工程岩体大多处于复杂的应力环境中。由于岩体裂纹走向相对于荷载方向的随机性，岩体脆性断裂多数由于Ⅰ-Ⅱ混合型裂纹的产生，因此研究岩石Ⅰ-Ⅱ混合型裂纹断裂有着非常重要的理论意义和工程价值。现行通用的适用于Ⅰ-Ⅱ混合型裂纹的...工程岩体大多处于复杂的应力环境中。由于岩体裂纹走向相对于荷载方向的随机性，岩体脆性断裂多数由于Ⅰ-Ⅱ混合型裂纹的产生，因此研究岩石Ⅰ-Ⅱ混合型裂纹断裂有着非常重要的理论意义和工程价值。现行通用的适用于Ⅰ-Ⅱ混合型裂纹的断裂准则，如最大周向应力准则，即MTS（Maximum tangential stress criterion）准则，最小应变能密度准则，即SED（Minimum strain energy density criterion）准则，最大应变能释放准则，即G（Maximum energy release rate criterion）准则，均未考虑T应力的影响。本文通过理论分析，ABAQUS数值模拟，反对称四点弯曲实验研究三个方面探究T应力对裂纹起裂扩展到影响。展开更多
of PhD thesis For the mode I rock fracture toughness measurement,three standard methods have been recommended by the ISRM,but there has not been a standard method for the determination of mode II and mixed mode I-II r...of PhD thesis For the mode I rock fracture toughness measurement,three standard methods have been recommended by the ISRM,but there has not been a standard method for the determination of mode II and mixed mode I-II rock fracture toughness. However mode II and mixed mode I-II fracturing of rock structures is more commonly observed than mode I in various geological and structural engineering settings. So it is of great important to thoroughly research these rock fracture problems and establish a standard method for determining the mode II or mixed mode I-II fracture toughness for rock materials. Based on the progress made for mode I rock fracture research,the cracked chevron notched Brazilian disk (CCNBD) specimen was also introduced for mode II and mixed mode I-II rock fracture toughness measurement. When the crack is orientated at an angle with respect to the diametrical loading,the crack of the CCNBD specimen is exposed to the mode II or mixed mode I-II stress distribution conditions. The solutions for stress intensity factors in the vicinity of the crack tip have been evaluated by the stepwise superimposition technique. In order to make sure that the theoretical analysis is correct,numerical calculation method has been employed to calibrate the theoretical results. It has been proved that the theoretical results yielded by the dislocation method are correct and reliable. According to the characteristic that the propagation of the crack in the CCNBD specimen is in its own plane and application of the energy superposition principle,the stress intensity factor of the mixed mode I-II has been defined in dimensionless terms as 212II2Imix])()[(***+=YYY. It was found that the curve of *mixY was concave. There exists a lowest point which corresponds to the maximum external load and indicates the crack has reached its critical state. Since the values of ***IIImix and YYY, are only dependent on the specimen geometry (qaaa and 10B,,),the critical values of ***IIImix and YYY, can be to known as long as the CCNBD specimen 展开更多
文摘工程岩体大多处于复杂的应力环境中。由于岩体裂纹走向相对于荷载方向的随机性，岩体脆性断裂多数由于Ⅰ-Ⅱ混合型裂纹的产生，因此研究岩石Ⅰ-Ⅱ混合型裂纹断裂有着非常重要的理论意义和工程价值。现行通用的适用于Ⅰ-Ⅱ混合型裂纹的断裂准则，如最大周向应力准则，即MTS（Maximum tangential stress criterion）准则，最小应变能密度准则，即SED（Minimum strain energy density criterion）准则，最大应变能释放准则，即G（Maximum energy release rate criterion）准则，均未考虑T应力的影响。本文通过理论分析，ABAQUS数值模拟，反对称四点弯曲实验研究三个方面探究T应力对裂纹起裂扩展到影响。
文摘of PhD thesis For the mode I rock fracture toughness measurement,three standard methods have been recommended by the ISRM,but there has not been a standard method for the determination of mode II and mixed mode I-II rock fracture toughness. However mode II and mixed mode I-II fracturing of rock structures is more commonly observed than mode I in various geological and structural engineering settings. So it is of great important to thoroughly research these rock fracture problems and establish a standard method for determining the mode II or mixed mode I-II fracture toughness for rock materials. Based on the progress made for mode I rock fracture research,the cracked chevron notched Brazilian disk (CCNBD) specimen was also introduced for mode II and mixed mode I-II rock fracture toughness measurement. When the crack is orientated at an angle with respect to the diametrical loading,the crack of the CCNBD specimen is exposed to the mode II or mixed mode I-II stress distribution conditions. The solutions for stress intensity factors in the vicinity of the crack tip have been evaluated by the stepwise superimposition technique. In order to make sure that the theoretical analysis is correct,numerical calculation method has been employed to calibrate the theoretical results. It has been proved that the theoretical results yielded by the dislocation method are correct and reliable. According to the characteristic that the propagation of the crack in the CCNBD specimen is in its own plane and application of the energy superposition principle,the stress intensity factor of the mixed mode I-II has been defined in dimensionless terms as 212II2Imix])()[(***+=YYY. It was found that the curve of *mixY was concave. There exists a lowest point which corresponds to the maximum external load and indicates the crack has reached its critical state. Since the values of ***IIImix and YYY, are only dependent on the specimen geometry (qaaa and 10B,,),the critical values of ***IIImix and YYY, can be to known as long as the CCNBD specimen
