Because of special geography and climate environment, the water circulation mechanism in the source of Yangtze River has a distinct characteristic. According to the features of climate, precipitation, glaciers and permafrost in the source region of Yangtze River, the transfer mechanisms among water vapor, solid water and liquid water are analyzed. Results show that despite the lack of rainfall in the source region of Yangtze River, there are huge amounts of solid water storage. Its unique characteristics of water conversion mechanism have constructed a fragile ecological system in the Yangtze River source. Once the water cycle mechanism changes, the ecological environment will be significantly affected.
Mann-Kendall test, wavelet analysis and tendency item extraction from moving average series were utilized for the consistency analysis of annual mean tide level from 1956 to 2009 in Yangtze River estuary. Tianshenggang, Hupuzha(Zhaxia) and Wusong station were taken as case study. M-K test showed that there was an obvious rising tendency for the annual mean tide level at each station. MexHat wavelet function was utilized for the cycle analysis of annual mean tide level series, which showed that there were primary cycles of 17a, 16a and 16a in Tianshenggang, Hupuzha(Zhaxia) and Wusong station respectively. According to the tide level cycle, the moving average series of annual mean tide level at Tianshenggang, Hupuzha(Zhaxia) and Wusong station were calculated, and the tendency items were extracted to quantify the variation tendency of annual mean tide level series respectively. Furthermore, consistency correction was carried out on annual mean tide level series. The present research provided theoretical basis for the sustainable development of water resources in Yangtze River Estuary.
A new water pollution control system which intelligently integrates the water quality and water quantity monitoring and the discharge device is proposed to replace the traditional polluted water treatment in which the water quality and quantity monitoring and discharge device were segmented into different systems. It is effective to curb water pollution spread and transport. The technical difficulties of this new system is discussed in this paper. Statistical analysis based on relevance principle proves that there are some pollutants (named multi-related pollutant) whose quantities are respectively related to several pollutant quantities simultaneously. The pollutants which can be rapidly measured on-line are selected from the multi-related pollutants, and the measurement priority is divided into different levels according to the measuring speed. The method of seeking multi-related pollutants and classifying different priority levels are expounded in this paper. Factual engineering application shows that the new system not only enables the water area to actively choose water flow according to the water quality, but also sensitively refuses unqualified water flow and therefore the paroxysmal pollution could be avoided effectively.
The method of discharge computation for a single tide is generally adopted in the calculation of water diversion amount for tidal sluice. But the method requires long time and large work load. Especially for sluices with changing gates, the measwrement and calibration are burdensome. With Dingbo sluice in Wuxi City as a research case, the authors proposed a novel method of calculating the water diversion amount which is based on hydraulic formula to analyze the waterhead-flow relation. Result shows that the calculation accuracy meets the specification requirements. The method is convenient, feasible, and accurate for the statistics of water diversion along the river, and could provide data for the most stringent water resource management regime.
Spatial difference of soil erosion in Muyang river watershed was analyzed by SWAT hydrological model. The research was carried out based on the meteorological data from 1993 to 2009 and land use data in 2009 in Songhuaba water source area and Kunming city, and the second national general soil survey data as well as the observed data of runoff and sediment discharge in the small watershed. Results showed that the interannual peak and valley values of precipitation and sediment discharge were in good coherence. While within the year, the sediment discharge occurred mainly from June to September. The average soil erosion modulus varied from 21.4 t/(km2·a) to 4 586.5 t/(km2·a), indicating that the soil erosion is mainly between middle to moderate levels. The spatial variation of soil erosion is closely related with land use type and topography and slope angle. Interannual variations of soil erosion modulus and precipitation were also in consistency. The research provides basis for estimating the spatial distribution of soil erosion and making targeted conservation measures.
With the widespread long-term mid-layer intrusion density flow in the tributary bays of Three Gorges Reservoir as a research background, an indoor physical model was built. Three main factors inflow rate, initial water level, and temperature difference were chosen to design various conditions to simulate and investigate the motion characteristics of adverse slope density current in the mid-layer. The variations of hydraulic elements of the density current such as head moving velocity, interface height and head thickness influenced by inflow rate, initial water level, and temperature difference were analyzed. With Channing’s theoretical formulas, the head velocities of mid-layer density current in different conditions were calculated and compared with the measured values. It was found that the difference between the two was not large, and the relative error was less than 5%.
I-type horseshoe cross-section with flat-bottom is simplified from standard I-type horseshoe cross-section. since the shape and size are easy to control,#em/em# is composed of a flat-bottom and three arc sections. It is commonly applied in hydroelectric engineering. But the critical water depth computation formula is a transcendental equation and has no analytic solution. Mathematics transformation for the critical flow equation was carried out, and the relationship between the dimensionless critical water depth and the relative dimensionless parameters was analyzed. Furthermore, an approximate formula for the calculation of critical water depth for I-type horseshoe cross-section with flat-bottom tunnel was obtained according to the fitting principle. This method overcomes the defects of other iterative trial calculating methods, such as calculation step, dependence on special charts and curves, and serious error. The formula is simple and the maximum error is less than 0.4% under the general engineering design condition (0<h/r≤1.447 1,h/r is the ratio of critical depth to the radius of arch roof). It can be used for engineering design practice and for the compilation of hydraulic structure design handbooks.
To provide reference for a highway tunnel construction, unloading confining pressure tests are carried out on standard siltstone samples with constant axial deformation by using MTS815.04 electro-hydraulic servo-controlled rigid testing system. Results show that there are three stages during the whole test process initial stage, crack growth stage, and failure stage. In the failure stage, the major cracks propagate along the direction of the maximum principal stress, and eventually a tension failure plane which is approximately parallel to the maximum principal stress is formed. The variation curve of axial pressure vs. confining pressure σ3 during the unloading process is analyzed. It can be found that the rock is more vulnerable to unloading destruction compared with loading destruction, because when the confining pressure is reduced to a certain degree, the cracks spread rapidly due to the tensile stress, and the friction between the expanded cracks disappears at the same time. The mechanical parameters of the siltstone samples under unloading are obtained, among which the elastic modulus and Poisson’s ratio μ show a non-linear change with the volumetric strain εv.
Soft rock is easily disintegrated and softened in the presence of water. Taking the soft rock of a dam foundation in middle Jinsha river as a research object, we selected 8 typical rock samples (argillaceous siltstone) from the dam foundation in the right bank and cut each sample into 3 parts to carry out dry uniaxial compressive test, indoor dry-wet cycle disintegration test, and outdoor natural disintegration test respectively on each part. By recording the initial disintegration time and describing the whole disintegration process, we quantitatively divided the disintegration into three levels completely disintegrated, moderately disintegrated, and not disintegrated. Moreover, we compared the final state of disintegration of the rock samples under dry-wet cycling condition and natural condition. Subsequently, we measured the viscous granule content in the rock samples after wet disintegration. Test results showed that rock samples in dry-wet cycling condition disintegrated more thoroughly than those in natural conditions. The initial time and final state of disintegration are well correlated with the dry uniaxial compressive strength and viscous granule content.
Three-dimensional method is needed in the stability analysis for slope projects with complex spatial geometric features and geological structures. A computer program CORE-lam3D for 3-D slope stability analysis was improved and developed. The program can simulate complex space surface such as real slope, geologic boundary, groundwater level and slip surface. Potential sliding surfaces and sliding directions can be calculated with three 3-D limit equilibrium analysis methods, and the impacts of water load, seismic load and anchoring forces were analyzed. The analysis results of a tension-distorted body on the right bank of the reservoir at Pubugou hydropower station verified the efficiency and applicability of the improved CORE-lam3D program.
In consideration of multiple wave reflections, frequency domain analysis method was adopted to solve one-dimensional wave propagation in layered jointed rock. Firstly, the overall transfer matrix of one-dimensional wave propagation along multiple parallel joints was constructed by using wave theory and linear displacement discontinuity model. Solution for one-dimensional wave propagation in frequency domain can be obtained with boundary conditions. Subsequently, discrete Fourier transform and inverse discrete Fourier transform were used to transform the solution from frequency domain to time domain. Finally, SV wave propagation through joints of different spaces and numbers was studied by the above methods, and the simulation result was compared with that from discrete element program UDEC. The results showed that the transmission coefficient |TN| (ratio of transmitted wave amplitude to incident wave amplitude) rose first, then declined, and finally became stable with the increasing of joint spacing. During the rising stage of TN, it has less dependence on the number of joints. Through comparison with UDEC results, the method in this paper was found to be feasible.
This research is carried out to improve the expansive soil subgrade of the first-class highway from Xiaoxita to Yaqueling in Yichang city. Different amounts of weathered sand were mixed in expansive soil samples to investigate the expansive soil’s free swelling ratio, unloaded swelling ratio, loaded swelling ratio (25kPa and 50kPa) and expansion force. Through heavy compaction test and comparison of swelling rates, it’s found that adding weathered sand changes the water content and compaction of expansive soil, and hence restrains the expansion. The free swelling ratio of expansive soil mixed with weathered sand is less than 35%, which meets the requirement of subgrade construction. Different ratio of mixed sand to soil has different effect on the expansion when the mix ratio is 10%, the free swelling ratio and expansion force decrease most remarkably; when the ratio is 40%-50%, the swelling rate under 25kPa loading changes most evidently; when the ratio is 30%-40%, the swelling rate under 50kPa changes by a biggest margin; when the ratio is 40%, the increase of load can well control the expansion. The amount of weathered sand has slight influence on unloaded swelling ratio. It’s concluded that the expansion of expansive soil mixed with 10% weathered sand could be restrained most rapidly and economically.
Wendeng pumped-storage power station is composed of water intake system, underground powerhouse system, tailrace system and the upper and lower reservoir. The underground chambers, seepage control system of the upper and lower dam, and the adits and densely distributed drainage holes above the penstock construct the complex impervious system of the station. GWSS(Groundwater Simulation System) software was adopted in the numerical simulation analysis on the complex seepage field of the project. Characteristics of the complex seepage field, the external water pressure of conduit pipe and the impervious effect of the upper dam during normal operation were investigated. The result shows that the pressure on the conduit pipe and branch pipe can be reduced obviously and hence the seepage control effect meets the requirement by setting plughole and drainage curtain at the top of the horizontal segment of the high-pressure tunnel.
Since thick silty soil distributes widely along the Zhengzhou-Wuhan Passenger Railway, the post-construction settlements should be controlled strictly. The key to embankment filling are regarded as the control over filling speed based on the settlement observation data to assure the stability of embankment; the prediction of post-construction settlements to determine the period of ballastless track construction; and the control over settlements after construction to the allowable limit. The reliability and pre-processing of settlement data, and the method of discriminating abnormal settlement data arepresented in this paper. The characteristics and applicability of settlement prediction models are discussed. The LSSVM (least squares support vector machine) is used in the pre-processing of settlement data. Hence a systematic prediction model for silty soil is established. The detailed prediction process is expounded by giving examples, and the prediction results show that the settlement tends to be stable; no large post-construction settlement would occur during the operation period, which suggest that the foundation treatment and construction method is successful.
To precisely reflect the anti-sliding stability of dam, a visualized software module was researched and developed to assess the deep-seated sliding stability of concrete gravity dam. Firstly, the stress distribution on the deep-seated sliding plane of the dam was numerically calculated. On this basis, by using the design method of the limit state of partial coefficient, the formula of shear strength was applied to each FEM element to define a new formula for the safety coefficient, thus an improved method of partial coefficient for the stability assessment was developed. In subsequence, the method was programmed by programming tool Delphi in association with AutoCAD. Since the advantage of FEM in calculating stress filed and considering dam foundation and body deformation is reflected in the method and the software module, and owing to the reliability degree taken into account as well, the obtained safety coefficient could well reflect the anti-sliding stability. Moreover, Ks expression in design specification is employed to make the method easy to use and popularize.
The present research is to explore the seismic response features of the cutoff wall in dam foundation with deep overburden and to evaluate its seismic safety. Jinping rockfill dam was taken a case study. On the basis of 3-dimensional nonlinear static analysis, submodeling method was used to carry out time-history analysis on the foundation’s cutoff wall. The filling materials of dam and the alluvium deposit were simulated by Hardin-Drnevich dynamic constitutive model. The thin-layer contact element was used to simulate the contact relationship between the cutoff wall and the overburden. Results indicated that dynamic stresses showed a strong response in the upper part of the cutoff wall near the bank sides. After superposing the dynamic response with static response, the deformation and stress distribution rules changed slightly compared with those in the static state. Influenced by the terrain of deep and narrow valley and the turning point of the right bank, the vertical compressive stress extremum occurred in the turning point of the right bank of the mid-upper part of the wall instead of the mid-lower part as general rule shows. During the seismic history, the rupture area of the cutoff wall extended little, and the growth rate of vertical compressive stress extremum was only 3.5%. In conclusion, the influence of seismic load on the work condition of cutoff wall was not obvious.
A digital construction management system which integrates computer technology, GIS technology, database technology, and wireless sensor network technology is introduced, and its application to the Dagangshan Hydropower Station is described. Functions inclusive of 3-D visual simulation, construction grouting, concrete temperature control and safe blasting monitoring are elaborated in detail. With this system, a data collection mode which fits the dam construction characteristics is established. Moreover, 3-D visual query, query and analysis of concrete temperature control, as well as process control and quality management for foundation treatment works are also accomplished. Digital system could realize the management and sharing of centralized data, enhance the standardization, refinement and personalization of the construction site, and provide technical support for the decision-making of hydropower construction.
