Abstract
The adverse effects of climate warming on the built environment in (sub)arctic regions are unprecedented and accelerating. Planning and design of climate-resilient northern infrastructure as well as predicting deterioration of permafrost from climate model simulations require characterizing permafrost sites accurately and efï¬ciently. Here, we propose a novel algorithm for analysis of surface waves to quantitatively estimate the physical and mechanical properties of a permafrost site. We show the existence of two types of Rayleigh waves (R1 and R2; R1 travels relatively faster than R2). The R2 wave velocity is highly sensitive to the physical properties (e.g., unfrozen water content, ice content, and porosity) of permafrost or soil layers while it is less sensitive to their mechanical properties (e.g., shear modulus and bulk modulus). The R1 wave velocity, on the other hand, depends strongly on the soil type and mechanical properties of permafrost or soil layers. In-situ surface wave measurements revealed the experimental dispersion relations of both types of Rayleigh waves from which relevant properties of a permafrost site can be derived by means of our proposed hybrid inverse and multi-phase poromechanical approach. Our study demonstrates the potential of surface wave techniques coupled with our proposed data-processing algorithm to characterize a permafrost site more accurately. Our proposed technique can be used in early detection and warning systems to monitor infrastructure impacted by permafrost-related geohazards, and to detect the presence of layers vulnerable to permafrost carbon feedback and emission of greenhouse gases into the atmosphere.
Highlights
Permafrost is defined as the ground that remains at or below 0◦C for at least two consecutive years
We developed a hybrid inverse and multi-phase poromechanical approach to quantitatively estimate the physical and mechanical properties of a permafrost site
The identification of two distinctive types of Rayleigh waves in the surface wave field measurements in permafrost sites is critical for quantitative characterization of the layers
Summary
Permafrost is defined as the ground that remains at or below 0◦C for at least two consecutive years. Design and construction of structures on permafrost normally follow one of two broad principles which are based on whether the frozen foundation soil in ice-rich permafrost is thaw-stable or thaw-unstable. Several in-situ techniques have been employed to characterize or monitor permafrost conditions Techniques such as remote sensing (Bhuiyan et al, 2020; Witharana et al, 2020; Zhang et al, 2018), and ground penetrating radar (GPR) 40 (Christiansen et al, 2016; Munroe et al, 2007; Williams et al, 2011) have been used to detect ice-wedge formations within the permafrost layers. In the current seismic testing practice, it is commonly 55 considered that the permafrost layer (frozen soil) is associated with a higher shear wave velocity due to the presence of ice in comparison to unfrozen ground. We quantify the physical properties such as ice content, unfrozen water content, and porosity as well as the mechanical properties such as the shear modulus and bulk modulus of permafrost or soil layers. Our results demonstrate the potential of seismic surface wave testing accompanied 70 with our proposed hybrid inverse and poromechanical dispersion model for the assessment and quantitative characterization of permafrost sites
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