Abstract
Abstract Intelligent Compaction (IC) of subgrade soil has been proposed to continuously monitor the stiffness of subgrade during its compaction. Modern IC rollers are vibratory compactors equipped with (1) an onboard measuring system capable of estimating the stiffness of the pavement material being compacted, (2) Global Positioning System (GPS) sensor to precisely locate the roller, and (3) an integrated mapping and reporting system. Using IC, the roller operator is able to evaluate the entire subgrade and address deficiencies encountered during compaction. Continuous monitoring of quality during construction can help build better quality and long-lasting pavements. However, most of the commercially available IC rollers report stiffness in terms of Original Equipment Manufacturer (OEM) specified indicator, known as Intelligent Compaction Measurement Value (ICMV). Although useful, additional tests are required to establish the correlation between these ICMV values and the resilient modulus of subgrade (M r ). Since the mechanistic design of the pavement is performed using M r , it is important to know if the design M r is achieved on the entire subgrade during compaction. This paper presents a systematic procedure for monitoring the level of compaction of subgrade in real time using intelligent compaction (IC). Specifically, the Intelligent Compaction Analyzer (ICA) developed at the University of Oklahoma was used for estimating the modulus of the subgrade. Results from two demonstration studies show that the ICA is able to estimate subgrade modulus with an accuracy that is acceptable for quality control activities during the construction of pavements.
Highlights
In the mechanistic-empirical design of asphalt pavements, the strength of the subgrade is represented in terms of resilient modulus (Mr)
The results of two case studies reported in this paper show that the Intelligent Compaction Analyzer (ICA) can estimate the modulus of the subgrade in real time during the compaction
The ICA-estimated moduli were validated by comparing them with the Falling Weight Deflectometer (FWD) back-calculated subgrade moduli and laboratory resilient moduli in two different field studies
Summary
In the mechanistic-empirical design of asphalt pavements, the strength of the subgrade is represented in terms of resilient modulus (Mr). Dynamic Cone Penetration (DCP) [3,4,5], Falling Weight Deflectometer (FWD) [6, 7], or Light Weight Deflectometer (LWD) [3] tests are performed to assess the stiffness (function of modulus, compacted layer thickness, and Poisson’s ratio) of the subgrade during construction These tests do not provide a direct measurement of the resilient modulus and are not commonly performed due to cost and time constraints. Since FWD tests are not always feasible to carry out, in the second study, the accuracy of the estimated MICA values was validated by comparing MICA values with the corresponding Mr values estimated from regression models developed based on the laboratory Mr (Mr-reg) test results These two studies demonstrate that the ICA is able to estimate the subgrade modulus in real time with an accuracy suitable for the quality control measures during the construction of subgrades
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