Geotechnical Characterization of the Subsurface Using Seismic and Electrical Resistivity Techniques in Mikinduri Meru County, Kenya

Abstract

Geotechnical study of the Mikinduri area was conducted with the aim to establish the causes of landslides and ground subsidence during the heavy rainfall. Sounding curves, travel time curves, 2D geoelectric sections, and 2D seismic models revealed 3-5 lithologic units to a depth of 30-250m. The study established thick loose alluvium deposits mixed with clay to a depth of 0.3-15m on an impermeable sub-basement as the possible major trigger of the landslides witnessed during rainy seasons. The thick alluvium deposits are due to erosion. They have been transferred by the location of the Mikinduri area, which lies in the lower regions of the Nyambene domes. Geologically, the domes were formed during Mount Kenya volcanic series and parasitic activities between the early Miocene and late Pleistocene eras. Resistivity modeling revealed deep geologic structures, including possible intrusions extending from 50m deep and faulted regions to a depth of 60-150m in the central and northeast area of study. The faulted area is highly saturated, as revealed by the low resistivity values. The delineated top black cotton soils and alluvium deposit are 40-50% clay and have poor foundation bearing capabilities. In contrast, compacted gravel, silt, and compact basaltic rock basement have good foundation capabilities. Keywords: Geotechnical, characterization, subsurface, seismic, electrical resistivity, foundation, geoelectric layer, Mikinduri Meru, Kenya.

Studia Quaternaria

“…In pre-and post-foundation studies, ERT provides in-sights into groundwater regimes (Maślakowski et al, 2014), seepage zones (Abu-Zied, 1994;Osazuwa and Chii, 2009), sinkhole (Yassin et al, 2014), bedrock structures (Storz et al, 2000;Ganerød et al, 2006;Egwuonwu et al, 2011). ERT technique can provide information on continuous profilling of depth to competent bedrock/formations and thickness of overburden covers (Robineau et al, 2007;Ngan-Tillard et al, 2010;Fadele et al, 2013;Nordiana et al, 2018). The technique can delineate undulating interfaces and boundary conditions.…”