CN85104819A - The hydroelectric effect method of quality of pile nondestructive test and device thereof - Google Patents

Abstract

The invention provides a kind of new method of quality of pile nondestructive test, the auto-power spectrum of main employing stake is judged the defective of stake.This method adopts the exciting force of hydroelectric effect vibration source emitting sound wave as stake, receives response signal with nautical receiving set, the blattnerphone tracer signal, and the input signal processor is done leaf transformation in the quick pair after the filtering, carries out the work of figure signal form.Thereby can obtain reflecting the multiple information of a defective.Take this as a foundation, formulate the standard of judging pile integrality.The effect one of aqueous medium is filtering in this law, the 2nd, and as the vibration source medium, make this method have test accurately, the signal to noise ratio (S/N ratio) height, easy to use, function is many, the low remarkable advantage that waits of cost.

Description

The hydroelectric effect method of quality of pile nondestructive test and device thereof

The present invention relates to a kind of method of quality of pile nondestructive test, particularly a kind of stress wave of transient state forced vibration.The auto-power spectrum of main employing stake is judged the defective of stake.

Pile foundation is widely used in bridge and construction work, and particularly the application of the cast-in-situ bored pile of different-diameter is wider, has accounted in Europe all with 70% of stake amount.Drilled pile and driven pile can produce fracture for various reasons, and defectives such as snotter and loose concrete are arranged.Spoilage according to foreign statistic hole stake is 5～10%, and this tends to cause very big harm.Though classical De rock stamen inspection technique is reliable, effort, time-consuming, the expense height can only be done sampling check, can not be to generally check of most stakes.And the static test method can not provide poor quality's reason, just provides the result.At present the single pile length that runs in the science of bridge building by several meters to hundreds of rice, diameter is by 1 meter to 2 meters; Soil layer by mud, loess to decayed rock; Pile crown have more than the water surface, have below the water surface.Measuring means should can both be used in these cases.In addition for a clump of piles, single stake and big and have the quality inspection problem under the traffic disturbed condition also should take at the existing field boundary noise of construction.In order to ensure construction quality, be the final acceptance of construction service of stake, need a kind of easy, reliable method of checking steel bar concrete pile.This is that engineering circle is thirsted for the research topic that solves for many years.The nondestructive test technology develops in machinery manufacturing industry comparatively fast, uses wider.But in civil engineering work, be applied to resemble the such resilient elongate rod member that inserts in the soil of stake, because of being subjected to the influence of multiple complicated factor, technical difficulty is bigger.The technical method of Ti Chuing is varied during the last ten years, as the stress wave propagation method, give pipe laying acoustic sounding method, mobility method, ballistic method etc.Details is seen Chinese magazine " external highway " the 1st phase of nineteen eighty-three Pg50 " development of external pile foundation quality nondestructive test technology " .But also there is not a kind of method can satisfy the requirement of the property visited, accuracy and high efficiency simultaneously so far.

Task of the present invention is exactly to overcome the shortcoming of detection method in the past, proposes a kind of new detection method, has test accurately, the signal to noise ratio (S/N ratio) height, and easy to use, function is many, the low remarkable advantage that waits of cost.Only with regard to vibration source, spark polarization source has similarity in it and the marine oil seismic prospecting.This kind method is used for the quality of pile nondestructive test and still belongs to the first time.

Task of the present invention is finished as follows:

1, adopt the hydroelectric effect vibration source when electrode in water during the instantaneous pressure discharge, the aqueous medium that the electrode gap environs is the very little gasification that heats up rapidly, formation High Temperature High Pressure air mass, thereby the very powerful pulsed pressure wave of formation, Here it is so-called hydroelectric effect.Use hydroelectric effect vibration source emission burst pulse, wide band sound wave is characterized in not changing the frequency spectrum of response signal as the exciting force of stake.Its energy is big, and pressure is up to several thousand atmospheric pressure, be enough to make vibration wave to pass to by the stake top at the bottom of reflected back stake top again, thereby make that the amplitude of response signal is bigger.And ultrasound wave does not then possess this advantage because decay is excessive.This pulsed force function time is very short, has only tens of microseconds.The sound wave that produces is a broadband at frequency field f＜1000HZ, thereby does not change the frequency spectrum of response signal, and this point is very important.Adopt this method test speed fast, exciting is convenient, good reproducibility.The energy of each time exciting can be controlled about equally.

2, after the application asdic method receives response signal stake excited target, produce compressional wave, shear wave and surface wave simultaneously.Reflexing to the compressional wave that stake is pushed up along stake, can reflect the integrality of whole pile body structure, is the useful signal that need will receive, and back two is undesired signal.In order clearly to differentiate compressional wave, must manage elimination shear wave and surface wave, to improve the signal to noise ratio (S/N ratio) of institute's tracer signal.General method is to adopt wave filter, but when the diameter of stake is big, and the frequency approach of surface wave is in the frequency of input pulse, so no longer can enough wave filters.The modulus of shearing of utilizing water is zero, can not transmit the characteristic of shearing strain, on the stake top water pipe is installed, and with the shear wave and the surface wave of aqueous medium elimination reflected back stake end face, they all belong to shearing wave.Use the nautical receiving set received signal then.Because of signal of vibrating is a burst pulse, broadband, used nautical receiving set and reception instrument also are wide band, can reflect the frequency spectrum of stake faithfully so comprise the frequency spectrum of the total system of vibration source, stake, nautical receiving set, and the signal of Jie Shouing can be eliminated the influence of test macro preferably like this.Nautical receiving set also claims wave detector, and this test is adopted is actually a piezoeletric quartz sensor, is placed on and just can receives the vibration acceleration signal that pile crown responds in the water, uses the blattnerphone tracer signal, and then shear wave and surface wave promptly are excluded.Record also comprised water in water pipe radial vibration and the pipe in the signal vertical to the level of reaching to reflected signal, the frequency of these signals is all greater than 1000HZ, use the low-pass filter elimination, whole test repeats repeatedly, each 5～15 seconds time intervals, signal data is averaged computing, thus stochastic error that can erasure signal, the neighbourhood noise in promptly can erasure signal.After taking the measure of above several respects, the signal to noise ratio (S/N ratio) of signal is improved greatly, can reach more than the 40db.Even have traffic to disturb on every side and the existing field boundary of construction disturbs, also can test exactly, big convenience the carrying out of work for inspection.

3, the processing of response signal is with signal data processor or the signal that receives with digital signal frequency spectrograph nautical receiving set, use the blattnerphone record, behind the unwanted high-frequency signal of low-pass filter elimination, send into signal data processor and do rapid fourier change, carry out the work of figure signal form.Squiggle in the time domain transformed to draw auto-power spectrum etc. in the frequency field.Carry out the auto-power spectrum analysis to mixing the signal that noise is arranged, can give prominence to useful information better, thereby further remove unwanted composition at random in the signal, comprise the interference that test macro is brought into.This method is a data-signal by converting analogue signals, can handle automatically signal data, than sunykatuib analysis much superior.

Because the existence of defective in the stake, the frequency spectrum of its reflected impulse has been different from the frequency spectrum of full pile, therefore adopts spectrum analysis to discern the defective of stake and the ability of reflective sound wave is important.Reflected impulse to sound wave, what utilize usually only is the size of pulse amplitude or the time that pulse arrives, and other many useful informations in the signal have been ignored, thereby can not fully judge defects property, more perfect signal Processing should comprise auto-power spectrum, phase spectral analysis and oscillogram and other many parameters.Thereby analysis result carried out secondary treating.The signal that nautical receiving set is received through the single treatment of signal processor, is drawn oscillogram automatically, thereby is obtained the pile crown counter-force generally speaking; Through secondary treating, transform to the auto-power spectrum of getting back behind the frequency domain, thereby as can be known dominant frequency numerical value, amplitude than and velocity of wave.

If existing field boundary receives, can adopt the digital signal frequency spectrograph to analyze.

To important engineering, the meter that gathers way is placed in outside a sidewall or the water pipe, receive pile crown vibration velocity signal, except drawing equally the above-mentioned signal data, also can carry out transfer function analysis simultaneously with the signal of nautical receiving set, be power as a passage, when two passages are speed, obtain admittance amplitude (V)/(F)～f curve and phase spectrum, can calculate admittance mean value, and can propose difference on the frequency by transport function, dynamic stiffness, to above-mentioned information play a part to check, verification.

4, formulate the standard of judgement pile integrality with above-mentioned 10 kinds of information via analyses, contrast and checkings, the signal that reflects different defectives is concluded, classified, set up corresponding relation with the integrality of stake, and take this as a foundation, formulate the standard of judging pile integrality.It below is the comprehensive criterion table of pile integrality.

Judge the comprehensive criterion table of pile integrality

One, basic criterion (signal of nautical receiving set is carried out data processing and gets)

In most cases, use the integrality that basic criterion promptly can be judged stake.But, at this moment then need to use assistant criteria and do further careful judgement owing to due to the complicacy and test error of actual stake, run into a small amount of stake sometimes not in full conformity with above-mentioned condition.

Two, assistant criteria (signal of nautical receiving set and velograph is carried out data processing and get)

Below with reference to accompanying drawing the hydroelectric effect device is described in further details:

Fig. 1 is the basic circuit diagram of hydroelectric effect vibration source.

Fig. 2 is that the diagrammatic sketch and the signal of hydroelectric effect device receives block diagram.

Fig. 3 is that signal data is handled block diagram.

Device is divided into three parts, promptly

1) stake top portion

Be placed in stake top, the reinforced concrete water pipe (1) of enough rigidity is arranged, high 0.8～2 meter, 5～10 centimetres of wall thickness, its diameter is approaching with the diameter of stake (5), and the water pipe center line coincides with the axis of stake, hold full water during work.Coaxial electrode (2) is placed the position of the interior water of pipe apart from 0.3～0.5 meter of stake end face, be positioned on the axis of stake, make stake under than pulse effect uniformly, produce extensional vibration.Nautical receiving set (3) is placed near stake end face center, but discord stake position contacting is better, and spacing is 1～3 centimetre, can receive the later reflected signal of aqueous medium filtering as soon as possible like this.

Above-mentioned concrete pipe can replace with steel pipe, 0.8～2 meter of its height, 1～2 centimetre of wall thickness.

2) midget plant of generation heavy impulse current

Its circuit diagram as shown in Figure 1, wherein 220 volts of AC power are through step-up transformer T₁₁, T₂₁, high tension silicon rectifier D₁And current-limiting resistance R₁To capacitor C₁Charging is charge circuit.By capacitor C₁, auxiliary gap K₁, discharge cable and sparking electrode (2) constitute discharge loop.An Button K₂, capacitor C₂, resistance R₂, rectifier D₂, step-up transformer T₂₂With K₁It then is firing system.Decide the voltage auto-ignition circuit owing to designed in the device, when repeating to excite, can make the energy that at every turn excites equal substantially.The vibration source control desk all concentrates in together charging, discharge and firing system, increases the regulator potentiometer sum counter, carries out control automatically.The time interval of regulator potentiometer is selected arbitrarily between 5～15 seconds.

The electrode (2) of discharge is a coaxial electrode in this example, and it links to each other with the midget plant of above-mentioned generation heavy impulse current.Discharge parameter is generally 2～10 microfarads, and 6000～12000 volts and with 4 microfarads, 9000 volts is good, its produce power is 162 joules.The damping that runs into stake is when big, can suitably add macro-energy to 250 joule.

3) instrument and equipment of reception and processing signals

Existing field boundary receives and the instrument of analytic signal is made up of blattnerphone and digital signal frequency spectrograph.

The instrument block diagram that receives and take back signal that in office analysis is recorded as shown in Figures 2 and 3.

Settle velograph (4) outside the water pipe on stake sidewall or stake top, it can link to each other with microphone amplifier, hyperchannel tape sound-track engraving apparatus, low-pass filter, signal processor, X-Y recorder together with nautical receiving set.

The advantage of hydroelectric effect method is:

One, degree of accuracy height. 632 piles have been tested at present. To single pile to 6～60 meters of length, 0.6～1.8 meter of diameter, the maximum of draw ratio be 66 the stake did check, basically consistent with destructive sampling inspection result, giving of defective locations estimated deviation is: 95% confidential interval is (0.65 meter, 1.35 meters).

Two, function is many

Both can check single pile (comprising the underwater stake of pile crown), and can check again the post under the framed bent pier to reach A clump of piles. Whether complete to pile body, the position of the one or multi-channel plane of disruption, vary in diameter and concrete quality (by the velocity of wave height) all can propose correct judgement. Or during known velocity of wave, instead ask stake long. And the impedance method of France can only be surveyed single pile, and draw ratio can reach 30 less than 20(at soft soil horizon, then belongs to exception), and can not survey stake under a clump of piles and the framed bent pier.

Three, in this way, the signal to noise ratio height, antijamming capability is strong, no matter when all can test, and need not interrupt near traffic. Check speed is fast, only needs a few minutes the formal Check-Out Time of every pile. The impedance method of France then can only be carried out in night.

Four, remarkable in economical benefits

The inspection cost of every pile takes than much lower times of Chuan Tong rock stamen method, take 30 meters long stakes as example, can save 8000 yuan for every.

Claims (11)

1, a kind of stress wave of quality of pile nondestructive test, exciting mode is the transient state forced vibration, it is characterized in that adopting hydroelectric effect vibration source emission burst pulse, wide band sound wave is as the exciting force of stake, receive response signal with the wide band nautical receiving set that has that can the elimination shearing wave, store this signal with the blattnerphone record, behind the wherein unwanted high-frequency signal of low-pass filter elimination, the input signal processor is done fast fourier transform, remove in the signal unwanted composition at random and carry out by the work of time domain to the figure signal form of frequency field, automatically draw oscillogram by X-Y recorder at last, spectrogram and autopower spectrum figure, thus the pile crown counter-force obtained, fundamental frequency, the amplitude ratio, multiple information such as velocity of wave.With above-mentioned information via analysis, contrast and checking are concluded the signal that reflects different defectives, and classification is set up corresponding relation with the integrality of stake, and taken this as a foundation, and formulates the standard of judging pile integrality.

2, the method for claim 1, it is characterized in that outside the water pipe on stake sidewall or stake top, settling velograph, the speed responsive signal that obtains carries out transfer function analysis simultaneously with the signal of nautical receiving set reception, obtains checking admittance amplitude (V)/(the F)～f curve of above-mentioned information and difference on the frequency, dynamic stiffness.

3, hydroelectric effect method as claimed in claim 1, it is characterized in that blattnerphone record in the signal frequency greater than the water pipe radial vibration of 1000HZ and water vertical to and level to reflected signal low-pass filter elimination.

4, as claim 1,2 described methods, it is characterized in that whole test repeats repeatedly, in each 5～15 seconds time intervals, signal data is averaged computing, with the stochastic error of erasure signal.

5, as claim 1,2 described methods, it is characterized in that it both had been applicable to single pile, also be applicable to a post and a clump of piles under the framed bent pier.

6, a kind of for using the custom-designed isolated plant of above-mentioned hydroelectric effect method, it is characterized in that it by the water pipe with enough rigidity (1) that is placed in stake top, place the sparking electrode (2) and the nautical receiving set (3) of water in the pipe to form.Electrode (2) links to each other with a midget plant that produces heavy impulse current.Nautical receiving set is connected with blattnerphone, low-pass filter, signal processor and X-Y recorder.

7, device as claimed in claim 6 is characterized in that said water pipe is reinforced concrete pipe or steel pipe, and their diameter is more smaller than the diameter of stake, and full water is held in the dead in line of its axis and stake during test.

8, the water pipe of concrete as claimed in claim 7 or steel is characterized in that the concrete pipe height is 0.8～2 meter, 5～10 centimetres of wall thickness.0.8～2 meter of steel pipe height, 1～2 centimetre of wall thickness.

9, device as claimed in claim 6 is characterized in that said electrode is a coaxial electrode, places 0.3～0.5 meter of distance stake end face on the interior center line of pipe, and discharge parameter is 2～10 microfarads, 6000～12000 volts, and with 4 microfarads, 9000 volts is good.

10, device as claimed in claim 6 is characterized in that said nautical receiving set is placed on the axis of stake, apart from stake top 1～3 centimeters.When being used for existing field boundary and analyzing, it is connected with blattnerphone, digital signal frequency spectrograph.When being used in office analysis, it is connected with blattnerphone, low-pass filter, signal processor, X-Y recorder.

11, device as claimed in claim 6, it is characterized in that settling velograph outside the water pipe on stake sidewall or stake top, it can be connected with microphone amplifier, hyperchannel tape sound-track engraving apparatus, low-pass filter, signal processor, X-Y recorder together with nautical receiving set.

Images