The Preliminary Research Of Microdamage Mechanics Characteristics Of Rock Under The Condition Of Freezing And Thawing

In the cold geotechnical engineering, when the rock containing a mount of water was frozen, the inner water swells, and the freezing swollen force is emerged, in turn the rock became a multi damage material containing water, ice, air, rock. The freezing force and deformation have a important role in the stability of rock engineering. In this paper, the major work is posed according to the accentuated problem in the west development. The research method is concerned with freezing test, CT scanning and damage mechanics analysis. Based on the damage mechanics theory, during the freezing and thawing, the CT measurement technology is used to observe the water transference, ice formation, inner microdamage propagation principle and the corresponding damage structure variability. The following is done:(1)it is difficult to analyzed damage variables which is very little, therefore, a new method of CT number division is put foreword, in which damage evolution is reflected by the statistical frequency. (2)because of the variability of rock subjected to outside action, three new conceptions: postive damage basic damage and negative damage, are suggested, which can deal with the condition that rock density became large.(3)the present damage variables based on CT number mostly include CT average number of the rock without damage, which is difficult to measure, so a new damage variable, which includes the average CT number is proposed, on the other hand, strain equal theory is generalized because the one put foreword by Lemaitre is not good enough to use. (4)a axial damage constitutive equation is proposed and testified. (5)with the circle times, the damage propagation laws of two different rocks, subjected to circle of freezing and thawing, are studied, and in the analysis process, traditional analysis method including average CT number and is used, some important conclusions are reached: inner damage of soft rock containing a large mount of apertures is largely propagating with the time increasement of circle, however, at the preliminary time, the hard rock containing a small mount of aperture is a little propagating, at late time, the influence become large ;(6)zone separation and statistics frequency put forward is used to analysized the three different damagepropagation in the open circumstance, when they are subjected to the different circle times of freezing and thawing, in which the temperature variability is linear, different freezing rate, and different freezing temperature, and no water is supplied during the test. In the study, what's more, some particular experiment phenomenon are explained by means of theories, such as water move, the change of water and ice. In the test, the preliminary propagation of the hard rock containing a small mount of aperture is dominant during the test, inner damage of soft rock containing a large mount of apertures is largely propagating with the time increasement of circle, because the circle time is limited, the damage propagation can not be observed during enough times. The study also indicates that the freezing temperature has a part influence on the damage propagation. As is known that the water in the rock contains a mount of salt, and the kind and content in turn make the water freezing temperature variable. On the other hand, rock material will shrink when frozen, and expand when warmed. For the hard rock containing a small mount of aperture, the shrink of rock material is superior to the expansion of water. For the second hard rock with layer, when freezing temperature is at 0 , the water disappearance is dominant, however, when at -10 and -20 , the water shrink is dominant. For the soft rock, the shrink of material and reconstruction of particle is dominant, and density of rock is large. The freezing rate also influences the rock damage propagation. In the whole, the density get large when frozen, and the freezing rate is reverse rational to the degree of the density enlargement. The density get small when frozen, and the freezing rate is reverse rational to th...