含V型相交裂隙岩体的力学特性及破坏模式试验

为深入了解V型相交裂隙岩体试件的力学特性和裂纹演化规律,采用MTS815电液伺服控制试验机对含不同夹角V型相交裂隙岩体试件进行了常规单轴压缩试验,基于试验结果,详细分析了试件的应力-应变曲线、强度与变形特性、裂纹演化与破坏模式及能量耗散特征。研究结果表明:①裂隙试件的应力-应变曲线进入裂纹萌生与扩展阶段早于完整试件,在峰前出现了明显的应力降现象,在峰后破坏阶段,完整试件表现为应力-应变曲线的快速跌落,而裂隙试件呈现台阶状多阶段性跌落,甚至缓慢水平下降,体现出明显的延性破坏特征;②裂隙试件的峰值应力、弹性模量和峰值应变均有明显减小。峰值强度和弹性模量随裂隙夹角的增加呈先增大后减小的变化趋势。轴向峰值应变主要受裂隙夹角的影响,总体随夹角的增大呈线性减小的趋势;③裂隙的存在能够完全改变岩体试件的破坏模式,随着裂隙夹角的逐渐增加,裂隙试件破坏模式的演化过程为:台阶式张拉-剪切复合破坏(30°)→张拉-八字形剪切复合破坏(60°)→台阶式平行双斜面剪切破坏(90°)。当裂隙夹角为60°时,试件的裂纹演化和破坏模式体现出对加载方向近似的结构对称性特征;④相交裂隙试件单轴压缩破坏的弹性应变能、耗散能、总能量和能量耗散率均较完整试件有大幅度的减小。裂隙试件产生的裂纹数量越多,试件表面的脱落现象越明显,耗散能和能量耗散率也越大。拉-剪复合破坏比单纯剪切破坏要消耗更多的能量。试件的破坏特征和破坏模式能很好地反映试件的能量耗散特性。

Mechanical properties and failure mode of rock mass containing V-type intersecting fissures

In order to understand the mechanical properties and crack evolution of rock mass specimens con-taining V-type intersecting fissures,some conventional uniaxial compression tests on specimens containing V-type intersecting fissures with different intersection angles were carried out by using the MTS815 elec-tro-hydraulic servo control test machine.Based on the experimental results,the stress-strain curves,strength and deformation characteristics,crack evolution and failure modes,energy dissipation characteristics of specimens were analyzed in detail.The main conclusions were drawn as follows:① the stress-strain curves of fissured specimens enter the stage of crack initiation and propagation earlier than that of intact specimens,and show obvious stress drops before the peak stress is reached.In the stage of post-peak failure,the stress-strain curves of intact specimens drop rapidly,while those of fissured specimens fall multi-stage,and even horizontal extension slowly declines,showing obvious ductile failure characteristics.② The peak stress,modulus of elasticity and peak strain of the fissured specimens decrease obviously.Peak strength and modulus of elasticity increase first and then decrease with the increase of intersection angle.Axial peak strain decreases linearly with the increase of the intersection angle,which is mainly affected by the intersection angle of fissures.③ The existence of fissures can completely change the failure mode of the fissure.With the increase of intersection angle,the evolution process of the failure modes of specimens is:step-type tensile-shear complex failure(30°)→ tensile and splayed-shear complex failure(60°)→ step-type parallel double inclined plane shear failure(90°).When the intersection angle is 60°,the crack evolution and failure modes of the specimens show approximate structural symmetry relative to loading direction.④ The elastic strain energy,dissipated energy,total energy and dissipated energy rate of the fissured specimens under uniaxial compression are significantly lower than those of intact specimens.The more the number of cracks,the more obvious the surface shedding phenomenon,so then the greater the dissipated energy and dissipated energy rate.Tensile-shear complex failure consumes more energy than single shear failure.The failure characteristics and failure modes of the fissured specimens can well reflect its energy dissipation characteristics.