Finite Element Analysis of TDR Cable-Grout-Soil Mass Interaction During Localized Shearing

James Tanner Blackburn

doi:https://doi.org/10.21985/N2147V

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Finite Element Analysis of TDR Cable-Grout-Soil Mass Interaction During Localized Shearing

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This thesis combines field and laboratory measurements with three dimensional (3D) finite element analysis (FEM) to demonstrate the use of Time Domain Reflectometry (TDR) cable-grout composites to measure localized shearing in soft soil. Past field installations of TDR cable-grout composites in rock have lead to its widespread use in the mining industry (Dowding and Huang, 1994). Lack of well instrumented installations in soil as well as differences in failure mechanisms and relative stiffnesses of rock and soil have inhibited development of optimal cable-grout composites for soil. A deforming landfill on soft clay provided an opportunity to field test the response of two different TDR cable-grout composites in soft soil. TDR signal reflections from the more compliant of the cable-grout composites in the field test shows that TDR cable-grout systems can be devised to respond to localized shearing in soil. However, additional analysis of the interaction between the cable, grout, and soil mass is required for design of TDR cable-grout composites employed in soft soils. Three dimensional (3D) finite element modeling (FEM) is employed to leverage field and laboratory measurements to analyze the interaction of a wide range of cablegrout inclusions and surrounding soil masses. Necessary model properties of cable, grout, and cable-grout interfaces were first back-calculated via 3D FEM from laboratory measurements of cable and cable-grout composite response to shearing. These backcalculated properties were then employed to extend the modeling to include the full interaction of cable, grout, and soil-mass. This complete model was then exercised to 1 investigate a suite of cables, grouts, and soils with variable strengths and stiffnesses to establish an optimum cable-grout composite design for a given soil. Analysis of TDR cable-grout-soil interaction is presented in the following order: 1) discussion of field case study, 2) comparison of laboratory results of shearing of individual cables and cable-grout composites with three dimensional finite element model results, and 3) employment of three dimensional finite element models to analyze cablegrout-soil interaction of TDR composites placed in soft to medium soils.

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