Abstract:Based on the agricultural trade volume between China and the countries along the Belt and Road from 2001 to 2020, the virtual water volume was measured by combining the water footprint of the products with the existing research results, and the formula of water stress index was constructed to quantify the water resources and agricultural water stress of the countries along the Belt and Road. The spatial and temporal evolution characteristics of virtual water trade and its mechanism were analyzed, and the pressure of agricultural water shortage arising from the trade was discussed. The results show that changes in China ’s import and export virtual water resources were related to its national conditions and international events. The trend of importing virtual water resources was increasing, with more than 90% coming from Southeast Asia, South Asia, Central and Eastern Europe, Mongolia and Russia, with green water accounting for about 80%. The trend of export virtual water resources was stable, with more than 80% exporting to Southeast Asia, West Asia and the Middle East, Mongolia and Russia, with green water accounting for about 70%. More than 1/3 of the countries along the Belt and Road are facing high and heavy water resources pressure, and more than 1/2 of the countries are facing high agricultural water pressure. Nearly 2/3 of the countries have reduced the pressure of agricultural water scarcity by importing virtual water resources from China. Nearly 1/3 of the countries have increased the pressure of agricultural water shortages by exporting virtual water resources to China.

Abstract:Based on the five criteria of hydrological integrity, chemical integrity, morphological structure integrity, biological integrity and social service function, the river health assessment index system for the Gansu section of the Weihe River Basin was constructed. The combined weighting method based on the improved analytic hierarchy process and the Critic method, and the fuzzy matter-element extension model were used to calculate the assessment grade of the river health. The river health in the Gansu section of the Weihe River Basin was evaluated and the prominent problems of water health of the Weihe River were analyzed with the obstacle diagnosis model. The results show that from 2017 to 2019, the health levels of the main stream of the Gansu section of the Weihe River Basin were in a sub-health state but with a slight improvement trend. The chemical integrity of the five criteria layers was the worst, indicating that the watershed management should pay more attention to the river water quality management. The indicators for assessing the sensitivity of river sections are related to the hydrological, chemical and biological integrity, and are the most effective sensitive factors to improve the river health level.

Abstract:Based on TM/Landsat8 OLI image data and land use data, the ecological environment quality index and distribution index were used to analyze the production-living-ecological space land use and eco-environment effect in Qianzhong Water Conservancy Hub Project area from 2000 to 2020. The response characteristics of land use change and ecological environment effect to topography and landform were also analyzed. The results show that from 2000 to 2020, the land use in the area has the overall characteristics that the ecological land is the most, followed by production land and living land. The area of ecological land first decreases and then increases. The area of production land has a decrease-increase-decrease trend while the area of living land shows a trend of continuous increase. The conversion among grassland ecological land, forest ecological land and agricultural production land is higher than other types of conversion, and the grassland ecological land area has the highest conversion. The ecological environment quality is fluctuated in the project area. The ecological environment quality in the eastern and western parts of the project area is generally better than that in the central part of the project area. The ecological environment quality in the areas with elevation greater than 1 700 m and slope greater than 15° and the eastern and southern slopes is better, while the ecological environment quality in the low altitude areas is gradually improving. The eco-environmental quality of non-karst and pure karst areas is better than that of sub-karst areas, but the eco-environmental quality of non-karst and pure karst areas shows a declining trend.

Abstract:Based on long series of measured tidal data and the harmonic analysis method, the long-period variation of the measured tide and astronomical tide downstream of the starting point of tidal bore in Hangzhou Bay were analyzed, and then the influence of astronomical tidal changes on the tidal bore in the Qiantang River was analyzed. The results show that the measured tidal range, tidal arrival time and flood tidal duration of the Zhapu station at the same day and the same tide on 3rd and 18th in lunar August each year vary greatly, with the maximum amplitudes of 1.95 m, 102 min and 122 min, respectively. The maximum variation of tidal range, tidal arrival time and duration of high tide on the same day and the same tide on the 3rd and 18th in lunar August each year at the Zhapu station are 1.52 m, 93 min and 46 min, respectively. The variation of astronomical tide has great influence on the tidal bore. The maximum difference of tidal bore height, arrival time, velocity and steepness of tidal bore at the Yanguan station on the same day and the same tide are 1.12 m, 93 min, 2.05 m/s and 18.1%, respectively.

Abstract:In order to analyze the subglacial flow structure and circulation distribution characteristics in a river bend, the flow field in the Shisifenzi bend was measured using acoustic Doppler current profiler (ADCP). By measuring the ice thickness, water depth and velocity of the bend, the ice condition and the distribution of the subglacial circulation in the bend section were analyzed. The results show that the flow under the ice in the bend does not completely present a double helix structure. During the freezing period, the circulation is concentrated on the concave side of the bend top and the convex side of the bend top, which is easy to occur between adjacent ice jams or between ice jams and river banks. The circulation curl in the circumfluence region increases linearly along the water depth, while the circulation curl in the non-circulation region decreases linearly. The distribution of circulation curl in different flow layers at the same position is basically the same. The circulation curl in the second half of the bend is larger than the first half and its value in the concave bank side is larger than the convex bank side, with the maximum circulation curl value of about 0.91 located in the concave bank side of the bend.

Abstract:To perform scientific and rational evaluation on landslide dam stability, essential information was undertaken from 313 collapsed and intact landslide dams worldwide to establish a case database. Eight influential factors related to the morphological characteristics and material composition of landslide dams, hydrodynamic conditions of barrier lakes were considered. Based on the analysis of Bayesian networks, two novel and expedited methods for assessing landslide dam stability were introduced, including a simplified model with missing nodes and a detailed model with intact nodes. The comparison between typical models of rapid evaluation method of landslide dam stability from both home and aboard shows that the simplified Bayesian network model can achieve an absolute accuracy rate of 83.33% and a conservative accuracy rate of 94.44%. Similarly, the detailed model demonstrates absolute and conservative accuracy rates of 80.77% and 96.15%, respectively. The reliability and scientificity of the Bayesian network model are verified. The Bayesian network models can incorporate and update real-time sample sets, and thereby the predictive accuracy of the models can be increased perpetually.

Abstract:In order to explore the complex non-linear relationship between concrete dam deformation monitoring data and various influencing factors, and to improve the deformation prediction accuracy of ultra-high arch dams, based on the twin support vector machine (TWSVM) model and the adaptive particle swarm optimization (APSO) method for parameter optimization, an APSO-TWSVM prediction model for the deformation of a very high arch dam was constructed by introducing position and velocity factors. Case analysis shows that the model can effectively explore the complex non-linear relationship between the deformation of arch dams and the influencing factors, and compared with the traditional SVM method, the model speed and accuracy have been significantly improved.

Abstract:To analyze the effects of ecotypic stabilizer on soil reinforcement of plant roots, direct shear tests were conducted on the root-ecotypic stabilizer-clay complex, and the shear strength parameters, shear modulus and total deformation energy of the complex under different root numbers and different ecotypic stabilizer contents were studied. Combined with the shear displacement generated by the samples, the shear characteristics and reinforcement mechanism of vegetation soil reinforcement were explored. The results show that the shear strength is increased by plant roots. When the content of the ecotypic stabilizer is greater than 1%, its influence on the complex deformation resistance is more obvious. The ecotype stabilizer forms a network structure in soil, which can promote the formation of cohesive soil aggregation, enhance the cohesion, and interact with the plant roots to improve the shear strength of the soil.

Abstract:In order to enhance the anti-crack and anti-scour property of cohesive clay, a series of evaporation, dry shrinkage cracking and anti-scour tests were carried out on xanthan gum composite cohesive clay mixed with sand of different contents. By measuring the moisture content of the sample and anti-scour coefficient of the soil, and quantitatively analyzing the development of surface crack of the soil with graphic analysis software, the internal water change law, anti-crack and anti-scour performance of the composite cohesive soil were studied. The results show that, with the addition of sand particles, the crack rate, crack width and scour damage degree of cohesive clay samples increase first and then decrease. When the sand content is 30%, the crack rate, crack width and scour damage degree of cohesive clay samples with or without xanthan gum are higher than those of other sand contents. When the sand content is about 50%, the xanthan gum colloid forms a stable structure with a certain strength with sand particles for xanthan gum composite silty clay, and its anti-scour performance is significantly improved.

Abstract:Taking the mud as non-Newtonian fluid, the leakage of the cofferdam in different positions for emergency repair of buried pipeline in mud flat was studied using ANSYS Fluent software. The influence of non-Newtonian consistency coefficient, power law index, and gap size on leakage was discussed, and the hourly rise of mud in the cofferdam was calculated. The results indicate that when the power law index is less than 1, shear thinning occurs, and the apparent viscosity of mud decreases with the increase in shear strain rate. With the increase in power law index, the leakage increases gradually, indicating that the apparent viscosity decreases with the increase in power law index. Moreover, when the power law index is greater than 1, the leakage increases further, indicating that the shear strain rate is less than 1 during flow process. The leakage of the cofferdam decreases gradually with the increase in consistency coefficient, but increases significantly with the increase in gap size. When the power law index is in the range of 0.3 to 0.5, the consistency coefficient is in the range of 3 to 9.kPa·s, and the gap size is in the range of 5 to 10 mm, the total height of the mud rising inside the cofferdam has little effect on the construction inside the cofferdam.

Abstract:The measured topographic data from 2014 to 2019 were used to quantitatively analyze the morphological adjustment of the shoals around the Qingcaosha Reservoir. The effects of corresponding protection measures for the shoals were explored based on the numerical model MIKE21. The results show that the outer beaches around the Qingcaosha Reservoir stopped sedimentation, and some parts of the beaches shrank after 2014. The head of shoals had been significantly scoured in the middle part of the north dikes, and the maximum scouring distance was nearly 900 m (-5 m and -10 m depth contours). The shoals’ shape was flattened, which must be protected in time. The ebb tide mainstream at the inlet and outlet of the Xinqiao channel deflected to the reservoir dikes, which affected the scouring evolution process of the shoals. After the implementation of submerged bank protection at the head of the Qingcaosha Reservoir, the velocity decreased significantly in shoal area outside the middle part of the north dikes, and the protection measures had little impact on the surrounding hydrodynamic processes.

Abstract:Taking the side inlet/outlet of an upper reservoir without adjustment section as the research object, the Reynolds stress model was used to explore the influence of diffusion section length on the hydraulic characteristics of the inlet/outlet, and the recommended value of diffusion section length was given from the perspective of hydraulics. The results show that the length of the diffusion section has a significant influence on the water flow movement of the side inlet/outlet, and the diffusion section should not be too long or too short. The flow velocity distribution along the inlet/outlet can only be affected by the length of the diffusion section under the pumping condition, and there is basically no influence under the power generation condition. For other hydraulic indicators such as head loss and flow distribution at each orifice, the length of the diffusion section will have a greater impact on it when the flow is in both directions, and with the increase of the length of the diffusion section, the hydraulic indicators will first become better and then worse. For the body type of side inlet/outlet without adjustment section, when the length of the diffusion section is 5.7 to 6.0 times the tunnel diameter, the hydraulic indicators meet the requirements of the specification. When the length of the diffusion section is 5.8 times the tunnel diameter, the hydraulic characteristics of the inlet/outlet are greatly improved, and the water flow pattern is better.

Abstract:To improve the accuracy of acoustic emission source locating for concrete panel damage in rockfill dams, a combined acoustic emission source locating method based on wave velocity correction, BSO-IGeiger method, is proposed. Wave velocity correction is used to improve the known constant wave velocity time difference method (Geiger method) and a localization objective function is established. The localization objective function is solved using the learning elimination mechanism-based beetle herd search algorithm (BSO). At the same time, a sensor array health monitoring network layout method is developed for area localization and sensor survival detection to ensure the reliability of the sound source localization of the rockfill dam panel. The experimental verification results show that the locating effect of BSO-IGeiger method is significantly better than that of Geiger method and the unknown constant wave velocity time difference method.

Abstract:In order to analyze the multi-point data of high arch dams more efficiently, the kernel principal component analysis (KPCA) method for error reconstruction was introduced to identify the outliers in the multi-point sequence. To solve the problem of poor performance of the clustering by fast search and find of density peaks (CFSFDP) algorithm in high dimension, the KPCA method was used to reduce the dimension, and an improved CFSFDP (ICFSFDP) algorithm was proposed for automatic selection of cluster center and truncation distance. Based on KPCA-ICFSFDP method and the multiple output Gaussian process (MOGP) method, a multi-point deformation MOGP model was built according to the partition. The results show that for the small number of partitions within the cluster points, compared with the MOGP model without partition, the prediction effect is improved. Meanwhile, for the measurement points with good performance of the overall MOGP model, the prediction accuracy remains high after partitioning, which is improved compared with the single-output Gaussian process model.

Abstract:Based on the Caochi landslide mass in the upstream of the Qingyukou Reservoir, the finite difference method for parameter optimization design of anti-slide piles with pre-stressed anchor cable was used to analyze the deformation and force distribution of the landslide under different states. The results show that the pile position has a great influence on the stability of the landslide mass, and the safety factor of the landslide stability increases and then decreases with the distance between the pile position and the slope toe. Under the same pile position, there exists a critical length of the anchorage section of the anti-sliding pile, which is 30 m. The influence of the pile spacing on the stability of landslide mass is greater than the section size of anti-slide pile. In the range of 26° to 35°, the angle of anchor cable has little effect on the landslide stability. Through comprehensive analysis, it is suggested that the section size, pile spacing and anchor cable angle of the anti-slide pile should be 2.5 m×3.5 m, 7 m and 27°, respectively.

Abstract:In order to analyze the safety change of an aqueduct in service,the time-discretization method was introduced into the time-varying reliability calculation of the aqueduct structure. Based on a project case, the bearing capacity and crack resistance limit state equation of the rectangular adueduct body were established for three parts in the transverse and longitudinal direction,and the time-varying reliability was calculated. Its accuracy was verified by comparing the calculation results of Monte Carlo method, and compared with the calculation results of dynamic reliability method. The results show that the reliability of the longitudinal bearing capacity of the aqueduct structure decreases with the service life, especially in the later stage of service the decline is much greater than the transverse bearing capacity, indicating that the limit state of the longitudinal bearing capacity is the control state of the aqueduct life. Both the longitudinal and transverse crack resistance reliability decline is slower compared with the bearing capacity reliability. The crack resistance reliability of the bottom plate is slightly lower than the target value in the later stage of service due to the low initial value. The overall calculation error of the time-discretization method is relatively small, especially for the safety evaluation of the structure in the later stage of service. Compared with the dynamic reliability method, the calculation result of the time-discretization method is more accurate. It is more reasonable to use the time-discretization method for the reliability calculation and safety evaluation for aqueducts.