상시 미동 측정에 의한 다짐 측정

상시 미동 측정에 의한 다짐 측정

Application of the passive seismic Horizontal-to-Vertical Spectral Ratio (HVSR) technique for embankment integrity monitoring

 

 

영신컨설턴트 (02) 529 8803 2018.7

 

도로 다짐관리는 비용과 시간이 많이 소요되는 정적 평판재하시험, 평판재하시험의 문제를 보완 동적 평판재하시험, 동적 콘 시험으로 한다. 상시미동에 의한 다짐관리는 가장 가벼워 편리한 장점이 있고 직경 큰 (1m)돌 층도 평가할 수 있다.

정적평판재하시험	동적 평판 재하시험	상시미동 측정

 

폐기물 매립장의 제방 H/V 측정에 의한 다짐 측정

The HVSR technique is a passive seismic method introduced by Nakamura (1989) that measures ambient seismic noise. The ambient seismic noise, or micro tremors, are produced primarily by wind and ocean waves culminating in what is proposed to be shear waves near the surface (Yamanaka et al, 1994).

 

Anthropogenic sources can also add to wave propagation, typically at higher frequencies than natural sources. 인위적인 파는 자연주파수보다 크다.

 

The HVSR method empirically defines that the constructive interference of waves within a layer will produce amplified horizontal oscillations relative to vertical oscillations and that the ratio of the horizontal and vertical components will produce a peak frequency related to the resonant frequency of the layer (Ali, 2013, Moro, 2015). In an ideal two-layer Earth model, this peak fundamental frequency can be used to estimate the shear wave velocity (Vs, in m/s) of the top layer if both layers display a high enough impedance contrast (Mucciarelli, 2001, Di Stefano et al, 2014). 한 층에서 수직(V)보다 수평(H)의 증폭이 크다

 

측정현장

시험용 제방

상시미동 측정

Ambient seismic tremor was recorded on top of embankments using a portable three-component seismometer. Traverses were collected wherever possible using a nominal station spacing of 50 m. 제방의 상단에서 50m 간격으로 측정

 

At each station, data was recorded for a duration of eight to ten minutes once good ground coupling and levelling was achieved in an area free of debris or rubble. A cover was placed over the unit to protect from the wind, and a 50 m exclusion zone was maintained during recording to avoid interference from the operator’s movements. 측정시간 8-10분

 

Data quality assurance and control, standard HVSR processing and peak resonance frequency (f0, in Hz) selection was undertaken in a proprietary software (Figure 3) following a workflow similar to the one described in Owers et al (2016).

 

Embankment Vs is then estimated following the empirical equation from Nakamura (2000);

 

Vs = 4 * h * f0,

 

where h is the known embankment thickness (in m) at the station location.

  

A summary of average Vs results collected over 69 passive seismic stations across five sites (embankments and tailings) is presented.

 

Figure : Passive seismic stations (green) over aerial photography.

HVSR results along selected traverses are displayed as vertical stacked spectrums with frequency on the ordinate decreasing down and station fiducial on the abscissa. 그래프의 가로 측정위치 세로 주파수에 대한 H/V

 

Table : Average Vs and associated standard deviation estimated from HVSR

surveying over various structure types. 매립장 위치별 상시미동에 의한 전단파 속도 Vs

Figure : HVSR average Vs values (516 m/s in 2015 and 523 m/s in 2017).

시간경과에 대한 전단파 속도

 

 

Figure : Vs and density laboratory testing results (a) PCT results for various moisture content, (b) observed linear correlation between density and ln(Vs).

 

standard Proctor Compaction Test (PCT) 함수비 밀도와 전단파 속도