*4.4. Effect of Fiber*

The results of permeability tests indicate that the ksat is a function of fiber type, dosage, and length (Figure 8). With an increase in dosage from 0.2 to 0.6%, the ksat values increased irrespective of the type of fiber for all specimens and are attributed to the randomly distributed fibers increasing the flow paths and causing free movement of the permeating liquid. In addition, an increase in fiber length from 6 to 12 mm results in an increase in

ksat values. However, this effect is not significant at higher curing periods. Relatively, the inclusion of FM results in increased ksat values compared to the inclusion of FC, especially at 0.6% dosage. This behavior is attributed to the fact that the FM has a rough surface with protrusions (Table 2) compared to FC, which facilitates in creating more drainage paths and leading to an increase in the resultant ksat values; whereas FC having a relatively smooth texture offers fewer drainage paths and leads to a reduction in ksat values at higher curing periods. Similar observations were reported by Abdi et al. [10] and Maher and Ho [11].

#### *4.5. Comparison between Flexible Wall Permeameter and Rigid Wall Permeameter*

A comparison of the ksat values obtained from the present study (using FWP at 50 kPa) and Moghal et al. [13] (using RWP) is presented in Figures 9–11 for the same materials under the same testing conditions. From Figures 9 and 10, the ksat values obtained from FWP are lower than the ksat values obtained from RWP tests for the fiber-reinforced lime-treated soil specimens up to a 7-day curing period irrespective of fiber type. A notable variation in ksat values (in the order of 10−1) is observed for specimens with 0.6% dosage and 12 mm length of fiber (FC and FM) compared to other combinations. Since complete control over the confining pressure and back saturation of a specimen prior to testing is possible in FWP, it leads to an accurate measurement of vertical and horizontal deformations and thus ksat values [21]. From the comparison, it is understood that FWP gives reliable results simulating the prevailing conditions in the field. For specimens cured for 28 days, the values of ksat obtained using FWP are higher than those obtained from RWP (Figure 11). Experimental results on RWP have revealed that at higher curing periods (28 days), the leakage of liquid through the sidewalls of RWP due to loss of soil contact may significantly influence the ksat values.

**Figure 9.** Comparison of hydraulic conductivity values from FWP and RWP (0-day curing period).

**Figure 10.** Comparison of hydraulic conductivity values from FWP and RWP (7-day curing period).

**Figure 11.** Comparison of hydraulic conductivity values from FWP and RWP (28-day curing period).

#### **5. Conclusions**

The present study evaluated the effect of fiber inclusion (FC and FM) on saturated hydraulic conductivity (ksat) of lime-treated expansive clay. The constant head method using FWP at various confining pressures is adopted for experimental work. The ksat values were evaluated at various dosages (0.2% and 0.6%), fiber lengths (6 and 12 mm), and curing periods (7 and 28 days). The following conclusions are drawn:


**Author Contributions:** A.A.S.: Methodology, Formal Analysis, Investigation, Data Curation, Writing Original Draft; M.A.A.-S.: Supervision, Funding Acquisition, Review and Editing; A.A.B.M.: Conceptualization, Writing Original Draft, Review and Editing, Moral Support; K.V.V.: Writing Original Draft and Final Version, Visualization. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work is funded by Deanship of Scientific Research, King Saud University through Vice Deanship of Scientific Research Chairs.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The content presented here was sourced from existing published literature, hence, this clause is not applicable.

**Acknowledgments:** The authors extend their appreciation to the Deanship of Scientific Research, King Saud University for funding this study through Vice Deanship of Scientific Research Chairs.

**Conflicts of Interest:** The authors declare no conflict of interest.

## **Abbreviations**

The following symbols are used in this paper:


#### **References**

