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Ground improvement via jet grouting is commonly used to strengthen weak ground and/or create hydraulic barriers. Delivering soilcrete columns with tightly controlled and known diameters is critical to performance; however, techniques to assess jet grout geometry during construction are lacking. This paper reports the results of a study on electrical resistivity imaging of soilcrete by investigating the effects of electrode configuration and electrical protocol type on laboratory scale soilcrete columns constructed in a tank filled with sand. Experimental results are verified via numerical modeling and the model is used to analyze the changes in soilcrete resistivity that result from geometric variation. The results of this study indicate that resistivity imaging with direct contact electrodes can estimate the diameter of laboratory scale jet grout columns to within ±5% of the as-built column diameter. A relationship between electrode spacing and column diameter is identified and quantified to more readily extend the diameter estimation approach developed in this research to field-scale geometries. Additionally, time lapse monitoring of soilcrete resistivity was performed over the course of curing. Results indicate that resistivity imaging should be performed as early as possible to obtain the greatest resistivity contrast between the soilcrete and in situ soil. [ABSTRACT FROM AUTHOR]

Stabilization via lime and/or cement is commonly used to improve poor subgrade soil. The key design parameters for lime stabilized soils and lime-cement stabilized soils (LSS/L-CSS) are strength and stiffness, the growth of which are dependent on both time and temperature. It is generally understood that increased curing temperature will result in increased LSS/L-CSS strength/stiffness; however, there is no quantitative framework for predicting this behavior. This paper proposes a modulus maturity function for LSS/ L-CSS that estimates low-strain modulus as a function of the curing duration and the average curing temperature over that duration. To develop the maturity function, nondestructive seismic modulus tests were performed on cylinders cured at varying temperature regimes from three LSS/L-CSS construction sites. Variations in curing behavior were compared within and across sites and least-squares regression analysis was performed to assess the functional behavior of the data. Results indicate that seismic modulus growth in LSS/L-CSS is nonlinear in both time and temperature and should be characterized via a maturity function. [ABSTRACT FROM AUTHOR]

Given the schedule pressure of lime-stabilized soil construction, many agencies specify the use of elevated temperature (e.g., 41°C), shorter duration (e.g., 5-7 days) accelerated specimen curing for unconfined compressive strength () testing and acceptance as a proxy for of specimens normally cured under 28-day 23°C conditions. Moreover, lime and highway transportation industry associations prescribe a unique accelerated curing regime for all lime-stabilized soils (7-day, 41°C). This paper presents the results from a laboratory investigation of stress-strain-strength development of four lime-stabilized soils under 2-8 day 41°C accelerated curing and the 0-28 day 23°C normal curing regime. Specimens cured at 41°C reached values equivalent to 28-day 23°C after 1.8-5.9 days. Accordingly, 7-day 41°C curing overestimates 28-day normal cure by 13-260%. When combined with a detailed analysis of data available in the literature, the results illustrate that the prescription of a unique equivalent accelerated curing regime is oversimplified and can lead to significant overestimation of design . [ABSTRACT FROM AUTHOR]

This technical note assesses the widely accepted Thompson's equation used to approximate design resilient modulus () for lime-stabilized soils from the results of unconfined compressive strength () testing. There is limited evidence in the literature to support Thompson's equation relating and for lime-stabilized soils, and other studies have suggested that the relationship provides an excessively conservative approximation for design , specifically above . Laboratory and testing was performed on multiple specimens of three lime-stabilized soils. These data reveal that Thompson's equation provides a lower-bound estimate of from and that Little's recommended relationship provides a more reasonable match to the data. This study also illustrated a lack of a clear correlation between and . [ABSTRACT FROM AUTHOR]

Given the schedule pressure of lime-stabilized soil construction, many agencies specify the use of elevated temperature (e.g., 41°C), shorter duration (e.g., 5-7 days) accelerated specimen curing for unconfined compressive strength () testing and acceptance as a proxy for of specimens normally cured under 28-day 23°C conditions. Moreover, lime and highway transportation industry associations prescribe a unique accelerated curing regime for all lime-stabilized soils (7-day, 41°C). This paper presents the results from a laboratory investigation of stress-strain-strength development of four lime-stabilized soils under 2-8 day 41°C accelerated curing and the 0-28 day 23°C normal curing regime. Specimens cured at 41°C reached values equivalent to 28-day 23°C after 1.8-5.9 days. Accordingly, 7-day 41°C curing overestimates 28-day normal cure by 13-260%. When combined with a detailed analysis of data available in the literature, the results illustrate that the prescription of a unique equivalent accelerated curing regime is oversimplified and can lead to significant overestimation of design . [ABSTRACT FROM AUTHOR]