ABSTRACT:The Saigon River, which flows through the center of Ho Chi Minh City, is of critical importance for the development of the city as forms as the main water supply and drainage channel for the city. In recent years, riverbank erosion and failures have become more frequent along the Saigon River, causing flooding and damage to infrastructures near the river. A field investigation and numerical study has been undertaken by our research group to identify factors affecting the riverbank failure. In this paper, field investigation results obtained from multiple investigation points on the Saigon River are presented, followed by a comprehensive coupled finite element analysis of riverbank stability when subjected to river water level fluctuations. The river water level fluctuation has been identified as one of the main factors affecting the riverbank failure, i.e. removal of the balancing hydraulic forces acting on the riverbank during water drawdown.
There are gaps in our knowledge regarding temporal changes in wood stability and mechanical properties in the context of wood durability. Energetic analyses have been performed in this study based on experimental results on the bending fatigue of wood under multiple loading conditions. New findings regarding the fatigue limit and fatigue life (N f ) are presented. The strain energy (SE) obtained from stress-strain envelopes until wood reaches its N f is a value specific to wood species and static strength regardless of the loading conditions. This value is about 50% higher than the SE in static tests. The relationship between mean energy loss (EL) and stress level (SL) to the point of fatigue failure is bilinear, and the mean EL is closely related to N f . Moreover, the SL -when mean EL approaches a specific value (∼1.10 kJ m -3 per cycle) as N f approaches infinity -is considered to be the fatigue limit; the latter is estimated to be about 20-30% of static strength.
Riverbank collapse often occurs along the Saigon River which flows through Ho Chi Minh City (HCMC). One of the influencing factors is the soft ground which is the riverbank composed of. Our research about the ground improvement method using quicklime, rice husks ash so far. Rice straw is newly added to the improved soil in this paper. The Rice straw is expected to improve the failure strain property that is to restrain brittle failure. These mixing materials can be obtained easily and cheaply in Vietnam. A series of unconfined compression tests are carried out to improve the mechanical properties of improved soil. Moreover pH tests are conducted to validate the chemical action of the improved soil and evaluate the effect of improved soil on surrounding environment.
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