基于3D打印和FDEM算法的层状岩体力学特性研究

Study on mechanical properties of layered rock mass based on 3D printing technology and FDEM algorithm

为探究层状岩体的强度和变形破坏特征随层理倾角和试样尺寸等因素的变化规律,利用粉末黏结成型3D打印技术制作涵盖多种倾角和尺寸的层理试样,并开展单轴压缩和巴西劈裂试验,利用有限元-离散元耦合算法(FDEM)对室内试验结果进行验证。研究结果表明:(1)抗压强度、弹性模量和变形模量随层理倾角呈“U”型变化,倾角90°试样的测试结果明显大于其他角度的;抗拉强度与层理倾角呈负相关关系,倾角0°试样的抗拉强度明显小于均质试样。(2)单轴压缩试样呈现张拉主导型(0°和90°)和剪切主导型破坏(5°和67.5°);随着层理倾角的逐渐增大,试样逐渐由延性破坏过渡到脆性破坏;巴西劈裂试样均呈现张拉破坏,裂隙走向呈直线型(0°和90°)和弧线型(45°)。(3)随着试样尺寸的逐渐增大,抗压强度逐渐趋于稳定,峰值应变逐渐减小并稳定在0.005左右;抗拉强度随试样尺寸呈倒“U”型变化,弹性模量和变形模量随试样尺寸在2.1 GPa附近波动,三者均未呈现稳定趋势。

To explore how the strength,deformation and failure characteristics of layered rock mass change with bedding angle and specimen scale,3D printing technology is adopted to produce bedding specimens of different angles and scale,and the uniaxial compression test and Brazilian splitting test are conducted.Besides,the combined finite-discrete element method(FDEM)is employed to testify the laboratory results.Three findings are reported as below.Firstly,compressive strength,elastic modulus and deformation modulus have a“U-shaped”curve relationship with bedding angle,respectively.When bedding angle is 90°,the values of these three factors are obviously higher than the results under the condition of other bedding angles.Tensile strength has a negative correlation with bedding angle.When bedding angle is 0°,the tensile strength is apparently lower than that of homogeneous specimens.Secondly,the specimens subjected to uniaxial compression load feature tension-dominated failure(with the bedding angles of 0°and 90°)and shear-dominated failure(with the bedding angles of 45°and 67.5°).As bedding angle increases,failure mode gradually transits from ductile failure to brittle failure.The specimens suffering from Brazilian splitting test show tension-dominated failure and the fractures assume linear-type(with the bedding angles of 0°and 90°)and arc-type(with the bedding angle of 45°).Lastly,as specimen scale gradually increases,compressive strength tends to be stable and peak strain decreases gradually and tends to stabilize around 0.005.Tensile strength and specimen scale have an“inverted U-shaped”curve relationship,elastic modulus and deformation modulus fluctuates around 2.1 GPa,and these three factors don't show stable tendency.