Post-implantation type post-tensioned pre-stress large pipe pile body axial force testing device and testing method
Technical Field
The invention relates to the technical field of port engineering and foundation pile engineering, in particular to a post-implantation type post-tensioned prestressed large pipe pile body axial force testing device and a testing method.
Background
The main purpose of the static load test pile of the high-pile wharf is to test the total bearing capacity of the pile foundation, the lateral frictional resistance and the end resistance value of the soil body layering, test results are used for verifying the design bearing capacity and optimizing the design, and the importance is very outstanding. Wherein, the layered side frictional resistance and the end resistance value of the soil body are mainly realized by testing the axial force of the pile body sections.
At present, post-tensioning prestressed concrete large pipe piles are gradually popularized and used in large port engineering high-pile wharfs, and the piles have the advantages of low manufacturing cost, high tensile strength of pile bodies, high durability and the like. The post-tensioning prestressed concrete large pipe pile has a pile diameter of 1.2m or 1.4m, and is formed by connecting a plurality of sections of pile bodies into a longer pile body after being tensioned by steel strands. The length of the single section is not more than 10m, and the single section pile body is formed into a pile through high-speed rotation and high-temperature steam curing in the preparation process to form the single section pipe joint with the strength higher than C60. A plurality of single pile bodies are bonded by an adhesive, tensioned, grouted and tensioned to form a complete long pile, and meanwhile, a steel pile shoe is arranged at the pile tip to form a final post-tensioned prestressed large tubular pile finished product.
The method mainly comprises two types, namely a first type that a concrete strain gauge is pre-embedded in the process of manufacturing a single-joint pipe section pile to test the strain of the pile body, and data lines of all pipe section sensors are connected to form a test system, and the method has obvious defects that a ① sensor is low in survival rate after high-speed rotation and high-temperature steam curing, a ② multi-pipe section data line series connection process is difficult, a connection part is easy to damage in construction, and the test quality cannot be guaranteed.
Therefore, the applicant designs and develops a post-implantation type post-tensioned prestressing large pipe pile body axial force testing device and a testing method for solving the problems.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a post-implantation type post-tensioned prestressing large pipe pile body axial force testing device and a testing method.
The invention is realized in this way, a post-implantation post-tensioned prestressing large pipe pile shaft force testing device, which comprises a post-tensioned prestressing large pipe pile formed by splicing a plurality of concrete pipe piles; the method is characterized in that: the center of the pipe pile wall of each section of concrete pipe pile is pre-provided with two metal pipes with the diameter smaller than the wall thickness of the concrete pipe pile, and the two metal pipes are symmetrically distributed relative to the center of the concrete pipe pile; the lengths of the two metal pipes are equal to the length of the concrete pipe pile; after a plurality of concrete pipe piles are spliced, splicing metal pipes of adjacent concrete pipe piles to form a through sensor installation channel, and arranging Bragg fiber Bragg grating strain sensors for measuring axial force of a pile body at each boundary of a soil layer corresponding to a pile test position in the sensor installation channel; the Bragg fiber Bragg grating strain sensor is connected with a fiber optic lead; an optical fiber lead guide port communicated with the metal pipe is arranged on the inner side of the concrete pipe pile positioned at the upper part; the optical fiber lead connected with the Bragg optical fiber grating strain sensor extends out of the optical fiber lead guide port and is connected with the optical fiber grating demodulator; the sensor mounting channel is densely filled with a grouting agent, and the Bragg fiber grating strain sensor, the fiber lead, the metal pipe and the concrete pipe pile form an integrated structure after the grouting agent is solidified; and a calibration section sensor for calculating the comprehensive elastic modulus of the section is embedded in the position close to the pile top.
Preferably, 6-8 Bragg fiber grating strain sensors are arranged in each channel; the Bragg fiber Bragg grating strain sensor is formed by serially connecting armored fibers.
Preferably, the two ends of the Bragg fiber Bragg grating strain sensor are connected with the armored optical fiber through metal chucks.
Preferably, the outer diameter of the metal pipe is not more than 1/3 of the wall thickness of the concrete pipe pile.
Preferably, the distance from the optical fiber lead guiding opening to the pile top is 2 m.
The invention also discloses a manufacturing method of the post-implantation type post-tensioned prestressing large pipe pile body axial force testing device, which comprises the following steps: the method is characterized in that: the method comprises the following steps:
s1, manufacturing a concrete pipe joint: the center of the pipe pile wall of the concrete pipe pile is pre-provided with two metal pipes with the diameter smaller than the wall thickness of the concrete pipe pile, and the two metal pipes are symmetrically distributed relative to the center of the concrete pipe pile; the lengths of the two metal pipes are equal to the length of the concrete pipe pile;
s2, manufacturing a post-tensioned prestressed large tubular pile, firstly, lowering the concrete tubular pile with the steel pile tip to a designated position, then lowering other concrete tubular piles one by one, ensuring that metal pipes in adjacent concrete tubular piles are concentric, simultaneously ensuring that the connecting surfaces of the adjacent concrete tubular piles are sealed and attached, and then carrying out prestressed tensioning and anchor sealing;
s3, manufacturing a Bragg grating string strain string, armoring a plurality of Bragg fiber Bragg grating strain sensors connected with an optical cable to form the Bragg grating string strain string, wherein the positions and the lengths of the Bragg fiber Bragg grating strain sensors need to be calculated in advance, metal chucks are arranged at two ends of each Bragg fiber Bragg grating strain sensor to clamp and fix the Bragg fiber Bragg grating strain sensors, the Bragg fiber Bragg grating strain sensors are arranged at boundaries of soil layers at test pile positions, and 6-8 Bragg fiber Bragg grating strain sensors are arranged in each channel;
s4, arranging an armored Bragg fiber Bragg grating strain sensor with a metal chuck in the reserved metal pipe channel in series, enabling each strain point position to correspond to each soil layer boundary position after the pile is driven into the pile, and leading the armored fiber optic conductor out of the inner wall of the pile body in advance at a fiber optic conductor leading port;
s5, testing whether the Bragg fiber Bragg grating strain sensors work normally or not, and continuing to perform the next step if the Bragg fiber Bragg grating strain sensors at the boundary positions of each soil layer can work normally after the testing; if one or more Bragg fiber Bragg grating strain sensors do not work normally, the armored fiber optic cable needs to be lifted out through the fiber optic cable guide port for replacement or maintenance, and then lowering and detection are carried out until all the Bragg fiber Bragg grating strain sensors can work normally;
and S6, after confirming that all Bragg fiber Bragg grating strain sensors are normal, grouting the sensor installation channel at the pile top and the pile tip through the reserved grouting holes to ensure that the pile body is compact and has no gap, and regarding the whole pile body as a synchronous deformation state.
S6, pre-burying a calibration section sensor at a position close to the pile top;
s7, calculating to obtain a numerical curve of the comprehensive elastic modulus E of the pile body through the relation between stress and strain of the calibrated section, and calculating the axial force of the pile body of each tested section through E and strain epsilon; carrying out static load test and carrying out test acquisition by using a 1Hz fiber bragg grating demodulator to obtain pile body strain values of different parts of the pile body under different loads;
when the test pile reaches the ultimate bearing capacity, rely on
Ni=EAεi
Calculating axial force values of different sections of the pile, and thus calculating the extreme side resistance and the end resistance of the layered soil body; wherein N isiIs the axial force (kN) of the pile with the i-th section, E is the comprehensive elastic modulus (MPa) of the pile body, A is the area (m) of the pile section2),εiIs the i-th section pile body measurement strain (mu epsilon).
The invention has the advantages and technical effects that: by adopting the testing method, the invention avoids the sensor from the negative effects of rotary pile forming, steam curing and the like, repeated wiring and the like by embedding the metal pore channel at the center of the pile wall of the pile pipe and penetrating the armored optical fiber string sensor after pile manufacturing is finished, thereby improving the survival rate and the accuracy of the sensor; the sensor is positioned at the right center of the pile pipe wall, and the concrete quality at the center is uniform and good, so that the strain test effect is optimal; the post-grouting process of the pore channel not only protects the sensor, but also improves the installation efficiency and effect of the sensor and improves the accuracy and precision of the axial force test. The method is easy to popularize and has good effect.
Drawings
FIG. 1 is a schematic diagram of the present invention.
In the figure, 1, concrete pipe piles; 1-1, an optical fiber lead guide port; 2. a metal tube; 3. a Bragg fiber grating strain sensor; 4. an optical fiber wire; 5. a fiber grating demodulator; 6. a grouting agent; 7. calibrating a section sensor; 8. and (5) a steel pile tip.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, a post-implantation post-tensioned prestressed large pipe pile shaft force testing device comprises a post-tensioned prestressed large pipe pile formed by splicing a plurality of concrete pipe piles 1; the center of the pipe pile wall of each section of concrete pipe pile is pre-provided with two metal pipes 2 with the diameter smaller than the wall thickness of the concrete pipe pile, and the two metal pipes are symmetrically distributed relative to the center of the concrete pipe pile; the lengths of the two metal pipes are equal to the length of the concrete pipe pile; after a plurality of concrete pipe piles are spliced, splicing metal pipes of adjacent concrete pipe piles to form a through sensor installation channel, and arranging Bragg fiber Bragg grating strain sensors 3 for testing the axial force of a pile body at each boundary of a soil layer corresponding to a pile testing position in the sensor installation channel; the Bragg fiber Bragg grating strain sensor is connected with a fiber optic lead 4; an optical fiber lead guide port 1-1 communicated with the metal pipe is arranged on the inner side of the concrete pipe pile positioned at the upper part; the optical fiber lead connected with the Bragg fiber grating strain sensor extends out of a fiber lead guide port and is connected with a fiber grating demodulator 5, and the fiber grating demodulator belongs to the existing product and is used for measuring optical frequency; the sensor mounting channel is densely filled with a grouting agent 6, and the Bragg fiber grating strain sensor, the optical fiber lead, the metal pipe and the concrete pipe pile form an integrated structure after the grouting agent is solidified; and a calibration section sensor 7 for measuring the comprehensive elastic modulus of the pile body is embedded in the position close to the pile top.
Preferably, 6-8 Bragg fiber grating strain sensors are arranged in each channel; the Bragg fiber Bragg grating strain sensor is formed by serially connecting armored fibers.
Preferably, the two ends of the Bragg fiber Bragg grating strain sensor are connected with the armored fiber through metal chucks 3-1.
Preferably, the outer diameter of the metal pipe is not more than 1/3 of the wall thickness of the concrete pipe pile. Preferably, the outer diameter of the metal pipe is 44mm, and the wall thickness is 2 mm;
preferably, the distance from the optical fiber lead guiding opening to the pile top is 2 m.
The invention also discloses a manufacturing method of the post-implantation type post-tensioned prestressing large pipe pile body axial force testing device, which comprises the following steps: the method is characterized in that: the method comprises the following steps:
s1, manufacturing a concrete pipe joint: the center of the pipe pile wall of the concrete pipe pile is pre-provided with two metal pipes with the diameter smaller than the wall thickness of the concrete pipe pile, and the two metal pipes are symmetrically distributed relative to the center of the concrete pipe pile; the lengths of the two metal pipes are equal to the length of the concrete pipe pile; after each concrete pipe pile normally rotates to form a pile and is subjected to steam curing, the concrete pipe pile belongs to the prior art and is not described herein again;
s2, manufacturing a post-tensioned prestressed large pipe pile, firstly, lowering the concrete pipe pile with the steel pile tip 8 to a specified position, then lowering other concrete pipe piles one by one to ensure that metal pipes in adjacent concrete pipe piles are concentric and simultaneously ensure that the connecting surfaces of the adjacent concrete pipe piles are sealed and attached, and then, carrying out prestressed tensioning and anchor sealing, wherein the tensioning and anchor sealing belong to the conventional technology in the field and are not described herein;
s3, manufacturing a Bragg grating string strain string, armoring a plurality of Bragg fiber Bragg grating strain sensors connected with an optical cable to form the Bragg grating string strain string, wherein the positions and the lengths of the Bragg fiber Bragg grating strain sensors need to be calculated in advance, metal chucks are arranged at two ends of each Bragg fiber Bragg grating strain sensor to clamp and fix the Bragg fiber Bragg grating strain sensors, the Bragg fiber Bragg grating strain sensors are arranged at boundaries of soil layers at test pile positions, and 6-8 Bragg fiber Bragg grating strain sensors are arranged in each channel;
s4, arranging an armored Bragg fiber Bragg grating strain sensor with a metal chuck in the reserved metal pipe channel in series, enabling each strain point position to correspond to each soil layer boundary position after the pile is driven into the pile, and leading the armored fiber optic conductor out of the inner wall of the pile body in advance at a fiber optic conductor leading port;
s5, testing whether the Bragg fiber Bragg grating strain sensors work normally or not, and continuing to perform the next step if the Bragg fiber Bragg grating strain sensors at the boundary positions of each soil layer can work normally after the testing; if one or more Bragg fiber Bragg grating strain sensors do not work normally, the armored fiber optic cable needs to be lifted out through the fiber optic cable guide port for replacement or maintenance, and then lowering and detection are carried out until all the Bragg fiber Bragg grating strain sensors can work normally;
s6, after confirming that all Bragg fiber Bragg grating strain sensors are normal in state, grouting sensor pore channels on the pile top and the pile tip through reserved grouting holes and sensor installation channels by adopting HLC-VII grouting agent mixed with 3% of P.O42.5 cement to ensure that the pile body is compact and has no gap, and regarding the whole pile body as a synchronous deformation state;
s6, pre-burying a calibration section sensor at a position close to the pile top;
s7, calculating to obtain a numerical curve of the comprehensive elastic modulus E of the pile body through the relation between stress and strain of the calibrated section, and calculating the axial force of the pile body of each tested section through E and strain epsilon; carrying out static load test and carrying out test acquisition by using a 1Hz fiber bragg grating demodulator to obtain pile body strain values of different parts of the pile body under different loads;
when the test pile reaches the ultimate bearing capacity, rely on
Ni=EAεi
Calculating axial force values of different sections of the pile, and thus calculating the extreme side resistance and the end resistance of the layered soil body; wherein N isiIs the axial force (kN) of the pile with the i-th section, E is the comprehensive elastic modulus (MPa) of the pile body, A is the area (m) of the pile section2),εiIs the i-th section pile body measurement strain (mu epsilon).
The invention has the advantages and technical effects that: by adopting the testing method, the invention avoids the sensor from the negative effects of rotary pile forming, steam curing and the like, repeated wiring and the like by embedding the metal pore channel at the center of the pile wall of the pile pipe and penetrating the armored optical fiber string sensor after pile manufacturing is finished, thereby improving the survival rate and the accuracy of the sensor; the sensor is positioned at the right center of the pile pipe wall, and the concrete quality at the center is uniform and good, so that the strain test effect is optimal; the post-grouting process of the pore channel not only protects the sensor, but also improves the installation efficiency and effect of the sensor and improves the accuracy and precision of the axial force test. The method is easy to popularize and has good effect.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention, such as the type of sensor, the material of the metal tube, etc., are included in the scope of the present invention.