CN101413276B - Method for nondestructively detecting highway guard rail upright post basic soil compaction degree by ultrasonic guide wave - Google Patents

Abstract

The invention relates to a method for nondestructively detecting the degree of compaction of foundation earth of a crash barrier post by using ultrasonic guided waves, which belongs to the field of nondestructive detection. The method comprises the following steps: firstly, determining parameters of the crash barrier post before embedding, and calculating the group velocity dispersion curve and the attenuation dispersion curve of the post before embedding the post into the ground; secondly, selecting a detecting frequency from the group velocity dispersion curve, and inputting the detecting frequency into an arbitrary function generator to generate a single-audio signal so as to excite a longitudinal axisymmetric guide wave mode in the post through a power amplifier module, a change-over switch module and a guided wave transceiver element; and thirdly, generating an end face back wave when the guided wave mode barges up against the end of the post, and transmitting the end face back wave to an oscilloscope through the guided wave transceiver element and the change-over switch module. The magnitudes of the end face back waves which are transmitted twice are determined and the guided wave signal attenuation is calculated; and the degree of compaction of the foundation earth can be determined through calculating the value of the attenuation factor. The method has the advantages of no damages to the post and the structure of the foundation earth, quick speed, low detection cost and the like.

Description

Utilize the method for supersonic guide-wave Non-Destructive Testing highway guard rail upright post basic soil pressure solidity

Technical field

The present invention relates to a kind of method of utilizing the supersonic guide-wave Non-Destructive Testing partly to be embedded in basic soil pressure solidity around the high speed highway guardrail upright post in the roadbed, belong to the Non-Destructive Testing field.

Background technology

Subtend track initiation traffic hazard for preventing to go out highway or sail highway at the automobile of running on expressway all set up anticollision barrier in the trackside of Modern High-Speed highway and the central partition, and fence upright is the main load bearing component of guardrail.Because the complicated condition around the guardrail, in burying process underground, cause the basic soil pressure solidity deficiency around the column easily, cause that the crashworthiness of fence upright descends, to the communications and transportation hidden danger that causes the accident.Because highway guard rail upright post partly is embedded in the roadbed of highway, its failure mode exists very strong disguise, it is effectively detected particularly bury the very big difficulty of ground part existence.

National standard employing method at present is to irritate the compactness that micromicrofarad and core cutter method etc. detect highway subgrade, can cause destruction to a certain degree to the roadbed of highway, does not see the relevant report of utilizing the supersonic guide-wave method to detect guardrail basis soil compaction degree at present.

Summary of the invention

The objective of the invention is to propose a kind of new high speed highway guardrail upright post detection method of basic soil pressure solidity on every side, this method can detect highway guard rail upright post basic soil compaction degree on every side simply, quickly and accurately under the prerequisite of not destroying highway subgrade.

The present invention is a kind of method of utilizing the supersonic guide-wave Non-Destructive Testing partly to be embedded in basic soil pressure solidity around the fence upright in the different medium, and this method detects according to the following steps:

1) determines interior diameter, overall diameter, wall thickness, density, longitudinal wave velocity, the transverse wave speed of detected fence upright, shear wave attenuation coefficient, compressional wave attenuation coefficient; Calculate the group velocity dispersion curve and the decay dispersion curve that do not bury the ground column;

2) never bury ground the column dispersion curve on selecting frequency in 50kHz～270kHz scope, the vertical axisymmetry mode institute respective frequencies of group velocity in 5150～5420m/s scope detects frequency, in this frequency and group velocity scope, vertically axisymmetry mode bury the ground part and do not bury ground velocity of propagation partly identical, and pad value is less, enough distances can be propagated, the amplitude of calculating the attenuation coefficient needed first time of end face echo and the end face echo second time can be accessed;

4) with selected detection frequency input arbitrary-function generator, arbitrary-function generator generates centre frequency and detects the single audio signal of frequency for this, after amplifying, power amplifier module obtains higher driving voltage, transfer to the guided wave R-T unit that places the fence upright end that is embedded in roadbed by the Signal Separation switch module, excitation longitudinal axis symmetry guided wave modal in fence upright; The end that this guided wave signals runs into the under ground portion of column produces reflection, forms echoed signal, and this guided wave modal can come back reflective between the upper and lower end face of column, forms once above end face echoed signal; Receive this end face echoed signal by same guided wave R-T unit, transfer to oscillograph through the Signal Separation switch; Determine the peak-to-peak value A of lower surface echo for the first time by the end face reflection oscillogram that oscillograph shows ₁Peak-to-peak value A with the lower surface echo second time ₂

4) never bury in the decay dispersion curve of ground column and read the attenuation coefficient that detects under the frequency, and multiply by the length of column, obtain the pad value Att of column when not burying ground ₀

5) calculate attenuation coefficient according to the following steps

Be calculated as follows part and bury the pad value of ground column:

Att＝-20log ₁₀(A ₂/A ₁)

Calculate because soil absorbs the attenuation coefficient that causes

6) value of different attenuation coefficients can be represented different guardrail basis soil compaction degree, and the size of attenuation coefficient value shows the column height of basic soil compaction degree on every side.

Described guided wave R-T unit is for being piezoelectric supersonic guided wave sensor or magneto strictive sensor.

The present invention mainly has the following advantages: 1) can realize the Non-Destructive Testing to the real degree of guardrail basis soil pressure; 2) used frequency range far exceeds outside nature and the common vibration frequency range, not influenced by operating mode; 3) highway subgrade is not destroyed, detection speed is fast, and it is low to detect cost.

Description of drawings

Fig. 1 pick-up unit schematic diagram

Fig. 2 detection method schematic flow sheet

Fig. 3 fence upright buries the ground part and does not bury the group velocity dispersion curve figure of ground part.Solid line represents to bury the dispersion curve of ground part among the figure, and the dispersion curve of ground part is not buried in the dotted line representative

The die-away curve of Fig. 4 column

The fence upright end face reflection waveform that Fig. 5 pumping signal centre frequency is received when being 180kHz

Fig. 6 soil compaction rate 1 time, the pumping signal centre frequency is received when being 180kHz is embedded in fence upright end face reflection waveform in the roadbed

Fig. 7 soil compaction rate 3 times, the pumping signal centre frequency is received when being 180kHz is embedded in fence upright end face reflection waveform in the roadbed

Fig. 8 soil compaction rate 5 times, the pumping signal centre frequency is received when being 180kHz is embedded in fence upright end face reflection waveform in the roadbed

Fig. 9 soil compaction rate 8 times, the pumping signal centre frequency is received when being 180kHz is embedded in fence upright end face reflection waveform in the roadbed

The relation curve of Figure 10 compactness and attenuation coefficient

Embodiment

Provide following examples below in conjunction with content of the present invention:

As shown in Figure 1, the present embodiment central post is length 1200mm, interior diameter 105mm, overall diameter 114mm, the weldless steel tube of wall thickness 4.5mm.Density is 7800kg/m ³, longitudinal wave velocity is 5960m/s, and transverse wave speed is 3260m/s, and the compressional wave attenuation coefficient is 0.002np/wl, and the shear wave attenuation coefficient is 0.001np/wl, the length of burying the ground part is 300mm.

1), calculates group velocity dispersion curve and decay dispersion curve, in 50～270kHz scope, group velocity is that 5400m/s selecting frequency 180kHz is as detecting frequency according to the parameter of fence upright;

2) column placed into the soil, and with compaction hammer with soil ramming to certain compaction rate.

3) will detect frequency input arbitrary-function generator 1, arbitrary-function generator 1 produces the single audio signal that centre frequency is 180kHz.Carry out voltage amplification through power amplifier module 2, put on the guided wave receiving/sending element 4, in tested column, produce longitudinal axis symmetry guided wave modal through change-over switch module 3; Guided wave receiving/sending element 4 is made up of piezoelectric probe, magnetostriction probe;

4) above-mentioned longitudinal axis symmetry guided wave modal is in the other end of column reflection, and guided wave receiving/sending element 4 receives the end echoed signal of longitudinal wave guide, through change-over switch module 3, behind the amplified current signal, sends into oscillograph 5;

5), determine the amplitude of twice end face echo according to the end face reflection oscillogram that shows on the oscillograph 5.

Fig. 7-10 is for being received under the 180kHz frequency, and four kinds of different compactions partly are embedded in the high speed highway guardrail upright post end face reflection oscillogram in the roadbed down.

6) attenuation coefficient of signal calculated.

Numerical value when following computation process is only listed compaction 8 and computation process

When 180kHz, the peak-to-peak value of end face echo is 198.95mV for the first time, and the peak-to-peak value of end face echo is 105.41mV for the second time.

Do not bury the pad value Att of ground column ₀=0.668 * 1.2=0.802dB

Partly bury the pad value of ground column

Att＝—20log ₁₀(A ₂/A ₁)

＝—20log ₁₀(105.41/198.95)

＝5.517dB

Calculate because soil absorbs the attenuation coefficient that causes

$=\frac{5.517-0.802}{2\×0.3}$

$=7.86\mathrm{dB}/m$

7) obtain compactness according to the core cutter method among the JTJ-051-93 " highway geotechnique experiment rules ".

8) by changing the size of soil compaction rate, repeating step 3～7 obtains the relation of attenuation coefficient and the different compactnesss of soil.

Following table is the guided wave attenuation coefficient of the correspondence that records under the different soils pressure degree.

Table one

The soil compression degree	Attenuation coefficient dB/m	Compactness
				1	2.18	54.40％
2	2.54	56.30％
			3	3.05	60.00％
4	3.88	63.44％
			5	4.87	67.70％
6	5.66	70.45％
			7	6.54	74.30％
8	7.86	80.20％

When Figure 10 is 180kHz, the corresponding relation of attenuation coefficient and upright post basic soil pressure solidity under the different soils compaction rate.

Can be in engineering reality according to concrete fence upright specification, go into ground length, soil regime, make and be similar to the attenuation coefficient shown in Figure 10 and the curve of compactness, as calibration curve.In actual detected,,, determine the basic soil pressure solidity of correspondence then by the inquiry calibration curve by the attenuation coefficient size of the definite actual measurement of detection method recited above.

Claims (2)

1. utilize the method for supersonic guide-wave Non-Destructive Testing highway guard rail upright post basic soil pressure solidity, it is characterized in that this kind method detects according to the following steps:

1) determines internal diameter, external diameter, the density of stud materials, longitudinal wave velocity, transverse wave speed, compressional wave attenuation coefficient, the shear wave attenuation coefficient of detected column, calculate the group velocity dispersion curve and the decay dispersion curve that do not bury the ground column;

2) selecting frequency is in 50～270kHz scope from the group velocity dispersion curve of embedding front column, and the vertical axisymmetry mode pairing frequency of group velocity in 5150～5420m/s scope is as detecting frequency;

3) with selected detection frequency input arbitrary-function generator (1), arbitrary-function generator (1) generates centre frequency and detects the single audio signal of frequency for this, driving voltage after power amplifier module (2) obtains amplifying, transfer to the guided wave receiving/sending element (4) of the upper end that places the fence upright (6) that is embedded in roadbed (7) by Signal Separation switch (3), excitation longitudinal axis symmetry guided wave modal in fence upright; This guided wave modal can come back reflective between the upper and lower end face of column, form once above end face echoed signal, receives this end face echoed signal by same guided wave receiving/sending element (4), transfers to oscillograph (5) through Signal Separation switch (3); Determine the peak-to-peak value A of lower surface echo for the first time by the end face reflection oscillogram that oscillograph (5) shows ₁Peak-to-peak value A with the lower surface echo second time ₂

4) never bury in the decay dispersion curve of ground column and read the attenuation coefficient that does not bury the ground column that detects under the frequency, and multiply by the length of column, calculate signal pad value Att in column before burying ground ₀

5) be calculated as follows the pad value Att that the ground column is buried in detection frequency lower part:

Att＝-20log ₁₀(A ₂/A ₁)

Be calculated as follows because soil absorbs the attenuation coefficient that causes

6) the different guardrail basis soil pressure solidity of the value representation of differential declines coefficient, the size of attenuation coefficient value shows the column height of basic soil pressure solidity on every side.

2. the method for utilizing supersonic guide-wave Non-Destructive Testing highway guard rail upright post basic soil pressure solidity according to claim 1 is characterized in that: described guided wave receiving/sending element (4) is supersonic guide-wave sensor or magneto strictive sensor.

Images