Abstract

Accurate measurement of soil temperature is essential for the diagnosis of various environmental processes and their impact on ecosystems. Indeed, continuous monitoring of temperature profiles with depth provides valuable understanding of the soil thermal response, which could support studies related to climate change, hydrology, agriculture, and geothermal energy. The paper describes an innovative installation procedure of temperature strings (CS225) to measure the temperature field of an undisturbed soil deposit at different depths in real time. The strings consisted of multiple temperature probes connected in series, placed at specific depths within the soil profile. The CS225 probes require little maintenance and no initial calibration, guaranteeing a high accuracy and resolution of the temperature measurements. The initial field measurements have shown a good performance of the probes, which have been able to detect the gradual decrease of soil temperature and the reduction of oscillations with depth. Further research will include the detailed analysis of the influence of ambient wind speed, solar radiation and soil moisture on the heat transfer from the ground surface to the deeper soil layers, as well as laboratory tests and numerical analysis.

Abstract

Future static settlement of a former aggregate mining quarry site in Irwindale, California is predicted based on the monitoring data and using numerical analyses that consider the total settlement of the deepest portion of the rockfill. The portion of quarry analyzed was backfilled with approximately 61 to 67 meters, has a volume of 2.6 million m3, and covers an area of 114,900 m2. The backfill material ranges from silty sand (SM) to silty gravel (GM) and was compacted to achieve an average relative compaction (RC) of 96%. The deepest fill area is currently being monitored with survey data to predict future 50-year settlement due to secondary compression. Settlement monument data from three different locations has been collected and made available starting from May 2009 up to now. A 3-dimensional model of the rockfill was used to determine an appropriate upper and lower bound of predicted future 50-year settlement from today in 13 stages and scenarios. The modified secondary compression index was estimated along with the modified compression index that was back calculated to match the field monitoring data. We could find good agreement between the field monitoring data and our numerical model when considering total settlement of the rockfill.