Permeability Characteristics of Improved Granite Residual Soils
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摘要: 针对福建尤溪花岗岩残积土遇水易软化崩解的特性，采用外掺法对其掺入改良剂进行改良，以降低其渗透系数。同时掺入石灰和粉煤灰，灰土质量比（即石灰质量∶粉煤灰质量∶花岗岩残积土质量）分别设置为1∶1∶8，1∶2∶7和1∶3∶6。对福建尤溪花岗岩残积土进行基本土工试验、击实试验和颗粒分析试验，对改良前后的尤溪花岗岩残积土进行变水头渗透试验，试验结果表明：（1）经掺入石灰和粉煤灰改良后的花岗岩残积土，其饱和渗透系数较改良前均有所降低，其抗渗性得到了提高。（2）当灰土质量比为1∶2∶7时，其饱和渗透系数降低幅度最大，改良效果最好。（3）无论重塑土还是改良土，其饱和渗透系数均随孔隙比的增大而增大，随干密度的增大而降低。Abstract: In response to the mechanical characteristics of the residual soil of granite in Youxi, Fujian, which is prone to softening and disintegration when encountering water, the external additives mixing method was used to improve its properties by adding additives to reduce its permeability coefficient. Adding ratios of lime, fly ash, and residual soil were set to 1∶1∶8, 1∶2∶7, and 1∶3∶6, respectively. Basic physical property index tests, compaction tests, and particle grading analysis tests were conducted on the granite residual soil from Youxi in Fujian. Variable water head permeability tests were conducted on the granite residual soil and improved granite residual soils separately. The test results showed that: (1) The saturated permeability coefficients of the improved granite residual soils by adding lime and fly ash into soil were decreased remarkably compared with that of the remolded residual soil, and its impermeability has been improved. (2) When the ratio of lime, ash, and soil is 1∶2∶7, the decrease in saturated permeability coefficient is the greatest, and the improvement effect in permeability is the best. (3) Whether remolded soil or improved soil, its saturated permeability coefficient increases with the increasing of its pore ratio, and decreases with the increasing of its dry density.
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表 1 福建花岗岩残积土的基本物理性质参数
土样名称 含水率w/% 天然密度ρ/(g·cm−3) 天然干密度ρd/(g·cm−3) 相对密度Gs 天然孔隙比e 塑限wp/% 液限wL/% 塑性指数Ip 福建花岗岩残积土 19.0 1.64 1.38 2.67 0.934 31.9 45.6 13.7 
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表 2 改良花岗岩残积土击实试验方案
含水率/% 1∶1∶8灰土质量比 1∶2∶7灰土质量比 1∶3∶6灰土质量比 14 15 13 18 19 16 20 22 19 22 24 21 24 26 24
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表 3 重塑花岗岩残积土和改良花岗岩残积土的击实试验结果
重塑花岗岩残积土 1∶1∶8灰土质量比 1∶2∶7灰土质量比 1∶3∶6灰土质量比 最优含水率/% 最大干密度/（g·cm−3） 最优含水率/% 最大干密度/（g·cm−3） 最优含水率/% 最大干密度/（g·cm−3） 最优含水率/% 最大干密度/（g·cm−3） 18.71 1.72 20.21 1.66 22.05 1.61 19.63 1.55
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表 4 改良花岗岩残积土渗透试验方案及结果
灰土质量比（石灰∶
粉煤灰∶残积土）干密度
ρd/（g·cm−3）孔隙比e 饱和渗透系数
k20/（cm·s−1）0∶0∶10 1.45 0.841 2.46×10−5 0∶0∶10 1.50 0.780 1.62×10−5 0∶0∶10 1.55 0.722 9.21×10−6 0∶0∶10 1.60 0.669 6.19×10−6 0∶0∶10 1.65 0.618 3.75×10−6 0∶0∶10 1.70 0.570 2.64×10−6 1∶1∶8 1.40 0.843 1.85×10−5 1∶1∶8 1.45 0.779 1.31×10−5 1∶1∶8 1.50 0.720 8.13×10−6 1∶1∶8 1.55 0.665 5.56×10−6 1∶1∶8 1.60 0.613 3.12×10−6 1∶1∶8 1.65 0.564 1.57×10−6 1∶2∶7 1.35 0.867 1.39×10−6 1∶2∶7 1.40 0.800 7.89×10−7 1∶2∶7 1.45 0.738 4.88×10−7 1∶2∶7 1.50 0.680 1.75×10−7 1∶2∶7 1.55 0.626 8.91×10−8 1∶2∶7 1.60 0.575 6.34×10−8 1∶3∶6 1.30 0.907 1.19×10−5 1∶3∶6 1.35 0.837 8.22×10−6 1∶3∶6 1.40 0.771 5.28×10−6 1∶3∶6 1.45 0.710 2.15×10−6 1∶3∶6 1.50 0.653 8.47×10−7 1∶3∶6 1.55 0.600 5.45×10−7
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