Abstract: Domestic geotechnical engineers paid more attention to the drained stability of high filled ground; however, the undrained stability brought by rapid constructions was more of a problem for ground with a high groundwater level and poor drainage performances. The relevant standards existing in current specifications and the common methods about undrained stability analysis of slopes were reviewed. By analyzing the relationship between total stress friction angles and stress paths and by calculating the typical total stress paths of original ground in high-fill projects, an explanation was given why the undrained stability of high filled ground was overestimated when strength indexes of total stress from consolidated-undrained (CU) triaxial tests were applied to undrained analysis, which brought theoretical defects and engineering hidden dangers. Taking a simple hypothetical slope model and a real case of a proposed high-fill airport as example, the factors of safety (FOS) of the undrained stability were calculated through five undrained analysis parameters or models using simplified Bishop method respectively. The results show that the undrained stability of high filled ground is overestimated by the CU total stress method all the time; the FOS of undrained stability by other four methods are close, which verifies the relative applicability of these methods.

Key words: high filled ground, consolidated-undrained strength index, effective stress strength index, undrained shear strength, effective consolidation stress method, MCC model