Optimization analysis of layered materials of composite filling body beside gob-side entry retaining
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摘要:
沿空留巷巷旁充填体分为让压层和抗压层，让压层材料应具有大变形的特性，减缓基本顶岩梁的剧烈活动；抗压层材料应具有强度高、刚性大等特点，柔性让压之后实现对上覆岩梁的有效控制。因此对让压层和抗压层材料的不同配比进行力学特性分析，并通过电镜扫描（SEM）对让压层和抗压层的对照组和优化组进行微观结构分析，最后对让压层和抗压层的最优配比进行组合试验。研究结果表明：让压层材料的最优配比为水灰质量比1.5∶1，发泡剂掺量0.06%，纤维掺量0.2%；优化组28 d时抗压强度达到了8.84 MPa；不同期龄下的应变力，优化组为对照组的1.8～2.6倍。抗压层材料配比中细矸率为40%，料浆质量分数78%，水泥掺量为20％时为最优，其平均抗压强度为13.21 MPa，抗拉强度为0.97 MPa，弹性模量为0.75 GPa，内摩擦角为26°，黏聚力为2.85 MPa；该配比下的充填体随着水泥掺量的增加后期强度逐渐增大。组合试件中让压层占比10%～20%时，具有较好的让压能力，也具有一定的关键承载能力。研究结果为沿空留巷巷旁充填体材料配比提供了参考。
Abstract:Along the hollow stay lane roadside filling body is divided into letting pressure layer and compression layer, letting pressure layer material should have the characteristics of large deformation, slow down the violent activities of the basic roof rock beam. The compressive layer material should be characterised by high strength and rigidity, and effective control of the overlying rock beams should be achieved after flexible letting pressure. Therefore, this paper analyzes the mechanical properties of different ratios of yield layer and compressive layer materials, and analyzes the microstructure of the control group and optimization group of yield layer and compressive layer by scanning electron microscope ( SEM ). Finally, the optimal ratio of yield layer and compressive layer is tested. The results of the study showed that the optimum ratio of the material for letting the compaction layer was 1.5:1 for the water-cement ratio, 0.06% for the blowing agent dosage and 0.2% for the fibre dosage. The compressive strength of the optimised group reached 8.84 MPa at 28 d. Strain at different ages was 1.8 to 2.6 times higher in the optimised group than in the control group. The compressive layer material ratio of 40% fine gangue rate, slurry mass concentration of 78%, cement dosage of 20% is optimal, the average compressive strength of 13.21 MPa, tensile strength of 0.97 MPa, modulus of elasticity of 0.75 GPa, the angle of internal friction of 26°, cohesion of 2.85 MPa. The filler at this ratio showed a gradual increase in strength with the increase in cement dosage in the later stages. When the yield layer accounts for 10%−20% of the composite specimen, it has good yield capacity and certain key bearing capacity. The research results provide a reference for the material ratio of roadside filling body in gob-side entry retaining.
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图 2 不同期龄下单轴压缩应力−应变曲线及割线模量拟合曲线
Figure 2. Uniaxial compressive stress-strain curve and secant modulus fitting curve at different ages
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图 3 对照组与优化组试件压缩破坏后对比
Figure 3. Comparison between control group and optimized group after compression failure
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图 4 对照组试件能谱面扫和元素分布形态
Figure 4. Energy spectrum surface scan and element distribution pattern of control group specimens
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图 5 优化组试件能谱面扫和元素分布形态
Figure 5. Specimen energy spectrum surface scan and element distribution pattern of optimization group
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图 8 不同因素对不同期龄下充填体强度的影响
Figure 8. Influence of different factors on strength of filling body under different ages
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图 10 煤矸石胶结充填体不同期龄下SEM及EDS图片
Figure 10. SEM and EDS images of coal gangue cemented backfill at different ages
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图 12 不同分层占比下复合充填体试件的应力−应变曲线
Figure 12. Stress-strain curves of composite backfill specimens under different layered proportions
表 1 让压层正交试验结果
Table 1 Orthogonal test results
序号 水灰质量比X1 发泡剂掺量X2/% 聚丙烯纤维掺量X3/% 抗压强度Y1/MPa 膨胀率Y2/% 1 1.00 0.03 0.20 14.18 5.54 2 1.00 0.06 0.60 13.75 7.91 3 1.00 0.09 0.40 13.63 8.34 4 1.25 0.03 0.60 12.92 5.99 5 1.25 0.06 0.40 12.38 9.71 6 1.25 0.09 0.20 10.41 9.80 7 1.50 0.03 0.40 9.08 9.10 8 1.50 0.06 0.20 8.97 10.31 9 1.50 0.09 0.60 7.64 11.71 
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表 2 单轴抗压强度各主控因素极差分析
Table 2 Uniaxial compressive strength of main control factors range analysis
项目 X1 X2 X3 K1 40.64 38.28 34.13 K2 35.31 35.09 37.34 K3 28.79 31.37 33.27 $\overline{K}_1 $ 13.55 12.76 11.38 $\overline{K}_2 $ 11.77 11.70 12.45 $\overline{K}_3 $ 9.60 10.46 11.09 R 3.95 2.30 1.36
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表 3 膨胀率各主控因素极差分析
Table 3 Range analysis of main controlling factors of expansion rate
项目 X1 X2 X3 K1 21.79 20.63 27.65 K2 25.5 29.93 27.15 K3 33.12 29.85 25.61 $\overline{K}_1 $ 7.26 6.88 9.22 $\overline{K}_2 $ 8.50 9.98 9.05 $\overline{K}_3 $ 11.04 9.95 8.54 R 3.78 3.10 0.68
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表 4 对照组与优化组力学测试结果
Table 4 Mechanical test results of control group and optimization group
期龄/d 组别 峰值强度/MPa 峰值应变/10−2 弹性模量/GPa 黏聚力/MPa 内摩擦角/（°） 抗拉强度/MPa 3 对照组 4.57 1.60 0.62 — — — 优化组 3.49 4.17 0.19 — — — 7 对照组 6.44 2.05 0.65 — — — 优化组 5.79 4.03 0.40 — — — 28 对照组 12.94 2.16 0.77 1.50 17 1.3 优化组 8.84 3.86 0.48 1.05 15 1.6
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