an engineering geological characterisation of tropical clays - GBV
an engineering geological characterisation of tropical clays - GBV
an engineering geological characterisation of tropical clays - GBV
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
15<br />
Chapter 2<br />
Previous works<br />
2.1 Summary<br />
A Germ<strong>an</strong> pr<strong>of</strong>essor, Suess (1892) summarised the geology <strong>an</strong>d structure <strong>of</strong> the Eastern Rift<br />
Valley, to the west <strong>of</strong> Nairobi city <strong>an</strong>d the present study area. The Eastern Rift Valley runs<br />
across Kenya from Malawi in the south to the Dead Sea in the north.<br />
Gregory traversed the country <strong>of</strong> Kenya in the period <strong>of</strong> 1896 to 1919. He made import<strong>an</strong>t<br />
early contributions by studying <strong>an</strong>d establishing the geology <strong>of</strong> some selected areas. He also<br />
studied <strong>an</strong>d described the major volc<strong>an</strong>ic series underlying Nairobi <strong>an</strong>d the study area; <strong>an</strong>d<br />
which include the Kapiti phonolites, trachytes, agglomerates, the Nairobi building stone <strong>an</strong>d<br />
the basic lavas <strong>of</strong> the Ngong volc<strong>an</strong>ic centre. He named <strong>an</strong>d designated the Kapiti phonolite<br />
as the oldest unit <strong>of</strong> the series. He published his works <strong>an</strong>d findings two years later (Gregory,<br />
1921) as well as a number <strong>of</strong> papers dealing with various aspects <strong>of</strong> the Rift Valley <strong>an</strong>d its<br />
environs.<br />
Prior, <strong>of</strong> the Mineral Department <strong>of</strong> the British Museum, later examined a large number <strong>of</strong> the<br />
rock specimens collected by Gregory from around the country <strong>an</strong>d which included Kapiti<br />
phonolite <strong>an</strong>d phonolitic quartz trachytes from Nairobi <strong>an</strong>d the current study area. In his<br />
published works (Prior, 1903), he recognised various subdivisions <strong>of</strong> the phonolitic series.<br />
Kunzli (1901) gave <strong>an</strong> account <strong>of</strong> the volc<strong>an</strong>ic rocks <strong>of</strong> the Eastern Rift Valley that included a<br />
description <strong>of</strong> the riebeckite trachytes <strong>an</strong>d phonolitic trachytes <strong>of</strong> the Kikuyu highl<strong>an</strong>ds <strong>an</strong>d<br />
north – western parts <strong>of</strong> the present study area.<br />
In 1905, Maufe, then <strong>of</strong> the Geological Survey <strong>of</strong> Great Britain, conducted a <strong>geological</strong><br />
survey along the railway from Mombasa (in the south) to Kisumu (in the west), through<br />
Nairobi. He later published his works <strong>an</strong>d findings (Maufe, 1908) in which he gave a brief<br />
summary <strong>of</strong> the geology between Nairobi <strong>an</strong>d Kijabe (to the north <strong>of</strong> the study area) by<br />
describing the principal rock types found. He also commented on the nature <strong>of</strong> faulting on the<br />
east fl<strong>an</strong>k <strong>of</strong> the Rift Valley.<br />
Earlier works <strong>an</strong>d brief comments on the geology <strong>of</strong> Nairobi <strong>an</strong>d its surroundings were also<br />
done by Walker (1903), Collie, (1912) <strong>an</strong>d Krenkel (1925). Krenkel described the volc<strong>an</strong>ic<br />
succession found by making reference to specific rock types, based on the earlier works <strong>of</strong><br />
Maufe (1908) <strong>an</strong>d Gregory (1921).<br />
Sikes, then Director <strong>of</strong> Public Works Department, Kenya, conducted underground water<br />
surveys in the Nairobi area in the period <strong>of</strong> 1920 to 1925. He also described the grid – fault<br />
structures caused by late faulting in the areas to the west <strong>of</strong> Nairobi city <strong>an</strong>d in the Rift region.<br />
The results <strong>of</strong> his observations <strong>an</strong>d findings were published in subsequent reports (Sikes 1926,<br />
1934 <strong>an</strong>d 1939). Additional hydrological investigations were undertaken in the years that<br />
followed by staff <strong>of</strong> the Ministry <strong>of</strong> Public Works, Nairobi, who examined in detail boreholes<br />
drilled at the time in the rapidly – growing Nairobi metropolit<strong>an</strong> area. The results <strong>of</strong> this work<br />
were incorporated in a technical report by Gevaerts (1964).<br />
Wayl<strong>an</strong>d, formerly Director <strong>of</strong> Geological Survey Ug<strong>an</strong>da, made a survey <strong>of</strong> materials in<br />
Kenya, including Nairobi <strong>an</strong>d the present study area. He investigated the materials for their