A non-woven, needle-punched geotextile is installed to accommodate cross-plane f

Question

A non-woven, needle-punched geotextile is installed to accommodate cross-plane flow, i.e., the flow is normal to the geotextile sheet. The geotextile is 3.0 mm thick, 1000 mm long, and 1000 mm wide. The total hydraulic head loss across the geotextile is 5.0 mm, and the design flow rate is 2000 ml/min. Is the geotextile used as a filter or a drain? Calculate the appropriate hydraulic properties of the geotextile, such as the transmissivity or permittivity, in-plane permeability or cross-plane permeability, whichever is applicable.

Explanation / Answer

The geotextile can act as a filter when flow occurs across the section and as a drain when the flow is along the surface. Here, the flow is normal to the sheet. hence, the geotextile acts as a filter.

The hydraulic properties to be found are permittivity and cross-plane permeability.

(a) Permittivity = q/(A.dH);

where

q= flow rate (m3/s) = 2000 mL/min = 3.33 x 10-5 m3/s

A= area of the geosynthetics (WxL) (m2) = 1000x1000 =106 mm2 = 1 m2

dH= head loss (m) = 5 mm = 5x10-3 m

i.e., Permittivity = (3.33x10-5)/(1x5x10-3)

= 6.67 x 10-3 sec-1

(b) Cross - plane permeability = permittivityxthickness of geotextile

= 6.67x10-3x3 = 0.02 m/s

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.