中等应变率下不同配比充填体的动态力学特征

Dynamic mechanical characteristics of backfill with different proportions under medium strain rates

通过设计6种较低的冲击气压对4种配比的充填体试件进行室内SHPB冲击试验来探究充填体的应力-应变曲线特征、动态抗压强度与应变率关系以及破坏模式。充填体取自云南玉溪大红山的分级尾砂,充填体的灰砂质量比分别为1∶4、1∶6、1∶8、1∶10。冲击气压分别为0.20 MPa、0.22 MPa、0.24 MPa、0.26 MPa、0.28 MPa和0.30 MPa。研究结果表明:1)从应力-应变曲线可以看出,CTB1∶4和CTB1∶6到达应力峰值后卸载较快,表现为脆性材料的变形特性,CTB1∶8比CTB1∶10达到应力峰值后卸载阶段较为缓慢,CTB1∶10最为平缓;2)当平均应变率由10 s^(-1)增至50 s^(-1)时,配比动态抗压强度增长趋势陡峭程度CTB1∶4最陡,CTB1∶10最缓。试件CTB1∶4动态抗压强度受应变率的影响最明显;3)在应变率不变条件下,CTB1∶10的峰值应变更大,易发生变形。对配比相同的试件,CTB试件的损伤破坏程度随着应变率提高而不断增大。随着平均应变率的增加,试件由一定数量的大碎块向细小碎块甚至向粉末状的方向转化;4)当矿山使用料浆质量分数为72%的尾砂充填体时,推荐灰砂配比范围选择1∶6~1∶4。

In this paper,the indoor SHPB impact test was carried out on the backfill specimen with 4 kinds of ratios by designing 6 kinds of lower impact pressure to explore the stress-strain curve characteristics of backfill,the relationship between dynamic compressive strength and strain rate and failure mode.The filling body was taken from the graded tailings of Dahongshan in Yuxi,Yunnan province.The cement-sand mass ratios of backfill were 1:4,1:6,1:8,1:10.The impact pressure was 0.20 MPa,0.22 MPa,0.24 MPa,0.26 MPa,0.28 MPa and 0.30 MPa,respectively.The results prove that:(1)It can be seen from the stress-strain curve that CTB1∶4 and CTB1∶6 are unloaded faster after reaching the stress peak,which shows the deformation characteristics of brittle materials.Compared with CTB1∶10,CTB1∶8 is slower in the unloading stage after reaching the stress peak,and CTB1∶10 is the most gentle.(2)When the average strain rate increases from 10 s^(-1) to 50 s^(-1),CTB1∶4 is the steepest,while CTB1∶10 is the slowest.The dynamic compressive strength of CTB1∶4 is most obviously affected by strain rate.(3)Under the condition of constant strain rate,the peak value of CTB1∶10 should change greatly and be prone to deformation.When the strain rate is in the range of 9.47-12.08 s^(-1),16.35-21.36 s^(-1),25.39-35.87 s^(-1),39.22-49.52 s^(-1),it is obvious that the failure degree of filling body with a higher ratio is smaller,and the failure degree of filling body specimen with the same ratio increases with the increase of strain rate.And with the increase of strain rate,the filling specimen changes from large fragments to fine fragments or even to powder.(4)When tailings filling body with a slurry concentration of 72%is used in the mine,1:6-1:4 is recommended as the ratio range of ash and sand.