Study On Unconfined Compression Test Of Thawing Frozen Soil

Seasonal frozen soil widely distributes in northeast and northwest of China , and has caused a lot of damages to constructions . Compared to other projects , railway projects , especially in old ones , can more easily be affected by some factors—such as water ,soil quality ,minus temperature, outer load , etc.Freezing and thawing effects of frozen soil are particular natural phenomena . Besides , human being have been participating in these processes , which make up of the corporate development of frozen soil environment . With the exploiture to natural resource and the development of the economy , many state governments , institutions , universities , departments of road , airport, oil , mine , industry and military all have been doing some researchs on frozen soil projects , hoping to solve all kinds of problems in constructions . Especially in the north regions , foundation instability and track deformation , caused by frost heaving and mud mumping , have been severely restricting the development of high speed railway . Therefore , researches on the frost heaving and thawing characteristic of frozen soil have been given widely attention .The strength of frozen soil will reduce obviously after it is thawed ,which will result in mud pumping in subgrade as well as the instability of foundation in seasonal frozen ground regions. In order to find out the mechanism of the soil strength weakening during the thawing process and design the effective prevention measures, we will do some non-sides limit pressure tests, and analyze the effects of some factors .The results show that water content , freezing temperature and thawing temperature play great roles on the strength-weakening characteristic of frozen soil thawed .There is a critical value between 18 percent and 20 percent of water content , which is called optimal water content . At this critical value , the failure strength and mechanics characteristic of frozen soil are best. Below the critical value , the failure style belongs to brittle failure ; beyond the value , the style tends to plastic failure , and the stress-strain relationships appear to hardening trend .As a kind of natural geologic materials , soil presents apparent anisotropy , heterogeneity , discontinuity and randomicity texturally and strong non-linearity , non-elasticity and viscosity in mechanics capability . Soil constitutive models are this kind of mathematical expressions which reflect these mechanical behavior . A experiential formular is given for the applications of real projects , which is composed of a linear equation and Gauss .The thawing frozen soil is inflicted by dynamic load . Stress-strain relationships between the effects of dynamic load and of dead load are compared , which will also support the constructions .