CN111622275A - Concrete pile foundation detection method - Google Patents
Concrete pile foundation detection method Download PDFInfo
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- CN111622275A CN111622275A CN202010454634.XA CN202010454634A CN111622275A CN 111622275 A CN111622275 A CN 111622275A CN 202010454634 A CN202010454634 A CN 202010454634A CN 111622275 A CN111622275 A CN 111622275A
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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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M7/00—Vibration-testing of structures; Shock-testing of structures
- G01M7/02—Vibration-testing by means of a shake table
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M7/00—Vibration-testing of structures; Shock-testing of structures
- G01M7/02—Vibration-testing by means of a shake table
- G01M7/025—Measuring arrangements
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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
Abstract
The invention relates to a concrete pile foundation detection method and belongs to the field of constructional engineering detection. The method is used for carrying out leveling treatment on the pile top of the pile foundation to be detected, a plurality of measuring sensors used for measuring the pile foundation to be detected are installed on the pile top of the pile foundation to be detected, the time-course curve of the acceleration response of the pile top is actually measured in a low-energy transient excitation mode, stable response signals can be obtained under each set frequency of the stable excitation, the excitation force of the stable excitation is adjusted according to the pile diameter, the pile length and the soil constraint condition around the pile, the average wave speed of the pile body is detected, whether pile body breakage and crack defects exist is judged, vertical compression resistance detection is carried out on the pile foundation to be detected, and vertical anti-pulling detection is carried out on the single pile foundation. The invention not only can detect the integrity of the pile foundation, but also can detect the compression resistance and the uplift resistance of the pile foundation to be detected.
Description
Technical Field
The invention relates to the field of constructional engineering detection, in particular to a concrete pile foundation detection method.
Background
The pile foundation engineering is the foundation for the development of the building engineering, exists at the bottom of the building, can not be seen by naked eyes, but plays an important role in the whole building engineering, and because the pile foundation engineering has the characteristics of specialty and concealment, the quality of the pile foundation influences the quality of the whole engineering, and the high-quality pile foundation engineering is beneficial to scientific and strict pile foundation detection, so that the pile foundation detection can not be replaced for the effect of the building engineering.
In order to solve the technical problems, the invention patent named 'a method for detecting integrity and defects of a building engineering pile foundation (publication number: CN 110735452A)' is searched, the method comprises the steps of drilling holes on the sides of a plurality of pile foundations to be detected, detecting the holes in the holes, generating a time-depth signal diagram of each pile foundation according to signals with different depths, correcting the time-depth signal diagram according to the detection signals of the complete pile foundation, and determining the integrity and the defects of the pile foundations according to the corrected time-depth signal diagram, so that the influence of ground soil layer nonuniformity on the detection of the pile foundations is eliminated.
The above prior art solutions have the following drawbacks: 1. the detection target of the prior art scheme is single, and only the integrity of the pile foundation can be detected, but the compression resistance and the uplift resistance of the pile foundation cannot be detected; meanwhile, the prior art scheme mainly selects the pile foundation with the complete pile body to carry out drilling depth detection, and accordingly the defect of the existing pile foundation to be detected is judged, the detection method has poor accuracy, and the defect of pile breakage or cracking of the pile foundation cannot be detected.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a concrete pile foundation detection method which not only can detect the integrity of a pile foundation, but also can detect the compression resistance and the uplift resistance of the pile foundation to be detected.
The above object of the present invention is achieved by the following technical solutions:
a method for detecting concrete pile foundation includes such steps as testing the pile foundation composed of pile top and pile body,
s1: carrying out leveling treatment on the pile top of the pile foundation to be detected, enabling the concrete quality and the section size of the pile top of the pile foundation to be detected to be equal to the design conditions of a pile body in a construction drawing, and enabling the central line of the pile foundation to be detected and the top surface (basic) of the pile top to be mutually vertical;
s2: installing a plurality of measuring sensors for measuring the pile foundation to be measured on the pile top of the pile foundation to be measured, enabling a plane formed by the plurality of measuring sensors to be vertical to the top surface of the pile foundation to be measured, actually measuring a time-course curve of acceleration response of the pile top in a low-energy transient excitation mode, ensuring that stable excitation can obtain stable response signals under each set frequency, and adjusting the excitation force of the stable excitation according to the pile diameter, the pile length and the soil constraint condition around the pile;
s3: detecting the average wave velocity of the pile body, detecting the integrity of the pile body by a wave theory analysis method and a frequency domain analysis method, and judging whether the pile body has the defects of pile breakage and crack;
s4: after the step S2 and the step S3 are completed, the vertical compression resistance of the pile foundation to be tested is detected,
firstly, applying vertical pressure load to a pile foundation to be detected step by step through a pile foundation compression resistance detection device, and then measuring and reading the settlement of the pile foundation to be detected after each step of pressure load is completed; then, unloading the vertical pressure load step by step, and measuring and reading the settlement of the pile foundation to be detected step by step;
s5: after the vertical compression resistance detection is finished, the single pile foundation is subjected to vertical anti-pulling detection,
vertical tensile load is applied to the pile foundation that awaits measuring step by step through pile foundation resistance to plucking detection device earlier, all surveys the deformation of pulling up of the pile foundation that awaits measuring after every stage tensile load is accomplished after that, then unloads vertical pressure load step by step, surveys the deformation of pulling up of the pile foundation that awaits measuring step by step.
By adopting the technical scheme, the integrity, the compression resistance and the uplift resistance of the pile foundation to be detected can be simultaneously detected by leveling the pile top, arranging the measuring sensor, and carrying out step-by-step loading and step-by-step unloading on the time-course curve of the acceleration response of the actually measured pile top, reading the reading of the pressure gauge or the tension gauge step by step and the like; meanwhile, the integrity of the pile body is detected based on a fluctuation theory analysis method and a frequency domain analysis method, and whether the pile body has the defects of pile breakage and cracks is judged on the basis, so that the detection result is more perfect.
In a preferred example, the invention may be further configured that, in the step S4, the step of detecting the vertical compression resistance of the pile foundation to be detected specifically includes the following steps,
s4.1, when the pile foundation to be detected reaches the rest period required by the construction specification of the building engineering, and after the pile foundation is subjected to low-strain detection, carrying out leveling treatment on the pile top of the pile foundation to be detected, so that the concrete quality and the section size of the pile top of the pile foundation to be detected are equal to the design conditions of the pile body in the construction drawing;
s4.2, arranging a pile foundation compression resistance detection device which is provided with a jack and is used for applying vertical load to the pile foundation to be detected on the pile foundation to be detected, and applying vertical pressure load to the foundation pile to be detected through the jack;
s4.3, when pressure load is applied to the pile foundation to be tested, loading the pile foundation to be tested by adopting a slow-speed load maintaining method, adding the next stage of load after each stage of load is relatively stable, and measuring and reading the settlement of the pile foundation to be tested, wherein the interval time for measuring and reading the settlement of the pile foundation to be tested is the time after each stage of loading is finished;
and S4.4, after the compression resistance detection of the pile foundation reaches the maximum applied load value, the load in the step S4.3 is unloaded in a grading mode, the unloading value of each grade is twice of the loading value during unloading, the load is measured and read once every 15min after unloading, the load is read once every 30min after reading twice, then the load of one grade is unloaded, and the load is measured and read once every 3h after all the loads are unloaded.
By adopting the technical scheme, the vertical pressure load is applied to the foundation pile to be tested through the jack, the settlement of the pile foundation to be tested is measured and read after each stage of loading is finished, and the measurement time and times are strictly controlled, so that the vertical compression resistance detection result of the pile foundation to be tested is more accurate and credible.
In a preferred example, the invention may be further configured that, in step S4.2, the pile foundation compression resistance detection device includes a pile foundation to be detected, a sleeper stack, a first steel beam, a first jack, an oil pressure gauge, and a counterweight block made of precast concrete, the sleeper stacks are symmetrically arranged on two sides of the pile foundation to be detected, the first steel beam is erected between the tops of the two sleeper stacks, the first jack is located between the top of the pile foundation and the middle of the first steel beam, the counterweight blocks are multiple and are all erected at the upper end of the first steel beam, and the oil pressure gauge is arranged on the pile foundation to be detected.
By adopting the technical scheme, the balancing weight is used for applying a reverse force to the first steel cross beam, the oil pressure gauge is used for measuring the pressure applied to the pile foundation to be detected by the first jack, and the pile foundation compression resistance detection device can be used for carrying out compression resistance detection on the pile foundation to be detected.
In a preferred example, the invention may be further configured that, in the step S4, the step of detecting the vertical compression resistance of the pile foundation to be detected specifically includes the following steps,
s5.1, in a rest period required by construction specification of the building engineering, after the pile foundation to be detected is subjected to vertical compression resistance detection, leveling the pile top of the pile foundation to be detected again to ensure that the concrete quality and the section size of the pile top of the pile foundation to be detected are equal to the design conditions of the pile body in the construction drawing;
s5.2, arranging a pile foundation anti-pulling detection device which is provided with a jack and is used for applying vertical pulling force to the pile foundation to be detected on the pile foundation to be detected, and applying vertical pulling force load to the foundation pile through the jack;
s5.3, when a tensile load is applied to the pile foundation to be tested, loading is carried out by adopting a slow load maintaining method, the next stage of load is added after the load of each stage is relatively stable, and the rising deformation of the pile foundation to be tested is measured and read, wherein the interval time for measuring and reading the rising deformation of the pile foundation to be tested is the time after the loading of each stage is completed;
and S5.4, when the termination detection condition of the vertical uplift detection is met, terminating the detection, unloading and reading and recording the resilience variable of the pile foundation to be detected.
By adopting the technical scheme, the vertical tensile load is applied to the foundation pile to be tested through the jack, the lifting deformation of the pile foundation to be tested is measured and read after each stage of loading is finished, and the measurement time and times are strictly controlled, so that the vertical compression detection result of the pile foundation to be tested is more accurate and credible.
In a preferred example, the pile foundation uplift detection device may further be configured that, in step S5.2, the pile foundation to be detected includes two pile foundations to be detected, two support tables, a second steel beam and a dial indicator, the two support tables are symmetrically distributed on two sides of the pile foundation to be detected, the second steel beam is located above the pile foundation to be detected, the two support tables are respectively provided with a second jack, output ends of the two second jacks are respectively connected to two sides of the second steel beam, a mechanical fixture or a steel bar is connected between the middle of the second steel beam and the pile foundation to be detected, and the dial indicator is provided with a plurality of dial indicators and is installed on two sides of a pile body of the pile foundation to be.
By adopting the technical scheme, the jack is used for applying tension to the first steel cross beam so as to apply tension to the pile foundation to be detected, the dial indicator is used for measuring the rising deformation applied to the pile foundation to be detected, and the pile foundation uplift detection device can be used for carrying out uplift detection on the pile foundation to be detected.
In a preferred example, the present invention may be further configured that, in step S2, when the pile foundation to be tested is a solid pile, the position of the excitation point of the pile foundation to be tested is located at the central portion of the pile foundation to be tested, and the installation position of the measurement sensor is located at a radius from the pile center 2/3; when the pile foundation to be detected is a hollow pile, the excitation point of the pile foundation to be detected and the installation position of the measuring sensor are on the same horizontal plane, the included angle formed by the horizontal plane and the central connecting line of the pile is 90 degrees, and the excitation point and the installation position of the measuring sensor are 1/2 parts of the thickness of the pile wall. By adopting the technical scheme, the solid pile foundation and the hollow pile foundation can be more accurately detected, so that the integrity of the pile foundation can be more accurately detected.
The present invention may further be configured in a preferred example, in step S2, the time interval length of the time domain signal recording of the time course curve should last for not less than 5min after the time of 2L/c; the upper limit of the frequency range of amplitude-frequency signal analysis should not be less than 2000 Hz. By adopting the technical scheme, more correlation points based on the time period length and the frequency range can be obtained, so that a more accurate time-course curve of the acceleration response of the actually measured pile top is obtained.
In a preferred example, the invention may be further configured that, in step S4.3 and step S5.3, the load amount applied to each stage is 1/8 of the design limit bearing capacity, the first stage addition amount is 1/4 of the characteristic value of the bearing capacity, after each stage of load reaches relative stability, the next stage of load cannot be applied until the pile foundation compression resistance detection reaches the maximum applied load value, and then the loading is terminated; after each stage of applied pressure load is finished, measuring and reading the settlement amount or the rising deformation amount of the pile top at 5min, 15min, 30min, 45min and 60min in sequence, and then measuring and reading the settlement amount or the rising deformation amount of the pile top once every 30 min.
By adopting the technical scheme, the stability of each stage of load is improved by strictly controlling the load quantity applied to each stage, and meanwhile, the time for measuring and reading the settlement quantity of the pile top is strictly controlled, so that people can be helped to more accurately observe the influence of the pressure or the tension on the pile foundation to be measured.
In a preferred example, the present invention may be further configured that, in the step S4.2, the load amount of the vertical pressure load is converted by the jack calibration curve, and is measured and read by the oil pressure gauge, and the load-oil pressure value corresponding table is established on site.
By adopting the technical scheme, the calibration curve can help people to accurately control the pressure of the pile foundation to be tested, and the load-oil pressure value corresponding table can be convenient for personnel to carry out field operation.
The present invention in a preferred example may be further configured to terminate loading when a vertical tensile load is applied if one of four conditions occurs:
a. under the action of a certain level of load, the upward pulling amount of the pile top is 5 times larger than that under the action of the previous level of upward pulling load;
b. controlling the pulling amount of the pile top according to the pulling amount of the pile top, and when the accumulated pulling amount of the pile top exceeds 100 mm;
c. controlling according to the tensile strength of the steel bar, wherein the pulling load on the pile top reaches 0.9 time of the standard value of the strength of the steel bar;
d. and for the pile foundation to be tested which is subjected to acceptance sampling detection, the maximum upper pulling load value of the design requirement is reached.
By adopting the technical scheme, the influence of the vertical pressure load on the pile foundation to be measured can be reduced, so that the measurement accuracy of the vertical pressure load is improved.
In summary, the invention includes at least one of the following beneficial technical effects:
1. according to the invention, the integrity, the compression resistance and the pulling resistance of the pile foundation to be detected can be detected simultaneously by leveling the pile top, arranging the measuring sensor, carrying out step-by-step loading and unloading on the time-course curve of the acceleration response of the actually measured pile top, reading the reading of a pressure gauge or a tension gauge step by step and the like; meanwhile, the integrity of the pile body is detected based on a fluctuation theory analysis method and a frequency domain analysis method, and whether the pile body has the defects of pile breakage and cracks is judged on the basis, so that the detection result is more perfect.
2. Because the anti-pulling detection is set to be carried out after the anti-pulling detection is finished, when the anti-pulling or anti-pulling detection is carried out on the pile foundation to be detected, the detection device is not required to be provided with too many jacks at one time, so that the pressure or the tension of the jack on the top of the pile foundation to be detected is smaller, the anti-pulling and anti-pulling detection result of the invention is more accurate, and the pile top part of the pile foundation to be detected is not damaged.
3. The compression-resistant detection device and the anti-pulling detection device provided by the invention have the advantages of simple structure, convenience in addition and low construction cost.
Drawings
FIG. 1 is a schematic flow chart of a concrete pile foundation detection method according to the present invention;
FIG. 2 is a schematic structural diagram of the pile foundation compression resistance detection device of the invention;
FIG. 3 is a schematic structural diagram of the pile foundation uplift detection device of the invention; (ii) a
FIG. 4 is a schematic view of the process of detecting the compressive resistance of the pile foundation to be detected according to the present invention;
fig. 5 is a schematic flow chart of the uplift detection of the pile foundation to be detected according to the invention.
Reference numerals: 1. a pile foundation compression resistance detection device 11, a sleeper pile 12, an oil pressure gauge 13, a balancing weight 14, a first steel beam 15 and a first jack; 2. a pile foundation uplift detection device 21, a support table 22, a dial indicator 23, a second steel beam 24, a mechanical clamp or a steel bar 25 and a second jack; 3. a pile foundation to be tested; 4. a main beam.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, the invention provides a concrete pile foundation detection method, which comprises a pile foundation to be detected consisting of a pile top and a pile body, and comprises the following steps,
installing a plurality of measuring sensors for measuring the pile foundation to be measured on the pile top of the pile foundation to be measured, actually measuring the time-course curve of the acceleration response of the pile top in a low-energy transient excitation mode, ensuring that the steady-state excitation can obtain stable response signals under each set frequency, adjusting the excitation force of the steady-state excitation according to the constraint conditions of the pile diameter, the pile length and the soil around the pile, detecting the average wave speed of the pile body, judging whether the pile body has the defects of pile breakage and crack, detecting the vertical compression resistance of the pile foundation to be measured, and detecting the vertical anti-pulling of the single pile foundation
S1: carrying out leveling treatment on the pile top of the pile foundation to be detected, enabling the concrete quality and the section size of the pile top of the pile foundation 3 to be detected to be equal to the design conditions (basically) of the pile body in the construction drawing, and enabling the central line of the pile foundation to be detected and the top surface (basically) of the pile top to be perpendicular to each other;
during actual operation, after pile foundation 3 that awaits measuring reaches the off period that building engineering construction standard required, just can carry out leveling to the pile bolck of pile foundation, the step of carrying out leveling to the pile bolck of pile foundation includes following step:
a. chiseling off loose and damaged pile tops on the pile foundation 3 to be detected to expose the hard concrete surface of the pile foundation 3 to be detected;
b. leveling and cleaning the pile top surface of the pile foundation 3 to be detected, and ensuring that no water is accumulated on the pile top surface of the pile foundation 3 to be detected;
c. cutting off exposed main ribs of the pile top, which obstruct normal testing, on the pile foundation 3 to be tested;
d. when the pile top of the pile foundation 3 to be tested is connected with a bearing platform or a cushion layer of the building engineering, the large section impedance change exists at the pile top, which is equivalent to influence on a test signal, so that the pile top of the pile foundation 3 to be tested is disconnected with a concrete bearing platform; when the side surface of the pile top is connected with the cushion layer of the building engineering, the pile foundation 3 to be tested and the cushion layer are disconnected unless the test signal is not influenced.
S2: installing a plurality of measuring sensors for measuring the pile foundation to be measured on the pile top of the pile foundation to be measured, enabling a plane formed by the plurality of measuring sensors to be vertical to the top surface of the pile foundation to be measured, actually measuring a time-course curve of acceleration response of the pile top in a low-energy transient excitation mode, ensuring that stable excitation can obtain stable response signals under each set frequency, and adjusting the excitation force of the stable excitation according to the pile diameter, the pile length and the soil constraint condition around the pile;
preferably, in step S2, when the pile foundation to be tested is a solid pile, the position of the excitation point of the pile foundation to be tested is located at the center of the pile foundation to be tested, and the installation position of the measuring sensor is located at a radius from the pile center 2/3; when the pile foundation to be detected is a hollow pile, the excitation point of the pile foundation to be detected and the installation position of the measuring sensor are on the same horizontal plane, the included angle formed by the horizontal plane and the central connecting line of the pile is 90 degrees, and the excitation point and the installation position of the measuring sensor are 1/2 parts of the thickness of the pile wall. Therefore, the invention can more accurately detect the solid pile foundation and the hollow pile foundation, thereby ensuring that the invention can more accurately detect the integrity of the pile foundation.
Preferably, in step S2, the time interval length of the time domain signal record of the time interval curve should last for not less than 5min after 2L/c; the upper limit of the frequency range of amplitude-frequency signal analysis should not be less than 2000 Hz. Therefore, the method can obtain more associated points based on the time period length and the frequency range, so that a more accurate time-course curve of the acceleration response of the actually measured pile top is obtained.
In actual work, transient excitation and steady-state excitation (with low energy) are both in the prior art, and are both excitation waves emitted from an excitation source at the top of a pile foundation to be detected, and are detected through the pile foundation to be detected of a detector, so the transient excitation and the steady-state excitation can be collectively called as excitation. The excitation points (including transient excitation points and steady excitation points) and the installation positions of the measuring sensors in the invention are all required to avoid the influence of main bars of the reinforcement cage, and the excitation direction of low-energy transient excitation is required to be along the direction of a pile axis. During actual work, transient excitation should pass a field knocking test, and an excitation force hammer and a hammer pad with proper weight are selected. In actual work, the (low-energy) transient excitation in the invention is preferably to use wide pulse to obtain the reflected signal of the defect at the bottom or the lower part of the pile body, and preferably to use narrow pulse to obtain the reflected signal of the defect at the upper part of the pile body.
S3: detecting the average wave velocity of the pile body, detecting the integrity of the pile body by a wave theory analysis method and a frequency domain analysis method, and judging whether the pile body has the defects of pile breakage and crack;
in actual operation, in step S3, when the average wave velocity of the pile body is detected, the wave velocity of the pile body may be preliminarily set according to the test values of the local piles of the same type.
S4: after the step S2 and the step S3 are completed, detecting the vertical compression resistance of the pile foundation to be detected, firstly applying vertical pressure load to the pile foundation to be detected step by step through a pile foundation compression resistance detection device, and then measuring and reading the settlement of the pile foundation to be detected after each step of pressure load is completed; then, unloading the vertical pressure load step by step, and measuring and reading the settlement of the pile foundation to be detected step by step;
in actual work, the vertical compression resistance detection steps of the invention for the pile foundation are concretely as follows,
s4.1, after the pile foundation 3 to be tested reaches the rest period required by the construction specification of the building engineering and the pile foundation is subjected to low-strain detection, carrying out leveling treatment on the pile top of the pile foundation, so that the concrete quality and the section size of the pile top of the pile foundation 3 to be tested are equal to the design conditions (basically) of the pile body in the construction drawing;
the invention can process the pile top (pile head) of the pile foundation to be tested to meet the requirements of the compression and compression resistance detection, and can reduce the influence of the pile top on the compression and compression resistance detection, thereby directly improving the quality of the test signal.
S4.2, arranging a pile foundation compression resistance detection device 1 which is provided with a jack 5 and is used for applying vertical load to the pile foundation 3 to be detected on the pile foundation 3 to be detected, and applying vertical pressure load to the pile foundation to be lateral base through the jack 5;
preferably, the load capacity of the vertical pressure load is converted by a calibration curve of the jack 5, and is measured and read by the oil pressure gauge 12, and a load-oil pressure value corresponding table is established on site. The calibration curve can help people to accurately control the pressure of the pile foundation to be tested, and the load-oil pressure value corresponding table can facilitate the field operation of personnel.
In actual operation, the pile foundation compression resistance detection device 1 comprises a pile foundation 3 to be detected, a sleeper pile 11, a first steel beam 14, a first jack 15, an oil pressure gauge 12 and a balancing weight 13 made of precast concrete, the sleeper piles 11 are symmetrically arranged on two sides of the pile foundation 3 to be detected, the first steel beam 14 is erected between the tops of the two sleeper piles 11, the first jack 15 is located between the top of the pile foundation and the middle of the first steel beam 14, the balancing weights 13 are multiple and are all erected at the upper end of the first steel beam 14, and the oil pressure gauge 12 is arranged on the pile foundation 3 to be detected.
In the technical scheme, the balancing weight 13 is used for applying a reverse force to the first steel beam 14), the oil pressure gauge 12) is used for measuring the pressure applied by the first jack 15) to the pile foundation 3) to be detected, and the pile foundation compression resistance detection device 1) can be used for carrying out compression resistance detection on the pile foundation to be detected.
In actual operation, as shown in fig. 2, the first jack 15) of the present invention is placed on the pile foundation 3 to be tested, and is mainly used for pushing the first steel beam 14 (carrier beam), and 2 or 3 jacks of 5000kN may be adopted.
S4.3, when pressure load is applied to the pile foundation 3 to be tested, loading the pile foundation 3 to be tested by adopting a slow-speed load-maintaining method (namely step-by-step loading), adding the next stage of load after the load of each stage is relatively stable, and measuring and reading the settlement of the pile foundation to be tested, wherein the interval time for measuring and reading the settlement of the pile foundation to be tested is after the loading of each stage is finished;
in step S4.3, if the settling volume or the rising deformation of the pile foundation 3 to be tested in 1 hour is not greater than 0.1mm twice, it is determined that the settling volume of the current-stage pile foundation 3 to be tested has reached relatively stable, and the next-stage load can be applied to the pile foundation 3 to be tested. Therefore, people can accurately judge whether the pile foundation 3 to be tested is in a stable state, and then help people judge whether a next-stage load needs to be applied.
Preferably, in step S4.3, the load applied to each stage is 1/8 of the design limit bearing capacity, the first stage addition is 1/4 of the characteristic value of the bearing capacity, and after the load of each stage is relatively stable, the next stage load can be applied until the compressive resistance of the pile foundation is detected to reach the maximum applied load value, and then the loading is terminated; after each stage of applied pressure load is finished, measuring and reading the settlement amount or the rising deformation amount of the pile top at 5min, 15min, 30min, 45min and 60min in sequence, and then measuring and reading the settlement amount or the rising deformation amount of the pile top once every 30 min.
Therefore, the stability of each stage of load is improved by strictly controlling the load applying amount of each stage, and meanwhile, the time for measuring and reading the settlement of the pile top is strictly controlled, so that people can be helped to more accurately observe the influence of pressure or tension on the pile foundation to be measured.
And S4.4, after the compression resistance detection of the pile foundation reaches the maximum applied load value, the load in the step S4.3 is unloaded in a grading mode, the unloading value of each grade is twice of the loading value during unloading, the load is measured and read once every 15min after unloading, the load is read once every 30min after reading twice, then the load of one grade is unloaded, and the load is measured and read once every 3h after all the loads are unloaded.
S5: during actual work, after vertical resistance to compression detects the completion, carry out vertical resistance to plucking to the monomer pile foundation and detect, it includes following step: vertical tensile load is applied to the pile foundation that awaits measuring step by step through pile foundation resistance to plucking detection device earlier, all surveys the deformation of pulling up of the pile foundation that awaits measuring after every stage tensile load is accomplished after that, then unloads vertical pressure load step by step, surveys the deformation of pulling up of the pile foundation that awaits measuring step by step.
More specifically, the step of detecting the vertical uplift of the pile foundation in the invention is specifically as follows,
s5.1, in a rest period required by construction specification of the building engineering, after the pile foundation 3 to be detected is subjected to vertical compression resistance detection, leveling the pile top of the pile foundation to be detected again, so that the concrete quality and the section size of the pile top of the pile foundation 3 to be detected are equal to the design conditions (basically) of the pile body in the construction drawing;
in the step S5.1, the step S4.1 may be referred to as a method of leveling the pile top of the pile foundation to be tested, and the step S5.1 may be referred to as a method of leveling the pile top of the pile foundation to be tested, which is the same as the step S4.1.
S5.2, arranging a pile foundation anti-pulling detection device 6 which is provided with a jack 5 and is used for applying vertical pulling force to the pile foundation 3 to be detected on the pile foundation 3 to be detected, and applying vertical pulling force load to the foundation pile through the jack 5;
in operation, pile foundation resistance to plucking detection device 6 is including the pile foundation 3 that awaits measuring, brace table 21, second steel crossbeam 23 and percentage table 22, brace table 21 has two and symmetrical distribution in 3 both sides of pile foundation that awaits measuring, second steel crossbeam 23 is located 3 tops of pile foundation that awaits measuring, all install second jack 25 separately on two brace table 21, second steel crossbeam 23 both sides are connected respectively to the output of two second jacks 25, be connected with mechanical fixture or reinforcing bar 24 between 23 middle parts of second steel crossbeam and the pile foundation 3 that awaits measuring, percentage table 22 has a plurality ofly and installs in the pile body both sides of pile foundation 3 that awaits measuring.
The jack is used for applying tension to the first steel cross beam 14 so as to apply tension to the pile foundation to be detected, the dial indicator 22 is used for measuring the ascending deformation applied to the pile foundation 3 to be detected, and through the pile foundation uplift detection device 1, the anti-uplift detection device can be used for carrying out uplift detection on the pile foundation to be detected.
In actual operation, the support platform 21 of the invention can be a reaction pile or a natural foundation, and when the anti-pulling detection is carried out on the pile foundation 3 to be detected, the reaction pile or the natural foundation is used for providing reaction; the second steel beam 23 on the pile-foundation uplift detection device 6 can also be called a reaction beam, and in order to improve the detection accuracy, the gravity center of the reaction beam coincides with the central line of the pile foundation 3 to be detected, preferably, the support platform 21 adopts a reaction pile, and the gravity centers of the fulcrums at two sides of the reaction beam coincide with the central line of the reaction pile.
During actual operation, the second jack 25 is placed between the two ends of the reaction beam and the reaction pile or the natural foundation for applying a pulling force (i.e. for loading), and the upward pulling deformation of the pile foundation 3 to be tested is obtained by measuring the dial indicators 22 placed on the two sides of the pile body (concrete). According to the actual situation on site, the supporting platform 21 (such as a counterforce beam) is connected with the pile top of the pile foundation 3 to be tested in two modes of a mechanical clamp and a steel bar welding mode.
S5.3, when a tensile load is applied to the pile foundation 3 to be tested, loading is carried out by adopting a slow load maintaining method (namely step-by-step loading), the next stage of load is added after the load of each stage is relatively stable, and the rising deformation of the pile foundation to be tested is measured and read, wherein the interval time for measuring and reading the rising deformation of the pile foundation to be tested is the time after the loading of each stage is finished;
in step S5.3, if the settling volume or the rising deformation of the pile foundation 3 to be tested in 1 hour is not greater than 0.1mm twice, it is determined that the settling volume of the current-stage pile foundation 3 to be tested has reached relatively stable, and the next-stage load can be applied to the pile foundation 3 to be tested. Therefore, people can accurately judge whether the pile foundation 3 to be tested is in a stable state, and then help people judge whether a next-stage load needs to be applied.
And S5.4, when the termination detection condition of the vertical uplift detection is met, terminating the detection, unloading and reading and recording the resilience variable of the pile foundation 3 to be detected.
In actual work, when the compression resistance of the pile foundation to be detected is detected, the compression resistance or the uplift resistance of the pile foundation to be detected can be detected by adopting the existing compression resistance detection device or uplift resistance detection device, or by adopting the compression resistance detection device or uplift resistance detection device provided by the invention.
In order to reduce the influence of the vertical pressure load on the pile foundation to be measured, thereby improving the measurement accuracy of the vertical pressure load, when the vertical pressure load is applied, if one of the following three conditions occurs, the loading is terminated:
a. under the action of a certain level of load, the settlement of the pile foundation 3 to be detected is 5 times of that of the previous level of load, and the total settlement of the pile top exceeds 40 mm;
b. under the action of a certain level of load capacity, the settlement of the pile foundation 3 to be detected is 2 times larger than that of the previous level under the action of load, and the pile foundation is not relatively stable after 24 hours;
during actual work, the settlement of the pile foundation 3 to be measured reaches the relatively stable standard as follows: the settlement amount or the rising deformation amount of the pile foundation 3 to be measured in 1 hour is not more than 0.1mm continuously twice.
c. The design maximum applied load has been reached.
In actual operation, when compiling the inspection report, the inspector should pay attention to the normalization of the inspection report. In practice, the following problems should be mainly addressed:
a. original recording: including the original observation, calculation and data derivation, should be true and reliable, and the original record should not be the 'original' record of re-correcting. The original record is in a uniform recommended format as much as possible.
b. The use of the measurement unit shall adopt the legal measurement unit, and pay attention to several principles: firstly, the symbol principle is preferably adopted, secondly, the Chinese character name or the symbol of the metering unit must be taken as a whole and cannot be detached for use, and thirdly, the Chinese character name and the symbol of the metering unit cannot be mixed for use.
c. Data processing: the data processing method of the inspection result can be generally processed according to two standard requirements of 'representation method and judgment method of limit value' and 'rule of data modification', and attention is paid to the processing method of special data.
d. And (4) testing results and testing conclusions: when the measured value in the inspection result is quite close to the standard value but judged to be unqualified according to the comparison method of the full value or the comparison method of the trimming value, the measured value should be retested for several times according to the same condition for the sake of caution, and the average value is taken; or other detection methods are used for checking the reproducibility degree of the compound.
In actual work, the method adopts a low-energy transient excitation mode at the pile top, measures the time-course curve of the acceleration response of the pile top, and judges the integrity of the pile body through fluctuation theoretical analysis and frequency domain auxiliary analysis. Meanwhile, the method can also judge whether the pile body has the defects of pile breakage, cracks and the like, and is used for detecting the average wave velocity of the concrete of the pile body.
In actual work, the pile foundation to be tested of the invention is in accordance with the following regulations: 1. the material, strength and section size of the pile head are basically equal to those of the pile body; 2. the pile top surface should be flat, dense and substantially perpendicular to the pile axis.
In actual work, the test parameter setting of the invention when testing the pile foundation to be tested meets the following regulations: 1. the time period length of time domain signal recording is not less than 5ms after 2L/c; the upper limit of the frequency range of amplitude-frequency signal analysis should not be less than 2000 Hz; 2. setting the pile length as the construction pile length from the pile top measuring point to the pile bottom, and setting the pile body sectional area as the construction sectional area; 3. the wave speed of the pile body can be preliminarily set according to the test values of the local piles of the same type; 4. the sampling time interval or the sampling frequency is reasonably selected according to the pile length, the pile body wave speed and the frequency domain resolution; the number of sampling points of the time domain signal is not less than 1024 points; 5. the set value of the sensor is set according to the metrological verification result.
During actual work, the installation and vibration excitation operation of the measuring sensor meet the following regulations:
1. the sensor is installed to be vertical to the top surface of the pile; when bonded with a coupling agent, the adhesive should have sufficient bonding strength.
2. The position of an excitation point of the solid pile is selected to be at the center of the pile, and the installation position of the measuring sensor is preferably at the radius position 2/3 away from the center of the pile; the excitation point of the hollow pile and the installation position of the measuring sensor are preferably on the same horizontal plane, the included angle formed by the connection line of the excitation point and the measuring sensor and the center of the pile is preferably 90 degrees, and the excitation point and the installation position of the measuring sensor are preferably 1/2 degrees of the thickness of the pile.
3. The vibration excitation point and the installation position of the measuring sensor are required to avoid the influence of the main reinforcement of the reinforcement cage.
4. The excitation direction should be along the pile axis direction.
5. Transient excitation should pass the field and strike the test, choose excitation force hammer and hammer blanket of suitable weight, preferably use the wide pulse to obtain the pile bottom or pile shaft inferior part defect reflected signal, preferably use the narrow pulse to obtain the pile shaft upper portion defect reflected signal.
6. The steady-state excitation should obtain a stable response signal under each set frequency, and the magnitude of the excitation force should be adjusted according to the pile diameter, the pile length and the constraint condition of the soil around the pile.
During actual work, the following regulations are met when the test sensor is used for signal acquisition and screening:
1. according to the size of the pile diameter, 2-4 detection points are symmetrically arranged at the pile center; the number of valid signals recorded per detection point is preferably not less than 3.
2. And checking and judging whether the actually measured signals reflect the integrity characteristics of the pile body.
3. The consistency of different detection points and time domain signals measured for multiple times is poor, the reason should be analyzed, and the number of the detection points is increased.
4. The signal should not be distorted and produce a null shift, and the signal amplitude should not exceed the range of the measurement system.
The embodiments of the present invention are preferred embodiments of the present invention, and the scope of the present invention is not limited by these embodiments, so: all equivalent changes made according to the structure, shape and principle of the invention are covered by the protection scope of the invention.
Claims (10)
1. A concrete pile foundation detection method comprises a pile foundation to be detected which is composed of a pile top and a pile body, and is characterized by comprising the following steps,
s1: carrying out leveling treatment on the pile top of the pile foundation to be detected, enabling the concrete quality and the section size of the pile top of the pile foundation (3) to be detected to be equal to the design conditions of a pile body in a construction drawing, and enabling the center line of the pile foundation to be detected to be perpendicular to the top surface of the pile top;
s2: installing a plurality of measuring sensors for measuring the pile foundation to be measured on the pile top of the pile foundation to be measured, enabling a plane formed by the plurality of measuring sensors to be vertical to the top surface of the pile foundation to be measured, actually measuring a time-course curve of acceleration response of the pile top in a low-energy transient excitation mode, ensuring that stable excitation can obtain stable response signals under each set frequency, and adjusting the excitation force of the stable excitation according to the pile diameter, the pile length and the soil constraint condition around the pile;
s3: detecting the average wave velocity of the pile body, detecting the integrity of the pile body by a wave theory analysis method and a frequency domain analysis method, and judging whether the pile body has the defects of pile breakage and crack;
s4: after the step S2 and the step S3 are completed, the vertical compression resistance of the pile foundation to be tested is detected,
firstly, applying vertical pressure load to a pile foundation to be detected step by step through a pile foundation compression resistance detection device, and then measuring and reading the settlement of the pile foundation to be detected after each step of pressure load is completed; then, unloading the vertical pressure load step by step, and measuring and reading the settlement of the pile foundation to be detected step by step;
s5: after the vertical compression resistance detection is finished, the single pile foundation is subjected to vertical anti-pulling detection,
vertical tensile load is applied to the pile foundation that awaits measuring step by step through pile foundation resistance to plucking detection device earlier, all surveys the deformation of pulling up of the pile foundation that awaits measuring after every stage tensile load is accomplished after that, then unloads vertical pressure load step by step, surveys the deformation of pulling up of the pile foundation that awaits measuring step by step.
2. The method for detecting the concrete pile foundation of claim 1, wherein in the step S4, the step of detecting the vertical compression resistance of the pile foundation to be detected specifically comprises the following steps,
s4.1, leveling the pile top of the pile foundation to be detected after the pile foundation (3) to be detected reaches the rest period required by the construction specification of the building engineering and the pile foundation is subjected to low-strain detection, so that the concrete quality and the section size of the pile top of the pile foundation (3) to be detected are equal to the design conditions of the pile body in the construction drawing;
s4.2, arranging a pile foundation compression resistance detection device (1) which is provided with a jack (5) and is used for applying vertical load to the pile foundation (3) to be detected on the pile foundation (3) to be detected, and applying vertical pressure load to the pile foundation to be lateral-group through the jack (5);
s4.3, when pressure load is applied to the pile foundation (3) to be tested, loading the pile foundation (3) to be tested by adopting a slow-speed load maintaining method, adding the next stage of load after each stage of load is relatively stable, and measuring and reading the settlement of the pile foundation to be tested, wherein the interval time for measuring and reading the settlement of the pile foundation to be tested is the time after each stage of loading is finished;
and S4.4, after the compression resistance detection of the pile foundation reaches the maximum applied load value, the load in the step S4.3 is unloaded in a grading mode, the unloading value of each grade is twice of the loading value during unloading, the load is measured and read once every 15min after unloading, the load is read once every 30min after reading twice, then the load of one grade is unloaded, and the load is measured and read once every 3h after all the loads are unloaded.
3. The concrete pile foundation detection method according to claim 2, wherein, in step S4.2, the pile foundation compression resistance detection device (1) comprises a pile foundation (3) to be detected, a sleeper pile (11), a first steel beam (14), a first jack (15) and an oil pressure gauge (12), and a balancing weight (13) made of precast concrete, sleeper piles (11) are symmetrically arranged on two sides of the pile foundation (3) to be tested, a first steel cross beam (14) is erected between the tops of the two sleeper piles (11), a first jack (15) is positioned between the top of the pile foundation and the middle part of the first steel cross beam (14), a plurality of balancing weights (13) are erected on the upper end of the steel cross beam (4), the balancing weights (13) are used for applying reverse force to the first steel cross beam (14), an oil pressure gauge (12) is arranged on the pile foundation (3) to be tested, the pressure measuring device is used for measuring the pressure applied by the first jack (15) to the pile foundation (3) to be measured.
4. The method for testing a concrete pile foundation according to claim 3, wherein in step S5, the step of testing the vertical uplift resistance of the pile foundation to be tested specifically comprises the following steps,
s5.1, in a rest period required by construction specification of the building engineering, after the pile foundation (3) to be detected is subjected to vertical compression resistance detection, flattening the pile top of the pile foundation to be detected again, so that the concrete quality and the section size of the pile top of the pile foundation (3) to be detected are equal to the design conditions of the pile body in the construction drawing;
s5.2, arranging a pile foundation anti-pulling detection device (6) which is provided with a jack (5) and is used for applying vertical pulling force to the pile foundation (3) to be detected on the pile foundation (3) to be detected, and applying vertical pulling force load to the foundation pile through the jack (5);
s5.3, when a tensile load is applied to the pile foundation (3) to be tested, loading by adopting a slow load maintaining method, adding the next stage of load after each stage of load is relatively stable, and measuring and reading the rising deformation of the pile foundation to be tested, wherein the interval time for measuring and reading the rising deformation of the pile foundation to be tested is the time after each stage of loading is finished;
and S5.4, when the termination detection condition of the vertical uplift detection is met, terminating the detection, unloading and reading and recording the resilience variable of the pile foundation (3) to be detected.
5. The concrete pile foundation detection method according to claim 4, wherein in step S5.2, the pile foundation uplift detection device (2) comprises a pile foundation (3) to be detected, support tables (21), second steel beams (23) and a dial indicator (22), the two support tables (21) are symmetrically distributed on two sides of the pile foundation (3) to be detected, the second steel beams (23) are located above the pile foundation (3) to be detected, the two support tables (21) are respectively provided with second jacks (25), the output ends of the two second jacks (25) are respectively connected with two sides of the second steel beams (23), a mechanical clamp or a steel bar (24) is connected between the middle part of the second steel beams (23) and the pile foundation (3) to be detected, and the dial indicator (22) is provided with a plurality of jacks and is arranged on two sides of a pile body of the pile foundation (3) to be detected.
6. The concrete pile foundation detection method according to any one of claims 1 to 5, wherein in step S2, when the pile foundation to be detected is a solid pile, the position of the excitation point of the pile foundation to be detected is located at the center of the pile foundation to be detected, and the installation position of the measuring sensor is located at a radius of 2/3 from the center of the pile; when the pile foundation to be detected is a hollow pile, the excitation point of the pile foundation to be detected and the installation position of the measuring sensor are on the same horizontal plane, the included angle formed by the horizontal plane and the central connecting line of the pile is 90 degrees, and the excitation point and the installation position of the measuring sensor are 1/2 parts of the thickness of the pile wall.
7. The method for detecting the concrete pile foundation of claim 6, wherein in step S2, the time period recorded by the time domain signal of the time course curve should last for not less than 5min after 2L/c; the upper limit of the frequency range of amplitude-frequency signal analysis should not be less than 2000 Hz.
8. The concrete pile foundation detection method of claim 7, wherein in step S4.3 and step S5.3, the load capacity applied to each stage is 1/8 of the design limit bearing capacity, the first stage addition is 1/4 of the characteristic value of the bearing capacity, after the load of each stage is relatively stable, the next stage of load can not be applied until the pile foundation compression resistance detection reaches the maximum applied load value, and the loading is stopped; after each stage of applied pressure load is finished, measuring and reading the settlement amount or the rising deformation amount of the pile top at 5min, 15min, 30min, 45min and 60min in sequence, and then measuring and reading the settlement amount or the rising deformation amount of the pile top once every 30 min.
9. The method for detecting the concrete pile foundation according to the claim 8, characterized in that in the step S4.2, the load capacity of the vertical pressure load is converted by a calibration curve of the jack (5), and is measured and read by an oil pressure gauge (12), and a load-oil pressure value corresponding table is established on site.
10. The method for detecting the concrete pile foundation in the claim 9, wherein when the vertical tensile load is applied, the loading is stopped if one of the following four conditions occurs:
a. under the action of a certain level of load, the upward pulling amount of the pile top is 5 times larger than that under the action of the previous level of upward pulling load;
b. controlling the pulling amount of the pile top according to the pulling amount of the pile top, and when the accumulated pulling amount of the pile top exceeds 100 mm;
c. controlling according to the tensile strength of the steel bar, wherein the pulling load on the pile top reaches 0.9 time of the standard value of the strength of the steel bar;
d. and for the pile foundation to be tested which is subjected to acceptance sampling detection, the maximum upper pulling load value of the design requirement is reached.
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