Development of a Time Domain Reflectometry Sensor for Cone Penetration Testing

Mike Amos, Lee Barbour, Dyan Pratt, Bing Si

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Laboratory and Field Testing

ABSTRACT: pment of a Time Domain Reflectometry Sensor for Cone Penetration Testing Mike Amos, Lee Barbour & Dyan Pratt Department of Civil, Environmental and Geological Engineering University of Saskatchewan, Saskatoon, Saskatchewan, Canada Bing Si Department of Soil Science University of Saskatchewan, Saskatoon, Saskatchewan, Canada ABSTRACT A preliminary laboratory program has been undertaken on a series of prototype designs for a time domain reflectometry (TDR) probe that could be adapted for cone penetration testing (CPT). The goal of this work is to design a TDR-CPT probe which could be used to map water content profiles across reclaimed mine closure landforms. The probe will be inserted to depths of at least 10-20 m, and will need to mitigate the effects of high salinity, as well as withstand the high levels of wear and friction encountered during insertion. Testing focused primarily on oil sands mine tailings sands with elevated salinity and a range of water contents. The best performance was obtained for a probe with three TDR rods partially embedded, and one enclosed, in acetyl resin. This prototype design will now be evaluated under more realistic field and operational conditions associated with CPT operation. RÉSUMÉ Un programme de laboratoire préliminaire a été entrepris sur une série de prototypes pour une sonde à réflectométrie de domaine temporel (TDR) qui pourrait être adaptée pour les tests de pénétromètres coniques. Le but de ce travail est de concevoir une sonde TDR-CPT qui pourrait être utilisée pour cartographier les profils de teneur en eau à travers les terres récupéré ont surtout visé les résidus des sables pétrolifères ayant un niveau de salinité élevé et enfoncée, et une enfermée, en résine Acétyle. Ce prototype sera maintenant évalué en conditions plus réalistes et des 1 INTRODUCTION Fundamental to the evaluation of the soil-atmosphere-vegetation-transfer (SVAT) of water within reclaimed mine closure landscapes is the measurement of the near surface water balance and consequently the associated changes in water volume within the soil profile. Quantifying the volume of water held within a soil requires the measurement of the gravimetric water content and dry density within the profile or the direct measurement of the volumetric water content. The first method is accurate but requires an undisturbed soil sample which is expensive and time consuming (Noborio 2001). In situ methods for the direct measurement of volumetric water content are available; however, these methods also have drawbacks. Two commonly used electrically-based systems, capacitance probes and frequency domain reflectometry (FDR), require time-consuming site-specific calibrations in new soils. Neutron tubes do not require calibrations, but require access tubes to be installed, and are time-consuming to obtain readings. Special training and licensing are also required due to its reliance on radiation sources for the measurements. Time domain reflectometry (TDR), however, is rapid, does not emit harmful radiation, and does not generally require site-specific calibration; as a result, it is a desirable in situ tool for determining volumetric water content (Noborio 2001, Jones et al. 2002, Strangeways 2003). The purpose of this research project is to develop a TDR probe that can be adapted for routine use in cone penetration testing (CPT). The objective of this development would be to obtain spatially distributed water content profiles to depths of 10 to 20 m within oil sands mine waste, although the same probe could be used in natural landforms. Challenges associated with these mine waste soils include elevated salinity levels, along with issues of wear and friction encountered during probe insertion. A TDR-CPT logging tool could rapidly characterize stored water volumes across mine closure landscapes, and when combined with existing resistivity and isotope sampling tools help to track the volume of recent meteoric water entering these landscapes following closure. This paper discusses the laboratory screening process that was followed in selecting and developing a prototype TDR probe that could achieve the research goal. Refinements of the selected prototype will be made to proceed to field testing in the next phase of the research project, with the intent of adapting it for routine CPT use.

RÉSUMÉ: evelopment of a Time Domain Reflectometry Sensor for Cone Penetration Testing Mike Amos, Lee Barbour & Dyan Pratt Department of Civil, Environmental and Geological Engineering

Access this article:
Canadian Geotechnical Society members can access to this article, along with all other Canadian Geotechnical Conference proceedings, in the Member Area. Conference proceedings are also available in many libraries.

Cite this article:
Mike Amos; Lee Barbour; Dyan Pratt; Bing Si (2014) Development of a Time Domain Reflectometry Sensor for Cone Penetration Testing in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper181,author = Mike Amos; Lee Barbour; Dyan Pratt; Bing Si,title = Development of a Time Domain Reflectometry Sensor for Cone Penetration Testing,year = 2014}