Suppose that a fracture plane in the formation is a plane of weakness, and that the strength of the formation is identical in other directions. The criterion for failure to occur along this plane can be written in the following form (Jaeger et al, 2007):(1)where is the maximum principal stress; is the minimum principal stress; S w is the cohesion of the plane of weakness;is the coefficient of internal friction of the plane of weakness; and is the angle between the normal to the plane of weakness and the direction of the maximum principal stress, .The stress difference required to cause slippage along the plane of weakness can be found from Eq. (1). If or ( is the angle of internal friction of the plane), Eq. (1) shows , i.e. slippage will not occur; if(2) and the stress difference, meets Eq. (1), slippage will occur. Otherwise, rock mass failure occurs and obeys the following relationship:( 3) where is the coeffi cient of internal friction of rock mass; is the cohesion of rock mass.In cylindrical coordinates, the stresses acting on the Abstract: Based on the plane of weakness theory, a model for predicting borehole stability in fractured reservoirs under different stress states was estiblisted and the equations for solving borehole stability were developed. The minimum downhole pressures required to maintain borehole stability under different natural fracture occurrences were calculated by using the data from a well in the Tazhong (central Tarim) area, Tarim Basin, west China. Several conclusions were drawn for naturally fractured reservoirs with a dip angle from less than 10 º to greater than 30 º. Application in three wells in the Tazhong area indicates that this model is practically useful.

This study aims to investigate the impact of dual credit policy on the diffusion of new energy vehicles (NEVs) from the perspective of complex interactions among heterogeneous manufacturers. Thus, the market competition and credit cooperation relationships, constituting the complex interrelated system in NEV diffusion, are considered in this paper. To this end, we established a double-layer complex network to depict the asymmetric competition and cooperation structure, and developed an evolution game model on network, revealing the diffusion rule and trend of NEVs among manufacturers. Simulation results show that the existence of credit cooperation relationship can effectively improve the diffusion of NEVs, especially when implementing cooperative strategy that prioritizes helping manufacturers with low sale profits. Such a cooperative strategy is effective for maintaining high diffusion of NEVs even under low NEV credit’s trading price. Meanwhile, the monopoly competitive structure characterized by scale free is harmful to NEV diffusion. However, credit cooperation can eliminate the by-effect of monopoly structure greatly by adopting the strategy of distributing by sale profits. In addition, manufacturers are advised to learn from their competitors during the evolutionary process, which should be the focus of manufacturers to maximize the NEV diffusion under small world competitive structure.

With the increasing requirements for the exploitation of underground resources, the subject of the physical and mechanical properties of rocks under high temperature and pressure needs to be studied urgently. In order to analyze the mechanical and energy characteristics of rocks under different thermal damages and confining pressures (c), a triaxial compression test is performed on 35 marble samples. The effects of thermal damage and high pressure are simulated with different thermal cycles and confining pressures. The results show that as the number of thermal cycles increases, the peak strain of marble gradually rises, but the peak stress and the elastic modulus (E) decrease by a degree, reaching 11.19‰, 39.53 MPa, 4.79 GPa, while there is no confining pressure applied at eight thermal cycles. At this point, the failure mode gradually changes from brittle fracture to plastic failure. When confining pressure rises, peak stress, peak strain, and elastic modulus all show an upward trend, reaching a maximum of 189.45 MPa, 13.39‰, 35.41 GPa, while the sample is undamaged at 30 MPa confining pressure. Moreover, peak stress increases linearly with confining pressure increase. The increased rate of the peak value of the total absorbed energy, elastic strain energy, and dissipated energy all show a convex trend. The dissipated energy gradually increases with the axial strain (ε1) during the rock loading process. The elastic strain energy has an energy storage limit, but the rock fails when the value exceeds the limit. The limit increases first and then decreases with the number of thermal cycles. These results can provide important engineering references for mining underground resources.