An Experimental Study on the Geotechnical, Mineralogical, and Swelling Behavior of KPK Expansive Soils

Abstract

Expansive soils are found in numerous regions of the world explicitly in arid and semiarid zones. These soils expand when absorbed moisture and shrink when released water. Such soil is viewed as a characteristic risk for infrastructures due to the shrink and swell behavior. These soils become more problematic when lightly or moderately loaded structures are built on them. The swelling and shrinkage in these soils chiefly happen due to the presence of montmorillonite minerals. The mineralogical and swell behavior of foundation soils is playing a vital role in the overall stability of a structure. These parameters are often ignored in the geotechnical report writing stage specifically in small projects, due to which, the durability and service life of the facilities are reduced and the maintenance cost is increased. To mitigate the potential damages in structures constructed on expansive soil, it is necessary to assess the mineralogical and swelling characteristics of expansive soil. The current study aims to determine the geotechnical, mineralogical, and swell behavior of the local expansive soils. Based on the results, the Karak soil has the highest plasticity index (PI) of 37% with a clay fraction of 28%, while the D.I. Khan soil has the least PI of 23% with a clay fraction of 17%. Similarly, Karak’s soil contained a higher percentage of montmorillonite (Rp = 8.9%). The maximum values of swell pressure, swell potential, and 1D deformation are 280 kPa, 12.5%, and 1.92 mm for the Karak soil, 6.45% 150 kPa, and 1.38 mm for D.I. Khan soil, and 10.5%, 245 kPa, and 1.64 mm for Kohat soil, respectively. This concludes that Karak’s soil has high plasticity and swell characteristics than Kohat and D.I. Khan soil. The swell characteristic of expansive soils increases with the increase in the percentage of the fine specifically the clay fraction. Furthermore, the Karak soil is more critical than Kohat and D.I. khan soil for lightly loaded structures.

Study on Expansion Characteristics and Expansion Potential of Gypsum Rock

“…This is because, in the test, the hydration of the upper anhydrite results in a weakened reaction between the lower anhydrite and water, which in turn causes a low free expansion rate of gypsum rock. Therefore, although the free expansion [25] rate is one of the most widely used judging indicators for expansive rock and soil, it is not suitable for judging the expansion potential of gypsum rock.…”

“…At present, expansive rocks are divided into two categories [13][14][15][16][17][18]: the first one is caused by chemical expansion reaction, the mechanism is complex, and the time is long (such as anhydrite and glauberite); the second one is caused by hydrophilic minerals, and the expansion of this type of rock is cyclically reciprocated under the action of water absorption and loss (such as mudstone and tuff) [19]. The main indicators for judging the expansion potential of expansive rocks include water content [20][21][22], viscous material content [9,15,[23][24][25], free expansion rate [25], ultimate expansion rate [26], dry saturated water absorption rate [27], and ultimate expansion force [9,25].…”