| Abstract： |
The swelling characteristics of swelling soft rocks (SSRs) in the Yanji Basin, Northeastern China, have posed huge challenges to the construction of local highways. Based on the geological background, the swelling properties and strength characteristics of undisturbed and reconstructed SSRs, especially the constitutive relationship, are studied, which is of great significance to engineering practice. In this study, X-ray diffraction and scanning electron microscopy were used to determine SSRs' mineral composition and microstructural characteristics. Swelling test, shear test, and unconfined compression test were used to identify the relationship between different water content of SSRs and free swell ratio (delta(e)), swelling pressure (P-e), stress-strain characteristics, and strength, respectively. The results showed that (1) the mixed layer content of illite-montmorillonite in SSRs reached 95%. (2) delta(e) and P-e were negatively linearly and exponentially related to the initial moisture content (omega(s)), respectively. Rapid and intense swelling mainly occurred at the initial swelling stage. (3) omega(s) were negatively linearly related to the shear stress (tau), cohesion (c) and the angle of internal friction (phi). In addition, SSRs with lower omega(s) suffered strain softening failure, while SSRs with higher omega(s) suffered strain hardening failure. (4) delta(e) and the moisture content after swelling were both linearly related to the logc and log phi. Furthermore, the optimum moisture content (21-26%) of SSRs of the Yanji Basin's project was determined for the first time. These results have already been applied to engineering practice in the Yanji Basin and other regions where SSRs are widely distributed. |
