Xiaoliang Yao

Analysis on the Settlement of Roadway Embankments in Permafrost Regions

In permafrost regions, the embankment settlement results from several physical and mechanical processes taking place in the different soil layer, making its mechanism very complicated. Under the thermal influence of embankment, climate warming as well as geothermal source, permafrost may degrade downwards or upwards, which continuously changes the thicknesses of the permafrost layer and the also unfrozen soil layers. Thus, any attempt to analyze the embankment settlement seems to be very troublesome and difficult. In this paper, based on ground temperatures of embankment sections in five typical regions along the Qinghai-Tibet Highway (QTH), the trends of variation of different soil layers and the thermal gradients are investigated. On this basis, four types of sections, which can represent most of the sections of QTH, are deduced to clarify the possible settlement sources in different soil layers. In order to further confirm and investigate of the settlement sources, an embankment model test was carried out. Combing the in-situ monitoring data with the results from the model test, the main settlement sources in embankment settlement are discussed for the four types of sections respectively. The results will facilitate the analysis of embankment settlement in permafrost regions.

Pore Water Pressure Distribution and Dissipation During Thaw Consolidation

A novel apparatus was developed for measurement of pore water pressure distribution and dissipation during thaw consolidation. Thaw consolidation tests were conducted to verify the applicability of nonlinear stress–strain relationship in 3-D large strain thaw consolidation theory. During thawing process, the measured pore pressure at different layers of soil samples increased sharply at first; when a certain value was approached, it stepped into dissipation stage. It was proved that the calculated results have a good agreement with tested results on both pore pressure distribution and dissipation. Further analysis indicated that nonlinearity of pore pressure distribution was proportionally related to thaw consolidation ratio (R), while it was opposite for thaw consolidation degree.

A Visco-Hypoplastic Constitutive Model and Its Implementation

This paper presents a hypoplastic constitutive model for the viscous behaviour of frozen soil. Then the model is implemented into \(\mathrm{FLAC3D}^{\circledR }\). The performance of the model is demonstrated by simulating a compression creep test with the tertiary stage and the deformation of an embankment.

Strength attenuation effects on rate-dependent law of stress development of frozen sand

Abstract In this paper, effects of strength attenuation on stress development tendency (strain hardening or softening) under different strain rate were analysed. A series of triaxial creep and constant strain rate compression tests were conducted on frozen sand samples. Based on test results analysis, it was indicated that strength attenuation function is usually underestimated with the creep test results. After correcting the function with constant strain rate test results, it was verified that the calculation accuracy of a rate-dependent model with strength attenuation proposed by the authors is improved greatly. Further theoretical analysis indicates that the development tendency of stress (strain hardening or softening) under different constant strain rates is dependent upon relative position between stress point and failure line in p−q space, and strain softening degree is dependent on applied strain rate and the law of strength attenuation.