基于三维扫描技术的土石混合体离散元模型参数反演及直剪模拟

Parameter Inversion and Direct Shear Simulation of Discrete Element Model of Soil-Rock Mixture Based on 3D Scanning Technology

利用三维扫描技术构建不同粒径的真实块石形状数据库,并建立不同含石量的土石混合体离散元随机模型。采用正交试验设计原理,分析试样宏细观参数间力学敏感性并建立两者的线性方程,结合物理试验对模型进行参数标定。对不同法向应力、不同含石量的土石混合体进行直剪模拟,结果表明:岩土体在剪切过程中,剪应力逐渐增大,变形先剪缩后剪胀;增加法向应力,试样抗剪强度提高,剪缩程度增大,但初始模量变化微弱;低含石量下剪力无明显峰值,应变硬化现象显著,变形以剪缩为主,随着含石量增加,初始模量及抗剪强度升高,高含石量下出现应力峰值,之后表现为应变软化,剪胀性突出。土石混合体增加法向应力或含石量,均会提高其初始配位数和力链强度,其中增加法向应力,配位数整体水平上升;在剪切过程中,低含石量下配位数呈递增趋势,高含石量下配位数逐渐减小,配位数不会持续增或减,当达到临界值时与试样体积一同趋于稳定;含石量越大剪切带越宽厚,剪切面周围速度及位移变化梯度较大,剪切中后期试样内出现逆时针涡旋速度场;动剪切盒内配位数较大,静剪切盒内配位数较小,剪切带处配位数波动幅度最大;岩土体中弱力链散乱稀疏,强力链分布集中,剪切时力链强度先增大后减小,逐渐发散变粗并沿对角线延伸,最终贯穿剪切区域。

Based on three-dimensional scanning technology,the databases with the real rock blocks shape of different particle sizes and discrete element models of soil-rock mixture(S-RM)samples with different stone contents were established.Mechanical sensitivity between the macro-meso parameters was analyzed and the linear equations were built according to the principle of orthogonal test design,calibrating meso-para-meters for the discrete element model by mechanic tests data.The large-scale numerical shear tests of the stone contents S-RM samples under different normal stresses were conducted.The results show that:the shear stress increases gradually and the volume deformation first contraction and then dilatancy during the shear process.It is noteworthy that with the increase of normal stresses,the peak strength and shear contraction deformation all increase,but the initial modulus changes slightly.The S-RM has no obvious peak strength under low contents of stone,and then the phenomenon of strain hardening is significant and shearing is the mainly deformation.The initial modulus and shear strength increases with the increase of stone content.For S-RM with high contents of stone,the peak stress occurs and then shows strain softening and prominent shear dila-tancy deformation in the late shear.The strength of force chain and initial coordination number of S-RM increases with the increase of either the stone contents or the normal stress.The increase of normal stress increase the overall level of coordination number.In shearing process,for S-RM with low contents of stone,the coordination number increase gradually with the increase of shear displacement,while the trend decreases for the stone contents of S-RM with high decreases.The fluctuation of coordination number and sample volume tends to be stable when reach to the critical value.As the stone content increases continually,the shear zone of the S-RM sample becomes wider,the gradient of velocity and displacement around the shear plane increases.A counter-clockwise vortex velocity field appears in the samples during the mid-to-late shear.The coordination number of dynamic shear box large compared to that of static shear box,and the coordination number in the shear zone fluctuates the most.In the S-RM,the weak force chain is scattered and sparse,while the strong force chain is concentrated.During the shear process,the strength of force chain increases first and then decreases.With the diverges and thickens of force chain,eventually the locally force chain are connected to each other diagonally.