A series of critical fracture toughness of two kinds of rock materials under different temperature which varied from-50°C to 240°C are measured by I-II-III mixed mode fracture experiments adopting atypical three point bending specimens. Relative stress intensity factors of crack initiation are calculated by finite element method. Combining with calculated values, the experiment results show that, the mixed mode fracture toughness of the rocks decreases with the increase of temperature. The experimental and calculated results can be used in the design of deep underground engineering or disaster prevention and mitigation engineering.

A series of torsion tests under different temperature were carried out with circumferential notched cylindrical rock specimens. By this kind of specimens, mode III rock crack propagation in real meaning was realized. The initiation torsion M of the mode III rock crack was measured under different temperature. The variation law of M v.s. temperature T was obtained. The initiation stress near crack tip under different temperatures was calculated by finite element method, and then, the mode III fracture toughness KIIIC of the rock was obtained by further calculation. The experiment and numerical results show that the mode III fracture toughness of the rock decreases with the temperature increase. The results of the paper can be used in the design of deep underground engineering ,disaster prevention and mitigation engineering.

This paper illustrates some preliminary experimental, numerical and theoretical analysis results of mixed mode I-III rock cracks under apparent mode III loading. Some edge notched granite specimens are tested under out-of-plane four-points shearing loading condition, i.e., an apparent mode III loading condition. A series finite element analysis was conducted to understand the mechanism of the crack fracture propagation under this loading condition. The stress intensity factor distributions along the 3-D crack tips are also obtained. All crack fracture propagation surfaces of the specimens are similar helicoids which radius can be mainly influenced by the loading patterns, i.e., the action width s. The crack fracture initiates at the midpoint of the crack front. From the numerical calculation and experimental investigation, it has been revealed that all of these crack fracture initiations are caused by maxima tensile stress σ1. Based on this stress σ1, a new fracture criterion of mixed mode I-III is proposed. Its predictions agree well with the experiment results. This criterion can be applied to practice engineering designs which are related with mixed mode I-III or pure mode III rock crack fracture problems.

No abstract

The nonlinear behavior of the full scale test of the composite joint between steel reinforced concrete beam and concrete filled steel tubular column under low cyclic reversed loading are simulated by using finite element software ANSYS. A separated model was used, element concrete solid 65, element shell 181 and element link 8 were used to model concrete material, steel members and steel bars respectively. The numerical analysis results are compared with the data of the experimental research. The advantages and shortcoming of the finite element model are given. A better numerical simulation method and a use for reference to the similar case are expected to be afforded.