Abstract:A dynamic control model for construction progress of the storehouse surface of core rockfill dams is proposed based on thesimulation model for construction progress and thereal-time monitoring model for construction quality of the storehouse surface, with field construction factors taken into consideration. Through optimization of the construction scheme and real-time analysis and feedback of progress deviation during the construction process with the model, the construction progress control before and during the construction process was realized. The model was applied to a core rockfill dam under construction. An optimized scheme for advance control of construction progress of a storehouse surface was chosen based on optimization and simulation analysis of multiple construction schemes. When the construction progress was stunted by unforeseen circumstances, the simulation model for storehouse surface construction was used to dynamically simulate and update the construction situation, and an optimized scheme for intermediate control of construction progress wasrecommended. The schedule of storehouse surface construction can thus be guaranteed. The application results showed that the actual construction scheme was consistent with the chosen one, only with a deviation of 23 minutes in the construction process. Therefore, the storehouse surface construction progress could be effectively controlled with the dynamic control model. As conclusions, the model can provide a reasonable and optimized construction scheme, effectively control the deviation in construction progress, and guarantee the construction progress of a storehouse surface of core rockfill dams.

Abstract:Through establishment of a two-dimensional cellular automata model, the evolution process of delta accumulation in inland rivers after a mountain river flows directly into open lake areas was examined. The development process of delta accumulation and the evolution laws of alluvial channel morphology on the accumulation surface were analyzed. The whole pattern was determined: first longitudinal forward, then vertical deposition uplift, and finally lateral spreading. The longitudinal forward rate decreases with the increase of the simulation steps, a gradual deposition uplift occurs in the vertical direction, and the rate of lateral spreading decreases with the increase of the simulation steps. The channel morphology evolution on the accumulation surface can be divided into three stages: the straight channel, braided channel, and micro-bend channel. The simulated results agree with existing experimental results of the physical model, indicating that the cellular automata model can be used to simulate the evolution process of the delta.

Abstract:In order to efficiently utilize the ultra-low head water resources, an axial flow turbine with a siphon outlet conduit was designed, and three-dimensional CFD numerical simulations were conducted with the design head and rated runner speed. The hydraulic loss of each flow passage component was calculated to study the hydraulic performance of the siphon turbine. The relationship between the flow regime at the runner outlet and the head loss of the outlet conduit was analyzed by changing the runner blade airfoil, and the influence of different runner blades on the hydraulic performance of the siphon turbine was studied. The results show that, with a constant water head, runner speed, and guide vane opening, the head loss in the outlet conduit of the turbine in the modified scheme with the third blade is at a minimal value of 0. 135 m, the corresponding average swirl angle is 13. 26o, and the turbine efficiency is at the maximum(89. 33%). In addition, the influence of the number of blades on the hydraulic performance of the siphon turbine was analyzed through selection of the blade with the maximum efficiency.

Abstract:To verify the applicability of the pull-out method in strength testing of ultra-high strength concrete, the cast-in-place pull-out method and post-install pull-out method were used to test the strength of ultra-high strength concrete. The strength of test pieces was graded at threelevels, C120, C150, and C180, and six groups of test pieces and a certain number of test cubes were selected for each strength level. Through experimental data fitting with the least square method and calculation of various parameters of the regression equation, some conclusions are drawn: all kinds of parameters are within reasonable ranges, and the pull-out method is suitable for testing the strength of ultra-high strength concrete. Comparison of data from different pull-out methods shows that, for the same kind of material, the cast-in-place pull-out method has higher accuracy, the strength curve of ultra-high strength concrete has a similar trend to that of steel fiber cement mortar, and the strength detection range of the post-install pull-out test is wider than that of the cast-in-place pull-out test.

Abstract:In order to investigate the seismic performance of the joint of a new PEC column-steel beam frame with a partial self-centering BRS energy-dissipation connection, the axial compression on the top of the PEC column and its layout were taken into consideration to design three reduced-scale specimens, and tests were conducted with low-cycle reversed lateral loading. Based on the experimental results, the seismic mechanisms of specimens were analyzed in terms of the load-carrying capacity, bending stiffness degradation, self-centering function, energy-dissipation capacity, and force-transfer mechanism of the joint. The results indicate that: (a)Partial self-centering BRS connectivity can provide self-centering functionality through dissipation of earthquake energy and reduction of structural response, and the main components are in the elastic state throughout the loading process. (b)The axial compression on the top of the PEC column significantly increases the initial bending stiffness, and accelerates the energy dissipation process, while the layout of the PEC column has little effect on the initial bending stiffness, stiffness degradation, and energy dissipation process. (c)The residual drift angle of specimen SYJ1 is less than 0. 005 rad when the loading drift reaches the interstory drift limit of 1/50 at the medium earthquake level and 0. 01 rad when the loading drift reaches the interstory drift limit of 1/30 at the maximum earthquake level, indicating its sound self-centering functionality. The self-centering functionality of specimen SYJ3 is slightly inferior to that of SYJ1, and the self-centering functionality of specimen SYJ3 is strong before the loading drift reaches the interstory drift limit of 1/50, but degenerates significantly in the late stage of loading.

Abstract:Four composite walls with double steel plates and filled concrete were tested under axial compressive loads, and the effects of the strength and distance-to-thickness ratio(the ratio of the distance between shear connectors to the steel plate thickness)of a steel plate on the local buckling position, critical loading, and failure modes were analyzed. Test results indicate that local buckling tends to occur in the middle between two vertical connectors and in the middle part of the area surrounded by four connectors. The limit value of the distance-to-thickness ratio that prevents local buckling failure from occurring before yielding failure decreases with the increase of the strength of steel. The distance-to-thickness ratio has a significant influence on the failure mode and critical load of local buckling. Based on the analysis of experiments, the formula for the limit value of the distance-to-thickness ratio that prevents local elastic buckling failure was derived. The applicability of the formula was verified by the existing experimental data and numerical analysis, and the formula was further modified.

Abstract:The multi-channel combined with low negative pressure dynamic compaction method was used to reinforce the ground in the Tongzhou Bay Science and Entrepreneurship Town in the coastal zone of Nantong. The change process and characteristics of ground water level, surface settlement, horizontal displacement of deep soil, pore water pressure, and vacuum degree were analyzed. The main physical properties, soil strength, and bearing capacity of the treated foundation were tested and evaluated. The results show that, the underground water level in the field can quickly drop to less than 3 m under the condition of continuous rainfall, a negative pressure condition was formed within a depth of 7 m using the vacuum method under the non-seal condition, and super static pore pressure caused by dynamic compaction can rapidly dissipate in 2 to 3 days. Influence of dynamic compaction was mainly based on settlement compression, the lateral displacement was small, and the physical and mechanical properties of soil were improved significantly, with the effective depth reaching 6. 5 m and the characteristic value of bearing capacity of foundation reaching 80 kPa. The new technology can enhance the ability of water drainage and the rapid dissipation of super static pore pressure. It is worth popularizing and applying in areas of abundant groundwater and rainfall.

Abstract:In order to improve the durability of foamed mixture lightweight soil(FMLS), the analytic hierarchy process(AHP)and fuzzy comprehensive evaluation(FCE)were combined to comprehensively evaluate the durability of FMLS. Based on the physical and mechanical properties of FMLS, the influencing factors were selected from the point of view of preliminary design, construction technology, and operation management, and the grade classification of influencing factors was established. The comprehensive evaluation model of FMLS’ durability was established based on the target layer, criterion layer, and index layer. The weight of the lower layer relative to the upper layer was determined by the AHP, and the consistency check of the judgment matrix was conducted to prove the rationality of the distribution of influencing factors’ weight. The membership function suitable for each influencing factor was built to calculate the membership degree, and the specific method of fuzzy comprehensive evaluation is presented. Using the lightweight soil subgrade in the charging island along the S03 section of a highway in Guangdong Province as an example, its durability was evaluated, demonstrating the practicality and reliability of AHP-FCE.

Abstract:In order to improve the accuracy of groundwater transport simulation, groundwater resources assessment, and land subsidence prediction, the variation of hydraulic parameters of an aquitard during water release was analyzed through laboratory testing. Based on the analytical solution of the water release quantity of an aquitard under the condition that the drawdown of the adjacent aquifer is constant and the flow in the aquitard is stable at the initial time, a type curve method for calculation of parameters is proposed, and experimental research was carried out using the self-developed test equipment. The experimental results show that the hydraulic conductivity and specific storativity decrease gradually with the water release from the aquitard, but the consolidation coefficient changes little. The hydraulic conductivity and specific storativity of the soil layer in the experiment were decreased by 52% and 59%, respectively. The assumption that hydraulic parameters are constant will lead to a significant error in the calculation of the water release quantity of the aquitard. The calculated water release quantity of the aquitard is larger than the actual value when the specific storativity in the initial stage of consolidation is used, but the opposite conclusion is obtained when the specific storativity in the final stage of consolidation is used.

Abstract:In order to investigate the composition of particle size of surface sediments in shallow lakes, the response of particle size distribution to the source and hydrodynamic characteristics of sediments, and the distribution characteristics of nutrients in sediments of shallow lakes, the particle size of sediment samples from four shallow lakes with different sizes and shapes in the Lixiahe Region were studied. The results are as follows: (a)The average particle size of the surface sediments in the study area decreases with the increase of depth. (b)The vertical distribution of the median grain diameter of the surface sediments in large lakes is significantly different. (c)The transportation capacity for sands of large and wide lakes is stronger than that of small and narrow lakes. (d)For a large lake, the sand content in the central area is higher than in the surrounding area of the lake. (e)The triangular distribution chart of particle size shows that the surface sediments mostly fall into the categories of silt loam and sandy loam, indicating that the hydrodynamic activity of the lakes in the study area is strong. (f)Poor continuity in the vertical distribution of sediments occurs in Jiulongkou Lake with a large amount of wind disturbance. (g)The vertical distribution of the average particle size of sediments in Wugong Lake and Desheng Lake does not change significantly, indicating that hydrodynamic conditions rarely change. These results agree with the field investigations.

Abstract:In order to strengthen the flood management of medium and small rivers, a hydrological model, a Mike11 model, and a Mike21FM model were established. One- and two-dimensional hydrodynamic models were coupled using Mike Flood and were used to analyze the flood and waterlogging risks of medium and small rivers. Using the left bank area of the Fuxin River in Fengxian County of Xuzhou City as an example, a numerical model of flood routing was established to analyze the flood control capacity of the Fuxin River and the waterlogging of the study area during different rainstorms. The results show that the flood control capacity of the study area can meet the 20-year return-period flood control standard. The drainage capacities of some medium and small rivers were so poor that some regions showed serious waterlogging.

Abstract:In order to distinguish trends and abrupt changes in hydrological time series, the generalized LASSO model based on L₁-norm regularization was used to detect changes in hydrological series. It is found that the annual mean streamflow series at the Cuntan Station shows a downward step change in 1969. Furthermore, trend analysis shows that both the sub-series before/after 1969 and the whole series after removing step change components show no significant trend, indicating that the assumption of the step change in the annual mean streamflow series at the Cuntan Station is reasonable. The conclusions obtained from the generalized LASSO method are consistent with those obtained from other change detection methods.

Abstract:Based on hydrological and meteorological data, the composition of hydrogen and oxygen isotopes in precipitation, surface water, and stream water were investigated for three typhoon events in the flood period of 2015 in the Hemuqiao Watershed, and the δ²H-δ¹⁸O relationship in precipitation was studied. The results show that the composition of hydrogen and oxygen isotopes in precipitation exhibited significant temporal variation. With the increase of the duration of rainfall, the δ¹⁸O values of the incremental rainfall with the same volume and rainfall during the same period had a decreasing trend. Throughfall, rather than rainfall, enriched heavier isotopes because of the canopy storage and isotopic fractionation. Rainfall was the main supply source of stream water. The contents of heavy isotopes in stream water were more abundant than those in precipitation and surface runoff due to the evaporation of stream water.

Abstract:Under the conditions of no evapotranspiration and soil water hysteresis, a simplified slope model was established for single-layer homogeneous and isotropic soil profiles on a trapezoid slope with infinite depth for different initial water contents. The Hydrus software, which was used to numerically solve Richards’ equation, was used to investigate the effects of slope gradients on the Horton runoff generation process during temporally and spatially uniform rainfall events. The results show that the runoff on the slope decreases with increasing slope gradients; increasing initial water contents may reduce the influence of slope gradients on runoff; and the relationship between runoff and slope gradients can be well approximated using power functions.