Wet and gassy zones in a municipal landfill from P- and S-wave velocity fields

Konstantaki, L.A.; Ghose, Ranajit; Draganov, Deyan; Heimovaara, T.J.

doi:10.1190/geo2015-0581.1

Cited by 13 publications

(11 citation statements)

References 36 publications

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“…However, it can be seen in Fig. 14 that it is in agreement with the values derived by Konstantaki et al (2016) from MASW (Rayleigh and Love waves) and S-wave seismic reflection data using the same relationship (Fig. 14).…”

Section: Unit Weightsupporting

confidence: 81%

Evaluating elastic wave velocities in Brazilian municipal solid waste

et al. 2019

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The sanitary landfills in Brazil are, generally, characterized by their high organic material content (around 60%), presence of different types of mixed wastes, and low compaction energy, which differentiates them from the landfills of developed and high-income countries. To prevent environmental and slope stability risks, it is crucial to understand the behavior of such landfills and the changes in their physical properties over time. The compression wave velocity (V p ) and shear wave velocity (V s ) are important parameters to subsidize the mechanical characterization of sanitary landfills, using which can be derived the dynamic elastic properties of municipal solid waste (MSW) for stability analysis. Using the geophysical methods of seismic refraction, active and passive multichannel analysis of surface waves, and crosshole test, it was obtained the values of Vp and Vs by employing an experimental cell and a lysimeter filled with MSW in the City of Campinas, São Paulo State, Brazil. The results obtained from the crosshole test showed that Vp ranged from 217 to 252 m/s and Vs ranged from 86 to 89 m/s. These low values can be attributed to the high content of organic material, low compaction energy, and climatic conditions such as high pluviometry index and high temperatures that together lead to changes in the pore fluid saturation, effective stress, and pore pressure. These values are indicative of the lower limit of the corresponding velocities reported in most literature; however, they are in accordance with the values reported for landfills located in countries with similar socioeconomic and climatic conditions.

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Section: Unit Weightsupporting

confidence: 81%

Evaluating elastic wave velocities in Brazilian municipal solid waste

et al. 2019

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“…Similar velocities were obtained for landfills in Switzerland (300-800 m/s; Lanz et al 1998;De Iaco et al 2003) and USA (350-550 m/s; Carpenter et al 2013). Konstantaki et al (2016) obtained particularly low P-wave velocities (150-200 m/s) in a landfill in the Netherlands, and attributed these to the presence of biogas (which could be the case at Hvalsø).…”

Section: D Seismic Refraction Surveyssupporting

confidence: 75%

Geophysics for urban mining and the first surveys in Denmark: rationale, field activity and preliminary results

et al. 2020

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Geophysical methods have been widely used in recent decades to investigate and monitor landfill sites for environmental purposes. With the advent of the circular economy, waste contained in old landfills may be considered a resource that can be developed. Since the content of old landfills is largely unknown, the occurrence and quantity of valuable materials must be investigated before embarking on any development activity. Two landfills on Sjælland, Denmark (located at Hvalsø and Avedøre) were selected for a pilot study to characterise their content. At both locations, a set of geophysical surveys is underway. Here, we present the data obtained from magnetic and 2D seismic refraction surveys. Magnetic data show various anomalies that can be interpreted as caused by iron-rich waste. At both sites, the landfill material results in generally low P-wave velocity (<400 m/s), lower than those obtained for Quaternary sediments at Avedøre. The seismic velocities appear to increase in the presence of metals or by compaction with depth (>550 m/s). We propose that seismic refraction can thus define the bottom of the landfill and possibly its internal structure, especially when combined with other methods.

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“…For small additions of gas, v P drops significantly (Anderson and Hampton 1980), due mostly to the effect of gas on the bulk compressibility of the sediment volume. Velocity values of 170-200 m/s are calculated with the addition of gas, consistent with Anderson and Hampton (1980) for gas saturations greater than 1% and Konstantaki et al (2016) and Angioni et al (2003) at shallow onshore sites. Of course, higher velocities than this are plausible, attributable to local velocity averaging in gassy and non-gassy sediment and/or a prevalence of smaller-sized bubbles in the total gas volume (Wilkens and Richardson 1998).…”

Section: Model Inputssupporting

confidence: 56%

“…Velocity values of 170–200 m/s are calculated with the addition of gas, consistent with Anderson and Hampton () for gas saturations greater than 1% and Konstantaki et al . () and Angioni et al . () at shallow onshore sites.…”

Section: Methodsmentioning

confidence: 86%

Tuning, interference and false shallow gas signatures in geohazard interpretations: beyond the rule

Barrett

Huws

Booth

et al. 2017

Near Surface Geophysics

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Shallow gas presents a significant geohazard for drilling operations, with implications for costly well deviations and inherent blowout risks. The archetypal seismic signature of shallow gas—a “bright spot”—can be falsely induced by tuning, whereby reflections from closely separated horizons stack and constructively interfere. According to established guidelines, maximum constructive interference is typically expected where horizons are separated by one‐quarter wavelength (λ/4) of the seismic wavelet. Here, we test the circumstances in which false gas signatures can be induced from tuning and the conditions in which the “λ/4” guidelines for interference become problematic. We simulate normal‐incidence seismic data for a variety of reflectivity models, incorporating different contrasts in reflectivity magnitude and polarity. We simulate acoustic impedance by supplying initial geological parameters to Gassmann’s rock physics equations, allowing bulk density and compressional (P‐) wave velocity to vary between 1200–2100 kg/m3 and 1460–1670 m/s, respectively, for non‐gassy sediments and 1160 kg/m3 and 170–200 m/s for gassy sediments. Tuning is considered for a Ricker wavelet source pulse, having both peak frequency and effective bandwidth of 60 Hz. Tuning effects are able to mask a gas pocket, corresponding to a “false negative” signature that represents a significant hazard for drilling operations. Furthermore, the widely adopted λ/4 assumption for constructive interference is not always valid as the brightest seismic responses can appear for thicker (<“λ/2”) and thinner (>“λ/16”) beds, depending upon the stratigraphy. Similar observations are made both qualitatively and quantitatively for real seismic responses, in which reflections from a series of dipping clinoforms interfere with those from an overlying unconformity. We conclude that greater attention should be paid to the interpretation of shallow gas risk; specifically, the effect of reflector geometries should not be overlooked as a means of producing or masking seismic amplitudes that could be indicative of a hazardous gas accumulation.

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Wet and gassy zones in a municipal landfill from P- and S-wave velocity fields

Cited by 13 publications

References 36 publications

Evaluating elastic wave velocities in Brazilian municipal solid waste

Evaluating elastic wave velocities in Brazilian municipal solid waste

Geophysics for urban mining and the first surveys in Denmark: rationale, field activity and preliminary results

Tuning, interference and false shallow gas signatures in geohazard interpretations: beyond the rule

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