01624787

Component

Resilient modulus (M sub R) of subgrade soil is one of the critical parameters in mechanistic-empirical pavement design. At present, the M sub R correlation exists between falling weight deflectometer (FWD) and dynamic cone penetrometer (DCP) in India. Estimation of resilient moduli on modified subgrade soil in laboratory test is a complex, cumbersome and time-consuming process. There is a lack of correlation between DCP value and backcalculated layer moduli using lightweight deflectometer (LWD) with radial geophone spacing 300 mm (12 in.) and 500 mm (24 in.) on modified subgrade soil. The main objective of this paper is to develop an empirical correlation between DCP (mm/blow) and LWD backcalculation (MPa) for in-situ applications. For this study, LWD and DCP tests were conducted during construction of a low volume road in Gujarat state, India. The natural soil was modified using liquid nanomaterials (Terrasil and Zycobond). Additionally, Portland Pozzolana Cement (PPC) was added to improve the bearing strength/resilient moduli of soil. Nondestructive LWD is gaining importance in pavement construction to determine quick resilient moduli of compacted subgrade layers. The computer program LWDmod supplied by Dynatest was used to backcalculate the layer moduli from LWD test data. Good correlation was observed between backcalculated layer moduli (MPa) and DCP (mm/blow) with R² of 88.21%. A cyclic triaxial test result shows approximately similar results with LWDmod backcalculated results using radial geophones. Backcalculated layer moduli closely matched with laboratory results at similar stress levels generated by the LWD in the field. Collected Shelby soil samples were tested in the laboratory under cyclic triaxial test. The ratio of backcalculated results to the M sub R laboratory values is 0.93 and 0.96 close to the unity. This result would be very useful to determination of quick in-situ resilient moduli using LWD in quality control for increasing the pace of road construction activities in India.

This paper was sponsored by TRB committee AFP30 Standing Committee on Soil and Rock Properties. Alternate title: A Correlation Between Lightweight Deflectometer Backcalculation and Dynamic Cone Penetrometer Values of Modified Subgrade Soil.

01618707

17-04169

English

15p

2017

Transportation Research Board 96th Annual Meeting

Digital/other

Figures; References; Tables

Backcalculation; Correlation analysis; Falling weight deflectometers; Low volume roads; Mechanistic-empirical pavement design; Modulus of resilience; Quality control; Road construction; Subgrade (Pavements)

Dynamic Cone Penetrometer; LWDmod (Computer program)

Lightweight deflectometers

Gujarat (India); India

Design; Highways; Pavements

Transportation Research Board Annual Meeting 2017 Paper #17-04169

TRIS, TRB, ATRI

Dec 8 2016 11:35AM