**2.4. Results and discussion**

## *2.4.1. Hydraulic permeability*

Table 5 shows the values of permittivity and coefficients of cross-plane permeability for six laminar geotextile composites by the cross-plane permeability test and theoretical values obtained by equations (2) and (3). Figure 18 shows the inverse of permittivity and coefficients of cross-plane permeability. To interpret permeable phenomena, it is more convenient to determine the water permeability by using the permittivity than the coefficient of cross-plane permeability. Therefore, theoretical values of water permeability of laminar geotextile composites are larger than those of experimental values. It was considered that this was due to the effects of loss rate of hydraulic pressure as a result of changes of porous areas at the inner interface of geotextile composites.


**Table 5.** Permeability coefficient and permittivity of laminar geotextile composites.

Nanotechnology Formulations and Modeling of Hydraulic Permeability Improvement for Nonwoven Geotextiles http://dx.doi.org/10.5772/61997 313

**Figure 18.** Inverse values of normal permeability and permittivity for several samples of nonwoven geotextiles.

#### *2.4.2. Modeling by inlet forms*

**Geotextile Composite** A–B A–C A/E A–F D/A D/C **Thickness (mm)** 6.02 7.00 5.29 4.82 8.10 6.82

The hydraulic conductivity of laminar geotextile composites was determined in terms of permittivity under the constant head method and falling head method in accordance with ASTM D 4491 test method. The permeability coefficient was determined by multiplication of permittivity and thickness of geotextile. (*Fluet Jr, J. E., 1985; ASTM D 35 Committee, 2015*)

Table 5 shows the values of permittivity and coefficients of cross-plane permeability for six laminar geotextile composites by the cross-plane permeability test and theoretical values obtained by equations (2) and (3). Figure 18 shows the inverse of permittivity and coefficients of cross-plane permeability. To interpret permeable phenomena, it is more convenient to determine the water permeability by using the permittivity than the coefficient of cross-plane permeability. Therefore, theoretical values of water permeability of laminar geotextile composites are larger than those of experimental values. It was considered that this was due to the effects of loss rate of hydraulic pressure as a result of changes of porous areas at the

**Permeability Coefficient (cm/sec) Permittivity (sec–1)**

A/B 4.951 2.364 3.576 3.757 1.173 1.258 0.578 0.607 A/C 4.441 2.125 2.828 3.039 1.086 0.743 0.411 0.441 A/E 4.914 0.023 0.096 0.105 1.193 0.020 0.018 0.020 E/A 0.023 4.914 0.091 0.106 0.020 1.193 0.017 0.020 A/F 5.033 0.029 0.185 0.199 1.193 0.042 0.038 0.041 D/A 3.487 3.956 3.513 3.712 0.881 0.956 0.434 0.458 D/C 4.427 2.042 2.812 2.972 1.118 0.714 0.412 0.436 C/D 2.042 4.427 2.860 2.972 0.714 1.118 0.419 0.436

Layer

Lower

Layer Composite Eq. (3)

Layer Composite Eq. (2) Upper

**)** 750 800 1,210 730 1,050 830

**Weight (g/m2**

312 Non-woven Fabrics

*2.3.3. Water permeability test*

**2.4. Results and discussion**

*2.4.1. Hydraulic permeability*

**Laminar Geotextile Composite**

inner interface of geotextile composites.

Lower

**Table 5.** Permeability coefficient and permittivity of laminar geotextile composites.

Upper Layer

**Table 4.** Specifications of laminar geotextile composites.

The inlet forms of inner interface of laminar geotextile composites to be related to the loss rate of hydraulic pressure are shown in Figure 19. In case of various porous areas of laminar geotextile composites, the permittivity and loss rates of hydraulic pressure are represented in Table 6. The lower the coefficient values of cross-plane permeability and permittivity, the larger the loss rate of hydraulic pressure. This was why the inlet forms of inner interface of laminar geotextile composites were bell mouth or soft tube structures. lower the coefficient values of cross-plane permeability and permittivity, the larger the loss rate of hydraulic pressure. This was why the inlet forms of inner interface of laminar geotextile composites were bell mouth or soft tube structures.

The inlet forms of inner interface of laminar geotextile composites to be related to the loss rate of

composites, the permittivity and loss rates of hydraulic pressure are represented in Table 2.4. The

**Figure 2.3. Inlet forms of inner interface of laminar geotextile composites. Figure 19.** Inlet forms of inner interface of laminar geotextile composites.


**Table 6.** Loss rate of hydraulic pressure of laminar geotextile composites.

#### **2.5. Conclusion**

**5. Conclusion** 

For laminar geotextile composites having different fiber-packing densities, water permeability was decreased with the smaller fiber-packing densities and this was due to the more bulky and less compacted structure of fibers. It was reasonable to apply the permittivity to interpret the water For laminar geotextile composites having different fiber-packing densities, water permeability was decreased with the smaller fiber-packing densities and this was due to the more bulky and less compacted structure of fibers. It was reasonable to apply the permittivity to interpret the water permeability of laminar geotextile composites instead of the coefficient of cross-plane permeability. The experimental values of water permeability exhibited the smaller values than theoretical values due to the loss rate of hydraulic pressure and inlet forms of inner interface. From these results, it was known that the hybrid structure of geotextiles to perform the smart drainage function could be manufactured by the variation of the fiber-packing density.
