含混杂纤维尾砂胶结充填体静态力学性能试验研究

Experimental Study on Static Mechanical Properties of Cemented Tailings Backfill with Hybrid Fiber

为探究钢纤维(SF)与聚丙烯纤维(PF)混杂后对尾砂胶结充填体静态力学性能及破坏模式的影响,采用电子万能试验机和扫描电镜分别对含混杂纤维尾砂胶结充填体进行单轴压缩试验和微观测试。结果表明:混杂纤维的掺入对充填体破坏模式有显著影响,无纤维充填体(CTB)最终以单斜面剪切破坏为主,呈明显的脆性破坏,而掺混杂纤维充填体(SP-FRB)因内部纤维的桥连和阻滞效应,最终破坏以较多的微小次生裂纹为主,试件整体裂而不断,表现出明显的延性变形;混杂纤维的掺入能够提高充填体的单轴抗压强度,但纤维含量存在最佳值;CTB及SP-FRB的应力-应变曲线均存在孔隙压密、线弹性变形、塑性屈服和破坏四个阶段。微观测试结果表明:充填体内部初始孔隙的数量和大小是破坏失稳的重要因素,钢纤维和聚丙烯纤维能够在充填体内保持较高的完整性,并分别通过与基体间的黏结力和自身疲劳断裂阻滞裂缝的扩展。

With the aid of an electronic universal testing machine and a scanning electron microscope,uniaxial compression tests and microscopic examinations of cemented tailings backfill with mixed fibers were carried out in order to investigate the impact of mixing steel fiber(SF)and polypropylene fiber(PF)on the static mechanical properties and failure mode.The findings demonstrate that:the inclusion of hybrid fiber has a substantial impact on the failure mode of the backfill;the CTB is mostly damaged by single bevel shear,displaying an evident brittle failure;the SP-FRB is primarily damaged by relatively minor secondary cracks due to the bridging and crack-resisting action of internal fibers;and the specimen is fractured as a whole,demonstrating an obvious ductile deformation;The addition of hybrid fiber can increase the filler′s uniaxial compressive strength,but there is a maximum amount that should be used.The stress-strain curves of both CTB and SP-FRB contain four stages:pore compaction,linear elastic deformation,plastic yield,and post-failure.The results of the microscopic tests indicate that the initial pore size and number inside the filler are significant factors in its failure.Steel fiber and polypropylene fiber can both maintain high integrity inside the filler and prevent crack expansion through adhesion with the matrix and their own fatigue fracture,respectively.