根系固土抗蚀受损后自我修复的力学特性

In present, there are many reports about root soil-fixation research, which take taproot as the object, and take the ultimate tension to calculate mechanical characteristics when the root ruptures. But there is no report about the following issues, when living root is in elastic-plastic deformation condition under load, whether or not this root has the ability of self-repair,whether or not differences exist between taproot and roots node. This study uses mechanics of materials,elastic-plastic mechanics and soil mechanics to research mechanical charicteristics and differences between taproot and root node under strong wind or soil collapse.Soil collapse generates from three kinds of load:tension,bending and wreckage. These three plants are Caragana microphylla Lam., Hippophae rhamnoides Linn. and Artemisia sphaerocephala Krasch., these three plants are common plant species in revegetation in Inner Mongolia.The mechanical characteristics and windbreak effect of these three plants are typical. From the view of perennial root and final root, and perennial roots node and final root, the self-repair of single root mechanical characteristics of three plants is researched under one more load. Plant roots suffer different degrees of instantaneous drawing force，continuous lateral load，horizontal and vertical displacement，to research the availability of root self-repair and mechanical characteristic. This study will find the mechanical characteristics of three plants roots, and the difference between taproot and root node.

目前，根系固土机制的研究均针对直根，以断裂时的极限拉力为依据。但是，活根在受力处于弹塑性变形状态，是否具有自我修复能力，根节点和相邻直根的力学特性是否存在差异，均无研究报道。本课题采用材料力学、弹塑性力学、土力学原理和试验方法，研究内蒙古中部普遍种植，根系力学特性和地上部分防风作用有代表性的三种植物- - 柠条、沙棘、白沙蒿在大风拉拔力作用，土体坍陷使根系受拉、受弯或折断的三类荷载作用下，根节点和相邻直根力学特性的差异及其力学指标；从多年生根和末级细根层面、多年生根节点和末级根节点层面，研究三种植物单根在承受未达到极限荷载的各类外力作用后，自我修复的可能性，以及自我修复后再次承受各类荷载时的力学特性；研究单株根系网，在不同程度的瞬时拉拔力、持续侧向荷载、水平和垂直位移作用后，整株根系自我修复的有效性和修复后的力学特性。阐明三种植物根系受损后自我修复的力学机制，以及直根段和根节点力学特性的差异。

针对柠条、沙柳、沙棘研究径级1-5mm不离体直根和侧根分支处分别承受2种程度轴向损伤力（相当于每一试验径级根平均极限抗拉力的30%和70%），自修复3个月的存活特性和对极限抗拉力的影响；及分别承受3种程度的径向损伤力（极限抗折力的30%、50%和70%）自修复3个月的存活特性和对极限抗折力的影响。研究整株柠条、沙柳、沙棘、白沙蒿根-土复合体分别承受该植物根土复合体平均极限剪力25%、50%和75%的损伤剪力，自修复3个月的存活特性和对根土复合体抗剪特性的影响。主要结论：根系承受该径级极限力70%的拉力或折力自修复3个月存活率超过60%，根径较受损时增加。直根、含侧根分支处根段承受极限拉力70%的损伤力自修复3个月与施力时对照相比，极限抗拉强度变化率为柠条10%和-4%、沙柳17%和12%、沙棘-28%和-24%；与平行对照相比两种根段极限抗拉强度下降率为柠条21%和30%、沙柳21%和29%、沙棘53%和54%。损伤力为极限折力的70%，自修复3个月直根和侧根分支处的极限抗折强度与平行对照相比，减小率为柠条15%和18%、沙柳14 %和19%、沙棘23%和30%。侧根分支处承受平均极限折力70%的损伤力自修复3个月，柠条抗折强度为受损直根的65%、沙棘为53%，沙柳直根与侧根分支处抗折强度差异不明显。4种植物根土复合体承受极限剪力75%的损伤力自修复3个月存活率大于83%，极限抗剪强度与残余强度比平行对照减少：沙柳17%和18%、柠条23%和31%、沙棘25%和28%、白沙蒿32%和27%。根系自修复5个月的各项强度均高于自修复3个月。单根受拉、受折自修复能力排序为沙柳与柠条相近，均高于沙棘；但整株根土复合体受剪自修复能力为柠条和沙棘相近，沙柳明显优于二者。单根两个部位正常生长和受力受损自修复后极限抗拉、抗折强度均为柠条>沙柳>沙棘，但整株根土复合体未受损及受损自修复后的抗剪强度均为沙柳>柠条>沙棘。4种植物侧根分支处根径平均为相邻上级直根根径的（103-109）%，但极限抗折强度小于相邻上级直根。