Abstract:In order to better apply the API model and Xin’anjiang model to the ungauged regions, the parameter regionalization study and its application were conducted in this paper. Here, the API model and Xin’anjiang model were applied to small and medium-sized basins in the Dabie Mountain area and South Anhui Mountain area, the regional regularity of model parameters in the selected area was studied, and the result of regionalization was verified by the new hydrological station for the small and medium-sized rivers. The results show that both API model and Xin’anjiang model can be used to simulate the flood runoff in the study area; stepwise regression analysis can effectively deduce the sensitive parameters; based on the parameter regionalization method combining spatial proximity and stepwise regression analysis, the average deterministic coefficients for hourly API model and Xin’anjiang model simulations in the new hydrological station are 0. 92 and 0. 86, respectively. Therefore, this method can effectively deduce the parameters of API model and Xin’anjiang model in the ungauged basins of selected area.

Abstract:Based on the needs of water resources management in the Tarim River Basin, the relationship between surface water and groundwater conversion was revealed to better exert the overall function of regional water resources. Using the HSPF-MODFLOW model, daily runoff process simulation was carried out in the basin, and the Nash coefficient E_ns, the deterministic coefficient R² and the root mean square error σ were selected to determine the simulation results. Under changing conditions, the atmospheric precipitation-surface water-groundwater conversion law was clarified. The results show that the simulated Nash coefficients of surface water in the calibration period and the verification period were both greater than 0. 7, and the simulation results of long-term continuous runoff were good as well. The simulated variation of groundwater level with the recharged quantity was basically consistent with the measured value. With the continuation of intermittent ecological water conveyance downstream of the main stream, the groundwater level in the lower reaches has risen remarkably, but the lower section of the ecological corridor has a small uplift. In 2004, the average groundwater depth of downstream groundwater was about 6. 21 m, and it was expected to reach 4. 73 m in the planning year. The coupled model can accurately simulate the process of surface runoff and groundwater dynamic change, which is significant for the joint evaluation and comprehensive management of water resources.

Abstract:Three aquatic plants, Foxtail algae, Hyacinth and Water lily, were collected from natural wetlands, and the bacterial community attached to the surface of each plant was analyzed by the high-throughput sequencing. The seasonal succession of bacterial community structure was explored, and the influence of environmental factors on the change of community was also analyzed. The results show that: (a)Cyanobacteria, Proteobacteria, Bacteroidetes and Actinobacteria were the main bacteria adhering to these aquatic plants. The community structure of bacteria adhering to the surface of the three aquatic plants was similar at the phylum level, while the abundance and succession characteristics were different at the generic level, which are mainly related to the plant stem and leaf area, the plant secretion and the photosynthetic intensity. (b)At the generic level, the seasonal succession of bacterial community attached to three aquatic plants is a spontaneous process with a certain direction, which is not limited by the external single factor and is the affected result of host plant and external water environment. (c)Through the cluster analysis, it was found that the effect of environmental change on the community structure of attached bacteria was higher than that of plant species. CCA analysis of environmental factors showed that temperature, pH and TN were the main factors affecting the succession of attached bacterial community of aquatic plants.

Abstract:In order to improve the accuracy of flood forecasting, the paper proposes a retroactive correction method for the whole intermediate state variables of a sub-basin based on the ensemble Kalman filter. According to the different geomorphic feature and confluence time of each sub-basin, its corresponding retroactive time is found, and then, the Xinanjiang model is combined with to correct the state of each sub-basin before a certain time, gradually reducing the accumulation of errors. The results of the ideal model show that the intermediate state of sub-basin is effectively corrected, relative error of peak and volume decreases, and the deterministic coefficient increases. 12 historical floods of the Dapoling Basin, selected as an example, are effectively modified by the proposed method. As a result, the method can effectively improve the accuracy of flood forecasting and can be widely used in actual flood forecasting.

Abstract:The design values of the materials’ property parameters were adopted customarily in researches by far, which failed to take the influences of construction quality into account. A method for the seismic response analysis of RCC dam considering the influences of construction quality is proposed in this paper. Firstly, based on the real-time monitoring data of compaction quality of RCC dam, the physical and mechanical parameters under the impact of construction quality were analyzed; then, a finite element model considering the influences of the construction quality was established; finally, combined with a practical project, the seismic responses were calculated. The results show that the influences of the construction quality on the seismic responses can be analyzed with this method, and thus, it can provide more scientific evidences for the anti-seismic design of RCC dam.

Abstract:This paper analyses the scouring types occurring at bridge piers and the dynamics triggering mechanism of local scour, summarizes the influencing factors and research methods of scour around a bridge pier, and discusses the difficulty and challenge in investigating local scour and potential future research areas. This review can be a useful reference for scientists and technicians to deal with the scouring issue around bridge pier.

Abstract:In order to calculate the multi-axial strength of concrete and design a concrete structure considering the multi-axial strength of concrete, a general method for calculating the multi-axial strength under an arbitrary multi-parameter strength criteria is presented in this paper by using the overload factor of equivalent ratio, K_OL. Taking a completed arch dam as an example, the equal proportional overload factor, K_OL, and the failure distance factor, K_FD, are calculated, respectively, and compared with the safety factor of uniaxial strength. Then, the necessity of designing a concrete arch dam according to the multi-axial strength is pointed out. Based on the definition of K_FD and the analysis of an example, it is suggested that K_FD should be consideredas an index for the safety design and the checking of multi-axial strength of arch dams.

Abstract:In order to further verify the safety degree of the longitudinal reinforced rockfill dam against the flood overtopping damage compared with the conventional rockfill dam dam, this paper analyzes the erosion of downstream rockfill caused by the flood overtopping based on relevant experiments, during which the downstream material is washed away forming a scour hole that is partially exposed to the air at the downstream side. Besides, the safe operating mechanism of the reinforced dam is also obtained from the experiments. The advantage of this new dam is changing the conventional overtopping failure mode to the progressive scour hole development mode, therefore it can delay the dam breaking, and provide additional time for the repair and evacuation. Calculations show that, whether the reinforced body will fail depends on the scour depth and its ultimate stress distribution.

Abstract:On the basis of quantitatively analyzing the relationship between compaction quality and compaction parameters, a comprehensive optimizing model with objectives of construction effectiveness, compacted density, and quality guarantee rate has been established in this paper. An adaptive t distribution mutation-firework algorithm(ATM-FWA)for the model was presented to achieve the economically reasonable compaction parameters for the construction of high earth-rock dam. The proposed method can contribute to search a reasonable compaction parameter scheme with less field compaction tests. A case study shows that ATM-FWA has more advantages than the traditional optimal methods in the convergence performance, searching effectiveness, and solution stability. The compaction density and porosity of earth-rock dam material using the optimized compaction parameters can satisfy the design requirement. Thus, the proposed method provides a new way for the roller selecting and the compaction parameters optimization in the construction of an earth-rock dam.

Abstract:In order to study the mechanical properties of soil-rock mixtures dominated by the soil under a low rock content, the modeling method combining multi-layer method under compaction and random polygon generating method is adopted to establish the particle flow model of soil-rock mixture, and the inhomogeneous coefficient S is proposed as an index of the heterogeneity of soil-rock mixture. The mesoscopic parameters of the particle model were checked by a laboratory test, and the numerical simulation of the biaxial test was also carried out, for checking the effects of three factors on the mechanical properties of the soil-rock mixtures under the condition of low stone content, including the rock content, the porosity and the inhomogeneous coefficient S. In the case of low stone content, the strength of the soil-rock mixture is greatly influenced by the porosity of the soil. With the decrease of the soil porosity, the strength of the soil-rock mixtures is greatly improved. The existence of block stone destroys the uniformity and continuity of the soil. On the contrary, the overall strength of the soil-rock mixture decreases with the increase of the rock content. The inhomogeneous coefficient S has great influence on bulk strain. The greater the coefficient of heterogeneity is, the more obvious the expansion of volumetric strain is.

Abstract:To explore the application method of MICP in the actual project, the MICP grouting pipe is used to reinforce the soil in this study. That is to insert the grouting pipe into the soil through holes of different densities, then penetrate the bacteria fluid and the cementing fluid into the soil through the holes on the grouting pipe, and at last, the cemented sand column can be formed in the soil. By comparing the reinforcement effect of contrast experiments, the results show that this grouting method can be used to form a complete and high strength cemented sand column and the strength of each layer is relatively balanced.

Abstract:To obtain the fracture properties of three-point bending concrete beam with double cracks, 24 specimens were tested in this paper. The initial crack-depth ratio of the specimens with a single crack is 0. 4. For the specimens with double cracks, the initial crack-depth ratio of the main crack(MC)is 0. 4 and it is 0. 2~0. 4 for the secondary crack(SC), while the distances between the SC and MC are 120 mm and 160 mm, respectively. Based on the double-K fracture theory, the effect of the crack-depth ratio of SC and the distance between SC and MC on the initial load, the maximum load, and the P-δ curve were studied. The results indicate that, with the increase of the crack-depth ratio of the SC from 0 to 0. 4, the initial load of the specimens increased from 4. 65 kN to 7. 12 kN by 53. 1%, and the maximum load increased from 7. 37 kN to 8. 22 kN by 11. 5%. With the increase of the distance between SC and MC, the initiation load, the maximum load and the ratio of initial load to maximum load increased at first and then decreased. Meanwhile, values of them reached to the peaks when the distance was 80 mm. Compared to single crack specimens, the bigger the ratio of the SC, the larger the slope of the linear segment of measured P-δ curve; the larger the distance between SC and MC, the smaller the slope of linear segment.

Abstract:Based on the basic idea of the Kachanov method, the stress intensity factors for the interaction of isometric collinear cracks are computed. Moreover, according to the Mises failure criterion and the D-P failure criterion, the expression of the plastic zone radius at the crack tip and the expansion ratio of plastic zone radius under the crack interaction are derived based on the small-area yield condition under the uniaxial tension. The radius enlargement of the plastic zone is the square of the ratio of the stress intensity factor under the interaction of two cracks to the stress intensity factor of a single crack. And, the influence of crack spacing on the plastic zone expansion is also analyzed. The results show that, for a same inclining angle of crack, the plastic zone radius of crack tip increases with the decrease of crack spacing, and its increasing rate increase as well. For different crack angles, the contact conditions at the plastic zone of crack tip are also different. Therefore, the combination conditions of double cracks need to be determined according to the inclining angle of crack.

Abstract:In this study, based on the degenerated shell element theory, the displacement field of the element is deduced, and the nonlinear composite element mode of the reinforced concrete multi-T beam is established. The longitudinal carrying bar is treated by the space bar element and its contribution to the stiffness matrix of nonlinear composite elements is deduced. The material nonlinearity of concrete is considered by the four parameters’ Ottosen criterion, and the geometrical nonlinearity of the structure is taken into account by the V. Karman assumption to analyze the influence of geometrical nonlinearity on the structure. The typical example shows that the nonlinear combination element of reinforced concrete multi-T beam with double nonlinearities is in good agreement with the experimental data. The element can be used to correctly analyze the structure nonlinearity. When the partial load is loaded, the stress of the reinforced bar on the side beam develops more rapidly and reaches the yield stress firstly, while the stress of rest reinforced beams of all the main girders develops in sequence until the structure is destroyed. For reinforced concrete multi T beams, the effect of material nonlinear is evident, and geometrically nonlinear effect can be excluded within a certain range.