层理面特性对砂岩断裂力学行为的影响研究  

Study on the influence of bedding plane on fracturing behavior of sandstone

作　　者：李斌[1] 黄达[1,2] 马文著 LI Bin;HUANG Da;MA Wen-zhu(State Key Laboratory for Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400044,China;School of Civil Engineering and Transportation,Hebei University of Technology,Tianjin 300401,China)

机构地区：[1]重庆大学煤矿灾害动力学与控制国家重点实验室,重庆400044 [2]河北工业大学土木与交通学院,天津300401

出　　处：《岩土力学》2020年第3期858-868,共11页Rock and Soil Mechanics

基　　金：国家自然科学基金面上项目(No.41672300)。

摘　　要：层理弱面对层状岩石的力学特性影响较显著,为了研究层理面特性对岩石断裂力学特性的影响,开展了具有不同层理方向的砂岩试样三点弯试验,探讨了砂岩断裂韧度及断裂模式的各向异性。之后基于有限元中的黏聚单元建立了数值模型,采用数值模拟方法研究了层理面强度对各层理角度试样断裂力学行为的影响规律。结果表明:层理方向影响下砂岩的断裂韧度及模式存在各向异性;同一层理方向试样的断裂韧度随层理面强度的增大而增大,且试样的层理面与加载方向夹角越小,断裂韧度受层理面强度变化影响越明显;试样的断裂模式不仅与层理面强度有关,还受层理倾角的控制,层理面与加载方向夹角θ=0o试样断裂模式基本不受层理面强度影响,θ=30o试样主要沿层理面张拉或剪切破坏,且沿层理面的破裂长度随层理面强度的降低逐渐增大;层理面强度较大时,θ=45o试样主要沿层理面张拉破坏,θ=60o^90o试样主要以贯穿层理的张拉破坏为主;层理面强度较小时,θ=45o^90o试样均以沿层理面的剪切破坏为主,其中θ=45o试样沿层理剪切长度最大。另外,通过数值模拟结果分析了层理面强度及方向对试样的起裂角及裂纹扩展路径产生的影响。该研究成果可作为层状岩石断裂力学理论的有益补充。The mechanical behavior of layered stone is much influenced by the weak bedding planes.To further explore how the layered structure influences the fracture characteristic of layered sandstone,a series of three-point-bending tests on sandstone specimens with different inclination angles was conducted and the anisotropy of fracture toughness and fracture pattern was discussed.Then a numerical model based on cohesive elements was proposed to simulate the fracture of semi-circular sandstone specimens under three-point-bending test and the effects of bedding strength on the fracturing behavior of semi-circular bending(SCB)specimens with different inclination angles were discussed by simulation with the proposed model.The results show that fracture toughness and fracture pattern are anisotropic under the influence of the inclination angle of the bedding and fracture toughness increases with the increase of bedding strength for a fixed inclination angle.In addition,the influence of joint strength on the fracture toughness is greater for lower inclination angles and the fracture patterns are not only influenced by joint strength,but also related to the inclination angle.Fracture patterns ofθ=0o specimens are almost not influenced by the joint strength,and the specimens all split along the bedding plane with tensile failure;tensile or shearing failure along the bedding plane occurs onθ=30o specimens and the crack length along the bedding plane increases with the decrease of joint strength;when the joint strength is higher,tensile failure along the bedding plane occurs onθ=45o specimens and tensile failure crossing the bedding plane occurs onθ=60o-90o specimens,while shearing failure along the bedding plane occurs onθ=45o-90o specimens when the joint strength becomes lower.Furthermore,the maximum shearing length occurs onθ=45o specimens.In addition,the impacts on the crack initiation angle and crack propagation path caused by both bedding strength and inclination angle are discussed based on the numerical results.The

关 键 词：半圆形砂岩试样 三点弯试验 黏聚单元 层理方向 层理面强度 断裂力学行为 

分 类 号：TU452[建筑科学—岩土工程]