Characterization of a heterogeneous landfill using seismic and electrical resistivity data

Abstract

Understanding the processes occurring inside a landfill is important for improving the treatment of landfills. Irrigation and recirculation of leachate are widely used in landfill treatments. Increasing the efficiency of such treatments requires a detailed understanding of the flow inside the landfill. The flow depends largely on the heterogeneous distribution of density. It is, therefore, of great practical interest to determine the density distribution affecting the flow paths inside a landfill. Studies in the past have characterized landfill sites but have not led to high-resolution, detailed quantitative results. We performed an S-wave reflection survey, multichannel analysis of surface waves (MASW), and electrical resistivity survey to investigate the possibility of delineating the heterogeneity distribution in the body of a landfill. We found that the high-resolution S-wave reflection method offers the desired resolution. However, in the case of a very heterogeneous landfill and a high noise level, the processing of high-resolution, shallow reflection data required special care. In comparison, MASW gave the general trend of the changes inside the landfill, whereas the electrical resistivity (ER) survey provides useful clues for interpretation of seismic reflection data. We found that it is possible to localize fine-scale heterogeneities in the landfill using the S-wave reflection method using a high-frequency vibratory source. Using empirical relations specific to landfill sites, we then estimated the density distribution inside the landfill, along with the associated uncertainty considering different methods. The final interpretation was guided by supplementary information provided by MASW and ER tomography.

Use of Seismic Interferometry to Improve the Imaging of a Heterogeneous Landfill

“…The 48 horizontal geophones that we planted had a 0.5 m spacing and they were kept fixed. The shot spacing was 1 m. Further details regarding the acquisition parameters can be found in Konstantaki et al (2015). Figure 1 shows the data acquisition geometry.…”

“…Surface waves were a challenge in the processing of the CRSS data (Konstantaki et al 2015). Here, we attempt to remove the surface-wave energy using SI.…”

“…We now apply SI to conventional reflection seismic survey (CRSS) data obtained on a landfill and investigate the advantages of SI. Konstantaki et al (2015) propose a processing procedure for the CRSS data from a landfill and remark on the difficulty of interpreting near-surface reflections due to the dominant presence of surface waves. Here, we also investigate the removal of surface waves using SI for landfill application.…”

“…Figures 2a,c,e depict the raw data, whereas Figure 2b,d,f the processed data for the three cases. The greyshaded areas show interpreted reflections, the red and green hyperbolas are interpreted scattering events: red are scattering events interpreted in the CRSS shot gather (Konstantaki et al 2015), whereas green are interpreted in the SI shot gather. Comparing Figure 2b and 2d we observe that scattering events 1,2,5,6 are present in both results.…”

“…To obtain a final virtual-shot gather we choose positive, negative, or a summation of positive and negative times according to the specific source-received positions. (g) Finally, we process the SI data in a way similar to the CRSS data (Konstantaki et al 2015). All stacked sections have a post-stack bandpass filter of 10-35-95-110 Hz applied.…”