Bu-Ali Sina University New Findings in Applied Geology 2228-5873 17 33 2023 06 22 Evaluation of geomechanical properties of argillite rocks in the region of south Makran (Chabahar-Nikshahr railway) Evaluation of geomechanical properties of argillite rocks in the region of south Makran (Chabahar-Nikshahr railway) 150 168 4655 10.22084/nfag.2022.26043.1514 FA V. Ahmadi Khounsaraki Ph. D. student, Dept., of Geology, Tarbiat Modares University, Tehran, Iran A. Uromeihy Prof., Dept., of Geology, Tarbiat Modares University, Tehran, Iran S. Madanipour Assist. Prof., Dept., of Geology, Tarbiat Modares University, Tehran, Iran M. Amiri Ph. D. student, Dept., of Geology, Faculty of Science, Ferdowsi University, Mashhad, Iran Journal Article 2022 04 04 Argillite rocks are among the weak rocks that cause problems in engineering projects due to their swelling, high cracking, low strength. The southern Makran structural zone is located in the southeastern part of Iran, between the two faults of Makran Trust and Qasr Ghand, and includes two sub-zones of coastal Makran and outer Makran. Most of the sediments are Quartz fragments (silt size) with carbonate cement containing sub-minerals of calcite and fossil fragments, indicating a shallow and low-energy marine environment of the Neogene age. The distribution of grains is mainly silty and angular in a Carbonate cement field with a calcium carbonate content of less than 15% and in coastal Makran due to the formation of sprite calcite between 70 and 80%. In order to determine the physical and mechanical properties of southern Makran argillaceous rocks along the Chabahar-Nikshahr railway axis in this research, porosity tests, plate load test (PLT), X-ray fluorescence test (XRF) and diffraction results X-ray (XRD) are conducted. The results of XRF samples show that the major constituent oxides are SiO₂, Al₂O₃, Fe₂O₃ and CaO, and the results of XRD indicate mainly silty mineralogy including: Quartz, calcite, albite, Muscovite, Clinochlore and Dolomit. The Field study in each of the sub-zones was used for rock mass classification and sampling for laboratory tests to determine geotechnical properties. According to the rock mass classifications, most sediments are in poor and very poor classifications due to tectonic conditions and high weathering. Petrological studies and determination of physical properties show that sediments located in coastal Makran have more porosity and less cement due to the young sedimentation basin and are in the category of weak rocks based on point load strength (Is₅₀<2MPa) according to Bieniawski classification. Indirect results of the uniaxial compaction test show that the sediments have a strength of less than 20 MPa, which has a high correlation with the amount of porosity (R2 = 0.95). Also, the relationships between uniaxial compressive strength and density and Calcium carbonate are (R2 = 0.81) and (R2 = 0.89), respectively. Argillite rocks are among the weak rocks that cause problems in engineering projects due to their swelling, high cracking, low strength. The southern Makran structural zone is located in the southeastern part of Iran, between the two faults of Makran Trust and Qasr Ghand, and includes two sub-zones of coastal Makran and outer Makran. Most of the sediments are Quartz fragments (silt size) with carbonate cement containing sub-minerals of calcite and fossil fragments, indicating a shallow and low-energy marine environment of the Neogene age. The distribution of grains is mainly silty and angular in a Carbonate cement field with a calcium carbonate content of less than 15% and in coastal Makran due to the formation of sprite calcite between 70 and 80%. In order to determine the physical and mechanical properties of southern Makran argillaceous rocks along the Chabahar-Nikshahr railway axis in this research, porosity tests, plate load test (PLT), X-ray fluorescence test (XRF) and diffraction results X-ray (XRD) are conducted. The results of XRF samples show that the major constituent oxides are SiO₂, Al₂O₃, Fe₂O₃ and CaO, and the results of XRD indicate mainly silty mineralogy including: Quartz, calcite, albite, Muscovite, Clinochlore and Dolomit. The Field study in each of the sub-zones was used for rock mass classification and sampling for laboratory tests to determine geotechnical properties. According to the rock mass classifications, most sediments are in poor and very poor classifications due to tectonic conditions and high weathering. Petrological studies and determination of physical properties show that sediments located in coastal Makran have more porosity and less cement due to the young sedimentation basin and are in the category of weak rocks based on point load strength (Is₅₀<2MPa) according to Bieniawski classification. Indirect results of the uniaxial compaction test show that the sediments have a strength of less than 20 MPa, which has a high correlation with the amount of porosity (R2 = 0.95). Also, the relationships between uniaxial compressive strength and density and Calcium carbonate are (R2 = 0.81) and (R2 = 0.89), respectively. https://nfag.basu.ac.ir/article_4655_544c8dd5a675726d66d2930ea8a22f41.pdf