In-situ pressuremeter test in warm and ice-rich permafrost

In order to investigate the in-situ mechanical behavior of warm and ice-rich frozen soils, a series of pressuremeter tests were carried out in permafrost regions on the Qinghai-Tibetan Plateau. Based on the test results, the relationship between stress and strain was obtained using Ladanyiʹs theory, and it can be described by a hyperbolic model. Moreover, two critical mechanical parameters, ultimate shear strength and initial shear modulus, for each test were deduced from the hyperbolic model. The shear strength increases linearly with decreasing temperature regardless of the water content, while the variation of the shear strength with the water content presents an exponential tendency. Comparing the results of pressuremeter tests with the results of triaxial test and uniaxial test, it can be found that the strengths obtained from pressuremeter tests are always greater than those of indoor tests. In the earlier stage of the pressuremeter test, the circumferential stress is reduced by the same increment as the radial stress increases. However, when the radial stress reaches a certain value, the circumferential stress increases gradually and even becomes a compressive stress.