Using the MTS815 Full-Digitally Servo-Controlled Rock Mechanics Testing Machine, three different types of brittle rocks retrieved at the 1870 Level of the Kafang Mine are tested in the laboratory experiments under uniaxial compression. Four different failure patterns are observed during this test. Most common failure patterns are axial splitting, V-shaped failure, X-shaped and shear failure as well. The 2-dimensional particle flow code (PFC2D) was used in the numerical simulations because of its capability in modelling the behavior of brittle rock material including fracture propagation. Contact-force distribution, crack distribution, stress–strain response and damage patterns formed during uniaxial compression tests are observed. The parameters used in the numerical simulations are calibrated when rock parameters such as uniaxial compressive strength, elastic modulus and Poisson’s ratio, are in agreement with the experimental results. Splitting and faulting failure modes frequently observed during laboratory experiments of rocks under uniaxial compression are also reproduced in the simulations. Damage formation during the compression simulations indicated that the PFC2D modeling could simulate the events happening during the laboratory compression tests of rock samples by reproducing similar fracture generation and deformation.
The study of brittle fracture process under compression is essential for understanding many processes encountered in rock engineering and earth sciences[1]. Laboratory experiments have traditionally been used as a simple and effective way to investigate the progressive failure process in rock material under uniaxial compression. Also, the failure of brittle rocks in laboratory cylindrical compression tests has been investigated by many researchers[2-6].
Meanwhile, numerical models (such as lattice model[7], bonded particle model[8-9], RFPA model based on FEM[6,10-11] and other models[12-15]) were used to model the fracture process of rock under loading. Although the failure model of rock subjected to uniaxial compression has been studied in detail for decades, the failure mechanisms, including the micro-cracks initiation, propagation, coalescence, axial splitting, shearing, etc., are not fully understand and still remain the subject of considerable scientific interest[16].
This paper presents a series of laboratory and numerical tests of different rock under uniaxial compression to investigate the fracture process. The marble, skarn and silicateous marble were chosen as the rock specimens in this study. The two dimension particle flow code (PFC2D) was chosen because of its capabilities in modelling the fracture process including fracture initiation, propagation and coalescences of rocks. Then the results from numerical simulation are presented and compared to those obtained from the laboratory tests.
A total of 15 rock specimens consisting of five samples from each type of marble, skarn and silicaceous marbles, were prepared for uniaxial compression tests (Fig.1).
All the cylindrical rock specimens are retrieved at the 1870 Level of the Kafang Mine, Yunnan Tin Group Corporation. The marble specimens were of 50mm in diameter and 100mm in length. The skarn and silicaceous marble specimens were of 60mm in diameter and 120mm in length. The density of marble, skarn and silicaceous marble are 2.789, 3.269 and 2.817g/cm3, respectively.
