Creep Characteristics of Frozen Sand under Dynamic Loading
ZHAO Shu ping, HE Ping, ZHU Yuan lin, CHANG Xiao xiao (State Key Laboratory of Frozen Soil Engineering, CAREERI, CAS, Lanzhou Gansu 730000, China)
Determining creep indices and developing creep model are two main tasks of the research on creep behavior of frozen soil, one important part of frozen soil mechanics. Many researchers have engaged in this field. As a result, some creep models, such as attenuation creep model, steady creep model, gradual flowing creep model and tertiary creep model, were developed. The influence of confining pressure, maximum axial stress and loading frequency on creep properties was evaluated. The creep yield criteria were presented. However, most of these works involve the creep behavior of frozen soil under static loading condition, and involve the frozen silt under dynamic loading condition. Fewer documents involve the creep characteristics of frozen sand under dynamic loading, which will be discussed in this paper. A series of creep experiments under various conditions, namely different temperature, various frequency and different maximum axial stress, were conducted on MTS, then creep curves were drawn and creep modal was put forward. The primary creep model ε=Aσ mt λ (Vyalov) was used to analyze the first and second stages of creep. Then, referring to the creep models under static loading condition and considering the features of dynamic loading, equation ε/σ n=B 1+B 2t 1/3 +B 3t was used to predict the whole creep process. Comparing the two analysis methods, it can be noticed that the coefficients of two regression methods are similar. However, the latter method has the advantage of predicting whole creep process. The influence of loading, temperature and loading frequency on creep failure factors (failure strain, time to failure and minimum creep rate) was evaluated. The test results indicate: (1) Failure strain increases, time to failure shortens and the minimum creep ratio quickens with increasing axial stress. The variation rate of creep factors is different between stress less than 2 MPa and stress more than 2 MPa. (2) The lower the temperature is, the less the failure strain, the longer the time to failure and the less the minimum creep ratio will be. The variation rate of creep factors is different between temperatures lower than -10 ℃ and higher than -10 ℃. (3) No obvious frequency dependent change of the minimum creep rate was found, which seems varying within a range. But there is a trend that the minimum creep rate slightly decreases with increasing frequency. Time to failure shortens and failure strain lessens with increasing frequency. When it is less than 7 Hz, the frequency greatly influences the failure strain and time to failure. But the failure strain and time to failure slightly decrease with increasing frequency when frequency is greater than 7 Hz.
【Fund】： 中国科学院寒区旱区工程与环境研究所知识创新工程项目 (CACX2 10 0 13 ) ;; 中国科学院知识创新工程重大项目 (KZCX1 SW 0 4) 资助
【CateGory Index】： P642.14
【CateGory Index】： P642.14