KR20100063177A - Measurement method and device of characteristics of soil compaction in laboratory - Google Patents

Abstract

PURPOSE: A method for measuring compaction of soil compaction material is provided to know compaction degree in a real time and to calculate compaction management standard. CONSTITUTION: A method for measuring compaction of soil compaction material comprises: a step of measuring vibration reach speed by installing an accelerometer in a depth of loading plate and soil compaction material to analyze vibration response; a step of determining wave transmission rate; a step of determining response characteristic value for obtaining specific relative density.

Description

{Measurement method and device of characteristics of soil compaction in laboratory}

The present invention relates to a method and apparatus for measuring compaction characteristics indoors of fill material, and in detail, vibrating rollers and ground vibrations used in the construction of civil structures by compacting assembly materials at various construction sites such as dams, breakwaters, and road embankments. The present invention relates to a method and apparatus for measuring compaction characteristics of a fill material, which can be used to analyze the acceleration response characteristics during compaction to grasp the compaction degree of a fill ground in real time.

Shear strength and deformation characteristics of materials used for construction in dams, breakwaters, road works, etc. are the most important engineering properties in the design of stability and prediction of settlements, so that high-quality materials are used to ensure a certain density. Although it is most desirable to use it, it is difficult to secure high-quality materials depending on the site conditions, and it is necessary to use poor materials. In this case, the method of satisfying the design conditions is to secure good compaction level. Can be.

In particular, when granular materials such as crushed stone are used, such as fill dams or road fills, the mechanism of compacting loads has not yet been clearly established theoretically. However, the strength and shape of the particles, the particle size distribution, the form of compaction load, whether the particles are crushed, the influence of water, etc. are known to be complicated and influenced by the compaction.

Therefore, in order to secure the stability of these structures, the required strength, deformability, and drainage should be measured. In designing the stability of the body, the circular activity surface method is usually used, which means that the building material should have the required shear strength. In the case of rock-fill material, sinking behavior and drainage behavior should be appropriate, and compaction management is to adjust to have required shear strength, deformation characteristics and drainage characteristics.

As such, there are two types of quality control by compaction: test method and visual confirmation.

First of all, the test method is to make an appropriate quality control standard (committed degree) in advance, and conducts a test based on the value and manages it according to the test result. Homogeneity can also be determined as a whole.

On the other hand, the visual method is a method of visually judging the construction state, focusing on whether the construction is properly performed, how the material state is, and whether the uniformity is secured. Recently, it is a trend to adopt high-quality on-site quality management technology that utilizes IT technology rather than the visual method with many individual errors.

An object of the present invention is to build an acceleration measurement system on the vibration compaction equipment and artificial ground in the room to analyze the response characteristics of the vibration compactor and the ground during vibration compaction, and use the vibration roller and the ground used in the embankment construction site based on the test results. Analysis of acceleration response characteristics during vibration compaction to grasp the compaction level of the soil in real time, and measure the wave propagation speed by depth of the ground soil to find the correlation with the compaction level of the soil soil. To calculate.

In order to achieve the above object, the present invention provides a laboratory test method for performing compaction management based on response characteristic values and a measuring method for determining compaction characteristics for each compaction depth.

Compact management by response characteristic value

The acceleration value obtained from the vibration accelerometer installed on the ground by vibration compaction changes as the compaction frequency increases. As shown in Fig. 1, when the number of compactions is small, the ground state stiffness is small and similar to the fundamental frequency. However, as the compaction progresses and the ground stiffness increases, the waveform of the frequency changes to a shape different from the basic frequency waveform. The reason for this is that as the vibration compaction of the ground progresses, the rigidity in the ground increases, and various frequencies are generated and synthesized at the fundamental frequency.

As shown in Fig. 2, after filtering by a band-pass filter (BPF) which is adapted to correspond to several frequencies including the basic vibration frequency, the amplitude corresponding to each frequency is detected.

In the calculation processing method based on the detected amplitude value determined here, the degree of compaction (ground strength) is determined using the equations proposed in the following equations (1) to (3).

Soil wave velocity distribution

The deformation or displacement of the soil generally depends on the stiffness of the soil rather than its strength. That is, in the case of soil having the same strength, if the stiffness is small, more deformation or displacement occurs with respect to the same external force than the soil with large stiffness. The engineering parameters representing soil stiffness are the modulus and Poisson's ratio. Such deformation coefficients include Young's modulus E, shear modulus G, and volumetric modulus K, which are widely known.

    In general, the wave propagation rates Vp and VS can be estimated from the Young's modulus E and the shear modulus G, respectively.

Knowing the shear wave velocity V _s from the above equation, E and G can be calculated. That is, in the experiment, the wave is generated by excitation in the soil to measure the time difference between the generation time t0 of the wave and the arrival times t1, t2, and t3, and divided by the time for the transmission distance (Vp or S = s / ( t1-t0)) can be used to find the wave propagation speed.

The present invention establishes the acceleration measurement system in the vibration compaction equipment and artificial ground indoors to analyze the vibration characteristics of the vibration compactor and ground during vibration compaction, and the vibration of the vibration roller and the ground used in the embankment construction site based on the test results. By analyzing the acceleration response characteristics during compaction, it is possible to grasp the compaction level of the soil in real time, and to measure the wave propagation speed by the depth of the ground, and to find the correlation with the compaction level of the soil. It has a useful effect that can be estimated.

Hereinafter, with reference to the accompanying drawings, preferred embodiments that do not limit the present invention will be described in detail.

Referring to the procedure for measuring the vibration transmission speed using the indoor compaction characteristic measurement system of the present invention.

First, the vibration experiment was performed to determine the correlation of the response response to the relative density, the vibration device as shown in Figure 3 to analyze the vibration response in the ground compaction and depth by the surface compaction as well as the response of the excitation device The experiment was carried out by installing the accelerometer at the predetermined depth of the loading plate and the fill material of the phosphorus vibration tester.

① Prepare experimental equipment such as accelerometer, data logger (see Fig. 4)

② Membrane attached to the bottom and wall of container 60cm in diameter and 60cm in height to reduce the reflection of vibration wave (see Fig. 5)

③ Dividing the ground (standard yarn) into three floors and installing the accelerometer in the center of the container after filling each floor (see Fig. 6).

④ After installing a 10cm thick iron plate to compact the whole ground to increase the relative density, (see Figure 7)

⑤ Compaction to a certain height with a compactor (see Fig. 8)

⑥ Measure the height of the ground to calculate the density (see Fig. 9)

⑦ Measure vibration reaching speed (see Fig. 10)

⑧ Vibration test plate (15cm and 26cm) preparation and vibration test (see Fig. 11)

⑨ Repeat steps 4 to 8 as many times as you want to perform vibration test by relative density.

결과 Analyze results obtained from vibration reaching speed test and vibration test

The following is a procedure for analyzing the wave propagation speed and response characteristics measured using the indoor compaction characteristic measurement system of the present invention.

The analysis of wave propagation speed is performed to determine the propagation speed of wave that can infer the distribution of compaction according to the compaction depth and the relative density of the soil. This is done to determine the response characteristic value to find the specific relative density for.

Wave Propagation Rate Analysis

① Measure the total depth of the filled soil and the distance between each accelerometer.

② Apply strike vibration to the board.

③ Measure the initial starting time of each accelerometer at the time of the vibration price. (See Fig. 12).

④ Calculate the propagation speed of waves between each acceleration by dividing the distance between each acceleration measured in ① by the start time measured in each accelerometer measured in ③.

⑤ Calculate the correlation between the relative density and the propagation speed of each soil.

⑥ Based on the correlation calculated in ⑤, determine the wave propagation speed corresponding to the management relative density of the target soil.

Response characteristic analysis

① Measure the relative depth of the filled soil which was compacted in the container and find the relative density.

② Provide excitation force for each frequency to fill ground through loading board.

③ Measure the response to the excitation force in each accelerometer.

④ After filtering is performed to remove noise from the response of each accelerometer measured in ③, FFT analysis is performed (see Fig. 14).

⑤ From the FFT analysis result obtained in ④, determine the power spectrum of the frequency band where each response characteristic value can be calculated.

 From the power spectrum calculated in ⑥ ⑤, determine the response characteristics suitable for the fill site.

A method of calculating the response characteristic suitable for the fill site from the power spectrum shown in FIG. 15 is as follows.

In Figure 15, A1 (spectral value at the frequency corresponding to 1/2 times the vibration frequency), A2 (spectral value at the vibration frequency), A3 (spectral value at the frequency corresponding to 3/2 times the vibration frequency) , A4 (spectral value at frequencies corresponding to twice the vibration frequency), A5 (spectral value at frequencies corresponding to 5/2 times the vibration frequency), A6 (frequency at frequency corresponding to three times the vibration frequency) Measure the spectral values) and substitute them into the equation for calculating the response characteristics (see equations (1), (2) and (3)) to obtain the response characteristics.

A1 A2 A3 A4 A5 A6 CCV PWIR CMV Remarks Standard yarn 0.07 0.85 0.25 0.4 0.005 0.001 0.789 0.553 0.471 Material 0.25 0.8 0.2 0.5 0.05 0.02 0.971 0.646 0.625 Crushed stone 0.01 0.02 0.006 0.008 0.002 0 0.867 0.456 0.400

If you draw a graph of relative density or compaction frequency in the same way as above, you can get the result as shown in Fig. 16. Based on this graph, the standard value of compaction management of fill is calculated. For example, based on 60% relative density. For compaction management, the compaction frequency should be 4 times, and the response characteristic value at this time is 140 when calculated by CCV, 85 when calculated by PWIR, and 90 when calculated by CMV. In the field, these characteristic values are calculated and pledged to be above this standard.

1 is a graph showing the change in the vibration acceleration according to the increase in the number of compaction of the fill material,

2 is a graph showing an operation processing method using a band pass filter;

3 is a conceptual diagram of a method for measuring compaction characteristics of a fill material according to the present invention;

4 is a real picture of the experimental equipment,

5 is a photograph showing the attachment state of the membrane,

6 is a photograph showing an installation state of the underground accelerometer for each depth;

Figure 7 is a photograph showing a compaction plate installation state,

8 is a photograph showing the compacting operation,

9 is a photograph showing a state of ground height measurement,

10 is a measurement photograph of the vibration reaching speed;

11 is a photograph showing a state of performing a vibration test,

12 is a graph of the first time measurement state,

13 is a graph for calculating correlation between relative density and wave propagation speed,

14 is a graph of filtering and FFT analysis of an acceleration response;

15 is a graph illustrating a state in which a power spectrum of a specific frequency is determined from an FFT analysis result;

Fig. 16 is a graph for calculating the compaction management reference value from the relationship between the relative density or compaction frequency and the compaction degree (response characteristic value) calculated from the power spectrum results.

Claims (4)

Vibration test is performed to investigate the correlation of the ground response response to the relative density of the fill material. Measuring an oscillation speed by installing accelerometers at predetermined depths of the backing plate and the fill material; Analyzing the wave propagation speed measured in the above step, determining the propagation speed of the wave that can infer the distribution of compaction according to the compaction depth and the relative density of the soil, Determining a response characteristic value for obtaining a relative density; Compaction characteristics indoor measurement method of the fill material, characterized in that consisting of. The method according to claim 1, The measurement of the wave propagation rate ① Measure the total depth and the distance between each accelerometer of the filled soil compacted in the container, ② apply striking vibration to the board, ③ Measure the accelerating time of each accelerometer at the time of the vibration price, ④ Calculate the propagation speed of waves between each acceleration by dividing the distance between each acceleration measured in ① by the start time measured in each accelerometer measured in ③. ⑤ Calculate the correlation between the relative density and the propagation speed of the wave by landfill, 6. The method for measuring compaction characteristics of fill material, characterized in that the wave transmission speed corresponding to the management relative density of target soil is determined based on the correlation calculated in ⑥ ⑤. The method according to claim 1, The determination of the response characteristic value ① Obtain the relative density by measuring the total depth of the embankment soil compacted in the container. ② Provide excitation force for each frequency to fill ground through loading board, ③ Measure the response to the excitation force in each accelerometer, ④ After filtering to remove noise from each accelerometer's response measured in ③, FFT analysis is performed. ⑤ Determine the power spectrum of the frequency band where each response characteristic value can be calculated from the FFT analysis result obtained in ④.  A method for measuring compaction characteristics of fill material, characterized in that the response characteristic value suitable for the fill site is determined from the power spectrum calculated in ⑥ ⑤. Apparatus used in the measuring method of claim 1, The compaction characteristics of the fill material comprising a container filled with the fill material, and a plurality of accelerometers installed on the lower plate of the vibration tester for hitting the fill material and the predetermined depth of the fill material filled in the container. Measuring device.

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