Engineering geological evaluation and zoning of bearing capacity of Gypsum soils in the Gachsaran formation using SPT test results on Masjed Soleyman Petrochemical site

Jowkar, Mohammad Hossein; Khamehchiyan, Mashalah; Nikudel, Mohammad Reza

doi:10.22034/jiraeg.2025.235313

Engineering geological evaluation and zoning of bearing capacity of Gypsum soils in the Gachsaran formation using SPT test results on Masjed Soleyman Petrochemical site

Document Type : Original Article

Authors

Mohammad Hossein Jowkar ¹

Mashalah Khamehchiyan ²

Mohammad Reza Nikudel ³

¹ Dept. of Engineering Geology, Fcaulty og Basic Sciences, Tarbiat Modares University

² Engineering Geology Department, Faculty of Basic Sciences, Tarbiat Modares University

³ Engineering Geology Department, Faculty of Basic Sciences, Tarbiat Modares university

10.22034/jiraeg.2025.235313

Abstract

Gypsum soils are among the most complex and problematic soil types due to their high solubility and the limited understanding of their engineering behavior. This study addresses these limitations by developing detailed bearing capacity zoning maps at 1.5-meter depth intervals down to the groundwater table, using SPT test results from over 80 boreholes drilled at the Masjed Soleyman Petrochemical site. The maps were compared to the level and direction of underground water flow obtained from EDP tests, as well as to the regional gypsum karst map, which was created using a combination of geophysical (GPR) and geotechnical (boreholes) methods. This comparison helps identify potential project locations and provides insight into the region's suitability for project implementation. In the second step, the study area was divided into two distinct regions by conducting laboratory and in-situ (including 6 PLT tests under both dry and saturated conditions) soil mechanics tests, and integration results with geological data and the locations of sensitive facilities to determine the allowable bearing capacity of single and mat foundations (regarding shear strength of the soil), calculated for each region. The combination of SPT data, the uniformity of subsurface layers, and correlations between bearing capacity and karst development maps indicate that variations in bearing capacity are mainly controlled by weak interlayers and by the dissolution and leaching of gypsum. Over time, these processes lead to the formation of gypsum karsts, representing a major geotechnical hazard and the most critical factor affecting the stability and suitability of the region for construction.

Keywords

Bearing capacity

gypsum soils

Masjed Soleyman petrochemical

SPT test

Gachsaran Formation

Subjects