Abstract:Based on the innovative trend analysis(ITA)method, this paper improved the parametric test method of trend significance, proposed a quantitative index to describe the average trend of time series, and used the bootstrap method to test the significance of the trend. After the Monte-Carlo numerical simulation, the detection results of the new method on the artificial data sequences were compared with the classic Mann-Kendall(MK)method and ITA method respectively, from which its feasibility was verified. Finally, the new method was applied to the trend analysis of four kinds of time series with different lengths, in different regions, and about different hydro-meteorological elements. The results showed that at the 5% significance level, there was a significant increasing trend in series of the annual runoff in the upstream of Heihe River, the number of storm days per year in Fukuoka, Japan, and the annual average temperature in Qionghai. Meanwhile, there was a significant decreasing trend at a significant level of 10% in the maximum daily precipitation in Beijing.

Abstract:In order to study the influence of road slope(1%-2% in cross slope and 0. 3%-5. 0% in longitudinal slope)and runoff of 0-70 m³/h on the inlet efficiency, tests were carried out on a 1∶1 platform. Experimental results show that the inlet efficiency decreases with the increasing of flow rate as well as the longitudinal slope. However, when the cross slope increases 0. 5%, the efficiency increases about 10%. In addition, experimental data were fitted with the orifice equation. Comparison was conducted between the fitting formula and previous empirical formulas, and the results show that the proposed formula gives better results on the standard flat-grate street inlet. Based on the fitting formula, a new method for the street inlet design is proposed for the future urban road construction and formulas for determining the inlet spacing are deduced, which were adopted for the optimal design of inlet spacing.

Abstract:This paper proposed an optimal algorithm for the calculation of urban runoff direction based on Cellular Automata(UCA). The optimal water distribution weights that is suitable for different flow patterns are selected by the flow simulation experiments on slopes. The UCA, D8, 4+4N and FMFD algorithms are used to calculate the Specific Catchment Area(SCA)on four mathematical surfaces, and the results of four algorithms are compared. The relative error(RE), root mean square error(RMSE)and mean absolute error(MAE)are chosen to evaluate the performance of four algorithms. The results showed that the optimal water distribution weights of UCA algorithm for the converge flow and the diverge flow are 2. 0 and 1. 1 respectively, and the RE and RMSE between the UCA simulated and theoretical values of SCA are the smallest on convex slopes, concave slopes, ridges and plane slopes. The UCA algorithm is suitable for the diverge flow on urban flat terrain and the converge flow on terrains with steep hydraulic gradient, which can provide a better solution for the simulation of urban runoff.

Abstract:To quantitatively assess the influence of multiple factors on the dynamic change of ground water in the piedmont plain of the North China, this paper selected a typical well irrigation area in Luancheng of Shijiazhuang City as the study area and analyzed the main influencing factors of the dynamic changes of groundwater level from the perspective of water balance. The principal component regression analysis method was used to exclude the interaction between main influencing factors and the contribution rate of each comprehensive factor to the groundwater level rise was analyzed quantitatively. The principal component-time series model was established to predict groundwater level changes in the piedmont plain of the North China under the influence of multiple factors. The results showed that the groundwater was mainly affected by local climatic factors, local human activities and human activities in the upper reaches in Luancheng from 1994 to 2015. The contribution rate of each influence factor on the recovery of groundwater level was 11. 7%, -50. 9% and -37. 4% respectively. The main factors that played a leading role in these three aspects were the precipitation in Luancheng, sowing area of wheat and corn in Luancheng, and the population of Shijiazhuang City in the upper reaches of Luancheng. In the past 20 years, the climate change was conducive to the recovery of groundwater resources in Luancheng, but human activities played a leading role in the problem of groundwater resources.

Abstract:This study employed several approaches to extract key geographic elements(i. e. , aquaculture area, submerged vegetation, floating-leaved vegetation, marsh and cultivated land)using the 37 Landsat image data from 1977 to 2020. Thereafter, the evolution process of geographic elements in the Gaobaoshaobo Lake was analyzed from the temporal and spatial dynamic evolution of elements in long time series. The main conclusions are as follows: As a whole, the area of aquaculture areas increased first and then decreased, which was mainly affected by the policy regulation. Potamogeton crispus is a dominant species of aquatic vegetation and has grown explosively to block waterways since 2010. The cultivated land was mainly disturbed in the north of Gaoyou Lake, and the area increased first and then decreased. Most of the marsh was disturbed in the north and near the coast of Gaoyou Lake, and the area of marsh is decreasing. Both are mainly converted into aquaculture areas. The change hotspot is located in the north of Gaoyou Lake, and driven by the policy regulation and economic interests, the transformation among marsh, cultivated land and aquaculture area is quite significant.

Abstract:In order to solve that the traditional structure decomposition method cannot consider the simplicity of formula and the uniformity of factor changes at the same time, in this study the structure decomposition method was improved and applied to the research on the water driving effect of Taizhou City, the representative city of water saving. The research results show that the scale of industrial water consumption in the region has dropped by 9. 14% in the past five years. Technical effects are the main contributor to Taizhou’s water-saving benefits. The scale effect is the main driving factor leading to the growth of industrial water consumption in Taizhou. Contrary to technical effects, structural effects that have the inhibitory effect of the growth of industrial water consumption in various regions are showing a steadily weakening trend, but there is still great potential for structural effects in economically underdeveloped regions. Based on the GDIM decomposition results, the two structural decomposition methods can draw similar conclusions as a whole, while the traditional structural decomposition method will produce excessively high evaluations of contributing factors for some areas where water use factors change drastically. The improved structural decomposition method is more accurate both in terms of calculation results and in economic sense, and is suitable for water-saving construction periods when water usage fluctuates volatility and economic influencing factors are complicated.

Abstract:Laboratory experiments using an undisturbed sediment core were conducted to explore the effect of organic matter(humic acid)on the nitrogen transformation and the nitrate reduction pathway in the hyporheic zone of Lake Taihu. Results show that, when only the nitrate was input along with the downwelling flow, nitrate reduction rates were 0. 087-0. 186 μg/(cm³·d)with an average of 0. 162 μg/(cm³·d), and the nitrate apparently accumulated in the hyporheic zone. Both the humic acid and the nitrate input along with hyporheic flow gradually promoted a reduction environment in the hyporheic zone within 21 days with Eh of below -200 mV. Nitrate reduction was greatly enhanced under this condition with an average reduction rate of about 0. 220 μg/(cm³·d)from 0. 092 to 0. 251 μg/(cm³·d). These indicated that added humic acid substantially promoted the nitrate reduction process. At a shallow depth of the hyporheic zone(0-22. 5 cm), the contribution of denitrification to the nitrate reduction reached more than 90%, indicating that the denitrification was the main pathway of nitrate reduction. At the deep depth of the hyporheic zone(22. 5-45. 0 cm), due to the deficient nitrate source, the contribution of nitrate reduction to the whole hyporheic zone accounted for less than 10%, and the denitrification accounted for about 39. 5%. Dissimilatory nitrate reduction to ammonium, as a secondary pathway of nitrate reduction, was obviously influenced by organic matter content, and its contribution to nitrate reduction decreased from 14. 0% to 2. 7% when organic matter concentrations decreased from 6. 92 mg/L to 3. 32 mg/L. Overall, supplementary organic matter was helpful for the nitrate reduction mainly by denitrification particularly at the shallow depth of hyporheic zone, playing a great role on the cycling and removing of carbon and nitrogen in a lake aquatic system.

Abstract:To reveal the effect of in-situ coverage of nano materials on heavy metals in surface sediments, the incubation experiments of in-situ sediment columns were carried out. Using micro-interface analysis technique, the high-resolution dialysis(HR-Peeper)technique and the diffusive gradients in thin films(DGT), the influence mechanisms of in-situ coverage of Fe₃O₄ nanoparticles on the release of Co and Ni from surface sediments were dissected. The results shows that the pH of the sediment covered by the nano-Fe₃O₄ gradually increased compared to that of the control group, while the Eh value decreased first and then increased. The coverage of nano-Fe₃O₄ can effectively adsorb the dissolved Co and the dissolved Ni in the pore water, and the maximum effective adsorption rates of dissolved Co and dissolved Ni in the pore water were 27. 07% and 26. 42%, respectively, with effective effect depths of 30 mm and 10 mm, respectively. The coverage of nano-Fe₃O₄ effectively inhibit the diffusion of labile Co/ Ni in sediments to overlying water and reduced the content of labile Co/Ni in sediments by 50. 26% and 15. 31%, respectively.

Abstract:In this paper, a landslide safety evaluation model is established based on the cloud model and the improved D-S evidence theory. With the basis of multi-source information fusion theory, combined with the safety monitoring data and landslide deformation and damage characteristics, a perfect landslide safety evaluation system is constructed, the cloud model is applied to generate the affiliation degree of each evaluation index, and the improved D-S evidence theory with the introduction of weight coefficients is used for the data fusion analysis to realize a comprehensive evaluation of landslide safety. The safety evaluation analysis of Zhoujia landslide in the Yalong River Kala Hydropower Station is studied as an example, and the safety status of the Zhoujia landslide is determined according to the principle of maximum affiliation. The results show that the whole area is in a basically stable state, while area B1 is in a unstable state, which is basically consistent with the actual status.

Abstract:In this paper, the index of aggregate distribution uniformity, uniformity, was defined and the corresponding calculation formula was provided. Thereafter, a pixel-based digital algorithm for uniformity was established by using the discrete element principle and EDEM software, and the rationality and correctness of uniformity were verified by multiple numerical examples. The results showed that the uniformity proposed in this paper had a clear physical meaning, values of which were between 0 and 1, and the uniformity of aggregate distribution increased with the uniformity. The regularity of the calculation results by means of uniformity correlated well with those by other methods. Meanwhile, the uniformity was more in line with the people's conventional way of thinking, and could reflect the uniformity degree of particle distribution quantitatively and accurately in the mixing process. In addition, the mechanical interaction between aggregates in the mixing process was also considered. Therefore, some phenomena, for example, the decrease of uniformity caused by the floating of lightweight aggregate could be reflected by the uniformity index. Lastly, some problems in the formation of fresh concrete were analyzed and demonstrated, and the corresponding suggestions for practical engineering were also put forward.

Abstract:In order to better grasp the long-term behavior and evolution law of dam deformation, the multifractal theory was applied to the analysis of measured data of dam deformation under the premise of considering the correlation between displacement and environmental quantity. Taking the deformation analysis of a concrete gravity dam as an example, the multi-scale sliding time window was used to eliminate the pseudo fluctuation generated by the traditional multifractal sub interval division. The multifractal characteristics of the correlation between displacement and environmental quantity were characterized by the multifractal detrended cross-correlation analysis(MF-DCCA). Furthermore, the multifractal asymmetric detrended cross-correlation analysis(MF-A-DCCA)was used to further analyze the volatility, asymmetry and long-range correlation of the original displacement sequence, positive trend and negative trend. The multifractal characteristics of displacement under the influence of environmental factors were described from two aspects of overall fluctuation and local trend of displacement. From the analysis results, the deformation behavior of the dam is good and the multifractal characteristics of displacement are obviously affected by environmental factors. The change of reservoir water level is the main cause for the multifractal characteristics of the horizontal displacement.

Abstract:After the tunnel-shield-driving machine excavated through the north levee of Yangtze River, several transverse construction cracks appeared in the river embankment, and the accumulative settlement of the embankment was large. This paper considered the influence of the cracks in the embankment construction of different depths on the seepage and slope stability of the Yangtze River embankment. Based on the saturated-unsaturated seepage finite element method and the Sweden slice method, the seepage and slope stability analysis models of the embankment in the tunnel crossing section were established to calculate the seepage behavior and slope stability of the embankment under different crack depths, when the river level was the highest in history. The results show that the deep mixing pile has significantly reduced the water head and reinforced the slope of the embankment. The through cracks have great influence on the seepage field of the stratum around cracks. When the crack depth is less than 8. 5 m, the maximum seepage gradient of dam foundation and body is 0. 181 and 0. 206 respectively, which is less than the allowable seepage gradient of the corresponding soil layer. Therefore, the seepage stability of the embankment satisfies the requirement. Moreover, the influence of location and depth of through cracks on the slope stability of the embankment is obvious. When the crack depth is 8. 5 m, the safety factors of slope under two different positions of through cracks are 2. 419 and 1. 844 respectively after the reinforcement of deep mixing piles. The slope stability of the reinforced embankment with deep mixing piles can meet the standard requirements when the crack depth is less than 8. 5 m.

Abstract:The soil adsorption experiment is conducted to study the adsorption characteristics of bisphenol A(BPA)in different graded soils, and the relationships between soil particle characteristics, hydraulic characteristics and soil adsorption characteristics were analyzed. The experimental results showed that the adsorption of BPA in soils with different gradations was nonlinear adsorption and could be described by the Freundlich adsorption isotherm model. However, the adsorption of BPA by the soil with particle size less than 0. 075 mm was close to the linear adsorption and the nonlinear factor was 0. 979. The mass fraction of particles below 0. 01 mm is directly proportional to the adsorption capacity. The soil adsorption was inversely proportional to the permeability coefficient of soil and the adsorption of BPA on the soil tended to be constant as the permeability coefficient increased.

Abstract:To discuss the influence of the development degree of structural plane on the location selection of high-level radioactive waste repository, the rock mass of Suanjingzi area in Beishan, Gansu Province, was taken as the research object, and the statistical characteristics, such as the joint occurrence, density, spacing, trace length, fault occurrence, width of fault zone and thickness of fault gouge, were obtained through the mathematical statistics based on the geometric characteristic investigation of joints and faults in the superficial rock mass. Then, a multi-scale structural surface comprehensive evaluation index was proposed to evaluate the structural plane development in the superficial rock mass. The results showed that there were 4 and 5 dominant joint groups around BS22 and BS23 boreholes, and joints obeyed the normal distribution. The midpoint surface densities of joint traces around BS22 and BS23 boreholes were 0. 037 m^-2 and 0. 035 m^-2 respectively, and the average trace lengths were 20. 38 m and 17. 39 m respectively. The fault F1 was interpreted as 35°∠85°, with an extension length of 4. 49 km. The structural plane of rock mass around the BS22 drill hole was less developed and more suitable for the construction site of high-level radioactive waste repository than the BS22 borehole.

Abstract:In order to explore the influencing factors of shrinkage crack propagation of compacted clay, compacted soil samples with different dry densities and initial moisture contents were prepared for the experimental study. By simulating drought conditions, shrinkage cracks gradually appeared in the compacted soil samples. During the test, the digital image processing technology was used to conduct the quantitative statistics and analysis on the formed cracks, and the influencing factors of crack development speed were analyzed by the variable density function of crack parameters. The results show that the initial water content limits the crack occurrence speed, and the number of cracks and the maximum crack width decrease with the increase of dry density. The growth rate of crack width increases with the increase of water content, but the influence of dry density on the crack development rate is not obvious. At the same initial water content, the fractal dimension decreases with the increase of dry density.

Abstract:Detailed shape evolution during particle crushing was investigated using dyed gypsum particles. The particle shape information was measured from photographs with two orthogonal orientations and the Weibull function was introduced to quantify the statistical distribution of particle shapes. Then, the shape characteristics of particles under one-dimensional compression were investigated. It is found that child particles that have more size differences with parent particles are more rough, less spherical, more elongated, and flatter, with wider distribution range of shape factors. Surviving particles become more regular compared with parent particles and the distribution ranges of their shape factors tend to narrow down, whereas the broken particles show the opposite changing trends. However, all particles within a size range consist of both the surviving particles and the broken particles so that the overall particle shapes do not show consistent changing trends.