Linkan Sarker

ORCID Identifier(s)

0000-0001-7885-9200

Graduation Semester and Year

2018

Language

English

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering

Department

Civil Engineering

First Advisor

Sahadat Hossain

Abstract

Evapotranspiration (ET) landfill cover is an emerging final cover system and offers several benefits over conventional landfill closure system. It is a cost-effective green solution for the sustainability of a landfill as its performance enhances with time compared to the conventional solution where low hydraulic conductivity soil barrier deteriorates with time. ET cover system relies on the water store-release principle and its performance depends on the site-specific factors such as on-site climatological conditions, soil hydraulic properties and native vegetation. To effectively monitor the performance of this type of cover system, its unsaturated behavior, field capacity, available moisture for plant growth, soil water storage (SWS) and moisture retention capacity need to be assessed in a continuous manner. In previous studies, those monitoring parameters were observed through installed sensors and data logger system. But the main disadvantages associated with those sensors, are, they damage with time and exhibit poor performance in the long run which demands replacement of the sensors after a certain time. In this study, electrical resistivity imaging (ERI) technique was employed as an alternative tool to measure the unsaturated behavior of the ET cover system. The study was conducted on test section ET cover (Lysimeter) on different types of vegetation in the City of Denton landfill. Three types of vegetated soil; covering Native trail grass, Switchgrass and Bermuda grass, were considered for the current study. Moisture content and matric suction of the cover soil were measured by installed sensors in the lysimeter at different depths. ERI test was performed in the field at regular interval across the positions of the sensors. Based on the field instrumentation and geophysical measurement, the change in electrical resistivity with moisture content and matric suction was investigated at two different depths (12-inch and 30-inch) from the surface. The results indicated a significant relationship between soil resistivity and field unsaturated soil behavior. Field capacity, permanent wilting point and plant available water were also estimated from ERI technique. Average SWS was determined simultaneously from the installed sensors during the ERI test. Unit cross sectional area resistance (?a) was introduced and concurrent values were extracted from the obtained resistivity profile. An inverse relationship between SWS and ?a was observed. Existing soil moisture retention capacity (ESMRC) was also observed in terms of ?a. Average SWS and ESMRC were analyzed for three different assumed thicknesses of ET cover soil (4 ft, 3.5 ft and 3 ft) which showed that with decreasing ET cover thickness, its moisture holding capacity also decreases. The field investigation results showed the ERI technique to be a potential non-destructive geophysical method to quantify and evaluate the field unsaturated behavior of ET cover and hence, it is an effective alternative way to monitor the ET cover performance.

Keywords

Field SWCC, Soil water storage, Field capacity, Electrical resistivity

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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