用8000KN多功能三轴仪测量脆性岩石的扩容、蠕变及松弛

Dilatancy Creep and Relaxation of Brittle Rocks Measured with the 8000 KN Multipurpose Triaxial Apparatus

本文提出了系统研究岩石在脆性范围内的扩容,蠕变及松驰性状的初步报告. 文中全面地描述了新型的8000KN伺服控制的多功能三轴仪.在常应变率为5×10^(-5)/sec,对四组16个房山花岗岩和济南辉长岩试件进行了从100MPa到400MPa的各种围压和从25°到250℃的各种温度的试验.根据以前提出的蠕变扩容本构方程(陈、康,1980,1983),介绍了一种确定扩容参数n,D~*和C的新方法.试验经果表明扩容随着温度的增加而增加,随着围压的增加而受到抑制。为了进一步研究在线性和扩容阶段与时间有关的变形,进行了蠕变和松驰实验.在围压和温度分別为100和200MPa,7℃和200℃的条件下,采用梯级加载对房山花岗岩进行了二个蠕变试验.用这种方法还能从一个试件获得蠕变和扩容依赖于偏应力和时间的关系。最后,在围压分別为100MPa和200MPa,和温度分别为7℃和200℃的条件下,采用随时间变化的梯级应变,对花岗岩进行了二个松驰试验.从所得的应力—应变关系中确定出蠕变和松驰在扩容开始时的临界值f~*.文中还分析了与时间有关的扩容过程,并指出它与裂纹的增长、接合和产生,而导致的结构变化有关.

A comprehensive description is given of the new 8000 KN servocontrolled multipurpose triaxial apparatus for the research of the dilatancy, creep and relaxational behaviour of rocks in the brittle stage. Eight series of tests at the constant strain rate of 5×10^(-5)/sec on samples of Fangshan granite and jinan gabbro have been performed for various confining pressures and temperatures; the dilatancy parameters have been determined on the basis of constitutive equations for creep dilatancy presented earlier (Tan, Kang 1983). The tests show an increase of dilatancy with the temperature and suppression of dilatancy with the confining pressure. A creep test on Fangshan granite has been carried out under a stepwise loading under 200 MPa confining pressure and a temperature of 200℃; in this manner the dependence of creep on deviatoric stress and time can be obtained very easily from one sample. At last a relaxation test under the same confining pressure and temperature has been performed under stepwise straining with the time. The yield values f* for creep and relaxation have been determined from the stress-strain isochrones. An analysis of the time dependent processes of dilatancy is presented in connection with structural changes due to crack growth, coalescence and generation.