Abstract:Aiming at the non-probabilistic characteristics of the factors influencing dam service reliability, a non-probabilistic Info-gap model is established to quantifiably describe the non-probabilistic uncertainty of the influence factors. A non-probabilistic reliability analytical method of dam service performance is proposed based on two non-probabilistic reliability measures, Info-gap decision theory and the volume ratio. Non-probabilistic target reliability indexes of dam service performance are then preliminarily determined. The proposed non-probabilistic method is used to analyze the structural service reliability of a dam. The results of the reliability analysis in various function modes demontrste the engineering applicability of the method and the varified rationality of the determined non-probabilistic target reliability as well.

Abstract:Reinforcement of dangerous reservoirs is a huge project in China, but the theories and methods of comprehensive assessment for the reinforcement effects are limited, leading to the difficulty to accurately evaluate the actual effects for a large number of reinforcement projects. The quantitative analysis of the evaluation method of the reinforcement effect for dangerous reservoirs is studied. Four reinforcement impact factors are defined, including the evaluation of reinforcing schemes, functional index rehabilitation, engineering construction and the benefit of reinforcement, based on which a “Building Block Model” of the influence factors is established to evaluate reservoir reinforcement effect. Quantification methods for the reinforcement effect evaluation indexes are proposed, including the evaluation indicator grading, time-dependent and time-independent evaluation indexes, subjective and objective weight of experts, static and dynamic weight. The quantitative evaluation model for evaluating the reinforcement effect of dangerous reservoirs is obtained. The model is applied to the reinforcement assessment of a dangerous reservoir and the results agree well with the actual situation and the acceptance conclusion.

Abstract:Taking the Lijiaxia Dam as an example, 4 typical phenomena of high concrete arch dams during long term operation are summarized and analyzed, including the large deformation of dam foundation, the asymmetric deformation at the left and right 1/4 part of the arch, uplift pressure anomaly at the elevation of 2087 at the left and right part of the dam, and the high ground temperature. The behavior of the Lijiaxia Dam was estimated by using high water level prototype test, forward and back analysis, FEM analysis of the observed data with the help of regularity analysis, correlation analysis, generalization and summarization. The results show that the variation of the horizontal displacement of the Lijiaxia Dam is normal as a whole with good operation conditions and the design demonstration and evaluation is normal. After treatment of the dam foundation, it satisfies the safety requirements with sufficient overload safety.

Abstract:In order to reflect the characteristics of foundation settlement after dynamic compaction, the relationship between the contact force and foundation settlement is established based on the principle of work and power. According to the principle of static equivalence and the calculation principle of layered settlement of foundation, the formula of contact force and settlement of dynamic compaction is deduced. The formula is simple and can calculate the settlement of layered soil after compaction. The calculation results show that the calculated value of foundation settlement is close to the field measured one, indicating a good verification for the applicability of the proposed formula. The calculated value of settlement and deformation modulus of each layered soil foundation after compaction is in accordance with the engineering practice, which reflects the strengthening characteristics of the dynamic compaction method.

Abstract:At present, the analysis of structure safety status of concrete dams using the monitoring data under strong earthquake is greatly influenced by calculation models and parameters. Based on the time series of the monitoring data under strong earthquake, the time-varying autoregressive recursive ARX model is established. The post-earthquake rapid evaluation method of concrete dams is then proposed based on the property that the ARX model parameters can reflect the dynamic variation of the structure system, and the efficiency of the model is improved by using the self-regulated forgetting factor. The simulation results for an example show that the time-varying parameters of ARX model can reflect the structure state variation of concrete dams, indicating that the proposed method is effective and feasibility and it can be a supplementary method to the Technical Specification of Strong Motion Monitoring for Seismic Safety of Hydraulic Structures(DL/T 5416-2009).

Abstract:Based on the achievements of Sino-Swiss Cooperation Project on Dam Safety Enhancement, the safety regulations and safety management modes of dams in Switzerland were summarized briefly, and the corresponding safety monitoring and controlling mechanisms of the dams were deeply analyzed in this paper. The safety management mechanism and safety monitoring system of the reservoirs and dams in China were also summarized and analyzed. Based on the results, the similarities and differences of the dam safety monitoring mechanisms between the two countries were compared and analyzed. A clear, practical and effective dam safety monitoring mechanism has been formed in Switzerland. The dam safety monitoring mechanism established in China is similar to that in Switzerland, but it is insufficient and the awareness of active monitoring is not strong enough, resulting in a quite different actual result. Therefore, China can learn from the mature modes of dam safety monitoring in Switzerland and enhance the awareness of active safety monitoring. Meanwhile, the safety monitoring system based on the concept of risk management should be set up, and advanced technologies such as the Internet of Things are suggested to be introduced to improve the safety monitoring level for small reservoirs with the characteristics of great numbers and various functions.

Abstract:Reinforcement recovery and reinforcement is an important work and long-term task in the field of hydraulic structure, which are of significance to ensure the safety service of the project, to develop the project benefit, and to extend the service period of the project. The cost calculation and decision making model of hydraulic structure maintenance and reinforcement and its algorithm are established under the premise of ensuring structure safety and reliability, with the consideration of the deterioration characteristics of structural performance and the introduction of life cycle cost theory from the objective of optimizing the whole life cycle cost in engineering. The proposed method is applied to a hydraulic structure, and the concrete maintenance plans during the whole life cycle are calculated and formulated. The result shows that the models and methods in this paper can provide some scientific basis for the maintenance and reinforcement strategies of hydraulic structures in the whole life cycle.

Abstract:To solve the shortage of useful materials in Baihetan Hydropower Station aggregate storage, taking the site geological conditions, excavation features and time, construction conditions, and economy into consideration, three supplementary mining scheduling programs are designed and optimized based on the re-examined results of the storage. With the help of linear weighted sum(LWS)method, the proposed three mining plans are analyzed for comparison based on four evaluation indexes, including the reserved useful materials, excavation time, construction conditions, and economy. The result shows that the third exploitation plan is the best that can increase 3. 8 million cubic meters of useful materials after excavating. It ensures the supply of aggregate content for the dam concrete program and guarantees the construction of Baihetan Hydropower Station.

Abstract:A series of laboratory pullout tests on the sensing optical fiber embedded in expansive soil were performed to study the impacts of three factors on soil-fiber interfacial mechanical properties, including dry density of soil, water content and overburden pressure. It is found that the displacement-pullout force curves under different test conditions have the similar rules. The pullout force increaces linearly with the pullout displacement to the maximum value, then decreases gradually and finally tends to the residual value. The optical-soil interfacial mechanical characteristics are analyzed based on a tri-linear pullout model. The shear strength of fiber soil interface is positively correlated with soil dry density and soil overburden pressure but is negatively related to soil moisture content. The study results will provide references for the further application of fiber optic sensing to expansive soil deformation monitoring in geotechnical engineering.

Abstract:The triaxial test of discrete elements in rockfill material has the problem of excessive influence factors and time-consuming for mesoscopic parameter calibration. On the basis of summarizing and analysing the current rockfill mesoscopic models, a mesoscopic parameter calibration model based on the quantum genetic algorithm(QGA)and support vector machine(SVM)was established. The Latin hypercube sampling was used to generate the mesoscopic parameter groups, and then the stress-strain curves were calculated by the discrete element method. In order to simulate the complex nonlinear relationship between the mesoscopic parameters and the stress-strain curves, the QGA was used to train SVM to achieve the best learning effect. According to the indoor triaxial test results and taking advantage of the speed of SVM, the mesoscopic parameters of rockfill were calibrated by the QGA searching process. The calibration example of rockfill shows that QGA-SVM can quickly and accurately calibrate the mesoscopic parameters of the discrete elements, indicating a good application value in practical engineering.

Abstract:Strain transfer relationship between surface-bonded plastic optical fibers(POFs)and concrete under different layouts is analyzed, based on which a strain transfer model between surface-bonded POFs and concrete is constructed. Numerical simulation is carried out to verify the correctness of the model and sensitivity analysis of the main parameters in the model is studied. The results show that, the width, thickness and shape of the adhesive layer have little effect on the strain transfer. In favor of the effect of strain transfer, it is suggested that the elastic modulus of the solidified glue is about 1GPa and the POF is bonded close to the surface of the concrete with the bonding length greater than 300mm.

Abstract:To investigate the internal self-drying effects of hydraulic concrete and high-performance concrete with different water-cement ratios, the ratios are set to be 0. 33, 0. 41, 0. 51 for hydraulic concrete and 0. 30, 0. 40, 0. 50 for high-performance concrete. The concrete specimens were sealed and the internal relatively humidity inside was monitored for three months. The test results show that the internal relative humidity for both hydraulic and high-performance concrete in the sealed state has two periods, namely the humidity saturation period and the humidity drop period. As the water-cement ratio decreases, the duration of the humidity saturation period gradually decreases. The drop rate of the relative humidity for high-performance concrete is higher than that for hydraulic concrete with the same water-cement ratio, and the duration of humidity saturation period for the former is shorter. The internal relative humidity of hydraulic concrete with the water-cement ratio 0. 5 in the sealed state does not drop substantially but with the water-cement ratio 0. 41, it drops slowly due to the self-drying effect. When the concrete dries gradually, it shrinks slowly, which provides a new idea to analyze the long-term instability mechanism for the strain with the deduction of temperature strain, called the no-stress-gauge strain in the Xiluodu ultra-high dam project.

Abstract:According to the abnormal data partitioning of the statistic diagnosis and the causes of the error data in dam monitoring, the abnormal data observed can be categorized into random error, gross error, system error. The influential data is distinguished and then the processing methods for different errors are studied using the mean shift model, including the t-test method for the gross error detection based on the model disturbed values and the Cook-distance-test method for the influential data based on the influence of the model disturbance on the model fitting parameters. Taking typical original monitoring data of dam displacement as an example, rationality test was performed using the proposed statistical diagnosis methods. The results indicate that these methods can effectively distinguish gross errors and influential data, with which the accuracy of further model analysis can be significantly improved.

Abstract:This paper introduces the safety service system of hydropower projects during operation stage in the perspective of the 3A hospitals. The definition, basic constitution and the main features of the 3A hospital in hydropower projects are discussed. The application and research of the key technologies during the health monitoring and evaluation for hydropower projects are stated. The basic framework of professional qualification rating and grading is also discussed. It is believed that the theory and method of the whole industrial chain and life cycle service in hydropower projects can be better established and improved in the perspective of 3A hospitals.

Abstract:To ensure the safety of the water conveyance tunnels in the operation period, effective dynamic monitoring indexes should be established according to the engineering characteristics. Based on the analysis of the monitoring methods and the influence factors of operation security, a safety monitoring model of water conveyance tunnel is established. The proposed model considers the influence factors such as internal and external water pressure, temperature, deformation of lining concrete and surrounding rock. The monitoring indexes are determined by the confidence interval method. The long-period monitoring data are segmented and analyzed, and the moving average filtering algorithm is introduced to determine the dynamic monitoring indexes for water conveyance tunnels. The calculation result of an engineering example shows that the dynamic monitoring indexes at measuring points can be determined by the proposed method.

Abstract:Based on the current state of construction and safety of earth-rockfill dams in China, in this paper, the theories, methods and technology of long term service and risk assessment of earth-rockfill dams are discussed from the aspects of internal erosion mechanisms, monitoring and diagnosis technology of hidden defects, service performance of the seepage control system, risk analysis and decommissioning demolition. It is concluded that in the future, further study should be focused on the defect detection of dams under deep water environment, the rapid detection technology of hidden danger, multi-source information fusion inference technology of long service state for earth-rockfill dams, the decision-making technology of dam decommissioning and the evolution mechanism of secondary derivative events in the impact zone of dam break. A mature earth-rockfill dam safety and risk control system in the project full life cycle should be developed to establish systematic theories and methods of protection and promotion for long-term service performance of earth-rockfill dams.