Abstract:Based on the time-series production simulation method which takes into account the time-series variation characteristics of system load and power generation output of new energy, the time-series production simulation model of hydro-optical power system is established. The optimal water-light capacity ratio is determined comprehensively from the aspects of system structure, economy, flexibility and reliability, and the rationality of the model is verified by the water-light system of the upper reaches of the Jinsha River in the Sichuan-Tibet section. The outputs of photovoltaic power stations and hydropower stations in the upper reaches of the Jinsha River are complementary within a year and within a day. For the level year of 2030, considering the retention of hydropower during dry period, the comprehensive performance of 9.136 million kW hydropower with 4 million kW photovoltaic is better, and the new non-water renewable electricity is about 6 billion kW·h.

Abstract:To understand the response patterns of water quality in the front pond of drainage pumping station to rainfall characteristics, the high-frequency online automatic monitoring was carried out for water quality and rainfall at two drainage pumping stations along the Qinhuai River in Nanjing City. The regression tree method was used to analyze the variations in the water quality (ammonia nitrogen and CODMn) of typical urban drainage pumping stations under different rainfall intensities and previous drought duration conditions, and the main influencing factors of water quality for different types of drainage pumping stations were explored. Taking ammonia nitrogen as an example, the concentration in the front pond of drainage pumping station A, which receives the domestic sewage inflow during both rainy and non-rainy days, decreases under heavy rain intensity, increases first and then decreases under moderate rain intensity, and gradually rises under light rain intensity. The water quality concentration in the front pond of drainage pumping station A is mainly affected by the rainfall intensity and secondary rainfall. The water quality concentration in the front pond of drainage pumping station B, which mainly receives the rainfall runoff but also has the inflow of domestic sewage during heavy rainfall, firstly increases and then gradually decreases under heavy rain intensity, decreases under moderate rain intensity, and has little change under light rain intensity. The water quality concentration in the front pond of drainage pumping station B is mainly affected by rainfall, previous drought duration and rainfall intensity. The response patterns of CODMn concentration to rainfall in the front pond of the two pumping stations is similar, but the concentration of CODMn is more affected by the surface runoff erosion associated with previous drought duration. Continuous rainfall causes large fluctuations in the concentration of ammonia nitrogen and CODMn in the front pond of drainage pumping stations, and longer previous drought duration results in worse water quality in the front pond of drainage pumping stations after rainfall events.

Abstract:In order to improve the efficiency of parameter optimization for complex hydrological models, sensitive parameters are determined through the Morris parameter sensitivity analysis. Subsequently, the multi-objective adaptive surrogate model optimization (MO-ASMO) algorithm is applied in the parameter calibration of the TOPKAPI model. The relative optimal solutions in the Pareto solution set are then selected based on the minimum Euclidean distance. The performance of MO-ASMO is compared with traditional multi-objective optimization methods, such as NSGA-II and NSGA-III, from two dimensions in terms of solution set distribution and simulation effectiveness of each flood event. The results indicate that, under the same number of model runs, MO-ASMO has a superior Pareto front compared to NSGA-II and NSGA-III. Both in the calibration and validation periods, the evaluation indicators of the MO-ASMO algorithm show better performance, overall surpassing the NSGA-II and NSGA-III algorithms, and as a result, the MO-ASMO algorithm effectively improves the efficiency of model parameter optimization.

Abstract:The triaxial wetting test in single line method of rockfill materials with different initial void ratio was carried out, and the varies of wetting deformation with the confining pressure, stress level and initial void ratio were analyzed. The test results show that the axial and volumetric wetting deformation decreases with the decrease of the initial void ratio under the same confining pressure and stress state. Based on the test results, it can be found that the initial void ratio has little influence on the dilatancy law of wetting stress, and the logarithmic wetting dilatancy equation can be used to describe the wetting stress dilatancy relationship under different initial pore ratio conditions. In addition, the model for the axial wetting deformation with the consideration of initial void ratio and stress state was proposed by modifying the empirical exponential model. After that, the equation for the volumetric wetting deformation was derived by the stress-dilatancy equation. Finally, the rationality of the proposed model was validated according to the comparison with test results.

Abstract:To address the problem of quantitative evaluation of the preferential flow model under the desiccation cracks, based on the double pore domain infiltration theory, this paper proposes a new preferential flow model considering the dynamic changes of desiccation cracks with the combination of Green-Ampt infiltration model. In the proposed model, the cracked soil is separated into matrix domains besides the cracks (L-matrix domain), under the cracks (B-matrix domain) and crack domain. Then, the effects of rainfall intensity, initial crack area ratio, and crack depth on the water ponding time, infiltration amount and depth of preferential flow are simulated and discussed. The results show that infiltration amount of preferential flow produced by desiccation cracks occupies 73.4% to 91.4% of the total precipitation. Its ultimate infiltration depth during rainfall is 3.1 to 7.2 times deeper than the crack depth. With the increase of rainfall intensity, the water ponding time of matrix domain decreases and the infiltration depth of preferential flow increases. During rainfall, the decreased crack area ratio leads to the decrease of infiltration amount of preferential flow. Moreover, it is found that with the increase of initial crack area ratio, the infiltration amount of the L-matrix domain decreases and the preferential flow infiltration increases, whereas its infiltration depth decreases. The increased crack depth mainly delays the water ponding time of the crack domain and increase the infiltration depth of preferential flow. In conclusion, the simulated results are consistent with the practical infiltration process within the desiccation cracks, and it also avoids errors and inconvenience caused by the defining hydraulic property of cracks.

Abstract:The paper combines the balanced octree with polyhedron mesh trimming based on the image octree method, and proposes a mesh generation algorithm of polyhedron in the 3D scaled boundary finite element method. According to the size of the structure, a cube grid is built to exactly include the whole structure, and then the pixel information of the structure image is formed. Then, according to the principle of 2∶1 balanced partition, the grid is divided recursively to realize the fast transition of mesh, and the balanced octree mesh can be generated. The internal elements are completely preserved while the external elements are removed. For the mesh of the boundary element, the surface-cube intersection method is proposed to screen the intersection surfaces of boundary element and structural boundary, and the intersection points between boundary element and structural boundary surface are searched to form a new element surface. The cut surface of the boundary element is formed by connecting the intersection points in order, and then combined with other surfaces of the boundary element to form the cut polyhedron element. Two numerical examples show that the calculated results of the scaled boundary finite element mesh generated by the proposed method have good accuracy and boundary adaptability.

Abstract:In order to enhance the safety and intelligence in the tunnelling of hard rock tunnel boring machines (TBM), this paper proposed a prediction model (BiLSTM-SVR model) that combined the bidirectional long short-term memory (BiLSTM) neural network with the support vector regression (SVR) algorithm, and the proposed model was capable of concurrently predicting surrounding rock grades and TBM tunnelling parameters based on the TBM tunnelling data. Example verification results show that the BiLSTM-SVR model demonstrates high accuracy in predicting surrounding rock grades, with the root mean square error (RMSE) and the mean absolute percentage error (MAPE) both being less than 0.026 5 and 0.95%, respectively. In the prediction of tunnelling parameters using the BiLSTM-SVR model, the accuracy in predicting thrust and torque is the highest, while the accuracy in predicting net excavation speed and excavation efficiency is the lowest. The proposed model exhibits significantly improved accuracy in predicting tunnelling parameters compared to the BiLSTM model and the SVR model individually, thereby combining single model effectively enhances the accuracy and robustness of model prediction.

Abstract:An improved permeation device was developed for the experimental investigation of the influence of different skeleton particle compositions with the consistent content of fine particle ranging (0.075 to 1 mm) on critical conditions of piping, erosion pattern and loss pattern of particles in the granular soil. The results show that for samples with different particle gradations, the hydraulic gradient and the seepage velocity exhibit a linear relationship before piping occurs, which essentially complies with Darcy’s Law. Skeleton particles in the size ranges of 1-2 mm, 2-3 mm, and 3-5 mm impede the development of piping, with particles in the 1-2mm range demonstrating a stronger blocking effect on piping voids than particles in other two size ranges. For skeleton particles of different gradations, the larger the heterogeneity coefficient, the larger the lower limit of the critical hydraulic gradient for the sample, making it more difficult for fine particles to be mobilized, and thus delaying the onset of piping. Conversely, the influence of the skeleton particle gradation on the upper limit of the critical hydraulic gradient of the sample is relatively minor.

Abstract:By setting up six groups of specimens and using the rainfall test, the resistance of modified silt slopes to rain erosion was analyzed through the changes in the surface erosion condition of specimens with respect to the amount of erosion, surface strength and calcium carbonate content. The results show that after spraying the enzyme induced carbonate precipitation (EICP) solution on the surface for EICP and lignin joint-modified samples, the surface integrity is better, the strength and calcium carbonate content are higher, the quality loss is smaller, and the resistance to rain erosion is improved obviously. As results, the erosion amount of the slope soil is reduced by 75.0% on average compared with other specimens, the surface strength is increased by 33.8% on average, and the calcium carbonate content is increased by 235.2% on average. The slope surface sprayed with EICP solution can form a hard shell layer that effectively avoids the erosion of the slope surface, while lignin can provide nucleation sites for the calcium carbonate. Therefore, the distribution of scattered calcium carbonate attaches to lignin, so that the addition of lignin improves the calcium carbonate content and the surface strength also increases with the increase of calcium carbonate content.

Abstract:In order to understand the disturbance and deformation characteristics of clay during the penetration of soil sampler, the novel transparent clay made by Aristoflex AVC and the particle image velocimetry (PIV) technique were used to carry out the penetration tests of soil sampler with different sizes through the visual model test device. The test results show that the deformation distribution characteristics of soil in different sections are nearly the same, and the deformation decreases as it distances away from the tube wall. The soil at the lower part of the sampler has good integrity, and the shear strain of the soil within about 0.19 times the core diameter from the central axis of sampler is small, which is suitable for doing the laboratory experiment. Sampler penetration disturbance is mainly caused by the frictional resistance of the sidewall and the squeezing effect of edged foot, so increasing the inner diameter of soil sampler can effectively reduce the compressive deformation of soil in the sampler.

Abstract:The motion and diffusion behaviours of multiple jets in wave-current environment were studied by using a 3D large eddy simulation model, and the diffusion and dilution mechanism of jets in wave-current environment was discussed. Then, the influence of hole spacing on the interaction between two-hole jets and environmental water was analyzed and the optimal relative hole spacing was given. The simulation results showed that, due to the strong interaction between cross-flow and wave, the three-dimensional vortices in the flow field at the wave trough phase are rich in structure, large in scale and numerous in number, which is conducive to the mixing between jets and environmental water, and between jet and jet. Hence, the multiple jets in wave-current environment have a better dilution than that in current only environment. With the increasing of hole spacing of dual jets, the interaction between the two jets becomes weaker while the interaction between jets and environment water becomes stronger. The best dilution effect of two-hole jets is obtained when the hole spacing is 7.0 times of the jet diameter.

Abstract:Based on the concept of treating waste with waste, this paper proposes a new idea to solidify the dredged sludge with the improved municipal solid waste incineration (MSWI) bottom ash. Laboratory tests were carried out to measure the moisture content, unconfined compressive strength and shear strength parameters of solidified dredged sludge. The results show that the best solidification effect is obtained when the pulverized powder and the unground powder of the MSWI bottom ash are mixed at 1∶1. Under the condition of the optimal mixture ratio, the unconfined compressive strength, cohesion and internal friction angle of the solidified dredged sludge increase with the increase of the curing times and the content of improved MSWI bottom ash, while the change trend of moisture content is on the contrary. When the content of the improved MSWI bottom ash is 35%, the unconfined compressive strength of solidified sludge after 28 curing days can reach 58.4.kPa, and the moisture content decreases from 67.4% to 38.0%, which proves the feasibility of using the improved MSWI bottom ash to solidify the dredged sludge.