Study of the Rock Crack Reaction in Low Temperature

Abstract: Aims at the rock stability in low temperature underground cavern, this paper investigates the crack fracture when rock suffers sub-zero temperature. the crack of I type was chosen for the main object to study and the influence of rock type and the temperature fall process on the crack fracture was to be investigate. Besides, the crack of I and II complex type was chosen for the subordinate object to study and the influence of the crack obliquity on crack fracture was to be investigated. The results of this paper have some reference value to the analogously projects and similar study.The concrete famation of crack fracture criterion was set up when crack under cooperate action of the temperature stress and the initial stress. From the criterion, the influence of the depth of caven, the rock type and the temperature difference in the cavern on the crack fracure can be gained.The similation analysis results show that the most key fator that influenct the crack fracture is the linear expansive coefficiency(LEC). When the LEC down with the temperature down as the rock usually behave taken into account, the stress intensity factor(SIF) in crack tip change to be 50% to 60% of the original value, further more, when the LEC value increace, the SIF will increace too, and the difference of the SIF was no less than the difference of the LEC multiply to 0.8. Beside, the elastic modulus of rock also has some affect on crack fracture.The length of the rack increase 150% of the original value, the SIF at crack tip woud increace appromately 50% of the orignial value. And the lower the temperature applied, the larger of the SIF would be, and the difference of the SIF is 10% to 30% times less than the difference of the temperature. The crack would be the I and II complex type when the crack not perpendicular to the carven surface. The crack fracture along the direction of temperature spread irrespective to the crack obliquity but the fracture length is depended on the crack obliquity. The greater of the angle of the crack surface and the temperature spread direction, the larger of the crack openness. With the angle increase from 5o to 85o, the SIF at crack tip of I type increase and the SIF at crack tip of II type increase and then decrease as a apex, the greatest value of the SIF at crack tip of II type was gotten when the angle is 45 o.Some tables and graphic was offered in the paper and provide some conference value to the project design which shows the relationship of temperature of the medium to be stored and the allowed depth of the cavern location in curtain geologic condition.Key words:low temperature, crack, temperature stress, stress intensity factor, fracture tempe…
Key words: low temperature; crack; temperature stress; stress intensity factor; fracture temper

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