(1) 여기서, ε p = 영구변형률, A, b = 모델계수 일반적으로 흙재료의 다짐도와 탄성계수는 매우 밀접한 Abstract Formation used as trackbed foundation for providing vertical bearing capacity onto rail foundation are composed of crushed stones usually with certain type of grain size distribution. Permanent deformation in trackbed foundation can be generated by increasing number of load repetition due to train traffic increases, causing track irregularity. In this study, a specially prepared trackbed foundation materials (M-40) used in Korea has been tested using a large repetitive triaxial compression apparatus in order to understand resilient and permanent deformation characteristics of the material. From these test results, resilient and permanent deformation characteristic are analyzed so that a permanent deformation model is developed which can consider number of load repetition N, confining stress (σ 3 ), shear stress ratio(τ/τ f ) and stiffness of the material.

Pipe installation following excavation of pavement and subsoils induces settlements, cracks and bad roughness near utility cut. This study is to use PMT and LDWT in order to evaluate stiffness and/or degree of compaction of sublayers and backfill in utility cut section because no specially designed efforts for evaluating stiffness condition of the substructures below new pavement after pipe installation are offered for the sections. From test results of PMT, comparable stiffness and/or degree of compaction in recompaction process is not obtained comparing to that of the existing sublayers before excavation. It is verified that LDWT comparing to PMT is effective only to get stiffness and/or degree of compaction within limited depth from surface of refill materials, but it is not useful to know stiffness of substructures in full-depth in case of utility cut. A numerical study is performed also for getting information about behavior of utility cut section with changing stiffness of the sublayers.