Research @NTU on Unsaturated Soil Mechanics for Sustainable Urban Living in Singapore

Research Objectives

Singapore is located in a tropical region where abundant rainfalls and high temperatures provide conditions for rapid and thorough insitu chemical and mechanical weathering of rocks. The active weathering process gives rise to deep residual soil profiles. In tropical regions, residual soils commonly exist in an unsaturated state with negative pore-water pressures. The negative pore-water pressures contribute additional shear strength to the unsaturated soils. Numerous studies have indicated that many slopes often fail during and after periods of heavy rainfalls in Singapore. Trees also tend to be overturned under similar conditions. Infiltration of water into the soil occurs during rainfall, reducing negative pore-water pressures and reducing the shear strength of the soil. The end result is the failure of many slopes and the uprooting of trees during heavy rainfalls. The assessment of stability of slopes and trees needs to take into consideration the mechanics and properties of unsaturated soils and the flux boundary conditions related to the imposed climate (i.e., rainfall infiltration, evaporation and transpiration across the ground surface). The application of unsaturated soil mechanics to geotechnical engineering is generally considered to be beyond classical soil mechanics and it is usually ignored by engineers. Unsaturated soil mechanics is becoming increasingly important as engineers become aware that global climate change concerns can be taken into consideration when analyzing the dynamic inter-action between the environment and near-ground-surface soils.

As Singapore moves towards a more liveable, and more sustainable city, carefully planned and executed research must be carried out to optimise land and resource utilisation. Over the past two decades, the School of Civil and Environmental Engineering (CEE) at NTU has embarked on several collaborative research projects which have attempted to provide state-of-the-art solutions to overcome problems imposed by inter-actions with the environment and the environmental changes and resource limitations. The cutting edge research in unsaturated soil mechanics conducted @ NTU has been a major contributor to the realization of the sustainable city blueprint for Singapore in facing challenges associated with global climate changes.

About the Unsaturated Soil Mechanics for Sustainable Urban Living Digital Project

The Unsaturated Soil Mechanics for Sustainable Urban Living digital project is an online knowledge base with photos, illustrations and images on core principles, methodology, modelling and applications of unsaturated soil mechanics to slope stability (particularly with respect to rainfall-induced slope failures) and tree stability. The database intends to provide a central resource with browse and search access to local researchers from academic institutions and government agencies, regional researchers where local soil and climate similar to Singapore, international researchers following the work of Professor Harianto Rahardjo on unsaturated soil mechanics; as well as to the general public who may wish to be more aware of research funded and carried out in unsaturated soil mechanics and its impact on slope failures and tree stability in Singapore.

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