Abstract:

To investigate the influence of pre-existing fissures on the settlement and deformation behavior of high-fill compacted loess foundations, geotechnical centrifuge model tests were conducted for a flat-terrain high-fill engineering scenario. Two foundation models, an intact model and a fissured model, were designed and comparatively examined during the loading process with respect to deformation development and failure characteristics. The results show that the failure mode is transformed by fissures from a single tensile-cracking pattern to a combined tensile-shear failure, in which fissure propagation, a branched crack network, and stepped surface dislocation are formed. The overall stiffness and stability of the foundation are reduced by fissures; settlement is initiated earlier than in the intact model, the total settlement is increased, and the settlement distribution is more non-uniform. A V-shaped concentration pattern of surface settlement is exhibited and is markedly intensified with increasing load. In addition, a distinct stratified effect on stress distribution is induced by the fissure structure: vertical stress is concentrated in the upper layer, weakened in the middle layer, and only slightly affected in the lower layer, whereas horizontal stress is concentrated near the bottom and released in the middle and upper layers. These changes reconstruct stress-transfer paths and increase the risk of local instability.

Key words: centrifuge model test, fissured foundation, loess foundation, settlement deformation, foundation settlement, failure characteristics