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Use of Bio-Cementation for Reducing Land Subsidence

Abed, Mahrooz | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51059 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khosravi, Ali; Pak, Ali; Ghobadi Nejad, Zahra
  7. Abstract:
  8. Land subsidence is a gradual settling or sudden sinking of the land surface from changes that take place underground. There are different causes of land subsidence; most notably, groundwater overdraft and severe weather conditions. Subsidence of the land surface due to ground water overdraft is caused by an increase in the intergranular pressure in unconsolidated aquifers, which results in a loss of buoyancy of solid particles in the zone dewatered by the falling water table and accordingly compaction of the aquifer. In this study, an experimental approach was developed to examine applicability of Microbially induced carbonate precipitation (MICP) for land subsidence control under environmental loading and severe climate conditions. MICP is an innovative technique which has been recently used to improve hydraulic and mechanical properties of soils under different loading conditions.This study focuses on the effect of varying moisture content conditions on the process of bio-cementation and the formation of hydraulic properties (i.e. soil water retention curve, SWRC) of sand treated using MICP technique.Exploitation of underground water is expected to result in significant changes in moisture content of soil in different layers affecting the process of bio-cementation. Based on the results of this study, MICP treatment is expected to reduce land subsidence and volumetric compression of sand. However, the difficulty of bacteria and chemical injection in unsaturated sand, especially at low values of degree of saturation may trigger the flushing of some of produced calcium carbonate, reducing the overall carbonate content and efficiency of MICP treatment. The spatial distribution of precipitation within the soil was also altered with changes in soil’s moisture content
  9. Keywords:
  10. Biocementation ; Unsaturated Sand ; Flow Pump ; Soil-Water Retention Curve ; Land Subsidence ; Soil Stabilization

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