This study presents a nonlinear optimization technique (NOT) for conducting the back analyses of geotechnical engineering problems
based on the field observations. Additional auxiliary techniques are incorporated to enhance the convergence and stability of the NOT.
The developed NOT and additional auxiliary techniques are incorporated into a finite element code and then applied to the back analysis
of excavation-induced wall deflection. A number of hypothetical excavation cases with various scenarios of stratigraphy and two quality
excavation case histories are used to validate the developed NOT, in which the dominant soil parameters are treated as target parameters.
Results show that the wall deflections of all hypothetical and actual excavation cases at each stage can be accurately and efficiently backfigured.
Abstract--COD and nitrogen balances were performed on four different types of laboratory-scale activated sludge system: aerobic, anoxic, anoxic-aerobic and anaerobic-anoxic-aerobic (biological excess phosphorus removal systems). The systems included a variety of configurations, with differing wastewater characteristics and operating parameters. The results suggest that good COD balances are to be expected in aerobic and anoxic-aerobic systems. Systems incorporating anaerobic zones exhibit low COD balances (less than 80%). Fermentation in the anaerobic zone apparently is implicated in this "loss" of COD. The consequences of the COD "loss" include both a significant decrease in oxygen requirements and in sludge production compared to aerobic or anoxic-aerobic systems. Possible mechanisms for the loss of COD and areas which require further study are discussed.
