CN114439056B - System for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology and construction and detection method thereof - Google Patents
System for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology and construction and detection method thereof Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/02—Handling of bulk concrete specially for foundation or hydraulic engineering purposes
- E02D15/04—Placing concrete in mould-pipes, pile tubes, bore-holes or narrow shafts
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/08—Sinking workpieces into water or soil inasmuch as not provided for elsewhere
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/10—Deep foundations
- E02D27/12—Pile foundations
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G9/00—Installations of electric cables or lines in or on the ground or water
- H02G9/02—Installations of electric cables or lines in or on the ground or water laid directly in or on the ground, river-bed or sea-bottom; Coverings therefor, e.g. tile
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D2600/00—Miscellaneous
- E02D2600/10—Miscellaneous comprising sensor means
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Abstract
The invention discloses a system for detecting pile foundation bearing capacity by using a distributed piezoelectric cable impedance sensing technology, which is characterized in that: including multichannel impedance analyzer and distributed piezoelectric cable, distributed piezoelectric cable distributes along pile length direction and embeds in the pile body, distributed piezoelectric cable encircles pile body evenly distributed at least three, distributed piezoelectric cable and multichannel impedance analyzer electrical signal connection, distributed piezoelectric cable includes piezoelectric cable, piezoelectric cable wire and switch switching device, wherein piezoelectric cable and piezoelectric cable wire parallel distribution, a plurality of departments set up control switch switching device between piezoelectric cable wire and the piezoelectric cable, through the position that the multichannel impedance analyzer is to be detected of switch switching device control multichannel impedance analyzer, distributed piezoelectric cable wholly adopt the crust parcel constraint. The construction method and the detection method of the system are also disclosed. The system has stronger anti-skid capability and lower cost.
Description
Technical Field
The invention relates to the technical fields of pile foundation engineering and piezoresistance, in particular to a system for detecting pile foundation bearing capacity by using a distributed piezoelectric cable impedance sensing technology. The invention also relates to a construction method of the system for detecting the bearing capacity of the pile foundation by using the distributed piezoelectric cable impedance sensing technology. The invention also relates to a detection method of the system for detecting the pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology.
Background
The pile foundation engineering is an important component part of a building foundation, the quality of the pile foundation construction greatly affects the bearing capacity of the pile foundation in the construction process, and the stability of the pile foundation in the operation and maintenance process directly affects the stability of an upper building and the personal safety of a user, so that the detection of the pile foundation engineering in the construction process and the long-term operation and maintenance process becomes particularly important. However, the environment is complex in the field construction and operation and maintenance process, the pile foundation data acquisition environment is bad, and higher requirements are put on the detection of pile foundations. Only the change process of the bearing capacity of the pile foundation is accurately detected, detection signals are timely transmitted, analysis and early warning are carried out, and early warning is timely carried out on foundation damage possibly occurring in actual engineering, so that the research on the bearing characteristics in the pile foundation construction process and the operation and maintenance process can be better perfected.
Currently, common detection methods for detecting concrete cast-in-place piles and PHC pipe piles are a reinforcing bar meter, a resistance strain gauge, an optical fiber grating, a distributed optical fiber and the like. Fiber gratings and distributed fibers are most commonly used. Distributed optical fibers have a number of disadvantages: (1) The distributed optical fiber demodulator has high price and large size and is monopoly by foreign technology; (2) Air or dust enters the flange plate, so that laser cannot be transmitted, and optical fiber signals are lost; (3) The optical fiber is fragile, and needs outer layer steel strand protection, etc.
The piezoelectric cable is composed of four layers from inside to outside, namely an alloy, PVDF copper wires and a polyethylene protective layer. The piezoelectric cable has high tensile strength, and the working environment temperature range of the PVDF piezoelectric cable is wide and is within the range of-20 ℃ to 50 ℃. Piezoelectric coefficient g 33 Remains substantially unchanged. Nowadays, piezoelectric cables are often used in traffic flow detection and the like, and are less used in perimeter safety detection such as pile foundation detection and the like. The impedance of the piezoelectric cable is in linear relation with the acting force, and the piezoelectric cable has a great application prospect in the aspect of perimeter safety detection.
Disclosure of Invention
The invention aims to provide a system for detecting pile foundation bearing capacity by using a distributed piezoelectric cable impedance sensing technology, which has stronger anti-skid capability and lower cost. The invention further provides a construction method of the system for detecting the pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology. The invention further provides a detection method of the system for detecting the pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a system for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology is characterized in that: including multichannel impedance analyzer and distributed piezoelectric cable, distributed piezoelectric cable distributes along pile length direction and embeds in the pile body, distributed piezoelectric cable encircles pile body evenly distributed at least three, distributed piezoelectric cable and multichannel impedance analyzer electrical signal connection, distributed piezoelectric cable includes piezoelectric cable, piezoelectric cable wire and switch exchange device, wherein piezoelectric cable and piezoelectric cable wire parallel distribution, a plurality of departments set up switch exchange device between piezoelectric cable wire and the piezoelectric cable, through switch exchange device control multichannel impedance analyzer's position that will detect, distributed piezoelectric cable wholly adopt the crust parcel constraint.
Preferably, the pile body is a PHC pipe pile, a wiring groove is formed in the surface of the PHC pipe pile along a to-be-tested route designed in advance on the surface of the pile body, the distributed piezoelectric cables are placed in the wiring groove and are solidified and packaged by adopting a cementing material, and four groups of distributed piezoelectric cables are distributed on each test section at intervals of 90 degrees.
Preferably, the pile body is a cast-in-place pile, and 4 longitudinal ribs which are uniformly distributed on the cast-in-place pile reinforcement cage along the section at intervals of 90 degrees are respectively fixed with a distributed piezoelectric cable through binding wires and epoxy resin.
The invention also provides a construction method of the system for detecting pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology, which is characterized by comprising the following steps of: the method comprises the following steps:
(1) Burying a cable: the distributed piezoelectric cables are embedded into the pile body in a surrounding mode, four groups of distributed piezoelectric cables are distributed at 90-degree surrounding intervals of each detection section, and fixed points are adopted for fixation after the distributed piezoelectric cables are embedded;
(2) And (3) connecting a data acquisition line: the end heads of the piezoelectric cable wires are connected with a multichannel impedance analyzer to form a system for detecting pile foundation bearing capacity of the pile body by using the distributed piezoelectric cable impedance sensing technology for data acquisition.
Preferably, the pile body is a PHC pipe pile, and the construction steps include:
(1) Grooving wiring: a route to be tested is designed in advance along the surface of the pile body, then a cutting tool is used for grooving along the designed route, the depth and the width of the groove are based on the fact that distributed piezoelectric cables can be placed in the groove, four groups of distributed piezoelectric cables are distributed around each detection section at 90-degree intervals, and fixed points are adopted for fixation after the distributed piezoelectric cables are buried;
(2) Gluing protection: the wiring groove is filled, adhered and surface-protected by epoxy resin;
(3) And (3) connecting a data acquisition line: the end heads of the piezoelectric cable wires are connected with a multichannel impedance analyzer to form a distributed piezoelectric cable impedance sensing technology system for detecting the pile foundation bearing capacity of the PHC pipe pile for data acquisition.
Preferably, the pile body is a cast-in-place pile, and the construction steps include:
(1) Burying a cable: 4 longitudinal ribs uniformly distributed on the cast-in-place pile reinforcement cage at intervals of 90 degrees along the section are respectively fixed with a distributed piezoelectric cable through binding wires and epoxy resin;
(2) Pouring the pile body: hoisting a bored concrete pile reinforcement cage bound with the distributed piezoelectric cable into the pile hole, and then pouring concrete to enable the concrete to wrap the distributed piezoelectric cable;
(3) And (3) connecting a data acquisition line: the end heads of the piezoelectric cable wires are connected with a multichannel impedance analyzer to form a distributed piezoelectric cable impedance sensing technology system for detecting the bearing capacity of the pile foundation of the cast-in-place pile for data acquisition.
According to the detection method of the system for detecting pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology, provided by the invention, under the action of pile foundation bearing capacity, the pile body generates stress and strain so as to change the impedance of the piezoelectric cable sensor, and the axial force change of the bored concrete pile or the PHC pipe pile is judged by using the output signal of the impedance change, so that the side friction resistance and the pile end bearing capacity change of the bored concrete pile or the PHC pipe pile are calculated, and the detection method comprises the following steps:
(1) The axial impedance Z (h) of the piezoelectric cable is obtained through the test of the multichannel impedance analyzer, the axial strain epsilon (h) of the piezoelectric cable is calculated because the change of the impedance and the strain form a linear relation, the piezoelectric cable is fixed on the surface of the pile body, the axial deformation of the piezoelectric cable is consistent with the axial direction of the pile body under static load force, the strain epsilon (h) of the pile body is also obtained, and the stress sigma (h) of the pile body is as follows:
σ(h)＝ε(h)·E c wherein E is c Is the elastic modulus of the filling pile.
According to pile body stress sigma (Z), pile body axial force Q (h) is:
q (h) =σ (h) ·a, where a is the shaft cross-sectional area.
(2) The strain value of the distributed piezoelectric cable under different load deformations along the pile body can be obtained by testing the impedance change of the piezoelectric cable implanted into the pile body, and epsilon is set 1 (h) And epsilon 2 (h) Respectively testing the strain test values of the symmetrical parts of the pile body at the depth h along the horizontal load direction, and axially compressing the strain epsilon when one side of the pile body is pulled and the other side is pressed a (h) And bending strain value epsilon m (h) The method comprises the following steps of:
preferably, the multichannel impedance analyzer integrates transmitting and receiving signals, and the measured value is the impedance change of a plurality of piezoelectric cables under the conditions of 1kHz and 1V voltage; the multichannel impedance analyzer has the function of controlling the switch detection switching device, and can realize switch command emission.
Compared with the prior art, the invention has the beneficial effects that:
(1) Compared with the optical fiber, the piezoelectric cable is cheaper in price, the piezoelectric cable is solid, is not influenced by site dust and the like, and the inside of the distributed optical fiber is easily influenced by dust, air and the like, so that the accuracy of the distributed optical fiber detection is influenced;
(2) The piezoelectric cable is provided with a polyethylene protective layer, so that the piezoelectric cable is not easy to damage, and the distributed optical fiber is fragile and needs to be protected by an outer layer of steel stranded wires;
(3) The multichannel impedance analyzer is cheaper than the distributed optical fiber demodulator, the size of the portable multichannel impedance analyzer is smaller than that of the optical fiber demodulator, and the multichannel impedance analyzer is convenient to carry and the like, so that the large-area detection of the bearing capacity of the pile foundation can be realized.
Drawings
FIG. 1 is a schematic diagram of a distributed piezoelectric cable impedance sensing technology for detecting pile foundation bearing capacity according to embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of the multi-channel impedance analyzer in FIG. 1;
FIG. 3 is a schematic diagram of the distributed piezoelectric cable of FIG. 1;
fig. 4 is a schematic layout diagram of a distributed piezoelectric cable in a PHC pile according to embodiment 1 of the present invention;
FIG. 5 is a cross-sectional view of FIG. 4
Fig. 6 is a schematic diagram of a distributed piezoelectric cable arrangement in a bored pile according to embodiment 2 of the present invention;
fig. 7 is a cross-sectional view of fig. 6.
Reference numerals:
the device comprises a 1-pile body, a 2-distributed piezoelectric cable, a 3-multichannel impedance analyzer, a 4-piezoelectric cable lead, a 5-piezoelectric cable, a 6-switch exchange device, a 7-multichannel impedance analyzer switch, an 8-multichannel impedance analyzer detection depth knob, a 9-multichannel impedance analyzer impedance acquisition key, a 10-multichannel impedance analyzer wiring hole and an 11-heat shrink tube; 12. wiring grooves.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1 to 5, the system for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology provided in embodiment 1 of the present invention includes a multi-channel impedance analyzer 3 and a distributed piezoelectric cable 2, the distributed piezoelectric cable 2 is distributed along the length direction of the pile body and is disposed in the pile body 1, the distributed piezoelectric cable 2 is uniformly distributed at least three around the pile body 1, in this embodiment, 4 distributed piezoelectric cables 2 are electrically connected with the multi-channel impedance analyzer 3, the distributed piezoelectric cable 2 includes a piezoelectric cable 5, a piezoelectric cable wire 4 and a switch exchange device 6, wherein the piezoelectric cable 5 and the piezoelectric cable wire 4 are parallel distributed, a switch exchange device 6 is disposed between the piezoelectric cable wire 4 and the piezoelectric cable 5, the switch exchange device 6 controls the positions to be detected by the multi-channel impedance analyzer 3, and the distributed piezoelectric cable 2 is entirely wrapped and restrained by a sheath.
Referring to fig. 3-5, the distributed piezoelectric cable 2 is packaged by the heat shrink tube 11, so that the cable can be effectively protected. The pile body 1 is a PHC pipe pile, a wiring groove 12 is formed in the surface of the PHC pipe pile along a to-be-tested route which is designed in advance on the surface of the pile body, the distributed piezoelectric cables 2 are placed in the wiring groove 12 and are solidified and packaged by adopting cementing materials, four groups of the distributed piezoelectric cables 2 are distributed at intervals of 90 DEG on each test section, and the structure is convenient for the impedance distributed piezoelectric cables 2 to detect the axial force change of the pile body in a synchronous change mode.
Referring to fig. 1-4, the present invention further provides a construction method of the system for detecting pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology, which comprises the following steps:
(1) Grooving wiring: a route to be tested is designed in advance along the surface of the pile body, then a cutting tool is used for grooving along the designed route, the depth and the width of the groove are based on the fact that the distributed piezoelectric cables 2 can be placed in the groove, four groups of the distributed piezoelectric cables 2 are distributed at 90-degree surrounding intervals of each detection section, and fixed points are adopted for fixation after the distributed piezoelectric cables 2 are buried;
(2) Gluing protection: the wiring groove 12 is filled, adhered and surface-protected with epoxy resin;
(3) And (3) connecting a data acquisition line: the end of the piezoelectric cable wire 4 is connected with the multichannel impedance analyzer 3 to form a system for detecting the bearing capacity of the PHC pile foundation by the distributed piezoelectric cable 2 impedance sensing technology for data acquisition.
The method for detecting the pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology includes that under the action of the pile foundation bearing capacity, the pile body generates stress and strain so that the impedance of the distributed piezoelectric cable 2 changes, and the axial force change of the cast-in-place pile or the PHC pipe pile is judged by using an output signal of the impedance change, so that the side friction resistance and the pile end bearing capacity change of the cast-in-place pile or the PHC pipe pile are calculated, and the method comprises the following steps:
(1) The axial impedance Z (h) of the piezoelectric cable 5 is obtained through the test of the multichannel impedance analyzer 3, the axial strain epsilon (h) of the piezoelectric cable 5 is calculated due to the fact that the change of the impedance and the strain form a linear relation, the axial deformation of the piezoelectric cable 5 is consistent with the axial direction of the pile body under static load force due to the fact that the piezoelectric cable 5 is fixed on the surface of the pile body, the pile body strain is also the strain epsilon (h), and the pile body stress sigma (h) is as follows:
σ(h)＝ε(h)·E c wherein E is c The elastic modulus of the pile body 1;
according to pile body stress sigma (Z), pile body axial force Q (h) is:
q (h) =σ (h) ·a, where a is the shaft cross-sectional area.
(2) The strain value of the distributed piezoelectric cable under different load deformations along the pile body can be obtained by testing the impedance change of the piezoelectric cable 5 implanted into the pile body, and epsilon is set 1 (h) And epsilon 2 (h) Respectively testing the strain test values of the symmetrical parts of the pile body 1 at the depth h along the horizontal load direction, and axially compressing the strain epsilon when one side of the pile body is pulled and the other side is pressed a (h) And bending strain value epsilon m (h) The method comprises the following steps of:
the multichannel impedance analyzer 3 integrates transmitting and receiving signals, and the measured value is the impedance change of a plurality of piezoelectric cables under the conditions of 1kHz and 1V voltage; the multichannel impedance analyzer 3 has the function of controlling the switch detection switching device 6, and can realize switch command transmission.
Referring to fig. 1, 2, 3, 6 and 7, embodiment 2 of the present invention is substantially the same as embodiment 1, and differs only in that: the pile body 1 is a bored concrete pile, and 4 longitudinal ribs which are uniformly distributed on the bored concrete pile reinforcement cage along the section at intervals of 90 degrees are respectively fixed with a distributed piezoelectric cable 2 through binding wires and epoxy resin.
The construction steps comprise:
(1) Burying a cable: 4 longitudinal ribs uniformly distributed on the cast-in-place pile reinforcement cage at intervals of 90 degrees along the section are respectively fixed with a distributed piezoelectric cable 2 through binding wires and epoxy resin;
(2) Pouring the pile body: hoisting a bored concrete pile reinforcement cage bound with the distributed piezoelectric cable into the pile hole, and then pouring concrete to enable the concrete to wrap the distributed piezoelectric cable 2;
(3) And (3) connecting a data acquisition line: the end of the piezoelectric cable wire 4 is connected with the multichannel impedance analyzer 3 to form a system for detecting the bearing capacity of the pile foundation of the cast-in-place pile by the distributed piezoelectric cable 2 impedance sensing technology for data acquisition.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (8)
1. A system for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology is characterized in that: including multichannel impedance analyzer and distributed piezoelectric cable, distributed piezoelectric cable distributes along pile length direction and embeds in the pile body, distributed piezoelectric cable encircles pile body evenly distributed at least three, distributed piezoelectric cable and multichannel impedance analyzer electrical signal connection, distributed piezoelectric cable includes piezoelectric cable, piezoelectric cable wire and switch exchange device, wherein piezoelectric cable and piezoelectric cable wire parallel distribution, a plurality of departments set up switch exchange device between piezoelectric cable wire and the piezoelectric cable, through switch exchange device control multichannel impedance analyzer's position that will detect, distributed piezoelectric cable wholly adopt the crust parcel constraint.
2. The system for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology according to claim 1, wherein: the pile body is a PHC pipe pile, a wiring groove is formed in the surface of the PHC pipe pile along a route to be tested, the distributed piezoelectric cables are placed in the wiring groove and are solidified and packaged by adopting cementing materials, and four groups of distributed piezoelectric cables are distributed at intervals of 90 degrees in each test section.
3. The system for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology according to claim 1, wherein: the pile body is a filling pile, and 4 longitudinal ribs which are uniformly distributed on the filling pile reinforcement cage along the section at intervals of 90 degrees are respectively fixed with a distributed piezoelectric cable through binding wires and epoxy resin.
4. A method of constructing a system for detecting pile foundation bearing capacity using distributed piezoelectric cable impedance sensing technology as claimed in claim 1, wherein: the method comprises the following steps:
(1) Burying a cable: the distributed piezoelectric cables are embedded into the pile body in a surrounding mode, four groups of distributed piezoelectric cables are distributed at 90-degree surrounding intervals of each detection section, and fixed points are adopted for fixation after the distributed piezoelectric cables are embedded;
(2) And (3) connecting a data acquisition line: the end heads of the piezoelectric cable wires are connected with a multichannel impedance analyzer to form a system for detecting pile foundation bearing capacity of the pile body by using the distributed piezoelectric cable impedance sensing technology for data acquisition.
5. The construction method of the system for detecting pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology according to claim 4, wherein the construction method comprises the following steps: the pile body is PHC pipe pile, and the construction steps comprise:
(1) Grooving wiring: a route to be tested is designed in advance along the surface of the pile body, then a cutting tool is used for grooving along the designed route, the depth and the width of the groove are based on the fact that distributed piezoelectric cables can be placed in the groove, four groups of distributed piezoelectric cables are distributed around each detection section at 90-degree intervals, and fixed points are adopted for fixation after the distributed piezoelectric cables are buried;
(2) Gluing protection: the wiring groove is filled, adhered and surface-protected by epoxy resin;
(3) And (3) connecting a data acquisition line: the end heads of the piezoelectric cable wires are connected with a multichannel impedance analyzer to form a distributed piezoelectric cable impedance sensing technology system for detecting the pile foundation bearing capacity of the PHC pipe pile for data acquisition.
6. The construction method of the system for detecting pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology according to claim 4, wherein the construction method comprises the following steps: the pile body is a filling pile, and the construction steps comprise:
(1) Burying a cable: 4 longitudinal ribs uniformly distributed on the cast-in-place pile reinforcement cage at intervals of 90 degrees along the section are respectively fixed with a distributed piezoelectric cable through binding wires and epoxy resin;
(2) Pouring the pile body: hoisting a bored concrete pile reinforcement cage bound with the distributed piezoelectric cable into the pile hole, and then pouring concrete to enable the concrete to wrap the distributed piezoelectric cable;
(3) And (3) connecting a data acquisition line: the end heads of the piezoelectric cable wires are connected with a multichannel impedance analyzer to form a distributed piezoelectric cable impedance sensing technology system for detecting the bearing capacity of the pile foundation of the cast-in-place pile for data acquisition.
7. A method of detecting a system for detecting pile foundation bearing capacity using distributed piezoelectric cable impedance sensing technology as claimed in claim 1, wherein: under the effect of pile foundation bearing force, pile body produces stress and strain, so that the impedance of piezoelectricity cable sensor changes, utilizes the output signal of impedance change to judge the axial force change of bored concrete pile or PHC tubular pile to calculate the change of the side friction resistance and pile tip bearing force of bored concrete pile or PHC tubular pile, include:
(1) The axial impedance Z (h) of the piezoelectric cable is obtained through the test of the multichannel impedance analyzer, the axial strain epsilon (h) of the piezoelectric cable is calculated because the change of the impedance and the strain form a linear relation, the piezoelectric cable is fixed on the surface of the pile body, the axial deformation of the piezoelectric cable is consistent with the axial direction of the pile body under static load force, the strain epsilon (h) of the pile body is also obtained, and the stress sigma (h) of the pile body is as follows:
σ(h)＝ε(h)·E c wherein E is c Is the elastic modulus of the pile body.
According to pile body stress sigma (Z), pile body axial force Q (h) is:
q (h) =σ (h) ·a, where a is the shaft cross-sectional area,
(2) The strain value of the distributed piezoelectric cable under different load deformations along the pile body can be obtained by testing the impedance change of the piezoelectric cable implanted into the pile body, and epsilon is set 1 (h) And epsilon 2 (h) Respectively testing the strain test values of the symmetrical parts of the pile body at the depth h along the horizontal load direction, and axially compressing the strain epsilon when one side of the pile body is pulled and the other side is pressed a (h) And bending strain value epsilon m (h) The method comprises the following steps of:
8. the method for detecting the pile foundation bearing capacity by using the distributed piezoelectric cable impedance sensing technology according to claim 7, wherein the method comprises the following steps: the multichannel impedance analyzer integrates transmitting and receiving signals, and the measured value is the impedance change of a plurality of piezoelectric cables under the conditions of 1kHz and 1V voltage; the multichannel impedance analyzer has the function of controlling the switch detection switching device, and can realize switch command emission.
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| BOTDR分布式检测技术在复杂地层钻孔灌注桩测试中的应用研究;魏广庆;施斌;余小奎;朴春德;朱友群;王宝军;;工程地质学报(06);第826-832页 * |
| 浅谈人工挖孔桩在挖孔过程中存在的问题及对策;杨建等;《科技信息》(第第36期期);第466页 * |
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