Abstract
Expansive clays are found worldwide in arid and semiarid regions. Such soils are considered a natural hazard for civil engineering infrastructures especially when they are lightly loaded. Expansive soils are often unsaturated due to the high absorption capacity of moisture. The damaging effect of expansive soils is intimately related to the distinctive soil‐water characteristic in the surficial soil layers subjected to wetting‐drying cycles. The soil‐water characteristic curve (SWCC) also known as the water‐retention curve shows the fluctuation of suction with the moisture content. It is one of the key parameters that have been developed and used by soil engineers for studying the properties of partially saturated soils. Currently, the SWCCs produced by most of the researchers are grounded on lab testing which is quite different from the field‐obtained curves. In the current study, the SWCCs for Karak expansive soil have been obtained from in situ testing (field). For this purpose, three sites were selected at Amberi Village (Karak) for instrumentation. An open trench of six‐foot depth was excavated in each site and instrumented. Electrical resistivity sensors (G‐blocks) and tensiometers were used for matric suction measurements. The gravimetric moisture content was measured with the help of moisture sensors calibrated with a speedy moisture meter. To check the fluctuation of moisture and suction, these instruments were installed at three different depths, that is, 0–2, 2–4, and 4–6 feet. Based on results, the maximum suction of 705.79 kPa was observed in the site “A” in 0–2‐foot depth (near the ground surface) with a moisture content of 15 percent. The variations in suction and moisture content follow the almost same trend at low suction; however, the trend was slightly different at the moderate suction range. The measured suction showed a strong correlation with the free swell index (FSI) and moisture content. It was found that the upper layers of expansive soil have high suction than lower layers due to more exposure to the environmental agencies and low density.
Highlights
Expansive soil is clayey soil in nature which undergoes large volume changes upon changing in the moisture content
E drying process of sites A and B was quicker than site C due to the low plasticity (CL) nature of site C. e suctions measured with tensiometers were close enough up to a certain extent with the sensors installed in the upper layers for all the sites
Three sites of expansive soil were instrumented with moisture and suction measuring devices. e following conclusions can be drawn from this study
Summary
Expansive soil is clayey soil in nature which undergoes large volume changes upon changing in the moisture content. E main objective of the current study is to check the behavior of local expansive soil in the framework of unsaturated soil mechanics and develop some correlation equation for subsequent use For this purpose, field instrumentation was carried out using a low-cost technique for measuring indirect matric potential (suction) and gravimetric moisture content in the field at shallow depths. E matric potential is very useful in studying the hydrological processes in the soil, such as evapotranspiration, availability of water for plants, and modeling the gas and water flow in unsaturated soil [10] It is applied in the strength and deformation characteristic of unsaturated soil and determining the physical response of various soil at different moisture contents [11]. If gypsum block sensors are separately calibrated, the obtained suction results will be close to that measured with the filter paper method [16]
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