An experimental study of the California bearing ratio of basalt fiber reinforced loess
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摘要:
为研究纤维加筋黄土CBR值影响因素及纤维增强土体机理，以短切玄武岩纤维为筋材，通过改变土体含水率、纤维长度、纤维含量、击实次数、浸水时间等条件进行加州承载比试验，探究初始含水率、纤维参数及试验方法对加筋土局部抗剪强度的影响规律。结果表明：纤维加筋土CBR值随含水率的增加呈现先增大后减小的趋势，存在“施工最优含水率”且相比击实试验最优含水率高1%～3%左右；纤维加筋土CBR值高于黄土CBR值，确定纤维长度20 mm，纤维含量0.4%为最优配比；击实次数从30击增加到98击,黄土CBR值提高273%，纤维加入后CBR值提高327%，加筋作用使土体通过提高击实功来提升强度的效果更加显著；浸水对试样CBR值影响较大，浸水时间对试样CBR值影响较小，且纤维的加入使试样对浸水时间的敏感度进一步降低，加筋土浸水2 d后强度降低54%，浸水4 d后强度降低58%。
Abstract:In order to study the factors affecting the CBR value of the fiber-reinforced loess and the mechanism of the fiber-reinforced soil, chopped basalt fiber was used as the reinforcement material, and the CBR test was performed by changing the moisture content, fiber length, fiber content, compaction times and soaking time. The experiment explored the influence of initial moisture content, fiber parameters and test methods on the local shear strength of the reinforced soil. The results show that the CBR value of the fiber-reinforced loess has a tendency of increasing first and then decreasing with increasing moisture content. There is an "optimal moisture content for construction" and it is about 1% greater than the optimal moisture content of the compaction test. The CBR value of the reinforced soil is higher than the CBR value of loess. It is found that the fiber length of 20 mm and the fiber content of 0.4% are the optimal ratio. The compaction times increase from 30 to 98, the CBR value increases by 273%, the CBR value increases by 327% after the fiber is added. Reinforcement makes the soil local shear strength more effective by increasing the compaction work. The water immersion has a greater effect on the CBR value of the sample and the soaking time has less effect on it. The sensitivity of the sample to the soaking time is further reduced by the addition of fibers. The strength is reduced by 54% after 2 days of soaking, and the strength is reduced by 58% after 4 days of soaking.
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Key words:
- CBR value /
- moisture content /
- fiber content /
- fiber length /
- compaction times /
- soaking time
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表 1 黄土的物理性质指标
Table 1. Physical properties of loess
天然密度ρ/(g·cm−3) 比重Gs 天然含水率w/% 塑限wP/% 液限wL/% 塑性指数IP 孔隙比e 1.68 2.71 17.5% 21.2 35.2 14 0.90 
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表 2 玄武岩纤维的物理力学参数
Table 2. Physical and mechanical parameters of basalt fiber
密度
ρ/(g·cm−3)单丝直径
D/μm抗拉强度/
MPa弹性模量/
GPa使用温度/
℃耐酸碱性 2.63 13 3000～4800 91～110 −270～650 极强
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表 3 加筋土试验参数
Table 3. Test parameters of the reinforced soil samples
纤维长度/mm 纤维含量/% w=11.1% w=12.1% w=13.1% w=14.1% w=15.1% 5 0 0.2 0.4 0.6 0.8 10 0 0.2 0.4 0.6 0.8 20 0 0.2 0.4 0.6 0.8 40 0 0.2 0.4 0.6 0.8
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表 4 不同击实次数、浸水时间的试验参数
Table 4. Test parameters of different compaction times and soaking times
土样 浸水时间/d 击实次数0 击实次数50 击实次数98 素土 0 2 4 加筋土 0 2 4
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表 5 不同纤维长度及含量的击实试验结果
Table 5. Compaction test results of different fiber contents and lengths
纤维长度/mm 纤维含量/% 最大干密度ρdmax/(g·cm−3) wop /% 0 0 1.95 13.1 5 0.2 1.94 13.5 0.4 1.92 12.9 0.6 1.91 12.7 0.8 1.89 12.6 10 0.2 1.93 13.3 0.4 1.93 12.8 0.6 1.91 12.4 0.8 1.90 12.9 20 0.2 1.93 12.9 0.4 1.92 12.3 0.6 1.92 13.2 0.8 1.90 13.3 40 0.2 1.92 12.6 0.4 1.91 12.7 0.6 1.90 13.3 0.8 1.88 13.0
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