Experimental Investigation On Creep Characteristics Of Warm And Ice-rich Frozen Sandy Silt Of Qinghai-tibet

The annual average temperature is lower than 0℃ of the Qinghai-Tibet Plateau, with more than 70% of the permafrost in China, the area of permafrost is up to 150 0000 square kilometers. Engineering survey data show that, there is a significant proportion of warm and ice-rich frozen soil in permafrost regions of the Qinghai-Tibet Plateau. But warm and ice-rich frozen soil has unstable complex mechanical properties, under long-term effects of the external load, it is easy to produce creep deformation obviously. It is great threat to the stability of highway engineering structures. For shallow frozen soil of the highway subgrade, and the difference between deep frozen soil, the stress of the shallow frozen soil is small, only loading the force of small stress and confining pressure. But for triaxial creep test of warm and ice-rich frozen soil, because of long test period, the temperature control is not accurate, frozen sample making is not mature, Etc. The relevant research data is very lack.For that reason, this paper made the highway of Huashixia Valley to Da Wu in Qinghai province as a project. developing the triaxial creep apparatus of frozen soil, studying the preparation method of warm and ice-rich frozen soil sample, and studying on the triaxial creep test of warm and ice-rich frozen soil, trying to establish a creep empirical model of the Qinghai-Tibet Plateau frozen sandy silt. The main research contents and achievements are as follows:Firstly, for the large-scale triaxial creep apparatus of frozen soil is expensive and so on, through market research and cost analysis, based on the research purpose of low-cost and high-precision, self-developed the triaxial creep apparatus of frozen soil to achieve automatic collection of the displacement and axial pressure; And by comparison instrument design, using pneumatic servo system to achieve the adjustable function of axial compression and confining pressure; using the method of cold bath circulation to control the freezing conditions of frozen soil sample.Secondly, for the preparation method of warm and ice-rich frozen soil sample is not mature, not yet unified and so on, based on the commonly preparation method for frozen soil samples in china, through extensive testing, determine the preparation method and detailed preparation process of ice-rich frozen soil.Then, the paper use self-developed triaxial creep apparatus of frozen soil, for warm and ice-rich frozen sandy silt sample in the typical highway of Qinghai province Huashixia Valley to Da Wu, carry out the triaxial creep test, based on the regular of the highway subgrade shallow frozen soil, using the experiment method of freezing-consolidation-creep to simulate the engineering practice, this paper study ice content, consolidation stress, consolidation temperature, load stress, load temperature, load stress ratio and so on,how to effect creep characteristics of warm and ice-rich frozen soilFinally, several typical creep empirical mode are used to fit the experimental data, by comparing the test results, the paper selects the appropriate creep empirical mode of warm and ice-rich frozen soil.