Impacts of organic matter and loading methods on one-dimensional compression behavior of calcareous sand

Abstract

To explore the effects of organic matter (OM) and loading methods on compression and particle breakage behaviors of calcareous sand (CS), a set of one-dimensional (1D) compression experiments were completed with two loading methods of constant rate of strain and incremental loading. Particle size distribution (PSD) analysis and three-dimensional (3D) modelling tests were performed to assess particle breakage degree and OM distribution form. Test results demonstrated that there existed an OM content of 25% in which the total vertical strain (TVS) in loading process declined first and then grew after that. While in unloading process, TVS decreased linearly from 16.1% to 4.2% approximately when OM content increased from 0 to 100%. In addition, there existed two loading stress turning points of 800 and 1600 kPa corresponding to vertical strain variation for CS-OM (A) and CS-OM (B) mixtures, respectively. The rebound index of mixtures increased from 0.002 to 0.107 when OM content increased to 100% which was determined collectively by the percentage of PCS and OM. OM can restrain particle breakage of CS to some degree and relative breakage ratio decreased from 0.24 to 0.03. Under the same condition, the relative breakage ratio (0.24) of CS-OM (B) mixtures with IL loading method were larger than that of CS-OM (A) mixtures or CRS loading method. Moreover, SEM and 3D models of CS-OM mixtures suggested that the OM are flocculent and distributed in surface or pores of CS particles.