Experimental study on shear strength of geopolymer stabilized soft soil
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摘要: 以固体氢氧化钠为碱性激发剂，矿渣和粉煤灰为前驱体，采用“一步法”制备粉煤灰−矿渣基地质聚合物。通过开展不固结不排水（UU）三轴剪切试验，测试粉煤灰−矿渣基地质聚合物固化软土的力学性能，揭示粉煤灰掺量、水灰比及养护时间等因素对固化软土抗剪强度的影响机制。同时计算固化软土的黏聚力和内摩擦角，并通过微观试验分析地质聚合物固化软土的作用机理。结果表明：粉煤灰掺量的增加导致地质聚合物固化软土的抗剪强度和内摩擦角减小；水灰比的增加使固化软土的抗剪强度降低；增大围压会使应变软化逐渐减弱，强度逐渐提高；养护时间增加，抗剪强度增加，黏聚力和内摩擦角同步呈现上升趋势。Abstract: Using solid sodium hydroxide as the alkaline exciter and slag and fly ash as the precursors, the fly ash-slag based geopolymer was prepared by "one-step" method. Through the unconsolidated and undrained (UU) triaxial shear test, the mechanical properties of soft soil stabilized with fly ash-slag based geopolymer were tested, and the influence mechanism of such as fly ash content, water to biner ratio, and curing time on the shear strength of the stabilized soft soil were investigated. The cohesion and internal friction angle of the stabilized soft soil were calculated, and the mechanisms of geopolymer stabilizing soft soil were also analyzed through microscopic tests. The results show that the increase of fly ash doping leads to the decrease of shear strength and internal friction angle of geopolymer stabilized soft soil; the increase of water to binder ratio reduces the shear strength of stabilized soft soil; the increase of cofining pressure makes the strain softening gradually weakened, and the strength gradually improved; the increase of curing time increases the shear strength, and the cohesion and the internal friction angle show a rising trend at the same time.
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Key words:
- geopolymer /
- stabilized soft soil /
- fly ash content /
- confining pressure /
- shear strength
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图 1 围压对地质聚合物固化软土应力−应变曲线的影响
Figure 1. Influence of confining pressure on stress-strain curve of geopolymer stabilized soft soil
图 2 粉煤灰掺量对地质聚合物固化软土应力−应变曲线的影响
Figure 2. Influence of coal ash percentage on stress-strain curve of geopolymer stabilized soft soil
图 3 养护时间对地质聚合物固化软土应力−应变曲线的影响
Figure 3. Influence of curing time on stress-strain curve of geopolymer stabilized soft soil
图 4 水灰比对地质聚合物固化软土应力−应变曲线的影响
Figure 4. Influence of water-cement ratio on stress-strain curve of geopolymer stabilized soft soil
图 5 不同粉煤灰掺量下地质聚合物固化软土的黏聚力
Figure 5. Cohesion of geopolymer stabilized soft soil with different fly ash content
图 6 不同粉煤灰掺量下地质聚合物固化软土的内摩擦角
Figure 6. Internal friction angle of geopolymer stabilized soft soil with different fly ash content
图 7 不同粉煤灰掺量下地质聚合物固化软土试样养护28 d的典型SEM形貌
Figure 7. SEM images of geopolymer stabilized soft soil with different FA content for 28 d curing time
图 8 不同养护时间下地质聚合物固化软土试样的典型SEM形貌
Figure 8. SEM images of the geopolymer stabilized soft soil with different curing time
图 9 不同水灰比下地质聚合物固化软土试样的典型SEM形貌
Figure 9. SEM images of the geopolymer stabilized soft soil with different water-cement ratio
表 1 土样物理性质指标
Table 1. Soil physical properties
天然含水率/％ 天然重度γ/(N·cm−3) 相对密度G 孔隙比e 液限wL/% 塑限wP/% 塑性指数IP 50 17.2 2.74 1.24 42.5 23.6 18.8 
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表 2 矿渣和粉煤灰的化学成分
Table 2. Chemical compositions of GGBFS and FA
单位：% 原材料 w(CaO) w(SiO2) w(Al2O3) w(SO3) w(TiO2) w(K2O) w(Fe2O3) GGBFS 40.303 30.638 15.721 2.039 0.779 0.521 0.416 FA 2.299 54.700 35.571 0.740 1.368 1.358 3.303
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表 3 地质聚合物固化软土的配比
Table 3. Proportioning of geopolymer stabilized soft soil
组号 地质聚合物固化软土配比 地质聚合物总掺量(m(硅铝
原材料) + m NaOH))/m(干土)重塑土含水率
m(水)/m(干土)养护
时间/dm(矿渣)/m(粉煤灰) m(水)/(m(硅铝原材料) + m(NaOH)) m(NaOH)/m(硅铝原材料) Ⅰ-1 100∶0 0.5 0.15 3/7/14/
28Ⅰ-2 0.6 Ⅰ-3 0.7 Ⅱ-1 90∶10 0.5 0.15 0.2 0.5 3/7/14/
28Ⅱ-2 0.6 Ⅱ-3 0.7 Ⅲ-1 80∶20 0.5 0.15 3/7/14/
28Ⅲ-2 0.6 Ⅲ-3 0.7
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