Abstract
Swelling and shrinkage are the two distinctive characteristics of expansive soils, and due to this behavior, these soils are considered a natural hazard for infrastructure. Many structures in different regions have been impaired due to the swell/shrink behavior of the expansive soil. Most of the severe distress is impeded because of the inherent suction (negative pore water pressure) present in expansive soils. Both suction and swelling parameters are greatly affected by the surrounding moisture content. Due to this feature of expansive soil, geotechnical engineers are interested in utilizing the suction-based correlations for the assessment of unsaturated expansive soils. The current investigation was carried out to develop novel correlations incorporating lab testing and field instrumentation. To fulfill the objectives, eight sites of the local expansive soil in Pakistan were selected for samples collection and field testing. Conventional odometer testing was conducted to measure the swell pressure (Sp) and swell potential (S) of the fabricated/remolded specimens. Gypsum block (G-block) sensors were additionally utilized for estimating the matric suction in the field. To expand the database, the previously published data of the same nature was also incorporated. Based on the results, the power form of the novel correlations (suction-based) is highly significant for estimating (Sp), while for swell potential, the logarithmic correlation with R2 = 0.6551 is more significant than other forms of correlations. The proposed suction-based correlation can be equally utilized for the estimation of field suction as well as for swell behavior of expansive soil having a plasticity index (PI) ≥ 22%.
Highlights
Expansive soil is a specific type of soil in which large-volume changes take place due to fluctuations in its moisture content. e volume changes occur in two different ways, namely, expansion and contraction or shrinkage. e expansion will occur when such soil is inundated in water due to absorption, while shrinkage happens when its moisture is extracted or evaporated
Recent research has recommended that the expansive behavior of soils could be assessed in a better way if the matric suction is considered in the investigations. e matric suction relies upon measurement of water content and chemical and physical characteristic of soils, including specific surface area, Advances in Civil Engineering mineralogical composition, stress condition, structure, relative compaction, voids ratio, and pore size distribution, in which the moisture content is more significant among different elements while dealing with the swell and shrinkage parameters
Conclusions. e current investigation comprised of field instrumentation and lab testing was conducted for developing some novel suction-based correlations for estimating swell parameters of local expansive soils. e major conclusions drawn from this experimental study are listed : (1) Basic geotechnical characteristics and designation of the eight local expansive soils investigated in the current study evaluated that Karak’s soil is more critical in wet conditions than Kohat and D.I Khan’s expansive soil for the construction of lightweight structures
Summary
Expansive soil is a specific type of soil in which large-volume changes take place due to fluctuations in its moisture content. e volume changes occur in two different ways, namely, expansion and contraction or shrinkage. e expansion will occur when such soil is inundated in water due to absorption, while shrinkage happens when its moisture is extracted or evaporated. E matric suction relies upon measurement of water content and chemical and physical characteristic of soils, including specific surface area, Advances in Civil Engineering mineralogical composition, stress condition, structure, relative compaction, voids ratio, and pore size distribution, in which the moisture content is more significant among different elements while dealing with the swell and shrinkage parameters. In the field, where structures are built on foundation soils, expansion in volume occurs in a vertically upward direction only, and lateral swell is resisted by the confining soils. Due to this phenomenon, structures will lift up or settle down only in a humid environment and cyclic dry period, respectively. Roads, and other facilities are susceptible to distress because of the presence of expansive soils [10, 11]. e distress is more critical when differential settlements occur due to shrinkage, and their maintenance cost is increased
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