CN102608211B - A method for measuring shear wave velocity of compacted specimens indoors - Google Patents

Abstract

The invention provides a method for testing the transverse wave velocity of an indoor compaction test piece, and the method is used for solving the problems that no definitive methods for testing the transverse wave velocity of an indoor compaction soil sample exist in the prior art. According to the method for testing the transverse wave velocity of the indoor compaction test piece, provided by the invention, the testing on the transverse wave velocity is carried out through adopting a compaction test piece as a test piece for testing the transverse wave velocity, adopting a rigid support as a test piece supporting device, adopting a high-frequency wave detector to test vibration signals and adopting an artificial striking manner to compact the test piece. The method for testing the transverse wave velocity of the indoor compaction test piece, provided by the invention, has the beneficial technical effects that: a method for monitoring the transverse wave velocity of an indoor test piece is provided, not only is the study on the propagation characteristics of waves in a soil and rock composite medium conduced, but also the application of wave testing techniques to geotechnical engineering can be promoted.

Description

A method for measuring shear wave velocity of compacted specimens indoors

technical field

The invention relates to a method for testing the compaction quality and stability of soil foundations, in particular to a method for testing the shear wave velocity of an indoor compaction test piece.

Background technique

At present, in engineering construction, wave test technology is widely used to evaluate the compaction quality and stability of soil foundation (including soil-rock composite foundation), and the interpretation of field test results must be based on the study of wave propagation characteristics of soil-rock composite media, especially through The fluctuation propagation law obtained from the wave velocity test results of soil-rock composite specimens with different water contents, different dry densities, different compaction times, and different soil-rock ratios can provide an important theoretical basis for the interpretation of field wave test results. Compared with rock specimens, due to the large porosity, low wave velocity, fast attenuation of high-frequency signals, and large specimen size of compacted soil samples in the laboratory, accurate wave velocity test values may not be obtained by ultrasonic testing methods. In the prior art, the vibration tester is mainly used to obtain the longitudinal wave velocity of the indoor compacted soil sample, but there is no clear test method for the shear wave velocity.

Contents of the invention

In order to solve the problems in the prior art that there is no clear test method for the shear wave velocity of the indoor compacted soil sample, the present invention proposes a test method for the shear wave velocity of the indoor compacted specimen. The method for testing the shear wave velocity of the indoor compaction test piece of the present invention adopts the compaction test piece as the test piece of the shear wave velocity, adopts the rigid bracket as the support device of the test piece, adopts the high frequency detector to test the vibration signal, and adopts manual striking for compaction The shear wave velocity of the specimen was tested.

Further, the shear wave velocity testing method of the indoor compaction test piece of the present invention comprises the following steps:

100mm×L125mm标准试件；(1) According to the compaction test standard JTGE40-2007 "Highway Soil Test Regulations", the compaction specimens were prepared by electric compaction, and the size of the specimens was

100mm×L125mm standard test piece;

(2) Use the specimen bracket to place the specimen horizontally between two symmetrically arranged rigid supports. One end face of the specimen is connected to the rigid support through a rubber cushion, a trigger detector and a vibration pad, and the other The side end face is connected to the rigid support through the receiving detector and the rubber cushion, and the two rigid supports are tightened by a tie rod and a certain contact stress is applied to the specimen; the detector is a 100Hz horizontal high-frequency detector, and the detector Tin foil or aluminum foil is used for coupling with the test surface of the specimen;

(3) Test parameter setting, set the test parameters according to the sampling interval of 30μs, the sampling length of 4K, the sampling delay of 512 bits, the filtering frequency of 240Hz, and the trigger mode of manual triggering;

(4) Signal collection and testing, signal collection and testing are divided into two parts:

For the first time, a small hammer is used to strike the vibrating plate along the direction parallel to the end face of the specimen, and the vibration signal of the specimen is collected at the same time; backing plate, and collect the vibration signal of the test piece at the same time; find the point opposite to the jump on the waveform diagram of the vibration signal obtained twice, and regard this point as the arrival time of the shear wave, and read the time _t1 and the time when the trigger detector receives the signal The arrival time t ₂ of the wave velocity signal of the receiving detector, that is, the opposite point of the above-mentioned take-off;

(5) Calculation of shear wave velocity

According to the shear wave arrival time t, t=t ₂ -t ₁ , the shear wave velocity v _s of the compacted specimen can be calculated using the following formula:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}$

In the formula: v _s is the shear wave velocity in mm/s; L is the length of the specimen in mm; t is the arrival time of the shear wave in s.

The beneficial technical effect of the method for testing the shear wave velocity of the indoor compaction test piece of the present invention is that the indoor test piece shear wave velocity monitoring method is proposed, which not only helps to study the propagation characteristics of waves in the soil-rock composite medium, but also promotes the application of wave testing technology in rock application in soil engineering.

Description of drawings

Accompanying drawing 1 is the schematic diagram of the shear wave velocity test method of indoor compaction test piece of the present invention;

Accompanying drawing 2 is the waveform diagram of the vibration signal of the embodiment of the shear wave velocity test method of the indoor compaction test piece of the present invention.

The method for testing the shear wave velocity of the indoor compaction test piece of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Detailed ways

Accompanying drawing 1 is the schematic diagram of the shear wave velocity test method of the indoor compaction test piece of the present invention, among the figure, 1 is rubber pad, 2 is shock pad, 3 is test piece, 4 is pull rod, 5 is rigid support, 6 Receiving geophone, 7 is the specimen support, and 8 is the triggering geophone. As can be seen from the figure, the shear wave velocity testing method of the indoor compaction test piece of the present invention comprises the following steps:

100mm×L125mm标准试件；(1) According to the compaction test standard JTGE40-2007 "Highway Soil Test Regulations", the compaction specimens were prepared by electric compaction, and the size of the specimens was

100mm×L125mm standard test piece;

(2) Use the specimen bracket to place the specimen horizontally between two symmetrically arranged rigid supports. One end face of the specimen is connected to the rigid support through a rubber cushion, a trigger detector and a vibration pad, and the other The side end face is connected to the rigid support through the receiving detector and the rubber cushion, and the two rigid supports are tightened by a tie rod and a certain contact stress is applied to the specimen; the detector is a 100Hz horizontal high-frequency detector, and the detector Tin foil or aluminum foil is used for coupling with the test surface of the specimen;

(3) Test parameter setting, set the test parameters according to the sampling interval of 30μs, the sampling length of 4K, the sampling delay of 512 bits, the filtering frequency of 240Hz, and the trigger mode of manual triggering;

(4) Signal collection and testing, signal collection and testing are divided into two parts:

For the first time, a small hammer is used to strike the vibrating plate along the direction parallel to the end face of the specimen, and the vibration signal of the specimen is collected at the same time; backing plate, and collect the vibration signal of the test piece at the same time; find the point opposite to the jump on the waveform diagram of the vibration signal obtained twice, and regard this point as the arrival time of the shear wave, and read the time _t1 and the time when the trigger detector receives the signal The arrival time t ₂ of the wave velocity signal of the receiving detector, that is, the opposite point of the above-mentioned take-off;

(5) Calculation of shear wave velocity

According to the shear wave arrival time t, t=t ₂ -t ₁ , the shear wave velocity v _s of the compacted specimen can be calculated using the following formula:

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}$

In the formula: v _s is the shear wave velocity in mm/s; L is the length of the specimen in mm; t is the arrival time of the shear wave in s.

The beneficial technical effect of the method for testing the shear wave velocity of the indoor compaction test piece of the present invention is that the indoor test piece shear wave velocity monitoring method is proposed, which not only helps to study the propagation characteristics of waves in the soil-rock composite medium, but also promotes the application of wave testing technology in rock application in soil engineering.

Claims (1)

1. indoor transverse wave speed method of testing of hitting real test specimen, it is characterized in that: employing is hit real test specimen and is tested test specimen as transverse wave speed, adopt rigid support as the test specimen bracing or strutting arrangement, adopt high frequency geophone test vibration signal, the transverse wave speed that adopts the mode manually impacted to hit real test specimen is tested, and the method comprises the following steps:

(1) real test specimen is hit in preparation according to Hitting Test Standards on Test JTGE40-2007 " highway earthwork test rule ", adopts the electronic reality of hitting, and sample dimensions is φ 100mm * L125mm standard specimen;

(2) adopt sample stent that test specimen laterally is placed between symmetrically arranged two rigid supports, one side end face of test specimen by rubber spacer, trigger wave detector and hit the backing plate that shakes and be connected with rigid support, the opposite side end face is connected with rigid support with rubber spacer by receiving wave detector, between two rigid supports, strains by pull bar and test specimen is applied to certain contact stress; Described wave detector is the horizontal high frequency geophone of 100Hz, with tinfoil paper or aluminium foil, is coupled between wave detector and test specimen test surfaces;

(3) test parameter setting, the mode that is manual triggers according to sampling interval 30 μ s, sampling length 4K, sampling delay 512 bits, frequency filtering 240Hz, triggering mode arranges test parameter;

(4) signals collecting and test, signals collecting and test are divided into twice:

Adopt for the first time hand hammer to knock and hit the backing plate that shakes along being parallel to test specimen end face direction, gather simultaneously the vibration signal of test specimen; Adopt for the second time hand hammer along with the direction of knocking for the first time opposite direction, knocking and hit the backing plate that shakes, gather simultaneously the vibration signal of test specimen; At the vibration signal of twice acquisition, on oscillogram, find the opposite point of take-off, and this point is considered as to the shear wave due in, read and trigger the time that wave detector receives signal

With the time that receives the arrival of wave detector velocity of wave signal

, i.e. the point that above-mentioned take-off is opposite;

(5) the calculating of transverse wave speed

According to shear wave time of arrival t,

, adopt following formula can calculate the transverse wave speed v of the real test specimen of launching an attack _s:

In formula: v _sFor transverse wave speed, unit is mm/s; L is the length of test specimen, and unit is mm; tFor shear wave time of arrival, unit is s.

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