硬岩脆性指标与弹性应变能关系初探

为探讨硬岩脆性指标与弹性应变能之间的关系,采用侧向应变差法确定起裂应力,以岩石起裂应力和峰值强度为桥梁,基于断裂力学理论和能量理论解释了脆性指标与弹性应变能内在的联系,并从两种岩石单轴压缩试验中构建了脆性指标与弹性应变能之间的函数关系.结果表明:脆性指标B_(13)、B_(14)与起裂弹性应变能(单变量)符合幂函数关系,脆性指标B_(15)、B_(16)与起裂弹性应变能(单变量)符合幂函数或线性函数关系,脆性指标B_(13)、B_(14)、B_(15)和B_(16)与峰值弹性应变能(单变量)之间无明显函数关系;新定义的脆性指标可由起裂和峰值弹性应变能(双变量)获得,或由起裂弹性应变能(单变量)获得,脆性指标与峰值弹性应变能关系式的构建,对于研究岩爆倾向性具有重要意义;根据新定义的脆性指标,利用两种岩石算例验证表明,采用起裂弹性应变能的岩石脆性指标计算方法具有一定的可靠性.通过这一研究,为岩石脆性指标与起裂弹性应变能关系的确定提供了一种新方法.

Preliminary study on relationship between brittleness index and elastic strain energy for hard rock

To study the relationship between brittleness index and elastic strain energy, the lateral strain response method was used to determine the crack initiation stress of hard rock. By using the crack initiation stress and peak stress of rock, the relationship between brittleness index and elastic strain energy was explained based on fracture mechanics theory and energy theory, and a functional relationships were constructed between brittleness index and elastic strain energy from uniaxial compression test for two types of rock. Results show that the brittleness indexes B₁₃, B₁₄are in power function relationship with the crack initiation elastic strain energy (single variable), and the brittleness indexes B₁₅, B₁₆are in power or linear function relationships with the crack initiation elastic strain energy (single variable). However, no apparent functional relationship was discovered between the brittleness indexes B₁₃, B₁₄, B₁₅, B₁₆and the peak elastic strain energy (single variable). The new brittleness index could be either obtained from both the crack initiation strain energy and the peak elastic strain energy (two variables), or the crack initiation elastic strain energy (single variable). The relationship between brittleness index and the peak elastic strain energy is of great significance for studying rock burst proneness. The calculation method for brittleness index was redefined. Besides, the verifications of two examples show that this method, using the crack initiation elastic strain energy, demonstrates certain credibility. This study provides a new method determining the relationship between brittleness index and the crack initiation elastic strain energy of rock.