Assessment, identifying, and presenting a plan for the stabilization of loessic soils exposed to scouring in the path of gas pipelines, case study: Maraveh-Tappeh city

Abstract

Dealing with collapsible soils consistently presents a crucial challenge for geological and geotechnical engineers. Loess soil is among the most widely recognized types of collapsible soils, covering approximately 10 % of the Earth's land surface. Loessic soil is a sedimentary deposit primarily composed of silt-size grains, loosely bound together by calcium carbonate. In Iran, approximately 17 % of Golestan province is covered by silty, clayey, and sandy loesses, primarily composed of loessic soil. Additionally, several energy transmission lines in this province traverse these loess-covered areas. Based on the reports from Golestan Gas Company experts, the scouring of gas pipeline channels in various regions, such as Dashli-Alum in Maraveh-Tappeh city, causes significant risks in the traffic roads and is one of the most critical issues facing this company. This research assessed the dispersion and collapse potentials of loess soil using a range of field exploration and laboratory testing methods. These methods included atomic absorption spectroscopy, the double hydrometer, scanning electron microscope photography, wavelength-dispersive X-ray fluorescence spectrometry, and consolidation tests. The results indicate that soil collapsibility was acquired as one of the components of the scouring phenomenon occurrences. To achieve an optimal solution, the effectiveness of the chemical stabilization method involving cement, bentonite, micro-silica, and synthesized nano‑titanium additives was evaluated through an oedometer, Atterberg limits, uniaxial compression, and direct shear tests. Additives dry mixing of cement and nano‑titanium were obtained as the optimal stabilization solutions against scouring compared to other additives. However, considering the environmental impacts of cement production and use, nano‑titanium presents a more environmentally sustainable option due to CO₂ absorption and reduced damage potential to vegetation.