CN1057338A - Portable nondestructive testing instrument for pile foundation - Google Patents

Abstract

The invention belongs to a kind of device that detects pile foundation quality.It is by sensor, amplifier, and low frequency filter, 12 bit high resolving power high-speed a/d transducers, computing machine, printer and magnetic tape station are formed.It is characterized in that and to calculate the program Solidification of various parameters on the EPROM of computing machine chip, the panorama that makes this device have the waveform time domain shows, carry out the data screen editor, cursor scanning, search are directly measured each reflection wave then, phase place, characteristic frequency and amplitude, computer analysis as calculated obtains pile body rejected region and proterties at last, and the bearing capacity of the vertical and horizontal of pile body.

Description

Portable nondestructive testing instrument for pile foundation

The invention belongs to a kind of device that detects pile foundation quality.

In the civil engineering, under the increasing situation of high-lager building, natural ground can not meet the demands, and the current extensive pile foundation that adopted is also more and more higher to the requirement of concrete-pile rheobase and bearing capacity.How detecting concrete pipe base produces in work progress defective and bearing capacities such as fracture, is an important job.At present, detect the quality and the bearing capacity thereof of pile foundation abroad, all adopt the method for big strain, its specialized apparatus is a pile driving analyzer, and this equipment is except that costing an arm and a leg, and requirement will have open place; And the pile foundation detector that the small strain dynamic measuring method is adopted, (patent No.: 88212156.1), it is a kind of peg equipment of developing on the PC-1500 computing machine as Chinese patent disclosed " concrete pipe base nondestructive dynamic test instrument ".It is by exciting device, signal transducer, and controller, sampling thief and pocket computer are formed, and utilize machine language and BASIC hybrid programming, make sampling, processing integrated.But this equipment can not carry out measurement data screen display and editor, can not intercept useful signal arbitrarily on time domain, also lacks the local function that strengthens of useful signal.Also exist computing velocity slow simultaneously, matching is poor, inconvenient operation, and therefore, it is difficult to obtain the reliable measurement result of high precision.

Therefore the purpose of this device be to propose a kind of by sensor, amplifier, wave filter, the high-resolution A/D transducer of 12 bits, interface board, the pile foundation quality pick-up unit that computing machine and data tape machine and printer are formed, and with the design program Solidification on the stamen sheet of computer-internal.Thereby can improve the accuracy of detection of each parameter, form fast, easy to carry, the multiple functional characteristics that possess computational analysis speed.

Measuring the concrete pipe base quality, is to adopt discharge in water, or the power hammer, or ball etc. makes exciting source pile body is imposed acting force, stake and Pile Soil system is produced vibrate.Use nautical receiving set then, or accelerometer, or velograph goes out various reflection waves and vibration signal in the pile body as sensor.These signals are amplified to desired value, remove high-frequency interferencing signal through filter row again, analog quantity is become digital quantity by the high-resolution A/D transducer of 12 bits.By computing machine time domain waveform is shown, so that whether the observation and inspection exciting force is suitable.When demonstrating complete waveform, can accurately observe various reflection waves then, phase place and amplitude.And, utilize screen to edit according to different analysis purposes, and choose the different piece data and carry out predominant frequency and the amplitude thereof that analysis of spectrum is respectively composed composition at last, judge pile foundation quality and its bearing capacity then.Meanwhile, can Calculation results be recorded on the magnetic tape station automatically, so that do secondary treating and on printer, provide waveform and each test parameter.

Measure the bearing capacity of pile body fracture position and level and vertical direction, the wave frequency of will removing all kinds of obstacles f ₁, survey the natural vibration frequency f of accurate pile body own ₂Vibration frequency F with the Pile Soil system ₃. utilize formula L=C/2f then ₂Obtain fracture position L, wherein c is the speed that sound wave is propagated in pile body.Utilize formula dynamic stiffness Kd=α F(2 π f again) obtain Kd; Obtain allowable bearing Pa according to Pa=α Kd at last, wherein α is a scale-up factor.So frequency f ₂And f ₃The accuracy of measuring directly has influence on the measuring accuracy of bearing capacity.This device adopts rated output spectrum and transfer function method and the program of solidifying in the stamen sheet can be accomplished the accuracy in sampling period, thus guaranteed reflection wave then, f ₂And f ₃Precision.

For accurate analysis to measure f ₂With f ₃, this device can utilize the screen of computing machine to edit; After the signal that the intact sensor of computer acquisition is received, show immediately, the signal of being gathered is differentiated, if run into the signal and can't to make pile body and Pile Soil owing to underexcitation not be that the signal of starting of oscillation is all given it up of transfiniting that occurs owing to excitation is excessive, because the error of calculation that the former brings is bigger, and the latter can't measure frequency f ₂And f ₃. thereby can encourage pile body again, signals collecting again is till collecting desirable signal, as shown in Figure 5.T among the figure ₁-T ₂Between signal be impulse signal, with measure irrelevant; T ₂-T ₃Signal comprises the pile body Natural Frequency of Vibration, utilizes it to carry out FFT, obtains frequency f ₂; T ₃-T ₄The vibration frequency that comprises the Pile Soil system is utilized FFT equally, obtains frequency f ₃

This device can superpose on time domain to weak signal by solidifying the stamen sheet, removes random undesired signal, outstanding useful signal; Get rid of the strong signal of impact and weak signal is amplified 2,4,8,16 or 32 times, thereby realize synchronous humidification weak signal.

By the calculating of pile bottom reflection signal energy, can extrapolate the thickness of pile bottom sediment.The pile bottom reflection signal usually shows as T among Fig. 6 ^' ₁-T ^' ₂Wave form.The area that it comprises is relevant with dragging apart of pile bottom reflection signal amplitude and signal, and amplitude with drag apart have with the pile bottom sediment proterties outside the Pass, also relevant with sediment thickness.Calculate by area, can infer its thickness.

These detections and calculating all solidify by being installed in special use in the EPSON HX-20 type computing machine that stamen sheet EPROM 27C64 realizes.

This device is because each several part is reasonable in design, so its outstanding feature is to have time domain waveform and catches, and the framing panorama shows that signal can superpose, thereby can improve signal to noise ratio (S/N ratio); Sample frequency can be given putting o'clock at 1 to 127 below 20KHz and can both be guaranteed to collect complete waveform and accurate recording reflection wave time of arrival with interior any setting in S to 12.7 second in the scope at 50 μ internal trigger, and weak signal produced synchronously strengthens; Can carry out the data screen editor, choose valid data, remove gibberish, make analysis accurately and reliably; Computing velocity is fast, and 512 FFT rated output spectrums approximately only need 5 second time; Cursor scanning, search, can shows signal time of arrival, frequency and amplitude.Can choose the pile bottom reflection signal and carry out integration, obtain area and estimate pile bottom sediment thickness.This device can be made computing machine usefulness separately, and has the standard BASIC, also can be by the self-editing various judgement application programs of user.From sensor, amplifier, low-pass filter, high resolving power high-speed a/d transducer, computing machine, printer are once assorted to magnetic tape station and combined in the suitcase, and be simple in structure, carries very convenient.Therefore this device can be widely as the on-the-spot visual plant that detects pile foundation quality in the civil engineering process.

Fig. 1 is the block scheme of this device.It is by sensor (1), amplifier (2), and low-pass filter (3), A/D transducer (4), computing machine (5), printer (6) and magnetic tape station (7) are formed.(8) among Fig. 1 are tested pile body, and (9) are limit soil.The sensor of this device (1) can be nautical receiving set, accelerometer or velograph.It can become electric signal with detected pile body mechanical vibration wave from pile body and send into amplifier (2), and amplifier (2) divides 11 grades, can amplify 1 * 2000 times.After signal is amplified to desired value, send into low-pass filter (3) again, the cutoff frequency of this low-pass filter (3) can divide 120Hz, 300Hz, 1000Hz and 2000Hz fourth gear, also can set up on their own.By wave filter (3), unwanted undesired signal is excluded, by the A/D transducer (4) of 12 bits shown in Figure 2 or 8 bits the analog quantity of signal is become digital quantity then.Its sample frequency can be 1 to 20KHz, and be 30 μ S switching time.12 high resolving power high-speed a/d transducers (4), it is a kind of personality board that is equipped with EPSON HX-20 computing machine, be characteristics in address design, the data acquisition mouth is arranged in system interface not on the address of usefulness at computing machine, thus the interference that can avoid address multiplex to bring.This device also is furnished with the special purpose interface plate that data transmit, as shown in Figure 3.By this interface, system can with have buffer, the sampling digit rate is 20KHz to 10MHz, even the collector of higher sample frequency joins, and makes it that the data that high speed acquisition device like this is gathered are sent into this device and carries out analytical calculation.Make this device can also carry out like this to metal or nonmetallic carrying out flaw detection.Therefore this device is again to become a high-resolution reflectoscope.Send into computing machine (5) by the data of A/D transducer (4) collection and carry out various computational analysiss.This computing machine (5) is that a kind of Japan produces EPSON HX-20 type computing machine.The flow chart of this device and is solidificated in this program design on the EPROM 27C64 stamen sheet of 8KB as shown in Figure 4.Thus can be the enterprising line data editor of screen with to the resampling of waveform, choosing intuitively needs the waveform portion handled, pieces together and abandons unnecessary portions, make analyze reliable; Can in parameter setting, make to give putting a little and between the 1-127 point, set arbitrarily simultaneously, make it accurately to record the zero-time of excitation, thereby guaranteed the measuring accuracy of pile body defect part.In addition, can use cursor scanning, the amplitude of measured waveform live part intuitively, reflection wave is then and calculate its characteristic frequency.At last by calculating push away the bearing capacity of defect of pile foundation position and pile foundation.And print various result of calculations through printer (6).Utilize magnetic tape station (7) to write down various data automatically simultaneously.

Fig. 2 is the circuit structure diagram of the A/D transducer of this device.It is by AD7501,74LS75, and LF398,74LS138, components and parts such as the integrated package of models such as AD574, various Sheffer stroke gate, resistance and electric capacity are formed.

Fig. 3 is the interface board circuitry lines composition of this device.It is by LS138, LS244, LS123, various Sheffer stroke gate, resistance, electric capacity, and components and parts such as clock interface are formed.

Fig. 4 is the program design calcspar of this device.

Fig. 5 is for supplying this device computational analysis reflection wave then, the synoptic diagram of frequency and amplitude.Wherein A is a signal amplitude, and t is the time.

Fig. 6 is the synoptic diagram for this device computational analysis pile bottom sediment thickness.Wherein A is a signal amplitude, and t is the time.

A most preferred embodiment of this device is: in a certain dwelling house building site, with the height freely falling body of 30 kilograms hand hammers from 30 centimeters of pile body top end faces, end face on the hammering pile body, record various reflection wave waveforms by accelerometer as sensor end face on pile body then, the signal that receives is sent into the low-pass amplifier that cutoff frequency is 120Hz through amplifying after 1 times, filter various high-frequency interferencing signals, then signal is sent into the high resolving power high-speed a/d transducer of 12 bits, use the sample frequency of 1.6KHz, triggering level is 0.5v, the analog quantity of signal is become digital quantity, and computer is analyzed various parameters as calculated, and to record allowable bearing be 28.1 tons.Obvious, this device can also have the result of implementation of other scheme.

Claims (5)

1, a kind of by exciting device to the pile body application of force, make pile body produce various vibration waves, this ripple is received by sensor (1) and it is become electric signal, amplify through amplifier (1), sample through high resolving power high-speed a/d transducer (4) again, make this continuous wave digitizing, then by computing machine (5) storage and analysis and judgement, last provide pile foundation the cannot-harm-detection device that each parts such as its analysis result are formed through printer, it is characterized in that it also includes one and can get rid of high-frequency interferencing signal, make the clear waves low-pass filter of surveying (3), in computing machine (5), also has an EPROM chip that is solidified with the analysis and judgement program, one is equipped with an interface board between A/D transducer (4) and computing machine (5), make the data of being gathered send into computing machine (5) effectively, whether thereby it is suitable to make this device observe exciting force by computer screen, various reflection waves then, phase place and amplitude, and then utilize screen to edit, up to satisfying the optimum detection effect, the extract effective data are judged the magnetic tape station (7) of the various parameters of pile foundation quality and bearing capacity and an automatic logger computer of energy (5) analysis gained.

2,, it is characterized in that said sensor (1) can be a nautical receiving set according to the said device of claim 1.

3, according to the said device of claim 1, the cutoff frequency that it is characterized in that said low frequency filter (3) can be 120Hz, 300Hz, and 1000Hz, and 2000Hz also can set arbitrarily.

4, according to the said device of claim 1, it is characterized in that said high resolving power high-speed a/d transducer (4) can be 12 bits, also can be 8 bits, its sample frequency can be set arbitrarily in 1 to 20KHz scope.

5, according to the said device of claim 1, it is characterized in that said interface board, it can be that 10MHz or higher collector join with sample frequency.

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