节理对砂岩变形及破坏特征影响研究

工程岩体一般都含有各种不同级别的地质构造节理和软弱面,使得岩体的强度弱化。含有节理的岩体和完整岩石具有完全不同的力学性质。本文在三轴压缩试验的基础上,对不同节理倾角的三峡库区砂岩开展研究,探讨其变形及破坏特征。试验结果表明:①在同种围压下,节理岩样峰值强度的大小关系为:σ_60°<σ_30°<σ_90°<σ_完整。②相同围压下,完整岩样弹性模量及变形模量均高于节理岩样,随着围压升高,岩样弹性模量和变形模量逐渐增大,其增长速度随围压增大而逐渐降低。③在低围压下(＜5 MPa),节理倾角对岩样弹性模量和变形模量影响较大,相比完整岩样有较大幅度地降低,其中30°倾角和60°倾角岩样降低程度较高,弹性模量最高达31%,变形模量最高达40%;随着围压增大(大于10 MPa),节理倾角对岩样变形参数影响逐渐减小,相比完整岩样,节理岩样弹性模量降低幅度小于15%,变形模量降低幅度小于10%。④节理倾角和围压对岩石的破坏机制均有较大的影响,节理倾角及围压不同,岩样破坏形式不同。

Influence of Joint on Deformation and Failure Characteristics of Sandstone

Engineering rock mostly contains a variety of different levels of geological tectonic joints and soft surface,weakening the strength of rock mass.Intact rock and rock containing joints have different mechanical properties.Based on triaxial compression tests,the effects of different joint angles on the deformation and failure characteristics of sandstone in the Three Gorges Reservoir Area were studied.The test results show that:①Under the same kind of confining pressure,the peak strength relationship of different jointed rock samples is σ60° ＜σ30° ＜σ90° ＜ σcomplete· ②Under the same confining pressure,elastic modulus and deformation modulus of complete rock samples are higher than that of jointed rock samples.With the confining pressure increasing,the elastic modulus and deformation modulus increase gradually.And the growth rate decreases with the confining pressure gradually increases.③In the case of low confining pressure (＜5 MPa),joint angles have great influence on both elastic modulus and deformation modulus,which decreases significantly compared with intact samples.The reduction degree of elastic modulus and deformation modulus of 30 ° and 60 ° tilt angle rock samples is significant,as the elasticity modulus up to 31％,deformation modulus up to 40％.As confining pressure increases (greater than 10 MPa),the influence of joint angle on deformation parameters of rock sample gradually reduces.Compared with complete rock sample,the reduction rate of elastic modulus is less than 15％,and the deformation modulus is less than 10％.④The joint angle and confining pressure both have greater impacts on the rock failure mechanism,and different joint angle and different confining pressure lead to different forms of destruction.