An experimental study of clogging of the geotextile filter system under normal stress
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摘要:
模拟实际工况，采用改进的可以施加竖向荷载的梯度比渗透仪完成了一系列土工织物过滤黏性土的梯度比试验。试验采用上海地区第④层黏性土和短纤针刺无纺土工织物，分别在临界水力梯度（1.0）和水力梯度为2.0下进行，并通过改变竖向荷载来研究土工织物反滤性能随水力梯度和法向应力的变化规律。研究结果表明：水力梯度和法向应力是影响土工织物淤堵特性和滤层透水能力的重要因素。随着竖向荷载的增加，土工织物过滤黏性土的梯度比有所增大，但其稳定时并未发生不容许的淤堵；在特定荷载下，渗透系数随时间减小，而后趋于稳定，稳定后的渗透系数随竖向荷载的增大而减小；水力梯度由1.0增大到2.0，也引起了土工织物-黏性土体系的梯度比增大，透水能力减弱。试验结果较好地反映了实际工况下土工织物滤层的反滤作用，可为类似工程设计提供参考。
Abstract:For simulating the actual working conditions, a series of gradient ratio tests of geotextile filtering clay are completed by using an improved gradient ratio permeameter that can apply vertical load. The tests are carried out under the condition of the critical hydraulic gradient (1.0) and hydraulic gradient equal to 2.0, respectively, with the 4th layer of clay soil in Shanghai and the short fiber needle punched non-woven geotextile. The variation of the filtration performance of geotextile with hydraulic gradient and normal stress is studied by changing the vertical load. The results show that the hydraulic gradient and normal stress are the important factors affecting the clogging characteristics and the permeability of geotextile filter. The gradient ratio of the geotextile filter clay increases with the increase of the vertical load, but there is no impermissible clogging when it is stable. Under a certain load, the coefficient of permeability decreases with time and then tend to stabilize. The stabilized coefficient of permeability decreases with the increase of the vertical load. The hydraulic gradient from 1.0 to 2.0 also causes the increase of the gradient ratio and the decrease of the permeability. The test results better reflect the filtration effect of the geotextile filter under the actual working conditions, which can provide references for similar engineering design.
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Key words:
- geosynthetics /
- nonwoven geotextiles /
- filtration /
- normal stress /
- gradient ratio test
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表 1 临界水力梯度下各级荷载稳定后的GR值
Table 1. Gradient ratio of stable loads under the critical hydraulic gradient
荷载/ kPa 0 5 15 25 GR 0.63 1.18 1.64 1.83 
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表 2 各级荷载稳定后的GR值(i=2.0)
Table 2. Gradient ratio of stable loads at all levels(i=2.0)
荷载/ kPa 0 5 15 25 GR 2.06 2.20 2.25 2.27
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表 3 临界水力梯度下各级荷载稳定后的渗透系数
Table 3. Coefficient of permeability of stable loads under the critical hydraulic gradient
荷载/kPa 0 5 15 25 K/(10−6cm·s−1） 3.40 1.70 1.30 0.89
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表 4 各级荷载稳定后的渗透系数(i=2.0)
Table 4. Coefficient of permeability after all levels of load stabilization (i=2.0)
荷载/ kPa 0 5 15 25 K/(10−6cm·s−1） 1.50 1.10 0.78 0.18
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