KSCE Journal of Civil Engineering

In this paper, a dynamic programming method is employed in conjunction with limit-equilibrium techniques to determine the location of the non-circular critical slip surface in the analysis of a slope failure due to a rainfall event. The Spencer method of slope stability analysis was incorporated into dynamic programming to predict the time of a slope failure and shape of the failure surface. A one-Dimensional (1D) sliding block model was used to analyze the motion of the failure mass. Furthermore, during the movement of the sliding mass, the stability of the model slope was analyzed by updating the shape of the model slope according to the new position of the sliding mass. The suction head in the soil pore provides soil shear strength to maintain the stability of the slope. The positive pore water pressure reduces the soil shear strength so that the slip surface beneath the water table will be more unstable. Numerous studies (using non-cohesive soil) have been conducted to locate the critical slip surface in slope stability problems without considering the increase in shear strength due to suction and apparent cohesion. The studies do not clearly illustrate the reasonable boundary conditions to avoid the slip surface alignment totally outside the actual slope. This paper clearly discusses the boundary conditions for such a slope stability problem reasonably. The step-by-step calculation procedure is presented through the flow diagram. Three cases of slope failure obtained from a laboratory flume experiment have been analyzed using the proposed method. The numerical simulation results and the results obtained from experiments are comparable.

A large number of heavy-duty asymmetric thin-plate box girder structures exist in large equipment, and their optimization can reduce the amount of material used and increase their load-carrying capacity. A new optimization method based on the Improved Quantum-Behaved Particle Swarm Optimization method (IQBPSO) is proposed in order to efficiently solve the mathematical model for the rationalization and optimization design of structures. The penalty function and Lévy flight strategy are considered in the optimization design of the improved algorithm, thus transforming the constrained optimization problem into an unconstrained optimization problem and improving the diversity and local optimization search capability of the quantum particle swarm. A mathematical model for the optimal design of box girder section size is established with the reduction of beam cross-sectional area as the objective function and the thin plate strength, rigidity, and stability of the thin slab as the constraints. The rapid lightweight design of the thin plate box beam was achieved, resulting in a 9.6% reduction in the manufacturing cost of the thin plate box beam. The optimization results are compared with several solutions of the thin slab box beams to verify the reliability and validity of the proposed optimization method.

The main objective of this study is to predict the stiffness of GFRP pipes subjected to compressive transverse loading. An experimental study is performed to measure the stiffness of a composite pipe with a core layer of sand/resin composites. Then, a simple analytical modeling constructed on the basis of solid mechanics is used to estimate the stiffness of the investigated pipe as the back-of-envelope technique widely used by industrial sectors. The simulation of stiffness test is conducted using finite element modeling wherein both large deformation and inelastic behavior of material is taken into account as the sources of nonlinearity. The results reveal that a very good estimation with high level of accuracy can be reached by proper selection of the element and performing nonlinear analysis.

Air quality management takes into consideration emission factors and inventories which are essential for developing emission control strategies for determining applicability of permitting and controlling programs and ascertaining the effects of sources and appropriate mitigation strategies. Emission estimates are also important for the related applications such as climate change etc. Emission inventories are studied by emission factors, which mostly lack association of some parameters, such as regional meteorological conditions, socioeconomic and developmental status and industrialization. This study offers a new approach (estimation of imission load) for the calculation of emission inventories after adding the estimation of many possible inputs and outputs. Foremost, average areal concentrations of pollutants are calculated by applying Percentage Weighting Polygon Method (PWP) to Erzurum urban SO2 imission measurement values. Later, mixing height of the study region in Erzurum, Turkey, is assessed by upper atmosphere observations from March 31st to April 1st 2006. Imission load of SO2 in Erzurum urban centre are calculated by a different paradigm based on multiplying urban centre area, mixing height and areal pollutant SO2 concentration values.

An experimental study was performed to investigate the dissipated energy to failure of sand samples subjected to uniform and non-uniform cyclic simple shear loading. The hypothesis evaluated was that for a given initial sample state the specific dissipated energy required to reach failure should be reasonably constant independent of the type of stress-time history used in the testing. Test samples consisted of dry Ottawa sand prepared at nine different initial states that were subjected to different stress controlled cyclic horizontal shear loading waveforms that included 15 uniform sinusoidal waves and up to 33 non-uniform loading wave forms. The experimental program presented showed that the measured cumulative dissipated specific energy to failure, defined when the double amplitude shear strain reaches 7.5%, for the different sample initial states was reasonably constant but with coefficients of variation ranging between 13 to 44%. As expected, the cumulative dissipated energy increased with increasing initial stress level and relative density. The findings support the notion that specific dissipated energy can be used as a reasonable failure predictor for uniform dry sands based on their initial state and are independent of the type of cyclic simple shear loading waveform using in the testing.

In this study, a three-dimensional model was used to numerically study the buoyant flow characteristics of heated water discharged from the submerged side outfalls in shallow and deep water. Hydraulic experimental data was used to evaluate the applicability of the model. The simulation results for model verification are in good accordance with experimental results. For shallow waters, the discharge jet is deflected by the river crossflow while forcing the river flow to bend towards the far bank over the depth. The unidirectional flow is dominant all over the depth in they-z cross section. In the case of submerged discharge with shallow water especially, the recirculating zone is the largest in the lowest layer, becoming smaller in the upper layer. As water depth increases, the ambient flow goes over the jet and thus diminishes the blocking effect so that jet bending decreases. Counterclockwise circulation and local eddies form with the increase of depth. Based on the viewpoint of rapid mixing and the dimension of the recirculating zone, submerged discharge appears more efficient than surface discharge.

To investigate the stratigraphic sequence in the ancient Yellow River Delta and further discuss the correlation of compressibility of undisturbed soils with depositional environments, two boreholes were drilled at Liyao test site in Cangzhou, Hebei Province, China. Some basic tests regarding to index properties were performed on sediments from one borehole, and oedometer test was conducted for the “undisturbed samples” collected from the other. The stratigraphic sequence in the study area is classified into four depositional systems in terms of sedimentation environment. Evaluation of sample disturbance shows that the “undisturbed samples” for oedometer test are just slightly disturbed in the sampling process. Since overall compressibility can be divided into intrinsic compressibility and additional one, the environmental factors that can affect soil microstructure are closely correlated with additional compressibility. Thus, the influencing mechanism of depositional rate on additional void index ΔI, was investigated quantitatively. Moreover, the relationship between floating range of yield stress and buried depth is established. Then, the additional compressibility of undisturbed samples can be evaluated with depositional rate and buried depth. Finally, the predicted overall compression curve with the proposed method in this study is compared with the measured curve to verify the reasonability and feasibility.