CN115897563A - Steel-concrete composite pile, preparation method of steel-concrete composite pile and application of steel-concrete composite pile - Google Patents
Steel-concrete composite pile, preparation method of steel-concrete composite pile and application of steel-concrete composite pile Download PDFInfo
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Abstract
The invention provides a steel-concrete composite pile, a preparation method of the steel-concrete composite pile and application of the steel-concrete composite pile, wherein the steel-concrete composite pile comprises a steel pipe pile positioned above water and a concrete large pipe pile positioned below water, the steel pipe pile and the concrete large pipe pile are connected through a connecting section, and a steel pile shoe is arranged on one side of the large pipe pile, which is far away from the steel pipe pile; the linkage segment both sides are provided with the flange that is used for connecting steel-pipe pile and concrete large-scale pile respectively, and are close to the flange of concrete large-scale pile department, act on simultaneously concrete large-scale tubular pile produces the prestressing force, concrete large-scale tubular pile includes that a plurality of adopts C60 or C70 hard concrete to pour the tube coupling that forms through centrifugal vibration roll-in composite technology, cooperation reinforcing bar hole spiral muscle and longitudinal reinforcement. The steel-concrete composite pile combines the advantages of low manufacturing cost of the concrete pipe pile and good bending resistance of the steel pipe pile, and achieves the purpose of reducing the cost on the premise of meeting the engineering quality requirement.
Description
Technical Field
The invention relates to the technical field of steel pipe composite piles, in particular to a steel-concrete composite pile, a preparation method of the steel-concrete composite pile and application of the steel-concrete composite pile.
Background
The scheme of driving piles in the sea-crossing bridge pile foundation is widely applied. According to different water depth, flow velocity, wave, geology and other environmental conditions, the pile types such as the steel pipe pile, the large-diameter prestressed concrete pipe pile and the like can be adopted. The steel pipe pile has the characteristic of strong bending resistance, and the prestressed concrete large pipe pile has the characteristics of low manufacturing cost and good durability.
However, due to the existing deep water wharf berths and sea-crossing bridges, when the prestressed concrete large pipe piles (hereinafter referred to as large pipe piles) are used for arranging the inclined piles in deeper water areas, the existing prestressed concrete large pipe piles appear to have insufficient bending resistance under the action of water flow, waves and the dead weight of the pipe piles. Due to the limitation of self bending resistance, large prestressed concrete pipe piles and other concrete pipe piles cannot be used for deep water wharfs and bridge engineering in marine environments to replace steel pipe piles in a larger range. Therefore, the technical scheme of the pile foundation adopting the prestressed concrete pipe pile is abandoned in different engineering stages in domestic famous projects such as Shanghai deep water harbors, east China sea bridges, hangzhou Bay bridges and the like in Shanghai international shipping centers, and the technical scheme of the large-diameter steel pipe pile is adopted instead, so that the construction cost is increased.
In the prior art, part of the disclosed steel-concrete composite piles have the technical performance reaching the application range of steel pipe piles, are low in cost and have high economic and social benefits
The length of the large tubular pile body and the steel pile combined pile is longer and longer, the hammer type and the hammer energy selected for pile sinking of the large tubular pile are larger and larger, and under the action of adverse factors such as water flow, waves, eccentric hammering and the like, the compressive stress borne by the pile body during pile sinking possibly exceeds the design value of the compressive stress of C60 or C70 concrete of the tubular pile, so that the tubular pile is damaged; and the degree of automation of individual production processes of the large tubular piles is low, so that the production cost of the product is high, and the market competitiveness is not strong.
Disclosure of Invention
The invention aims to provide a steel-concrete composite pile, a preparation method of the steel-concrete composite pile and application of the steel-concrete composite pile.
In order to achieve the purpose, the invention is realized by the following technical scheme.
The reinforced concrete composite pile comprises a steel pipe pile positioned above water and a large concrete pipe pile positioned below water, wherein the steel pipe pile and the large concrete pipe pile are connected through a connecting section, and a steel pile shoe is arranged on one side of the large pipe pile, which is far away from the steel pipe pile; flanges for connecting the steel pipe pile and the concrete large pipe pile are respectively arranged on two sides of the connecting section, the flanges close to the concrete large pipe pile act on the concrete large pipe pile simultaneously, and prestress is generated; the large concrete pipe pile comprises a plurality of pipe joints which are formed by pouring reinforcing steel bar hole spiral bars and longitudinal reinforcing steel bars by adopting a C60 or C70 dry and hard concrete through a centrifugal vibration rolling composite process, wherein in the plurality of pipe joints, the section of each pipe joint is at least provided with 16 preformed holes, and the preformed holes far away from the direction of the steel pipe pile are connected with the steel pile shoe through an anchorage device along the length direction of the large concrete pipe pile.
Further, from the steel pipe pile to the direction of the concrete large pipe pile, the connecting section sequentially comprises a steel anchor ear, a rectangular stiffening plate and a triangular stiffening plate.
Further, as seen from the cross-sectional view, the rectangular stiffening plates are circular rings, the circumference of each circular ring is symmetrically divided into a plurality of rectangular stiffening plates, and concrete is filled in the rectangular stiffening plates.
Further, the thickness of the triangular stiffening plate is not less than 15mm.
The invention also discloses a preparation method of the steel-concrete composite pile, which is characterized by comprising the following steps of:
preparing a concrete large pipe pile: the method sequentially comprises the steps of installing a steel reinforcement cage, installing a template, pouring the steel pipe pile, steaming, removing the template and performing water curing, wherein C60 or C70 hard concrete is selected for pouring the steel pipe pile;
preparing the steel pipe pile: the method comprises the following steps of (1) selecting steel to manufacture the steel pipe pile, coating an anticorrosive paint layer on the outer layer of the steel pipe pile, arranging modified epoxy glass flake heavy anticorrosive paint at the bottom of the anticorrosive paint layer, and arranging acrylic polyurethane paint on the anticorrosive paint layer;
installing a connecting section: welding the connecting sections between the adjacent steel pipe piles and between the steel pipe piles and the large pipe pile;
welding the steel pile shoe: and welding the steel pile shoe to the side part of the large tubular pile.
Furthermore, the preparation of the large tubular pile further comprises the step of pulling steel strands, and the steps of brushing the adhesive, completing secondary tensioning and splicing, hoisting, pressing slurry, welding the steel cladding plate, lengthening the steel pile shoe and welding the stiffening plate sequentially comprise.
Further, during the preparation of the steel pipe pile, the method further comprises the step of assembling a sacrificial anode, specifically, the sacrificial anode is installed and fixed by adopting an underwater dry welding method, and the iron core of the sacrificial anode is made of deformed steel.
Furthermore, during installation of the connecting sections in the step, triangular stiffening plates are arranged along the circumferential direction at the joints of the adjacent steel pipe piles and the joints of the steel pipe piles and the large pipe piles, the thickness of each triangular stiffening plate is 12-18mm, and the height of each triangular stiffening plate is 400-600mm.
The invention also discloses the application of the steel-concrete composite pile in foundation conditions of fine sand, silt sand, medium coarse sand, silt clay, silty clay, sandy clay, gravel sand, dense sand or weathered rock.
Further, the application comprises hoisting of the steel-concrete composite pile, and the hoisting is six-point hoisting or four-point hoisting.
The invention has the following beneficial effects:
according to the invention, the steel connecting section plays a transitional buffer role in changing the section of the composite pile structure from the section of the steel pipe pile to the section of the large pipe pile, so that the nonuniformity of stress distribution in the hammering stress transfer process is reduced, and the stress characteristic of concrete near a joint is greatly improved.
According to the invention, the large pipe pile is formed by pouring C60 or C70 hard concrete produced by a centrifugal vibration rolling composite process in cooperation with a reinforcing steel bar hole spiral rib and a longitudinal reinforcing steel bar, the section of the pipe section is at least provided with 16 preformed holes, and the preformed holes are connected with the steel pile shoe through an anchorage device along the length direction.
In the invention, the upper part and the lower part are respectively made of different materials as pile foundation materials, and the upper steel pile has the characteristic of strong bending resistance and can well meet the bending resistance requirement on the pile foundation; the lower prestressed concrete large pipe pile fully exerts the advantages of large vertical bearing capacity and low price, and the advantages are combined and complemented. In view of structural durability, although the steel pipe pile is arranged above a mud surface, mature anti-corrosion engineering measures can be taken, the structural durability requirement is easily met, the concrete pipe pile has better durability in a seawater environment, and the concrete pipe pile is arranged below an embedding point and isolated from air, so that the corrosion rate is extremely slow. Therefore, the steel-concrete composite pile can meet the requirement on structural durability. The novel steel-concrete composite pipe pile also solves the bottleneck problem that the use of a large pipe pile is influenced due to the insufficient hoisting capacity of a pile driving barge. The novel steel-concrete composite pipe pile is used for replacing a steel pipe pile, and the engineering cost is greatly reduced.
The invention has the following beneficial effects:
the steel-concrete composite pile is a new pile type which reasonably combines a prestressed concrete pipe pile and a steel pipe pile according to the environment of the engineering, combines the advantages of low manufacturing cost of the concrete pipe pile and good bending resistance of the steel pipe pile, and achieves the purpose of reducing the cost on the premise of meeting the engineering quality requirement.
In the invention, compared with the steel pipe pile, the cost of the single steel-concrete composite pile can be saved by 13.4 ten thousand yuan, the cost is reduced by about 38%, and the steel-concrete composite pile has larger economic benefit compared with the steel pipe pile.
In the invention, the bending resistance of the upper part of the steel-concrete composite pile is equivalent to that of the steel pipe pile, the application bottleneck of insufficient bending resistance of the prestressed concrete large pipe pile is broken to a certain extent, and the application of the prestressed concrete pipe pile in related engineering can be expanded; compared with the corresponding steel pipe pile, the steel-concrete composite pile designed according to the method has higher cost performance, the cost is reduced by 35-38% in the calculation example of the chapter, and the steel-concrete composite pile for the engineering pile foundation in the open sea deep water area can be used for replacing the steel pipe pile, so that considerable economic benefit and social benefit can be generated.
Drawings
Fig. 1 is a schematic structural diagram of a steel-concrete composite pile provided by the invention;
fig. 2 is a schematic structural view of a large tubular pile provided by the invention;
FIG. 3 is a schematic structural view of a steel pipe pile according to the present invention;
FIG. 4 is a schematic structural diagram of a sacrificial anode provided by the present invention;
in the figure:
100. steel pipe piles; 200. a connection section; 300. concrete large pipe piles; 400. a steel pile shoe; 500. a sacrificial anode.
Detailed Description
The present invention is described in detail with reference to the embodiments shown in the drawings, but it should be understood that these embodiments are not intended to limit the present invention, and those skilled in the art should understand that functional, methodological, or structural equivalents or substitutions made by these embodiments are within the scope of the present invention.
Example 1
In the present embodiment, the main cases are mainly described.
Referring to fig. 1-4, the steel-concrete composite pile of the present invention is divided into four parts, namely, a steel pipe pile 100, a connecting section 200, a concrete large pipe pile 300, and a steel pile shoe 400.
In practical applications, a steel-concrete composite pile of a certain specification is taken as an example for introduction.
In the application, the steel-concrete composite pile mainly comprises two pile bodies, the lower part is a prestressed concrete large pipe pile, the upper part is a steel pipe pile, and a connecting section is arranged between the steel pipe pile and the concrete large pipe pile. The long 500mm of connection section comprises steel pipe, rectangle stiffening plate, tip flange board and steel clad plate: the inner diameter of the steel pipe is 910mm, and the wall thickness is 22mm; the rectangular stiffening plate is 25mm thick, 16 pieces in number and is arranged in an equal circumference way; the thickness of the end flange plate is 32mm, the outer diameter of the steel clad plate is 1200mm, and the wall thickness is 6mm.
Further, the large tubular pile 300 of the present invention requires the following structure:
the concrete large pipe pile adopts a D1200B32-2 type and is provided with a plurality of pipe joints, and the length of each pipe joint is 4 meters. Stretching the prestressed reinforcement between the pipe joints by brushing an epoxy adhesive; the pipe joint is prepared by a C60 or C70 dry hard concrete centrifugal vibration rolling composite process, specifically, 16 reserved holes with the diameter of phi 40mm are arranged on the section of the pipe joint, the outer wall protective layer of each hole is 52.5mm in each reserved hole, and the inner wall protective layer of each hole is 52.5mm.
In the invention, the length of the concrete large pipe pile 300 is 1.5-2 times of the length of the steel pipe pile 100, the displacement of the pile top is gradually increased in the horizontal external load of 0-80kN, and the maximum bending moment of the pile body is about 1060 kN.m.
Still include the reinforcing bar in the coupling, specifically include steel reinforcement cage spiral muscle and longitudinal reinforcement, all adopt 8mm cold drawing to 7mm in the HPB 235. The strength of the cement paste for grouting the preformed hole is not less than 40MPa; the tubular pile divides the post top section, and two kind pile top festival annular muscle intervals of basic section are 50nm, and basic festival annular muscle is 50mm in the 1 meter scope in both ends, and the rest is 100mn, and pile top festival tip is equipped with the steel sheet hoop. The quality of the pipe pile is 10mm according to the height of the fillet weld seam of the steel pile shoe, and 8mm of the ribbed plate; the A surface is provided with machining allowance to ensure that the plate is 20nm thick and the unevenness is less than or equal to 2mm; the steel plate hoop length of the steel plate hoop is 3753+2nm, and the roundness of the steel plate hoop is not allowed to have local mutation.
Referring to fig. 3, the steel pipe pile of the present invention requires the following:
the steel plate is made of 345 steel, and straight welding seams are adopted.
And (3) manufacturing the steel pipe pile, wherein the steel plate meets the design requirement and has delivery qualification certificate, and the surface of the steel pipe pile is free from defects such as cracks, bubbles, scaling and the like or defects such as interlayers and the like. After the appearance inspection of the steel pile welding line is qualified, internal flaw detection inspection should be carried out on the butt welding line, 2% of X-ray shooting is required, and 100% of ultrasonic inspection is required; and after the appearance inspection of the welding line of the lifting ring is qualified, performing ultrasonic inspection on the welding line by 100 percent. And (4) corrosion prevention of the steel pile, namely removing rust on the surface to S.2.5 grade, coating with anticorrosive paint, and meeting the service life of more than 20 years after corrosion prevention. The bottom layer of the anticorrosive paint adopts modified epoxy glass flake heavy anticorrosive paint, and the thickness of a dry film is more than or equal to 700 mu m; the surface layer is made of acrylic polyurethane paint, and the thickness of the dry film is more than or equal to 100 mu m.
Referring to FIG. 4, the invention further includes sacrificial anodes installed and fixed by underwater dry welding, the size of the anodes is 1250x (115 + 135) x130, the gross weight is 56 kg/piece, 2 pieces/pile, and the total number is 80 pieces.
In the installation of the sacrificial anode, the specific operation and technical requirements are as follows:
(1) The length of each welding line of the welding leg is required to be more than 80mm, and the height of each welding line is not less than 4mm;
(2) The anode is firmly welded without the phenomena of insufficient solder and false solder, and the surface of the anode is strictly prohibited from being contaminated by oil stains in the transportation and construction processes;
(3) The sacrificial anode is made of high-efficiency aluminum-zinc-indium-magnesium-titanium alloy, the iron core is made of deformed steel bar, and the welding leg is made of 235;
(4) The anode is fixed on the accessory of the steel pipe pile, and the anode block is ensured not to fall off.
Wherein the large tubular pile 300 adopts a D1200B32-2 type, and the length of each pipe joint is 4 meters. The pipe sections are divided into two types of pile top sections and basic sections, and the end plates of the pile top sections are provided with steel plate hoops. The required pile length is spliced among the pipe joints by coating epoxy adhesive, tensioning prestressed steel strands and a grouting process in the reserved holes, the pile top direction is anchored with the steel-concrete connecting section through 16 OVM anchorage devices, and the pile tip direction is anchored with a 0.5m steel pile shoe through 4 OVM anchorage devices.
In the invention, the internal and external stress distribution of the concrete pipe pile is not uniform in the existing connecting part, and in order to reduce the non-uniformity, a connecting section 200 consisting of a rectangular rib plate and an internal and external coated steel pipe is additionally arranged below the original connecting part, specifically, in the embodiment, a steel pipe pile with the length of 1m is selected, the pipe pile connecting part forming the connecting section 200 is 0.5m long, and a concrete large pipe pile consisting of the concrete pipe pile is 0.5m long. The outer diameter of the upper steel pipe pile is 1200mm, and the wall thickness is 16mm; the thickness of the triangular rib plates (total 16 ribs) is 16mm, the length is 500mm, and the width is 129mm. The thickness of a connecting part flange is 302mm, the outer diameter is 1200mm, and the inner diameter is 910mm; the thickness of each rectangular rib plate (16 in total) is 25mm, the length is 500mm, and the width is 116mm; the inner diameter of the inner layer steel pipe is 910mm, and the wall thickness is 25mm; the outer diameter of the outer layer steel pipe is 1200mm, and the wall thickness is 6mm. The outer diameter of the lower concrete pipe pile is 1200mm, and the inner diameter is 910mm.
Improve novel joint structure, the inlayer steel pipe is 25mm, increases outer steel pipe thickness and is 6mm, increases flange plate thickness simultaneously and is 32mm, and under pile driving stress was the 140MPa circumstances, the tensile and the compressive strength of the near concrete of joint all satisfied the strength requirement.
According to the invention, the upper load can be effectively transferred by filling concrete between the rectangular reinforced slabs, so that the upper load is more uniformly distributed on the top of the concrete tubular pile, the first principal stress and the third principal stress of the concrete tubular pile and the maximum Mises stress value on the steel tubular pile are obviously reduced, the composite pile has more safety reserves, and the application range of the composite pile is expanded.
In the invention, a triangular stiffening plate is additionally arranged between the steel pipe pile 100 and the connecting section 200 for reinforcement, and the triangular stiffening plate is formed by reinforcing plates, wherein the thickness of each reinforcing plate is 16mm, the width of each reinforcing plate is the same as that of an annular end plate of the pipe pile, the height of each reinforcing plate is more than or equal to 500mm, and the number of the reinforcing plates is more than or equal to 16. Considering that the composite pile is gradually changed into the cross section of the concrete pipe pile from the cross section of the steel pipe pile through the connecting section, the stress distribution condition is complex in the hammering pile sinking process, and the welding seam quality is required to be ensured.
When the invention is used for lifting sinking piles, a reinforcing inner ring is arranged in the steel pipe pile 100 on the pile top, the width is 500mm, and the wall thickness is 20mm. When the four-point hoisting is adopted, 1 hoisting ring is welded at the position of the steel pipe pile 19 meters away from the pile top, and 1 hoisting ring is welded at the position of 24 meters back-off from the pile top after the steel pipe pile is turned by 180 degrees; when the six-point hoisting is adopted, 2 hoisting rings are welded at the positions 16m and 26 m away from the pile top of the steel pipe pile, and 1 hoisting ring is welded at the position 24 m away from the pile top by rotating 180 degrees.
In the embodiment, the steel pile shoe 400 at the end is specifically provided with a cylinder body with the inner diameter of 910mm, the wall thickness of 16mm and the length of 500mm. The unevenness of the inner side surface of the flange ring close to the concrete pipe joint is not more than 2mm, and the thickness of the plate is ensured to reach 20mm by the machining allowance. And 8 triangular stiffening plates are used for reinforcing the cylinder body and the flange ring, and the thickness of each stiffening plate is 14mm.
In the invention, the flange at the lower part is simultaneously used as an end plate of the concrete large tubular pile 300, prestress can be applied to the concrete large tubular pile 300 through the flange, the steel cladding plate is connected with the concrete large tubular pile 300 into a whole under the condition of retaining an anchorage device, and the steel cladding plate simultaneously plays a role of sealing the anchorage device; the upper flange is connected with the end of the steel pipe pile 100 into a whole by welding, thereby forming a complete steel-concrete composite pile.
The manufacturing process flow of the steel-concrete composite pile comprises the following steps:
(1) roll welding of a steel reinforcement cage → installation of the steel reinforcement cage → mold assembly → pipe section molding → steam curing → mold disassembly → water curing → stacking yard to be spliced;
(2) manufacturing a steel-concrete connecting section → manufacturing a steel pipe pile → welding the steel-concrete connecting section and the steel pipe pile;
(3) the steel pile shoe is welded with a flange ring and a cylinder body with the width of 10cm, so that the requirement of a single-end tensioning process is met;
(4) the method comprises the steps of steel pipe pile, concrete pipe joint and steel pile shoe local steel strand penetrating → adhesive brushing → secondary tensioning and splicing → hoisting → slurry pressing → steel ladle plate welding, steel pile shoe lengthening and reinforcing plate welding → slurry is hoisted to a storage yard according to the requirement.
Furthermore, the joints of the steel pipe piles are positioned at the joints, epoxy adhesive is coated, tension prestressed steel strands are laid, and grouting liquid is filled in the joints.
According to the invention, the steel-concrete composite piles are spliced in the special pile splicing pedestal area, and the special splicing trolley is used as a splicing jig frame. The work is carried out in two stages. The first stage is splicing pile formation of the concrete large pipe pile, and a post-tensioning process is adopted to splice a steel pile tip, a large pipe pile pipe joint and a steel connecting section into a pile; and the second stage is the whole steel-concrete composite pile splicing, and a steel structure welding process is adopted to form the whole steel-concrete composite pile structure.
Compared with the steel pipe pile, the steel-concrete composite pile has the following advantages:
(1) The manufacturing cost is low, the steel consumption is less (the manufacturing cost of the steel pipe pile with the same length is about 2 to 3 times of that of the prestressed concrete pipe pile with the same diameter);
(2) The steel pipe pile must adopt special anti-corrosion measures such as coating or cathodic protection in a seawater environment, and the large pipe pile and the PHC pipe pile have good chlorine salt corrosion resistance in a marine environment, and do not need other protection measures under general conditions, so that the construction and maintenance cost is greatly reduced.
The application of the large tubular pile and the PHC/SPHC tubular pile in the deep sea area has certain superiority, has obvious economic benefit when being used for replacing a steel pipe pile, is determined by people in domestic and foreign industries, is often taken as a preferred pile type of a high-pile wharf, is popularized and applied in a large range in coastal wharfs in east China and south China and bridge engineering, and obtains good engineering effect and social and economic benefit.
The bending resistance of the new steel-concrete composite pile formed by combining the prestressed concrete large pipe pile and the steel pipe pile is equivalent to that of the steel pipe pile, and the application bottleneck that the bending resistance of the prestressed concrete large pipe pile is insufficient is broken to a certain extent. The application of the reinforced concrete composite pile in related engineering is enlarged, and the cost of pile foundation engineering can be greatly saved. According to the market price measurement at the present stage, the cost of the D1200B1-1 type large pipe pile is 1650 yuan less than that of a steel pipe pile with the phi 1200 wall thickness of 20mm per meter, the cost of the structure increase of the anchoring connection part is deducted, and the cost of the pile foundation begins to be reduced when the replacement length is more than 6.5 m. When more than 3000 steel pipe piles are needed in a project and the pile length is 60 to 70 meters, if a steel-concrete composite pile can be used for replacing the steel pipe pile, the saving situation of the engineering cost can be roughly calculated as follows (assuming the diameter is 1.2 m):
the average pile length is 65m, the average water depth is 15m, the length of the large pipe pile replacing the steel pipe pile is 35m, the cost of each steel-concrete pile is saved by at least 3.8 ten thousand yuan compared with the cost of the steel pipe pile, and the economic benefit is more than 1.1 million yuan RMB and is very considerable.
Example 2
In this embodiment, the description is mainly given with reference to specific applications.
The steel-concrete composite pile has various forms, namely a section of steel pipe pile is anchored on the upper part of a large pipe pile through a special joint to form a composite pipe pile, and the composite pipe pile is a CSC pile type consisting of large pipe piles at two ends and a middle steel pipe pile.
In order to further understand the steel-concrete composite pile, the formed steel-concrete composite pile is further researched, and the concrete steps are as follows:
(1) The steel-concrete composite pile is applied to research and develop system investigation, and the varieties and application conditions of various steel pipe-prestressed concrete pipe pile composite piles are summarized and combed.
(2) The adaptability research of the steel-concrete composite pile researches a design method and driving performance analysis of the steel-concrete composite pile according to engineering examples of various steel-concrete composite piles, discusses feasibility of establishing a specification table of the steel-concrete composite pile, and analyzes application conditions and an application range of the steel-concrete composite pile under various working conditions.
(3) Design and calculation of hanging pile of steel-concrete composite pile
Theoretical calculation and test are carried out on the design, stress distribution, deformation and the like of the lifting point when each composite pile lifts the pile, and the design calculation method of the composite pile lifts the pile, which accords with the actual engineering, is summarized.
(4) The test technology research of the steel-concrete composite pile is combined with engineering practice, and the method for testing the integrity of the pile body of the steel-concrete composite pile is summarized through tests.
(5) And analyzing the comprehensive economic cost of the steel-concrete composite pile by combining the comprehensive economic cost analysis with the research foundation.
First part, structural design and Properties of Steel-concrete composite pile
The invention also researches the design method and the driving capability of the steel-concrete composite pile, analyzes the application condition and the application range of the steel-concrete composite pile and discusses the feasibility of establishing the specification table of the steel-concrete composite pile.
First, the study of the design method of the steel-concrete composite pile
1) Wall thickness of steel pipe pile
(1) The equal-rigidity steel-concrete composite pile is a new pile type formed by combining a prestressed concrete pipe pile and a steel pipe pile together, and in order to meet the continuity conditions of structural deformation such as pile foundation processing and hoisting, the whole bending rigidity of the pile body is required to be consistent under an ideal state, namely the bending rigidity of the concrete pipe pile is equal to that of the steel pipe pile:
E s I s =E c I c (formula one)
In the formula: e s The elastic modulus (MPa) of the steel pipe pile material;
I s the inertia moment (m 4) of the cross section of the steel pipe pile to the central shaft;ccssIEIE= sEsI
E c modulus of elasticity (MPa) of concrete tubular pile material
I c And the inertia moment (m 4) of the cross section of the concrete pipe pile to the central shaft.
According to the formula as a theoretical basis, the calculation and research finally result in that: for the condition of equal bending rigidity, the wall thickness difference of the steel pipe piles corresponding to the large pipe piles with the same diameter is less than 0.5mm, so that the uniform wall thickness can be adopted for the steel-concrete composite piles with the same diameter, and the type selection is convenient.
(2) Structural design requirements
The steel pipe pile in port engineering needs to be subjected to anticorrosion treatment, a joint anticorrosion scheme of reserved corrosion thickness and another anticorrosion measure (anticorrosion coating, cathodic protection and the like) is generally adopted, a calculation formula of the reserved corrosion thickness of the steel pipe pile is obtained according to Port engineering pile foundation Specification (JTS 167-4-2012), the bending strength of the pipe pile with different pipe diameters is researched by using the formula, and finally the following conclusion is obtained: after the reserved corrosion thickness is deducted, the bending strength design value of the steel pipe pile is more than 1.5 times of the bending strength design value of the corresponding large pipe pile, the advantage of good bending resistance of the steel pipe pile is fully exerted, and the engineering requirement can be basically met.
2) Length of steel pipe pile
In order to fully ensure the quality of a pile foundation, according to the Port engineering pile foundation Specification (JTS 167-4-2012) [1], a steel-concrete composite pile joint part is preferably placed below the zero point of the bending moment of a pile body during design, and generally Z is not less than 4T, wherein Z is the depth from the zero point of the bending moment to a mud surface, and T is a relative stiffness characteristic value of the pile.
According to the depth, the distance difference of the steel pipe pile extending below the mud surface is about 1.4-1.5 m for different geological conditions; for two types of piles with different diameters, the distance difference between the steel pipe pile extending below the mud surface is about 0.2-0.3 m. Therefore, the calculation formula of the length of the steel pipe pile below the mud surface can be unified.
3) Bearing capacity of steel-concrete composite pile
The steel-concrete composite pile bears horizontal load and bending moment with the steel-pipe pile on upper portion, bear vertical load with prestressed concrete tubular pile in the lower part, through to horizontal load, bending moment and vertical load research, learn to deduct after reserving corrosion thickness, the vertical bearing capacity of steel-pipe pile body still is greater than corresponding big tubular pile, consequently to steel-concrete composite pile body bearing capacity aspect, its big tubular pile part should be able to satisfy the vertical bearing capacity requirement when the design, steel-pipe pile part should be able to satisfy the bending resistance bearing capacity requirement.
Second, mechanical properties of the joint were analyzed
The invention mainly analyzes the sensitivity of each parameter of the joint.
1) Static mechanical properties
The invention mainly analyzes the stress and deformation of the connecting part, and finds that the stress concentration area of the connecting part of the lower concrete pipe pile and the joint is a bearing danger point of the steel-concrete composite pile under the action of external load. The wall thickness of the outer wall of the connecting part of the steel-concrete composite pile is small, so that the radial displacement is large; meanwhile, the welding position of the stiffened plate and the steel pipe pile has larger radial displacement due to stress concentration. The section inertia moment of the connecting part is 0.0186m 4 And the bending rigidity of the whole connecting part is larger than the weak parts of the upper steel pipe pile, the lower concrete pipe pile and the non-reinforced concrete composite pile.
Analyzing the influence of boundary conditions: the calculation is carried out, wherein the length of each steel pipe pile and the length of each concrete pipe pile at the joint of the steel-concrete composite pile are 3m, the bottom end of the steel-concrete composite pile is fully constrained, and the top end of the steel-concrete composite pile is applied with unit compressive stress. In order to ensure the accuracy of the analysis, the influence of the boundary conditions on the calculation results is studied by changing the lengths of the pipe piles at both ends of the connecting part, and the lengths of the pipe piles are set to be 2m, 3m and 4m respectively, while the other conditions are kept unchanged. Finally, the stress distribution rule of the steel pipe pile or the pipe pile connecting part is basically unchanged.
The 3 rd main stress extreme value in the concrete pipe piles with different lengths is extracted and combined with the corresponding stress cloud chart, so that the fact that the length of the pipe pile with the length of more than 2m basically has no influence on the stress distribution of the pipe pile can be found, and the length of the pipe pile in the follow-up research is 2m.
Specifically, the strength analysis of the concrete pipe pile structure adopts the first main stress to judge whether the concrete structure meets the design tensile strength, and adopts the third main stress to judge whether the concrete structure meets the design compressive strength.
2) And (3) analyzing parameter sensitivity: the effect is not so much found here and is therefore omitted.
3) Linker optimization analysis
And comprehensively optimizing and analyzing parameters of each component of the connecting part by taking the 3 rd main stress extreme value at the upper part of the concrete pipe pile as the limit and taking the minimum volume of the connecting part as the target, and omitting specific contents. On the basis of keeping the original design safety degree, the volume of the connecting part is reduced by 42.9 percent, the material cost of the connecting part is saved, and the optimization effect is good.
Thirdly, analyzing the driving ability of the steel-concrete composite pile
In this embodiment, the 3 rd principal stress extreme value at the upper part of the concrete pipe pile is limited to 0.31, and the parameters of each component of the connecting part are comprehensively optimized and analyzed with the goal of minimizing the volume of the connecting part, and specific contents are omitted. On the basis of keeping the original design safety degree, the volume of the connecting part is reduced by 42.9 percent, the material cost of the connecting part is saved, and the optimization effect is good.
In this example, the driving performance of the steel-concrete composite pile, the steel pipe pile and the large pipe pile under the same conditions were analyzed by comparison. The project carries out the whole-process monitoring of the high strain of 2 steel-concrete composite piles, wherein the actual measured bearing capacity of the 320T-3 pile driving and the 320T-10 pile driving is 7521kN and 7961kN respectively.
Through the calculation result of the punchability and the field actual measurement result in the experiment, it can be seen that:
(1) Under the same geological conditions, the same hammer type is used for respectively sinking three pile types, steel pipe piles, large pipe piles and steel-concrete composite piles with consistent pile length, wall thickness and the like, and the differences of the total hammering number, the final penetration degree and the like are not large. When the steel-concrete composite pile is vibrated and sunk, the energy can be better transmitted to the large tubular pile through the steel pipe pile. The driving performance of the steel-concrete composite pile is not lower than that of a large tubular pile.
(2) Compare big tubular pile, during the pile sinking of steel-concrete composite pile, because on the pile hammer is not direct to act on the pile body concrete, had one section steel-pipe pile in top as the buffering, alleviateed the local compressive stress of big tubular pile top concrete greatly, but make big tubular pile top by the bad nature greatly reduced of beating, be favorable to pile body concrete quality.
(3) The calculated values of the total hammering number and the final penetration of the steel-concrete composite pile are close to the actual situation, but have certain access, mainly because a certain calculation assumption is adopted during calculation by a wave equation method, and in addition, uncertainty also exists in the piling system (the efficiency of the hammer, a hammer pad and a pile pad) and the field geological conditions.
(4) The wave equation method has been applied to analysis of driving performance of a precast pile in the early stage of construction for many times in recent years, including smooth driving of a foundation pile to a designed elevation, final penetration prediction, a pile stopping control standard of the foundation pile, pile driving stress analysis, construction equipment (including hammer type, drop height, hammer pad, pile pad material, thickness and the like), and the like, and plays an active role in smooth development of engineering.
By analyzing the design method, the mechanical property and the like of the steel-concrete composite pile and discussing the sensitivity of each parameter of the connecting part, the connecting part is optimized on the basis, and the following conclusion is obtained:
(1) The steel pipe pile types can be uniformly defined aiming at large pipe piles of different types;
(2) Aiming at the requirement that the joint part of the steel-concrete composite pile is placed below the zero point of the bending moment of the pile body, the calculation formulas of the lengths of the steel pipe piles below the mud surface can be unified;
(3) When the steel-concrete composite pile is designed, the large pipe pile part can meet the vertical bearing capacity requirement, and the steel pipe pile part can meet the bending resistance bearing capacity requirement;
(4) The stress of the concrete pipe pile can be reduced by increasing the thicknesses of the end flange, the steel pipe, the steel covering plate and the reinforced plate and reducing the thickness of the connecting part flange, so that the integral bearing capacity of the steel-concrete composite pile is improved; after optimization, the volume of the connecting part is reduced by 42.9 percent on the basis of keeping the original design safety degree, and the material cost of the connecting part is saved.
(5) When the steel-concrete composite pile is vibrated and sunk, energy can be better transferred to the large tubular pile through the steel pipe pile, and the driving performance of the steel-concrete composite pile is not lower than that of the large tubular pile; when the steel-concrete composite pile is sunk, the local compressive stress of the concrete at the top of the large tubular pile is greatly relieved, so that the driving property of the damaged top of the large tubular pile is greatly reduced, and the quality of the concrete of the pile body is facilitated.
Second part, hoisting design and calculation of steel-concrete composite pile
For long piles, the strength and the crack resistance of the long piles are usually controlled by internal force in the processes of hoisting and hoisting of the piles, and the hoisting condition is far dangerous compared with the horizontal hoisting condition. The method has the advantages that the pile hanging process and the internal force calculation of the steel-concrete composite pile are researched, reasonable design parameters are selected, the internal force of the pile in the hanging process can be reduced as much as possible, the risk of hanging the pile is reduced, and the method has great practical value and economic benefit.
) Research on six-point hoisting of steel-concrete composite pile
General description of the experiment
In the invention, a six-point hoisting test is carried out on the reinforced concrete composite pile, and strain values of measurement points at inclination angles of 0 degree, 15 degrees, 30 degrees, 45 degrees and 55 degrees of the pile body are measured in the hoisting process. The length of a 320T-23 steel-concrete composite pile is 81m, the upper part of the pile is a 28m steel pipe pile, the middle part of the pile is a 0.5m connecting section, and the lower part of the pile is a 52m large pipe pile and a 0.5m steel pile shoe. In the figure, the diameter of the steel pipe pile is 1200mm, the wall thickness is 20mm, and the material is Q345 steel. The wall thickness of the large tubular pile is 145mm, the prestressed tendon adopts a 7 phi 5 steel strand, and the standard value fptk of the tensile strength of the steel strand is 1860MPa.
The hoisting bending moment of the 320T-23 pile six-point hoisting tends to increase firstly and then decrease along with the increase of the inclination angle, the maximum negative bending moment appears at the position of an R4 hoisting point, the value is-1215.0 kN.m when the inclination angle is 30 degrees, and the corresponding maximum concrete compressive stress is 10.33MPa; the maximum positive bending moment occurs at the midspan of the lifting points R1 and R2, the value is 101.7 kN.m when the inclination angle is 45 degrees, and the corresponding maximum concrete tensile stress is 0.86MPa.
) Four-point crane for steel-concrete composite pile
The lifting bending moment of the 20T-10 pile four-point crane also shows a trend of increasing firstly and then decreasing along with the increase of the inclination angle, the maximum negative bending moment appears at the R2 lifting point, the value is-1421.3 kN.m, and the corresponding maximum concrete compressive stress is 12.08MPa; the maximum positive bending moment occurs at the midspan of the lifting points R3 and R4, the value is 305.4 kN.m when the inclination angle is 45 degrees, and the corresponding maximum concrete tensile stress is 2.6MPa. The test values do not exceed the designed value of the anti-cracking bending moment of the concrete pile section of the steel-concrete composite pile, but the safety coefficient is lower, so that four-point hoisting is not recommended to be used for hoisting the long pile.
Through deducing the design calculation method of six-point hanging and four-point hanging of the steel-concrete composite pile and combining with field test verification, the sensitivity of the hanging pile parameters is discussed, and the following conclusion is obtained:
(1) The hoisting bending moment of the steel-concrete composite pile shows a trend of increasing firstly and then reducing along with the increase of the inclination angle, the bending moment in the hoisting process at four points is greater than the hoisting bending moment at the corresponding inclination angle at six points, and although the design value of the anti-cracking bending moment of the concrete pile section of the steel-concrete composite pile is not exceeded, the safety coefficient is lower, so that the four-point hoisting is not recommended to be used for hoisting the long pile;
(2) The theoretical calculation method for the steel-concrete composite pile hanging can better reflect the stress performance of the steel-concrete composite pile when the pile is hung, and the calculation result is safer, so that the design requirement is met;
(3) When the steel-concrete composite pile is hoisted at six points, the hoisting height is high, and the stress performance of the steel-concrete composite pile during hoisting is not greatly influenced by the positions of the hoisting points; the length of the sling S3 and the gravity center position of the steel-concrete composite pile have great influence on the stress performance of the steel-concrete composite pile during hoisting, and the lengths of the sling S3 and the concrete pile section are determined under the condition that the conditions allow;
(4) During four-point hoisting, the hoisting height, the length of the sling S1, the position of each hoisting point and the gravity center position of the steel-concrete composite pile have great influence on the stress performance during hoisting of the steel-concrete composite pile, and the hoisting height, the length of the sling S1, the position of each hoisting point and the gravity center position of the steel-concrete composite pile are determined according to the practical engineering conditions by comprehensive consideration.
Third part of economic cost analysis
In the embodiment, the economic benefits of the single-pile composite steel-concrete pile are comprehensively analyzed by comparing the single-pile economic cost of the steel-concrete composite pile in part of engineering projects based on a budget formula.
The bending resistance of the upper part of the steel-concrete composite pile is equivalent to that of the steel pipe pile, the application bottleneck that the bending resistance of the prestressed concrete large pipe pile is insufficient is broken to a certain extent, and the application of the prestressed concrete pipe pile in related engineering can be expanded; compared with the corresponding steel pipe pile, the steel-concrete composite pile designed by the method has higher cost performance, the cost is reduced by 35-38% in the calculation example of the embodiment, and the steel-concrete composite pile for the engineering pile foundation in the open sea deep water area is used for replacing the steel pipe pile, so that considerable economic benefit and social benefit are generated.
The reinforced concrete composite pile provides a new pile type for the engineering industry, can be selected and adopted according to various engineering conditions, and has huge vitality and wide application prospect.
The invention analyzes the mechanical property, the design calculation method, the test technology, the economic cost and the like of the steel-concrete composite pile to obtain the following conclusion:
(1) The types of the steel pipe piles in the steel-concrete composite pile can be uniformly divided into two; the calculation formula of the length Z of the steel pipe piles below the mud surface can be unified;
(2) When the steel-concrete composite pile is designed, the large pipe pile part can meet the vertical bearing capacity requirement, and the steel pipe pile part can meet the bending resistance bearing capacity requirement;
(3) The stress of the concrete pipe pile can be reduced by increasing the thicknesses of the end flange, the steel pipe, the steel covering plate and the reinforced plate and reducing the thickness of the connecting part flange, so that the integral bearing capacity of the steel-concrete composite pile is improved;
(4) The theoretical calculation method for the steel-concrete composite pile hanging can better reflect the stress performance of the steel-concrete composite pile when the pile is hung, and the calculation result is safer, so that the design requirement is met; the hoisting bending moment of the steel-concrete composite pile shows a trend of increasing and then decreasing along with the increase of the inclination angle, the bending moment in the hoisting process at four-point hoisting is greater than that at the corresponding inclination angle at six-point hoisting, and four-point hoisting is not recommended to be used for hoisting the long pile;
(5) When the steel-concrete composite pile is hoisted at six points, the hoisting height is high, and the stress performance of the steel-concrete composite pile during hoisting is not greatly influenced by the positions of the hoisting points; the length of the sling S3 and the gravity center position of the steel-concrete composite pile have great influence on the stress performance of the steel-concrete composite pile during hoisting, and the lengths of the sling S3 and the concrete pile section are determined under the condition that the conditions allow;
(6) During four-point hoisting, the hoisting height, the length of the sling S1, the position of each hoisting point and the gravity center position of the steel-concrete composite pile have great influence on the stress performance during hoisting of the steel-concrete composite pile, and the hoisting height, the length of the sling S1, the position of each hoisting point and the gravity center position of the steel-concrete composite pile are determined according to the practical engineering conditions by comprehensive consideration.
(7) Compared with the corresponding steel pipe pile, the steel-concrete composite pile designed according to the invention has higher cost performance, can reduce the cost by more than 33 percent, and can generate considerable economic and social benefits when the steel-concrete composite pile is used for replacing the steel pipe pile in the engineering pile foundation of the open sea deep water area.
The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (10)
1. The reinforced concrete composite pile is characterized by comprising a steel pipe pile positioned above water and a concrete large pipe pile positioned below water, wherein the steel pipe pile and the concrete large pipe pile are connected through a connecting section, and a steel pile shoe is arranged on one side of the large pipe pile, which is far away from the steel pipe pile;
flanges for connecting the steel pipe pile and the concrete large pipe pile are respectively arranged on two sides of the connecting section, the flanges close to the concrete large pipe pile act on the concrete large pipe pile simultaneously, and prestress is generated;
the large concrete pipe pile comprises a plurality of pipe joints which are formed by pouring reinforcing steel bar hole spiral bars and longitudinal reinforcing steel bars by adopting a C60 or C70 dry and hard concrete through a centrifugal vibration rolling composite process, wherein in the plurality of pipe joints, the section of each pipe joint is at least provided with 16 preformed holes, and the preformed holes far away from the direction of the steel pipe pile are connected with the steel pile shoe through an anchorage device along the length direction of the large concrete pipe pile.
2. The reinforced concrete composite pile according to claim 1, wherein the connecting section comprises a steel anchor ear, a rectangular stiffening plate and a triangular stiffening plate in sequence from the steel pipe pile to the concrete large pipe pile.
3. The steel-concrete composite pile according to claim 2, wherein the rectangular stiffening plates are circular rings as seen in a cross-sectional view, the circumference of the circular rings is symmetrically divided into a plurality of rectangular stiffening plates, and concrete is filled in the rectangular stiffening plates.
4. The steel-concrete composite pile according to claim 2, wherein the triangular stiffener has a thickness of not less than 15mm.
5. The method for manufacturing a steel-concrete composite pile according to any one of claims 1 to 4, comprising the steps of:
preparing a concrete large pipe pile: the method sequentially comprises the steps of installing a steel reinforcement cage, installing a template, pouring the steel pipe pile, steaming, removing the template and performing water curing, wherein C60 or C70 hard concrete is selected for pouring the steel pipe pile;
preparing the steel pipe pile: the method comprises the following steps of (1) selecting steel to manufacture the steel pipe pile, coating an anticorrosive paint layer on the outer layer of the steel pipe pile, arranging modified epoxy glass flake heavy anticorrosive paint at the bottom of the anticorrosive paint layer, and arranging acrylic polyurethane paint on the anticorrosive paint layer;
installing a connecting section: welding the connecting sections between the adjacent steel pipe piles and between the steel pipe piles and the large pipe pile;
welding the steel pile shoe: and welding the steel pile shoe to the side part of the large tubular pile.
6. The method for preparing the steel-concrete composite pile according to claim 5, wherein the step of preparing the large tubular pile further comprises the step of pulling steel strands, and the steps of brushing the adhesive, completing secondary tensioning and splicing, lifting, grouting, welding steel cladding plates, lengthening steel pile shoes and welding stiffening plates sequentially are included.
7. The method for preparing the steel-concrete composite pile according to claim 5, wherein the preparation of the steel pipe pile further comprises the assembly of a sacrificial anode, specifically, the sacrificial anode is installed and fixed by adopting underwater dry welding, and the iron core of the sacrificial anode is made of deformed steel.
8. The method for preparing the steel-concrete composite pile according to claim 5, wherein during installation of the connecting section, triangular stiffening plates are arranged along the circumferential direction at the joint of the adjacent steel pipe piles and the joint of the steel pipe pile and the large pipe pile, the thickness of each triangular stiffening plate is 12-18mm, and the height of each triangular stiffening plate is 400-600mm.
9. Use of a steel-concrete composite pile according to any one of claims 1 to 4 in a ground condition of fine sand, silt sand, medium coarse sand, silty clay, sandy clay, gravel sand, dense sand or weathered rock.
10. The application of the steel-concrete composite pile according to claim 9, wherein the application comprises hoisting of the steel-concrete composite pile, and the hoisting is six-point hoisting or four-point hoisting.
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