Dynamic Response of a Model Levee on Sherman Island Peat: A Curated Data Set

Abstract

A model levee resting atop soft compressible peaty organic soil in the Sacramento/San Joaquin Delta was shaken by forced vibration to study the seismic deformation potential of the underlying peat and measure dynamic levee-peat interaction. Forced vibration testing occurred over a frequency range of 0 to 5 Hz and produced force amplitudes applied to the embankment crest that induced elastic to nonlinear levee-foundation responses. Available data include acceleration records from sensors mounted on the model levee and on the ground surface near the model levee, and acceleration and pore pressure measurements from sensors embedded in the underlying peat. A remote data acquisition system measured settlements and pore pressures over a span of more than a year, encompassing time before and after the dynamic testing. Small pore pressures were generated in the peat during testing although embankment settlements from cyclic loading were small.

Weakening mechanisms imposed on California’s levees under multiyear extreme drought

“…As noted, many of the Delta levees are founded on peaty soils (Reinert et al 2014). A significant amount of carbon around the globe is stored in organic soils (e.g., peat) and changes in soil temperature and moisture due to the current warming trend significantly influence SOC dynamics.…”

“…Land subsidence in the Delta is primarily caused by aerobic microbial oxidation of SOC, coupled with sea level rise, and compaction of organic soils resulting from groundwater extraction and agricultural practice (Mount and Twiss 2005;Brooks et al 2012;Reinert et al 2014). In fact, microbial oxidation of SOC accounts for approximately 75 % of the elevation loss due to peat subsidence (Mount and Twiss 2005).…”

“…Levees constructed in the Delta are founded on thick layers of peat and the unique macro-structure of peat poses a critical challenge in evaluating subsidence (Reinert et al 2014;Cappa et al 2015). Progressive land subsidence can directly threaten levee structures by exacerbating the risks of water rising over the tops of levees (referred to as overtopping).…”

“…Input soil properties were selected based on values reported afterReinert et al (2014) for a California levee sand. The SSCCs were computed here for a depth (z) of 9 m, which is a practical height for the body of an earthen leveeDesiccation cracks (enhanced water flow) Volume change and soil-strength reduction (soil moisture and temperature dependent) Hydraulic boundary condition (varies in time)Soil-strength reduction (soil moisture and temperature dependent) Conceptual model of thermo-hydro-mechanical weakening mechanisms imposed on levees during extreme drought conditions (afterVahedifard et al 2016a) …”

“…Input soil properties were selected based on values reported afterReinert et al (2014) andLu et al (2009) for a California levee sand and analogous sandy material, respectively…”