Technical Studies


Instantaneous Water Content and Density Determination of Compacted Soils by Multi-physical Data Fusion (2/2)

The quality control of compacted soils relies on measuring the moisture content and dry density of soils during compaction, which determine the strength and hydraulic conductivity of earth dams, road embankment and retaining structures. Inappropriate moisture content or insufficient dry density during construction would cause excessive ground settlement and failure of earth structures. Conventional quality control methods are time consuming and the nuclear method although efficient is potentially hazardous. Due to increased regulatory restrictions and growing concerns over the safety of using a device with a nuclear source, there is an increased effort to find a possible alternative to the nuclear gauge for compaction control. The replacement device must accurately assess the properties of the compacted fill and do so in a timely manner that does not impact construction. Up to date, no single measurement technique is successful in meeting these goals. However, Time Domain Reflectometry (TDR, measuring the electrical property of compacted soils) is ranked as the most potential technique, which may be further complemented by seismic wave velocity or thermal conductivity measurements. The objective of this research is to develop an integrated measurement technique for rapid determination of soil water content and dry density based on fusion of various non-nuclear physical measurements. The behavior of various physical properties in compacted soils is more complicated than just a function of two main factors (dry density and water content). The lack of the knowledge in considering major influencing factors is a main problem. Electrical, thermal, and elastic wave behavior of compacted soils were thoroughly and fundamentally investigated in first year, based on which a multi-physical data fusion approach, Bayesian Inference, was proposed for rapidly determining soil water content and dry density. In the second year, the experimental studies will be finished and a reliable, efficiency, and workable in-situ multi-physical measuring system will be designed and evaluated with field experiments.