Effect of mineralogical composition related to profile depth on index and strength properties of regolith soil
- PDF / 6,233,293 Bytes
- 18 Pages / 595.276 x 790.866 pts Page_size
- 4 Downloads / 198 Views
ORIGINAL PAPER
Effect of mineralogical composition related to profile depth on index and strength properties of regolith soil Bilgehan Kul Yahşi 1
&
Hakan Ersoy 1
Received: 23 January 2020 / Accepted: 7 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract While chemical weathering is the most significant geochemical process that affects the engineering behavior of rocks, the fact that authigenic soils present different values of their physical and mechanical properties depending on the depth is also directly related to weathering. Although it is known that such variation is applicable for regolith soils with thickness reaching tens of meters, significant differences can be observed through the depth of residual soils with the thickness of only a few meters. Ignoring such aspects especially in sites with a high risk of landslide leads to many engineering problems. Therefore, Trabzon Province, which has the highest potential of landslide in Turkey, has been selected as the pilot area within the scope of this study. The variations in engineering properties of regolith soils, which have a depth of up to 15 m and are weathered products of volcanic rocks, have been researched as a function of geochemical properties. For this purpose, the data collected from borehole applications, geophysical surveys, in situ cone penetration tests (CPT), and standard penetration test (SPT) as well as laboratory experiments have been evaluated; and it is observed that physico-mechanical properties are directly based on geochemical variations. While the zones with low SiO2 and high Al2O3 and Fe2O3 values are characterized with high content of clay and cohesion, depths with low S wave velocity correspond to areas with the highest chemical alteration index values and the highest degree of weathering. And high liquid limit (LL) values correspond to areas with high illite content as well as high Al2O3 and Fe2O3 values. At these depths, high friction ratio values are observed in CPT results. Obtained data indicate that physicomechanical properties vary as a function of the depth based on geochemical properties, and this suggests that the soil in projects with regolith soils needs to be separated into different layers and analyzed. Keywords Regolith . CPT . SPT . Seismic survey . Borehole . Trabzon . Turkey
Introduction Regolith term was first used by Merrill (1897) for identifying geological materials covering the bedrock. This definition was renovated by Eggleton (2001) to include materials such as fault and weathered blocks, saprolites containing parent rock blocks, weakly cemented volcanic rocks and tuffs, alluviums, and talus that are created as a result of one or several processes of weathering, erosion, transfer, and storage and are stored on the bedrock. Regoliths are mostly final products of various physical,
* Bilgehan Kul Yahşi [email protected] 1
Department of Geology, Karadeniz Technical University, Trabzon, Turkey
chemical, and biological processes altering the mineral structure of the
Data Loading...
