Foundation Alternatives in Dredge Fill Soils Overlaying Organic Clay

Abstract

Dhaka city has experienced a rapid growth of urban population for the last 40 years. This high population increase demands rapid expansion of the city. Unfortunately, most parts of the Dhaka city having competent subsoil for building construction are already exhausted. As such new areas are being reclaimed by both government and private agencies using dredge fill from nearby river sources. Sub-soil investigations have been carried out in different reclaimed areas within the city. It is found that top filling layer is non-plastic fine sand. Mean grain size of which varies from 0.15 to 0.20 mm. A very soft organic layer exists below the filling layer which is highly plastic and highly compressible. Field SPT N-value of filling layer and organic layer vary from 2 to 11 and 1 to 2, respectively. Attempts have been made to correlate unconfined compressive strength with SPT N-value, plasticity index, and organic content. Attempts have also been made to correlate compression index with organic content and initial void ratio of the soft organic clay. The correlations of the soil properties with organic content are variable and in most of the cases no definite correlations could be established. It has been observed that filling sand overlaying organic layer will badly affects the foundation on or having in it. Foundation alternatives have been suggested for the reclaimed areas in Dhaka city.

Microplastic Contamination in Soils: A Review from Geotechnical Engineering View

“…More than 200 million m 3 of dredge sediments have been collected annually from the bottom of almost 400 ports in the USA and mainly used for urban soil reconstruction and upland placement for agriculture [ 123 ]. In another study, the dredge sediment that was mainly composed of fine sand was collected from a riverbank in Dhaka, Bangladesh and used as filling material for land reclamation [ 124 ]. The total sediment amount that has been dredged annually in China is more than 5 billion m 3 [ 125 ].…”