Influences of particle shape and degree of compaction on shear response of clinker ash
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摘要: 炉渣颗粒土是火电厂发电过程中煤炭燃烧产生的一种颗粒废弃物,近年来经常作为边坡和路基回填材料在工程建设中使用。对6种不同产地的炉渣颗粒土进行了单颗粒破碎试验,发现炉渣颗粒土的单颗粒强度显著低于天然砂土,具有较大的破碎性。随后,开展了一系列排水三轴剪切试验,研究了颗粒形状、压实度和围压对其剪切特性的影响。三轴试验结果表明,压实度可以显著提高炉渣颗粒土的初始刚度及峰值抗剪强度。相较于自然砂土,炉渣颗粒土拥有较大的峰值摩擦角,作为回填材料可提供较大的承载力。另外,炉渣颗粒土的峰值摩擦角随着围压的增大而降低。分析结果揭示颗粒形状和单颗粒强度均是影响炉渣颗粒土抗剪强度的重要因素。在不同的围压水平,两者对峰值抗剪强度的影响程度有所不同。另外,通过图像分析法获取了不同种类炉渣颗粒土的多种形状参数,发现炉渣颗粒土的圆度和球度都显著小于大部分自然砂土,表明该类颗粒材料拥有较为复杂的颗粒形状。分析结果还表明炉渣颗粒土的临界状态摩擦角与炉渣颗粒土的各个形状参数都存在一定程度的关联性。采用了一个新的能够考虑多种颗粒形状因素影响的综合指标,建立了其与临界状态强度和临界状态线位置参数的经验关系表达式。Abstract: The clinker ash is a kind of granular waste produced after the combustion of coal. It has been used in slope and foundation engineering as backfill materials. The single-particle crushing tests on the clinker ash from six different origins are carried out. The results indicate that the clinker ash particles own much lower single-particle strength than the natural sands and exhibit larger crushability. A series of drained triaxial shear tests are performed on the clinker ash to examine the effects of particle shape, degree of compaction and effective confining pressure on its shear characteristics. An increase in the degree of compaction strengthens the initial stiffness and the peak shear strength of the clinker ash. Compared to the natural sands, the clinker ash possesses larger peak friction angle and provides higher bearing capacity as foundation materials. As the effective confining pressure increases, the peak friction angle of the clinker ash gradually decreases. The results suggest that both the particle shape and the single-particle strength are important factors affecting the shear strength of the clinker ash. In addition, several particle shape parameters of the clinker ash are decided using the digital image analysis method. The clinker ash has smaller roundness and sphericity indexes due to its complex particle shape. The analysis results show that the critical state friction angle is well correlated with the particle shape parameters. A general and new particle shape index is employed to correlate with the relevant parameters associated with the critical state and its position.
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Key words:
- particle shape /
- clinker ash /
- critical state /
- degree of compaction /
- friction angle
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图 2 电子显微镜下炉渣颗粒土典型颗粒图像
Figure 2. Electron scanning images of typical clinker ash grains
图 3 炉渣颗粒土和天然砂土的平均单颗粒破碎强度
Figure 3. Mean crushing strengths of clinker ash and natural sands
图 4 炉渣颗粒土干密度随含水率的变化规律
Figure 4. Variation in dry density of clinker ash with water content
图 5 炉渣颗粒土在不同试验条件下的应力-应变关系曲线
Figure 5. Stress-strain curves for clinker ash under different test conditions
图 6 不同压实度条件下炉渣颗粒土的应力-应变关系
Figure 6. Stress-strain curves for clinker ash under different degrees of compaction
图 7 不同压实度条件下炉渣颗粒土的峰值摩擦角
Figure 7. Variation in peak friction angle of clinker ash with varying degrees of compaction
图 8 颗粒形状参数对临界状态摩擦角的影响
Figure 8. Effects of particle shape parameters on critical state friction angle of different granular materials
图 9 炉渣颗粒土平均规则性ρ与临界状态角的关系
Figure 9. Relationship between mean regularity of particles and critical state friction angle for clinker ash
图 11 炉渣颗粒土和天然砂土的平均规则性ρ与临界状态线位置参数的关系
Figure 11. Relationship between mean regularity of particles and critical state line position parameters of clinker ash and other natural sands
表 1 炉渣颗粒土物理性质
Table 1. Physical properties of clinker ash
试样 颗粒相对质量密度Gs 最大孔隙比 最小孔隙比 不均匀系数 平均粒径 /mm 平均单颗粒强度 /MPa CA.A 2.072 1.748 0.949 20.3 0.570 4.27 CA.B 2.151 1.646 1.010 12.5 0.210 1.99 CA.C 2.173 1.618 0.883 13.8 1.300 2.56 CA.D 2.132 1.488 0.887 21.2 0.220 1.04 CA.E 2.151 1.422 0.752 26.7 0.710 4.75 CA.F 2.110 1.425 0.769 21.0 1.750 3.12 
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表 2 炉渣颗粒土的颗粒形状参数
Table 2. Particle shape parameters of clinker ash
试样 圆形度R 长宽比 球度S 凹凸度C 平均规则性 CA.a 0.402 0.715 0.781 0.947 0.711 CA.b 0.375 0.708 0.707 0.930 0.680 CA.c 0.389 0.663 0.810 0.935 0.701 CA.d 0.414 0.645 0.801 0.949 0.702 CA.e 0.388 0.676 0.747 0.935 0.686 CA.f 0.387 0.652 0.751 0.941 0.682 CA.A 0.379 0.645 0.814 0.929 0.691 CA.B 0.366 0.684 0.822 0.916 0.697 CA.C 0.408 0.704 0.820 0.956 0.723 CA.D 0.362 0.625 0.823 0.928 0.684 CA.E 0.396 0.689 0.821 0.942 0.712 CA.F 0.384 0.714 0.817 0.945 0.715
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表 3 三轴排水剪切试验条件
Table 3. Experimental conditions for drained triaxial shear tests
试样 /kPa 实际压实度Dc/% 试样 /kPa 实际压实度Dc/% CA.A 50 83.5 88.1 96.9 CA.D 50 83.6 87.3 100 88 97.9 100 90.8 100.7 200 83.4 87.4 99.1 200 85.0 101.4 CA.B 50 88.1 90.1 103.4 CA.E 50 84.6 87.7 100.1 100 92.7 104.2 100 85.0 86.2 102.9 200 86.0 93.7 104.9 200 90.0 98.0 CA.C 50 83.8 88.2 96.8 CA.F 50 85.0 88.9 100.3 100 98.6 100 85.0 92.0 99.3 200 83.0 101.0 200 99.9 注： 目标压实度Dc为85%,90%,100%。
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表 4 炉渣颗粒土临界状态摩擦角与临界状态线几何参数
Table 4. Critical state friction angles and geometrical parameters of critical state line for clinker ash
试样 临界状态摩擦角 截距Γ 斜率 CA.A 39.95 1.541 0.121 CA.B 40.15 1.589 0.117 CA.C 38.82 1.596 0.097 CA.D 40.10 1.576 0.132 CA.E 39.02 1.598 0.114 CA.F 39.54 1.609 0.102 CA.a 38.77 1.619 0.098 CA.b 39.45 1.621 0.108 CA.c 39.04 1.545 0.121 CA.d 38.60 1.655 0.114 CA.e 39.16 1.591 0.111 CA.f 39.21 1.589 0.127
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