Study On The Stability Of Widening Subgrade And The Additional Stress Of Pavement Structure Layer Under The Condition Of Differential Settlement

It becomes more and more prominent in highway reconstruction and expansion projectsthat differential settlement of the subgrade caused stress and inhomogeneous deformation onpavement structure of widened roads. This dissertation adopted various methods of full-scalemodel tests, field tests, laboratory tests and finite element model to simulate, and analyzed thestability of widening embankment and the additional stress within pavement structure layers.The major findings are：1、Commonly, the destruction on widened subgrade is due to instability and unevensettlement of the roadbed. Through our analysis, the major failure mechanisms are theuncoordinated deformation between new and old subgrades the bad combination of the newand old embankments, and the strength and stiffness differences between new and oldsubgrades.2、We examined the widening embankment stability using the strength reduction finiteelement analysis versus the calculated embankment stability safety factors with limitequilibrium. The most dangerous slip surface of the widened embankment was a sliding arcbelt with certain width, unlike the regular circular slip surface of subgrade.3、We studied the effect of differential settlement on the strain characteristics of thepavement structure layers using the widening roadbed full-scale model tests. We found thatwhen the roadbed differential settlement values reached a certain threshold, the pavementstructure strain began to increase dramatically and plastic strain damage began to appear inthe pavement structure layer.