![]() ![]() ![]() ![]() Then from macro perspectives, contents and abrasiveness of mineral compositions will be adopted as vital index for hobbing cutter abrasion. Quantitative abrasion rules of the seven minerals on hobbing cutters will be ascertained. The specimen is made up of seven main rock-forming minerals and a new self-developed transparent rock-like resin material. First of all, in the view of micro mineral compositions, rock abrasiveness tests are to be carried out. One is on abrasion mechanism of hobbing cutters. This research program is based on South Qinling tunnel of Hanjiang-to-Weihe River project, and two issues will be investigated. The experimental results are supported by poroelasticity and fracture mechanics analysis of the process, and may be applied to influence hydrailic fracture orientation in the field. Finallt, the influence of pressure gradient induced body forces is demonstrated by generating fractures connecting two pore pressure source points. The fractures are shown to propagate towards regions of higher local pore pressure. ![]() In other experiments, controlled fractures are propagated both mechanically and hydraulically across sandstone slabs subjected to non-uniform pore pressure fields. Simple fracture initiation tests conducted on cylindrical limestone and sandstone rock samples are first described which support an effective stress law for tensile fracture initiation in very porous rocks. Fracture is influenced by both pore pressure magnitude on a local scale around the crack tip and by the orientation and distribution of pore pressure gradients on a global scale. Theoretical analysis and experimental results are presented to describe the influence of pore pressure on tensile fracture initiation and propagation direction. ![]()
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June 2023
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