Triaxial behavior of cement-stabilized organic matter–disseminated sand

Abstract

Organic matter–disseminated sand (OMDS) is a widely distributed problematic soil in coastal areas of Hainan province, China. Its existence makes the installation of piles difficult and has the risk of insufficient bearing capacity. OMDS is different from other organic soils such as peat in terms of formation, mineral component, organic content, and forms of organic matters. In this study, 20% (w/w) cement together with 7.5% (w/w) lime at a water–cement ratio of 0.45 was mixed with OMDS to improve its mechanical performances. A series of unconsolidated undrained static triaxial test was conducted on the stabilized OMDS to investigate the failure mode, stress–strain relationship, maximum and residue deviator stress, axial strain at failure, and elastic modulus under various confining pressures (0, 200, 300, 400 kPa) and curing time (7d, 14d, 28d). The test results showed that higher confining pressure and longer curing time in general led to higher maximum and residue deviator stress, larger axial strain at failure, and larger secant elastic modulus of cement-stabilized OMDS. The maximum and residue deviator stress of cement-stabilized OMDS increased with curing time and ranged from 500 to 2180 kPa and from 250 to 1800 kPa, respectively. Under elevated confining pressure, maximum deviator stress increased substantially, irrespective of curing time. Secant elastic modulus (E50) increased with confining pressure at these three curing time, from 29 to 42 MPa. Due to the existence of organic matters, the strength of cement-stabilized OMDS was lower than cement-stabilized non-organic sand, regardless of confining pressure and curing time. This study provided new insight into the shear strength behavior of cement-stabilized OMDS under different confining conditions. This will facilitate the design and construction of foundations in this type of soil.