摘要
为了研究岩石不连续面的拉剪力学行为,采用自主研制的拉剪装置开展天然灰岩层面在法向拉应力作用下的直剪试验,分析了剪切应力-位移曲线、层面断裂形态及强度特征。拉剪应力作用下断裂面无摩擦粉碎区和局部崩裂。随法向拉应力的增加,剪切强度呈非线性减小。进一步,采用PFC模拟研究了锯齿状层面起伏特征对其拉剪破裂及强度特性的影响。随法向拉应力的增大,剪切裂纹减少而拉伸裂纹增多。当起伏角较小时,裂纹沿锯齿层面产生;当起伏角较大时,裂纹在锯齿面和锯齿内均有发生。可将锯齿状层面破坏分为沿锯齿面拉伸-剪切破裂、沿锯齿面拉伸-拉剪破裂和锯齿面-锯齿混合破裂3种模式,并具体分析了各模式的损伤演化。随起伏角增大,锯齿状层面的剪切强度先减小后增大,在起伏角为30°时达到最小值;随法向拉应力的增大,剪切强度近似线性减小,可采用Mohr-Coulomb准则进行描述,其摩擦角和黏聚力随起伏角的增加而减小。剪切强度、摩擦角和黏聚力随起伏角的变化规律主要受破裂模式的控制。随着层面黏结强度的增加,从锯齿面破裂逐渐转变为锯齿面-锯齿混合破裂。当层面黏结强度达到一定值以后,拉剪强度不再增加,主要受锯齿的岩石强度控制。
In order to study the tensile-shear behavior of rock discontinuities,the self-developed tension-shear device was used to carry out the direct shear test of the natural limestone bedding planes under normal tensile stresses,and the shear stress-displacement curves,the bedding plane fracture morphologies and strength characteristics were analyzed.The fracture surfaces have no friction crushing zone and local split under a tensile-shear stress.The shear strength decreases nonlinearly with the increase of normal tensile stress.Further,PFC simulation was used to study the influence of saw-tooth bedding plane undulation characteristics on its tensile-shear rupture and strength characteristics.As the normal tensile stress increases,the shear cracks decrease and the tensile cracks increase.When the undulation angle is small,cracks are generated along the saw-tooth bedding planes;when the undulation angle is large,cracks are generated along the saw-tooth bedding planes and saw-tooth.The saw-tooth bedding plane failure can be divided into three modes:tensile and shear ruptures along the saw-tooth planes,tensile and tensile-shear ruptures along the saw-tooth planes,and mixed saw-tooth plane and saw-tooth ruptures.And the damage evolution of each failure mode was analyzed.The shear strength of the saw-tooth bedding planes decreases first and then increases with the increase of the undulation angle,and the minimum is at 30°.It decreases almost linearly with the increase of the normal tensile stress,which can be described by the Mohr-Coulomb criterion.The friction angle and cohesive force decrease with the increase of the undulation angle.The variation of shear strength,friction angle and cohesion force with undulation angle is mainly controlled by the failure mode.With increasing levels of adhesive strength of bedding plane,the saw-tooth plane rupture is gradually converted into a mixed saw-tooth plane and saw-tooth ruptures.When the adhesive strength reaches a certain level,tensile-shear strength no longer increases,mainly controlled by the strength of the saw-tooth rock.
作者
岑夺丰
刘畅
黄达
CEN Duo-feng;LIU Chang;HUANG Da(School of Civil and Transportation Engineering,Hebei University of Technology,Tianjin 300401,China)
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2022年第S01期77-87,96,共12页
Rock and Soil Mechanics
基金
国家自然科学基金(No.41807279)
河北省自然科学基金(No.E2019202336)
天津市自然科学基金(No.20JCQNJC00980).
关键词
岩石力学
层面
拉剪
起伏角
颗粒流模拟
rock mechanics
bedding plane
tensile-shear
undulation angle
particle flow simulation
