Effect of soaking time of dithionite–citrate–bicarbonate solution on strength and deformation characteristics of lateritic soil

Abstract

This study aimed to reveal the influence of different free-iron-oxides contents on the strength and deformation characteristics of in situ lateritic soil. A test method that combined the selective chemical dissolution method and in situ Ménard pressuremeter test (PMT) was proposed. The soaking time in dithionite–citrate–bicarbonate (DCB) solution was used as a variable to control the free-iron-oxides content in lateritic soil. Then, the in situ lateritic soil boreholes with different soaking time were tested by PMT. The results showed that the in situ horizontal pressure p0, critical edge pressure pf, ultimate pressure prediction pl, pressuremeter modulus Em, shear modulus Gm, and foundation-bearing capacity f0k of lateritic soil decreased rapidly after immersing in DCB solution within 1–4 d. With increasing soaking time, the decrease rate reduced gradually. Moreover, the relationship curve between free-iron-oxides content and soaking time declined rapidly and then stabilized, and the free-iron-oxides content at the inflection point was 30.11 g/kg. When the free-iron-oxides content changed to the inflection point, the free-iron-oxides that played a cementing role was largely removed, indicating that the effective cementing iron-content of Miaoling lateritic soil was about 52.9%. This study demonstrated that the proposed test method can determine the influence of free-iron-oxides content on the strength and deformation characteristics of lateritic soil.

Keywords

• Lateritic soil
• Ménard pressuremeter test (PMT)
• Free-iron-oxides
• Dithionite–citrate–bicarbonate (DCB)
• Effective cementation of iron