CN112144516A

CN112144516A - Construction method of concrete pile

Info

Publication number: CN112144516A
Application number: CN202011107783.5A
Authority: CN
Inventors: 王继忠; 张连喜; 王光亮
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-10-16
Filing date: 2020-10-16
Publication date: 2020-12-29

Abstract

The invention provides a construction method of a concrete pile, which is characterized in that the construction of a concrete cast-in-place pile is firstly completed, under the condition of keeping the integrity of a concrete pile body, the construction of pile end carriers in various forms is carried out, the common hidden dangers of virtual soil, sediment and the like at the pile bottom of the conventional concrete cast-in-place pile are eliminated, the bearing capacity of the concrete cast-in-place pile is further improved, and meanwhile, the work efficiency is improved and the cost is saved. The construction method comprises the following three steps: the one is that pile body concrete is poured after pile casing passageway is preset, carry out the construction that pile tip solidification carrier or closely knit carrier or solidification add closely knit carrier again, the second is that add behind the cast-in-place pile body concrete and establish pile casing passageway, carry out pile tip solidification carrier again or closely knit carrier or solidification add the construction of closely knit carrier, the third kind is that pile body concrete is poured after pile casing passageway is preset, carry out the construction of the closely knit resistance to plucking carrier of pile tip again.

Description

Construction method of concrete pile

Technical Field

The invention relates to the field of civil engineering, in particular to construction of a concrete pile.

Background

With the rapid development of national construction in China, more and more construction projects such as bridges, elevated railways and the like are provided, and the original multi-storey buildings are gradually replaced by high-rise buildings, so that the requirement on the bearing capacity of piles in the foundation is relatively higher and higher. In the face of the trend, a method of increasing the pile diameter and the pile length is generally adopted in geotechnical engineering at present to increase the friction force and the end resistance of the pile so as to achieve the purpose of improving the bearing capacity of the pile, but the construction cost of the large-diameter and large-depth pile is very high because the consumption of building materials is very high, the requirement on construction equipment is very high, the construction cost of general large-scale equipment such as a rotary drilling rig is as high as more than one million or even more than ten million yuan, and the manufacturing cost, the construction cost and the transportation cost are very expensive.

Meanwhile, the large-diameter and large-depth pile form is generally formed by adopting large-caliber rotary drilling hole forming, long spiral hole guiding, impact drilling hole forming and other modes, the soil borrowing method hole forming processes are difficult to avoid the phenomena of sediment, mud clamping and the like at the bottom of the pile, if the sediment at the bottom of the pile is not effectively treated, the bearing capacity of the cast-in-place pile is seriously influenced, and in the technical specification JGJ 94-94 of the building pile foundation, special provisions are particularly made for the sediment at the bottom of the pile. At present, the method for eliminating the pile bottom sediment generally adopts manual hole cleaning and post-pressure grouting, and the two methods have certain limitations, the risk of manual hole cleaning is high, the construction of post-pressure grouting usually needs secondary hole cleaning and secondary pressure grouting, the process is complex, and the cost is high.

Patent No. ZL98101041.5 discloses a pile foundation technology, which includes a composite carrier and a concrete pile body, and is characterized in that a pile casing is filled with fillers such as construction waste, the fillers are rammed by a heavy hammer, and the composite carrier is formed at the pile end by a three-stroke penetration control standard, so that the upper load is effectively transmitted to a better bearing layer through the pile and the composite carrier under the pile, thereby improving the bearing capacity of the pile. However, due to the limitation of construction equipment and construction means, it is difficult to complete a larger diameter and longer pile, and thus it is difficult to apply the carrier pile to a project with high bearing capacity requirement.

In addition, coastal areas of China are areas where developed cities are concentrated, the number of construction projects is large, most of geological conditions of the coastal areas have the same characteristics, namely, the content of underground water is rich, the soil quality is soft, the characteristics cause great difficulty in foundation base treatment, the carrier piles are also the same, and the problems that water enters a pile casing and cannot be constructed, the concrete of a pile body is corroded by water or sludge and is easy to shrink or break, the soil body at the pile end is impacted by fillers to cause serious disturbance and the like are particularly easily encountered in construction, and the bearing capacity of a pile foundation is seriously influenced.

It is therefore desirable to provide a pile which meets the high load bearing requirements and which is adaptable to a variety of geological formations, and which is both highly efficient and relatively low cost.

Disclosure of Invention

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for constructing a concrete pile, which includes completing a construction of a cast-in-place concrete pile, and performing a construction of a pile end carrier of various forms while maintaining the integrity of a concrete pile body, thereby eliminating the general hidden troubles such as loose soil and sediment at the bottom of the conventional cast-in-place concrete pile, further improving the bearing capacity of the cast-in-place concrete pile, and achieving an improvement in work efficiency and a cost saving.

In order to achieve the above object, a method for constructing a concrete pile according to the present invention comprises the steps of:

1) performing construction of pile body hole forming at a pile position in a foundation, wherein the pile body hole forming mode comprises rotary drilling, diving drilling, impact drilling, down-the-hole drilling and long spiral drilling;

2) after the hole is formed to the elevation of the pile bottom, placing a reinforcement cage in the pile hole, and placing more than one pile casing in the reinforcement cage;

3) inserting more than one concrete guide pipe into the pile hole, and pouring concrete into the pile hole through the concrete guide pipes to reach the elevation of the pile top to form a concrete cast-in-place pile taking the pile casing as a pore channel;

4) the concrete guide pipe is proposed, and before the initial setting of the concrete or after the concrete has certain strength, the reinforcement treatment is carried out on the bottom end of the cast-in-place pile by one of the following methods according to the soil layer property and the upper load requirement:

inserting a grouting pipe with an injection head into the pile casing to the bottom end of the pile, pressurizing and injecting cement slurry into the grouting pipe, and simultaneously rotating and gradually sinking the grouting pipe downwards to improve the strength of soil mass in a certain range below the pile end to form a pile end curing carrier;

secondly, placing a slender hammer into the pile casing, filling a certain amount of cement sand mixture into the pile casing, tamping the cement sand mixture by using the hammering kinetic energy of the slender hammer, and repeating the filling and tamping operation to reinforce and compact the soil body below the pile end within a certain depth and range to form a pile end compact carrier;

thirdly, solidifying the soil mass at the pile end and constructing a carrier at the pile end, namely inserting a grouting pipe with an injector head into the pile casing to the bottom end of the pile, pressurizing and injecting cement slurry into the grouting pipe, simultaneously rotating and gradually sinking the grouting pipe downwards to improve the strength of the soil mass below the pile end within a certain range, then putting the grouting pipe out, putting a slender hammer with the diameter smaller than that of the pile casing into the pile casing, filling a certain amount of cement sand mixture into the pile casing, tamping the cement sand mixture by the hammering kinetic energy of the slender hammer, and repeatedly carrying out the filling and tamping operation to ensure that the soil mass below the pile end within a certain depth and range is continuously reinforced and compacted to form the composite carrier at the pile end;

5) the pile body is processed and constructed by one of the following modes:

firstly, providing a grouting pipe or a slender hammer, pouring concrete in a pile casing to the elevation of the pile top, and providing the pile casing to form a pile;

secondly, a grouting pipe or a slender hammer is proposed, a second reinforcement cage is inserted into the pile casing and then concrete is poured to the elevation of the pile top, then the pile casing is proposed to form a pile, or the pile casing is proposed and then the second reinforcement cage is inserted and then concrete is poured to the elevation of the pile top to form a pile;

thirdly, a grouting pipe or a slender hammer is lifted, concrete is poured to the elevation of the pile top, a pile casing is lifted out to form a pile after a second reinforcement cage is reversely inserted into the concrete, or a second reinforcement cage is reversely inserted into the concrete to form a pile after the pile casing is lifted out;

and fourthly, providing a grouting pipe or a slender hammer, putting the prefabricated reinforced concrete pile body into the pile casing, and providing the pile casing for forming the pile.

In order to achieve the above object, another construction method of a concrete pile according to the present invention comprises the steps of:

1) performing construction of pile body hole forming at a pile position in a foundation, wherein the pile body hole forming mode comprises rotary drilling, diving drilling, impact drilling and down-the-hole drilling long spiral drilling;

2) after the hole is formed to the elevation of the pile bottom, a reinforcement cage is placed in the pile hole;

3) inserting more than one concrete guide pipe into the pile hole, and pouring concrete into the pile hole through the concrete guide pipes to reach the elevation of the pile top to form a concrete cast-in-place pile;

4) putting out a concrete guide pipe, and inserting more than one pile casing with a bottom sealing pile tip into the cast-in-place pile until the bottom end of the cast-in-place pile before the initial setting of the concrete;

5) according to soil property and upper load requirement, reinforcing treatment is carried out on the bottom end of the cast-in-place pile by one of the following methods:

firstly, inserting a grouting pipe with an injection head into a pile casing to the bottom end of a pile, pressurizing and injecting cement slurry into the grouting pipe, and simultaneously rotating and gradually sinking the grouting pipe downwards to improve the strength of soil mass in a certain range below the pile end to form a pile end curing carrier;

thirdly, solidifying the soil mass at the pile end and constructing a pile end carrier, namely inserting a grouting pipe with an injector head into a pile casing in the cast-in-place pile to the bottom end of the pile, pressurizing and injecting cement slurry into the grouting pipe, rotating and gradually sinking the grouting pipe downwards to improve the strength of the soil mass below the pile end within a certain range, then putting a slender hammer with the diameter smaller than that of the pile casing into the pile casing in the cast-in-place pile, filling a certain amount of cement sand mixture into the pile casing, tamping the cement sand mixture by the hammering kinetic energy of the slender hammer, and repeating the filling and tamping operations to further strengthen and compact the soil mass below the pile end within a certain depth and range to form the composite pile end carrier;

5) the pile body is processed and constructed by one of the following modes:

In order to achieve the above object, a third concrete pile construction method of the present invention includes the steps of:

1) performing construction of pile body hole forming at a pile position in a foundation, wherein the pile body hole forming mode comprises rotary drilling, diving drilling, down-the-hole drilling and long spiral drilling;

4) putting a concrete guide pipe, putting a slender hammer into a pile casing in a cast-in-place pile, filling a certain amount of cement-sand mixture into the pile casing, tamping the cement-sand mixture by using the hammering kinetic energy of the slender hammer, and repeating the filling and tamping operation to reinforce and compact the soil body in a certain depth and range below the pile end to form a pile end compact carrier;

5) continuously hammering the carrier in the protective cylinder by using a slender hammer, and gradually entering the carrier to a certain depth; or the slender hammer is used for continuously hammering the carrier to enter a certain depth and then the protective cylinder is pressed down to follow the carrier;

6) repeating the operation of the step 5), and stopping hammering when the slender hammer enters the carrier to reach the set depth;

7) a slender hammer is put forward, another reinforcement cage is sunk into the protective cylinder, and the bottom end of the reinforcement cage enters into the ramming hole of the carrier;

8) and pouring concrete in the pile casing to the elevation of the pile top, and lifting the pile casing to form the pile.

The construction method of the three concrete piles is that the construction of the concrete cast-in-place pile is firstly completed, and under the condition of keeping the integrity of a concrete pile body, the construction of pile end carriers in various forms is carried out, and the difference is that the first method is to preset a protective cylinder in a pile hole in advance in the concrete cast-in-place pile body to form the concrete cast-in-place pile taking the protective cylinder as a pore channel; the second method is that after the pile body is poured with concrete, a pile casing is inserted into the pile body to form a concrete pouring pile with the pile casing as a pore channel; the third method is to combine the reinforcement cage and the carrier sufficiently to improve the uplift resistance of the pile on the basis of the first method. The method to be selected in the concrete construction is determined according to the geological conditions of the project, the design parameter requirements of the upper load, the compression resistance, the pulling resistance, the bending resistance, the shearing resistance and the like of the building, the construction period and the like.

In the first and second concrete pile construction methods, reinforcement treatment is performed at the bottom end of the cast-in-place pile by one of three methods, wherein the first method for forming the pile end solidified carrier by high-pressure grouting is suitable for the condition that the soil layer at the pile end is not high in relative strength and the construction speed is relatively high; the second method for forming the pile end compact carrier through the filler tamping operation is suitable for the conditions that the soil layer at the pile end has higher relative strength and the bearing capacity of a single pile also has higher requirement; the third method of solidifying the pile end soil body first and then constructing the pile end carrier has the largest influence range of the pile end soil body and the highest relatively provided bearing capacity, is suitable for high-bearing capacity pile types with larger diameters and lengths and is suitable for more complicated geological conditions.

In the three concrete pile construction methods, preferably, the diameter of the pile casing or the total diameter of the arranged pile casings is smaller than the diameter of the reinforcement cage. In the large-diameter concrete cast-in-place pile, particularly over 1000mm, 2-3 pile casings can be sunk into a concrete pile body, and then the operations of filler tamping or high-pressure grouting are carried out in the pile casings simultaneously or respectively, so that the effects of saving equipment energy and improving construction efficiency can be achieved.

In the above three concrete pile construction methods, preferably, before the pile body hole-forming construction, the soil body with a certain depth and a larger diameter at the pile position is reinforced by cement stirring, so as to improve the strength of the pile body and the pile periphery and increase the shear resistance. For example, before a concrete pile with the diameter of 800mm is constructed, a soil body with the diameter of about 1500mm and the depth of 5m at the pile position is dug out, the dug soil body, cement and other curing agents are added with water and uniformly stirred to form fluid curing soil through ground mechanical equipment, then the fluid curing soil is poured back into an original pile hole, and operations such as hole forming, pile body concrete pouring and the like are carried out before the curing soil is solidified, so that the strength of the pile body at the middle and shallow part of the concrete pile is effectively improved, and higher shear resistance and lateral bending resistance are provided for the pile.

In the above three concrete pile construction methods, preferably, when there are a plurality of pile casings sunk, the filler tamping operation is performed simultaneously by a plurality of long and thin hammers of the same number in the plurality of pile casings, or the filler tamping operation is performed first in a certain pile casing and then the filler tamping operation is performed in other pile casings in sequence.

In the three concrete pile construction methods, the outer wall of the pile casing is preferably coated with a release agent including clear oil to facilitate later extraction of the pile casing.

In the three concrete pile construction methods, the concrete guide pipe is preferably inserted to the outside of the casing in the pile hole.

In the above three concrete pile construction methods, preferably, the cement-sand mixture is prepared by mixing cement and sand or crushed stone with small particle size or a mixture of the above materials with water. The cement sand mixture is adopted as the filler, the filler has small grain diameter, can smoothly fall into the bottom end of the pile casing from the gap between the slender hammer and the pile casing, realizes uninterrupted continuous work of the slender hammer, greatly improves the work efficiency, has good effect of sealing underground water during construction because the filler component of the cement mixture is a fine-grain hydrophilic substance with larger specific surface area, and simultaneously has cementing property so as to obviously enhance the carrier strength,

in the three concrete pile construction methods, preferably, the soil body below the pile end in a certain depth and within a certain range is reinforced and compacted, namely the soil body below the pile end in a depth of 3-5 m and within a diameter of 2-3 m is reinforced and compacted, and the construction ground is ensured not to bulge and the adjacent pile carrier is not damaged.

In the second and third modes of step 4) of the first and third methods or step 5) of the second method, after the filling and tamping operations are repeated, preferably, the density degree of the pile end carrier is controlled by using the penetration degree or the filling amount of three strokes, and the density degree of the carrier is controlled by using the penetration degree of three strokes: the number of times of subsidence after the long and thin hammer falls and is tamped when the long and thin hammer is not filled is one-hit penetration, three times of the penetration are measured continuously by the same falling distance and are three-hit penetrations, and the three-hit penetrations meet the following standards: the later penetration is less than or equal to the former penetration, the total value of the three-shot penetration is less than a design value, and the value range of the design value is 0-50 mm; the compactness of the carrier is controlled by the filling amount, which is that: and setting the filling amount of the filler according to the geological conditions and the bearing capacity, and completely filling and tamping the filler with the set amount.

In the three concrete pile construction methods, the operation of the step 4) is preferably omitted according to geological conditions and bearing capacity requirements, and the pile end soil body is tamped by directly utilizing the hammering kinetic energy of the long and thin hammer without filling materials. The method is suitable for soil layers with higher strength at the pile end, such as pebbles, sandstone layers and the like.

In the three concrete pile construction methods, preferably, in the operation process of the step 4) or the step 5), the pile casing is intermittently lifted and lowered or rotated left and right or vibrated, so that the outer wall of the pile casing and the surrounding concrete are prevented from being solidified and cemented under the long-time action, and the later period of the pile casing is facilitated to be provided.

The construction method of the concrete pile has the characteristics and advantages that:

the method is characterized by eliminating the common defects of pile bottom sediment of the concrete cast-in-place pile: the pile bottom sediment is the sediment with a certain thickness formed at the bottom of the pile hole by the friction touch of a hole forming machine and the hole wall and the hole bottom in the hole forming process, so that the sediment has the characteristics of multiple pores, coarse particles and non-saturation, and the problem of the pile bottom sediment is difficult to avoid no matter which hole forming modes, such as rotary drilling, diving drilling, impact drilling, down-the-hole drilling, long spiral drilling and the like are adopted, and the quality and the bearing capacity of the pile are seriously influenced. Aiming at the problem, the invention uses the free falling motion of the slender hammer to tamp the sediment at the bottom of the pile hole, and uses the principles of dynamic compaction and dynamic consolidation, under the tamping energy of the slender hammer, the sediment particles become smaller and the pores are reduced, and the sediment particles and the better soil body at the bottom of the pile are fully consolidated and compacted and consolidated with the soil body at the bottom of the pile into a whole, so the effect of eliminating the sediment is very obvious, and the effect of eliminating the sediment can be achieved by adopting the method of forming cement soil by high-pressure grouting at the bottom end of the pile.

Secondly, the respective advantages of the filling pile and the carrier pile are fully combined: the cast-in-place concrete pile is a commonly used conventional pile type, the hole forming and construction technology is mature, and the construction of the cast-in-place concrete pile can be carried out by hole forming methods such as rotary drilling, diving drilling, impact drilling, down-the-hole drilling, long spiral drilling and the like. The pile bearing capacity of the pile is derived from pile side friction and pile end resistance, the pile end resistance is not enough, the first pile side friction is easily influenced by pile bottom sediment, and the second pile side friction is not enough or even can generate negative friction when the pile body is in a soft soil layer, so that the whole bearing capacity of the pile is limited and the quality is unstable. On the basis of the concrete cast-in-place pile, the invention carries out subsequent construction of a plurality of carriers at the pile end by a reasonable and efficient technical means, fully exerts the technical advantages of the carrier pile, adopts filler tamping or high-pressure grouting to effectively reinforce the soil body with a certain depth and range at the pile end, can eliminate sediment, greatly improves the bearing capacity of a single pile, and has the effect of achieving twice the result with half the effort.

Thirdly, the bearing capacity of the pile end is obviously improved: the carrier is composed of rammed cement sand mixture, compacted soil and influenced soil, the strength and modulus are gradually reduced from inside to outside, the pressure of the load is gradually diffused in the process of transferring during stress, the carrier is equivalent to a multi-stage expanded foundation, the bearing capacity of the soil body of the pile end foundation is fully exerted, and the stress borne by the pile body is diffused, reduced and reduced layer by layer, so that the bearing capacity of the pile is obviously improved, the limit bearing capacity of the pile can be improved by 2-3 times compared with that of a common cast-in-place pile, a reinforcement cage extends into the carrier through the construction of the carrier, and when a single pile is subjected to uplift resistance, the uplift bearing capacity of the single pile can be improved by 1-2 times compared with that of the common pile due to the anchoring effect of.

And fourthly, various methods can be selected to carry out pile body pore-forming, pile body pouring and construction carrier, the application type and the application range are obviously improved, and the method is applicable to various soil layers and foundation forms.

The following table shows the comparison of the bearing capacity of a single pile after a carrier is added on the common cast-in-place pile and the pile end (without considering the ultimate strength of the concrete of the pile body, the bearing capacity of the single pile is in kN):

the geological properties of the pile body are as follows: the first layer is 1.5m of cohesive soil 2m of filling soil, and the lateral resistance is 28 kPa; the second layer is silty clay 3m, the side resistance is 30kPa, the third layer is cohesive soil 2.5m, the side resistance is 28kPa, the fourth layer is silty clay 3m, and the side resistance is 25 kPa.

When pile end holding power layer is cohesive soil, bearing capacity 190kPa, the contrast condition of single pile bearing capacity (kN):

diameter and classification	600mm	800mm	1000mm	1200mm
					Ordinary cast-in-place pile	870kN	1240kN	1660kN	2120kN
Pile end curing carrier	1230kN	1630kN	1980kN	2430kN
					Pile end compacting carrier	1640kN	1940kN	2240kN	2540kN
Pile tip curing and compacting carrier	1950kN	2300kN	2650kN	3000kN

When the pile end bearing layer is silt and the bearing capacity is 230kPa, the bearing capacity (kN) of a single pile is compared:

diameter and classification	600mm	800mm	1000mm	1200mm
					Ordinary cast-in-place pile	950kN	1390kN	1900kN	2470kN
Pile end curing carrier	1590kN	1920kN	2530kN	2960kN
					Pile end compacting carrier	2230kN	2640kN	3600kN	3940kN
Pile tip curing and compacting carrier	2600kN	3110kN	3890kN	4170kN

When the pile end bearing layer is sandy soil and the bearing capacity is 260kPa, the bearing capacity (kN) contrast condition of a single pile is as follows:

diameter and classification	600mm	800mm	1000mm	1200mm
					Ordinary cast-in-place pile	1230kN	1890kN	2660kN	3550kN
Pile end curing carrier	3230kN	3680kN	4020kN	5120kN
					Pile end compacting carrier	4070kN	4610kN	5720kN	6240kN
Pile tip consolidation and densificationSolid carrier	4240kN	5370kN	6500kN	7230kN

From the experimental data in the table, it can be seen that the better the soil property of the pile end bearing layer is, the larger the additionally increased bearing capacity of the pile end carrier is, and the higher the characteristic value of the bearing capacity of a single pile is.

Drawings

Fig. 1 is a process view showing an example of a method of constructing a concrete pile according to the present invention, which improves the compressive capacity of the pile by constructing a solidified carrier at the bottom end of the concrete pile.

Fig. 2 is a process diagram of a second embodiment of the method of constructing a concrete pile according to the present invention, which improves the compressive capacity of the pile by constructing a dense carrier at the bottom end of the concrete pile.

Fig. 3 is a process diagram of a third embodiment of the method of constructing a concrete pile according to the present invention, which improves the compression and uplift resistance of the pile by constructing a dense carrier at the bottom end of the concrete pile.

Fig. 4 and 5 are schematic cross-sectional views of a pile body of the concrete pile of the present invention during construction.

In fig. 1 to 5, 1 is a pore-forming drilling tool, 2 is a pile hole, 3 is a reinforcement cage, 4 is a casing, 5 is a concrete conduit, 6 is concrete, 7 is a grouting pipe, 8 is cement grout, 9 is a slender hammer, 10 is cement sand mixture, 11 is concrete poured for the second time, 12 is a second reinforcement cage, and 13 is a precast concrete pile.

Detailed Description

Fig. 1 is a process view showing an example of a method for constructing a concrete pile according to the present invention, which improves the compressive capacity of the pile by constructing a solidified carrier at the bottom end of the concrete pile. Firstly, as shown in a in fig. 1, digging out a soil body at a pile position in a foundation by a rotary drilling tool 1 to form a pile hole 2, wherein the diameter of the pile hole is 800 mm; then, as shown in b in fig. 1, after a hole is formed to reach the elevation of the pile bottom, a steel reinforcement cage 3 with the diameter of 700mm is placed in the pile hole 2, and a pile casing 4 with the diameter of 600mm is concentrically placed in the steel reinforcement cage 3; then, as shown in c in fig. 1, two concrete guide pipes 5 are inserted downwards into the pile hole 2 and the position outside the pile casing 4, and concrete 6 is poured into the pile hole through the concrete guide pipes 5 to reach the elevation of the pile top, so as to form a concrete poured pile with the pile casing 4 as a central hole; then, as shown in d in fig. 1, lifting the concrete guide pipe 5, inserting a grouting pipe 7 with a spray head into the pile bottom end in the pile casing 4 before the initial setting of the concrete 6, pressurizing and injecting cement slurry 8 into the grouting pipe 7, and simultaneously rotating left and right and gradually sinking the grouting pipe 7 downwards; then, as shown in e in fig. 1, repeating the operation of injecting the cement grout 8 under pressure while rotating left and right and gradually sinking into the grouting pipe 7, and if necessary, lifting up and then pressing down the grouting pipe 7 while grouting until the cement grout 8 is uniformly mixed with the soil body within the range of 1.2m of the lower diameter and 1.5m of the height of the pile end, so as to form a pile end solidified carrier with about 1.7m3 and remarkably improved strength; then, as shown in f in fig. 1, the grouting pipe 7 is lifted, the prefabricated reinforced concrete pile 13 with the diameter of 550mm is placed in the pile casing 4, and finally the pile casing 4 is lifted to form the pile. In the embodiment, the length of the pile is 18m, the diameter of the pile is 800mm, and the geological conditions are as follows: the pile top is located in a clay layer, the clay layer side resistance characteristic value is qsi =18kPa, the soil layer thickness is 3m from the pile top, a silt layer is below the clay layer, the silt layer side resistance characteristic value is qsi =25kPa, the thickness is 5m, a fine sand layer is below the silt layer, the pile end is located in the soil layer, the sand layer thickness is 21m, the sand layer side resistance characteristic value is qsi =35kPa, and the end resistance characteristic value qp =1250 kPa. The characteristic value of the side resistance of the concrete cast-in-place pile before the carrier is cured at the end of the un-constructed pile is 1328.85kN, the characteristic value of the end resistance is 628kN, and the total bearing capacity is 1956.85 kN; after the curing carrier is constructed at the bottom end of the concrete cast-in-place pile, the characteristic value of end resistance is improved to 2580 kN, the total bearing capacity is 3908.85kN, and the bearing capacity is improved by 99% compared with the end resistance.

Fig. 2 is a process diagram of a second embodiment of the method for constructing a concrete pile according to the present invention, which improves the compression and uplift resistance of the pile by constructing a dense carrier at the bottom end of the concrete pile. Firstly, as shown in a in figure 2, at a pile position in a foundation, soil is discharged through a diving drill 1 to form a pile hole 2, and the diameter of the pile hole is 1000 mm; then, as shown in b in fig. 2, after the hole is formed to the elevation of the pile bottom, a reinforcement cage 3 with the diameter of 800mm is placed in the pile hole 2, and a pile casing 4 with the diameter of 600mm is concentrically placed in the reinforcement cage 3; then, as shown in c in fig. 2, two concrete guide pipes 5 are inserted downwards into the pile hole 2 and the position outside the pile casing 4, and concrete 6 is poured into the pile hole through the concrete guide pipes 5 to reach the elevation of the pile top, so as to form a concrete poured pile with the pile casing 4 as a central hole; then, as shown in d in fig. 2, a concrete conduit 5 is lifted, a slender hammer 9 with the diameter of 500mm is placed in the pile casing 4, a small amount of cement sand mixture 10 is filled in the pile casing, the cement sand mixture 10 falls into the bottom end of the pile casing 4 through a gap between the slender hammer 9 and the pile casing 4, the slender hammer 9 is lifted for a certain height and then falls freely, and the hammering kinetic energy of the slender hammer 9 is utilized to ram the cement sand mixture 10; then, as shown in e in fig. 2, repeating the filling and tamping operation to strengthen and compact the soil body within a certain depth and range under the pile end to form a pile end compact carrier, wherein the compact carrier consists of cement sand mixture 10, compacted soil body and affected soil body from inside to outside; then, as shown in fig. 2 f, an elongated hammer 9 is proposed, and a reinforcement cage 12 having a diameter of 500mm is put into the casing 4; finally, as shown in g in fig. 2, pouring concrete 11 into the pile casing 4 to the height of the pile top, and lifting the pile casing 4 to form the pile. In this embodiment, the pile length is 15m, and the soil layer in the pile body scope is from top to bottom in proper order: layer clay with the thickness of 5.8m, wherein the characteristic value of resistance of the soil side of the layer is qsi =21 kPa; secondly, forming a layer of powdery clay with the thickness of 4.4m, wherein the characteristic value of the resistance of the soil side of the layer is qsi =24 kPa; ③ layer of silt with the thickness of 12.7m, wherein the layer of silt is fak =210kPa, the characteristic value of side resistance is qsi =25kPa, and the characteristic value of end resistance is qp =750 kPa. The bearing capacity characteristic value of the concrete filling pile before the carrier is not constructed is 1400 kN, after the dense carrier is constructed at the bottom end of the concrete filling pile, the bearing capacity characteristic value of the carrier pile is improved to 3600 kN, and compared with the bearing capacity of the carrier pile, the bearing capacity of the carrier pile is improved by 157%.

Fig. 3 is a process diagram of a third embodiment of the method for constructing a concrete pile according to the present invention, which improves the compression and uplift resistance of the pile by constructing a dense carrier at the bottom end of the concrete pile. Firstly, as shown in a in fig. 3, digging out a soil body at a pile position in a foundation by a rotary drilling tool 1 to form a pile hole 2, wherein the diameter of the pile hole is 800 mm; then, as shown in b in fig. 3, after a hole is formed to reach the elevation of the pile bottom, a reinforcement cage 3 with the diameter of 650mm is placed in the pile hole 2, and a pile casing 4 with the diameter of 580mm is placed in the reinforcement cage 3; then, as shown in c in fig. 3, two concrete guide pipes 5 are inserted downwards into the pile hole 2 and the position outside the pile casing 4, and concrete 6 is poured into the pile hole through the concrete guide pipes 5 to reach the elevation of the pile top, so as to form a concrete poured pile with the pile casing 4 as a central hole; then, as shown in d in fig. 3, a concrete conduit 5 is lifted, a slender hammer 9 with the diameter of 460mm is placed in the pile casing 4, a small amount of cement sand mixture 10 is filled in the pile casing, the cement sand mixture 10 falls into the bottom end of the pile casing 4 through a gap between the slender hammer 9 and the pile casing 4, the slender hammer 9 is lifted for a certain height and then falls freely, and the hammering kinetic energy of the slender hammer 9 is utilized to ram the cement sand mixture 10; then, as shown in e in fig. 3, repeating the filling and tamping operation to strengthen and compact the soil body within a certain depth and range under the pile end to form a pile end compact carrier, wherein the compact carrier consists of cement sand mixture 10, compacted soil body and affected soil body from inside to outside; then, as shown in f in fig. 3, continuously hammering the carrier downwards in the casing 4 by using the slender hammer 9 without filling, and gradually entering the carrier to a certain depth to form a ramming hole, and stopping hammering when the depth of the slender hammer 9 in the ramming hole in the carrier reaches 80 mm; then, as shown in g in fig. 3, an elongated hammer 9 is proposed, and another reinforcement cage 12 is sunk in the casing 4, and the bottom end of the reinforcement cage 12 enters into the ramming hole of the carrier; finally, as shown in h in fig. 3, pouring concrete 11 into the pile casing 4 to the height of the pile top, and lifting the pile casing 4 to form the pile. In this embodiment, the pile length is 16m, and the soil layers within the pile body range are from top to bottom: layer clay with the thickness of 3.6m, wherein the characteristic value of resistance of the soil side of the layer is qsi =20 kPa; secondly, forming a layer of powdery clay with the thickness of 4.2m, wherein the characteristic value of the resistance of the soil side of the layer is qsi =22 kPa; thirdly, the thickness of the layer of silt is 5.5m, and the characteristic value of the resistance of the soil side of the layer is qsi =23 kPa; a layer of fine sand with the thickness of 11.2m and the thickness of fak =240kPa, wherein the layer soil side resistance characteristic value qsi =26kPa, and the end resistance characteristic value qp =800 kPa. Before constructing the carrier, the compression bearing capacity characteristic value of the concrete cast-in-place pile is 1300kN, and the uplift bearing capacity characteristic value is 690 kN; after the dense carrier is constructed at the bottom end of the concrete cast-in-place pile, the characteristic value of the compressive bearing capacity of the carrier pile is improved to 4610 kN, the characteristic value of the uplift bearing capacity is improved to 1420 kN, and the compressive bearing capacity and the uplift bearing capacity are respectively improved by 254% and 105%.

Fig. 4 is a cross-sectional view of a pile body of the concrete pile of the present invention during construction using fig. 2 as an example. As shown in fig. 4, the concrete pile body 6 includes a reinforcement cage 3, an inner ring of the reinforcement cage 3 includes a casing 4, and the casing 4 includes a slender hammer 9 capable of moving up and down.

Fig. 5 is a schematic cross-sectional view of a pile body during construction of another embodiment of the concrete pile of the present invention. As shown in fig. 5, the concrete pile body 6 includes a reinforcement cage 3, the inner ring of the reinforcement cage 3 includes three closely attached casing 4, and each casing 4 includes a slender hammer 9 capable of moving up and down.

The above embodiments are illustrative only and not restrictive, and the scope of the invention is not to be limited thereto, and various changes and modifications in other forms can be made on the basis of the above description and are within the scope of the invention.

Claims

1. A construction method of a concrete pile is characterized in that the construction of a concrete pile body is firstly completed, and then a pile end carrier is constructed, wherein the method comprises the following steps:

5) the pile body is processed and constructed by one of the following modes:

2. A construction method of a concrete pile is characterized in that a concrete pile body is constructed first, and then construction of a pile end carrier is completed, wherein the method comprises the following steps:

5) the pile body is processed and constructed by one of the following modes:

3. A construction method of a concrete pile is characterized in that a concrete pile body is constructed first, and then construction of a pile end carrier is completed, wherein the method comprises the following steps:

7) a slender hammer is put forward, a second reinforcement cage is sunk into the protective cylinder, and the bottom end of the reinforcement cage enters into the ramming hole of the carrier;

4. A method for constructing a concrete pile according to claim 1, 2 or 3, wherein in the step 2), the diameter of the pile casing or the total diameter of the pile casings after being arranged is smaller than the diameter of the reinforcement cage.

5. The method for constructing concrete pile according to claim 1, claim 2 or claim 3, wherein before the hole-forming construction of the pile body, the soil body with a certain depth and a larger diameter at the pile position is reinforced by cement stirring to improve the strength of the pile body and the pile periphery and increase the shear resistance.

6. A method of constructing a concrete pile according to claim 1, 2 or 3, wherein in the step 2), when there are a plurality of sinking casings, the same number of long and thin hammers are used to simultaneously tamp the filler in the plurality of casings, or the filler is tamped in a casing and then sequentially tamped in other casings.

7. A method of constructing a concrete pile according to claim 1, claim 2 or claim 3, wherein in step 2) the outer wall of the casing is coated with a release agent such as bitumen to facilitate later extraction of the casing.

8. A method of constructing a concrete pile according to claim 1, claim 2 or claim 3, wherein said concrete guide pipe in said step 3) is inserted into the outer side of the pile casing in the pile hole.

9. A method of constructing a concrete pile according to claim 1, claim 2 or claim 3, wherein said cement-sand mixture of step 4) is obtained by mixing cement and sand or crushed stone of small particle size or a mixture of said materials with water.

10. The method for constructing a concrete pile according to claim 1, claim 2 or claim 3, wherein said step 5) of compacting the soil mass at a depth and range below the pile tip means that the soil mass at a depth of 3 to 5m and a diameter of 2 to 3m below the pile tip is compacted and compacted, and it is ensured that the construction ground does not swell and the adjacent pile carrier does not break.

11. The method for constructing a concrete pile according to claim 1, claim 2 or claim 3, wherein in the means (5) and (iii), after the operations of filling and tamping are repeated, the density of the pile end carrier is controlled by using the penetration or the amount of the filling material, and the density of the carrier is controlled by using the penetration: the number of times of subsidence after the long and thin hammer falls and is tamped when the long and thin hammer is not filled is one-hit penetration, three times of the penetration are measured continuously by the same falling distance and are three-hit penetrations, and the three-hit penetrations meet the following standards: the later penetration is less than or equal to the former penetration, the total value of the three-shot penetration is less than a design value, and the value range of the design value is 0-50 mm; the density of the carrier is controlled by adopting the filling material amount: and setting the filling amount of the filler according to the geological conditions and the bearing capacity, and completely filling and tamping the filler with the set amount.

12. A method for constructing a concrete pile according to claim 1, 2 or 3, wherein the operation of step 4) is omitted according to geological conditions and bearing capacity requirements, and neither filler is directly used for ramming the soil mass at the pile end by using the hammering kinetic energy of the long and thin hammer.

13. A method for constructing a concrete pile according to claim 1, claim 2 or claim 3, wherein the pile casing is intermittently lifted or lowered, or rotated or vibrated during the step 4) or step 5) to prevent the outer wall of the pile casing from being cemented with the surrounding concrete over a long period of time.