CN113914304A

CN113914304A - CFG pile long spiral drill hole core pipe pumping mixture pouring pile-forming construction method

Info

Publication number: CN113914304A
Application number: CN202111392180.9A
Authority: CN
Inventors: 赵云飞; 李秋石; 孙林智; 梁涛; 袁幸朝; 熊亮
Original assignee: Sinohydro Bureau 5 Co Ltd
Current assignee: Sinohydro Bureau 5 Co Ltd
Priority date: 2021-11-19
Filing date: 2021-11-19
Publication date: 2022-01-11

Abstract

The invention discloses a construction method for pouring and forming a pile by pumping a mixture into a CFG pile long spiral drilling core tube, which comprises the following steps: determining soil property characteristics of a construction site, selecting a pile position determination method according to the soil property characteristics, determining technological parameters of CFG pile construction, performing surface treatment, setting a working cushion layer, measuring and lofting the pile position, positioning a drilling machine, starting drilling, drilling a long spiral drilling hole core pipe to a preset depth, stopping drilling by the drilling machine, pumping a pouring mixture to the long spiral drilling hole core pipe, starting the drilling machine to lift the drilling, and moving the long spiral drilling hole core pipe out of the drilling hole; the invention realizes the pouring of the CFG pile according to the soil property characteristics in the railway construction, realizes the one-step forming of the CFG pile, can realize the rapid construction of the CFG pile under different soil properties, can effectively save the construction time and the construction cost, reduces the pollution to the environment and is beneficial to improving the environment.

Description

CFG pile long spiral drill hole core pipe pumping mixture pouring pile-forming construction method

Technical Field

The invention relates to the field of railway construction, in particular to a construction method for pouring and forming a pile by pumping a mixture through a long spiral drilling core tube of a CFG (cement fly-ash gravel) pile.

Background

The CFG represents cement, fly ash and broken stone respectively, and the composite foundation of the CFG pile obtains even settlement and higher bearing capacity through the arrangement of the flexible mattress layer, and is a novel filling pile which is most economical, applicable, rapid and reliable for reinforcing soft soil foundation.

The rigidity of the gravel pile is improved by the CFG pile, so that the CFG pile not only can well play a side resistance role of the whole pile, but also can well play an end resistance role of the whole pile. Compared with the pile foundation, the CFG composite pile has the advantages that the pile body material of the CFG pile can be doped with industrial waste fly ash, no reinforcement is arranged, and the bearing capacity of soil between the piles is fully exerted. The construction cost is generally 1/2 ~ 2/3 of pile foundation, and economic benefits is very obvious.

In the railway construction at the present stage, CFG piles are less adopted, and related construction is not performed by a corresponding construction method.

Disclosure of Invention

The invention aims to solve the technical problem that a CFG construction method is lacked in railway construction, and aims to provide a construction method for pouring a CFG pile by pumping a mixture into a long spiral drilling core tube, so that the problem of pouring of the CFG pile is solved.

The invention is realized by the following technical scheme:

a CFG pile long spiral drill hole core pipe pumping mixture pouring pile forming construction method comprises the following steps:

determining soil texture characteristics of a construction site, and selecting a pile position determining method according to the soil texture characteristics, wherein the pile position determining method comprises a pile separating jumping driving method and a continuous driving method;

determining technological parameters of CFG pile construction, including mixture mixing proportion, slump, stirring time, drilling speed and pumping pressure;

processing the earth surface, and setting a working cushion layer;

pile position measurement lofting;

the drilling machine is in place, and the long spiral drilling core pipe and the pile position are coaxially arranged;

drilling a long spiral drilling core pipe to a preset depth;

stopping drilling by the drilling machine, and pumping the perfusion mixture to the long spiral drilling core pipe;

the drilling machine starts to lift the drill, and the long spiral drilling core pipe is moved out of the drilling hole;

and moving the drilling machine to the determined next pile position.

Specifically, the thickness of working bed course is 50cm, the surface of working bed course is provided with 2% drainage cross slope, the lower extreme of drainage cross slope is provided with the escape canal.

Specifically, the construction parameters include:

drilling speed: 1m to 1.2 m/min;

the mixture proportion is as follows: cement: sand: crushing stone: water: fly ash: 1: 4.02: 4.92: 0.48: 0.67: 0.0105;

slump: 160-200 mm;

stirring time: not less than 60-120 s;

the drill lifting speed is as follows: 2m to 3.5 m/min;

pumping pressure: 5.5-7.5 Mpa.

Specifically, the pile position measuring and lofting method comprises the following steps:

measuring and releasing the pile position by using a total station;

vertically driving a 20-30 cm deep hole into a pile position by using a positioning steel chisel with the diameter of 8 mm;

and pouring lime powder into the holes for fixing.

Specifically, when the drilling machine is in place, the long spiral drilling core pipe and the positioning steel chisel are coaxially arranged, and the allowable deviation of the pile position in the longitudinal and transverse directions is not more than 5 cm.

Specifically, after the drilling machine stops drilling, cleaning and tamping the hole bottom;

before the mixture is pumped and poured into the long spiral drilling core pipe, the mixture is prepared, and the preparation and adding sequence of the mixture is as follows: broken stone or pebble → cement, fly ash and pumping agent → sand, and the stirring time is not less than 60 s.

Further, the construction method further comprises the following steps:

initially setting the mixture;

removing a soil layer planted on the ground surface by 30 cm;

after the clearing is finished, excavating a protective soil layer for 20 cm;

cutting off a 50cm pile head of the CFG pile which is formed;

pouring a pile cap on the pile head;

and (5) backfilling the soil layer.

Specifically, the construction method for cutting off the 50cm pile head of the CFG pile formed by the pile comprises the following steps:

symmetrically nailing a plurality of steel brazes into the same horizontal plane according to the same angle;

the pile head is hit and cut off.

Specifically, the construction method for pouring the pile cap on the pile head comprises the following steps:

at the concentric pile cap mould of CFG stake top vertical and CFG stake, pile cap mould size: the diameter is 100cm, the thickness is 50cm, and the height of the CFG pile is 10 cm;

and C30 concrete is poured.

Specifically, the construction method of the backfill soil layer comprises the following steps:

backfilling 20cm thick original soil;

and filling the same filler as the embankment on the upper side of the thick original soil, wherein the filling height is up to the pile cap height.

Compared with the prior art, the invention has the following advantages and beneficial effects:

in railway construction, the CFG pile is poured according to soil property characteristics, one-step forming of the CFG pile is realized, rapid construction of the CFG pile under different soil properties can be realized, construction time and construction cost can be effectively saved, pollution to the environment is reduced, and the environment is favorably improved; fills the blank in the foundation treatment and develops a new field of foundation treatment construction. Has remarkable social benefit.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the principles of the invention.

Fig. 1 is a flow schematic diagram of a construction method for pouring a CFG pile long auger hole core pipe into a pile by pumping a mixture according to the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are for purposes of illustration only and are not to be construed as limitations of the invention.

It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings.

In the present invention, the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

The construction method is suitable for clay soil, silt soil, sandy soil, pebble layers (the content of pebbles is not more than 30%) with the grain diameter not more than 60mm and the thickness not more than 5m, and places with high requirements on noise and mud pollution. But is not suitable for the field with wires and cables in the air.

the method comprises the steps of firstly, determining soil texture characteristics of a construction site, and selecting a pile position determining method according to the soil texture characteristics, wherein the pile position determining method comprises a pile separating jumping driving method and a continuous driving method;

the concrete construction method is determined by field tests, and the continuous driving method is easy to cause adjacent piles to be crushed or necked, and is easy to cause ground uplift in cohesive soil; the pile-separating jumping method is not easy to generate the phenomenon, but when the soil layer is hard, a new pile is additionally driven in the middle of the driven pile, so that the driven pile is cracked or broken by vibration.

Therefore, in soft soil, a pile spacing jumping method can be adopted when the pile distance is larger, but the time interval between the construction of a new pile and the piling is not less than 7 d; in saturated loose silt, if the pile spacing is small, a pile-separating jumping method is not suitable; meanwhile, when the pile is arranged in the full length, the principle of 'from one side to the other side' is followed.

Secondly, determining technological parameters of CFG pile construction, including mixture mixing proportion, slump, stirring time, drilling speed and pumping pressure;

according to the requirements of ' temporary standards for passenger transport special line railway roadbed construction quality acceptance and ' technical guidelines for passenger transport special line railway roadbed engineering construction ', 8 CFG test piles are made before construction, and by rechecking geological data and feasibility of equipment, process and construction sequence, various process parameters such as mixture mix proportion, slump, stirring time, drill lifting speed and the like are determined, and the integrity of a pile body and the single pile bearing capacity detected by a flat plate load test are detected by using a low-strain detection technology, the construction parameters of the CFG piles are confirmed as follows:

drilling speed: 1m to 1.2 m/min;

slump: 160-200 mm;

stirring time: not less than 60-120 s;

the drill lifting speed is as follows: 2m to 3.5 m/min;

pumping pressure: 5.5-7.5 Mpa.

Thirdly, processing the earth surface and setting a working cushion layer; the thickness of the working cushion layer is 50cm, the surface of the working cushion layer is provided with a 2% drainage cross slope, and the lower end of the drainage cross slope is provided with a drainage ditch.

And cleaning a flat field, removing ground and high-altitude obstacles, well checking the geological features before construction, and comparing the measured original ground elevation with the designed pile top elevation.

After the field is leveled, a photo wheel road roller is used for rolling to prevent the drilling machine from toppling over during the walking and drilling process of the drilling machine.

And (3) mechanically leveling to 50cm above the elevation of the CFG pile top, taking 50cm as a working cushion layer, making a 2% drainage cross slope on the surface, rolling and compacting by using a YZ26T vibratory roller, and manually excavating drainage ditches around. The height of the top of the CFG pile after leveling is 50cm higher than that of the designed CFG pile, the requirement for cutting the pile head cannot be met if the height is too low, and pile body concrete is wasted if the height is too high.

And fourthly, measuring and lofting the pile position, namely measuring and lofting the test pile position by using a total station, vertically driving the pile position into a deep hole of 20-30 cm by using a positioning drill rod with the diameter of 8mm, pouring lime powder into the hole for fixing, and inserting a marker into the hole, so that the pile position can be conveniently searched and rechecked after the abandoned soil in the drilled hole is buried.

Fifthly, positioning a drilling machine, and coaxially arranging the long spiral drilling core pipe and the pile position;

when the drilling machine is in place, the long spiral drilling core pipe and the positioning steel chisel are coaxially arranged, and the allowable deviation of the pile position in the longitudinal and transverse directions is not more than 5 cm.

The drill must be flat and stable in position and not inclined or moved during construction. And correcting and adjusting the verticality of the drill rod by hanging hammers on two sides of the drilling machine. In order to accurately control the drilling depth, a depth control scale is made on the pile frame so as to observe and record in the construction process and ensure that the verticality tolerance of the CFG pile is not more than 1%.

Before construction, pile-forming technological experiment (not less than 2) is carried out to determine various technological parameters such as mixing proportion, slump, stirring time, pipe drawing speed and the like according to whether composite geological data and equipment and technological construction sequence are proper or not.

Sixthly, drilling the hole, and drilling the long spiral drilling core pipe to a preset depth;

when the drilling is started, the valve of the drill bit is closed, the long spiral drilling core pipe is moved downwards until the drill bit touches the ground, and the motor is started to drill. The drill pipe is slow firstly and fast secondly, so that the shaking of the drill pipe (namely a long spiral drilling core pipe, the same below) at the initial drilling stage is reduced, and the hole deviation is prevented.

When the drill rod shakes or is difficult to drill in the drilling process, the drilling footage should be slowed down. And simultaneously, the deviation of the drill rod is checked and corrected in time. When drilling, recording current change per meter and current value of current mutation position, and simultaneously doing the work of drilling abandoned soil subsection arrangement, and keeping image data as the reference of geological rechecking condition. When the drill bit reaches the preset elevation of the designed pile length and enters the hard body for 50cm, the position of the drill tower body corresponding to the stop position of the bottom surface of the power head is marked obviously and is used as the basis for controlling the pile length in construction.

And before drilling, arranging a mixing station in advance to mix the concrete and convey the mixed concrete to a construction site.

The mixture is stirred and is intensively stirred, the mixture is required to be constructed according to the mixing proportion, the metering is correct, and the feeding sequence is as follows: firstly filling broken stones or pebbles, then adding cement, fly ash and pumping agent, and finally adding sand, so that the cement, fly ash and pumping agent are sandwiched between the sand and the pebbles, and the stirring time of each batch is not less than 60 s. The slump of concrete is controlled to be 16-20 cm, clinker is prepared in a concrete pump hopper and a stirring barrel of a stirrer before pumping, and the mixture can smoothly pass through a rigid pipe, a high-strength flexible pipe, a bent pipe and a reducer pipe to reach the interior of a drill rod core pipe.

Seventhly, stopping drilling by the drilling machine, and pumping the filling mixture to the long spiral drilling core pipe;

and after the drilling machine stops drilling, cleaning and tamping the hole bottom, wherein the cleaning and tamping of the hole bottom are key processes of a immersed tube method, sediment is not more than 10cm, and the hole bottom is tamped by a heavy hammer of not less than 35 kg. If a small amount of ground water is present at the bottom of the hole, dry materials can be added and compacted.

And after the CFG pile is drilled to the designed elevation, stopping drilling, starting pumping the mixture, pouring the mixture to 50cm above the designed CFG pile top elevation, stopping pumping the mixture, wherein the pile length allowable deviation is not more than 10cm, and the pile diameter allowable deviation is not more than 2 cm. And for the long spiral and the pile hole with water, respectively adopting hollow drill rod pumping mixing materials and underwater pouring processes. The normal work of the exhaust valve is guaranteed in the construction, and the exhaust valve is required to be checked frequently in each work shift to prevent the exhaust valve from being blocked by cement.

Eighthly, starting the drill by the drilling machine, and moving the long spiral drilling core pipe out of the drilling hole;

and starting tube drawing after the long spiral drilling core tube is filled with the mixture, and strictly forbidding to draw the tube first and then pump the mixture.

When the pipe is pulled out, the drill rod must stop rotating, the pipe is strictly prevented from being pulled out and rotating, the pile-forming lifting speed is controlled to be 2-3 m/min, the pile-forming process is continuously carried out, and the problem that the machine is stopped for material waiting due to slow feeding of the background is avoided. The machine is prevented from stopping in saturated sandy soil and silt soil layers. After the pouring is finished, the pile head is covered by a cement bag for protection.

The elevation of the construction pile top is about 50cm higher than the designed pile top, the allowable deviation of the pile length is not more than 10cm, and the allowable deviation of the pile diameter is not more than 2 cm. The machine is stopped to wait for the materials due to slow feeding, and after the pouring pile is formed, a cement bag is used for covering the pile head for protection.

And ninth, moving the drilling machine to the determined next pile position.

And after the previous pile is constructed, the drilling machine is shifted to carry out the construction of the next pile. During construction, because the CFG pile is provided with more soil, the adjacent pile position is often covered, and sometimes the originally calibrated pile position is moved because the supporting leg is pressed beside the pile position when the drilling machine supports the pile. Therefore, when the next pile is constructed, the pile position to be constructed is rechecked according to the position of the ash pile (axis) or the surrounding pile, and the accuracy of the pile position is ensured. When the drilling machine is moved, the bored pile is prevented from being disturbed, so that shallow-layer broken piles and unset pile bodies are prevented from being deformed.

And step ten, initially setting the mixture, removing the ground surface planting soil layer by 30cm, and excavating a protective soil layer by 20cm after the clearing is finished.

After the CFG pile construction is finished and the mixture is initially set (generally 7 days after the construction), piling and cleaning the waste soil. The pile body below the enlarged head cannot be damaged during cleaning; the soil between piles cannot be disturbed; the un-constructed pile position of the working face can not be damaged. And after the clearing is finished, removing the soil layer planted on the ground surface by 30cm, excavating a protective soil layer 20cm below the ground surface, and preventing the rubber soil from being formed without disturbing the substrate soil when the protective soil layer is removed. The elevation is strictly controlled during construction, and overexcavation is avoided.

Eleventh, cutting off a 50cm pile head of the CFG pile formed; symmetrically nailing a plurality of steel brazes into the same horizontal plane according to the same angle; the pile head is hit and cut off.

And after the protective soil layer is removed, cutting off a pile head with the pile top of 50 cm. When cutting pile, the pile cutting machine is used to cut around the pile body, and then the 2 or 4 steel fibres are manually and symmetrically placed on the same horizontal plane at the same angle, and the pile head is cut off by striking with a big hammer.

After the pile head is cut off, the pile top is flattened from periphery to middle by using steel fiber and a hand hammer, and the allowable deviation of the pile top is 0 to +20 mm. If the pile body is broken to be lower than the designed elevation of the pile top too much when the soil among the piles is excavated and the pile head is cut, the pile must be connected to the designed elevation of the pile top, the pile top which is cut flat and chiseled is washed clean by water, and the pile is connected by the mixture of the same material and the mixture ratio of the pile body or the mixture of the pea stone with the strength higher by one grade than the strength of the pile body and exceeds the periphery of the pile by 200 mm.

Step ten, pouring a pile cap at the pile head, erecting a pile cap mould concentric with the CFG pile at the CFG pile top, and sizing the pile cap mould: the diameter is 100cm, the thickness is 50cm, the height of the CFG pile is 10cm, and C30 concrete is poured.

And step thirteen, backfilling a soil layer, backfilling raw soil with the thickness of 20cm, filling the same filler as the embankment on the upper side of the thick raw soil, filling the height of the filler to the elevation of the pile cap, and compacting by using a small machine.

And finally, performing integrity spot check and pile body bearing capacity spot check on the pile body, and finishing the acceptance of the CFG pile after the spot check is qualified.

Meanwhile, a plurality of specific embodiments are provided for illustration:

example one

A civil engineering three-standard-section two-work area of the Jing and Shanghai high-speed railway.

The soft foundation of the roadbed engineering mostly adopts CFG piles for foundation treatment, the total quantity of the CFG piles in the constructed section is about 14 ten thousand long meters, and the maximum pile length is 15.6 m. The CFG pile is a composite foundation of CFG pile formed by mixing a pile body with proper amount of stone chips, fly ash and cement with water and mixing to obtain a pile body with higher bonding strength, and the pile body, soil between piles and mattress layer. CFG stands for cement, fly ash and crushed stone, respectively. Because the industrial waste-fly ash is used to replace part of cement, the construction cost is greatly reduced, and the post strength of the pile body is increased. Through the setting of flexible mattress layer, make CFG stake composite foundation obtain even settlement and higher bearing capacity, be the most economical, suitable for, quick, reliable a novel bored concrete pile of consolidating soft soil foundation. The CFG pile composite foundation is a foundation treatment technology developed on the basis of a gravel pile foundation reinforcing method. The rigidity of the gravel pile is improved by the CFG pile, so that the CFG pile not only can well play a side resistance role of the whole pile, but also can well play an end resistance role of the whole pile. Therefore, the method is widely adopted and achieves good economic and social benefits.

The CFG piles constructed in the civil engineering three-standard-section two-work area of the Jing and Shanghai high-speed railway are all I-type piles through low strain detection, and the engineering quality is good.

Example two

Municipal road engineering of 'four ways and one channel' in a zone of a Tan Jinjing Bay.

The total length is about 23.5 kilometers, wherein CFG piles are adopted for foundation treatment in K0+ 113-K1 + 360-section road soft foundation treatment, the CFG piles are 26.5 kilometers, and 15800 meters are used for piling by adopting CFG piles and adopting long spiral drilling core pipes to pump mixed materials. The construction technology is applied to the project, so that the mastering in the construction processes of technology, quality, safety and the like is greatly improved, and the construction period is shortened for the construction of the project.

EXAMPLE III

And 5, newly building a SJZ-2 standard section line from Shijiazhuang to Jinan railway passenger special line engineering.

The initial mileage of the mark section is: DK51+ 213.36-DK 79+555.99, wherein the length of a main line is 28342.63m, the length of a roadbed is 2004.49m, foundations are processed by CFG piles, the total length of the CFG piles is 3.42 ten thousand m, and the CFG piles are formed by a long spiral drilling core pipe pumping mixed material pile forming construction method. The construction technology is applied to the project, so that the mastering of the technology, the quality, the safety and other construction processes is greatly improved, the working efficiency is increased, and conditions are created for the completion of the main project.

In the description herein, reference to the description of the terms "one embodiment/mode," "some embodiments/modes," "example," "specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment/mode or example is included in at least one embodiment/mode or example of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to be the same embodiment/mode or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments/modes or examples. Furthermore, the various embodiments/aspects or examples and features of the various embodiments/aspects or examples described in this specification can be combined and combined by one skilled in the art without conflicting therewith.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

It will be understood by those skilled in the art that the foregoing embodiments are merely for clarity of description and are not intended to limit the scope of the invention. It will be apparent to those skilled in the art that other variations or modifications may be made on the above invention and still be within the scope of the invention.

Claims

1. A CFG pile long spiral drill hole core pipe pumping mixture pouring pile-forming construction method is characterized by comprising the following steps:

processing the earth surface, and setting a working cushion layer;

pile position measurement lofting;

drilling a long spiral drilling core pipe to a preset depth;

and moving the drilling machine to the determined next pile position.

2. The CFG pile long auger hole core pipe pumping mixture pouring pile forming construction method according to claim 1, wherein the thickness of the working cushion layer is 50cm, the surface of the working cushion layer is provided with a 2% drainage cross slope, and the lower end of the drainage cross slope is provided with a drainage ditch.

3. The CFG pile long auger hole core pipe pumping mixture pouring pile-forming construction method according to claim 1, wherein the construction parameters comprise:

drilling speed: 1m to 1.2 m/min;

slump: 160-200 mm;

stirring time: not less than 60-120 s;

the drill lifting speed is as follows: 2m to 3.5 m/min;

pumping pressure: 5.5-7.5 Mpa.

4. The CFG pile long auger hole core pipe pumping mixture pouring pile-forming construction method according to claim 1, wherein the pile position measuring and lofting method comprises the following steps:

measuring and releasing the pile position by using a total station;

and pouring lime powder into the holes for fixing.

5. The CFG pile long spiral drill hole core pipe pumping mixture pouring pile forming construction method according to claim 4, wherein when a drilling machine is in place, the long spiral drill hole core pipe and the positioning steel chisel are coaxially arranged, and the allowable deviation of the pile position in the longitudinal and transverse directions is not more than 5 cm.

6. The CFG pile long spiral drill hole core pipe pumping mixture pouring pile forming construction method according to claim 1, characterized in that after a drilling machine stops drilling, the bottom of a hole is cleaned and tamped;

7. The CFG pile long auger hole core pipe pumping mixture pouring pile-forming construction method according to claim 1, characterized by further comprising the following steps:

initially setting the mixture;

removing a soil layer planted on the ground surface by 30 cm;

after the clearing is finished, excavating a protective soil layer for 20 cm;

cutting off a 50cm pile head of the CFG pile which is formed;

pouring a pile cap on the pile head;

and (5) backfilling the soil layer.

8. The construction method for pouring the mixture into the core tube of the long auger hole of the CFG pile for piling according to the claim 7, wherein the construction method for cutting off the 50cm pile head of the CFG pile which is piled comprises the following steps:

the pile head is hit and cut off.

9. The CFG pile long auger hole core tube pumping mixture pouring pile-forming construction method is characterized in that the construction method for pouring the pile cap at the pile head comprises the following steps:

and C30 concrete is poured.

10. The CFG pile long auger hole core pipe pumping mixture pouring pile-forming construction method is characterized in that the construction method of the backfill soil layer comprises the following steps:

backfilling 20cm thick original soil;