Experimental research on the influence of mica on strength of cement-reinforced soft clay
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摘要:
软黏土具有压缩性强、承载能力低的特点，实际工程中多用水泥作为固化剂对软黏土进行加固。云母是软黏土中较为常见的一种片状矿物，其含量和颗粒大小会影响水泥加固后的软黏土即水泥软黏土的强度。通过无侧限抗压强度试验和直接剪切试验研究云母含量及目数对水泥软黏土抗压强度及抗剪强度的影响，提出了云母含量、目数与水泥软黏土抗压强度、抗剪强度指标值之间的关系。试验中云母目数设定为10，20，40，80目共4个梯度，云母含量设定为0%、8%、16%、24%、32%共5个梯度。试验结果表明，云母含量的增加以及云母目数的减小会导致水泥软黏土无侧限抗压强度和抗剪强度的降低，且其对无侧限抗压强度的不利影响更为显著。含10目32%云母的水泥软黏土的强度减少量最大，此时无侧限抗压强度为0.33 MPa，是不含云母水泥软黏土的25.5%；黏聚力为76.5 kPa，比不含云母时减少了12.24 kPa；内摩擦角由不含云母时的23.71°降低至21.77°。云母自身的片状形态及其对水泥水解水化作用、离子交换作用的阻碍是造成水泥软黏土强度降低的主要原因。
Abstract:Soft clay is of the characteristics of strong compressibility and low bearing capacity. Cement is used as curing agent to strengthen soft clay in engineering. Mica is a kind of mineral widely distributed in soft clay, and its content and particle size will affect the strength of the cement-reinforced soft clay. The influence law among the mica content and mica mesh number on strength of the cement-reinforced soft clay is studied based on direct shear tests and unconfined compressive strength tests. Based on the experimental data, the mathematical relationship between the content and mesh number of mica and soil-cement strength is established. The number of mica meshes in the experiment is 10, 20, 40 and 80 mesh, and the mica content is set as 0%, 8%, 16% and 32%. The results show that as the content of mica increases or the number of mica meshes decreases, the unconfined compressive strength and shear strength of the cement-reinforced soft clay show a decreasing trend, and the effect of mica on the unconfined compressive strength is more significant. When the number of mica mesh in the cement soft clay is 10 mesh and the content is 32%, the strength of the cement soft clay decreases the most. In this case, the unconfined compressive strength of 0.33 MPa is 25.5% of that of the cement soft clay without mica, the cohesion is 76.5 kPa, which is 12.24 kPa less than that of the cement soft clay without mica, and the internal friction angle decreases from 23.71° to 21.77°. It is speculated that the lamellar morphology of mica and adverse effect on cement hydration are the main reasons for the decrease of the cement soil strength.
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Key words:
- mica /
- cement-reinforced soft clay /
- compressive strength /
- cohesion /
- internal friction angle
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表 2 云母的主要化学成分
Table 2. Chemical compositions of mica
成分 SiO2 Al2O3 K2O Na2O MgO Fe2O3 含量/% 44～50 20～33 9～11 1～2 1～2 2～6 
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表 3 软土的基本物理性质
Table 3. Physic-mechanical indices of soft soil
天然密度ρ/(g·cm−3) 黏聚力c/kPa 内摩擦角φ/(°) 含水率w/% 孔隙比e 1.71 19 8.2 68 1.79
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表 4 软黏土的矿物成分
Table 4. Mineral compositions of soft clay
/% 石英 钾长石 斜长石 蒙脱石 伊蒙混层 伊利石 高岭石 绿泥石 32.4 1.7 15.4 1.0 3.8 26.7 9.5 9.5
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表 5 水泥软黏土强度试验结果
Table 5. Results of the cement-reinforced soft clay strength
云母含量/% 云母目数 10目 20目 40目 80目 qu/MPa c/kPa φ/(°) qu/MPa c/kPa φ/(°) qu/MPa c/kPa φ/(°) qu/MPa c/kPa φ/(°) 0 1.28 88.74 23.71 1.28 88.74 23.71 1.28 88.74 23.71 1.28 88.74 23.71 8 1.11 84.15 22.22 1.13 85.68 22.45 1.14 87.21 23.34 1.14 87.90 23.71 16 0.63 81.86 22.15 0.71 82.62 22.37 0.79 85.68 22.96 0.87 86.46 23.41 24 0.42 79.56 21.99 0.55 81.09 22.22 0.67 83.39 23.04 0.71 84.15 23.56 32 0.33 76.50 21.77 0.45 78.80 22.07 0.52 81.86 23.12 0.58 82.62 23.34
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表 6 水泥软黏土强度试验统计值
Table 6. Test statistics of strength of the cement soft clay
抗压强度qu/MPa 黏聚力c/kPa 内摩擦角φ/(°) 云母目数0，含量0% 1.28 88.74 23.71 云母目数10，含量32% 0.33 76.50 21.77 差值 0.95 12.24 1.94 强度损失比 74.2% 13.8% 8.2%
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