高铁级配碎石振动压实下力学机制演化与颗粒破碎研究.pdf

第2 0 卷第9 期2023年9月D0I:10.19713/ki.43-1423/u.T20221989铁道科学与工程学报Journal of Railway Science and Engineering高铁级配碎石振动压实下力学机制演化与颗粒破碎研究Volume 20Number 9September2023谢康，陈晓斌，尧俊凯，王业顺，邓志兴！(1.中南大学土木工程学院，湖南长沙410 0 7 5；2.中国铁道科学研究院集团有限公司铁道建筑研究所，北京10 0 0 8 1)摘要：为准确表征出高铁级配碎石填料的压实过程，采用新型智能振动压实仪，分别从物理力学层面表征出级配碎石的压实过程。提出改进Viola-Jones算法量化出振动压实过程中级配碎石颗粒粒径、颗粒形状的演化规律，最后通过离散元方法揭示了振动压实中的颗粒破碎对级配碎石宏细观力学性能的影响机制。研究结果表明：在振动压实试验中，级配碎石的干密度在振动压实过程中不断增大，而力学性能K,却出现了“软化”的现象；级配碎石在振动压实前后级配没有明显变化，内部粗颗粒细长比变化也不明显，而圆度在压实后逐渐增加，表明级配碎石在振动压实过程中的颗粒破碎模式并非为颗粒被压碎，而是颗粒边缘突出、薄弱部位被分化、磨圆，可采用圆度来量化振动压实过程中颗粒破碎程度(研磨度)；试样强度随着研磨度的增加而逐渐减小，且呈现出三阶段演化机制：0.1 DF0.4时，试样强度损失较小；0.4 DF0.7时，试样强度出现明显损失；0.7 DF1.0时，试样强度没有明显损失。并通过颗粒平均配位数、滑动与转动等细观指标进一步揭示了振动压实中的颗粒研磨度对试样强度影响机制。研究成果可进一步揭示高铁级配碎石振动压实机理，也可为高铁路基智能压实控制技术奠定理论基础。关键词：高铁路基；振动压实；颗粒破碎；形状演化；力学特性；离散元法中图分类号：U215.4文章编号：16 7 2-7 0 2 9（2 0 2 3）0 9-32 17-12文献标志码：A开放科学(资源服务)标识码(OSID)Mechanical evolution and particle crushing under vibration compaction ofgraded gravel fill for high-speed railwayXIE Kang,CHEN Xiaobin,YAO Junkai,WANG Yeshun,DENG Zhixing(1.School of Civil Engineering,Central South University,Changsha 410075,China;2.Railway Engineering Research Institute,China Academy of Railway Sciences Co.,Ltd.,Beijing 100081,China)Abstract:In order to accurately characterize the compaction process of graded gravel fill for high-speed railway,a new intelligent vibration compaction instrument was used to quantity the properties of graded gravel fill fromthe physical mechanical aspects during the vibration compaction process.Moreover,the improved Viola-Jonesalgorithm was proposed to quantify the evolution of particle size and shape of the graded gravel fill during the收稿日期：2 0 2 2-10-12基金项目：国家自然科学基金资助项目（519 7 8 6 7 4)：中国铁道科学研究院集团重点课题（2 0 2 0 YJ143)：中国铁路设计集团重点课题(2020YY240606)；中南大学中央高校基本科研业务费专项资金资助项目(2 0 2 2 ZZTS0622)通信作者：陈晓斌(197 8 一)，男，江西赣州人，教授，博士，从事交通岩土工程研究；E-mail：c h e n _x i a o b i n c s u.e d u.c n3218vibration compaction.Finally,the influence mechanism of the particle crushing on the macro-micro mechanicalproperties of graded gravel fill during the vibration compaction was revealed by the discrete element method.Theresults show that in the vibration compaction tests,the dry density of graded gravel fill increases with the increaseof vibration time,while the mechanical property K,“softens with the increase of vibration time.The gradedgravel fill has no obvious change in gradation before and after vibration compaction.The slenderness ratio of theinternal coarse particles has no obvious change,while the roundness increases gradually after compaction.Thisphenomenon indicates that the particle crushing mode of graded gravel fill in vibration compaction is not that theparticles are crushed seriously,but that the particles are differentiated and rounded at the prominent and weakparts of the particle edges.The roundness can be used to quantify the particle crushing degree(friction degree)during compaction.The strength of the sample decreases gradually with the increase of the degree of grinding,and presents a three-stage evolution mechanism.When 0.1DF0.4,the strength loss of the sample is small.when 0.4DF0.7,the strength loss of the sample is obvious.When 0.75mm)基于体积相等原则替换为不同研磨度颗粒。基于自2023年9月10080一频率分布曲线%/明且一累积分布曲线604020000.81.0-Ri-压实前0.2100(d)8060402000.200.3圆度/工0.250.4-R-压实前一R-压实后R2-压实前R2-压实后0.300.35圆度0.40第9期编程序保证替换后的颗粒分布方向满足均匀分布，后分别开展研磨度为0.1，0.4，0.7 以及1.0 这4个工况的柔性膜双轴压缩试验。数值试验中采用linear接触本构模拟颗粒与颗粒、颗粒与墙体之间接触关系2 4。而在分析研磨度过程中，取颗粒间的摩擦因数为0.5，颗粒与墙体V(b)(a)谢康，等：高铁级配碎石振动压实下力学机制演化与颗粒破碎研究验标定获得，如图7 所示。模型细观参数如表1所示2 4，同时所标定出的刚度、刚度比与NIE等2 6-2 8 论文中路基填料细观参数基本相同。200(c)1503223间的摩擦力为0.12 4-2 1。其他参数通过室内三轴试数值结果试验结果口剪胀100-6050V(a)三轴试验；(b)三轴试验数值模拟；(c)结果对比(围压2 0 0 kPa)图7 离散元参数标定Fig.7Discrete element parameter calibration表1DEM模型细观参数Table 1Parameters used in the DEM simulation参数颗粒密度/(kgcm)颗粒-颗粒法向刚度/Pa颗粒-墙法向刚度/Pa刚度比，k/k颗粒-颗粒摩擦因数颗粒-墙体摩擦因数局部阻尼系数图8 展示了试样生成过程、等效压缩过程、颗粒替换过程以及剪切过程，详细的建模过程如下：1)颗粒生成。首先在BxH的矩形区域内随机生成研磨度为1.0 的圆形颗粒，如图8 所示，填料颗粒的颗粒根据级配(见图1)、临时孔隙率0.8 和矩形区域面积而定。2)墙体压缩。采用边界压缩法对墙体进行等向压缩，其中上下墙体以Vc(0.1xH)速度、左右侧墙以1/2 Vc速度往中心运动。等向压缩过程中，当作用于墙体上的应力达到2 0 0 kPa，且颗粒系统中平均不平衡力与平均接触力之比小于10 时停止等向压缩过程2 5。03）颗粒替换。遍历粒径大于5mm的颗粒，并将粒径大于5mm的圆形颗粒分别替换为不同研磨模拟值度的Clump颗粒，实现同位置、同粒径的不规则2.650Clump替换。通过clump.rotate函数将不同模型中1108的Clump颗粒旋转，使得颗粒分布角度满足均匀2108分布，再次伺服至动态平衡。1.254)柔性膜伺服压缩。用柔性膜替换左右刚性0.5壁，柔性膜颗粒采用Linear-parallel-bond模型，为0.1了保护柔性膜不被刺穿，黏结颗粒应具有一定的0.7初始重叠量，黏结单元颗粒的球心距设为单元颗粒直径(膜厚度)的0.7 2 倍，最终通过伺服机制将围压施加在柔性膜颗粒上2 9。5)试样加载。将颗粒-颗粒之间摩擦因数设为0.5，局部阻尼设为0.7。停止上下加载墙的伺服，保持左右柔性膜伺服，围压固定在2 0 0 kPa。剪切速率设为0.0 1m/s，使得数值试验中惯性参数I,小于10-，满足准静态加载要求。当轴向应变为15%，停止剪切。3.2宏观力学特性通过应力比、体变2 4规律来研究颗粒破碎引起的圆度演化对粗粒土填料宏观力学性质的影响。不同研磨度试样的应力比与轴向应变曲线如图9所示。24轴向应变/%6810123224铁道科学与工程学报2023年9月真实颗粒形状(a)理想颗粒形状研磨度10.1(b)0.40.71.0V个V试样生成1.51.20.90.60.30从图9中可以看出加载初始阶段，应力比均随着轴向应变呈现线性增加，且在较小的轴向应变便达到峰值。峰值应力之后，应力比逐渐减小最终达到残余抗剪强度。随着破碎程度的增加，试样的峰值强度和残余强度逐渐下降，可见颗粒研磨度越大，颗粒越光滑，颗粒之间的咬合作用越弱。同时，强度下降速率随研磨度(DF)呈现出3个不同阶段：0.1DF0.4时，试样峰值强度和残余强度损失较小；0.4DF0.7时，试样峰值强度和等压固结(a)振动压实下真实颗粒研磨度演化；(b)建模过程图8 模型建立Fig.8 Model building50(b)口4540(。)/潮3530-0.10.4一0.7-1.00.030.06轴向应变(a)应力比随轴向应变演化规律；(b)内摩擦角随破碎程度演化规律图9不同研磨度试样的应力应变关系Fig.9 Stress-strain relationship of samples with different grinding degrees残余强度出现明显损失；0.7 DF1.0时，试样峰值强度和残余强度没有明显损失。基于图9(a)数据，图9(b)量化出了不同研磨度试样的峰值内摩擦角和残余内摩擦角的变化规律。由图可知，随着研磨度增加，峰值内摩擦角和残余状态逐渐减低，且降低速率分布同样符合上述的3个阶段。图10 为不同研磨度颗粒试样体积变形演化规律。由图可知，不同研磨度下在加载初始阶段发生了较小的体积收缩，之后随着加载进行都迅速颗粒原位替换25200.090.12柔性膜伺服0.150剪切压缩一一峰值内摩擦角一o一残余内摩擦角0.20.4研磨度0.60.81.0第9期产生了明显的体积膨胀，研磨度的减小会影响体积应变变化的模式，当DF在0.7 1.0 之间，试样很快发生了明显的体积膨胀，但是趋于稳定时所对应的轴向应变则较小。主要原因在偏球形颗粒的试样内部颗粒之间的咬合作用很弱，试样内部谢康，等：高铁级配碎石振动压实下力学机制演化与颗粒破碎研究3225-0.14一一0.1一0 0.4-0.10一一 0.7-1.0K-0.06迅速发生重排布且迅速稳定。当DF在0.10.7 之间时，体积变化趋于稳定的速度也变慢，同时在临界状态时的体积变化呈现增加趋势。主要原因在于随着研磨度的减小，颗粒的相对运动会受到周围颗粒的约束，颗粒运动变得困难，运动中伴随着更多的翻越、错动，试样内部稳定的速度变慢。3.3细观机理3.3.1平均配位数配位数2 4表示颗粒周围接触的颗粒的数量，可直接量化出颗粒体的密实程度，也可以描述剪切过程中的颗粒重分布情况，进一步，采用配位数变异系数CV(Z)，量化出颗粒分布的不均匀程度和混乱程度，计算方法如下：CV(Z)=(Z-2)NpSD,=V台N式中：N,为颗粒个数；Z,为第i个颗粒的配位数；SD,为配位数的标准差。3.5(a)3.02.52.01.51.000.02 0.04 0.06 0.08 0.10 0.12 0.14Fig.11 Variation law of average coordination number of samples with different grinding degrees3.3.2颗粒运动分析级配碎石作为典型的颗粒材料，颗粒受力运-0.020.020图10 不同研磨度试样体积变形演化规律Fig.10Evolution law of volume deformation of sampleswith different grinding degrees图11(a)展示了不同研磨度试样平均配位数变化规律。总体看来，平均配位数在剪切初期迅速下降，后下降速率减缓直至稳定，反映出试样内部由密实状态变为松散状态，试样的体积逐渐增加，这与图11的试样体积变形演化规律一致。图SD,11(b)显示了不同研磨度试样平均配位数变异性，(6)当0.1DF0.7时，颗粒棱角越少，试样结构内部越均匀，而值得注意的是，若0.7 DF后，试样内(7)部颗粒混乱度增加，这说明偏光滑、圆形颗粒，颗粒间的咬合作用对配位数的变化不敏感，颗粒间的咬合作用对棱角度较多的颗粒较为敏感。0.24(b)一口0.1口-00.4 0.7-v-1.0轴向应变(a)平均配位数；(b)平均配位变异系数图11不同研磨度试样平均配位数变化规律剪胀剪缩0.030.06轴向应变一口一峰值状态一o一残余状态0.200.160.120.08动，主要包括2 类运动形式，即颗粒滑动(位置改变)和滚动(旋转)，颗粒滑动的增强常导致滚动减0.0910.20.120.40.6研磨度0.150.81.03226弱3。图12(a)展示了不同研磨度试样滑动率与轴向应变的关系曲线。由图可知，随着轴向应变的增大，滑动率先急剧增大，后逐渐减小至稳定。随着研磨度越小，滑动率越大，说明颗粒形状越不规则，颗粒之间的滑动接触的比例相对较多，颗粒之间的转动受限，运动更多以滑动形式进行。图12(b)展示了不同研磨度颗粒试样转动量的变化(a)-一0.1 0.40.4一一0.7一-1.00.30.20.104结论1)振动压实试验出现了级配碎石的干密度随振动时间增大而增加，而力学性能K,却随振动时间增加而“软化”的现象。2)级配碎石在振动压实前后级配没有明显变化，内部粗颗粒细长比变化也不明显，而圆度压实后增加，表明高铁级配碎石振动压实中颗粒破碎模式并非颗粒被压碎，而是在颗粒边缘突出、薄弱部位被分化、磨圆。3）试样强度随着研磨度的增加而逐渐减小，且呈现出三阶段演化机制：0.1 DF0.4时，试样强度损失较小；0.4 DF0.7时，试样强度出现明显损失；0.7 DF1时，试样强度没有明显损失。4)随着试样颗粒研磨度的增加，平均配位数减小，而滑动率逐渐提高，颗粒旋转量逐渐降低，进一步揭示了研磨度对试样强度影响的细观机制。参考文献：1叶阳升，蔡德钩，张千里，等.高速铁路路基工程关键技铁道科学与工程学报规律。随着加载进行，颗粒转动逐渐增加，并且呈线性增加趋势，在应力较大时仍没有收敛现象，说明剪切过程中颗粒一直处于旋转状态，进而产生塑性变形适应轴向应变。随着研磨度减小，颗粒的相对运动会受到周围颗粒的约束，周围颗粒容易限制其转动，运动中伴随着更多的翻越、错动，滑动范围增大。10(b)8pe/鲁转迷6420.0300.060.09轴向应变图12 不同研磨度试样颗粒运动变化规律Fig.12Variation law of particle motion of samples with different grinding degrees22(5):35-40.2DUONG T V,CUI Yujun,TANG A M,et al.Effects ofwater and fines contents on the resilient modulus of theinterlayer soilofrailway substructureJ.ActaGeotechnica,2016,11(1):51-59.3张家玲，徐光辉，蔡英.连续压实路基质量检验与控制研究J.岩土力学,2 0 15,36(4):1141-1146.ZHANG Jialing,XU Guanghui,CAI Ying.investigation on quality inspection and control forcontinuously compacting 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