CN109487835A - The detection method and detection device of pile foundation allowable bearing - Google Patents
The detection method and detection device of pile foundation allowable bearing Download PDFInfo
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- CN109487835A CN109487835A CN201811156091.2A CN201811156091A CN109487835A CN 109487835 A CN109487835 A CN 109487835A CN 201811156091 A CN201811156091 A CN 201811156091A CN 109487835 A CN109487835 A CN 109487835A
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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
- E02D2600/00—Miscellaneous
- E02D2600/10—Miscellaneous comprising sensor means
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Abstract
Disclose the detection method and detection device and detection system of a kind of pile foundation allowable bearing based on freely falling body exciting low strain dynamic, detection method includes the following steps: that power is rammed at the top of freely falling body exciting pile foundation to generate vibration response signal, the bottom that power is rammed is equipped with elastic buffer unit, the power is rammed via pile foundation described in the elastic buffer unit exciting, and the vibration velocity signal includes low-frequency vibration response signal；First acquisition unit measuring force rams the impact force signal that exciting generates, and the second acquisition unit measures the vibration response signal that pile foundation generates；Time base variable samples the impact force signal and vibration response signal and intercepts impact force signal and the vibration response signal of predetermined period to obtain the low-frequency vibration response signal based on impact force signal, it impacts force signal and low-frequency vibration response signal and generates the dynamic stiffness curve based on vibration frequency via transmission function, the dynamic stiffness value for being zero based on vibration frequency in dynamic stiffness curve determines pile foundation allowable bearing.
Description
Technical field
The present invention relates to technical field of nondestructive testing, especially a kind of pile foundation based on freely falling body exciting low strain dynamic is held
Perhaps the detection method and detection device of bearing capacity.
Background technique
If pile foundation encounters loads change, earthquake, water damage etc. during operation, the basic later period is used safe
Assessment, needs to detect foundation bearing capacity again.Currently, the method that can do loading test, there is static load method and dynamic load method, this
Both of which has shortcoming, if static load method is the method that engineering circles are most trusted, takes a lot of work, is expensive.The analysis method of dynamic load method
More complex, accuracy is not also high, cannot accomplish to generally investigate to existing foundation pile and pile foundation, basically can not make to existing building basis
With believable bearing capacity can not be provided to the pile foundation for having runed many years by both the above method.
According to the mutual misalignment between the size, pile body stress level and stake soil of stake top exciting force, generally foundation pile is moved
Support method is divided into high strain dynamic test method and low-strain dynamic measure method.High strain dynamic test method: high strain dynamic test method is generally selected
Select hammer it is great foundation pile is impacted in 1.0%~1.5% weight for estimating ultimate bearing capacity of single pile, pile body generate dependent variable
Grade is in 10-3Left and right obtains participating in the quiet of soil of stake soil vibration, dynamic resistance and the defect shape of stake by the solution to wave equation
Condition, to carry out quantitative assessment to pile bearing capacity and pile body integrity, the shortcomings that this method is that basis will generate several mm
Permanent displacement, and check and evaluation can not be carried out on existing structure.Low-strain dynamic measure method: pile detection with low strain method
Pile strain magnitude is generally 10-5Within, mainly there are reflective wave method, dynamic parameter method, mechanical impedance method, hydroelectric effect method etc.,
The equipment that low-strain dynamic measure assessment bearing capacity is not waited using several kilograms to more than ten kilograms mainly impacts single pile, most favourable opposition
Hit power substantially at 2~3 tons or so, and on frequency band distribution from the point of view of high band power energy comparison it is small, in the past for using
Small strain method carries out bearing capacity evaluation to denounce most being exactly its low-frequency range minimum energy, and lesser impact force is likely to result in
The nonlinearity erron of test result, so that the using effect to method impacts.Therefore, in terms of bearing capacity evaluation, application
Effect of the various methods such as low-strain dynamic measure method all without having obtained.
Disclosed above- mentioned information are used only for enhancing the understanding to background of the present invention in the background section, it is thus possible to
Information comprising not constituting the prior art known to a person of ordinary skill in the art in home.
Summary of the invention
Problems to be solved by the invention
As described above, its low low-frequency range minimum energy of existing low strain dynamic method, nonlinearity erron is big and bring therewith
Interference is more in structural dynamic response, is unable to get accurate Carrying Capacity, and present invention needs provide a kind of based on freely falling body
The detection method and detection device of the pile foundation allowable bearing of exciting low strain dynamic, can significantly improve low-frequency range energy, keep away
Exempting from screw thread slippage under long-term surge acts on causes measured result error larger, significantly improves acquisition data SNR, passes through
Data processing of the invention is crossed, detection accuracy can be largely increased and present invention detection is rapid, can be used for generally investigating pile foundation
Plinth bearing capacity can not accomplish that this point, the present invention can be also used for existing build in the prior art due to the cost of detection and time
The loading test of pile foundation under building.
Solution to problem
The inventors of the present invention have made intensive studies in order to achieve the above objectives, specifically, the present invention provides a kind of base
In the detection method of the pile foundation allowable bearing of freely falling body exciting low strain dynamic comprising following step:
Power is rammed at the top of freely falling body exciting pile foundation to generate vibration response signal, wherein the bottom that the power is rammed is equipped with
Elastic buffer unit, the power are rammed via pile foundation described in the elastic buffer unit exciting, and the vibration velocity signal includes
Low-frequency vibration response signal；
First acquisition unit measuring force rams the impact force signal that exciting generates, and the second acquisition unit measures what pile foundation generated
Vibration response signal；
Time base variable sample it is described impact force signal and vibration response signal and intercept predetermined period impact force signal and
Vibration response signal with obtain based on impact force signal low-frequency vibration response signal,
It impacts force signal and low-frequency vibration response signal and generates the dynamic stiffness curve based on vibration frequency via transmission function,
The dynamic stiffness value for being zero based on vibration frequency in dynamic stiffness curve determines the pile foundation allowable bearing.
In the detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic, vibratory response is surveyed
Amount unit be piezoelectric velocity sensor, low-frequency vibration response signal be low-frequency vibration speed responsive signal, impact force signal and
Low-frequency vibration speed responsive signal generates the dynamic stiffness curve based on vibration frequency, the dynamic stiffness via transmission functionWherein, F (f) is the impact force signal based on frequency, and v (f) is the low-frequency vibration speed responsive based on frequency
Signal determines the pile foundation allowable bearing based on the dynamic stiffness value of vibration frequency in dynamic stiffness curve etc. 0.
In the detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic, it is based on impact force
Signal and low-frequency vibration speed responsive signal generate the auto-power spectrum S of impact forceFF(f) and the interaction of impact force and vibration velocity
Rate composes SFV(f), coherent function γ2(f) it isWork as γ2(f) 0.5 < determines the impact force signal and low frequency vibration
Dynamic speed responsive signal is noise.
It is described freely to fall in the detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic
The height of body is 1.5-2m, and the quality that power is rammed is 50~600kg, and in one embodiment, exciting obtains maximum impact force and is
20000-50000 kilogram, the frequency acquisition that time base variable samples the impact force signal is 1k-2k, and time base variable multiple is 2-8
Times.
In the detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic, the dynamic stiffness
Being extended to the dynamic stiffness value of the longitudinal axis close to the gentle section of dynamic stiffness curve that vibration frequency is 0 on curve is Static stiffness value, described quiet
Rigidity value is based on tolerable settlement and obtains the pile foundation allowable bearing.
In the detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic, dynamic stiffness curve
Gentle section is in 5~20Hz frequency range, described via the dynamic stiffness of linear regression acquisition 0Hz to be determined as Static stiffness value
Pile foundation allowable bearing is the Static stiffness value multiplied by the tolerable settlement, and tolerable settlement is 4 millimeters.
In the detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic, power rammer is freely fallen
Center or pier side center, the second acquisition unit at the top of body exciting pile foundation are arranged in the centre bit at the top of pile foundation
It sets to measure vibration response signal, power is rammed at the top of multiple falling bodies exciting pile foundation to generate multiple vibration response signal to be added
Power impact force signal and weighting low-frequency vibration response signal, it is logical based on weighting impact force signal and weighting low-frequency vibration response signal
It crosses transmission function and generates the weighting dynamic stiffness curve based on vibration frequency.
In the detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic, the pile foundation
Single-pile foundation or used multi-column pier foundation including exposed pile crown, the multi-column pier foundation are located under existing building via cushion cap,
Power is rammed to generate vibration response signal at the top of freely falling body exciting cushion cap, and the power is rammed via elastic buffer unit exciting institute
Cushion cap is stated, the second acquisition unit is arranged at the top of cushion cap to measure vibration response signal.
According to another aspect of the present invention, the pile foundation based on freely falling body exciting low strain dynamic described in a kind of implementation allows to hold
The detection device for carrying the detection method of power includes at the exciting unit, data acquisition unit and data of freely falling body exciting pile foundation
Manage unit, wherein
Exciting unit includes,
Permanent magnet unit, being configured to lead to based on control signal magnetic or disconnected magnetic is adsorbed capable rammer or freely falling body,
Power is rammed, and is configured at the top of freely falling body exciting pile foundation to generate vibration response signal, the bottom that the power is rammed
Equipped with elastic buffer unit, the power is rammed via pile foundation described in the elastic buffer unit exciting,
Data acquisition unit includes,
First acquisition unit, the first acquisition unit for being configured to the impact force signal that acquisition power rams exciting are arranged in power and ram top
Portion,
Second acquisition unit, the second acquisition unit for being configured to acquisition vibration response signal are arranged at the top of pile foundation；
Data processing unit includes,
Time base variable sampling unit is configured to acquire the impact force signal and vibration response signal based on time base variable,
Interception unit is configured to be based on punching based on predetermined period interception impact force signal and vibration response signal to obtain
The low-frequency vibration response signal of force signal is hit,
Processing unit is configured to be based on based on impact force signal and low-frequency vibration response signal via transmission function generation
The dynamic stiffness curve of vibration frequency, the processing unit determine that the pile foundation is allowed based on the dynamic stiffness value that vibration frequency is zero
Bearing capacity.
In the detection device, exciting unit further includes,
Detachable bracket is configured to bearing exciting unit and makes exciting unit vertical alignment pile foundation, the card disassembly
Bracket includes the pilot unit that alignment pile foundation is rammed for directed force,
Motor, the motor for being configured to provide the power for promoting exciting unit are arranged on detachable bracket,
Leveling unit, is used to level detachable bracket, and the permanent magnet unit connects motor with fixed pulley by wirerope；
The elastic buffer unit includes Rubber end,
First acquisition unit is acceleration transducer,
Second acquisition unit be velocity sensor or piezoelectric acceleration transducer,
The processing unit includes the switch unit for issuing the control signal of logical magnetic or disconnected magnetic, and processing unit includes number letter
Number processor, application-specific integrated circuit ASIC or on-site programmable gate array FPGA, processing unit includes memory, the memory
It may include that one or more read only memory ROMs, random access memory ram, flash memory or Electrical Erasable can be compiled
Journey read-only memory EEPROM.
Beneficial effects of the present invention
The present invention is rammed at the top of freely falling body exciting pile foundation by power to generate vibration response signal, the bottom that the power is rammed
Equipped with elastic buffer unit, the power is rammed via pile foundation described in the elastic buffer unit exciting, significantly improves low frequency vibration
Sound of something astir induction signal samples the impact force signal and vibration response signal and the impact force for intercepting predetermined period by time base variable
Signal and vibration response signal obtain excellent dynamic of signal-to-noise ratio to obtain the low-frequency vibration response signal based on impact force signal
Stiffness curve significantly reduces dynamic stiffness value error, and it is raw via transmission function to impact force signal and low-frequency vibration response signal
At the dynamic stiffness curve based on vibration frequency, the dynamic stiffness value for being zero based on vibration frequency in dynamic stiffness curve determines the pile foundation
Plinth allowable bearing.This method is closed by the equivalent of low-frequency range loading frequency and the substantially linear slight change of foundation pile dynamic stiffness
System, and dynamic stiffness in low frequency band frequency closer to 0 value dynamic stiffness closer to Static stiffness, dynamic stiffness value that vibration frequency is zero determines
For Static stiffness, dynamic load method in the prior art needs to obtain the quiet of the same area by carrying out quiet dynamic comparison on the same area
Dynamic coefficient of correlation estimates Analysis on Static Stiffness bearing capacity based on static to dynamic ratio, and the present invention does not need to do static test to obtain
Static to dynamic ratio and detection accuracy and reliability can be significantly improved, the present invention significantly shortens detection time, can be to stake
Basis is generally investigated, this is also that existing detection method cannot achieve, and the present invention itself is moved by utilizing to each pile foundation
Stiffness characteristics generate Static stiffness, can more accurately reflect the bearing capacity of pile foundation, can be also used for the pile foundation under existing building
The loading test of plinth, use scope is extensive, eliminates the expense of static test, substantially increases the detection of Pile Bearing Capacity
Range and detection accuracy significantly improve the safety of structure operation.
The above description is only an overview of the technical scheme of the present invention, in order to make technological means of the invention clearer
Understand, reach the degree that those skilled in the art can be implemented in accordance with the contents of the specification, and in order to allow the present invention
Above and other objects, features and advantages can be more clearly understood, illustrated below with a specific embodiment of the invention
Explanation.
Detailed description of the invention
Fig. 1 shows the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of one embodiment of the invention
The step schematic diagram of detection method.
Fig. 2 shows the pile foundation allowable bearings based on freely falling body exciting low strain dynamic of one embodiment of the invention
The impact force signal schematic representation of detection method.
Fig. 3 shows the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of one embodiment of the invention
The impact force of detection method composes schematic diagram.
Fig. 4 shows the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of one embodiment of the invention
The impact force signal schematic representation of the time base variable sampling of detection method.
Fig. 5 shows the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of one embodiment of the invention
The time base variable of detection method samples vibration response signal schematic diagram.
Fig. 6 shows the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of another embodiment of the invention
Detection method based on predetermined period intercept signal schematic diagram.
Fig. 7 shows the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of another embodiment of the invention
Detection method non-intercepting process dynamic stiffness curve schematic diagram.
Fig. 8 shows the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of another embodiment of the invention
Detection method intercepting process dynamic stiffness curve schematic diagram.
The implementation that Fig. 9 shows another embodiment of the invention allows to hold based on the pile foundation of freely falling body exciting low strain dynamic
Carry the structural schematic diagram of the detection device of the detection method of power.
The implementation that Figure 10 shows another embodiment of the invention is allowed based on the pile foundation of freely falling body exciting low strain dynamic
The structural schematic diagram of the detection device of the detection method of bearing capacity.
Specific embodiment
The specific embodiment that the present invention will be described in more detail below with reference to accompanying drawings.Although being shown in attached drawing of the invention
Specific embodiment, it being understood, however, that may be realized in various forms the present invention without that should be limited by embodiments set forth here
System.It is to be able to thoroughly understand the present invention on the contrary, providing these embodiments, and can be complete by the scope of the present invention
Be communicated to those skilled in the art.
It should be noted that having used some vocabulary in the specification and claims to censure specific components.Ability
Field technique personnel it would be appreciated that, technical staff may call the same component with different nouns.This specification and right
It is required that not in such a way that the difference of noun is as component is distinguished, but with the difference of component functionally as differentiation
Criterion."comprising" or " comprising " as mentioned throughout the specification and claims are an open language, therefore should be solved
It is interpreted into " including but not limited to ".Specification subsequent descriptions are to implement better embodiment of the invention, so the description be with
For the purpose of the rule of specification, the range that is not intended to limit the invention.Protection scope of the present invention is when the appended right of view
It is required that subject to institute's defender.
In order to facilitate understanding of embodiments of the present invention, it is done by taking several specific embodiments as an example below in conjunction with attached drawing further
Explanation, and each attached drawing does not constitute the restriction to the embodiment of the present invention.
Specifically, the detection method of the pile foundation allowable bearing as shown in Figure 1 based on freely falling body exciting low strain dynamic
Step schematic diagram, a kind of detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic includes following steps
It is rapid:
Power is rammed at the top of freely falling body exciting pile foundation to generate vibration response signal, wherein the bottom that the power is rammed is equipped with
Elastic buffer unit, the power are rammed via pile foundation described in the elastic buffer unit exciting, and the vibration velocity signal includes
Low-frequency vibration response signal；
First acquisition unit measuring force rams the impact force signal that exciting generates, and the second acquisition unit measures what pile foundation generated
Vibration response signal；
Fig. 2 shows the pile foundation allowable bearings based on freely falling body exciting low strain dynamic of one embodiment of the invention
The impact force signal schematic representation of detection method.Fig. 3 show one embodiment of the invention based on freely falling body exciting low strain dynamic
Pile foundation allowable bearing detection method impact force compose schematic diagram, the present invention utilize power ram freely falling body impact force
Realize the impact to structure, in order to improve the distribution of low-frequency range energy, when design rams bottom in power and uses such as high-performance rubber
The elastic buffer unit of the Rubber end of production, substantially increases low-frequency range energy；In one embodiment, in order to avoid previous power
Hammer pressure sensor is arranged in bottom, long-term surge acts on the larger problem of lower screw thread slippage measured result error, and first
Acquisition unit is placed in the top of power rammer, and the conversion of power is carried out using the calibration result of acceleration and impact force.It was verified that should
Design scheme greatly changes low strain dynamic method testing effect, and as Figure 2-3, the present invention changes total impact force water
It is flat, maximum impact force has been increased to 20 tonnes not, has been 8~10 times of the prior art；Second, energy is obviously mainly distributed on low
Frequency range, the following impact force 600kg-700kg power of low-frequency range 10Hz are 15 times or more of prior art low-strain measurement method, with
This method matches in the feature that low-frequency range is applicable in；Third, long-time service are not in that previous impact force scaling results obviously become
Change.
Time base variable sample it is described impact force signal and vibration response signal and intercept predetermined period impact force signal and
Vibration response signal is to obtain the low-frequency vibration response signal based on impact force signal.Impact force signal and low-frequency vibration response letter
Number via transmission function generate the dynamic stiffness curve based on vibration frequency, based on vibration frequency in dynamic stiffness curve etc. 0 it is dynamic just
Angle value determines the pile foundation allowable bearing.
In one embodiment, 1k~2k is set by the frequency acquisition of force signal, time base variable multiple is set as 2~8 times.
Fig. 4 shows the detection side of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of one embodiment of the invention
Method time base variable sampling impact force signal schematic representation, Fig. 5 show one embodiment of the invention based on freely falling body exciting
The time base variable of the detection method of the pile foundation allowable bearing of low strain dynamic samples vibration response signal schematic diagram, referring to fig. 4 with 5.
The present invention obtains the dynamic stiffness on basis to input/output signal, using transfer function analysis method.Transmission function (transfer
Function) refer to that the response of zero initial condition lower linear system (exports) Laplace transform (or z-transform) and excitation of amount
The ratio between the Laplace transform of (inputting) amount.Be denoted as G (s)=Y (s)/U (s), wherein Y (s), U (s) be respectively output quantity and
The Laplace transform of input quantity.Transmission function is one of the basic mathematical tool for describing linear system dynamic characteristic, classics control
The theoretical main approaches --- frequency response method and root-locus technique --- of system are all built upon on the basis of transmission function.
Mechanical impedance method is also to apply transmission function to the test of basic dynamic stiffness.The single pile of the low strain dynamic of the prior art, which detects, to be utilized
Full-time domain test result carries out transfer function analysis, since acquisition time is short, impact force is small, signal energy is small, outside noise is big
Etc. factors influence, the dynamic stiffness curve signal-to-noise ratio actually obtained is very poor, and especially in low-frequency range, this results in dynamic stiffness value mistake
Difference is very big, this is also another main cause that previous dynamic stiffness detection bearing capacity is not widely popularized.In order to change this
One problem, the present invention by interception predetermined period impact force signal and vibration response signal, Fig. 6 show the present invention another
The detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of embodiment is intercepted based on predetermined period
Signal schematic representation improves precision of analysis as shown, signal-to-noise ratio greatly improved in intercepting process.Fig. 7 is shown
The detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic of another embodiment of the invention is not cut
Take the dynamic stiffness curve schematic diagram of processing.Fig. 8 show another of the invention embodiment based on freely falling body exciting low strain dynamic
Pile foundation allowable bearing detection method intercepting process dynamic stiffness curve schematic diagram.Pass through comparison, present invention interception
Dynamic stiffness curve that treated has obtained apparent optimization.
The present invention can significantly improve the low-frequency vibration signal of acquisition, analyze and cut by time base variable sampling, Frequence zooming
Analysis is taken to significantly improve the precision of dynamic stiffness curve, this method carries out shock-testing to structure in terms of pile measurement, passes through
The response relation of analysis input and output, to analyze the stiffness by itself feature of structure, the present invention passes through freely falling body exciting pile foundation
Plinth surveys the vibratory response of its generation, vibration analysis is based on, according to formulaIf f=0, dynamic stiffness value Kd
It is exactly Static stiffness Ks.But in actual measurement, when frequency is 0, vibratory response has actually stopped, so cannot be directly based upon dynamic rigid
The frequency of line of writing music is corresponding 0 dynamic stiffness of 0 value as allowing static force, and is needed based in low-frequency range loading frequency and foundation pile
The relation of equal quantity of the substantially linear slight change of dynamic stiffness, and dynamic stiffness is closer in low-frequency range (being far below the natural frequency of vibration) frequency
0 value dynamic stiffness is closer to Static stiffness.The Static stiffness for calculating 0Hz obtains basis multiplied by tolerable settlement further according to Static stiffness value
Bearing capacity.The present invention solves low accuracy existing for Pile Bearing Capacity context of detection, expensive, laborious, analysis complexity, to new
Stake cannot generally investigate bearing capacity, and the problem of bearing capacity can not be assessed to built pile foundation, reliable measurements are provided for engineering circles
The method of pile foundation allowable bearing.
In a preferred embodiment, it according to 5Hz~20Hz dynamic stiffness data, chooses multiple spot frequency and dynamic stiffness carries out line
Property in push away, selected points are no less than 5 points, obtain linear regression formula using these numerical characteristics put, public according to returning
The dynamic stiffness value of formula reckoning 0Hz.When frequency is equal to 0, dynamic response is stripped, therefore, the frequency obtained from dynamic stiffness curve is
Dynamic stiffness value when zero is Static stiffness.
In a preferred embodiment, Ks=Km-(Kn-Km) * m/ (n-m), wherein KsDynamic stiffness when as f=0, also referred to as
For Static stiffness, KmIndicate dynamic stiffness when frequency is f=m, KnIndicate dynamic stiffness when frequency is f=n, n, m respectively represent reality
Measured frequency, unit Hz, between 5~20, and n > m, usual m take 5.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, vibratory response measuring unit is piezoelectric velocity sensor, and low-frequency vibration response signal is low-frequency vibration speed
Response signal impacts force signal and low-frequency vibration speed responsive signal via transmission function and generates the dynamic stiffness based on vibration frequency
Curve, the dynamic stiffnessWherein, F (f) is the impact force signal based on frequency, and v (f) is based on frequency
Low-frequency vibration speed responsive signal determines that the pile foundation is allowed based on the dynamic stiffness value of vibration frequency in dynamic stiffness curve etc. 0
Bearing capacity.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, the auto-power spectrum S of impact force is generated based on impact force signal and low-frequency vibration speed responsive signalFF(f) and
The interaction rate of impact force and vibration velocity composes SFV(f), coherent function γ2(f) it isWork as γ2(f) 0.5 <, really
The fixed impact force signal and low-frequency vibration speed responsive signal are noise.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, the height of the freely falling body is 1.5-2m, and the quality that power is rammed is that 50~600kg exciting obtains maximum impact force
For 20000-50000 kilogram, the frequency acquisition that time base variable samples the impact force signal is 1k-2k, and time base variable multiple is 2-
8 times.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, the resolution ratio of the frequency of the abscissa of dynamic stiffness curve is less than 1 hertz, in one embodiment, abscissa
Coordinate is as unit of 0.5 hertz of interval.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, the vibration response signal includes vibration acceleration signal.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, the vibration response signal includes vibration displacement signal.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, the dynamic rigid of the longitudinal axis is extended to close to the gentle section of dynamic stiffness curve that vibration frequency is 0 in the dynamic stiffness curve
Angle value is Static stiffness value, and the Static stiffness value is based on tolerable settlement and obtains the pile foundation allowable bearing, dynamic stiffness curve
Gentle section is lower than the pile foundation natural frequency of vibration.The pile foundation natural frequency of vibration is the important indicator of the degree of safety of structure, can be to avoid altogether
Vibration.Therefore, method of the invention significantly improves the safety of pile foundation structure.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, the gentle section of dynamic stiffness curve is in 5~20Hz frequency range, and the dynamic stiffness of 0Hz is obtained via linear regression
To be determined as Static stiffness value, the pile foundation allowable bearing is the Static stiffness value multiplied by the tolerable settlement, allows to sink
Drop amount is 4 millimeters.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, power rams the center or pier side center at the top of freely falling body exciting pile foundation, the second acquisition unit cloth
The center at the top of pile foundation is set to measure vibration response signal, power is rammed more to generate at the top of multiple falling bodies exciting pile foundation
Secondary vibration response signal with obtain weighting impact force signal and weighting low-frequency vibration response signal, based on weighting impact force signal and
It weights low-frequency vibration response signal and the weighting dynamic stiffness curve based on vibration frequency is generated by transmission function.
The detection method of pile foundation allowable bearing of the present invention based on freely falling body exciting low strain dynamic it is preferred
In embodiment, the pile foundation includes the single-pile foundation or used multi-column pier foundation of exposed pile crown, the multi-column pier foundation warp
Be located under existing building by cushion cap, power is rammed to generate vibration response signal at the top of freely falling body exciting cushion cap, the power ram via
Cushion cap described in the elastic buffer unit exciting, the second acquisition unit are arranged at the top of cushion cap to measure vibration response signal.
The implementation that Fig. 9 shows another embodiment of the invention allows to hold based on the pile foundation of freely falling body exciting low strain dynamic
Carry the structural schematic diagram of the detection device of the detection method of power, the pile foundation based on freely falling body exciting low strain dynamic described in a kind of implementation
The detection device of the detection method of plinth allowable bearing includes the exciting unit 1 of freely falling body exciting pile foundation, data acquisition list
Member 2 and data processing unit 3, wherein
Exciting unit 1 includes,
Permanent magnet unit 4, being configured to lead to based on control signal magnetic or disconnected magnetic is adsorbed capable rammer or freely falling body,
Power rams 5, is configured at the top of freely falling body exciting pile foundation to generate vibration response signal, the power rams 5 bottom
Portion is equipped with elastic buffer unit 16, and the power is rammed via pile foundation described in the elastic buffer unit exciting,
Data acquisition unit 2 includes,
First acquisition unit 6, the first acquisition unit for being configured to the impact force signal that acquisition power rams exciting are arranged in power rammer
Top,
Second acquisition unit 7, the second acquisition unit for being configured to acquisition vibration response signal are arranged at the top of pile foundation；
Data processing unit 3 includes,
Time base variable sampling unit 8 is configured to acquire the impact force signal and vibration response signal based on time base variable,
Interception unit 9 is configured to based on predetermined period interception impact force signal and vibration response signal to be based on
The low-frequency vibration response signal of force signal is impacted,
Processing unit 10 is configured to generate base via transmission function based on impact force signal and low-frequency vibration response signal
In the dynamic stiffness curve of vibration frequency, the processing unit determines that the pile foundation is held based on the dynamic stiffness value that vibration frequency is zero
Perhaps bearing capacity.
In detection device of the present invention, the implementation that Figure 10 shows another embodiment of the invention is based on freely falling body
The structural schematic diagram of the detection device of the detection method of the pile foundation allowable bearing of exciting low strain dynamic, exciting unit 1 further include,
Detachable bracket 11 is configured to bearing exciting unit and makes 1 vertical alignment pile foundation of exciting unit, described removable
Unloading bracket 11 includes the pilot unit 12 that alignment pile foundation is rammed for directed force,
Motor 13, the motor for being configured to provide the power for promoting exciting unit 1 are arranged on detachable bracket 11,
Leveling unit 14, is used to level detachable bracket 11, and the permanent magnet unit 4 passes through wirerope and fixed pulley 15
Connect motor 13；
The elastic buffer unit 16 includes Rubber end,
First acquisition unit 6 is acceleration transducer,
Second acquisition unit 7 be velocity sensor or piezoelectric acceleration transducer,
The processing unit 10 includes the switch unit for issuing the control signal of logical magnetic or disconnected magnetic, and processing unit includes number
Signal processor, application-specific integrated circuit ASIC or on-site programmable gate array FPGA, processing unit include memory, the storage
Device may include one or more read only memory ROMs, random access memory ram, flash memory or Electrical Erasable can
Program read-only memory EEPROM.
In one embodiment, the motor that motor 13 is substantially 2 tons of lifting force.
In one embodiment, leveling unit 14 is leveling paper washer.
In one embodiment, permanent magnet unit 4 includes magnet structure.
In one embodiment, pilot unit 12 is guided way.
In one embodiment, 13 1.5~2m of hoisting depth of motor, power ram using 50~600kg weight, using power ram from
The impact to structure is realized by falling bodies impact force.Power rams the Rubber end that bottom uses high-performance rubber production, substantially increases
Low-frequency range energy；Meanwhile it is sliding in order to avoid previous power hammer pressure sensor is arranged in bottom, long-term surge acts on lower screw thread
First acquisition unit 6, is placed in the top of power rammer by the larger problem of de- measured result error, utilizes acceleration and impact force
The conversion of calibration result progress power.The maximum impact force of the present embodiment has been increased to 22 tons, and energy is obviously mainly distributed on low frequency
Section 10Hz or less.
Industrial applicibility
The detection method and detection device of pile foundation allowable bearing based on freely falling body exciting low strain dynamic of the invention
And it can manufacture and use in field of non destructive testing.
Although embodiment of the present invention is described in conjunction with attached drawing above, the invention is not limited to above-mentioned
Specific embodiments and applications field, above-mentioned specific embodiment are only schematical, directiveness, rather than restricted
's.Those skilled in the art are under the enlightenment of this specification and in the range for not departing from the claims in the present invention and being protected
In the case where, a variety of forms can also be made, these belong to the column of protection of the invention.
Claims (10)
1. a kind of detection method of the pile foundation allowable bearing based on freely falling body exciting low strain dynamic comprising following step:
Power is rammed at the top of freely falling body exciting pile foundation to generate vibration response signal, wherein the bottom that the power is rammed is equipped with elasticity
Buffer cell, the power are rammed via pile foundation described in the elastic buffer unit exciting, and the vibration velocity signal includes low frequency
Vibration response signal；
First acquisition unit measuring force rams the impact force signal that exciting generates, and the second acquisition unit measures the vibration that pile foundation generates
Response signal；
Time base variable samples the impact force signal and vibration response signal and intercepts impact force signal and the vibration of predetermined period
Response signal with obtain based on impact force signal low-frequency vibration response signal,
It impacts force signal and low-frequency vibration response signal and generates the dynamic stiffness curve based on vibration frequency via transmission function, be based on
The dynamic stiffness value that vibration frequency is zero in dynamic stiffness curve determines the pile foundation allowable bearing.
2. the detection method of the pile foundation allowable bearing according to claim 1 based on freely falling body exciting low strain dynamic,
It is characterized in that, vibratory response measuring unit is velocity sensor, low-frequency vibration response signal is low-frequency vibration speed responsive letter
Number, force signal and low-frequency vibration speed responsive signal, which are impacted, via transmission function generates the dynamic stiffness curve based on vibration frequency,
The dynamic stiffnessWherein, F (f) is the impact force signal based on frequency, and v (f) is the low frequency vibration based on frequency
Dynamic speed responsive signal, f is frequency, and the dynamic stiffness value for being zero based on the frequency vibrated in dynamic stiffness curve determines the pile foundation
Allowable bearing.
3. the detection method of the pile foundation allowable bearing according to claim 2 based on freely falling body exciting low strain dynamic,
It is characterized in that, generating the auto-power spectrum S of impact force based on impact force signal and low-frequency vibration speed responsive signalFF(f) and
The interaction rate of impact force and vibration velocity composes SFV(f), coherent function γ2(f) it isWork as γ2(f) 0.5 <, really
The fixed impact force signal and low-frequency vibration speed responsive signal are noise.
4. the detection method of the pile foundation allowable bearing according to claim 1 based on freely falling body exciting low strain dynamic,
It is characterized in that, the height of the freely falling body is 1.5-2m, the quality that power is rammed is 50~600kg, and time base variable samples the punching
The frequency acquisition for hitting force signal is 1k-2k, and time base variable multiple is 2-8 times.
5. the detection method of the pile foundation allowable bearing according to claim 1 based on freely falling body exciting low strain dynamic,
It is characterized in that, being extended to the dynamic rigid of the longitudinal axis close to the gentle section of dynamic stiffness curve that vibration frequency is zero in the dynamic stiffness curve
Angle value is Static stiffness value, and the Static stiffness value is based on tolerable settlement and obtains the pile foundation allowable bearing.
6. the detection method of the pile foundation allowable bearing according to claim 5 based on freely falling body exciting low strain dynamic,
It is characterized in that, the gentle section of dynamic stiffness curve is in 5~20Hz frequency range, via linear regression obtain zero hertz it is dynamic just
For degree to be determined as Static stiffness value, the pile foundation allowable bearing is the Static stiffness value multiplied by the tolerable settlement, described
Tolerable settlement is 4 millimeters.
7. the detection method of the pile foundation allowable bearing according to claim 1 based on freely falling body exciting low strain dynamic,
It is characterized in that, power rams the center or pier side center at the top of freely falling body exciting pile foundation, the second acquisition unit cloth
The center at the top of pile foundation is set to measure vibration response signal, power is rammed more to generate at the top of multiple falling bodies exciting pile foundation
Secondary vibration response signal with obtain weighting impact force signal and weighting low-frequency vibration response signal, based on weighting impact force signal and
It weights low-frequency vibration response signal and the weighting dynamic stiffness curve based on vibration frequency is generated by transmission function.
8. the detection method of the pile foundation allowable bearing according to claim 1 based on freely falling body exciting low strain dynamic,
It is characterized in that, the pile foundation includes the single-pile foundation or used multi-column pier foundation of exposed pile crown, the multi-column pier foundation warp
Be located under existing building by cushion cap, power is rammed to generate vibration response signal at the top of freely falling body exciting cushion cap, the power ram via
Cushion cap described in the elastic buffer unit exciting, the second acquisition unit are arranged at the top of cushion cap to measure vibration response signal.
9. the pile foundation allowable bearing based on freely falling body exciting low strain dynamic described in a kind of implementation any one of claim 1-8
The detection device of detection method, which is characterized in that the detection device includes exciting unit, the number of freely falling body exciting pile foundation
According to acquisition unit and data processing unit, wherein
Exciting unit includes,
Permanent magnet unit, being configured to lead to based on control signal magnetic or disconnected magnetic is adsorbed capable rammer or freely falling body,
Power is rammed, and is configured at the top of freely falling body exciting pile foundation to generate vibration response signal, the bottom that the power is rammed is equipped with
Elastic buffer unit, the power are rammed via pile foundation described in the elastic buffer unit exciting,
Data acquisition unit includes,
First acquisition unit, the first acquisition unit for being configured to the impact force signal that acquisition power rams exciting are arranged in power and ram top,
Second acquisition unit, the second acquisition unit for being configured to acquisition vibration response signal are arranged at the top of pile foundation；
Data processing unit includes,
Time base variable sampling unit is configured to acquire the impact force signal and vibration response signal based on time base variable,
Interception unit is configured to be based on impact force based on predetermined period interception impact force signal and vibration response signal to obtain
The low-frequency vibration response signal of signal,
Processing unit is configured to generate via transmission function based on vibration based on impact force signal and low-frequency vibration response signal
The dynamic stiffness curve of frequency, the processing unit determine that the pile foundation allows to carry based on the dynamic stiffness value that vibration frequency is zero
Power.
10. detection device according to claim 9, which is characterized in that exciting unit further includes,
Detachable bracket is configured to bearing exciting unit and makes exciting unit vertical alignment pile foundation, the detachable bracket
Pilot unit including ramming alignment pile foundation for directed force,
Motor, the motor for being configured to provide the power for promoting exciting unit are arranged on detachable bracket,
Leveling unit, is used to level detachable bracket, and the permanent magnet unit connects motor with fixed pulley by wirerope；
The elastic buffer unit includes Rubber end,
First acquisition unit is acceleration transducer,
Second acquisition unit be velocity sensor or piezoelectric acceleration transducer,
The processing unit includes the switch unit for issuing the control signal of logical magnetic or disconnected magnetic, and processing unit includes at digital signal
Manage device, application-specific integrated circuit ASIC or on-site programmable gate array FPGA, processing unit include memory, the memory can be with
It is programmable only including one or more read only memory ROMs, random access memory ram, flash memory or Electrical Erasable
Read memory EEPROM.
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