Abstract:Using the techniques of system simulation, real-time monitoring, databases, and visualization, simulation and visual analysis for the construction of the storehouse surface of a roller-compacted concrete(RCC)dam was carried out. An elaborate simulation model for storehouse surface construction was established, through which detailed construction progress information can be obtained. Furthermore, interactive three-dimensional dynamic visualization analysis for storehouse surface construction was realized. These research achievements have been applied in a RCC dam in Southwest China.

Abstract:The backwater caused by bridge piers on plain rivers was numerically simulated using the water-blocking ratio of piers(α)as the control parameter. The backwater effect of piers was investigated in terms of the creep height in front of piers and the backwater height in front of a bridge according to different generation mechanisms and influence areas. The influence area of the creep height in front of piers was determined by the variation coefficient of the cross-sectional backwater height. It is concentrated around the piers with higher water-blocking ratios(α>7%). The relationships between the dimensionless relative backwater height β_yg, the relative distance from the location with the maximum backwater height to the bridge pier, and the water-blocking ratio were analyzed using the cross-sectional average backwater height as the representation variable. The results show that the maximum backwater height occurs at four to five times the pier width in front of the pier with higher water-blocking ratios, and the increase in the water-blocking ratio causes the maximum backwater height in front of the bridge to rapidly increase and the backwater area to continuously enlarge. The water-blocking ratio of 7% is a significant demarcation value for the backwater height in front of bridges on plain rivers. Thus, the water-blocking ratio of medium and large bridges should not be more than 7%.

Abstract:In order to investigate the effects of the joint operation of gates and pumps on the improvement of the water environment, using the central area of Suzhou City as an example, a one-dimensional hydrodynamic and water quality model for river networks, including 45 key hydraulic projects, was established based on measured data. The pollution sources were classified and calculated in detail. The measured water quality data were used to validate the model. The law of water quality change under the conditions of normal years and the current operation scheme was studied. The results show that the variations of concentrations of COD_Cr and NH⁺₄-N are negatively correlated with the water level, and the water quality in dry seasons is better in the northwest and worse in the southeast. Therefore, a scheme for reallocating the diverted water from the Xitang River using gates and pumps in the central area of the city is proposed to improve the water quality in dry seasons. The simulation results show that the water quality in most areas can reach a higher grade under the new operation scheme. The concentrations of pollutants in the monitoring sites decreased significantly, and the maximum reduction rate reached 49. 7%.

Abstract:Based on the rainfall profile in the landslide-prone area on the reservoir bank slope near the dam of the Longjiang Hydropower Plant in Yunnan Province, the slope stability under antecedent rainfall was investigated. By using the self-developed experimental apparatus, laboratory model tests were conducted to simulate landslides under antecedent rainfall, and the characteristics of landslides were analyzed. Research shows that antecedent rainfall is a major factor in landslides. Antecedent rainfall infiltrates the slope from the surface, reducing the soil strength and leading to a loss or reduction of the matrix suction in the unsaturated soil. Thus, the subsequent rainfall can easily generate landslides. Landslides induced by antecedent rainfall are categorized as shallow retrogressive landslides.

Abstract:Due to the lack of detailed field data recording the dam breach process, most of the models for overtopping-induced dam breach analysis of earth-rock dams have not been fully validated. In view of this problem, 17 models for analysis of mechanisms of earth-rock dam breach are summarized. The BREACH model, DB model, and IWHR model were used to simulate 1/3 of the accidents involving the Tangjiashan barrier dam breach, and the differences between measured and calculated results regarding the erosion rate of dam materials, discharge curve, and water level curve were analyzed. The influences of cohesion, the internal frictional angle, the non-uniformity coefficient, and porosity of dam materials on the discharge curve were studied with the BREACH model. The results show that the peak discharge predicted by the IWHR model is the highest, followed by those predicted by the BREACH model and DB model; the time, corresponding to the peak discharge, obtained by the DB model and IWHR model, is earlier than that obtained by measurement, while the corresponding time obtained by the BREACH model is later than that obtained by measurement; with the increase of cohesion and the internal frictional angle, the calculated peak discharge decreases and the corresponding time is delayed; with the increase of porosity and the non-uniformity coefficient, the peak discharge increases and the corresponding time comes earlier; and the non-uniformity coefficient and porosity have a significant influence on the calculated results regarding the dam breach.

Abstract:In order to study the mechanism of agricultural soil moisture conservation through sand injection in the northwest arid region of the Loess Plateau, rainfall infiltration tests on three kinds of indoor soil columns(a homogeneous soil column, a soil column with a 3 cm-thick sand layer, and a soil column with a 5 cm-thick sand layer)were performed, and the water-resisting phenomenon of the sand layer was analyzed through establishment of a micro model. The water contents in different layers of soil columns at two times(13 days and 197 days)and the δD and δ¹⁸O values of soil water were measured with the drying method and MAT253 gas isotope ratio mass spectrometer. The change in water content with the depth and the relationship between δD and δ¹⁸O of soil water were obtained. The results show that the sand layer can retard water infiltration rather than prevent water infiltration. The reasons for this are that the water-holding capacity of sand is far less than that of loess, retarding water infiltration, and the sudden decrease in the wetted cross-sectional area at the interface with abruptly changed medium causes the water infiltration velocity to decrease.

Abstract:Based on the results of a large number of laboratory compression-direct shear combined tests, the shear strength properties and mechanisms of typical peaty soil with a high degree of decomposition, sampled from three different sites in Kunming and Dali cities, were analyzed. The test results demonstrate the following: the shear stress-shear displacement curves of peaty soil showed different shapes in the consolidated quick shear test, quick shear test, and slow shear test; with the increase of the normal stress, the shear deformation changed from plastic deformation to elastic-plastic deformation in the consolidated quick shear and slow shear tests; the shear deformation in the quick shear test showed mainly the plastic deformation under different normal stresses; the shear strength envelopes of peaty soil with a high degree of decompression were, basically, two intersecting polygonal lines with different slopes; the normal stress(σ_s)corresponding to the break point of shear strength envelopes was about 200 kPa in the consolidated quick shear test and slow shear test, and the value was about 100 kPa in the quick shear test. Based on analysis of the compression deformation of peaty soil, the evolution mechanisms of the shear strength were further analyzed by means of establishing compression-shear microstructural models for peaty soil. We conclude that the increasing normal stress causes peaty soil to change from a porous state to a relatively densified state, leading to changes in the shear strength and the shear strength parameters.

Abstract:To obtain large-area seismic deformation, the imaging mode and data characteristics of ESAs new generation Sentinel-1A SAR were studied. The method for processing interferometric data from TOPSAR images is presented in this paper. Based on data from the Sentinel-1A, an interferogram covering an area of 160 km×180 km in the region of the Nepal April 25 earthquake was generated. The results show that the maximal relative deformation in the line of sight direction reaches about 2 m.

Abstract:In consideration of the diffusion, electric field migration, and binding, a coupling chloride ion migration model was established based on Ficks second law. The model was verified with experimental data. Using the saline soil environment in Nantong City as an example, Comsol Multiphysics software was used to analyze the migration mechanisms of chloride ions in concrete, to simulate the temporal and spatial distributions of chloride ions in concrete, and to examine the chloride resistance of ordinary Portland cement(OPC)concrete and fly ash concrete with different strength grades. The results show that, in the saline soil environment, the OPC concrete structure cannot meet the durability requirements by only improving the concrete strength grade and protective cover thickness. Fly ash concrete can improve the service life of the concrete structure. In the saline soil environment in Nantong City, a reinforced concrete structure should adopt fly ash concrete, and the protective cover thickness of fly ash concrete with strength grades of C30, C40, C50, and C60 should be 55 mm, 50 mm, 45 mm, and 40 mm, respectively, for a service life of 100 years.

Abstract:In order to acquire better forecast results for settlements of dykes with fabric form sand, a fractional-order grey model is presented based on the grey model. The program was established using MATLAB to change the differential-order derivative into a fractional-order one. This model was used to predict the settlement of dykes with fabric form sand. Comparative analysis of the grey Verhulst model, residual GM model, and proposed model was performed. The results show that the predicted results of the fractional-order grey model are more accurate, and the fractional-order grey model not only has the reliable previous forecast effect of the GM(1, 1)model, but also the reliable later forecast effect of the Grey Verhulst model. Moreover, the long-term forecast results of the fractional-order grey model show a higher degree of stability than those of the GM model.

Abstract:In order to avoid selection of the type of functions when using traditional copula methods to fit the joint probability distribution, the copula function and the maximum entropy principle were jointly used(in a method also called the copula entropy method), and the two-dimensional joint distribution functions of flood variates were obtained by solving the copula function with the maximum entropy. With the solved copula function, the two-dimensional joint distribution functions of flood variates(peak discharge, flood volume, and flood duration)were mutually constructed. The Gibbs sampling method and copula functions were used to stochastically simulate trivariate flood events. A case study was conducted using the observed flood data from the Lutaizi Hydrological Station on the Huaihe River. A goodness-of-fit analysis shows that the copula entropy method is effective in fitting multivariate probability distributions and the Gibbs sampling method is effective in simulating trivariate flood events.

Abstract:To investigate the distribution characteristics of ammoniaoxidizing archaea (AOA) in sediments of shallow lakes, we chose the shallow lakes in the Lixia River area, which is in the lower Huaihe River Basin, as the research object and studied the community structure of AOA in four shallow lakes with different functional types in the region using the methods of molecular biology and microbiology. The results show that there exists AOA in this region and this provides an important supplement to the global geographic distribution and habitat of AOA. In the surface sediments of this region, the diversity and richness of AOA is highest in the center of Dazong Lake. AOA is mainly accumulated in the groups 1.1b and 1.1a, in which, 71.3％ of the sequences belong to Group 1.1b and 28.7％ of the sequences belong to Group 1.1a. The presence of submerged plants significantly improves the richness of Group 1.1b, and abundant organic matter is conducive to promoting the growth of AOA. The surrounding factories, sandpits, fisheries, and the livestock breeding upstream of Jiulongkou affect the characteristics of the community in the surface sediments.

Abstract:The ecological flow obtained from traditional hydrologic methods that adopt measured runoff series affected by human activities is lower than its actual value. In order to solve this problem, an improved 7Q10 method is proposed based on analysis of long series of rainfall and runoff data, and is used to calculate the minimum ecological flow at representative hydrological stations upstream, midstream, and downstream of the Luanhe River. The results indicate that runoff in the Luan River has been significantly affected by human activities since 1979, and the minimum ecological flow obtained from the improved 7Q10 method is more reasonable than that obtained from the traditional method.

Abstract:The power system reliability evaluation methods are time-consuming and generate large errors. In order to solve these problems, a method for reliability evaluation of power systems is proposed based on the improved particle swarm optimization(PSO), the least squares support vector machine(LSSVM), and Monte Carlo simulation(MCS), where the improved PSO is used to optimize the parameters of SVM. The method can obtain more accurate LSSVM parameters through reasonable improvement of PSO, and a PSO-LSSVM model for classification of system state samples has been established. Using the PSO-LSSVM model to classify the system samples extracted by the MCS method, failure state samples and normal state samples were obtained with the PSO-LSSVM model. Reliability indices only for failure state samples were calculated and reliability evaluation results were output. This method was used to calculate the reliability index of the IEEE-RTS 79 system under different operation conditions, and the results show that the method improves the evaluation precision of the LSSVM-MCS method with a consistent amount of computation time.

Abstract:Based on the development and utilization condition of energy and resources and power energy demand in the Ngari area of Tibet, possible power supply schemes were studied. A clean energy utilization hybrid model of a reservoir power station and photovoltaic plant is proposed through comprehensive comparison of power system requirements, operation and maintenance, environmental protection, and economics. The system structure, power generation characteristics, and operation effect of this hydro-photovoltaic hybrid system are analyzed. The results show that the complementary power-generating characteristic of the energy utilization pattern using the reservoir power station and photovoltaic plant is beneficial to photovoltaic power consumption and power network safety operation.