CN116024959B - Precast pile, construction method thereof and quality detection method - Google Patents
Precast pile, construction method thereof and quality detection method Download PDFInfo
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Abstract
A precast pile, comprising: the pile comprises a steel pipe, a joint, an anchor disc, an end structure and a distributed optical fiber sensor, wherein the steel pipe is used as a pile body and is divided into a spiral anchor section and an optical pipe section in the length direction, the joint is positioned at the top end of the spiral anchor section, the anchor disc is fixed on the spiral anchor section and is circumferentially and spirally distributed, the end structure is positioned at the tail end of the optical pipe section, and the distributed optical fiber sensor is fixed with the steel pipe. Aiming at an undisturbed soil foundation of a rock or a hard soil body lying below an upper soil covering layer, the bearing capacity of the pile body is increased by additionally arranging anchor plates which are spirally distributed on the steel pipe pile body, so that the beneficial technical effects of reducing the size of the pile body and reducing the manufacturing, transportation and construction cost of the steel pile are realized; the defect that the screw anchor is not suitable for geological conditions of shallow overburden rock, underlying rock or hard soil is overcome by pre-punching, so that the application range of the screw anchor foundation is enlarged; and the distributed optical fiber sensor is used for obtaining the temperature change of the precast pile and pile forming stress distribution after grouting, so that the data real-time detection of pile forming quality is realized.
Description
Technical Field
The invention belongs to the field of geotechnical engineering steel piles, and particularly relates to a precast pile, a construction method thereof and a quality detection method.
Background
Along with the continuous development of technology, the foundation gradually develops towards miniaturization, mechanization and environmental protection in engineering construction, and more projects adopting original soil foundations such as spiral anchors, prefabricated steel pipe piles and the like become an important way for reducing engineering investment. However, the foundation has the application range, and greatly limits the popularization and application in engineering. In addition, in many mountainous and hilly areas, the original soil foundation in a single form cannot meet the engineering construction requirement, so that precast pile foundations are needed to be selected, and the bearing capacity of the original rock-soil body is fully exerted.
The spiral anchor is used as a steel environment-friendly foundation and is composed of an anchor rod, an anchor disc, an anchor head and the like, a foundation pit is not required to be excavated during construction, the spiral anchor is screwed into a deeper soil body by applying torque on the top of the anchor rod, disturbance on the foundation soil body is small, the bearing performance of an undisturbed soil layer can be fully exerted, and compared with a concrete cast-in-situ foundation, the spiral anchor has the characteristics of light weight, convenience in transportation and construction, good bearing performance and the like, is mainly suitable for a softer soil foundation, has poor applicability to a hard soil layer and is not suitable for a rock foundation; the screw anchor construction screwing torque uncertainty of the complex stratum is high, and the construction machine configuration difficulty is high.
The steel pipe pile is used as a deep foundation, is composed of a plurality of steel piles which are sunk into the soil and a bearing platform which is connected with the pile top, can be sunk in a hammering, vibrating and static pressure mode, jointly bears the upper load action through the resistance between the pile side and the foundation soil and the pile end resistance, has the advantages of high bearing capacity, large horizontal resistance, flexible design, short construction period and the like, and is suitable for areas where the upper soil layer is weak, and the lower part is a hard soil layer or a rock stratum. However, the steel pipe pile has high use cost, so that further application and popularization are limited.
Grouting is an engineering technology with strong practicability and wide application range, and utilizes a hydraulic, pneumatic or electrochemical method to inject slurry for consolidation of a rock-soil body into pores and cracks of the rock-soil body, so that the rock-soil body becomes a new structure body with high strength and high stability, thereby achieving the aim of improving the physical and mechanical properties of the rock-soil body; the method is also the most common technical measure for improving the bearing performance of the undisturbed soil foundation, and the grouting quality has great influence on the bearing capacity of the undisturbed soil foundation. The gaps of the rock-soil body have strong irregular characteristics, so that the grouting effect is seriously affected, and the grouting quality is difficult to detect by the existing construction process.
Disclosure of Invention
The invention aims to expand the application range of the spiral anchor and the steel pipe pile, reduce the use cost of the steel pipe pile and improve the construction quality.
The invention aims at realizing the following technical scheme:
a precast pile, the precast pile comprising: the pile comprises a steel pipe, a joint, anchor discs and an end structure, wherein the steel pipe is used as a pile body and is divided into a spiral anchor section and a light pipe section in the length direction, the joint is positioned at the top end of the spiral anchor section, the anchor discs are fixed on the spiral anchor section and are circumferentially and spirally distributed, and the end structure is positioned at the tail end of the light pipe section.
Preferably, the precast pile further comprises a distributed optical fiber sensor fixed with the steel pipe.
Preferably, a slot is formed in the outer side of the steel pipe along the length direction and is used for embedding the distributed optical fiber sensor.
Preferably, the end structure comprises an open end or a closed end.
Preferably, the closed end has a grouting hole in the middle.
Preferably, the diameter of the steel pipe is 70-300 mm.
Preferably, the wall thickness of the steel pipe is 6-20 mm.
Preferably, the number of the anchor discs is 1-4.
Preferably, the diameter of the anchor disc is 2-5 times of the diameter of the steel tube.
The invention also provides a precast pile construction method based on the same inventive concept, which comprises the following steps:
s10: drilling pile holes in the foundation by adopting drilling machinery;
s20: removing bottom sediment of the pile hole;
s30: screwing the precast pile into the pile hole to a preset foundation burial depth;
s40: and filling gaps between the precast piles and the foundation by grouting or pressing concrete.
Preferably, the diameter of the pile hole is larger than the diameter of the steel pipe and smaller than the diameter of the anchor disc.
Preferably, the diameter of the pile hole satisfies the following conditions: the diameter of the steel pipe is 20-100 mm and is smaller than the diameter of the anchor disc by 200mm.
Preferably, the pressure of grouting or pressure grouting concrete is 0.8-1.5 MPa.
Preferably, the removing the bottom sediment of the pile hole includes: and cleaning the sediment at the bottom of the pile hole by air blowing, slurry pumping, slag drawing or slurry changing.
The invention also provides a precast pile quality detection method based on the same inventive concept, which is used for detecting the precast pile grouting quality and comprises the following steps:
z10: after the grouting construction of the precast pile is finished, the upper computer acquires temperature change data of different positions of the precast pile through an optical time domain reflectometer and a distributed optical fiber sensor;
z20: and comparing the temperature change data of different positions of the precast pile with a standard temperature curve of the grouting material curing process to determine filling and cementing quality of the grouting material.
The invention also provides another precast pile quality detection method based on the same inventive concept, which is used for pile forming quality detection of the precast pile, and comprises the following steps:
c10: after the construction of the precast pile is completed, applying a preset static load to the precast pile by adopting a press machine;
c20: the upper computer obtains stress distribution data of different positions of the precast pile through an optical time domain reflectometer and a distributed optical fiber sensor (5);
c30: calculating pile forming bearing capacity of the precast pile according to the obtained stress distribution data and the size data of the precast pile;
c40: and comparing the pile forming bearing capacity with the rated bearing capacity of the precast pile to judge pile forming quality.
Preferably, the distributed optical fiber sensors are located in grooves formed in the outer side of the steel pipe of the precast pile along the length direction.
Preferably, the distributed optical fiber sensor comprises a photonic crystal fiber or a polymer fiber.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a precast pile, which comprises: the pile comprises a steel pipe, a joint, anchor discs and an end structure, wherein the steel pipe is used as a pile body and is divided into a spiral anchor section and a light pipe section in the length direction, the joint is positioned at the top end of the spiral anchor section, the anchor discs are fixed on the spiral anchor section and are circumferentially and spirally distributed, and the end structure is positioned at the tail end of the light pipe section. Aiming at the undisturbed soil foundation of the rock or the hard soil body lying under the upper soil covering layer, the invention increases the bearing capacity of the pile body by additionally arranging the anchor plates which are spirally distributed on the steel pipe pile body, thereby realizing the beneficial technical effects of reducing the size of the pile body and reducing the manufacturing, transportation and construction cost of the steel pile; the defect that the spiral anchor is not suitable for geological conditions of shallow overburden rock or underlying rock or hard soil is overcome by pre-punching; the invention overcomes the defects that the bearing capacity of the steel pipe pile in the soft soil layer is insufficient and the spiral pile is not suitable for the geological conditions of shallow covering layer, underlying rock or hard soil, reduces the use cost of the steel pipe pile, and further expands the application range of the undisturbed soil foundation through different construction processes.
The invention discloses a precast pile detection method, which comprises the following steps: after the construction of the precast pile is finished, detecting the temperature of the precast pile by using a distributed optical fiber sensor, and determining the cementing quality of grouting materials according to the temperature change; when the stress detection is needed, pile body stress distribution of the precast pile is detected based on the distributed optical fiber sensor, and pile quality is judged according to the pile body stress distribution. According to the invention, the distributed optical fiber sensor is used for obtaining the temperature change of the precast pile and the pile forming stress distribution rule after grouting, so that the data real-time detection of pile forming quality is realized, the construction quality is improved, the construction risk is reduced, and the use cost of the steel pipe pile is further reduced.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a cross-sectional view of section A-A of FIG. 1;
FIG. 3 is a cross-sectional view of section B-B of FIG. 1;
FIG. 4 is a schematic view of an open end of the present invention;
FIG. 5 is a schematic view of a closed end of the present invention;
FIG. 6 is a flow chart of a construction method of a precast pile according to the present invention;
FIG. 7 is a graph showing the temperature change of a steel pipe after pouring of the grouting material according to the present invention;
FIG. 8 is a graph showing the stress distribution of the pile body after construction according to the present invention;
FIG. 9 is a flow chart of a construction method of a precast pile according to the present invention;
wherein: 1-steel pipe, 2-joint, 3-anchor disc, 4-end structure, 5-distributed optical fiber sensor, 6-cementing area, 101-steel pipe diameter, 102-end opening, 103-grouting hole, 301-anchor disc diameter, 302-anchor disc pitch, 303-anchor disc spacing.
Detailed Description
The technical solution is further described below with reference to the drawings and the specific embodiments to help understand the content of the present invention.
Example 1
As shown in fig. 1, the present invention discloses a precast pile, which includes: the pile comprises a steel pipe 1 serving as a pile body and divided into a spiral anchor section and a light pipe section in the length direction, a joint 2 positioned at the top end of the spiral anchor section of the steel pipe 1, anchor discs 3 fixed on the spiral anchor section of the steel pipe 1 and distributed in a circumferential spiral mode, an end structure 4 positioned at the tail end of the light pipe section of the steel pipe 1 and a distributed optical fiber sensor 5 fixed with the steel pipe 1.
As shown in fig. 2 and 3, the steel pipe 1 includes a groove for embedding the distributed optical fiber sensor 5, and the distributed optical fiber sensor 5 is placed in the groove and fixed to the steel pipe 1 by adhesion, and may be fixed by epoxy resin type structural adhesive.
The end structure 4 comprises an open end or a closed end; as shown in fig. 4, the open end is kept open at the end of the steel pipe 1, and has an end opening 102 of the same size as the inner diameter of the steel pipe; the closed end is tapered as shown in fig. 5, and the steel pipe 1 has a grouting hole 103 at the tapered end for grouting.
The diameter of the steel pipe 1 is 70-300 mm; the wall thickness of the steel pipe 1 is 6-20 mm; the diameter 101 and the wall thickness of the steel pipe are calculated according to the maximum bearing of the precast pile and the geological condition of the foundation, and the concrete mechanical calculation process is the prior art, so that the description is omitted.
The number of the anchor discs 3 is 1-4, the anchor discs 3 are spiral surfaces taking the axle center of the pile body as a rotating shaft, the circumferential angle of each anchor disc 3 is 360 degrees to provide balanced supporting force, the bearing capacity of the precast pile can be increased to shorten the pile body size by increasing the number of the anchor discs 3, and the precast pile can be suitable for soft soil layers without being implanted with hard soil or rock layers by increasing the number of the anchor discs for construction projects with lower bearing capacity requirements, so that the construction difficulty and construction cost are greatly reduced; the number of the anchor discs 3 is calculated and determined according to the maximum bearing of the precast pile and the geological condition of the foundation, and the specific mechanical calculation process is the prior art, so that the description is omitted.
The diameter 301 of the anchor disc is 2-5 times of the diameter 101 of the steel pipe, and the excessive diameter 301 of the anchor disc can increase torque during screwing in, so that construction difficulty and cost are increased; the larger anchor disc diameter 301 can improve the bearing capacity of the precast pile, and the larger opening diameter can reduce the depth of the anchor disc entering the stratum and reduce the screwing torque, so that the proportional relation among the anchor disc diameter 301, the drilling diameter and the steel pipe diameter 101 needs to be balanced according to the geological conditions of specific construction, and the calculation process is the prior art in the building field, so that the details are not described.
The distributed optical fiber sensor 5 includes a photonic crystal fiber or a polymer fiber.
The spiral anchor is used as a steel environment-friendly foundation and is composed of an anchor rod, an anchor disc, an anchor head and the like, a foundation pit is not required to be excavated during construction, the spiral anchor is screwed into a deeper soil body by applying torque on the top of the anchor rod, disturbance to the foundation soil body is small, the bearing performance of an undisturbed soil layer can be fully exerted, and compared with a concrete cast-in-situ foundation, the foundation has the characteristics of light weight, convenience in transportation and construction, good bearing performance and the like, and is mainly suitable for a softer soil foundation.
The steel pipe anchor is a foundation in which a steel pipe is directly put into a borehole drilled in a rock foundation mechanically (or manually) and the steel pipe and the rock mass are cemented into a whole by pouring cement mortar. The steel pipe pile is used as a deep foundation, is composed of a plurality of steel piles which are sunk into the soil and a bearing platform which is connected with the pile top, can be sunk in a hammering, vibrating and static pressure mode, and jointly bears the upper load through the resistance between the pile side and the foundation soil and the pile end resistance, has the advantages of high bearing capacity, large horizontal resistance, flexible design, short construction period and the like, is suitable for the areas with weak upper soil layer and hard soil layer or rock stratum at the lower part, but the existing steel pipe pile can provide enough bearing capacity only when entering the hard soil layer or rock stratum at the lower part, and has to increase the length and the diameter size for the construction project with thicker soft soil layer or high bearing requirement, so that the use cost of the steel pipe pile is further increased.
The precast pile is a composite structure steel pile with a spiral anchor at the upper part and a steel pipe anchor at the lower part, and the upper structure acting force is resisted by the anchoring force of an anchor disc and a soil body, the binding force between concrete and a steel pipe and the rock-soil body. The precast pile consists of a joint, a steel pipe, a spiral anchor disc and an end structure, wherein the joint is positioned at the top of the steel pipe, the anchor disc is arranged at the upper part of the steel pipe, and the end structure is positioned at the bottom of the steel pipe; slotting the outer part of the steel pipe, and burying at least one distributed optical fiber sensor of a loop from top to bottom; the end structure can adopt an open type or a closed type, a grouting hole is preset in the closed type end structure, and grouting or concrete injection can be performed through the inside of the steel pipe; after the precast pile is installed to a preset burial depth, the anchor disc is screwed into an upper soil layer, and the end structure enters a decubitus rock or a hard (compact) soil body; through grouting or pressing the concrete between steel pipe and ground gap, make it and the cementing of stake week ground body form wholly, jointly resist the effort of superstructure, this novel pile body structure can exert the bearing capacity of upper cover soil layer and decubitus rock or hard (closely knit) soil body, accessible distributed optical fiber sensor detects into the stake quality simultaneously.
As shown in fig. 2, the section A-A of fig. 1 is in order from inside to outside: the device comprises a steel pipe 1, a distributed optical fiber sensor 5 arranged in a groove, a cementing area 6 between the steel pipe 1 and a foundation and an anchor disc 3; as shown in fig. 3, the section B-B of fig. 1 is, in order from inside to outside: steel pipe 1, distributed optical fiber sensor 5 installed in the groove, cementing region 6 between steel pipe 1 and the foundation.
The material and the structural requirement of the precast pile are as follows: q235, Q355 or Q420 is adopted as the steel; the diameter of the steel pipe is 70 mm-300 mm, and the wall thickness is 6 mm-20 mm; 1-4 anchor discs can be arranged on the upper part of the steel pipe, the diameter of each anchor disc is 2-5 times of that of the steel pipe, the distance between the anchor discs is preferably an integral multiple of the pitch of each anchor disc so that paths of multiple anchor discs coincide, and screwing resistance can be reduced; grouting materials can be cement paste, cement mortar and the like; the distributed optical fiber sensor 5 can adopt photonic crystal optical fibers and polymer optical fibers.
The steel pipe anchor is a foundation in which a steel pipe is directly put into a borehole drilled in a rock foundation mechanically (or manually) and the steel pipe and the rock mass are cemented into a whole by pouring cement mortar. The spiral anchor is used as a steel environment-friendly foundation and is composed of an anchor rod, an anchor disc, an anchor head and the like, a foundation pit is not required to be excavated during construction, the spiral anchor is screwed into a deeper soil body by applying torque on the top of the anchor rod, disturbance to the foundation soil body is small, the bearing performance of an undisturbed soil layer can be fully exerted, and compared with a concrete cast-in-situ foundation, the foundation has the characteristics of light weight, convenience in transportation and construction, good bearing performance and the like, and is mainly suitable for a softer soil foundation.
Aiming at the undisturbed soil foundation of the rock or the hard soil body lying under the upper soil covering layer, the invention increases the bearing capacity of the pile body by additionally arranging the anchor plates which are spirally distributed on the steel pipe pile body, thereby realizing the beneficial technical effects of reducing the diameter and the length dimension of the pile body and reducing the manufacturing, transportation and construction cost of the steel pile; the defect that the spiral anchor is not suitable for geological conditions of shallow overburden rock or underlying rock or hard soil is overcome by pre-punching; the invention solves the problems that the bearing capacity of the steel pipe pile in the soft soil layer is insufficient and the spiral pile is not suitable for the geological conditions of shallow covering layer, underlying rock or hard soil, and further expands the application range of the undisturbed soil foundation through different construction processes; according to the invention, the distributed optical fiber sensor is used for obtaining the temperature change of the precast pile and the pile forming stress distribution rule after grouting, so that the data real-time detection of pile forming quality is realized, the construction quality is improved, the construction risk is reduced, and the method has remarkable economic benefit.
Example 2
Based on the same inventive concept, the present invention also provides a precast pile construction method for construction of a precast pile as described in embodiment 1, comprising the steps of:
s10: drilling pile holes in the foundation by adopting drilling machinery, wherein the diameter of the pile holes is larger than that of the steel pipes and smaller than that of the anchor disc;
s20: removing bottom sediment of the pile hole;
s30: screwing the precast pile into the pile hole to a preset foundation burial depth;
s40: and filling gaps between the precast piles and the foundation by grouting or pressing concrete.
The diameter of the pile hole meets the following conditions: the diameter of the steel pipe is 20-100 mm and is smaller than the diameter of the anchor disc by 200mm, the bearing capacity and the required screwing torque can be adjusted by adjusting the difference between the pile hole size and the diameter size of the anchor disc, and the construction flexibility of the precast pile and the adaptability to different geological environments can be improved.
The pressure of the grouting or press-grouting concrete is 0.8-1.5 MPa.
The removing of the bottom sediment of the pile hole comprises: and cleaning the sediment at the bottom of the pile hole by air blowing, slurry pumping, slag drawing or slurry changing.
As shown in fig. 6, the specific construction method is as follows:
preparing construction;
drilling: the hydraulic drilling machine, the pneumatic percussion drilling machine and other mechanical construction can be adopted, and the drilling diameter D=the diameter d+ (20-100 mm) of the steel pipe is 200mm smaller than the diameter of the anchor disc;
hole cleaning: after drilling is completed, the sediment at the bottom of the hole can be cleaned by adopting modes of air blowing, pulp pumping, slag drawing, pulp changing and the like;
screwing: adopting mechanical screwing construction, screwing the spiral anchor-steel pipe anchor precast pile foundation to the preset foundation burial depth;
grouting: or pressing and pouring concrete; before grouting, slag removal treatment is carried out on the hole bottom, grouting or pressing grouting concrete operation is carried out, the grouting pressure is maintained at about 1MPa, the grouting material is prepared according to the designed grouting amount which is 1.5 times, and when the hole wall is partially collapsed, the grouting amount is increased according to specific conditions.
The structural state after construction is finished is shown in fig. 9, the steel pipe 1 penetrates into a rock mass or a hard soil mass, the anchor disc 3 is combined with the soil mass, grouting or concrete is added from an opening reserved at the joint 2, the grouting or concrete passes through the inside of the steel pipe 1 to the end structure 4 and enters into a gap space between the steel pipe 1 and a foundation, and a cementing area 6 is formed in a gap between the steel pipe 1 and the soil mass, the rock mass or the hard soil mass through grouting (or pressing grouting concrete), so that the precast pile and an undisturbed soil foundation are strongly fixed, and the precast pile achieves the expected strength.
Aiming at the undisturbed soil foundation of the rock or the hard soil body lying under the upper soil covering layer, the invention increases the bearing capacity of the pile body by additionally arranging the anchor plates which are spirally distributed on the steel pipe pile body, thereby realizing the beneficial technical effects of reducing the diameter and the length dimension of the pile body and reducing the manufacturing, transportation and construction cost of the steel pile; the defect that the screw anchor is not suitable for the large-diameter steel pile is overcome by pre-punching; the invention solves the problems that the bearing capacity of the steel pipe pile in the soft soil layer is insufficient and the spiral pile is not suitable for the large-diameter steel pile, and adapts to different construction processes and geological conditions through different end structures, thereby further expanding the application range of the undisturbed soil foundation.
Example 3
Based on the same inventive concept, the invention also provides a precast pile quality detection method for detecting the precast pile grouting quality, wherein the detection method comprises the following steps:
z10: after the grouting construction of the precast pile is finished, the upper computer acquires temperature change data of different positions of the precast pile through an optical time domain reflectometer and a distributed optical fiber sensor (5);
z20: and comparing the temperature change data of different positions of the precast pile with a standard temperature curve of the grouting material curing process to determine filling and cementing quality of the grouting material.
The precast pile is the precast pile described in embodiment 1, but is not limited to the precast pile disclosed by the invention, and the grouting quality detection method of the precast pile is also applicable to grouting quality detection of other types of precast piles.
The setting and hardening of the grouting material is generally divided into the following stages:
(1) initial reaction period: in the early stage of hydration, as the hydrate is not much, grouting material particles coated with a hydrate film layer are separated, the mutual attraction force is small, and the grouting slurry has good plasticity. Typical exothermic reactions are carried out at 168J/g.h for a duration of 5 to 10 minutes.
(2) Incubation period: the gel film layer grows around the grouting material particles and forms point contact with each other to form a loose network structure, so that the grouting slurry body starts to lose fluidity and partial plasticity, and is initially set, but does not have strength at the moment. The exothermic reaction rate was 4.2J/g.h for a duration of 1h.
(3) Coagulation period: the gel film breaks (the osmotic pressure generated by the fact that the water permeates into the film and the water diffuses outwards through the film is higher than the speed of the water), the grouting material particles are further hydrated, and the reaction speed is increased until the broken film is repaired by new gel. The exothermic reaction rate was gradually increased to 211/g.h over 6h with a duration of 6h.
(4) Hardening period: the gel formed further fills the gaps between the particles, and the capillary holes are smaller and smaller, so that the structure is tighter, and the grouting slurry gradually develops strength to enter a hardening stage. The exothermic reaction rate gradually decreased to 4.2J/g.h over 24h for a period of 6h to several years. After a long period of hydration (months or even years), most of the particles remain with the core that has not yet been hydrated. Thus, the hardened grouted rock is a heterogeneous structure consisting of gel, unhydrated grouting particles and capillaries.
Regarding the curing process of the grouting material, since the first stage has a short time and the second stage has a low heat release rate, the first two stages are omitted, the curing process is divided into a setting stage and a hardening stage, and the temperature curve of the embodiment only shows the temperature change of the setting stage and the hardening stage. The purpose of measuring the precast pile temperature curve is to determine the end of the curing process of the grouting material through temperature change, and the structural strength of the grouting material reaches the expected index so as to facilitate the work of the next working procedure.
And (3) cement quality detection: as the grouting material is cemented to generate hydration heat, the temperature of the pile end and the pile periphery is gradually increased, and then slowly decreased. The temperature of a plurality of points can be continuously detected through the distributed optical fibers arranged on the pile body, a time-temperature curve is drawn, if the time-temperature curve trend of the points is shown in the graph 7, the cementing quality is good, if part of the points do not have obvious temperature rising process, the cementing quality of the points is not expected, the temperature rising is not obvious, the insufficient filling of the point grouting material is indicated, the fact that the point grouting material has larger cavities is indicated, and the distribution range and the size of the defect position can be judged through the temperature change of the points.
The grouting material is hydrated to generate heat, the temperature of the pile body is continuously monitored after grouting, a temperature change curve is shown in fig. 7, and the temperature curve in the drawing is divided into three parts of a temperature rising section, a temperature falling section and a slow falling section; the temperature rising section and the falling section correspond to the setting period of the curing reaction of the grouting material together, wherein the temperature rising section represents the exothermic time period before the curing reaction reaches the extremum, and the exothermic amount gradually decreases after the curing reaction reaches the extremum, so that the temperature rising section is represented as the temperature falling section of the temperature curve; the slow-down section of the temperature curve represents the hardening period of the curing reaction of the grouting material, the heat release amount of the curing reaction at the stage is greatly reduced, the heat accumulated by the early-stage curing reaction is continuously dissipated, and the heat release amount of the curing reaction in the hardening period is lower than the heat dissipated by the precast pile to the surrounding environment, so that the slow-down section of the temperature curve is formed. The formation of the slow-down section represents the beginning of the hardening period of the curing reaction of the grouting material, the minimum hardening time of the hardening period is calculated according to the curing characteristic (the relation between the curing time and the strength) of the used grouting material and the minimum requirement of the subsequent working procedure on the bearing strength of the precast pile, and the grouting curing of the precast pile is considered to be finished after the time of the slow-down section of the temperature curve is greater than the minimum hardening time, so that the cementing quality of the grouting material is detected through the temperature change.
According to the invention, the distributed optical fiber sensor is used for obtaining the temperature change of the precast pile after grouting, so that the data real-time detection of grouting quality is realized, the pile forming quality is improved, the construction risk is reduced, and the method has remarkable economic benefit.
Example 4
Based on the same inventive concept, the invention also provides another precast pile bearing capacity detection method for pile forming quality detection of the precast pile, wherein the detection method comprises the following steps:
c10: after the construction of the precast pile is completed, applying a preset static load to the precast pile by adopting a press machine;
c20: the upper computer obtains stress distribution data of different positions of the precast pile through an optical time domain reflectometer and a distributed optical fiber sensor (5);
c30: calculating pile forming bearing capacity of the precast pile according to the obtained stress distribution data and the size data of the precast pile;
c40: and comparing the pile forming bearing capacity with the rated bearing capacity of the precast pile to judge pile forming quality.
The precast pile construction adopts a precast pile construction method as described in embodiment 2.
The distributed optical fiber sensors are located in grooves formed in the outer sides of the steel pipes of the precast piles in the length direction.
The distributed fiber optic sensor includes a photonic crystal fiber or a polymer fiber.
The detection device used for the precast pile quality detection method comprises the following steps: the device comprises a distributed optical fiber sensor fixed with a precast pile, an optical time domain reflectometer connected with the distributed optical fiber sensor, and an upper computer connected with the optical time domain reflectometer; the distributed optical fiber sensor and the precast pile are mutually fixed; the precast pile is the precast pile described in the embodiment 1, but is not limited to the precast pile disclosed by the invention, and the precast pile bearing capacity detection method is also applicable to pile forming quality detection of other types of precast piles.
The distributed optical fiber sensors are located in grooves formed in the outer sides of the steel pipes of the precast piles in the length direction.
The distributed fiber optic sensor includes a photonic crystal fiber or a polymer fiber.
The data collection and data processing are both prior art, and therefore will not be described in detail.
Static load test: during static load test, the strain of a plurality of points can be detected by using the distributed optical fibers, the stress distribution of the pile body can be calculated according to the strain, the bearing capacity can be calculated, and the pile quality can be determined.
When the engineering quality sampling detection static load test is carried out, the stress distribution of the pile body is measured through the distributed optical fiber sensor, the change trend of the stress along with the depth is shown in fig. 8, the actual bearing capacity of the precast pile can be calculated through the surface area and the stress distribution of the precast pile (the calculation process is the prior art and is not repeated), when the actual bearing capacity of the precast pile is smaller than the engineering expected bearing capacity, the pile forming quality of the precast pile is represented to be unqualified, and when the actual bearing capacity of the precast pile is larger than the engineering expected bearing capacity, the pile forming quality of the precast pile is represented to be qualified, so that the pile forming quality is determined according to the stress distribution.
According to the invention, the pile-forming stress distribution rule is obtained through the distributed optical fiber sensor, and the bearing capacity of the precast pile is obtained through calculation, so that the data real-time detection of pile-forming quality is realized, the pile-forming quality is improved, the construction risk is reduced, and the method has remarkable economic benefit.
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof, but rather as providing for the use of additional embodiments and advantages of all such modifications, equivalents, improvements and similar to the present invention are intended to be included within the scope of the present invention as defined by the appended claims.
Claims (14)
1. A precast pile suitable for use on undisturbed soil foundations of bedrock or hard soil under an upper earth layer, characterized in that the precast pile used comprises: the pile comprises a steel pipe (1) used as a pile body and divided into a spiral anchor section and a light pipe section in the length direction, a joint (2) positioned at the top end of the spiral anchor section, anchor discs (3) fixed on the spiral anchor section and distributed in a circumferential spiral manner, an end structure (4) positioned at the tail end of the light pipe section, and a distributed optical fiber sensor (5) fixed with the steel pipe (1); the end structure (4) comprises an open end or a closed end; the closed end part is conical and is provided with a grouting hole (103) in the middle; the distributed optical fiber sensor detects the temperature after the construction of the precast pile is finished, and determines the cementing quality of grouting materials according to the temperature change; and the distributed optical fiber sensor detects pile body stress distribution in a static load test after the precast pile is constructed, and calculates according to the surface area and the stress distribution of the precast pile so as to determine pile forming quality.
2. A precast pile according to claim 1, characterized in that the outside of the steel pipe (1) is provided with a slot along the length direction for embedding a distributed optical fiber sensor (5).
3. A precast pile according to claim 1, characterized in that the diameter of the steel pipe (1) is 70-300 mm.
4. A precast pile according to claim 1, characterized in that the wall thickness of the steel pipe (1) is 6-20 mm.
5. A precast pile according to claim 1, characterized in that the number of anchor discs (3) is 1-4.
6. A precast pile according to claim 1, characterized in that the diameter of the anchor disc (3) is 2-5 times the diameter of the steel pipe (1).
7. A precast pile construction method for construction of a precast pile as set forth in claim 1, comprising the steps of:
s10: drilling pile holes in the foundation by adopting drilling machinery;
s20: removing bottom sediment of the pile hole;
s30: screwing the precast pile into the pile hole to a preset foundation burial depth;
s40: filling gaps between the precast piles and the foundation by grouting or pressing concrete;
s50: after the grouting construction of the precast pile is finished, the upper computer acquires temperature change data of different positions of the precast pile through an optical time domain reflectometer and a distributed optical fiber sensor (5);
s60: and comparing the temperature change data of different positions of the precast pile with a standard temperature curve of the grouting material curing process to determine filling and cementing quality of the grouting material.
8. A precast pile construction method as defined in claim 7, wherein the diameter of the pile hole is larger than the diameter of the steel pipe (101) and smaller than the diameter of the anchor disc (301).
9. A precast pile construction method as defined in claim 7, wherein the diameter of the pile hole satisfies the following condition: the diameter of the steel pipe (1) is 20-100 mm and the diameter of the anchor disc (3) is 200mm.
10. A precast pile construction method as defined in claim 7, wherein the grouting or press-cast concrete has a pressure of 0.8 to 1.5mpa.
11. A method of constructing a preformed pile according to claim 7, wherein said removing bottom sediment of said pile hole comprises: and cleaning the sediment at the bottom of the pile hole by air blowing, slurry pumping, slag drawing or slurry changing.
12. A precast pile quality inspection method for a precast pile according to claim 1 or a precast pile constructed by a precast pile construction method according to claim 7, characterized in that the quality inspection method comprises the steps of:
c10: after the construction of the precast pile is completed, applying a preset static load to the precast pile by adopting a press machine;
c20: the upper computer obtains stress distribution data of different positions of the precast pile through an optical time domain reflectometer and a distributed optical fiber sensor (5);
c30: calculating pile forming bearing capacity of the precast pile according to the obtained stress distribution data and the size data of the precast pile;
c40: and comparing the pile forming bearing capacity with the rated bearing capacity of the precast pile to judge pile forming quality.
13. A precast pile quality inspection method as claimed in claim 12, characterized in that the distributed optical fiber sensor (5) is located in a slot provided in the length direction outside the steel pipe (1) of the precast pile.
14. A precast pile quality inspection method as claimed in claim 12, characterized in that the distributed optical fibre sensor (5) comprises a photonic crystal fibre or a polymer fibre.
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| JP4208062B2 (en) * | 2000-08-08 | 2009-01-14 | 財団法人鉄道総合技術研究所 | Slip detection reinforcement pile for earth structure |
| CN205348237U (en) * | 2015-10-21 | 2016-06-29 | 中国电子工程设计院 | Cage bored concrete pile fiber grating lateral rigidity dynamic verification system inserts behind long spiral |
| CN105756056A (en) * | 2016-04-07 | 2016-07-13 | 中国十七冶集团有限公司 | Novel concrete screw pile construction method |
| CN110306610A (en) * | 2019-06-26 | 2019-10-08 | 宁波中淳高科股份有限公司 | A kind of built-in sensors method for embedding for concrete precast pile |
| CN114318992A (en) * | 2021-11-23 | 2022-04-12 | 固远晨通科技发展有限公司 | Intelligent spiral steel pile and construction method thereof |
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