Investigation of the Effect of Geosynthetics on Climate-Induced Changes in Unsaturated Soil Behavior Using Non-Parametric Measure

The expansive behavior of clayey soil in response to climate-induced changes in the soil water characteristic curve (SWCC) is a significant issue for many types of earth infrastructure. The application of geosynthetic material has been common to reduce the climate-induced changes in SWCC. Engineered turf, which is a composite geosynthetic material, has gained popularity for different earth systems to increase overall infrastructure resiliency. This paper’s objective was to investigate engineered turf’s effect on the climate-induced changes in SWCC at shallow depths in the field conditions using the statistical non-parametric measure: Spearman rank correlation coefficient (ρ_s). This research hypothesized that since the changes in soil moisture and suction would relatively be simultaneous for exposed ground under variable climate, thereby exhibiting a reasonable negative correlation between water content and suction, whereas the degree of simultaneity in the changes between water content and suction of the soil under the engineered turf would display arbitrary correlation. To test the hypothesis, two test beds, (1) a compacted clay bed (CCB) and (2) a compacted clay bed overlain by engineered turf (ETB), were constructed with expansive soil and instrumented with collocated moisture sensors and tensiometers identically to collect concurrent water content and suction data continuously. The analysis revealed that the estimated ρ_s values for CCB were almost −1.0 during different drying conditions indicating a very strong correlation. On the contrary, the estimated ρ_s values for ETB were +0.79 to −0.32 indicating an irrational to a weak correlation between ρ_s. The results indicated the engineered turf to be an effective barrier to climate-induced changes in SWCC.