Oil and gas are the main reserves in the fractures of rocks. Under different pressure conditions, fracture permeability of reservoir rock directly affects the flow of oil and gas, which is an important object of oil and gas exploration and development. The permeability of single fractured rock and double fractured rock under different pressure conditions was studied by using high-precision hydro-mechanics coupled triaxial experimental equipment. The experimental scheme is as follows: (i) permeability test under increasing confining pressure, (ii) permeability test under increasing liquid pressure, (iii) permeability test under cyclic loading and unloading deviatoric stress and (iv) permeability test under synchronously increasing confining pressure and deviatoric stress. Results show that the entire change of permeability is irreversibly reduced. This is due to the presence of residual factors in permeability after the dilation cycle and the recompaction cycle ends. On the basis of the dual medium model of fracture, the permeability model of fractured rock is proposed considering the interaction among fracture system, matrix system and expansion deformation of fracture under external stress. The simulation results of the model are in good agreement with the experimental results. These results can provide an important basis for the prediction of permeability of fractured rock and efficient oil and gas exploitation.
Vigilance is recognized as the response to potential predation threats. Many factors influence vigilance behaviour, and the effect of group size has had a great deal of attention in recent years. The group size effect hypothesis proposes that there is a negative relationship between group size and vigilance, which has been proven ture for many birds and mammal species. However this relationship has not been investigated for a number of other species including the the Equus kiang. The E. kiang is the largest wild ass in the world, and endemic to the Tibetan Plateau. Previous studies have reported its distribution and reproduction, but information about their behaviour especially their daytime activity budgets is still very limited. Also unknown is if the distinctive habitat of the Tibetan Plateau makes their behaviour different from other Equidae species. So in this paper, we discuss our behavioural observations of the daytime activity budgets and the group size effect on vigilance for the E. kiang population in the Arjinshan National Nature Reserve, Xinjiang, China. The results indicate that group size has a significant effect on the vigilance levels: with an increase in group size, both the group scan level decreased and group scan frequency increased. Our results also showed that E. kiang spent most of their time feeding (51.41
± 2.74 %), followed by moving (22.49 ± 1.40 %), standing (19.62 ± 6.74 %), resting (18.41 ± 2.13 %), and other activities (8.64 ± 0.72 %). Their feeding behaviour showed three distinct activity peaks during the day: early morning (8:00-11:00), midday (14:30-15:30), and around sunset (18:00-19:30). During the peaks of activity, E. kiang spent most of their time feeding, and during the period of inactivity, E. kiang spent most of their time resting and standing. So the group size effect was supported for E. kiang by this study, and our results are consistent with research on other Equidae species.