Interpretation of Windows Program for Data-Base Backcalculations with Deflection Indices

• Main Authors: JIUNN-KAI CHIOU, 邱俊凱
• Other Authors: Der-Wen Chang
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/25641633502864552925

碩士 === 淡江大學 === 土木工程學系 === 87 === The study uses the Green''s flexibility influence functions to simulate the pavement response. Based on previous research efforts (Shih,1998), a data-base backcalculation program IDBAC is extended for versatile applications with more efficient searching schemes. Accordingly, the deflection data bases for the steady-state and impulsive dynamic deflection tests are established. The effects of the layer thickness and the depth to bedrock as well as the pre- and post- corrections of the asphalt modulus due to temperature variations are analysed. Comparative study is conducted for backcalculations on the local measurements of the Road Rater and FWD tests. The results of this study indicate that the pavement response will be amplified dynamically for a site where bedrock depth is less than 5 m, and the static deflections will be higher than the dynamic ones visa versa. The bedrock effects are typically significant only when the bedrock is near to the ground surface (5m). The static backcalculation will not ensure good backcalculations. Program IDBAC can be properly used if the bedrock depth exceeds 5 m, otherwise iterative programs UTAM or DBFWD should be proceeded. The backcalculated modulus of the subgrade soil is higher than it''s designed value, and both type backcalculation results are found agreeable. In the sensitivity study on the deflections of the steady-state and the impulse tests, changing thickness of the surface layer has the largest effects. To validate the iterative program DBFWD, backcalculations are conducted on FWD deflections collected overseas. With proper control of the deflection history, the bedrock depth can be estimated from empirical formulations. It is found that program DBFWD can provide reasonable backcalculation results for cases where bedrock depth is larger than 79 cm.