Method and apparatus for determining stiffness of a roadway

Abstract

An apparatus for the compaction of roadway materials includes a compaction analyzer for calculating stiffness during construction of the roadway. The apparatus generates a dynamic modulus for each layer of a roadway which can be used to calculate the overall effective modulus. A method for determining stiffness includes generating a dynamic modulus for each layer and calculating the overall effective modulus using the modulus of each layer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]Priority is claimed from U.S. Provisional Application Ser. No. 61 / 621,259, entitled “Method of Determining Stiffness” filed Apr. 6, 2012.BACKGROUND OF THE INVENTION[0002]The current disclosure is directed to methods and apparatus for the compaction of roadway materials, and more particularly, to methods and apparatus for calibrating a compaction analyzer, and determining stiffness during construction.[0003]Asphalt is often used as pavement. In the asphalt paving process, various grades of aggregate are used. The aggregate is mixed with asphalt cement (tar) and sand, and heated to approximately 150° C. to 169° C., and a paver lays down the hot asphalt mix and levels the asphalt mix with a series of augers and scrapers. The material as laid is not dense enough due to air voids in the asphalt mix. Therefore, a roller makes a number of passes over the layer of asphalt material, referred to herein as the asphalt mat, driving back and forth, or...

AI Technical Summary

Benefits of technology

[0006]The apparatus disclosed herein comprises a vibratory compactor, or roller, with sensors, and a compaction analyzer associated therewith. The compaction analyzer has a feature extraction module, a neural network module and an analyzer module. The sensors may comprise accelerometers for measuring vibratory response signals of the roller, and the compaction analyzer utilizes the characteristics of the vibratory response signals to generate, in real time, a modulus signal representative of the density of the material being compacted. In addition, the compaction analyzer will generate signals representative of the dynamic modulus of the pavement. A method of compacting a roadway section with a roller having a compaction analyzer operably associated therewith comprises entering initial input parameters into the compaction analyzer and making a plurality of passes with the roller over a layer of a portion of the roadway section. The method may further comprise applying a vibratory energy to the portion of the roadway section with the roller as it moves over the layer of the portion of the roadway section and repeatedly gathering responsive vibration signals of the roller as it moves over the layer portion of the roadway section. Additional steps may comprise generating, with the compaction analyzer, estimated modulus signals representative of estimated dynamic moduli based upon the responsive vibration signals of the roller and the initial input parameters entered into the compaction analyzer and measuring the modulus of the layer of the roadway section at a plurality of locations on the portion of the roadway section. The measured moduli may be compared to the estimated moduli at the plurality of locations to determine the difference between the measured and the estimated moduli. Selected ones of the initial input parameters to the analyzer can then be adjusted based on the difference between the measured moduli and the estimated moduli. The compaction analyzer will generate an adjusted modulus output signal which will more closely approximate an actual modulus of the roadway section than does the estimated modulus signal. The remainder of

Problems solved by technology

The material as laid is not dense enough due to air voids in the asphalt mix.

The process of measuring density of the asphalt mat during the compaction process is cumbersome, time-consuming, and is not indicative of the overall compaction achieved unless measurements are taken at a large number of points distributed in a grid fashion, which is difficult to achieve in the field due to cost considerations alone.

Failure to meet the target density is unacceptable and remedial measures may result in significant cost overruns.

Early dete

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