reinforcement hoop to temporarily support the steel reinforcement cage 5 at the hole opening. The temporary support at the hole opening should meet the strength requirements. Move the hook to the upper end of the steel reinforcement cage 5, remove the temporary support, and slowly lower the steel reinforcement cage 5 until it reaches the design elevation. Temporarily support the steel reinforcement cage 5 at the casing opening, then hoist the second section of the steel reinforcement cage 5, align the vertical main reinforcements of the upper and lower sections of the steel reinforcement cage 5 in a straight line for welding. After all the joints are welded, it can be lowered into the hole until all the steel reinforcement cages 5 are installed. And fix it firmly at the hole opening to prevent the phenomenon of the cage floating during the process of pouring concrete;

[0072] S9. Formwork:

[0073] The pile body formwork is assembled strictly according to the measured points to ensure accuracy. For the part of the pile body above the ground, prefabricated steel formwork is used for assembly. After the reinforcement is completed and self-inspection is qualified, it is reported to the supervisor for acceptance. During the process of installing the formwork, the hole cleaning operation is always maintained through the reserved hole 2 in the collar 1 to prevent excessive sediment. After the mud performance index is detected and meets the requirements, the conduit can be lowered;

[0074] S10. Placing the conduit:

[0075] The conduit used for pouring underwater concrete has an inner diameter of 300mm and a wall thickness of 5mm. Before use, the conduit undergoes a watertight test and a water pressure test. The water pressure is not less than 1.3 times the water depth in the hole. Then, it is numbered section by section according to the order of entry into the hole and the cumulative length is calibrated to ensure that the distance from the bottom of the hole is between 20 and 40cm;

[0076] S11. Pouring underwater concrete:

[0077] During perfusion, the part below the locking mouth 1 adopts the underwater pile perfusion process, and the part above the locking mouth 1 is vibrated with an insertion vibrator. The conduit shall not be removed during the whole perfusion process. For underwater concrete perfusion, a concrete pump truck is used to pump the concrete into the hopper. During perfusion, the slurry is discharged from the reserved hole 2 of the locking mouth 1. At the same time, high-pressure water is used to flush out the concrete contaminated by the slurry through the reserved hole 2. When the fresh concrete rises to the locking mouth 1, the reserved hole 2 is closed, and the pouring continues until the top of the pile 4. At the same time, an insertion vibrator is used for vibration to ensure the compactness of the concrete. To ensure the construction quality, at least 1m of overpouring is required, and the excess concrete is directly discharged from the formwork opening. All the concrete is supplied by the mixing plant and transported to the construction site by concrete mixer trucks.

[0078] The reserve quantity of the first batch of concrete shall meet the requirement of bottom sealing. During perfusion, a 2.0m 3 hopper is used. The concrete mixer truck directly unloads the concrete mixture into the hopper, and continuous unloading is maintained. After the hopper is filled, the valve is opened, and the concrete quickly falls to the bottom of the hole. The whole perfusion process shall be completed within the initial setting time of the first batch of concrete.

[0079] During the process of concrete perfusion, the top height of the underwater concrete shall be measured in a timely and accurate manner to adjust the conduit embedment depth in time and ensure continuous concrete perfusion. The conduit embedment depth during the underwater concrete perfusion process is maintained at 2m to 6m. The specific operation method is as follows: after a truckload of concrete is poured, the height from the concrete surface to the locking mouth 1 is measured with a sounding rope. The measured hole depth minus the concrete height (considering the suspended height of the conduit for the first truckload of concrete) is the conduit embedment depth; after each truckload of concrete is poured, the measured height minus the measured height of the previous truckload of concrete, plus the conduit extended into the concrete last time, is cycled in turn, and the conduit is disassembled according to the length of the on-site conduit. During the period between two pipe extractions, the conduit should be frequently twisted to reduce the adhesion between the conduit and the concrete and avoid the phenomenon of difficult pipe extraction.

[0080] To ensure the quality of the pile head concrete, when pouring the concrete, 0.8m to 1.0m of overpouring is required according to the requirements compared with the design elevation. When pouring to the top of the formwork, all the concrete contaminated by the slurry is discharged from the formwork, and the upper concrete is vibrated with an insertion vibrator;

[0081] At the end of perfusion, check the quantity of the poured concrete and measure the depth of the reverse hole to determine whether the measured pouring height of the concrete is correct; after the concrete perfusion is completed, slowly pull out the conduit with a crane; after the whole construction is completed, clean the construction site to achieve the condition of finishing the work and cleaning the site;

[0082] S12. Pile body finishing:

[0083] After the concrete of the pile body is poured and reaches a certain strength, it is necessary to break the locking mouth 1 and the retaining wall to finish the pile body.

[0084] After the pile body is decorated, backfill with the retaining plate 3.

[0085] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0086] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0087] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or communicable with each other; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0088] The above has described the embodiments of the present invention in detail, but the content described is only the preferred embodiments of the present invention and cannot be considered as used to limit the scope of implementation of the present invention. Any equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. An integral one-time construction method for an underground circular and above-ground square slab pile foundation, characterized in that, The construction steps are: S1. Leveling the site: Before construction, determine the scope of the bored pile site, arrange personnel to remove debris, level and compact the site in a timely manner, and the working platform must be flat, solid, stable and compacted to enable the drilling rig to be smoothly positioned and placed stably, and to bear all loads during construction; S2. Measurement and setting out: Before construction, the pile center and the four corners of the lock mouth (1) are directly staked out. The construction personnel determine the location of the lock mouth (1) according to the measurement points. After the lock mouth (1) is constructed, the surveying personnel re-measure the elevation of the lock mouth (1) and conduct technical briefing to determine the required excavation depth. S3. Make the lock: First, the ground part of the lock mouth (1) is constructed. This part is made of reinforced concrete. The top surface is kept flat and the four corners are accurately positioned. Then, according to the geological conditions of the pile hole mouth section, each section is excavated 0.5 to 1m, and C20 concrete is used to cast the retaining wall. The upper and lower sections of the retaining wall steel bars should be reliably connected. The upper section of the retaining wall steel bars penetrate into the lower section of the retaining wall. The retaining wall should be constructed to the boundary between the light and dark piles. In order to facilitate the discharge of mud during pouring, a hole (2) is left on each side of the lock mouth (1); S4. Mud preparation: According to the geological conditions of the pile foundation, clay is selected to prepare the mud, and additives are added to adjust the mud according to the actual situation on site; S5. Drilling rig in place: Put the drilling rig in place, set up the drilling frame, align it with the center of the pile hole, adjust and install the lifting system, pull the wind cable, lift the drill bit, and slowly put it into the lock (1); S6. Drilling: When drilling a hole, slurry should be poured into the hole first. During the drilling process and the entire drilling process, the water level in the hole should always be kept at least 1.5m above the groundwater level and 0.3m below the top surface of the lock mouth (1) to prevent overflow. During the drilling process, waste mud and sediment should be transported to a designated location for treatment by tank trucks and should not be discharged at will at the construction site. After drilling is completed, the broken drilling debris and part of the mud are squeezed into the hole wall, and most of it is carried out of the hole by mud circulation; S7. Check hole depth, inclination, diameter and hole cleaning: After the pile foundation is bored, the verticality of the pile (4) is measured with a borehole detector. The length of the borehole detector is 4-6 times the designed pile diameter and not less than 6m. The outer diameter is the same as the designed pile diameter. Both ends are tapered and have sufficient strength. The pile foundation that has passed the borehole detector inspection is promptly cleaned for the second time. The purpose of the hole cleaning is to remove the sediment in the pile foundation and the disturbed soft layer, reduce the sediment thickness at the bottom of the pile hole, and prevent the sediment at the bottom of the pile from being too thick and reducing the bearing capacity of the pile (4); S8. Lifting and placement of steel frame: The steel cage (5) is made into two parts at the steel processing plant, and the main reinforcement and the reinforcing stirrups are all welded to increase the rigidity of the steel cage (5). The steel bars are connected by welding, and the adjacent joints are staggered up and down and left and right. The staggered distance meets the requirements of the specification. After acceptance, it is transported to the construction site by a tractor and a small trailer, and is hoisted by a car crane and a drilling rack. Before the steel cage (5) is hoisted, the hoisting rod is welded according to the length of the hoisting rod given by the measurement handover. After the steel cage (5) is entered into the hole, the elevation of the steel cage (5) is promptly checked according to the position of the hoisting rod to see if it is accurate. Then, the steel cage (5) is firmly positioned to prevent the cage from falling or floating. S9. Template: The pile body formwork is assembled strictly according to the measured points to ensure accuracy. The part of the pile body above the ground is assembled with standardized steel formwork. After reinforcement and self-inspection, it is reported to the supervisor for acceptance. During the installation of the formwork, the hole cleaning operation is always carried out through the reserved hole (1) of the collar to prevent excessive sediment. After the mud performance index is detected to meet the requirements, the catheter can be lowered; S10. Place the catheter: The catheter is used for pouring underwater concrete, and then it is numbered section by section according to the hole entry sequence and the cumulative length is calibrated to ensure that the distance from the bottom of the hole is between 20 and 40 cm; S11. Pour underwater concrete: During pouring, the part below the collar (1) adopts the underwater pile pouring process, and the part above the collar (1) is vibrated with an insertion vibrator. The catheter shall not be removed during the whole pouring process. At the end of pouring, check the quantity of the poured concrete and measure the depth of the reverse hole to determine whether the measured pouring height of the concrete is correct. The underwater concrete is poured by a concrete pump truck into the hopper. During pouring, the mud is discharged from the reserved hole (2) of the collar (1). At the same time, the concrete contaminated by the mud is flushed out through the reserved hole (2) by high-pressure water. When the fresh concrete rises to the collar (1), the reserved hole (2) is closed, and the pouring continues to the top of the pile. At the same time, an insertion vibrator is used for vibration to ensure the compactness of the concrete. To ensure the construction quality, at least 1 m of overpouring is required, and the excess concrete is directly discharged from the formwork opening; S12. Pile body finishing: After the concrete of the pile body reaches a certain strength, the collar (1) and the retaining wall need to be demolished to finish the pile body.

2. The integral one-time construction method of the underground circular and above-ground square plate pile foundation according to claim 1, characterized in that, The relative density of the mud prepared in step S4: 1.10 - 1.30, viscosity 18 - 24 s, sand content less than 4%.

3. The integral one-time construction method of the underground circular and above-ground square plate pile foundation according to claim 1, characterized in that, During the drilling and slag cleaning in step S6, the soil layer slag samples should be inspected and saved. When there are changes and transitions in the soil layer, record the soil layer changes and the drilling depth, and conduct geological confirmation. In case of differences between the geological conditions and the design, report immediately and continue construction after determining the treatment measures.

4. The integral one-time construction method of the underground circular and above-ground square slab pile foundation according to claim 3, characterized in that, In step S6, the drilling operation is carried out continuously. When stopping drilling due to reasons, the drill bit is lifted more than 5 m above the bottom of the hole to prevent the hole from collapsing and burying the drill. When resuming drilling after taking slag or stopping drilling for other reasons, start from a low stroke and gradually increase to the normal stroke to avoid jamming the drill.

5. The integral one-time construction method of the underground circular and above-ground square plate pile foundation according to claim 4, characterized in that, During the whole drilling process in step S6, the diameter and size of the drill bit should be checked in time and repaired in time to avoid the pile diameter being smaller than the design requirements after the hole is formed.

6. The integral one-time construction method of the underground circular and above-ground square plate pile foundation according to claim 5, characterized in that, In step S8, the steel reinforcement cage (5) is processed and hoisted in two sections. When hoisting the lower section, it is temporarily supported on the collar (1) by steel pipes, and the upper and lower sections of the steel reinforcement cage (5) are welded and connected with steel bars.

7. The integral one-time construction method of the underground circular and above-ground square plate pile foundation according to claim 6, characterized in that, In step S8, when the length of the steel reinforcement cage (5) is greater than 8 m, the three-point lifting method with a shoulder pole is adopted for lifting, and when the length of the steel reinforcement cage (5) is less than 8 m, the two-point lifting method is adopted.

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